S/MIME signature verification extension to JMAP
draft-ietf-jmap-smime-09
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (jmap WG) | |
|---|---|---|---|
| Author | Alexey Melnikov | ||
| Last updated | 2021-10-21 (Latest revision 2021-09-30) | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html xml htmlized pdfized bibtex | ||
| Reviews |
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| Stream | WG state | Submitted to IESG for Publication | |
| Associated WG milestone |
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| Document shepherd | Bron Gondwana | ||
| Shepherd write-up | Show Last changed 2021-08-19 | ||
| IESG | IESG state | Approved-announcement to be sent::Revised I-D Needed | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Murray Kucherawy | ||
| Send notices to | brong@fastmailteam.com | ||
| IANA | IANA review state | IANA OK - Actions Needed | |
| IANA expert review state | Expert Reviews OK |
draft-ietf-jmap-smime-09
Network Working Group A. Melnikov
Internet-Draft Isode Ltd
Intended status: Standards Track 30 September 2021
Expires: 3 April 2022
S/MIME signature verification extension to JMAP
draft-ietf-jmap-smime-09
Abstract
This document specifies an extension to JMAP for Mail (RFC 8621) for
returning S/MIME signature verification status.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 3 April 2022.
Copyright Notice
Copyright (c) 2021 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
and restrictions with respect to this document. Code Components
extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. Addition to the capabilities object . . . . . . . . . . . . . 3
4. Extension for S/MIME signature verification . . . . . . . . . 3
4.1. Extension to Email/get . . . . . . . . . . . . . . . . . 3
4.2. Extension to Email/query . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5.1. JMAP capability registration for "smimeverify" . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
JMAP for Mail [RFC8621] is a JSON based application protocol for
synchronising email data between a client and a server.
This document describes an extension to JMAP for returning S/MIME
[RFC8551] signature verification status, without requiring a JMAP
client to download the signature body part and all signed body parts
(when the multipart/signed media type [RFC1847] is used) or to
download and decode CMS (when the application/pkcs7-mime media type
(Section 3.2 of [RFC8551]) is used). The use of the extension
implies the client trusts the JMAP server's S/MIME signature
verification code and configuration. This extension is suitable for
cases where reduction in network bandwidth and client side code
complexity outweigh security concerns about trusting JMAP server to
perform S/MIME signature verifications. One possible use case is
when the same organization controls both the JMAP server and the JMAP
client.
2. Conventions Used in This Document
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.
Type signatures, examples, and property descriptions in this document
follow the conventions established in Section 1.1 of [RFC8620]. Data
types defined in the core specification are also used in this
document.
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3. Addition to the capabilities object
The capabilities object is returned as part of the standard JMAP
Session object; see Section 2 of [RFC8620]. Servers supporting
_this_ specification MUST add a property called
"urn:ietf:params:jmap:smimeverify" to the capabilities object.
The value of this property is an empty object in both the JMAP
session _capabilities_ property and an account's
_accountCapabilities_ property.
4. Extension for S/MIME signature verification
4.1. Extension to Email/get
[RFC8621] defines the Email/get method for retrieving message
specific information. This document defines the following pseudo
values in the _properties_ argument:
* *smimeStatus*: If "smimeStatus" is included in the list of
requested properties, it MUST be interpreted by the server as a
request to return the "smimeStatus" response property.
* *smimeStatusAtDelivery*: If "smimeStatusAtDelivery" is included in
the list of requested properties, it MUST be interpreted by the
server as a request to return the "smimeStatusAtDelivery" response
property. (It is effectively the same as the "smimeStatus" value
calculated at the date/time of delivery, as specified by
"receivedAt".)
* *smimeErrors*: If "smimeErrors" is included in the list of
requested properties, it MUST be interpreted by the server as a
request to return the "smimeErrors" response property.
* *smimeVerifiedAt*: If "smimeVerifiedAt" is included in the list of
requested properties, it MUST be interpreted by the server as a
request to return the "smimeVerifiedAt" response property.
