Header Protection for S/MIME
draft-ietf-lamps-header-protection-09
The information below is for an old version of the document.
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| Authors | Daniel Kahn Gillmor , Bernie Hoeneisen , Alexey Melnikov | ||
| Last updated | 2022-11-22 | ||
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draft-ietf-lamps-header-protection-09
LAMPS Working Group D. K. Gillmor
Internet-Draft American Civil Liberties Union
Intended status: Standards Track B. Hoeneisen
Expires: 26 May 2023 pEp Foundation
A. Melnikov
Isode Ltd
22 November 2022
Header Protection for S/MIME
draft-ietf-lamps-header-protection-09
Abstract
S/MIME version 3.1 introduced a mechanism to provide end-to-end
cryptographic protection of e-mail message headers. However, few
implementations generate messages using this mechanism, and several
legacy implementations have revealed rendering or security issues
when handling such a message.
This document updates the S/MIME specification to offer a different
mechanism that provides the same cryptographic protections but with
fewer downsides when handled by legacy clients. Furthermore, it
offers more explicit guidance for clients when generating or handling
e-mail messages with cryptographic protection of message headers.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://dkg.gitlab.io/lamps-header-protection/. Status information
for this document may be found at https://datatracker.ietf.org/doc/
draft-ietf-lamps-header-protection/.
Discussion of this document takes place on the LAMPS Working Group
mailing list (mailto:spasm@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/spasm/.
Source for this draft and an issue tracker can be found at
https://gitlab.com/dkg/lamps-header-protection.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 26 May 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Two Schemes of Header Protection . . . . . . . . . . . . 6
1.2. Problems with Wrapped Messages . . . . . . . . . . . . . 7
1.3. Problems with Injected Headers . . . . . . . . . . . . . 7
1.4. Motivation . . . . . . . . . . . . . . . . . . . . . . . 7
1.4.1. Backward Compatibility . . . . . . . . . . . . . . . 8
1.4.2. Deliverability . . . . . . . . . . . . . . . . . . . 8
1.5. Other Protocols to Protect Email Header Fields . . . . . 9
1.6. Applicability to PGP/MIME . . . . . . . . . . . . . . . . 9
1.7. Requirements Language . . . . . . . . . . . . . . . . . . 10
1.8. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.9. Document Scope . . . . . . . . . . . . . . . . . . . . . 11
1.9.1. Out of Scope . . . . . . . . . . . . . . . . . . . . 12
2. Specification . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1. Injected Headers Scheme . . . . . . . . . . . . . . . . . 12
2.2. Wrapped Message Scheme . . . . . . . . . . . . . . . . . 13
2.3. Sending Side . . . . . . . . . . . . . . . . . . . . . . 13
2.3.1. Composing a Cryptographically-Protected Message Without
Header Protection . . . . . . . . . . . . . . . . . . 13
2.3.2. Header Confidentiality Policy . . . . . . . . . . . . 14
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2.3.3. Definition of HP-Removed and HP-Obscured header
fields . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.4. Composing with "Injected Headers" Header
Protection . . . . . . . . . . . . . . . . . . . . . 16
2.3.5. Composing with "Wrapped Message" Header Protection . 20
2.3.6. Choosing Between Wrapped Message and Injected
Headers . . . . . . . . . . . . . . . . . . . . . . . 22
2.4. Default Header Confidentiality Policy . . . . . . . . . . 22
2.4.1. Minimalist Header Confidentiality Policy . . . . . . 22
2.4.2. Strong Header Confidentiality Policy . . . . . . . . 23
2.4.3. Null Header Confidentiality Policy . . . . . . . . . 23
2.4.4. Offering Stronger Header Confidentiality . . . . . . 23
2.5. Receiving Side . . . . . . . . . . . . . . . . . . . . . 24
2.5.1. Identifying that a Message has Header Protection . . 24
2.5.2. Updating the Cryptographic Summary . . . . . . . . . 25
2.5.3. Rendering a Message with Injected Headers . . . . . . 25
2.5.4. Rendering a Wrapped Message . . . . . . . . . . . . . 28
2.5.5. Guidance for Automated Message Handling . . . . . . . 30
2.5.6. Affordances for Debugging and Troubleshooting . . . . 31
2.5.7. Rendering Other Schemes . . . . . . . . . . . . . . . 31
2.5.8. Composing a Reply to an Encrypted Message with Header
Protection . . . . . . . . . . . . . . . . . . . . . 32
2.5.9. Implicitly-rendered Header Fields . . . . . . . . . . 33
2.5.10. Unprotected Header Fields Added in Transit . . . . . 33
3. E-mail Ecosystem Evolution . . . . . . . . . . . . . . . . . 35
3.1. Dropping Legacy Display Elements . . . . . . . . . . . . 35
3.2. Stronger Default Header Confidentiality Policy . . . . . 35
4. Usability Considerations . . . . . . . . . . . . . . . . . . 36
4.1. Mixed Protections Within a Message Are Hard To
Understand . . . . . . . . . . . . . . . . . . . . . . . 37
4.2. Users Should Not Have To Choose a Header Confidentiality
Policy . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.3. Users Should Not Have To Choose a Header Protection
Scheme . . . . . . . . . . . . . . . . . . . . . . . . . 37
5. Security Considerations . . . . . . . . . . . . . . . . . . . 38
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 38
6.1. Encrypted Header Fields Are Not Always Private . . . . . 38
6.1.1. Encrypted Header Fields Can Be Inferred From External
Metadata . . . . . . . . . . . . . . . . . . . . . . 39
6.1.2. HCP May Not Mask All Data in an Encrypted Header
Field . . . . . . . . . . . . . . . . . . . . . . . . 39
6.1.3. An Intermediary Can Trick a Recipient into
Overestimating the Cryptographic Status of a Header Field
in an Encrypted Message . . . . . . . . . . . . . . . 39
6.1.4. Summary and Implementation Guidance . . . . . . . . . 40
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 41
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9.1. Normative References . . . . . . . . . . . . . . . . . . 41
9.2. Informative References . . . . . . . . . . . . . . . . . 42
Appendix A. Possible Problems with some Legacy Clients . . . . . 44
A.1. Problems Reviewing signed-and-encrypted Messages in List
View . . . . . . . . . . . . . . . . . . . . . . . . . . 44
A.2. Problems when Rendering a signed-and-encrypted Message . 44
A.3. Problems when Replying to a signed-and-encrypted
Message . . . . . . . . . . . . . . . . . . . . . . . . . 45
A.4. Problems Reviewing signed-only Messages in List View . . 46
A.5. Problems when Rendering a signed-only Message . . . . . . 46
A.6. Problems when Replying to a signed-only Message . . . . . 47
Appendix B. Test Vectors . . . . . . . . . . . . . . . . . . . . 47
B.1. Baseline Messages . . . . . . . . . . . . . . . . . . . . 47
B.1.1. No cryptographic protections over a simple message . 48
B.1.2. S/MIME signed-only signedData over a simple message, No
Header Protection . . . . . . . . . . . . . . . . . . 48
B.1.3. S/MIME signed-only multipart/signed over a simple
message, No Header Protection . . . . . . . . . . . . 50
B.1.4. S/MIME encrypted and signed over a simple message, No
Header Protection . . . . . . . . . . . . . . . . . . 52
B.1.5. No cryptographic protections over a complex
message . . . . . . . . . . . . . . . . . . . . . . . 55
B.1.6. S/MIME signed-only signedData over a complex message,
No Header Protection . . . . . . . . . . . . . . . . 56
B.1.7. S/MIME signed-only multipart/signed over a complex
message, No Header Protection . . . . . . . . . . . . 59
B.1.8. S/MIME encrypted and signed over a complex message, No
Header Protection . . . . . . . . . . . . . . . . . . 62
B.2. Signed-only Messages . . . . . . . . . . . . . . . . . . 65
B.2.1. S/MIME signed-only signedData over a simple message,
Wrapped Message . . . . . . . . . . . . . . . . . . . 65
B.2.2. S/MIME signed-only multipart/signed over a simple
message, Wrapped Message . . . . . . . . . . . . . . 67
B.2.3. S/MIME signed-only signedData over a simple message,
Injected Headers . . . . . . . . . . . . . . . . . . 70
B.2.4. S/MIME signed-only multipart/signed over a simple
message, Injected Headers . . . . . . . . . . . . . . 72
B.2.5. S/MIME signed-only signedData over a complex message,
Wrapped Message . . . . . . . . . . . . . . . . . . . 74
B.2.6. S/MIME signed-only multipart/signed over a complex
message, Wrapped Message . . . . . . . . . . . . . . 76
B.2.7. S/MIME signed-only signedData over a complex message,
Injected Headers . . . . . . . . . . . . . . . . . . 80
B.2.8. S/MIME signed-only multipart/signed over a complex
message, Injected Headers . . . . . . . . . . . . . . 82
B.3. Encrypted-and-signed Messages . . . . . . . . . . . . . . 85
B.3.1. S/MIME encrypted and signed over a simple message,
Wrapped Message with hcp_minimal . . . . . . . . . . 85
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B.3.2. S/MIME encrypted and signed over a simple message,
Injected Headers with hcp_minimal . . . . . . . . . . 88
B.3.3. S/MIME encrypted and signed over a simple message,
Injected Headers with hcp_minimal (+ Legacy Display) 91
B.3.4. S/MIME encrypted and signed over a simple message,
Wrapped Message with hcp_strong . . . . . . . . . . . 94
B.3.5. S/MIME encrypted and signed over a simple message,
Injected Headers with hcp_strong . . . . . . . . . . 97
B.3.6. S/MIME encrypted and signed over a simple message,
Injected Headers with hcp_strong (+ Legacy Display) . 101
B.3.7. S/MIME encrypted and signed reply over a simple
message, Wrapped Message with hcp_minimal . . . . . . 104
B.3.8. S/MIME encrypted and signed reply over a simple
message, Injected Headers with hcp_minimal . . . . . 107
B.3.9. S/MIME encrypted and signed reply over a simple
message, Injected Headers with hcp_minimal (+ Legacy
Display) . . . . . . . . . . . . . . . . . . . . . . 110
B.3.10. S/MIME encrypted and signed reply over a simple
message, Wrapped Message with hcp_strong . . . . . . 113
B.3.11. S/MIME encrypted and signed reply over a simple
message, Injected Headers with hcp_strong . . . . . . 117
B.3.12. S/MIME encrypted and signed reply over a simple
message, Injected Headers with hcp_strong (+ Legacy
Display) . . . . . . . . . . . . . . . . . . . . . . 120
B.3.13. S/MIME encrypted and signed over a complex message,
Wrapped Message with hcp_minimal . . . . . . . . . . 123
B.3.14. S/MIME encrypted and signed over a complex message,
Injected Headers with hcp_minimal . . . . . . . . . . 127
B.3.15. S/MIME encrypted and signed over a complex message,
Injected Headers with hcp_minimal (+ Legacy Display) 131
B.3.16. S/MIME encrypted and signed over a complex message,
Wrapped Message with hcp_strong . . . . . . . . . . . 135
B.3.17. S/MIME encrypted and signed over a complex message,
Injected Headers with hcp_strong . . . . . . . . . . 139
B.3.18. S/MIME encrypted and signed over a complex message,
Injected Headers with hcp_strong (+ Legacy Display) . 142
B.3.19. S/MIME encrypted and signed reply over a complex
message, Wrapped Message with hcp_minimal . . . . . . 146
B.3.20. S/MIME encrypted and signed reply over a complex
message, Injected Headers with hcp_minimal . . . . . 150
B.3.21. S/MIME encrypted and signed reply over a complex
message, Injected Headers with hcp_minimal (+ Legacy
Display) . . . . . . . . . . . . . . . . . . . . . . 154
B.3.22. S/MIME encrypted and signed reply over a complex
message, Wrapped Message with hcp_strong . . . . . . 159
B.3.23. S/MIME encrypted and signed reply over a complex
message, Injected Headers with hcp_strong . . . . . . 163
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B.3.24. S/MIME encrypted and signed reply over a complex
message, Injected Headers with hcp_strong (+ Legacy
Display) . . . . . . . . . . . . . . . . . . . . . . 167
Appendix C. Additional information . . . . . . . . . . . . . . . 171
C.1. Stored Variants of Messages with Bcc . . . . . . . . . . 171
Appendix D. Examples . . . . . . . . . . . . . . . . . . . . . . 171
D.1. Example text/plain Cryptographic Payload with Legacy
Display Elements . . . . . . . . . . . . . . . . . . . . 172
D.2. Example text/html Cryptographic Payload with Legacy Display
Elements . . . . . . . . . . . . . . . . . . . . . . . . 172
Appendix E. Document Changelog . . . . . . . . . . . . . . . . . 173
Appendix F. Open Issues . . . . . . . . . . . . . . . . . . . . 175
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 176
1. Introduction
Privacy and security issues regarding email Header Protection in S/
MIME have been identified for some time. Most current
implementations of cryptographically-protected electronic mail
protect only the body of the message, which leaves significant room
for attacks against otherwise-protected messages. For example, lack
of header protection allows an attacker to substitute the message
subject and/or author.
This document describes two different structures for how message
headers can be cryptographically protected, and provides guidance for
implementers of MUAs that generate and interpret such messages. It
takes particular care to ensure that messages interact reasonably
well with legacy MUAs.
1.1. Two Schemes of Header Protection
This document addresses two different schemes for cryptographically
protecting email header sections or fields and provides guidance to
implementers.
One scheme is the form specified in S/MIME 3.1 and later, which
involves wrapping a message/rfc822 or message/global MIME object with
a Cryptographic Envelope around the message to protect. This
document calls this scheme "Wrapped Message", and it is documented in
more detail in [RFC8551]. Experience has shown that this form does
not interact well with some legacy MUAs (see Section 1.2).
Consequently, another form of header protection is introduced, where
the protected header fields are placed directly on the Cryptographic
Payload, without using an intervening message/* MIME object. This
document calls this scheme "Injected Headers", and it is documented
in more detail in this document, in Section 2.3.4 and Section 2.5.3.
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1.2. Problems with Wrapped Messages
Several legacy MUAs have revealed rendering issues when dealing with
a message that uses the Wrapped Message header protection scheme.
In the worst cases, some mail user agents cannot render message/
rfc822 message subparts at all, in violation of baseline MIME
requirements as described on page 5 of [RFC2049]. This leaves all
wrapped messages unreadable by any recipient using such a MUA.
In other cases, the user sees an attachment suggesting a forwarded
email message, which -- in fact -- contains the protected email
message that should be rendered directly. In most of these cases,
the user can click on the attachment to view the protected message.
However, viewing the protected message as an attachment in isolation
may strip it of any security indications, leaving the user unable to
assess the cryptographic properties of the message. Worse, for
encrypted messages, interacting with the protected message in
isolation may leak contents of the cleartext, for example, if the
reply is not also encrypted.
1.3. Problems with Injected Headers
A legacy MUA dealing with an encrypted message that has some header
fields obscured using the Injected Headers scheme will not render the
obscured header fields to the user at all. A workaround "legacy
display" mechanism is provided in this document, which most legacy
MUAs should render to the user, albeit not in the same location that
the header fields would normally be rendered.
1.4. Motivation
Users generally do not understand the distinction between message
body and message header. When an e-mail message has cryptographic
protections that cover the message body, but not the header fields,
several attacks become possible.
For example, a legacy signed message has a signature that covers the
body but not the header fields. An attacker can therefore modify the
header fields (including the Subject header) without invalidating the
signature. Since most readers consider a message body in the context
of the message's Subject header, the meaning of the message itself
could change drastically (under the attacker's control) while still
retaining the same cryptographic indicator of authenticity.
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In another example, a legacy encrypted message has its body
effectively hidden from an adversary that snoops on the message. But
if the header fields are not also encrypted, significant information
about the message (such as the message Subject) will leak to the
inspecting adversary.
However, if the sending and receiving MUAs ensure that cryptographic
protections cover the message headers as well as the message body,
these attacks are defeated.
1.4.1. Backward Compatibility
If the sending MUA is unwilling to generate such a fully-protected
message due to the potential for rendering, usability,
deliverability, or security issues, these defenses cannot be
realized.
The sender cannot know what MUA (or MUAs) the recipient will use to
handle the message. Thus, an outbound message format that is
backward-compatible with as many legacy implementations as possible
is a more effective vehicle for providing the whole-message
cryptographic protections described above.
This document aims for backward compatibility with legacy clients to
the extent possible. In some cases, like when a user-visible header
like the Subject is cryptographically hidden, the message cannot
behave entirely identically to a legacy client. But accommodations
are described here that ensure a rough semantic equivalence for
legacy clients even in these cases.
1.4.2. Deliverability
A message that cannot be delivered is less useful than a message with
perfect cryptographic protections. Senders want their messages to
reach the intended recipients.
Given the current state of the Internet mail ecosystem, encrypted
messages in particular cannot shield all of their header fields from
visibility and still be guaranteed delivery to their intended
recipient.
This document accounts for this concern by providing a mechanism
(Section 2.3.2) that prioritizes initial deliverability (at the cost
of some header leakage) while facilitating future message variants
that shield more header metadata from casual inspection.
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1.5. Other Protocols to Protect Email Header Fields
A separate pair of protocols also provides some cryptographic
protection for the email message header integrity: DomainKeys
Identified Mail (DKIM) [RFC6376], as used in combination with Domain-
based Message Authentication, Reporting, and Conformance (DMARC)
[RFC7489]. This pair of protocols provides a domain-based reputation
mechanism that can be used to mitigate some forms of unsolicited
email (spam).
However, the DKIM+DMARC suite provides cryptographic protection at a
different scope than the mechanisms described here. In particular,
the message integrity and authentication signals provided by
DKIM+DMARC correspond to the domain name of the sending e-mail
address, not the sending address itself, so DKIM+DMARC not provide
end-to-end protection. DKIM+DMARC are typically applied to messages
by (and interpreted by) mail transfer agents, not mail user agents.
The mechanisms in this document are typically applied to messages by
(and interpreted by) mail user agents.
Furthermore, DKIM+DMARC only provides cryptographic integrity and
authentication, not encryption. So cryptographic confidentiality is
not available from that suite.
DKIM+DMARC can be used on any message, including messages formed as
described in this document. There should be no conflict between
these schemes.
Though not strictly e-mail, similar protections have been in use on
Usenet for signing and verification of message headers for years.
See ([PGPCONTROL] and [PGPVERIFY-FORMAT] for more details. Like
DKIM, these Usenet control protections offer only integrity and
authentication, not encryption.
1.6. Applicability to PGP/MIME
This document describes end-to-end cryptographic protections for
e-mail messages in reference to S/MIME ([RFC8551]).
Comparable end-to-end cryptographic protections can also be provided
by PGP/MIME ([RFC3156]).
The mechanisms in this document should be applicable in the PGP/MIME
protections as well as S/MIME protections, but analysis and
implementation in this document focuses on S/MIME.
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To the extent that any divergence from the mechanism described here
is necessary for PGP/MIME, that divergence is out of scope for this
document.
