Authentication-Results Registration for TLS
draft-martin-authentication-results-tls-00
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| Last updated | 2014-03-02 | ||
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draft-martin-authentication-results-tls-00
Network Working Group F. Martin, Ed.
Internet-Draft LinkedIn
Updates: 7001 (if approved) March 03, 2014
Intended status: Standards Track
Expires: September 04, 2014
Authentication-Results Registration for TLS
draft-martin-authentication-results-tls-00
Abstract
This memo updates the registry of properties in Authentication-
Results: message header fields to allow relaying of the results of an
email sent using STARTTLS [RFC3207] or not.
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 September 04, 2014.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Discussion . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. results meaning . . . . . . . . . . . . . . . . . . . . . 3
2.2. properties . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Authentication-Results Examples . . . . . . . . . . 6
A.1. TLS Results . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
STARTTLS [RFC3207] defines how to send an email over an SMTP
[RFC5321] encrypted session between two mail servers.
This memo thus registers an additional reporting property allowing a
TLS result to be relayed as an annotation in a message header.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
1.2. Discussion
STARTTLS [RFC3207] defines how to send an email over an encrypted
session between two mail servers, Message Transfer Agent (MTA), using
the TLS [RFC5246] protocol.
Most of these exchanges are opportunistic, meaning, a best effort is
done to establish an encrypted message exchange regardless of the
strength of the cipher or the validy of the certificates used.
However, the results of this negotiation should be recorded in the
message via the Authentication-Results header [RFC7001] to indicate
to other message processing algorithms, including Messaging User
Agents (MUA), how securely this message was transmitted from the MTA
client to the MTA server.
2. Definitions
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This memo adds to the "Email Authentication Methods" registry,
created by IANA upon publication of [RFC7001], the following:
o The method "tls"; and
o Associated with that method, the properties (reporting items)
"cert.client", "cert.server", "cert.cipher" and "cert.strength".
2.1. results meaning
The "tls" method can have the following results:
none: the message was sent in clear.
pass: the message was sent encrypted and the client certificate was
verified valid.
fail: the message was sent encrypted but the client certificate is
not valid. It is advised to use comments to indicate the nature of
the problem like certifcate expired, not linked to a trusted CA,...
temperror: the message was sent encrypted and the server was not able
to verify the client certificate at this time. This may indicate for
instance that the server could not fetch the CRL.
permerror: the message was sent encrypted and the client certificate
was not verified by the MTA server.
2.2. properties
cert.client: the subject of the X.509 certificate used by the client
to initiate TLS.
cert.server: the subject of the X.509 certificate used by the server
to initiate TLS (optional).
key.cipher: the description of the TLS cipher suite used as defined
in the IANA cipher suite registry.
key.strength: as many SMTP TLS are opportunistic in nature this
property is an arbitrary value set by the MTA server to indicate the
stength of the encryption.
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3. IANA Considerations
Per [IANA], the following items have been added to the "Email
Authentication Methods" registry:
+------------+----------+--------+----------------+-----------------+
| Method | Defined | ptype | property | value |
+------------+----------+--------+----------------+-----------------+
| tls | RFC 3207 | cert | client | subject of |
| | | | | client |
| | | | | certificate |
| | | | | section 4.1.26 |
| | | | | of RFC 5280 |
+------------+----------+--------+----------------+-----------------+
| tls | RFC 3207 | cert | server | subject of |
| | | | | server |
| | | | | certificate |
| | | | | section 4.1.26 |
| | | | | of RFC 5280 |
+------------+----------+--------+----------------+-----------------+
| tls | RFC 3207 | key | cipher | IANA cipher |
| | | | | suite registry |
| | | | | description |
| | | | | from RFC 5246 |
+------------+----------+--------+----------------+-----------------+
| tls | RFC 3207 | key | strength | low |
| | | | | medium |
| | | | | high |
| | | | | |
+------------+----------+--------+----------------+-----------------+
Also, the following items have been added to the "Email
Authentication Result Names" registry:
+-----------+--------------+------------+---------+-----------------+
| Code | Existing/New | Defined In | Method | Meaning |
+-----------+--------------+------------+---------+-----------------+
| none | existing | RFC 7001 | tls | this memo |
| | | | (added) | |
+-----------+--------------+------------+---------+-----------------+
| pass | existing | RFC 7001 | tls | this memo |
| | | | (added) | |
+-----------+--------------+------------+---------+-----------------+
| fail | existing | RFC 7001 | tls | this memo |
| | | | (added) | |
+-----------+--------------+------------+---------+-----------------+
| temperror | existing | RFC 7001 | tls | this memo |
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| | | | (added) | |
+-----------+--------------+------------+---------+-----------------+
| permerror | existing | RFC 7001 | tls | this memo |
| | | | (added) | |
+-----------+--------------+------------+---------+-----------------+
4. Security Considerations
This memo creates a mechanism for relaying STARTTLS [RFC3207] results
using the structure already defined by [RFC7001]. The Security
Considerations sections of those documents should be consulted.
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3207] Hoffman, P., "SMTP Service Extension for Secure SMTP over
Transport Layer Security", RFC 3207, February 2002.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
[RFC7001] Kucherawy, M., "Message Header Field for Indicating
Message Authentication Status", RFC 7001, September 2013.
5.2. Informative References
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
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Appendix A. Authentication-Results Examples
This section presents an example of the use of this new header field
to indicate TLS results.
A.1. TLS Results
A message that went over a successful TLS session:
Authentication-Results: mail-router.example.net;
dkim=pass (good signature) header.d=newyork.example.com
header.b=oINEO8hg;
tls=pass (verified, expires 20140505)
tls.client="/C=US/ST=CA/L=ToonTown/O=ACME/CN=smtp.example.com"
tls.cipher=TLS_RSA_WITH_RC4_128_SHA
tls.strength=medium;
Received: from newyork.example.com
(newyork.example.com [192.0.2.250])
by mail-router.example.net (8.11.6/8.11.6)
for <recipient@example.net>
with ESMTPS id i7PK0sH7021929;
Fri, Feb 15 2002 17:19:22 -0800
DKIM-Signature: v=1; a=rsa-sha256; s=rashani;
d=newyork.example.com;
t=1188964191; c=relaxed/simple;
h=From:Date:To:VBR-Info:Message-Id:Subject;
bh=sEu28nfs9fuZGD/pSr7ANysbY3jtdaQ3Xv9xPQtS0m7=;
b=oINEO8hgn/gnunsg ... 9n9ODSNFSDij3=
From: sender@newyork.example.com
Date: Fri, Feb 15 2002 16:54:30 -0800
To: meetings@example.net
Message-Id: <12345.abc@newyork.example.com>
Subject: here's a sample
Author's Address
Franck Martin (editor)
LinkedIn
Mountain View, CA
US
Email: fmartin@linkedin.com
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