The "smimeStatus" response property is defined as follows:
smimeStatus: "String|null". null signifies that the message doesn't
contain any signature. Otherwise, this property contains the S/MIME
signature and certificate verification status calculated according to
[RFC8551] and [RFC8550]. Possible string values of the property are
listed below. Servers MAY return other values not defined below, as
defined in extensions to this document. All values (defined below or
in extensions to this document) MUST be in ASCII. (Note that this
response property contains tokens, thus it is not subject to
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Internationalization or Localization). Clients MUST treat
unrecognized values as "unknown" or "signed/failed". Note that the
value of this property might change over time.
unknown: S/MIME message, but it was neither signed nor encrypted.
This can also be returned for a multipart/signed message which
contains an unrecognized signing protocol (for example OpenPGP).
signed: S/MIME signed message, but the signature was not yet
verified. Some servers might not attempt to verify a signature
until a particular message is requested by the client. JMAP
servers compliant with this document SHOULD return "signed/
verified" or "signed/failed" instead of this signature status.
signed/verified: S/MIME signed message and the sender's signature
was successfully verified, the sender matches the From header
field, and the sender's certificate (and the certificate chain) is
trusted for signing.
signed/failed: S/MIME signed message, but the signature failed to
verify. This might be a policy related decision (message signer
doesn't match the From header field), message was modified, the
signer's certificate has expired or was revoked, etc.
The "smimeStatusAtDelivery" response property has the same syntax as
"smimeStatus" but is calculated at the "receivedAt" date/time.
Unlike "smimeStatus", the "smimeStatusAtDelivery" response property
value is immutable. "smimeStatusAtDelivery" allows clients to compare
the S/MIME signature verification status at delivery with the current
status as returned by "smimeStatus", for example to help to answer
questions like "was the signature valid at the time of delivery?".
The "smimeErrors" response property is defined as follows:
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smimeErrors: "String[]|null". null signifies that the message doesn't
contain any signature or that there were no errors when verifying the
S/MIME signature. (I.e., this property is non null only when the
corresponding "smimeStatus" response property value is "signed/
failed".) Each string in the array is a human readable description
(in the language specified in the Content-Language header field, if
any) of a problem with the signature, the signing certificate or the
signing certificate chain. (See Section 3.8 of [RFC8620] in regards
to how this is affected by the language selection.) In one example,
the signing certificate might be expired and the message From email
address might not correspond to any of the email addresses in the
signing certificate. In another example the certificate might be
expired and the JMAP server might be unable to retrieve a CRL for the
certificate. In both of these cases there would be 2 elements in the
array.
The "smimeVerifiedAt" response property is defined as follows:
smimeVerifiedAt: "UTCDate|null" (server-set). null signifies that the
message doesn't contain any S/MIME signature or that there is a
signature, but there was no attempt to verify it. In all other cases
it is set to the date and time of when the S/MIME signature was most
recently verified. Note that a request to fetch "smimeStatus" and/or
"smimeErrors" would force this response property to be set to a non
null value, if an S/MIME signature exists.
"smimeStatus" and "smimeErrors" values are calculated at the time the
corresponding JMAP request was processed (but see below about result
caching), not at the time when the message was generated (according
to its Date header field value). In all cases "smimeVerifiedAt" is
set to the time when "smimeStatus" and "smimeErrors" were last
updated. As recalculating these values is expensive for the server,
they MAY be cached for up to 10 minutes from the moment when they
were calculated.
Example 1: Retrieval of minimal information about a message,
including its From, Subject and Date header fields, as well as S/MIME
signature verification status at delivery and date/time when the
message was received.
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["Email/get", {
"ids": [ "f123u457" ],
"properties": [ "mailboxIds", "from", "subject", "date",
"smimeStatusAtDelivery", "receivedAt" ]
}, "#1"]
This might result in the following response:
[["Email/get", {
"accountId": "abc",
"state": "41234123231",
"list": [
{
"id": "f123u457",
"mailboxIds": { "f123": true },
"from": [{"name": "Joe Bloggs", "email": "joe@bloggs.example.net"}],
"subject": "Dinner tonight?",
"date": "2020-07-07T14:12:00Z",
"smimeStatusAtDelivery": "signed/verified",
"receivedAt": "2020-07-07T14:15:18Z"
}
]
}, "#1"]]
Example 2: Retrieval of minimal information about a message,
including its From, Subject and Date header fields, as well as the
latest S/MIME signature verification status, S/MIME verification
errors (if any) and when was the S/MIME signature status last
verified. The response contains 2 S/MIME errors related to S/MIME
signature verification.