1.7. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.8. Terms
The following terms are defined for the scope of this document:
* S/MIME: Secure/Multipurpose Internet Mail Extensions (see
[RFC8551])
* PGP/MIME: MIME Security with OpenPGP (see [RFC3156])
* Message: An Email Message consisting of Header Fields
(collectively called "the Header Section of the message")
followed, optionally, by a Body; see [RFC5322].
Note: To avoid ambiguity, this document avoids using the terms
"Header" or "Headers" in isolation, but instead always uses
"Header Field" to refer to the individual field and "Header
Section" to refer to the entire collection.
* Header Field: A Header Field is a line beginning with a field
name, followed by a colon (":"), followed by a field body (value),
and terminated by CRLF; see [RFC5322].
* Header Section: The Header Section is a sequence of lines of
characters with special syntax as defined in [RFC5322]. The
Header Section of a Message contains the Header Fields associated
with the Message itself. The Header Section of a MIME part (that
is, a subpart of a message) typically contains Header Fields
associated with that particular MIME part.
* Body: The Body is the part of a Message that follows the Header
Section and is separated from the Header Section by an empty line
(i.e., a line with nothing preceding the CRLF); see [RFC5322]. It
is the (bottom) section of Message containing the payload of a
Message. Typically, the Body consists of a (possibly multipart)
MIME [RFC2045] construct.
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* Header Protection: cryptographic protection of email Header
Sections (or parts of it) for signatures and/or encryption
* Cryptographic Layer, Cryptographic Payload, Cryptographic
Envelope, Structural Headers, Main Body Part, User-Facing Headers,
and MUA are all used as defined in
[I-D.ietf-lamps-e2e-mail-guidance]
* Legacy MUA: a MUA that does not understand header protection as
described in this document. A Legacy Non-Crypto MUA is incapable
of doing any end-to-end cryptographic operations. A Legacy Crypto
MUA is capable of doing cryptographic operations, but does not
understand or generate messages with header protection.
* Wrapped Message: The header protection scheme that uses the
mechanism described in [RFC8551], where the Cryptographic Payload
is a message/rfc822 or message/global MIME object. (see
Section 2.2).
* Injected Headers: The header protection scheme that uses the
mechanism described in this document (see Section 2.1), where the
protected header fields are inserted on the Cryptographic Payload
directly.
* Header Confidentiality Policy: a functional specification of which
header fields should be obscured when composing an encrypted
message with header protection. See Section 2.3.2.
1.9. Document Scope
This document describes sensible, simple behavior for a program that
generates an e-mail message with standard end-to-end cryptographic
protections, following the guidance in
[I-D.ietf-lamps-e2e-mail-guidance]. An implementation conformant to
this draft will produce messages that have cryptographic protection
that covers the message's headers as well as its body.
This document also describes sensible, simple behavior for a program
that interprets such a message, in a way that can take advantage of
these protections covering the header fields as well as the body.
The message generation guidance aims to minimize negative
interactions with any legacy receiving client while providing
actionable cryptographic properties for modern receiving clients.
In particular, this document focuses on two standard types of
cryptographic protection that cover the entire message:
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* A cleartext message with a single signature, and
* An encrypted message that contains a single cryptographic
signature.
1.9.1. Out of Scope
While the generation guidance aims to provide minimal disruption for
any legacy client, such a client by definition does not implement
this document.
Therefore, the document does not attempt to provide guidance for
legacy clients.
Furthermore, this document does not explicitly contemplate unusual
(and tricky) variants of cryptographic message protections, including
any of these:
* Encrypted-only message (without a cryptographic signature)
* Triple-wrapped message
* Signed message with multiple signatures
* Encrypted message with a cryptographic signature outside the
encryption.
All such messages are out of scope.
2. Specification
As mentioned in Section 1.1, this document describes two ways to
provide end-to-end cryptographic protection for an e-mail message
that includes all header fields known to the sender at message
composition time.
A receiving MUA MUST be able to handle both header protection
schemes, as described in Section 2.5.
A sending MUA MUST be able to generate the Injected Headers scheme
(Section 2.3.4), and MAY generate the Wrapped Message scheme
(Section 2.3.5).
2.1. Injected Headers Scheme
A message that uses the Injected Headers scheme has protected header
fields in the header section of the Cryptographic Payload.
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For an encrypted message that has at least one user-visible header
field omitted or obscured outside of the Cryptographic Payload, those
header fields MAY also be duplicated into decorative copies in the
Main Body MIME part of the Cryptograhic Payload itself. These
decorative copies within the message are known as "legacy display
elements".
Composing a message with the Injected Headers scheme is described in
Section 2.3.4. Rendering such a message is described in
Section 2.5.3.
2.2. Wrapped Message Scheme
A message that uses the Wrapped Message scheme has a Cryptographic
payload of a single message/rfc822 (or message/global) MIME object,
which itself contains the original message (including the protected
header section).
Composing a message with the Wrapped Message scheme is described in
Section 2.3.5. Rendering such a message is described in
Section 2.5.4.
2.3. Sending Side
This section describes the process an MUA should use to apply
cryptographic protection to an e-mail message with header protection.
We start by describing the legacy message composition process as a
baseline.
2.3.1. Composing a Cryptographically-Protected Message Without Header
Protection
[I-D.ietf-lamps-e2e-mail-guidance] describes the typical process for
a legacy crypto MUA to apply cryptographic protections to an e-mail
message. That guidance and terminology is replicated here for
reference:
* origbody: the traditional unprotected message body as a well-
formed MIME tree (possibly just a single MIME leaf part). As a
well-formed MIME tree, origbody already has structural headers
(Content-*) present.
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* origheaders: the intended non-structural headers for the message,
represented here as a list of (h,v) pairs, where h is a header
field name and v is the associated value. Note that these are
header fields that the MUA intends to be visible to the recipient
of the message. In particular, if the MUA uses the Bcc header
during composition, but plans to omit it from the message (see
section 3.6.3 of [RFC5322]), it will not be in origheaders.
* crypto: The series of cryptographic protections to apply (for
example, "sign with the secret key corresponding to X.509
certificate X, then encrypt to X.509 certificates X and Y"). This
is a routine that accepts a MIME tree as input (the Cryptographic
Payload), wraps the input in the appropriate Cryptographic
Envelope, and returns the resultant MIME tree as output.
The algorithm returns a MIME object that is ready to be injected into
the mail system:
* Apply crypto to origbody, yielding MIME tree output
* For each header name and value (h,v) in origheaders:
- Add header h of output with value v
* Return output
2.3.2. Header Confidentiality Policy
When composing an encrypted message with header protection, the
composing MUA needs a Header Confidentiality Policy (HCP). In this
document, we represent that Header Confidentiality Policy as a
function hcp:
* hcp(name, val_in) --> val_out: this function takes a header field
name name and initial value val_in as arguments, and returns a
replacement header value val_out. If val_out is the special value
null, it mean that the header field in question should be omitted
from the set of header fields visible outside the Cryptographic
Envelope.
For example, an MUA that obscures the Subject header field by
replacing it with the literal string [...], hides all Cc'ed
recipients, and does not offer confidentiality to any other header
fields would be represented as (in pseudocode):
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hcp_example(name, val_in) → val_out:
if name is 'Subject':
return '[...]'
else if name is 'Cc':
return null
else:
return val_in
Note that such a policy is only needed when the end-to-end
protections include encryption (confidentiality). No comparable
policy is needed for other end-to-end cryptographic protections
(integrity and authenticity), as they are simply uniformly applied so
that all header fields known by the sender have these protections.
This asymmetry is an unfortunate consequence of complexities in
message delivery systems, some of which may reject, drop, or delay
messages where all header fields are removed from the top-level MIME
object.
This document does not mandate any particular Header Confidentiality
Policy, though it offers guidance for MUA implementers in selecting
one in Section 2.4. Future documents may recommend or mandate such a
policy for an MUA with specific needs. Such a recommendation might
be motivated by descriptions of metadata-derived attacks, or stem
from research about message deliverability, or describe new
signalling mechanisms, but these topics are out of scope for this
document.
2.3.3. Definition of HP-Removed and HP-Obscured header fields
This document defines 2 new header fields used for conveying the
effect of sender's Header Confidentiality Policy: HP-Removed and HP-
Obscured. These two MIME header fields should only ever appear
directly within the header section of the cryptographic payload of a
cryptographic envelope offering confidentiality.
HP-Removed includes a comma separated list of header field names that
were omitted from the outer header when the message with header
protection was generated. The HP-Removed header field can appear at
most once in the header section of a cryptographic payload.
Each instance of HP-Obscured contains a header field name and the
value that this header field was modified to in the outer header.
The HP-Obscured header field can appear multiple times in the header
section of a cryptographic payload.
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If a header field name A doesn't appear in an HP-Obscured header
field value, then the header field A was either removed (and thus
would appear in the HP-Removed header field) or it was copied without
any modifications to the outer header.
Syntax of these new header fields is defined using the following ABNF
[RFC5234]:
hp-removed = "HP-Removed:" field-name-list CRLF
field-name-list = [FWS] field-name
*([FWS] "," [FWS] field-name) [FWS]
hp-obscured = "HP-Obscured:" [FWS] field-name ": "
field-value CRLF
field-value = unstructured
2.3.4. Composing with "Injected Headers" Header Protection
The "Injected Headers" header protection scheme places the header
fields to be protected directly on the cryptographic payload. Unlike
in the "Wrapped Scheme" (see compose-wrapped-message), there is no
wrapping of the message body in any additional message/* MIME part.
This section describes how to generate such a message.
To compose a message using "Injected Headers" header protection, the
composing MUA needs one additional input in addition to the Header
Confidentiality Policy hcp defined in Section 2.3.2.
* legacy: a boolean value, indicating whether any recipient of the
message is believed to have a legacy client. If all recipients
are known to implement this draft, legacy should be set to false.
(How a MUA determines the value of legacy is out of scope for this
document; an initial implementation can simply set it to true)
Enabling visibility of obscured header fields for decryption-capable
legacy clients requires transforming a header list into a readable
form and including it as a decorative "Legacy Display" element in
specially-marked parts of the message. This document recommends two
different mechanisms for such a decorative adjustment: one for a
text/html Main Body part of the e-mail message, and one for a text/
plain Main Body part. This document does not recommend adding a
Legacy Display element to any other part.
Please see [I-D.ietf-lamps-e2e-mail-guidance] for guidance on
identifying the parts of a message that are a Main Body Part.
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The revised algorithm for applying cryptographic protection to a
message is as follows:
* if crypto contains encryption, and legacy is true:
- Create ldlist, an empty list of (header, value) pairs
- For each header field name and value (h,v) in origheaders:
o If h is user-facing (see
[I-D.ietf-lamps-e2e-mail-guidance]):
+ If hcp(h,v) is not v:
* Append (h,v) to ldlist
- If ldlist is not empty:
o Identify each leaf MIME part of payload that represents the
"main body" of the message.
o For each "Main Body Part" bodypart of type text/plain or
text/html:
+ Insert Legacy Display element header list ldlist into the
content of bodypart (see Section 2.3.4.1 for text/plain
and Section 2.3.4.2 for text/html)
+ Add Content-Type parameter hp-legacy-display with value 1
to bodypart
* For each header field name and value (h,v) in origheaders:
- Add header field h to MIME part payload with value v
* Set the protected-headers parameter on the Content-Type of payload
to v1
* Apply crypto to payload, producing MIME tree output
* If crypto contains encryption:
- Create new empty list of header field names and values newh
- Let hpr be an empty comma-separated list of header field names
- For header field name and value (h,v) in origheaders:
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o Let newval be hcp(h,v)
o If newval is null:
+ Add the value h to hpr
o Else (if newval is not null):
+ Add (h,newval) to newh
+ If newval is not v:
* Let string record be the concatenation of h, a literal
":" (colon followed by space), and newval
* Add header field "HP-Obscured" to MIME part payload
with value record
- If hpr is not empty:
o Add header field "HP-Removed" to MIME part payload with
value hpr
- Set origheaders to newh
* For each header field name and value (h,v) in origheaders:
- Add header field h to output with value v
* Return output
Note that both new parameters (hcp and legacy) are effectively
ignored if crypto does not contain encryption. This is by design,
because they are irrelevant for signed-only cryptographic
protections.
2.3.4.1. Adding a Legacy Display Element to a text/plain Part
For a list of obscured header fields represented as (header, value)
pairs, concatenate them as a set of lines, with one newline at the
end of each pair. Add an additional trailing newline after the
resultant text, and prepend the entire list to the body of the text/
plain part.
For example, if the list of obscured header fields was [("Cc",
"alice@example.net"), ("Subject", "Thursday's meeting")], then a
text/plain part that originally contained:
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I think we should skip the meeting.
Would become:
Subject: Thursday's meeting
Cc: alice@example.net
I think we should skip the meeting.
2.3.4.2. Adding a Legacy Display Element to a text/html Part
Adding a Legacy Display Element to a text/html part is similar to how
it is added to a text/plain part (see Section 2.3.4.1). Instead of
adding the obscured header fields to a block of text delimited by a
blank line, the composing MUA injects them in an HTML <div> element
annotated with a class attribute of header-protection-legacy-display.
The content and formatting of this decorative <div> have no strict
requirements, but they SHOULD represent all the obscured header
fields in a readable fashion. A simple approach is to assemble the
text in the same way as Section 2.3.4.1, wrap it in a verbatim <pre>
element, and put that element in the annotated <div>.
The annotated <div> should be placed as close to the start of the
<body> as possible, where it will be visible when viewed with a
standard HTML renderer.
For example, if the list of obscured header fields was [("Cc",
"alice@example.net"), ("Subject", "Thursday's meeting")], then a
text/html part that originally contained:
<html><head><title></title></head><body>
<p>I think we should skip the meeting.</p>
</body></html>
Would become:
<html><head><title></title></head><body>
<div class="header-protection-legacy-display">
<pre>Subject: Thursday's meeting
Cc: alice@example.net</pre></div>
<p>I think we should skip the meeting.</p>
</body></html>
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2.3.4.3. Only Add a Legacy Display Element to Main Body Parts
Some messages may contain a text/plain or text/html subpart that is
_not_ a main body part. For example, an e-mail message might contain
an attached text file or a downloaded webpage. Attached documents
need to be preserved as intended in the transmission, without
modification.
The composing MUA MUST NOT add a Legacy Display element to any part
of the message that is not a main body part. In particular, if a
part is annotated with Content-Disposition: attachment, or if it does
not descend via the first child of any of its multipart/mixed or
multipart/related ancestors, it is not a main body part, and MUST NOT
be modified.
See [I-D.ietf-lamps-e2e-mail-guidance] for more guidance about common
ways to distinguish main body parts from other MIME parts in a
message.
2.3.4.4. Do Not Add a Legacy Display Element to Other Content-Types
The purpose of injecting a Legacy Display element into each Main Body
MIME part is to enable rendering of otherwise obscured header fields
in legacy clients that are capable of message decryption, but don't
know how to follow the rest of the guidance in this document.
The authors are unaware of any legacy client that would render any
MIME part type other than text/plain and text/html as the Main Body.
A generating MUA SHOULD NOT add a Legacy Display element to any MIME
part with any other Content-Type.
2.3.5. Composing with "Wrapped Message" Header Protection
The Wrapped Message header protection scheme is briefly documented in
Section 3.1 [RFC8551]. This section provides a more detailed
explanation of how to build such a message, and augments it with the
forwarded parameter as described in
[I-D.melnikov-iana-reg-forwarded].
To compose a message using "Wrapped Message" header protection, we
use those inputs described in Section 2.3.1 plus the Header
Confidentiality Policy hcp defined in Section 2.3.2. The new
algorithm is:
* For header field name and value (h,v) in origheaders:
- Add header field h to origbody with value v
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* If crypto contains encryption:
- Create new empty list of header field names and values newh
- Let hpr be an empty comma-separated list of header field names
- For header field name and value (h,v) in origheaders:
o Let newval be hcp(h,v)
o If newval is null:
+ Add the value h to hpr
o Else (if newval is not null):
+ Append (h,newval) to newh
+ If newval is not v:
* Let string record be the concatenation of h, a literal
":" (colon followed by a space), and newval
* Add header field HP-Obscured to origbody with value
record
- If hpr is not empty:
o Add header field "HP-Removed" to MIME part payload with
value hpr
* If any of the header fields in origbody, including header fields
in the nested internal MIME structure, contain any 8-bit UTF-8
characters (see section section 3.7 of [RFC6532]):
- Let payload be a new MIME part with one header field: Content-
Type: message/global; forwarded=no, and whose body is origbody.
* Else:
- Let payload be a new MIME part with one header field: Content-
Type: message/rfc822; forwarded=no, and whose body is origbody.
* Apply crypto to payload, yielding MIME tree output
* If crypto contains encryption:
- Set origheaders to newh
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* For header field name and value (h,v) in origheaders:
- Add header field h to output with value v
* Return output
Note that the Header Confidentiality Policy hcp is ignored if crypto
does not contain encryption. This is by design.
2.3.6. Choosing Between Wrapped Message and Injected Headers
When composing a message with end-to-end cryptographic protections,
an MUA SHOULD protect the header fields of that message as well as
the body, using one of the formats described here.
A compatible MUA MUST be capable of generating a message with header
protection using the Injected Headers Section 2.3.4 format.
2.4. Default Header Confidentiality Policy
An MUA SHOULD have a sensible default Header Confidentiality Policy,
and SHOULD NOT require the user to select one. At the time this
document was written, a good choice for default HCP is the
conservative approach described by hcp_minimal (Section 2.4.1).
Any default Header Confidentiality Policy SHOULD provide
confidentiality for the Subject header field by replacing it with the
literal string [...]. Most users treat the Subject of a message the
same way that they treat the body, and they are surprised to find
that the Subject of an encrypted message is visible.
2.4.1. Minimalist Header Confidentiality Policy
The most conservative recommended Header Confidentiality Policy only
protects the Subject header field:
hcp_minimal(name, val_in) → val_out:
if name is 'Subject':
return '[...]'
else:
return val_in
hcp_minimal is the recommended default HCP for a new implementation,
as it provides meaningful confidentiality protections, and is
unlikely to cause deliverability or usability problems.
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2.4.2. Strong Header Confidentiality Policy
Alternately, a more aggressive (and therefore more privacy-
preserving) Header Confidentiality Policy only leaks a handful of
fields whose absence is known to increase rates of delivery failure,
and simultaneously obscures the Message-ID behind a random new one:
hcp_strong(name, val_in) → val_out:
if name in ['From', 'To', 'Cc', 'Date']:
return val_in
else if name is 'Subject':
return '[...]'
else if name is 'Message-ID':
return generate_new_message_id()
else:
return null
The function generate_new_message_id() represents whatever process
the MUA typically uses to generate a Message-ID for a new outbound
message.
hcp_strong is known to cause usability problems with message
threading for many legacy MUAs, and is not recommended as a default
HCP for new implementations.
2.4.3. Null Header Confidentiality Policy
Legacy MUAs can be conceptualized as offering a null Header
Confidentiality Policy, which offers no confidentiality protection to
any header field:
hcp_null(name, val_in) → val_out:
return val_in
A MUA offering header protection SHOULD NOT use hcp_null by default.
2.4.4. Offering Stronger Header Confidentiality
A MUA MAY offer even stronger confidentiality for header fields of an
encrypted message than described in Section 2.4.2. For example, it
might implement an HCP that obfuscates the From field, or omits the
Cc field, or ensures Date is represented in UTC (obscuring the local
timezone).
The authors of this document hope that implementers with deployment
experience will document their chosen Header Confidentiality Policy
and the rationale behind their choice.
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2.5. Receiving Side
An MUA that receives a cryptographically-protected e-mail will render
it for the user.
The receiving MUA will render the message body, a selected subset of
header fields, and (as described in
[I-D.ietf-lamps-e2e-mail-guidance]) provide a summary of the
cryptographic properties of the message.
Most MUAs only render a subset of header fields by default. For
example, few MUAs typically render Message-Id or Received header
fields for the user, but most do render From, To, Cc, Date, and
Subject.
A MUA that knows how to handle a message with header protection makes
the following two changes to its behavior when rendering a message:
* If it detects that an incoming message had protected header
fields, it renders header fields for the message from the
protected header fields, ignoring the external (unprotected)
header fields.
* It includes information in the message's cryptographic summary to
indicate the types of protection that applied to each rendered
header field (if any).
A MUA that handles a message with header protection does _not_ need
to render any new header fields that it did not render before.
2.5.1. Identifying that a Message has Header Protection
An incoming message can be identified as having header protection
based on one of two signals:
* The Cryptographic Payload has Content-Type: message/rfc822 or
Content-Type: message/global and the parameter forwarded has a
value of no. See Section 2.5.4 for rendering guidance.
* The Cryptographic Payload has some other Content-Type and it has
parameter protected-headers set to v1. See Section 2.5.3 for
rendering guidance.
Messages of both types exist in the wild, and a compliant MUA MUST be
able to handle them both. They provide the same semantics and the
same meaning.
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2.5.2. Updating the Cryptographic Summary
Regardless of whether a cryptographically-protected message has
protected header fields, the cryptographic summary of the message
should be modified to indicate what protections the header fields
have.
Each header field individually has exactly one the following
protections:
* unprotected (this is the case for all header fields in messages
that have no header protection)
* signed-only (bound into the same validated signature as the
enclosing message, but also visible in transit)
* encrypted-only (only appears within the cryptographic payload; the
corresponding external header field was either omitted or
obfuscated)
* signed-and-encrypted (same as encrypted-only, but additionally is
under a validated signature)
Note that while the message itself may be signed-and-encrypted, some
header fields may be replicated on the outside of the message (e.g.
Date). Those header fields would be signed-only, despite the message
itself being signed-and-encrypted. Additionally, the data from some
encrypted or signed-and-encrypted header fields may not be fully
private (see Section 6.1 for more details).
Rendering the cryptographic status of each header field is likely to
be complex and messy --- users may not understand it. It is beyond
the scope of this document to suggest any specific graphical
affordances or user experience. Future work should include examples
of successful rendering of this information.
2.5.3. Rendering a Message with Injected Headers
When the Cryptographic Payload does not have a Content-Type of
message/rfc822 or message/global, and the parameter protected-headers
is set to v1, the values of the protected header fields are drawn
from the header fields of the Cryptographic Payload, and the body
that is rendered is the Cryptographic Payload itself.
2.5.3.1. Example Signed-only Message with Injected Headers
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A └─╴application/pkcs7-mime; smime-type="signed-data"
⇩ (unwraps to)
B └┬╴multipart/alternative [Cryptographic Payload + Rendered Body]
C ├─╴text/plain
D └─╴text/html
The message body should be rendered the same way as this message:
B └┬╴multipart/alternative
C ├─╴text/plain
D └─╴text/html
It should render header fields taken from part B.
Its cryptographic summary should indicate that the message was signed
and all rendered header fields were included in the signature.
The MUA SHOULD ignore header fields from part A for the purposes of
rendering.
2.5.3.2. Example Signed-and-Encrypted Message with Injected Headers
Consider a message with this structure, where the MUA is able to
validate the cryptographic signature:
E └─╴application/pkcs7-mime; smime-type="enveloped-data"
↧ (decrypts to)
F └─╴application/pkcs7-mime; smime-type="signed-data"
⇩ (unwraps to)
G └┬╴multipart/alternative [Cryptographic Payload + Rendered Body]
H ├─╴text/plain
I └─╴text/html
The message body should be rendered the same way as this message:
G └┬╴multipart/alternative
H ├─╴text/plain
I └─╴text/html
It should render header fields taken from part G.
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Its cryptographic summary should indicate that the message was signed
and encrypted. As in Section 2.5.4.2, each rendered header field
found in G should be compared against the header field of the same
name from E. If the value found in E matches the value found in G,
the header field should be marked as signed-only. If no matching
header field was found in E, or the value found did not match the
value from G, the header field should be marked as signed-and-
encrypted.
2.5.3.3. Do Not Render Legacy Display Elements
As described in Section 2.1, a message with cryptographic
confidentiality protection MAY include "Legacy Display" elements for
backward-compatibility with legacy MUAs. These Legacy Display
elements are strictly decorative, unambiguously identifiable, and
will be discarded by compliant implementations.
The receiving MUA SHOULD avoid rendering the identified Legacy
Display elements to the user at all, since it is aware of header
protection and can render the actual protected header fields.
If a text/html or text/plain part within the cryptographic envelope
is identified as containing Legacy Display elements, those elements
should be hidden when rendering or generating a draft reply.
2.5.3.3.1. Identifying a Part with Legacy Display Elements
A receiving MUA acting on a message that contains an encrypting
Cryptographic Layer identifies a MIME subpart with within the
Cryptographic Payload as containing Legacy Display elements based on
the Content-Type of the subpart.
* The subpart's Content-Type contains a parameter hp-legacy-display
with value set to 1
* The subpart's Content-Type is either text/html (see
Section 2.5.3.3.3) or text/plain (see Section 2.5.3.3.2)
Note that the term "subpart" above is used in the general sense: if
the Cryptographic Payload is a single part, that part itself may
contain a Legacy Display element if it is marked with the hp-legacy-
display=1 parameter.
2.5.3.3.2. Omitting Legacy Display Elements from text/plain
If a text/plain part within the Cryptographic Payload has the
Content-Type parameter hp-legacy-display="1", it should be processed
before rendering in the following fashion:
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* Discard the leading lines of the body of the part up to and
including the first entirely blank line.
Note that implementing this strategy is dependent on the charset used
by the MIME part.
See Appendix D.1 for an example.
2.5.3.3.3. Omitting Legacy Display Elements from text/html
If a text/html part within the Cryptographic Payload has the Content-
Type parameter hp-legacy-display="1", it should be processed before
rendering in the following fashion:
* If any element of the HTML <body> is a <div> with class attribute
header-protection-legacy-display, that entire element should be
omitted.
A straightforward way for an HTML-capable MUA to do this is to add an
entry to the [CSS] stylesheet for such a part:
body div.header-protection-legacy-display { display: none; }
2.5.4. Rendering a Wrapped Message
Some MUAs may compose and send a message with end-to-end
cryptographic protections that offer header protection using the
Wrapped Message scheme described in Section 3.1 of [RFC8551]. This
section describes how a receiving MUA should identify and render such
a message.
When the Cryptographic Payload has Content-Type of message/rfc822 or
message/global, and the parameter forwarded is set to no, the values
of the protected header fields are drawn from the header fields of
the Cryptographic Payload, and the body that is rendered is the body
of the Cryptographic Payload.
2.5.4.1. Example Signed-Only Wrapped Message
Consider a message with this structure, where the MUA is able to
validate the cryptographic signature:
J └─╴application/pkcs7-mime; smime-type="signed-data"
⇩ (unwraps to)
K └┬╴message/rfc822 [Cryptographic Payload]
L └┬╴multipart/alternative [Rendered Body]
M ├─╴text/plain
N └─╴text/html
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The message body should be rendered the same way as this message:
L └┬╴multipart/alternative
M ├─╴text/plain
N └─╴text/html
It should render header fields taken from part K.
Its cryptographic summary should indicate that the message was signed
and all rendered header fields were included in the signature.
The MUA SHOULD ignore header fields from part J for the purposes of
rendering.
2.5.4.2. Example Signed-and-Encrypted Wrapped Message
Consider a message with this structure, where the MUA is able to
validate the cryptographic signature:
O └─╴application/pkcs7-mime; smime-type="enveloped-data"
↧ (decrypts to)
P └─╴application/pkcs7-mime; smime-type="signed-data"
⇩ (unwraps to)
Q └┬╴message/rfc822 [Cryptographic Payload]
R └┬╴multipart/alternative [Rendered Body]
S ├─╴text/plain
T └─╴text/html
The message body should be rendered the same way as this message:
R └┬╴multipart/alternative
S ├─╴text/plain
T └─╴text/html
It should render header fields taken from part Q.
Its cryptographic summary should indicate that the message was signed
and encrypted. Each rendered header field found in Q should be
compared against the header field of the same name from O. If the
value found in O matches the value found in Q, the header field
should be marked as signed-only. If no matching header field was
found in O, or the value found did not match the value from Q, the
header field should be marked as signed-and-encrypted.
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2.5.5. Guidance for Automated Message Handling
Some automated systems have a control channel that is operated by
e-mail. For example, an incoming e-mail message could subscribe
someone to a mailing list, initiate the purchase of a specific
product, approve another message for redistribution, or adjust the
state of some shared object.
To the extent that such a system depends on end-to-end cryptographic
guarantees about the e-mail control message, header protection as
described in this document should improve the system's security.
This section provides some specific guidance for systems that use
e-mail messages as a control channel that want to benefit from these
security improvements.
2.5.5.1. Interpret Only Protected Header Fields
Consider the situation where an e-mail-based control channel depends
on the message's cryptographic signature and the action taken depends
on some header field of the message.
In this case, the automated system MUST rely on information from the
header field that is protected by the mechanism described in this
document. It MUST NOT rely on any header field found outside the
cryptographic payload.
For example, consider an administrative interface for a mailing list
manager that only accepts control messages that are signed by one of
its administrators. When an inbound message for the list arrives, it
is queued (waiting for administrative approval) and the system
generates and listens for two distinct e-mail addresses related to
the queued message -- one that approves the message, and one that
rejects it. If an administrator sends a signed control message to
the approval address, the mailing list verifies that the protected
To: header field of the signed control message contains the approval
address before approving the queued message for redistribution. If
the protected To: header field does not contain that address, or
there is no protected To: header field, then the mailing list logs or
reports the error, and does not act on that control message.
2.5.5.2. Ignore Legacy Display Elements
Consider the situation where an e-mail based control channel expects
to receive an end-to-end encrypted message -- for example, where the
control messages need confidentiality guarantees -- and where the
action taken depends on the contents of some MIME part within message
body.
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In this case, the automated system that decrypts the incoming mssages
and scans the relevant MIME part SHOULD identify when the MIME part
contains a legacy display element (see Section 2.5.3.3.1), and it
SHOULD parse the relevant MIME part with the legacy display element
removed.
For example, consider an administrative interface of a confidential
issue tracking software. An authorized user can confidentially
adjust the status of a tracked issue by a specially-formatted first
line of the message body (for example, severity #183 serious). When
the user's MUA encrypts a plain text control message to this issue
tracker, depending on the MUA's HCP and its choice of legacy value,
it may add a legacy display element. If it does so, then the first
line of the message body will contain a decorative copy of the
confidential Subject: header field. The issue tracking software
decrypts the incoming control message, identifies that there is a
legacy display element in the part (see Section 2.5.3.3.1), strips
the legacy display lines (including the first blank line), and only
then parses the remaining top line to look for the expected special
formatting.
2.5.6. Affordances for Debugging and Troubleshooting
Note that advanced users of an MUA may need access to the original
message, for example to troubleshoot problems with the MUA itself, or
problems with the SMTP transport path taken by the message.
A MUA that applies these rendering guidelines SHOULD ensure that the
full original source of the message as it was received remains
available to such a user for debugging and troubleshooting.
2.5.7. Rendering Other Schemes
Other MUAs may have generated different structures of messages that
aim to offer end-to-end cryptographic protections that include header
protection.
While this document is not normative for those schemes, it offers
guidance for how to identify and handle these other formats. In the
following a list of systems that are known to generate email messages
with end-to-end cryptographic protections that include header
protection using a different MIME scheme.
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2.5.7.1. Pretty Easy Privacy (pEp)
The pEp (pretty Easy privacy) [I-D.pep-general] project specifies
MIME schemes for Signed-and-Encrypted email messages that also
provide header protection [I-D.pep-email]. Similar to the "Wrapped
Messages" scheme described in Section 2.3.5 and Section 2.5.4, pEp
email messages are fully encapsulated in the Cryptographic Payload.
More information can be found in [I-D.pep-email].
2.5.8. Composing a Reply to an Encrypted Message with Header Protection
When composing a reply to an encrypted message with header
protection, the MUA is acting both as a receiving MUA and as a
sending MUA. Special guidance applies here, as things can go wrong
in at least two ways: leaking previously-confidential information,
and replying to the wrong party.
2.5.8.1. Avoid Leaking Encrypted Header Fields in Reply
As noted in [I-D.ietf-lamps-e2e-mail-guidance], an MUA in this
position MUST NOT leak previously-encrypted content in the clear in a
followup message. The same is true for protected header fields.
Values from any header field that was identified as either encrypted-
only or signed-and-encrypted based on the steps outlined above MUST
NOT be placed in cleartext output when generating a message.
In particular, if Subject was encrypted, and it is copied into the
draft encrypted reply, the replying MUA MUST obfuscate the
unprotected (cleartext) Subject header field as described above.
[[ TODO: formally describe how a replying MUA should generate a
message-specific Header Protection policy based on the cryptographic
status of the headers of the incoming message ]]
2.5.8.2. Avoid Misdirected Replies to Encrypted Messages with Header
Protection
When replying to a message, the Composing MUA typically decides who
to send the reply to based on:
* the Reply-To, Mail-Followup-To, or From header fields
* optionally, the other To or Cc header fields (if the user chose to
"reply all")
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When a message has header protection, the replying MUA MUST populate
the destination fields of the draft message using the protected
header fields, and ignore any unprotected header fields.
This mitigates against an attack where Mallory gets a copy of an
encrypted message from Alice to Bob, and then replays the message to
Bob with an additional Cc to Mallory's own e-mail address in the
message's outer (unprotected) header section.
If Bob knows Mallory's certificate already, and he replies to such a
message without following the guidance in this section, it's likely
that his MUA will encrypt the cleartext of the message directly to
Mallory.
2.5.9. Implicitly-rendered Header Fields
While From and To and Cc and Subject and Date are often explicitly
rendered to the user, some header fields do affect message display,
without being explicitly rendered.
For example, Message-Id, References, and In-Reply-To header fields
may collectively be used to place a message in a "thread" or series
of messages.
In another example, Section 2.5.8.2 observes that the value of the
Reply-To field can influence the draft reply message. So while the
user may never see the Reply-To header field directly, it is
implicitly "rendered" when the user interacts with the message by
replying to it.
An MUA that depends on any implicitly-rendered header field in a
message with header protection SHOULD use the value from the
protected header field, and SHOULD NOT use any value found outside
the cryptographic protection.
2.5.10. Unprotected Header Fields Added in Transit
Some header fields are legitimately added in transit, and could not
have been known to the sender at message composition time.
The most common of these header fields are Received and DKIM-
Signature, neither of which are typically rendered, either explicitly
or implicitly.
If a receiving MUA has specific knowledge about a given header field,
including that:
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* the header field would not have been known to the original sender,
and
* the header field might be rendered explicitly or implicitly,
then the MUA MAY decide to operate on the value of that header field
from the unprotected header section, even though the message has
header protection.
The MUA MAY prefer to verify that the header fields in question have
additional transit-derived cryptographic protections (e.g., to test
whether they are covered by a valid DKIM-Signature, see [RFC6376])
before rendering or acting on them.
Specific examples appear below.
2.5.10.1. Mailing list header fields: List-* and Archived-At
If the message arrives through a mailing list, the list manager
itself may inject header fields (most of which start with List-) in
the message:
* List-Archive
* List-Subscribe
* List-Unsubscribe
* List-Id
* List-Help
* List-Post
* Archived-At
For some MUAs, these header fields are implicitly rendered, by
providing buttons for actions like "Subscribe", "View Archived
Version", "Reply List", "List Info", etc.
An MUA that receives a message with header protection that contains
these header fields in the unprotected section, and that has reason
to believe the message is coming through a mailing list MAY decide to
render them to the user (explicitly or implicitly) even though they
are not protected.
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3. E-mail Ecosystem Evolution
This document is intended to offer tooling needed to improve the
state of the e-mail ecosystem in a way that can be deployed without
significant disruption. Some elements of this specification are
present for transitional purposes, but would not exist if the system
were designed from scratch.
This section describes these transitional mechanisms, as well as some
suggestions for how they might eventually be phased out.
3.1. Dropping Legacy Display Elements
Any decorative Legacy Display element added to an encrypted message
that uses the Injected Header scheme is present strictly for enabling
header field visibility (most importantly, the Subject header field)
when the message is viewed with a decryption-capable legacy client.
Eventually, the hope is that most decryption-capable MUAs will
conform to this specification, and there will be no need for
injection of Legacy Display elements in the message body. A survey
of widely-used decryption-capable MUAs might be able to establish
when most of them do support this specification.
At that point, a composing MUA could make the legacy parameter
described in {#compose-injected-headers} to false by default, or
could even hard-code it to false, yielding a much simpler message
construction set.
Until that point, an end user might want to signal that their
receiving MUAs are conformant to this draft so that a peer composing
a message to them can set legacy to false. A signal indicating
capability of handling messages with header protection might be
placed in the user's cryptographic certificate, or in outbound
messages.
This draft doesn't attempt to define the syntax or semantics of such
a signal.
3.2. Stronger Default Header Confidentiality Policy
This draft defines two different forms of Header Confidentiality
Policy. A MUA implementing an HCP for the first time SHOULD deploy
hcp_minimal as recommended in Section 2.4. This HCP offers the most
commonly-expected protection (obscuring the Subject header field)
without risking deliverability or rendering issues.
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The HCPs proposed in this draft are relatively conservative and still
leak a significant amount of metadata for encrypted messages. This
is largely done to ensure deliverability (see Section 1.4.2) and
usability, as messages without some critical header fields are more
likely to not reach their intended recipient.
In the future, some mail transport systems may accept and deliver
messages with even less publicly-visible metadata. Many MTA
operators today would ask for additional guarantees about such a
message to limit the risks associated with abusive or spammy mail.