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["Email/get", {
"ids": [ "af123u123" ],
"properties": [ "mailboxIds", "from", "subject", "date",
"smimeStatus", "smimeErrors", "smimeVerifiedAt" ]
}, "#1"]
This might result in the following response:
[["Email/get", {
"accountId": "abc",
"state": "41234123231",
"list": [
{
"id": "af123u123",
"mailboxIds": { "f123": true },
"from": [{"name": "Jane Doe",
"email": "jdoe@example.com"}],
"subject": "Company takeover",
"date": "2020-01-31T23:00:00Z",
"smimeStatus": "signed/failed",
"smimeErrors": [
"From email address doesn't match the certificate",
"Can't retrieve CRL from the CRL URL"],
"smimeVerifiedAt": "2020-03-01T12:11:19Z"
}
]
}, "#1"]]
4.2. Extension to Email/query
[RFC8621] defines the Email/query method for searching for messages
with specific properties. This document defines the following
properties of the *FilterCondition* object:
* *hasSmime*: "Boolean". If "hasSmime" has the value true, only
messages with "smimeStatus" other than null match the condition.
If "hasSmime" has the value false, only messages with
"smimeStatus" equal to null match the condition.
* *hasVerifiedSmime*: "Boolean". If "hasVerifiedSmime" has the
value true, only messages with "smimeStatus" equal to "signed/
verified" match the condition. If "hasVerifiedSmime" has the
value false, only messages with "smimeStatus" not equal to
"signed/verified" (including the value null) match the condition.
5. IANA Considerations
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5.1. JMAP capability registration for "smimeverify"
IANA is requested to register the "smimeverify" JMAP Capability as
follows:
Capability Name: "urn:ietf:params:jmap:smimeverify"
Specification document: this document
Intended use: common
Change Controller: IETF
Security and privacy considerations: this document, Section 6
6. Security Considerations
Use of server-side S/MIME signature verification JMAP extension
requires the client to trust the server signature verification code
and configuration to perform S/MIME signature verification. For
example, if the server is not configured with some Trust Anchors,
some messages will have "signed/failed" status instead of "signed/
verified".
Constant recalculation of S/MIME signature status can result in a
Denial-of-Service condition. For that reason, it is RECOMMENDED to
cache results of signature verification for 10 minutes.
7. References
7.1. Normative References
[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>.
[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>.
[RFC8550] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Certificate Handling", RFC 8550, DOI 10.17487/RFC8550,
April 2019, <https://www.rfc-editor.org/info/rfc8550>.
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[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>.
[RFC8620] Jenkins, N. and C. Newman, "The JSON Meta Application
Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July
2019, <https://www.rfc-editor.org/info/rfc8620>.
[RFC8621] Jenkins, N. and C. Newman, "The JSON Meta Application
Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621,
August 2019, <https://www.rfc-editor.org/info/rfc8621>.
7.2. Informative References
[RFC1847] Galvin, J., Murphy, S., Crocker, S., and N. Freed,
"Security Multiparts for MIME: Multipart/Signed and
Multipart/Encrypted", RFC 1847, DOI 10.17487/RFC1847,
October 1995, <https://www.rfc-editor.org/info/rfc1847>.
Appendix A. Acknowledgements
This document is a product of JMAP Working Group. Special thank you
to Bron Gondwana, Neil Jenkins, Murray Kucherawy, Kirsty Paine and
Peter Yee for suggestions, comments and corrections to this document.
Author's Address
Alexey Melnikov
Isode Ltd
14 Castle Mews
Hampton
TW12 2NP
United Kingdom
Email: Alexey.Melnikov@isode.com
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