This specification offers the HCP formalism itself as a way for MUA
developers and MTA operators to describe their expectations around
message deliverability. MUA developers can propose a stronger
default HCP, and ask MTA operators (or simply test) whether their
MTAs would be likely to deliver or reject encrypted mail with that
HCP applied. Proponents of a stronger HCP should explicitly document
the HCP, and name it clearly and unambiguously to facilitate this
kind of interoperability discussion.
Reaching widespread consensus around a stronger global default HCP is
a challenging problem of coordinating many different actors. A
piecemeal approach might be more feasible, where some signalling
mechanism allows a message recipient, MTA operator, or third-party
clearinghouse to announce what kinds of HCPs are likely to be
deliverable for a given recipient. In such a situation, the default
HCP for a MUA might involve consulting the signalled acceptable HCPs
for all recipients, and combining them (along with a default for when
no signal is present) in some way.
If such a signal were to reach widespread use, it could also be used
to guide reasonable statistical default HCP choices for recipients
with no signal.
This draft doesn't attempt to define the syntax or semantics of such
a signal.
4. Usability Considerations
This section describes concerns for MUAs that are interested in easy
adoption of header protection by normal users.
While they are not protocol-level artifacts, these concerns motivate
the protocol features described in this document.
See also the Usability section in [I-D.ietf-lamps-e2e-mail-guidance].
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4.1. Mixed Protections Within a Message Are Hard To Understand
[[ TODO ]]
4.2. Users Should Not Have To Choose a Header Confidentiality Policy
This document defines the abstraction of a Header Confidentiality
Policy object for the sake of communication between implementers and
deployments.
Most e-mail users are unlikely to understand the tradeoffs between
different policies. In particular, the potential negative side
effects (e.g. poor deliverability) may not be easily attributable by
a normal user to a particular HCP.
Therefore, MUA implementers should be conservative in their choice of
default HCP, and should not require the ordinary user to make an
incomprehensible choice that could cause unfixable, undiagnosable
problems. The safest option is for the MUA developer to select a
known, stable HCP (this document recommends hcp_minimal in
Section 2.4) on the user's behalf. A MUA should not not expose the
ordinary user to a configuration option where they are expected to
manually select (let alone define) an HCP.
In the event that a MUA implementer gets user complaints about
problems with removed or obscured header fields due to the MUA's
defined HCP, the implementer may offer the user an option to drop
header confidentiality altogether for freshly composed messages
(thereby reverting to hcp_null). But when handling such a scenario
for a reply to a message with some header confidentiality policy in
place, note the guidance in Section 2.5.8.1 to avoid accidental
leakage.
4.3. Users Should Not Have To Choose a Header Protection Scheme
This document also describes two different header protection schemes:
Wrapped Messages in Section 2.2 and Injected Headers in Section 2.1.
These distinct schemes are described for the sake of implementers who
may have to deal with messages found in the wild, but their intended
semantics are identical. They represent different tradeoffs in terms
of rendering and user experience on the recipient's side, things that
a given user writing a message is not prepared to select.
When composing a message with cryptographic protections, the ordinary
user should not be confronted with any choices about which header
protection scheme to use. Rather, the MUA developer should use a
single scheme for all outboud cryptographically-protected messages.
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This document recommends the Injected Headers scheme for generating
messages with cryptographic protections, as described in Section 2.
A MUA should not expose the ordinary user to any configuration option
where they are expected to manually select, enable, or disable header
protections for new cryptographically-protected messages.
5. Security Considerations
This document describes a mechanism for improving the security of
cryptographically-protected e-mail messages. Following the guidance
in this document should improve security for users of these
technologies by more directly aligning the underlying messages with
user expectations about confidentiality, authenticity, and integrity.
However, many existing messages with cryptographic protections will
not have these protections, and MUAs encountering these messages will
need to handle older forms (without header protection) for quite some
time. An implementation that deals with legacy message archives will
need to deal with all the various formats forever. Helping the user
distinguish between cryptographic protections of various messages is
a difficult job for message renderers.
However, on the message generation side, the situation is much
clearer: there is a standard form that a protected message can take,
and an implementer can always generate the standard form. Generating
the standard form also makes it more likely that any receiving
implementation will be able to handle the generated message
appropriately.
6. Privacy Considerations
6.1. Encrypted Header Fields Are Not Always Private
For encrypted messages, depending on the sender's HCP, some header
fields may appear both within the Cryptographic Envelope and on the
outside of the message. Section 2.5.2 identifies those messages as
signed-only. These header fields are clearly _not_ private at all,
despite a copy being inside the Cryptographic Envelope.
A header field where the protected encrypted value does not match the
value outside the message have encrypted-only or signed-and-encrypted
status. But even header fields with these stronger levels of
cryptographic confidentiality protection might not be as private as
the user would like.
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6.1.1. Encrypted Header Fields Can Be Inferred From External Metadata
For example, if the To: and Cc: header fields are omitted from the
unprotected header section, the values in those fields might still be
inferred with high probability by an adversary who looks at the
message either in transit or at rest. If the message is found in, or
being delivered to a mailbox for bob@example.org, it's likely that
Bob was in either To: or Cc:. Additionally, an MTA that handles the
message may add a Received: header field (or some other custom header
field) that leaks some information about the nature of the delivery.
6.1.2. HCP May Not Mask All Data in an Encrypted Header Field
In another example, if the HCP modifies the Date: header to mask out
high-resolution time stamps (e.g. rounding to the most recent hour)
and to convert the local timezone to UTC, some information about the
date of delivery will still be attached to the e-mail. At the very
least, the low resolution, global version of the date will be present
on the message. Additionally, headers like Received that are added
during message delivery might include higher-resolution timestamps.
And if the message lands in a mailbox that is ordered by time of
receipt, even its placement in the mailbox and the non-obscured Date:
header fields of the surrounding messages could leak this
information.
Some fields like From: may be impossible to fully obscure, as many
modern message delivery systems depend on at least domain information
in the From: field for determining whether a message is coming from a
domain with "good reputation" (that is, from a domain that is not
known for leaking spam). So even if an aggressive HCP opts to remove
the human-readable part from any From: header field, and to
standardize/genericize the local part of the From: address, the
domain will still leak.
6.1.3. An Intermediary Can Trick a Recipient into Overestimating the
Cryptographic Status of a Header Field in an Encrypted Message
When an encrypted (or signed-and-encrypted) message is in transit, an
active intermediary can strip or tamper with any header field that
appears outside the Cryptographic Envelope.
For example, if the original sender's HCP passes through the Cc:
header field unchanged, a cleanly-delivered message would indicate
that the Cc: header field has a cryptographic status of signed. But
if an intermediary attacker simply removes the header field from the
unprotected header section before forwarding the message, then the
recipient would believe that the field has a cryptographic status of
signed-and-encrypted.
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An attacker can thus induce a false sense of confidentiality in a
recipient whose MUA actually did not provide that level of privacy.
This draft offers protection against such an attack by way of the HP-
Obscured and HP-Removed header fields that can be found on the
cryptographic payload. If a header field appears to have been
obscured, but no HP-Obscured header matches it; or if the header
field appears to have been removed, but the HP-Removed header does
not include its field name, the receiving MUA can indicate to the
user that the header field in question may not have been
confidential.
However, in such a case, a conservative MUA may still decide to treat
the header field in question as signed-and-encrypted during reply, to
avoid accidental leakage of the cleartext value in the reply message,
as described in Section 2.5.8.1.
6.1.4. Summary and Implementation Guidance
In the abstract sense, the above concerns are of course also true for
any encrypted data, including the body of the message: if the sender
isn't careful, the message contents or session keys could leak in
many different ways that are beyond the scope of this draft. The
message recipient has no way in principle to tell whether the
apparent confidentiality of any given piece of encrypted content has
been broken via channels that they cannot perceive. And an active
intermediary aware of the recipient's public key can always encrypt a
cleartext message in transit to give the recipient a false sense of
security.
A receiving MUA should be cautious about how it represents the
cryptographic status of encrypted-only and signed-and-encrypted
header fields to the user, to avoid overpromising. However, the MUA
should _also_ strive to avoid additional leakage of these header
fields, as described in Section 2.5.8.1.
7. IANA Considerations
This document request IANA to register the following header fields in
the "Permanent Message Header Field Names" Registry in accordance
with [RFC3864].
* Header field name: HP-Removed
* Applicable protocol: mail [RFC5322]
* Status: standard
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* Author/change controller: IETF
* Specification document(s): Section 2.3.3 of RFCXXX
* Header field name: HP-Obscured
* Applicable protocol: mail [RFC5322]
* Status: standard
* Author/change controller: IETF
* Specification document(s): Section 2.3.3 of RFCXXX
8. Acknowledgments
The authors would like to thank the following people who have
provided helpful comments and suggestions for this document: Berna
Alp, Bernhard E. Reiter, Claudio Luck, David Wilson, Hernani
Marques, juga, Krista Bennett, Kelly Bristol, Lars Rohwedder, Robert
Williams, Russ Housley, Sofia Balicka, Steve Kille, Volker Birk, and
Wei Chuang.
9. References
9.1. Normative References
[I-D.ietf-lamps-e2e-mail-guidance]
Gillmor, D. K., "Guidance on End-to-End E-mail Security",
Work in Progress, Internet-Draft, draft-ietf-lamps-e2e-
mail-guidance-04, 22 November 2022,
<https://www.ietf.org/archive/id/draft-ietf-lamps-e2e-
mail-guidance-04.txt>.
[I-D.ietf-lamps-header-protection-requirements]
Melnikov, A. and B. Hoeneisen, "Problem Statement and
Requirements for Header Protection", Work in Progress,
Internet-Draft, draft-ietf-lamps-header-protection-
requirements-01, 29 October 2019,
<https://www.ietf.org/archive/id/draft-ietf-lamps-header-
protection-requirements-01.txt>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<https://www.rfc-editor.org/info/rfc2045>.
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[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/info/rfc5322>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
9.2. Informative References
[CSS] World Wide Web Consortium, "Cascading Style Sheets Level 2
Revision 2 (CSS 2.2) Specification", 12 April 2016,
<https://www.w3.org/TR/2016/WD-CSS22-20160412/>.
[I-D.ietf-lamps-samples]
Gillmor, D. K., "S/MIME Example Keys and Certificates",
Work in Progress, Internet-Draft, draft-ietf-lamps-
samples-08, 2 February 2022,
<https://www.ietf.org/archive/id/draft-ietf-lamps-samples-
08.txt>.
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[I-D.melnikov-iana-reg-forwarded]
Melnikov, A. and B. Hoeneisen, "IANA Registration of
Content-Type Header Field Parameter 'forwarded'", Work in
Progress, Internet-Draft, draft-melnikov-iana-reg-
forwarded-00, 4 November 2019,
<https://www.ietf.org/archive/id/draft-melnikov-iana-reg-
forwarded-00.txt>.
[I-D.pep-email]
Marques, H., "pretty Easy privacy (pEp): Email Formats and
Protocols", Work in Progress, Internet-Draft, draft-pep-
email-01, 2 November 2020,
<https://www.ietf.org/archive/id/draft-pep-email-01.txt>.
[I-D.pep-general]
Birk, V., Marques, H., and B. Hoeneisen, "pretty Easy
privacy (pEp): Privacy by Default", Work in Progress,
Internet-Draft, draft-pep-general-01, 21 October 2022,
<https://www.ietf.org/archive/id/draft-pep-general-
01.txt>.
[PGPCONTROL]
UUNET Technologies, Inc., "Authentication of Usenet Group
Changes", 27 October 2016,
<https://ftp.isc.org/pub/pgpcontrol/>.
[PGPVERIFY-FORMAT]
Lawrence, D. C., "Signing Control Messages, Verifying
Control Messages", n.d.,
<https://www.eyrie.org/~eagle/usefor/other/pgpverify>.
[RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and
Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
<https://www.rfc-editor.org/info/rfc2049>.
[RFC3156] Elkins, M., Del Torto, D., Levien, R., and T. Roessler,
"MIME Security with OpenPGP", RFC 3156,
DOI 10.17487/RFC3156, August 2001,
<https://www.rfc-editor.org/info/rfc3156>.
[RFC6376] Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
"DomainKeys Identified Mail (DKIM) Signatures", STD 76,
RFC 6376, DOI 10.17487/RFC6376, September 2011,
<https://www.rfc-editor.org/info/rfc6376>.
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[RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized
Email Headers", RFC 6532, DOI 10.17487/RFC6532, February
2012, <https://www.rfc-editor.org/info/rfc6532>.
[RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based
Message Authentication, Reporting, and Conformance
(DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015,
<https://www.rfc-editor.org/info/rfc7489>.
Appendix A. Possible Problems with some Legacy Clients
When an e-mail message with end-to-end cryptographic protection is
received by a mail user agent, the user might experience many
different possible problematic interactions. A message with header
protection may introduce new forms of user experience failure.
In this section, the authors enumerate different kinds of failures we
have observed when reviewing, rendering, and replying to messages
with different forms of header protection in different legacy MUAs.
Different legacy MUAs demonstrate different subsets of these
problems.
Hopefully, a non-legacy MUA would not exhibit any of these problems.
An implementer updating their legacy MUA to be compliant with this
specification should consider these concerns and try to avoid them.
A.1. Problems Reviewing signed-and-encrypted Messages in List View
* Unprotected Subject, Date, From, To are visible
* Threading is not visible
A.2. Problems when Rendering a signed-and-encrypted Message
* Unprotected Subject is visible
* Protected subject (on its own) is visible in the body
* Protected subject, date, from, to visible in the body
* User interaction needed to view whole message
* User interaction needed to view message body
* User interaction needed to view protected subject
* Impossible to view protected subject
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* Nuisance alarms during user interaction
* Impossible to view message body
* Appears as a forwarded message
* Appears as an attachment
* Security indicators not visible
* User has multiple different methods to Reply: (e.g. reply to
outer, reply to inner)
* User sees English "Subject:" in body despite message itself being
in non-English
* Security indicators do not identify protection status of header
fields
* Header fields in body render with local header field names (e.g.
showing "Betreff" instead of "Subject") and dates (TZ, locale)
A.3. Problems when Replying to a signed-and-encrypted Message
Note that the use case here is:
* User views message, to the point where they can read it.
* User then replies to message, and they are shown a message
composition window, which has some UI elements
* If the MUA has multiple different methods to Reply: to a message,
each way may need to be evaluated separately
This section also uses the shorthand UI:x to mean "the UI element
that the user can edit that they think of as x."
* protected subject is in UI:subject (and will leak)
* protected subject is quoted in UI:body
* protected subject is not anywhere in UI
* message body is _not_ visible/quoted in UI:body
* user cannot reply while viewing protected message
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* reply is not encrypted by default (but is for normal S/MIME
sign+enc messages)
* unprotected From: is in UI:To
* User's locale (lang, TZ) leaks in quoted body
* Header fields not protected (and in particular, Subject is not
obscured) by default
A.4. Problems Reviewing signed-only Messages in List View
* Unprotected Subject, Date, From, To are visible
* Threading is not visible
A.5. Problems when Rendering a signed-only Message
* Unprotected Subject is visible
* Protected subject (on its own) is visible in the body
* Protected subject, date, from, to visible in the body
* User interaction needed to view whole message
* User interaction needed to view message body
* User interaction needed to view protected subject
* Impossible to view protected subject
* Nuisance alarms during user interaction
* Impossible to view message body
* Appears as a forwarded message
* Appears as an attachment
* Security indicators not visible
* Security indicators do not identify protection status of header
fields
* User has multiple different methods to Reply: (e.g. reply to
outer, reply to inner)
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* Header fields in body render with local header fields (e.g.
showing "Betreff" instead of "Subject") and dates (TZ, locale)
A.6. Problems when Replying to a signed-only Message
This uses the same use case(s) and shorthand as Appendix A.3.
* Unprotected Subject: is in UI:subject
* Protected Subject: is quoted in UI:body
* Protected Subject: is not anywhere in UI
* Message body is not visible/quoted in UI:body
* User cannot reply while viewing protected message
* Unprotected From: is in UI:To
* User's locale (lang, TZ) leaks in quoted body
Appendix B. Test Vectors
This section contains sample messages using the different schemes
described in this document. Each sample contains a MIME object, a
textual and diagrammatic view of its structure, and examples of how
an MUA might render it.
The cryptographic protections used in this document use the S/MIME
standard, and keying material and certificates come from
[I-D.ietf-lamps-samples].
These messages should be accessible to any IMAP client at
imap://bob@header-protection.cmrg.net/ (any password should
authenticate to this read-only IMAP mailbox).
You can also download copies of these test vectors separately at
https://header-protection.cmrg.net.
If any of the messages downloaded differ from those offered here,
this document is the canonical source.
B.1. Baseline Messages
These messages offer no header protection at all, and can be used as
a baseline. They are provided in this document as a counterexample.
An MUA implementer can use these messages to verify that the reported
cryptographic summary of the message indicates no header protection.
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B.1.1. No cryptographic protections over a simple message
This message uses no cryptographic protection at all. Its body is a
text/plain message.
It has the following structure:
└─╴text/plain 152 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Subject: no-crypto
Message-ID: <no-crypto@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:00:02 -0500
User-Agent: Sample MUA Version 1.0
This is the no-crypto message.
This message uses no cryptographic protection at all. Its body
is a text/plain message.
--
Alice
alice@smime.example
B.1.2. S/MIME signed-only signedData over a simple message, No Header
Protection
This is a signed-only S/MIME message via PKCS#7 signedData. The
payload is a text/plain message. It uses no header protection.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 3852 bytes
⇩ (unwraps to)
└─╴text/plain 204 bytes
Its contents are:
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Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="signed-data"
Subject: smime-one-part
Message-ID: <smime-one-part@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:01:02 -0500
User-Agent: Sample MUA Version 1.0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0fqXgq4SWcC0nsG1lyyXt1TL270I6ATKRGJWiQVCCpDtc0NT6vdJ45bCSzsCAwEA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B.1.3. S/MIME signed-only multipart/signed over a simple message, No
Header Protection
This is a signed-only S/MIME message via PKCS#7 detached signature
(multipart/signed). The payload is a text/plain message. It uses no
header protection.
It has the following structure:
└┬╴multipart/signed 4191 bytes
├─╴text/plain 224 bytes
└─╴application/pkcs7-signature [smime.p7s] 3429 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: multipart/signed;
protocol="application/pkcs7-signature"; boundary="052";
micalg="sha-256"
Subject: smime-multipart
Message-ID: <smime-multipart@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:02:02 -0500
User-Agent: Sample MUA Version 1.0
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--052
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
This is the smime-multipart message.
This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a text/plain
message. It uses no header protection.
--
Alice
alice@smime.example
--052
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature; name="smime.p7s"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/evPgP96wV+z4TtAwW2Z34rTiz4DxMI07XYNFUEOls/gkUP2GxzymsO2kaYWTut3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--052--
B.1.4. S/MIME encrypted and signed over a simple message, No Header
Protection
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses no header protection.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 6720 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 3960 bytes
⇩ (unwraps to)
└─╴text/plain 239 bytes
Its contents are:
Gillmor, et al. Expires 26 May 2023 [Page 52]
Internet-Draft Header Protection S/MIME November 2022
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: smime-enc-signed
Message-ID: <smime-enc-signed@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:03:02 -0500
User-Agent: Sample MUA Version 1.0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, et al. Expires 26 May 2023 [Page 53]
Internet-Draft Header Protection S/MIME November 2022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, et al. Expires 26 May 2023 [Page 54]
Internet-Draft Header Protection S/MIME November 2022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B.1.5. No cryptographic protections over a complex message
This message uses no cryptographic protection at all. Its body is a
multipart/alternative message with an inline image/png attachment.
It has the following structure:
└┬╴multipart/mixed 1406 bytes
├┬╴multipart/alternative 794 bytes
│├─╴text/plain 206 bytes
│└─╴text/html 304 bytes
└─╴image/png inline 232 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="c39"
Subject: no-crypto-complex
Message-ID: <no-crypto-complex@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:00:02 -0500
User-Agent: Sample MUA Version 1.0
--c39
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="05a"
--05a
Gillmor, et al. Expires 26 May 2023 [Page 55]
Internet-Draft Header Protection S/MIME November 2022
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
This is the no-crypto-complex message.
This message uses no cryptographic protection at all. Its body
is a multipart/alternative message with an inline image/png
attachment.
--
Alice
alice@smime.example
--05a
Content-Type: text/html; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
<html><head><title></title></head><body>
<p>This is the <b>no-crypto-complex</b> message.</p>
<p>This message uses no cryptographic protection at all. Its body
is a multipart/alternative message with an inline image/png
attachment.</p>
<p><tt>-- <br/>Alice<br/>alice@smime.example</tt></p></body></html>
--05a--
--c39
Content-Type: image/png
Content-Transfer-Encoding: base64
Content-Disposition: inline
iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAcElEQVR42uVTOxbA
MAgS739nO3TpRw20dqpbfARQEjOywiwYnCtkDKnbcLk66sqlT+zt9cidkE+6KwkZ
sgrzfcqVMpL2jo0447gYDpeArk+OnJHkIhAfTPRicihAf5YJrw7vjv0ZWRWM/uli
vdPf1QZ2kDD9xppd8wAAAABJRU5ErkJggg==
--c39--
B.1.6. S/MIME signed-only signedData over a complex message, No Header
Protection
This is a signed-only S/MIME message via PKCS#7 signedData. The
payload is a multipart/alternative message with an inline image/png
attachment. It uses no header protection.
It has the following structure:
Gillmor, et al. Expires 26 May 2023 [Page 56]
Internet-Draft Header Protection S/MIME November 2022
└─╴application/pkcs7-mime [smime.p7m] 5249 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 1288 bytes
├┬╴multipart/alternative 882 bytes
│├─╴text/plain 258 bytes
│└─╴text/html 353 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="signed-data"
Subject: smime-one-part-complex
Message-ID: <smime-one-part-complex@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:01:02 -0500
User-Agent: Sample MUA Version 1.0
MIIPHwYJKoZIhvcNAQcCoIIPEDCCDwwCAQExDTALBglghkgBZQMEAgEwggVIBgkq
hkiG9w0BBwGgggU5BIIFNU1JTUUtVmVyc2lvbjogMS4wDQpDb250ZW50LVR5cGU6
IG11bHRpcGFydC9taXhlZDsgYm91bmRhcnk9IjMzZSINCg0KLS0zM2UNCk1JTUUt
VmVyc2lvbjogMS4wDQpDb250ZW50LVR5cGU6IG11bHRpcGFydC9hbHRlcm5hdGl2
ZTsgYm91bmRhcnk9ImUwYiINCg0KLS1lMGINCkNvbnRlbnQtVHlwZTogdGV4dC9w
bGFpbjsgY2hhcnNldD0idXMtYXNjaWkiDQpNSU1FLVZlcnNpb246IDEuMA0KQ29u
dGVudC1UcmFuc2Zlci1FbmNvZGluZzogN2JpdA0KDQpUaGlzIGlzIHRoZSBzbWlt
ZS1vbmUtcGFydC1jb21wbGV4IG1lc3NhZ2UuDQoNClRoaXMgaXMgYSBzaWduZWQt
b25seSBTL01JTUUgbWVzc2FnZSB2aWEgUEtDUyM3IHNpZ25lZERhdGEuICBUaGUN
CnBheWxvYWQgaXMgYSBtdWx0aXBhcnQvYWx0ZXJuYXRpdmUgbWVzc2FnZSB3aXRo
IGFuIGlubGluZQ0KaW1hZ2UvcG5nIGF0dGFjaG1lbnQuIEl0IHVzZXMgbm8gaGVh
ZGVyIHByb3RlY3Rpb24uDQoNCi0tIA0KQWxpY2UNCmFsaWNlQHNtaW1lLmV4YW1w
bGUNCi0tZTBiDQpDb250ZW50LVR5cGU6IHRleHQvaHRtbDsgY2hhcnNldD0idXMt
YXNjaWkiDQpNSU1FLVZlcnNpb246IDEuMA0KQ29udGVudC1UcmFuc2Zlci1FbmNv
ZGluZzogN2JpdA0KDQo8aHRtbD48aGVhZD48dGl0bGU+PC90aXRsZT48L2hlYWQ+
PGJvZHk+DQo8cD5UaGlzIGlzIHRoZSA8Yj5zbWltZS1vbmUtcGFydC1jb21wbGV4
PC9iPiBtZXNzYWdlLjwvcD4NCjxwPlRoaXMgaXMgYSBzaWduZWQtb25seSBTL01J
TUUgbWVzc2FnZSB2aWEgUEtDUyM3IHNpZ25lZERhdGEuICBUaGUNCnBheWxvYWQg
aXMgYSBtdWx0aXBhcnQvYWx0ZXJuYXRpdmUgbWVzc2FnZSB3aXRoIGFuIGlubGlu
ZQ0KaW1hZ2UvcG5nIGF0dGFjaG1lbnQuIEl0IHVzZXMgbm8gaGVhZGVyIHByb3Rl
Y3Rpb24uPC9wPg0KPHA+PHR0Pi0tIDxici8+QWxpY2U8YnIvPmFsaWNlQHNtaW1l
LmV4YW1wbGU8L3R0PjwvcD48L2JvZHk+PC9odG1sPg0KLS1lMGItLQ0KDQotLTMz
ZQ0KQ29udGVudC1UeXBlOiBpbWFnZS9wbmcNCkNvbnRlbnQtVHJhbnNmZXItRW5j
b2Rpbmc6IGJhc2U2NA0KQ29udGVudC1EaXNwb3NpdGlvbjogaW5saW5lDQoNCmlW
Qk9SdzBLR2dvQUFBQU5TVWhFVWdBQUFCUUFBQUFVQ0FZQUFBQ05pUjBOQUFBQWNF
bEVRVlI0MnVWVE94YkENCk1BZ1M3MzluTzNUcFJ3MjBkcXBiZkFSUUVqT3l3aXdZ
bkN0a0RLbmJjTGs2NnNxbFQrenQ5Y2lka0UrNkt3a1oNCnNncnpmY3FWTXBMMmpv
MDQ0N2dZRHBlQXJrK09uSkhrSWhBZlRQUmljaWhBZjVZSnJ3N3ZqdjBaV1JXTS91
Gillmor, et al. Expires 26 May 2023 [Page 57]
Internet-Draft Header Protection S/MIME November 2022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, et al. Expires 26 May 2023 [Page 58]
Internet-Draft Header Protection S/MIME November 2022
e+HEQjN6bKft5zulMCqh7NKRpRmDcEE9RXDGKGYQ9BKBf6Od/04lolBY/xpPu9G5
XnUTHN3MmqubrTSP3xxU5AozL8i7XmkB68VxKBQ2YpfcXBFGbuvlc6FXkbh2QtRX
UgBZEp+GSxG7o0UVJRa97t6wblUdMwaQ1ONrtBsmrO46bThv4cgrlGBvz8tGfHwR
4HbS/Rp+6jNAS0K9fZ0PQxy2b4M4braYg3f1n4q3dDH8N0XiUcwG8FiB9XQo18+D
fdkZwTVUoDHWjSVdIREobdPI2wdpnGxS/AB1VuiYpcebi4o=
B.1.7. S/MIME signed-only multipart/signed over a complex message, No
Header Protection
This is a signed-only S/MIME message via PKCS#7 detached signature
(multipart/signed). The payload is a multipart/alternative message
with an inline image/png attachment. It uses no header protection.
It has the following structure:
└┬╴multipart/signed 5234 bytes
├┬╴multipart/mixed 1344 bytes
│├┬╴multipart/alternative 938 bytes
││├─╴text/plain 278 bytes
││└─╴text/html 376 bytes
│└─╴image/png inline 232 bytes
└─╴application/pkcs7-signature [smime.p7s] 3429 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: multipart/signed;
protocol="application/pkcs7-signature"; boundary="452";
micalg="sha-256"
Subject: smime-multipart-complex
Message-ID: <smime-multipart-complex@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:02:02 -0500
User-Agent: Sample MUA Version 1.0
--452
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="ac5"
--ac5
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="813"
--813
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Gillmor, et al. Expires 26 May 2023 [Page 59]
Internet-Draft Header Protection S/MIME November 2022
This is the smime-multipart-complex message.
This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a
multipart/alternative message with an inline image/png
attachment. It uses no header protection.
--
Alice
alice@smime.example
--813
Content-Type: text/html; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
<html><head><title></title></head><body>
<p>This is the <b>smime-multipart-complex</b> message.</p>
<p>This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a
multipart/alternative message with an inline image/png
attachment. It uses no header protection.</p>
<p><tt>-- <br/>Alice<br/>alice@smime.example</tt></p></body></html>
--813--
--ac5
Content-Type: image/png
Content-Transfer-Encoding: base64
Content-Disposition: inline
iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAcElEQVR42uVTOxbA
MAgS739nO3TpRw20dqpbfARQEjOywiwYnCtkDKnbcLk66sqlT+zt9cidkE+6KwkZ
sgrzfcqVMpL2jo0447gYDpeArk+OnJHkIhAfTPRicihAf5YJrw7vjv0ZWRWM/uli
vdPf1QZ2kDD9xppd8wAAAABJRU5ErkJggg==
--ac5--
--452
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature; name="smime.p7s"
MIIJ4AYJKoZIhvcNAQcCoIIJ0TCCCc0CAQExDTALBglghkgBZQMEAgEwCwYJKoZI
hvcNAQcBoIIHpjCCA88wggK3oAMCAQICEw8tJb0ROZdKzkJUh6HuPTQGirQwDQYJ
KoZIhvcNAQENBQAwVTENMAsGA1UEChMESUVURjERMA8GA1UECxMITEFNUFMgV0cx
MTAvBgNVBAMTKFNhbXBsZSBMQU1QUyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3Jp
dHkwIBcNMTkxMTIwMDY1NDE4WhgPMjA1MjA5MjcwNjU0MThaMDsxDTALBgNVBAoT
BElFVEYxETAPBgNVBAsTCExBTVBTIFdHMRcwFQYDVQQDEw5BbGljZSBMb3ZlbGFj
ZTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAJqVKfqLwaLjj+gBUCfk
acKTg8cc2OtJ9ZSed6U3jUoiZVpMLcP3MUKtLeLg9r1mAfIDlB/wlbdmadXPmrsz
Gillmor, et al. Expires 26 May 2023 [Page 60]
Internet-Draft Header Protection S/MIME November 2022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--452--
Gillmor, et al. Expires 26 May 2023 [Page 61]
Internet-Draft Header Protection S/MIME November 2022
B.1.8. S/MIME encrypted and signed over a complex message, No Header
Protection
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses no
header protection.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 8690 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 5426 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 1356 bytes
├┬╴multipart/alternative 950 bytes
│├─╴text/plain 293 bytes
│└─╴text/html 388 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: smime-enc-signed-complex
Message-ID: <smime-enc-signed-complex@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:03:02 -0500
User-Agent: Sample MUA Version 1.0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B.2. Signed-only Messages
These messages are signed-only, using different schemes of header
protection and different S/MIME structure. The use no Header
Confidentiality Policy because the hcp is only relevant when a
message is encrypted.
B.2.1. S/MIME signed-only signedData over a simple message, Wrapped
Message
This is a signed-only S/MIME message via PKCS#7 signedData. The
payload is a text/plain message. It uses the Wrapped Message header
protection scheme.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 4262 bytes
⇩ (unwraps to)
└┬╴message/rfc822 601 bytes
└─╴text/plain 228 bytes
Its contents are:
Gillmor, et al. Expires 26 May 2023 [Page 65]
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Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="signed-data"
Subject: smime-one-part-wrapped
Message-ID: <smime-one-part-wrapped@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:04:02 -0500
User-Agent: Sample MUA Version 1.0
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jqB8+dz2AwYeMxODWq9opwtA/lTOkRg8uuivZfg/m5fFo/QshlHNaaTDVEXsU4Ps
98Hm/3gznbvhdjFbZbi4oZ3tAadRlE5K9JiQaJYOnUmGpfB8PPwDR6chMZeegSQA
W++OIKqHrg/WEh4yiuPfqmAvX2hZkPpivNJYdTPUXTSO7K459CyqbqG+sNOo2kc1
nTXl85RHNrVKQK+L0YWY1Q+hWDCCA88wggK3oAMCAQICEzdBBXntdX9CqaJcOvT4
as6aqdcwDQYJKoZIhvcNAQENBQAwVTENMAsGA1UEChMESUVURjERMA8GA1UECxMI
TEFNUFMgV0cxMTAvBgNVBAMTKFNhbXBsZSBMQU1QUyBSU0EgQ2VydGlmaWNhdGlv
biBBdXRob3JpdHkwIBcNMTkxMTIwMDY1NDE4WhgPMjA1MjA5MjcwNjU0MThaMDsx
Gillmor, et al. Expires 26 May 2023 [Page 66]
Internet-Draft Header Protection S/MIME November 2022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5wKuDjFCAJPiZCe6IXm0fx/z4kr5YCFJ2yG/Cu4jjSHFZR8/JRz8O83rBbD1kFiX
YiA8QWQtlXYvSZumZzYSSOzs3H/5HfAINCyVICMJc9Z5IQjNhXKUWfZc8NwpJMsC
909/PC03aMXRSfIewlcYZRR/j/fp0c06V9zzYlDDzSCwjayysNQP89HkZiX90PuA
Mo3c2j5FiD1FkaMrXsE4fEAapQ8uTufzD0s=
B.2.2. S/MIME signed-only multipart/signed over a simple message,
Wrapped Message
This is a signed-only S/MIME message via PKCS#7 detached signature
(multipart/signed). The payload is a text/plain message. It uses
the Wrapped Message header protection scheme.
It has the following structure:
└┬╴multipart/signed 4521 bytes
├┬╴message/rfc822 631 bytes
│└─╴text/plain 256 bytes
└─╴application/pkcs7-signature [smime.p7s] 3429 bytes
Its contents are:
Gillmor, et al. Expires 26 May 2023 [Page 67]
Internet-Draft Header Protection S/MIME November 2022
MIME-Version: 1.0
Content-Type: multipart/signed;
protocol="application/pkcs7-signature"; boundary="b43";
micalg="sha-256"
Subject: smime-multipart-wrapped
Message-ID: <smime-multipart-wrapped@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:05:02 -0500
User-Agent: Sample MUA Version 1.0
--b43
MIME-Version: 1.0
Content-Type: message/rfc822; forwarded="no"
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Subject: smime-multipart-wrapped
Message-ID: <smime-multipart-wrapped@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:05:02 -0500
User-Agent: Sample MUA Version 1.0
This is the smime-multipart-wrapped message.
This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a text/plain
message. It uses the Wrapped Message header protection scheme.
--
Alice
alice@smime.example
--b43
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature; name="smime.p7s"
MIIJ4AYJKoZIhvcNAQcCoIIJ0TCCCc0CAQExDTALBglghkgBZQMEAgEwCwYJKoZI
hvcNAQcBoIIHpjCCA88wggK3oAMCAQICEw8tJb0ROZdKzkJUh6HuPTQGirQwDQYJ
KoZIhvcNAQENBQAwVTENMAsGA1UEChMESUVURjERMA8GA1UECxMITEFNUFMgV0cx
MTAvBgNVBAMTKFNhbXBsZSBMQU1QUyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3Jp
dHkwIBcNMTkxMTIwMDY1NDE4WhgPMjA1MjA5MjcwNjU0MThaMDsxDTALBgNVBAoT
BElFVEYxETAPBgNVBAsTCExBTVBTIFdHMRcwFQYDVQQDEw5BbGljZSBMb3ZlbGFj
ZTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAJqVKfqLwaLjj+gBUCfk
acKTg8cc2OtJ9ZSed6U3jUoiZVpMLcP3MUKtLeLg9r1mAfIDlB/wlbdmadXPmrsz
yidmbuZmOpB5voVQfiLYYy3iOx7YOqzXrl6udP07k0sV+UdSNRFxrfKeoQEFXgOa
Gillmor, et al. Expires 26 May 2023 [Page 68]
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Gdmnx4OG/e3p1fIKM0dPzZLoOAJF5m5O0xzXPL74zFCWp2f1ZkuE4A6l41koaZXC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bKZa1oPTUNlm6QpivtqDIdqGJdGf8L1zLfXBuo2zL3HR+M9CDr4Opq2JCkzP0Qhp
7poIccGE6I9Tsg+RrOA9iCQsPn1+Tg8YedjGzUWF07rNmT0TzPCVzUAuBlr+JJtz
OKypyQ3eoZ6EPazXqMyHAVcsm0GI364IOA0b8PSrJNtjh+AqJ5QfH+0e7NSzNnEm
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MC8GCSqGSIb3DQEJBDEiBCCMT6eYpntC4UCFZCclaeFvHRBSPNVDL943812L5TpB
LDANBgkqhkiG9w0BAQEFAASCAQCmWUt7zv57UxTSan7aQOmP1ikFFnS+R/baXlC0
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L55XclHNt0CkMhjwphosBRniyknGjQbg6cwiUjoFxLGnc/jW
--b43--
Gillmor, et al. Expires 26 May 2023 [Page 69]
Internet-Draft Header Protection S/MIME November 2022
B.2.3. S/MIME signed-only signedData over a simple message, Injected
Headers
This is a signed-only S/MIME message via PKCS#7 signedData. The
payload is a text/plain message. It uses the Injected Headers header
protection scheme.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 4234 bytes
⇩ (unwraps to)
└─╴text/plain 239 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="signed-data"
Subject: smime-one-part-injected
Message-ID: <smime-one-part-injected@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:06:02 -0500
User-Agent: Sample MUA Version 1.0
MIIMMgYJKoZIhvcNAQcCoIIMIzCCDB8CAQExDTALBglghkgBZQMEAgEwggJbBgkq
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9r1mAfIDlB/wlbdmadXPmrszyidmbuZmOpB5voVQfiLYYy3iOx7YOqzXrl6udP07
k0sV+UdSNRFxrfKeoQEFXgOaGdmnx4OG/e3p1fIKM0dPzZLoOAJF5m5O0xzXPL74
zFCWp2f1ZkuE4A6l41koaZXCN5XL7wWTLMLeNf9Byb5ksKqUuqEHAMd1nmoNMgjY
Gillmor, et al. Expires 26 May 2023 [Page 70]
Internet-Draft Header Protection S/MIME November 2022
9VfVfcrv9w43GG8FtpSX+TWzB2zNS2OF+XIVnzRG5DeoULq8v88Z5bLpIJ/nx26r
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/wrb+5CS85FLWuHRuKm85dkUFTANBgkqhkiG9w0BAQEFAASCAQBE/g/trAYogNeF
9oD6esBshX+oPQp8AhmTNr5mdEi+YCHauiO4z94lPIGHwPGGI220cly1C68bMsjT
HPlaumv6zhotJym5OtJH1nD0cOxeqMSP+/htEgb/YmOTs1tGL5W6MRDE2Qpk+ZT+
skuKKBT98a/VQGEmyIZSTJV9SmiapvYDb9BA+KPuFZ0Yd/vMtTjq1dRBzadE9byX
O10GDNMBiqOeDeVcfU2j/rb3UELfJqSpiTqEST/JIq1PvZHr+En2Z0PfMA7BKjTm
sl/sczGLBObDAJztOOG7oU83zowcKn0JNse2cKU2eQMAENtuahfaXzVrmbfsW665
Mrfom9Z/
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B.2.4. S/MIME signed-only multipart/signed over a simple message,
Injected Headers
This is a signed-only S/MIME message via PKCS#7 detached signature
(multipart/signed). The payload is a text/plain message. It uses
the Injected Headers header protection scheme.
It has the following structure:
└┬╴multipart/signed 4487 bytes
├─╴text/plain 258 bytes
└─╴application/pkcs7-signature [smime.p7s] 3429 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: multipart/signed;
protocol="application/pkcs7-signature"; boundary="f1e";
micalg="sha-256"
Subject: smime-multipart-injected
Message-ID: <smime-multipart-injected@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:07:02 -0500
User-Agent: Sample MUA Version 1.0
--f1e
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: smime-multipart-injected
Message-ID: <smime-multipart-injected@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:07:02 -0500
User-Agent: Sample MUA Version 1.0
Content-Type: text/plain; charset="utf-8"; protected-headers="v1"
This is the smime-multipart-injected message.
This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a text/plain
message. It uses the Injected Headers header protection scheme.
--
Alice
alice@smime.example
--f1e
Gillmor, et al. Expires 26 May 2023 [Page 72]
Internet-Draft Header Protection S/MIME November 2022
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature; name="smime.p7s"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9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0yMTAyMjAxNTA3MDJa
MC8GCSqGSIb3DQEJBDEiBCA6Rhu8s2iPcyWQk+TNKhP9ZHJ9+wulWjsMpAF1NXCE
jDANBgkqhkiG9w0BAQEFAASCAQB4QMAYf42dnAelBRb2NotiixNgdjdSpVK75af6
oND3UjdCWcd4bPbrfTZMQKp0FBPoOft9lw2fWNgXwKbhD1cL3RWUmUq0zcNbI3XI
86vWp79p+KwM/+SyDdfgudIRGjbs/tmKaBvaH89a8SvuxhNxq/pxgDzpy/JWC8Er
AUDTbKrNVsYD+MfzMy9B0TlK2YLKoQ6rV0N1n2nXbW0e+Ztv0a/getNKAEAP+5hE
OQkq50RxUP9pI5kQ1NdU6zqCNhRjmd1wnMxn45K+hfY8cxwwemFn94PgDGpPG4mB
yRXQPj+5oyduWiHRMLXG1+fs4tqxHZXN+WaUHvSIDqNXK3rj
--f1e--
B.2.5. S/MIME signed-only signedData over a complex message, Wrapped
Message
This is a signed-only S/MIME message via PKCS#7 signedData. The
payload is a multipart/alternative message with an inline image/png
attachment. It uses the Wrapped Message header protection scheme.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 5680 bytes
⇩ (unwraps to)
└┬╴message/rfc822 1648 bytes
└┬╴multipart/mixed 1584 bytes
├┬╴multipart/alternative 946 bytes
│├─╴text/plain 282 bytes
│└─╴text/html 380 bytes
└─╴image/png inline 232 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="signed-data"
Subject: smime-one-part-complex-wrapped
Message-ID: <smime-one-part-complex-wrapped@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:04:02 -0500
User-Agent: Sample MUA Version 1.0
MIIQXQYJKoZIhvcNAQcCoIIQTjCCEEoCAQExDTALBglghkgBZQMEAgEwggaGBgkq
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bGU+CkZyb206IEFsaWNlIDxhbGljZUBzbWltZS5leGFtcGxlPgpUbzogQm9iIDxi
Gillmor, et al. Expires 26 May 2023 [Page 74]
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b2JAc21pbWUuZXhhbXBsZT4KRGF0ZTogU2F0LCAyMCBGZWIgMjAyMSAxMjowNDow
MiAtMDUwMApVc2VyLUFnZW50OiBTYW1wbGUgTVVBIFZlcnNpb24gMS4wCgotLTFk
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bnRlbnQtVHJhbnNmZXItRW5jb2Rpbmc6IDdiaXQKClRoaXMgaXMgdGhlIHNtaW1l
LW9uZS1wYXJ0LWNvbXBsZXgtd3JhcHBlZCBtZXNzYWdlLgoKVGhpcyBpcyBhIHNp
Z25lZC1vbmx5IFMvTUlNRSBtZXNzYWdlIHZpYSBQS0NTIzcgc2lnbmVkRGF0YS4g
IFRoZQpwYXlsb2FkIGlzIGEgbXVsdGlwYXJ0L2FsdGVybmF0aXZlIG1lc3NhZ2Ug
d2l0aCBhbiBpbmxpbmUKaW1hZ2UvcG5nIGF0dGFjaG1lbnQuIEl0IHVzZXMgdGhl
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Eh4yiuPfqmAvX2hZkPpivNJYdTPUXTSO7K459CyqbqG+sNOo2kc1nTXl85RHNrVK
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iv8oLV7Fno8/9kc5EikI2ux89aGhPkegvyDx1gnLajIcjKvMvvL10KwV3YK/cvLG
dUPDI6/U5wu7tFjO8A2Wkj4=
B.2.6. S/MIME signed-only multipart/signed over a complex message,
Wrapped Message
This is a signed-only S/MIME message via PKCS#7 detached signature
(multipart/signed). The payload is a multipart/alternative message
with an inline image/png attachment. It uses the Wrapped Message
header protection scheme.
It has the following structure:
Gillmor, et al. Expires 26 May 2023 [Page 76]
Internet-Draft Header Protection S/MIME November 2022
└┬╴multipart/signed 5612 bytes
├┬╴message/rfc822 1706 bytes
│└┬╴multipart/mixed 1642 bytes
│ ├┬╴multipart/alternative 1002 bytes
│ │├─╴text/plain 310 bytes
│ │└─╴text/html 408 bytes
│ └─╴image/png inline 232 bytes
└─╴application/pkcs7-signature [smime.p7s] 3429 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: multipart/signed;
protocol="application/pkcs7-signature"; boundary="1dd";
micalg="sha-256"
Subject: smime-multipart-complex-wrapped
Message-ID: <smime-multipart-complex-wrapped@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:05:02 -0500
User-Agent: Sample MUA Version 1.0
--1dd
MIME-Version: 1.0
Content-Type: message/rfc822; forwarded="no"
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="a30"
Subject: smime-multipart-complex-wrapped
Message-ID: <smime-multipart-complex-wrapped@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:05:02 -0500
User-Agent: Sample MUA Version 1.0
--a30
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="844"
--844
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
This is the smime-multipart-complex-wrapped message.
This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a
Gillmor, et al. Expires 26 May 2023 [Page 77]
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multipart/alternative message with an inline image/png
attachment. It uses the Wrapped Message header protection
scheme.
--
Alice
alice@smime.example
--844
Content-Type: text/html; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
<html><head><title></title></head><body>
<p>This is the <b>smime-multipart-complex-wrapped</b> message.</p>
<p>This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a
multipart/alternative message with an inline image/png
attachment. It uses the Wrapped Message header protection
scheme.</p>
<p><tt>-- <br/>Alice<br/>alice@smime.example</tt></p></body></html>
--844--
--a30
Content-Type: image/png
Content-Transfer-Encoding: base64
Content-Disposition: inline
iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAcElEQVR42uVTOxbA
MAgS739nO3TpRw20dqpbfARQEjOywiwYnCtkDKnbcLk66sqlT+zt9cidkE+6KwkZ
sgrzfcqVMpL2jo0447gYDpeArk+OnJHkIhAfTPRicihAf5YJrw7vjv0ZWRWM/uli
vdPf1QZ2kDD9xppd8wAAAABJRU5ErkJggg==
--a30--
--1dd
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature; name="smime.p7s"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N5XL7wWTLMLeNf9Byb5ksKqUuqEHAMd1nmoNMgjY9VfVfcrv9w43GG8FtpSX+TWz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cml0eQITN0EFee11f0Kpolw69Phqzpqp1zALBglghkgBZQMEAgGgaTAYBgkqhkiG
9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0yMTAyMjAxNzA1MDJa
MC8GCSqGSIb3DQEJBDEiBCA1zCXdvmyUdnAjEayGwsTfRb8LzslPryiqROPrKMYD
TTANBgkqhkiG9w0BAQEFAASCAQAnLKYYseI7mqyx59HGWR50IQOZBIoURPXGixq/
FkUxnLYCB1vsqcSYEf6LSnTc80jLYRyeqaML9BNT/6uJDzo2o6mqFmayzv40Zb2G
a2X3503JCQzQOFWX3zu6Wz8yaSUryMDF8toh6N+68eJ+Bp3EXhE1T24lpRalxSGZ
sc2d15lz3bY4RBbqOUf5zFPIEA3E20wwZT1ldUuqgFFORHmZm9I+ZOUFwkN28oIu
PQptk54Dbr2o7h3jxLEj6/S1p0ErZ5NurHVZzdmPT3UwLlub59a1cQiTXut82nw/
mS8oNv/2EF/CDMr+90F+QaXEggC9EEKjJenTJZUtxqgtpwQm
--1dd--
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B.2.7. S/MIME signed-only signedData over a complex message, Injected
Headers
This is a signed-only S/MIME message via PKCS#7 signedData. The
payload is a multipart/alternative message with an inline image/png
attachment. It uses the Injected Headers header protection scheme.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 5700 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 1614 bytes
├┬╴multipart/alternative 950 bytes
│├─╴text/plain 293 bytes
│└─╴text/html 388 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="signed-data"
Subject: smime-one-part-complex-injected
Message-ID: <smime-one-part-complex-injected@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:06:02 -0500
User-Agent: Sample MUA Version 1.0
MIIQbQYJKoZIhvcNAQcCoIIQXjCCEFoCAQExDTALBglghkgBZQMEAgEwggaWBgkq
hkiG9w0BBwGgggaHBIIGg01JTUUtVmVyc2lvbjogMS4wDQpTdWJqZWN0OiBzbWlt
ZS1vbmUtcGFydC1jb21wbGV4LWluamVjdGVkDQpNZXNzYWdlLUlEOiA8c21pbWUt
b25lLXBhcnQtY29tcGxleC1pbmplY3RlZEBsaHAuZXhhbXBsZT4NCkZyb206IEFs
aWNlIDxhbGljZUBzbWltZS5leGFtcGxlPg0KVG86IEJvYiA8Ym9iQHNtaW1lLmV4
YW1wbGU+DQpEYXRlOiBTYXQsIDIwIEZlYiAyMDIxIDEyOjA2OjAyIC0wNTAwDQpV
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DQpNSU1FLVZlcnNpb246IDEuMA0KQ29udGVudC1UcmFuc2Zlci1FbmNvZGluZzog
N2JpdA0KDQpUaGlzIGlzIHRoZSBzbWltZS1vbmUtcGFydC1jb21wbGV4LWluamVj
dGVkIG1lc3NhZ2UuDQoNClRoaXMgaXMgYSBzaWduZWQtb25seSBTL01JTUUgbWVz
c2FnZSB2aWEgUEtDUyM3IHNpZ25lZERhdGEuICBUaGUNCnBheWxvYWQgaXMgYSBt
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c21pbWUuZXhhbXBsZQ0KLS05MDcNCkNvbnRlbnQtVHlwZTogdGV4dC9odG1sOyBj
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aGFyc2V0PSJ1cy1hc2NpaSINCk1JTUUtVmVyc2lvbjogMS4wDQpDb250ZW50LVRy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VokFQgqQ7XNDU+r3SeOWwks7AgMBAAGjga8wgawwDAYDVR0TAQH/BAIwADAXBgNV
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Y/0eNARD6/oF0/sYonX2doizcGMk53riugAocCn5zbzhW/JVdYn30UxfyrZlRAzE
f7GHqgB/NyjOad3pdpVYeDh4ciNKjbs+aEoTWgAkoqENt1sRxlcvb7HVX524bKZa
1oPTUNlm6QpivtqDIdqGJdGf8L1zLfXBuo2zL3HR+M9CDr4Opq2JCkzP0Qhp7poI
ccGE6I9Tsg+RrOA9iCQsPn1+Tg8YedjGzUWF07rNmT0TzPCVzUAuBlr+JJtzOKyp
yQ3eoZ6EPazXqMyHAVcsm0GI364IOA0b8PSrJNtjh+AqJ5QfH+0e7NSzNnEmMYIC
ADCCAfwCAQEwbDBVMQ0wCwYDVQQKEwRJRVRGMREwDwYDVQQLEwhMQU1QUyBXRzEx
MC8GA1UEAxMoU2FtcGxlIExBTVBTIFJTQSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0
eQITN0EFee11f0Kpolw69Phqzpqp1zALBglghkgBZQMEAgGgaTAYBgkqhkiG9w0B
CQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0yMTAyMjAxNzA2MDJaMC8G
CSqGSIb3DQEJBDEiBCC84gf/+no5va6ErXhHIk1xELMQNWg9BUh8E1M78W5u5TAN
BgkqhkiG9w0BAQEFAASCAQB+q8buLwucKfPrBoXxKP7ZaJ/ifg8Y4Axf84AhNJXC
+NWzThUSgq12Fn9cdSVO858oDrWDSndd/zwgab0TgQZ+64atwiQ7bVTDkG8qgeT+
I/R1I8jGOCUTpkKcK34tOYbmhkc7/2BLITc3qOAxuN+lrsWVL2NF8LFGh9RbfzRu
WFVqAMyfAo9DRr1PeFDoDQnjAGti37M8/WvftXixxOAevVmFUWbpnFiwdvSwdrt0
CKquQ1NYbFAvxOawxLU0jFqhIgW10+fU4jqQDukUVSKFiw1/dK+7jlZC6sCXf3Ys
oHRhxqY/bSsgXn1DUWSDjhae3HnlZuoVXLJDHGCd6oSR
B.2.8. S/MIME signed-only multipart/signed over a complex message,
Injected Headers
This is a signed-only S/MIME message via PKCS#7 detached signature
(multipart/signed). The payload is a multipart/alternative message
with an inline image/png attachment. It uses the Injected Headers
header protection scheme.
It has the following structure:
└┬╴multipart/signed 5580 bytes
├┬╴multipart/mixed 1672 bytes
│├┬╴multipart/alternative 1006 bytes
││├─╴text/plain 312 bytes
││└─╴text/html 410 bytes
│└─╴image/png inline 232 bytes
└─╴application/pkcs7-signature [smime.p7s] 3429 bytes
Its contents are:
MIME-Version: 1.0
Content-Type: multipart/signed;
protocol="application/pkcs7-signature"; boundary="f91";
micalg="sha-256"
Subject: smime-multipart-complex-injected
Message-ID: <smime-multipart-complex-injected@lhp.example>
Gillmor, et al. Expires 26 May 2023 [Page 82]
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From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:07:02 -0500
User-Agent: Sample MUA Version 1.0
--f91
MIME-Version: 1.0
Subject: smime-multipart-complex-injected
Message-ID: <smime-multipart-complex-injected@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:07:02 -0500
User-Agent: Sample MUA Version 1.0
Content-Type: multipart/mixed; boundary="099"; protected-headers="v1"
--099
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="9a5"
--9a5
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
This is the smime-multipart-complex-injected message.
This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a
multipart/alternative message with an inline image/png
attachment. It uses the Injected Headers header protection
scheme.
--
Alice
alice@smime.example
--9a5
Content-Type: text/html; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
<html><head><title></title></head><body>
<p>This is the <b>smime-multipart-complex-injected</b> message.</p>
<p>This is a signed-only S/MIME message via PKCS#7 detached
signature (multipart/signed). The payload is a
multipart/alternative message with an inline image/png
attachment. It uses the Injected Headers header protection
scheme.</p>
<p><tt>-- <br/>Alice<br/>alice@smime.example</tt></p></body></html>
Gillmor, et al. Expires 26 May 2023 [Page 83]
Internet-Draft Header Protection S/MIME November 2022
--9a5--
--099
Content-Type: image/png
Content-Transfer-Encoding: base64
Content-Disposition: inline
iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAcElEQVR42uVTOxbA
MAgS739nO3TpRw20dqpbfARQEjOywiwYnCtkDKnbcLk66sqlT+zt9cidkE+6KwkZ
sgrzfcqVMpL2jo0447gYDpeArk+OnJHkIhAfTPRicihAf5YJrw7vjv0ZWRWM/uli
vdPf1QZ2kDD9xppd8wAAAABJRU5ErkJggg==
--099--
--f91
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-signature; name="smime.p7s"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SryCqeHEFbZFkB4urMk4xrIJC3CzWruS2Q0FHbBlfkgKN5wXVgkWFfiOucfCn+IQ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--f91--
B.3. Encrypted-and-signed Messages
These messages are encrypted and signed. They use PKCS#7 signedData
inside envelopedData, with different header protection schemes and
different Header Confidentiality Policies.
B.3.1. S/MIME encrypted and signed over a simple message, Wrapped
Message with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Wrapped Message header protection scheme with
the hcp_minimal Header Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7475 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4522 bytes
⇩ (unwraps to)
└┬╴message/rfc822 742 bytes
└─╴text/plain 321 bytes
Gillmor, et al. Expires 26 May 2023 [Page 85]
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Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <smime-enc-signed-wrapped-minimal@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:08:02 -0500
User-Agent: Sample MUA Version 1.0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To1oCrpPGXaO9L99dTw7wNjTY8t09zuoI5SFkIm4OEn6csRuFyBwlPv7KQSG6rDb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11mvM2Hn4XpkNgH5Oykk8MksFXuQkXvkuyPGXmTezj/UD0jO0iPjjZbaDtOIEHbR
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4X3aekeHM/qkzNPnvHm1g0FxLNmqf+r+Bevmpc+z0iMUbTBmYdrWp9fOtXqDWYyg
zBh8v8YJAMfFG8NX0Kzdb2vCm3+2YKcV/t5e+oFRjcUSDjjLS6I7TeBxMrTz001K
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OqyDpxXbdy4cd71EDJ6pPvh9GIOI/zj8b2JBc7CRAqNchy/DoqEy1+n5PFzKzfu0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Gillmor, et al. Expires 26 May 2023 [Page 87]
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B.3.2. S/MIME encrypted and signed over a simple message, Injected
Headers with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_minimal Header Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7435 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4498 bytes
⇩ (unwraps to)
└─╴text/plain 333 bytes
Gillmor, et al. Expires 26 May 2023 [Page 88]
Internet-Draft Header Protection S/MIME November 2022
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <smime-enc-signed-injected-minimal@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:09:02 -0500
User-Agent: Sample MUA Version 1.0
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Gillmor, et al. Expires 26 May 2023 [Page 90]
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M33AKEIwZjG7lmnCnURdu5YNA9Q1hBgjshd7tHAZI57I8UwdX/GrH/jGm3Zd0L38
xPfZpa9QSr2Fs/f54Zje/G+9vK543k5PY26PckeSxVFrAc1eLNRRXuP0DHVc5xxX
pwj+ARVUo23qb2bn2j3Rk8u41Z+mtOq4YmLc5Q6a0M034HTqrc4jiHU0Hy2nekJV
pBbOU/BFByUFHn+M1h6yRtgQjVKmC88O/aBb5u7MqrOsQ6cvNqHfs3A12HgjBxga
+vBLwEHtHYgBOeZRdIeQwA==
B.3.3. S/MIME encrypted and signed over a simple message, Injected
Headers with hcp_minimal (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_minimal Header Confidentiality Policy with a "Legacy Display"
part.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7670 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4674 bytes
⇩ (unwraps to)
└─╴text/plain 423 bytes
Gillmor, et al. Expires 26 May 2023 [Page 91]
Internet-Draft Header Protection S/MIME November 2022
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-injected-minimal-legacy@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:10:02 -0500
User-Agent: Sample MUA Version 1.0
MIIWHAYJKoZIhvcNAQcDoIIWDTCCFgkCAQAxggMQMIIBhAIBADBsMFUxDTALBgNV
BAoTBElFVEYxETAPBgNVBAsTCExBTVBTIFdHMTEwLwYDVQQDEyhTYW1wbGUgTEFN
UFMgUlNBIENlcnRpZmljYXRpb24gQXV0aG9yaXR5AhMPLSW9ETmXSs5CVIeh7j00
Boq0MA0GCSqGSIb3DQEBAQUABIIBAA7foZVL0cKGxTAGMEqr24xmXk+R9+1tBvxo
vVC0FR62j6F3bEqRPggJoL/HYhvhbCluNzS462O1GUESTn6dU0sFnAtHvpm/aggs
ywFJsWc/fzzIyEN9wQ5X+2BWM9SofTEikdGaUUz/fub8KpV3ZHmpO+boNOMRWys5
gOR9GFt+iv5LEdqhvaymsdFs/qKAZBZo28ffE4DsanZEVmYufMriwoyRtyqnHD4A
hmihNTH5ZCdeUUSZXb0w/UP9TWlQ9C3m663fywaS1zUNaol4gEpTcto76D/FohGk
s9mZ4vFcBgGWzH7GJWJFWE4VRCQoNiWC4H8y+wIqfIDE9d4isEMwggGEAgEAMGww
VTENMAsGA1UEChMESUVURjERMA8GA1UECxMITEFNUFMgV0cxMTAvBgNVBAMTKFNh
bXBsZSBMQU1QUyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkCEzB8R0APhiY6
HGLS64MvlsDXhpQwDQYJKoZIhvcNAQEBBQAEggEASY3CY6TZFO/11DvnkCjzRwpZ
S+1JJ7S/t7cPtxZxd8ZVVAmNmVEvYkcXsCNbvUrTy2BlVFWYKuPOOvfXQVHhK4PP
Yq23OYseIXVnsP7qlDMS/ZS+ptGBIXV2ZzqBt7I9jgMLC7f5i2NQwDns0720Slz1
MOIztq+Ccy8l31WlF5k40PlI6oy6PLv5RgM7v5CGr4RmGBZBiv2rQPYlfSSGvAQ+
Xn16CHji/70f9tEXfXGREJRzx/lIKFjz+JdROE4gptu/wXNjw6bTVTPx6FmfOhnD
8XUZA6oBjN14Hi3lLHzYlrhKQG+9owD4tsTcOcdIh7B8ZsMy2G8Mg0mWWHTWgTCC
Eu4GCSqGSIb3DQEHATAdBglghkgBZQMEAQIEEFmrLeGX3dF7SOczv6nMLxWAghLA
C3wQFKe2rnY/Rc4LgupEDeMq9p39XhDQIEYeYvcNiPuRC0ietAnYPfAegOQ1hsZh
Nd87LpWCtj736OkRwUXhQyoVEdr8YJRIBBgOYC56WyHutkdWAFsCXrHhJAeHdq4y
5XAdOPX9McvqKmdeDCfanXMWNs28G/sVIfwA1o6Tg4COw7g1DXVJhYqyZnX2tvDH
u5XM4EMVezY3F1dh7rs+NTNQ3ziFs/48dzIVPLmOZj/OX9o2pcnhzU2gyE2ciPtR
t8p/hWw2bdllp5+ZH4Ma/Cmaz+48GrRn3TgQzSw1/QtI+x6h6RBGSVTRo/nTEvWQ
t9SaoC1C+SxmEtHCPWtWLDnf979+I9ZGkqsrrjasoTKZAieq6KeTBB9Fya6eyyGj
VdDEx7jmKtpJpGvb0pBvl8xxWKD7hjX2f3qbgFKrwuToayXLXCw1hYnX3UQ4L7cH
t7h5T5m3pIehG8+HyNFOGvt1QaFTLzibQ1fgU8hdDQQkVhPDkPyCbLI3nFZ8HH9D
V5dxxd6O2t6oNeBJQUKMAzOxnfsygBhw89fobdskQnOPOBvl7PCSLrzGMvvE1WUq
wamSi94s7V6gFfUmbe7YYdZEl/VEEawzaw/eZ+wHbjVxQkpEZ388cFHMdHOnkhUG
SFobdwBYQj8vV4hxRTuoM9V7ZaV58S1MuS4Z86MUkCf2V9Z/9+XgkvmZMu/G+G7A
td574PqjRaFrOuLuEQHRRZgcgUP+5troXLRgcJJTYdZB6JKdfNg1ikBF6Bsl2Fv2
XxXU5o89L53X87Q6oyycSuZUUwhaVQbx4voWjnoR/Wcgo5bE9+moXhXHkFYOajDs
UAORrQGVC+NaaVwpQMQujvZUOYQJJaRiZc5kALd8TZ8c2W9s3j4L4pDDmQcrgBp7
BVdBnNDh7rNwFqrsp5Tt9lJkaA7A3JcMhTnxvWQCbe3e8jbgj5oFfR0vIZju7md/
NwT5rzrSVOAHpgUGEalM6u+zN5YU1Am9aisFYy9s0d1j6uzGTP++UfSI6mJPX5HZ
7HHVExQmVCjVgQwpifT8sOA8GBWUb9w5i3+BXhJroFJkgELcna6RHiRasndr5fdK
Gillmor, et al. Expires 26 May 2023 [Page 92]
Internet-Draft Header Protection S/MIME November 2022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, et al. Expires 26 May 2023 [Page 93]
Internet-Draft Header Protection S/MIME November 2022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.3.4. S/MIME encrypted and signed over a simple message, Wrapped
Message with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Wrapped Message header protection scheme with
the hcp_strong Header Confidentiality Policy.
It has the following structure:
Gillmor, et al. Expires 26 May 2023 [Page 94]
Internet-Draft Header Protection S/MIME November 2022
└─╴application/pkcs7-mime [smime.p7m] 7650 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4654 bytes
⇩ (unwraps to)
└┬╴message/rfc822 837 bytes
└─╴text/plain 319 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <73a42f8e-8f5a-5c62-b982-82ace766fd32@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:11:02 -0500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Gillmor, et al. Expires 26 May 2023 [Page 95]
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Gillmor, et al. Expires 26 May 2023 [Page 96]
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B.3.5. S/MIME encrypted and signed over a simple message, Injected
Headers with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_strong Header Confidentiality Policy.
Gillmor, et al. Expires 26 May 2023 [Page 97]
Internet-Draft Header Protection S/MIME November 2022
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7605 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4630 bytes
⇩ (unwraps to)
└─╴text/plain 331 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <27139e00-e05f-581d-a339-d2bd43bd0f42@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:12:02 -0500
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Internet-Draft Header Protection S/MIME November 2022
B.3.6. S/MIME encrypted and signed over a simple message, Injected
Headers with hcp_strong (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_strong Header Confidentiality Policy with a "Legacy Display"
part.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7845 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4806 bytes
⇩ (unwraps to)
└─╴text/plain 420 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <fdccb76a-49ed-50c5-9030-e4aeb83d7f04@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:13:02 -0500
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7O+E5GosuFO3VpWxchFXWSUziMnI3Rn9bjzK/xEHMgMe87ptvIp/J7dNwdHCYU2z
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B.3.7. S/MIME encrypted and signed reply over a simple message, Wrapped
Message with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Wrapped Message header protection scheme with
the hcp_minimal Header Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7735 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4712 bytes
⇩ (unwraps to)
└┬╴message/rfc822 879 bytes
└─╴text/plain 327 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <smime-enc-signed-wrapped-minimal-reply@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:14:02 -0500
User-Agent: Sample MUA Version 1.0
In-Reply-To: <smime-enc-signed-wrapped-minimal@lhp.example>
References: <smime-enc-signed-wrapped-minimal@lhp.example>
MIIWTAYJKoZIhvcNAQcDoIIWPTCCFjkCAQAxggMQMIIBhAIBADBsMFUxDTALBgNV
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bXBsZSBMQU1QUyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkCEzB8R0APhiY6
Gillmor, et al. Expires 26 May 2023 [Page 104]
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SgZ3YcbaJQWds1MpHiQ8cfpB5HuPRBJnLjetU+6CN+U1DwW89i/kgkiKp/LFFonX
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B.3.8. S/MIME encrypted and signed reply over a simple message,
Injected Headers with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_minimal Header Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7695 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4692 bytes
⇩ (unwraps to)
└─╴text/plain 339 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-injected-minimal-reply@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:15:02 -0500
User-Agent: Sample MUA Version 1.0
In-Reply-To: <smime-enc-signed-injected-minimal@lhp.example>
References: <smime-enc-signed-injected-minimal@lhp.example>
MIIWLAYJKoZIhvcNAQcDoIIWHTCCFhkCAQAxggMQMIIBhAIBADBsMFUxDTALBgNV
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Gillmor, et al. Expires 26 May 2023 [Page 107]
Internet-Draft Header Protection S/MIME November 2022
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Gillmor, et al. Expires 26 May 2023 [Page 108]
Internet-Draft Header Protection S/MIME November 2022
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Gillmor, et al. Expires 26 May 2023 [Page 109]
Internet-Draft Header Protection S/MIME November 2022
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KWZrv4qEgfqOMJHavYX2TQ==
B.3.9. S/MIME encrypted and signed reply over a simple message,
Injected Headers with hcp_minimal (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_minimal Header Confidentiality Policy with a "Legacy Display"
part.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7975 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4898 bytes
⇩ (unwraps to)
└─╴text/plain 435 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-injected-minimal-legacy-reply@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:16:02 -0500
Gillmor, et al. Expires 26 May 2023 [Page 110]
Internet-Draft Header Protection S/MIME November 2022
User-Agent: Sample MUA Version 1.0
In-Reply-To:
<smime-enc-signed-injected-minimal-legacy@lhp.example>
References:
<smime-enc-signed-injected-minimal-legacy@lhp.example>
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B.3.10. S/MIME encrypted and signed reply over a simple message,
Wrapped Message with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Wrapped Message header protection scheme with
the hcp_strong Header Confidentiality Policy.
It has the following structure:
Gillmor, et al. Expires 26 May 2023 [Page 113]
Internet-Draft Header Protection S/MIME November 2022
└─╴application/pkcs7-mime [smime.p7m] 7955 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4872 bytes
⇩ (unwraps to)
└┬╴message/rfc822 997 bytes
└─╴text/plain 325 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <0e210732-9184-5855-9a95-2a635560d3a6@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:17:02 -0500
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Internet-Draft Header Protection S/MIME November 2022
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Internet-Draft Header Protection S/MIME November 2022
B.3.11. S/MIME encrypted and signed reply over a simple message,
Injected Headers with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_strong Header Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 7930 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 4856 bytes
⇩ (unwraps to)
└─╴text/plain 337 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <0b3ea6dd-0e91-5a91-9bc0-3d553f892983@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:18:02 -0500
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WDVFDFDdjZUulonv0rmlz9i9fsK0tsDYcS4TDkimaDOKrGCtnxbxBzzUhEm8jN3W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9Ve8V2DvgTdgLrc3SHZn1BgtWwISf1jLRx3IWmB6kIRTKoqUND+Mh/bgblfnKy4o
OTPmg2hFLvY64mJEnWC5ATZUx8IN71dsKa18CyDCVWjaq99H+DMbBB+DWk15nbke
ZPwTyUM7CiHIlnpoMBu5Xc9H/2EtLsESNZ90tNbyQH1eCU/OaBM/5ivEZWE3VCnT
7VRke7s3JYbcBAkWMO1oRGj/s0HrPFR6ju7LHjZvWIjeZap1Zf4ldJpTyC6yRcs9
DjJIu9BUU1QE/t4uLOCPsCLlcmTzXtZpD+jV7+9wH8s+LZ0AE1GH+3FZyL9p3UA7
B.3.12. S/MIME encrypted and signed reply over a simple message,
Injected Headers with hcp_strong (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a text/plain
message. It uses the Injected Headers header protection scheme with
the hcp_strong Header Confidentiality Policy with a "Legacy Display"
part.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 8190 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 5058 bytes
⇩ (unwraps to)
└─╴text/plain 432 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <b10dcc75-cf43-5fd7-9e48-f932a9d68fb5@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 10:19:02 -0500
MIIXnAYJKoZIhvcNAQcDoIIXjTCCF4kCAQAxggMQMIIBhAIBADBsMFUxDTALBgNV
BAoTBElFVEYxETAPBgNVBAsTCExBTVBTIFdHMTEwLwYDVQQDEyhTYW1wbGUgTEFN
UFMgUlNBIENlcnRpZmljYXRpb24gQXV0aG9yaXR5AhMPLSW9ETmXSs5CVIeh7j00
Boq0MA0GCSqGSIb3DQEBAQUABIIBACIQq5gYVGjxS7N/umioYGQaBDzYuvtRP0wn
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drJZYTnB3yuCJmfeS9zonrI+CYksfA9NwkFJdyl9b0ILw7tVf2QFEqX/5tU+6o6b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snC6cKkTedQBfJ81GZT2ZmoX0dRLABvo/bu5k1h/5FtQibRcd/XGzIeeSSTsiCS4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qdmuO9Jg6DYckWE+MG83Q0gkoi5s+z9mZDtzPCIMU6wh8zwRXwAFVNCi2oNE6TMz
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CeSQ0YCTp/Yla4j80bPDB1eno5riUPDzR4UNsLpQ8Fms+qvJJk5e5rsA38Z6pOOi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ZNP1iYiohIvy59OyBzsz2mQR/ETCquOf82fJCXRxZ0wphAdXO2oy2o9Vky/njGFf
Fz3EStlH7Z7EoyLkj5d5F+74a+1hWzShS4mw3aX3LmsNq9f5MWC0TuwzxDvSGPU3
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5g0R+BohkWzBP1aIWhF+b56ZL3Afkpqw5q5LkXmHCuSlYA6yMhR7govC1uFoGJ2c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k2g7mTjU15dCOYWuXF/Ma9RiggjsR3fJ/KOu1IqAHkG402O8WF87Ku6wNZUy4bE2
QJYljwwnBwej2sMjSjLpr16fzvPm7hTx20Og4gMZB2qTPtL+VcQ8oPSVUWuEDuAV
Ds/pIMaQUr9EMPSqQumDXpzehQMe4FGaDUu0AF5ynuTacYKNd0am8QAA0mT+zB7S
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z8DQG/TMK/pRFOyAiFk1PtqiD/VYcUxPQmaPMx6Mu1VArGjkvedqIVJcTF1OsMIy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orVZheuE5q9klV0SauNu+JawzU9UZg69m5QnJ9b5fyAMtAFVVNVlmTzZsonY0ovj
KX6rj76Y4NcLjEKXwJzWDGJvZHv7D4KKgK+ptBpud1hAfmwlDWH3oFP2uelz/262
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cWgT2D+w/Nx4WQcz19h4LWYBecrUml8Wo53DQApeLJNMdUzNgeKKOFxs3an/y5/g
NEJT4p+kCpgQfSHJ8sKujf0X8/HHoaxfH3Vd/V2wZrYCVf5IxECQ2xyO1lorvU0w
YbK6euqf597puiFolZtRzOaSnuauUvVAQNthTwfOhUWswoUC/i+jaS9m/4GkIoUH
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dxg6Y2g/v8GUe8Z+RKoLGdjzavyu0AVgZ5O2eH+u2BalxfpQpbQtVFxZEFCeHDLZ
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eAlLLPLNjthzVWmnWF8bBew5sWsjlV5aw+Ly5tCC472KLLM+t2NcVB44OcBa/BSE
p/vh3TEsoZ/m+UfK8EGLqNVs2vPZhuVW9i19cN/5ALp497jj7Pdq/LY19x8VIrjV
EqbFPWIKeRDcBIvh4R1+0Z6nlHvILjv1NlNABnKqHwfjCQicvOaE7OlJ3QWWbBjC
dtOkxhC9+gBqDlq1YWgwbEzDPcFVzcCmTPH9wHhshcmp25O7lxqSxONeNcGMKy17
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Kyc5T3ReUPHrm8RIcaccjIwgxxyJ8YW3iCpH2s+vdaJnEC1Aa6D+53+0aCFg0/2g
asqTZ/iLws+bFux6MrNs8cohuvtF8Y6A/++cp40kp+PtSN8G7+g1CmkdZZdMg5u5
9J8s8SIrSbVj3y8eH/DSWGQ0gMc+NYLaWBXNReVPndwWP7aqXjLysuRAVVgOFvJa
zrwFU3JeUphCtGTht785hFePHTZ5IZBw+DAxvWHGX/5sIBokYH9E6l224r3ikUXU
DApjB42XlcYwo386TU6OUzfE8xHaJ7o+nW09t6sWy99M+BYngsu5ghjqIz7EAZjU
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BEB4pDKLcVf5tXVKSOSeIA/nauOxb8y+xve2ZkY8UARMwrtt7mqgqYgB6/gLD7Ah
Rw/Zs0+oQiNqv7XTY9clU/FfAQlRYiiz8o9fU783ccpsuw0PcgtnHWqyrw5I4vl4
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Eo8/ks2dfhjeiMfHkGl5aFybZAmd1f/sEtbUX5rCGkf0REfa17TC2NpB+OVSIJKI
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9uJU/KuVEk+cmUVwAbqWimq2XpY4TyopHyVjSFy7a8iaYs/sd+u2E2EEfXiyVra5
UsJmo/RdgZSCt0yLcYAKsO3gpXW1KSthrAUFYbSDlg7g5nQ9y2JyLsZGhjM+c1/I
6fEhOucX0MBaqMWpS31pMw8LUKSKOdiMXS+OlKzALyg3X1ObR1yK6PNK4XWs7L0+
a8nAdbRwoasr6SrenKYuTPkuRhLEkj0k+V4B7ilY8xGYuYjiZkxYxpZBwB8AM07m
ck4fGBGOOYdaGhraRy4DImP8SzVebtEj7i4wN7s+fHs3c8d7c6QuKOJhicyK6Hj+
spmo/oEd8vsvHieyu056IHduU4aeDkVoTYN2ks7itpuAv9wMOv6It2r4fob/aRSx
ExuZeT+RW/qnFpLDiUXa/z5VYZH32Ea6W/MUjoLc6VqzfGScE0FKJte+XiasJ8BG
yLuotJvLI5hCIz8gW8M4nSo8yly9VeyZ7Fn/DLsoJ32jQpYmhUjKjtNzqLcq6Wti
B.3.13. S/MIME encrypted and signed over a complex message, Wrapped
Message with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Wrapped Message header protection scheme with the hcp_minimal Header
Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 9600 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6090 bytes
⇩ (unwraps to)
└┬╴message/rfc822 1882 bytes
└┬╴multipart/mixed 1818 bytes
├┬╴multipart/alternative 1132 bytes
│├─╴text/plain 375 bytes
│└─╴text/html 473 bytes
└─╴image/png inline 232 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-complex-wrapped-minimal@lhp.example>
From: Alice <alice@smime.example>
Gillmor, et al. Expires 26 May 2023 [Page 123]
Internet-Draft Header Protection S/MIME November 2022
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:08:02 -0500
User-Agent: Sample MUA Version 1.0
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Gillmor, et al. Expires 26 May 2023 [Page 124]
Internet-Draft Header Protection S/MIME November 2022
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Gillmor, et al. Expires 26 May 2023 [Page 125]
Internet-Draft Header Protection S/MIME November 2022
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Gillmor, et al. Expires 26 May 2023 [Page 126]
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FjUpgcgUs/UWqVh2gpkU8qXkuUUZ+WSlEWje+FQVi7hp7fRlLHZvE06bZ7/elKOI
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1OCgq3zDr5wxrv+XNowoQn7P3nSnQYnqppc9VhVaKBU=
B.3.14. S/MIME encrypted and signed over a complex message, Injected
Headers with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_minimal Header
Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 9620 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6114 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 1848 bytes
├┬╴multipart/alternative 1136 bytes
│├─╴text/plain 387 bytes
│└─╴text/html 482 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-complex-injected-minimal@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:09:02 -0500
User-Agent: Sample MUA Version 1.0
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Gillmor, et al. Expires 26 May 2023 [Page 130]
Internet-Draft Header Protection S/MIME November 2022
B.3.15. S/MIME encrypted and signed over a complex message, Injected
Headers with hcp_minimal (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_minimal Header
Confidentiality Policy with a "Legacy Display" part.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 10205 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6548 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 2157 bytes
├┬╴multipart/alternative 1431 bytes
│├─╴text/plain 485 bytes
│└─╴text/html 637 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-complex-injected-minimal-legacy@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:10:02 -0500
User-Agent: Sample MUA Version 1.0
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Gillmor, et al. Expires 26 May 2023 [Page 132]
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Gillmor, et al. Expires 26 May 2023 [Page 134]
Internet-Draft Header Protection S/MIME November 2022
B.3.16. S/MIME encrypted and signed over a complex message, Wrapped
Message with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Wrapped Message header protection scheme with the hcp_strong Header
Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 9775 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6218 bytes
⇩ (unwraps to)
└┬╴message/rfc822 1975 bytes
└┬╴multipart/mixed 1911 bytes
├┬╴multipart/alternative 1128 bytes
│├─╴text/plain 373 bytes
│└─╴text/html 471 bytes
└─╴image/png inline 232 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <95b9bb39-c028-5ff4-99b1-f179cb5d7585@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:11:02 -0500
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Gillmor, et al. Expires 26 May 2023 [Page 136]
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Gillmor, et al. Expires 26 May 2023 [Page 137]
Internet-Draft Header Protection S/MIME November 2022
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Gillmor, et al. Expires 26 May 2023 [Page 138]
Internet-Draft Header Protection S/MIME November 2022
B.3.17. S/MIME encrypted and signed over a complex message, Injected
Headers with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_strong Header
Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 9795 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6246 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 1941 bytes
├┬╴multipart/alternative 1132 bytes
│├─╴text/plain 385 bytes
│└─╴text/html 480 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <23abef5f-8781-5c95-a46c-61e3a4464d58@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:12:02 -0500
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Gillmor, et al. Expires 26 May 2023 [Page 141]
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B.3.18. S/MIME encrypted and signed over a complex message, Injected
Headers with hcp_strong (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_strong Header
Confidentiality Policy with a "Legacy Display" part.
Gillmor, et al. Expires 26 May 2023 [Page 142]
Internet-Draft Header Protection S/MIME November 2022
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 10380 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6676 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 2248 bytes
├┬╴multipart/alternative 1425 bytes
│├─╴text/plain 482 bytes
│└─╴text/html 634 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <9cfcaae2-9fec-5aca-9a29-c98da35b262d@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:13:02 -0500
MIId7AYJKoZIhvcNAQcDoIId3TCCHdkCAQAxggMQMIIBhAIBADBsMFUxDTALBgNV
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B.3.19. S/MIME encrypted and signed reply over a complex message,
Wrapped Message with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Wrapped Message header protection scheme with the hcp_minimal Header
Confidentiality Policy.
Gillmor, et al. Expires 26 May 2023 [Page 146]
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It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 9880 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6308 bytes
⇩ (unwraps to)
└┬╴message/rfc822 2041 bytes
└┬╴multipart/mixed 1977 bytes
├┬╴multipart/alternative 1144 bytes
│├─╴text/plain 381 bytes
│└─╴text/html 479 bytes
└─╴image/png inline 232 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-complex-wrapped-minimal-reply@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:14:02 -0500
User-Agent: Sample MUA Version 1.0
In-Reply-To:
<smime-enc-signed-complex-wrapped-minimal@lhp.example>
References:
<smime-enc-signed-complex-wrapped-minimal@lhp.example>
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Gillmor, et al. Expires 26 May 2023 [Page 148]
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Gillmor, et al. Expires 26 May 2023 [Page 149]
Internet-Draft Header Protection S/MIME November 2022
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B.3.20. S/MIME encrypted and signed reply over a complex message,
Injected Headers with hcp_minimal
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_minimal Header
Confidentiality Policy.
Gillmor, et al. Expires 26 May 2023 [Page 150]
Internet-Draft Header Protection S/MIME November 2022
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 9925 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6342 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 2009 bytes
├┬╴multipart/alternative 1148 bytes
│├─╴text/plain 393 bytes
│└─╴text/html 488 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-complex-injected-minimal-reply@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:15:02 -0500
User-Agent: Sample MUA Version 1.0
In-Reply-To:
<smime-enc-signed-complex-injected-minimal@lhp.example>
References:
<smime-enc-signed-complex-injected-minimal@lhp.example>
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Gillmor, et al. Expires 26 May 2023 [Page 152]
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Gillmor, et al. Expires 26 May 2023 [Page 153]
Internet-Draft Header Protection S/MIME November 2022
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B.3.21. S/MIME encrypted and signed reply over a complex message,
Injected Headers with hcp_minimal (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_minimal Header
Confidentiality Policy with a "Legacy Display" part.
Gillmor, et al. Expires 26 May 2023 [Page 154]
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It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 10510 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6766 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 2314 bytes
├┬╴multipart/alternative 1435 bytes
│├─╴text/plain 487 bytes
│└─╴text/html 639 bytes
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smime-type="enveloped-data"
Subject: [...]
Message-ID:
<smime-enc-signed-complex-injected-minimal-lgc-rpl@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:16:02 -0500
User-Agent: Sample MUA Version 1.0
In-Reply-To:
<smime-enc-signed-complex-injected-minimal-legacy@lhp.example>
References:
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B.3.22. S/MIME encrypted and signed reply over a complex message,
Wrapped Message with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Wrapped Message header protection scheme with the hcp_strong Header
Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 10100 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6468 bytes
⇩ (unwraps to)
└┬╴message/rfc822 2157 bytes
└┬╴multipart/mixed 2093 bytes
├┬╴multipart/alternative 1140 bytes
│├─╴text/plain 379 bytes
│└─╴text/html 477 bytes
└─╴image/png inline 232 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <38a0b7ba-76e0-5351-93e9-f44877e20e6e@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:17:02 -0500
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Internet-Draft Header Protection S/MIME November 2022
B.3.23. S/MIME encrypted and signed reply over a complex message,
Injected Headers with hcp_strong
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_strong Header
Confidentiality Policy.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 10140 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6502 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 2125 bytes
├┬╴multipart/alternative 1144 bytes
│├─╴text/plain 391 bytes
│└─╴text/html 486 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <c6774fdb-3ef5-5293-ab2d-eca8b66b4bbf@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:18:02 -0500
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Internet-Draft Header Protection S/MIME November 2022
B.3.24. S/MIME encrypted and signed reply over a complex message,
Injected Headers with hcp_strong (+ Legacy Display)
This is a encrypted and signed S/MIME message using PKCS#7
envelopedData around signedData. The payload is a multipart/
alternative message with an inline image/png attachment. It uses the
Injected Headers header protection scheme with the hcp_strong Header
Confidentiality Policy with a "Legacy Display" part.
It has the following structure:
└─╴application/pkcs7-mime [smime.p7m] 10790 bytes
↧ (decrypts to)
└─╴application/pkcs7-mime [smime.p7m] 6968 bytes
⇩ (unwraps to)
└┬╴multipart/mixed 2460 bytes
├┬╴multipart/alternative 1449 bytes
│├─╴text/plain 494 bytes
│└─╴text/html 646 bytes
└─╴image/png inline 236 bytes
Its contents are:
Content-Transfer-Encoding: base64
Content-Type: application/pkcs7-mime; name="smime.p7m";
smime-type="enveloped-data"
Subject: [...]
Message-ID: <acced3c9-111b-5a4f-bd80-34558da32b4d@lhp.example>
From: Alice <alice@smime.example>
To: Bob <bob@smime.example>
Date: Sat, 20 Feb 2021 12:19:02 -0500
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/31+cHHBVIWzPBpbq8am8Ct2Ha1SRcOV3gFlU9jg3Us1pYdX7p0gqaQRgJOumcCu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gsaJ9xT2a4TxezWjBUQInTcv9dRcDXidNt3py3F1jBqx9MkTnEbrYKOXZ1wk71fS
FZQ7IcPrdKjwY7id5j9ABHQfQWy8bRECh3woq42JisX17wmBXlmtjmeaPUkZynKA
taPBG5IM5jRqxHntADcWQRXg5UBB/ssj2ziyd8xSpIZnikMcJQUZAlOWprCXm1kC
LBYanEAhce71K/o79v13de+Ynox5v0smvsMF9RU7+90Yzx/2dWzbMSwh4+IDoAZ3
fYUFootr14wPHVA4z34Vuyc30BR7UMv3JvIXmU8awdENHUf9yVGOTbMhu2MOkp5O
9//u36yzJCV9X6CcF8I1NrDaoS7OSzt5kWvMm3t3nGZAibf12ZGdeVK0+ypaIcVA
Appendix C. Additional information
C.1. Stored Variants of Messages with Bcc
Messages containing at least one recipient address in the Bcc header
field may appear in up to three different variants:
1. The Message for the recipient addresses listed in To or Cc header
fields, which must not include the Bcc header field neither for
signature calculation nor for encryption.
2. The Message(s) sent to the recipient addresses in the Bcc header
field, which depends on the implementation:
a) One Message for each recipient in the Bcc header field
separately, with a Bcc header field containing only the address
of the recipient it is sent to.
b) The same Message for each recipient in the Bcc header field
with a Bcc header field containing an indication such as
"Undisclosed recipients", but no addresses.
c) The same Message for each recipient in the Bcc header field
which does not include a Bcc header field (this Message is
identical to 1. / see above).
3. The Message stored in the 'Sent'-Folder of the sender, which
usually contains the Bcc unchanged from the original Message,
i.e., with all recipient addresses.
The most privacy preserving method of the alternatives (2a, 2b, and
2c) is to standardize 2a, as in the other cases (2b and 2c),
information about hidden recipients is revealed via keys. In any
case, the Message has to be cloned and adjusted depending on the
recipient.
Appendix D. Examples
This section offers example cryptographic payloads (the content
within the cryptographic envelope) that contain Legacy Display
elements.
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D.1. Example text/plain Cryptographic Payload with Legacy Display
Elements
Here is a simple one-part Cryptographic Payload (headers and body) of
a message that includes Legacy Display elements:
Date: Fri, 21 Jan 2022 20:40:48 -0500
From: Alice <alice@example.net>
To: Bob <bob@example.net>
Subject: Dinner plans
Message-ID: <text-plain-legacy-display@lhp.example>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; hp-legacy-display="1";
protected-headers="v1"
Subject: Dinner plans
Let's meet at Rama's Roti Shop at 8pm and go to the park
from there.
A compatible MUA will recognize the hp-legacy-display="1" parameter
and render the body of the message as:
Let's meet at Rama's Roti Shop at 8pm and go to the park
from there.
A legacy decryption-capable MUA that is unaware of this mechanism
will ignore the hp-legacy-display="1" parameter and instead render
the body including the Legacy Display elements:
Subject: Dinner plans
Let's meet at Rama's Roti Shop at 8pm and go to the park
from there.
D.2. Example text/html Cryptographic Payload with Legacy Display
Elements
Here is a modern one-part Cryptographic Payload (headers and body) of
a message that includes Legacy Display elements:
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Date: Fri, 21 Jan 2022 20:40:48 -0500
From: Alice <alice@example.net>
To: Bob <bob@example.net>
Subject: Dinner plans
Message-ID: <text-html-legacy-display@lhp.example>
MIME-Version: 1.0
Content-Type: text/html; charset="us-ascii"; hp-legacy-display="1";
protected-headers="v1"
<html><head><title></title></head><body>
<div class="header-protection-legacy-display">
<pre>Subject: Dinner plans</pre>
</div>
<p>
Let's meet at Rama's Roti Shop at 8pm and go to the park
from there.
</p>
</body>
</html>
A compatible MUA will recognize the hp-legacy-display="1" parameter
and mask out the Legacy Display div, rendering the body of the
message as a simple paragraph:
Let's meet at Rama's Roti Shop at 8pm and go to the park
from there.
A legacy decryption-capable MUA that is unaware of this mechanism
will ignore the hp-legacy-display="1" parameter and instead render
the body including the Legacy Display elements:
Subject: Dinner plans
Let's meet at Rama's Roti Shop at 8pm and go to the park
from there.
Appendix E. Document Changelog
[[ RFC Editor: This section is to be removed before publication ]]
* draft-ietf-lamps-header-protection-09
- clarify terminology
- add privacy and security considerations
- clarify HCP examples and baselines
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- recommend hcp_minimal as default HCP
- add HP-Obscured and HP-Removed (avoids reasoning about
differences between outside and inside the cryptographic
envelope)
- regenerated test vectors
* draft-ietf-lamps-header-protection-08
- MUST compose injected headers, MAY compose wrapped messages
- MUST parse both schemes
- cleanup and restructure document
* draft-ietf-lamps-header-protection-07
- move from legacy display MIME part to legacy display elements
within main body part
* draft-ietf-lamps-header-protection-06
- document observed problems with legacy MUAs
- avoid duplicated outer Message-IDs in hcp_strong test vectors
* draft-ietf-lamps-header-protection-05
- fix multipart/signed wrapped test vectors
* draft-ietf-lamps-header-protection-04
- add test vectors
- add "problems with Injected Messages" subsection
* draft-ietf-lamps-header-protection-03
- dkg takes over from Bernie as primary author
- Add Usability section
- describe two distinct formats "Wrapped Message" and "Injected
Headers"
- Introduce Header Confidentiality Policy model
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- Overhaul message composition guidance
- Simplify document creation workflow, move public face to gitlab
* draft-ietf-lamps-header-protection-02
- editorial changes / improve language
* draft-ietf-lamps-header-protection-01
- Add DKG as co-author
- Partial Rewrite of Abstract and Introduction [HB/AM/DKG]
- Adding definitions for Cryptographic Layer, Cryptographic
Payload, and Cryptographic Envelope (reference to
[I-D.ietf-lamps-e2e-mail-guidance]) [DKG]
- Enhanced MITM Definition to include Machine- / Meddler-in-the-
middle [HB]
- Relaxed definition of Original message, which may not be of
type "message/rfc822" [HB]
- Move "memory hole" option to the Appendix (on request by Chair
to only maintain one option in the specification) [HB]
- Updated Scope of Protection Levels according to WG discussion
during IETF-108 [HB]
- Obfuscation recommendation only for Subject and Message-Id and
distinguish between Encrypted and Unencrypted Messages [HB]
- Removed (commented out) Header Field Flow Figure (it appeared
to be confusing as is was) [HB]
* draft-ietf-lamps-header-protection-00
- Initial version (text partially taken over from
[I-D.ietf-lamps-header-protection-requirements]
Appendix F. Open Issues
[[ RFC Editor: This section should be empty and is to be removed
before publication. ]]
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* Ensure "protected header" (Ex-Memory-Hole) option is (fully)
compliant with the MIME standard, in particular also [RFC2046],
Section 5.1. (Multipart Media Type).
* Decide on whether or not merge requirements from
[I-D.ietf-lamps-header-protection-requirements] into this
document.
* Decide on whether or not specification for more legacy HP
requirements should be added to this document.
* Verify ability to distinguish between Messages with Header
Protection as specified in this document and messages without
header protection, and update receiving guidance accordingly.
* Privacy Considerations Section 6
* Security Considerations Section 5
Authors' Addresses
Daniel Kahn Gillmor
American Civil Liberties Union
125 Broad St.
New York, NY, 10004
United States of America
Email: dkg@fifthhorseman.net
Bernie Hoeneisen
pEp Foundation
Oberer Graben 4
CH- CH-8400 Winterthur
Switzerland
Email: bernie.hoeneisen@pep.foundation
URI: https://pep.foundation/
Alexey Melnikov
Isode Ltd
14 Castle Mews
Hampton, Middlesex
TW12 2NP
United Kingdom
Email: alexey.melnikov@isode.com
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