Network Working Group A. Melnikov Internet-Draft Isode Ltd Intended status: Standards Track October 11, 2013 Expires: April 14, 2014 Authentication-Results Registration for S/MIME signature verification draft-melnikov-authentication-results-smime-03 Abstract RFC 7001 specifies the Authentication-Results header field for conveying results of message authentication checks. This document defines a new authentication method to be used in the Authentication- Results header field for S/MIME related signature checks. 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Melnikov Expires April 14, 2014 [Page 1] Internet-DrafAuthentication-Results Registration for S/MIME October 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions Used in This Document . . . . . . . . . . . . . . 2 3. "smime" Authentication Method . . . . . . . . . . . . . . . . 2 3.1. S/MIME Results . . . . . . . . . . . . . . . . . . . . . 2 3.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References . . . . . . . . . . . . . . . . . . 6 6.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 7 1. Introduction [RFC7001] specifies the Authentication-Results header field for conveying results of message authentication checks. As S/MIME signature verification (and alteration) is sometimes implemented in border message transfer agents, guards and gateways (for example see [RFC3183]), there is a need to convey signature verification status to Mail User Agents (MUA) and downstream filters. This document defines a new authentication method to be used in the Authentication- Results header field for S/MIME related signature checks. 2. Conventions Used in This Document 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 [RFC2119]. The formal syntax uses the Augmented Backus-Naur Form (ABNF) [RFC5234] notation including the core rules defined in Appendix B of RFC 5234 [RFC5234]. 3. "smime" Authentication Method 3.1. S/MIME Results The result values used by [RFC5751] are as follows: +-------------+-----------------------------------------------------+ | Result code | Meaning | +-------------+-----------------------------------------------------+ | none | The message was not signed. | | | | | pass | The message was signed, the signature or signatures | | | were acceptable to the verifier, and the | Melnikov Expires April 14, 2014 [Page 2] Internet-DrafAuthentication-Results Registration for S/MIME October 2013 | | signature(s) passed verification tests. | | | | | fail | The message was signed and the signature or | | | signatures were acceptable to the verifier, but | | | they failed the verification test(s). | | | | | policy | The message was signed, signature(s) passed | | | verification tests, but the signature or signatures | | | were not acceptable to the verifier. | | | | | neutral | The message was signed but the signature or | | | signatures contained syntax errors or were not | | | otherwise able to be processed. This result SHOULD | | | also be used for other failures not covered | | | elsewhere in this list. | | | | | temperror | The message could not be verified due to some error | | | that is likely transient in nature, such as a | | | temporary inability to retrieve a certificate or | | | CRL. A later attempt may produce a final result. | | | | | permerror | The message could not be verified due to some error | | | that is unrecoverable, such as a required header | | | field being absent or the signer's certificate not | | | being available. A later attempt is unlikely to | | | produce a final result. | +-------------+-----------------------------------------------------+ A signature is "acceptable to the verifier" if it passes local policy checks (or there are no specific local policy checks). For example, a verifier might require that the domain in the rfc822Name subjectAltName in the signing certificate matches the domain in the address of the sender of the message, thus making third-party signatures unacceptable. [RFC5751] advises that if a message fails verification, it should be treated as an unsigned message. A report of "fail" here permits the receiver of the report to decide how to handle the failure. A report of "neutral" or "none" preempts that choice, ensuring the message will be treated as if it had not been signed. 3.2. Examples Return-Path: Authentication-Results: example.com; smime=fail (certificate is revoked by CRL) body.smime-identifier=aliceDss@examples.com body.smime-part=2 Melnikov Expires April 14, 2014 [Page 3] Internet-DrafAuthentication-Results Registration for S/MIME October 2013 Received: from ietfa.amsl.com (localhost [IPv6:::1]) by ietfa.amsl.com (Postfix) with ESMTP id 2875111E81A0; Fri, 06 Sep 2002 00:35:14 -0700 (PDT) MIME-Version: 1.0 To: User2@examples.com From: aliceDss@examples.com Subject: Example 4.8 Message-Id: <020906002550300.249@examples.com> Date: Fri, 06 Sep 2002 00:25:21 -0700 Content-Type: multipart/signed; micalg=SHA1; boundary="----=_NextBoundry____Fri,_06_Sep_2002_00:25:21"; protocol="application/pkcs7-signature" This is a multi-part message in MIME format. ------=_NextBoundry____Fri,_06_Sep_2002_00:25:21 This is some sample content. ------=_NextBoundry____Fri,_06_Sep_2002_00:25:21 Content-Type: application/pkcs7-signature; name=smime.p7s Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename=smime.p7s MIIDdwYJKoZIhvcNAQcCoIIDaDCCA2QCAQExCTAHBgUrDgMCGjALBgkqhkiG9w0BBwGgggL gMIIC3DCCApugAwIBAgICAMgwCQYHKoZIzjgEAzASMRAwDgYDVQQDEwdDYXJsRFNTMB4XDT k5MDgxNzAxMTA0OVoXDTM5MTIzMTIzNTk1OVowEzERMA8GA1UEAxMIQWxpY2VEU1MwggG2M IIBKwYHKoZIzjgEATCCAR4CgYEAgY3N7YPqCp45PsJIKKPkR5PdDteoDuxTxauECE//lOFz SH4M1vNESNH+n6+koYkv4dkwyDbeP5u/t0zcX2mK5HXQNwyRCJWb3qde+fz0ny/dQ6iLVPE /sAcIR01diMPDtbPjVQh11Tl2EMR4vf+dsISXN/LkURu15AmWXPN+W9sCFQDiR6YaRWa4E8 baj7g3IStii/eTzQKBgCY40BSJMqo5+z5t2UtZakx2IzkEAjVc8ssaMMMeUF3dm1nizaoFP VjAe6I2uG4Hr32KQiWn9HXPSgheSz6Q+G3qnMkhijt2FOnOLl2jB80jhbgvMAF8bUmJEYk2 RL34yJVKU1a14vlz7BphNh8Rf8K97dFQ/5h0wtGBSmA5ujY5A4GEAAKBgFzjuVp1FJYLqXr d4z+p7Kxe3L23ExE0phaJKBEj2TSGZ3V1ExI9Q1tv5VG/+onyohs+JH09B41bY8i7RaWgSu OF1s4GgD/oI34a8iSrUxq4Jw0e7wi/ZhSAXGKsZfoVi/G7NNTSljf2YUeyxDKE8H5BQP1Gp 2NOM/Kl4vTyg+W4o4GBMH8wDAYDVR0TAQH/BAIwADAOBgNVHQ8BAf8EBAMCBsAwHwYDVR0j BBgwFoAUcEQ+gi5vh95K03XjPSC8QyuT8R8wHQYDVR0OBBYEFL5sobPjwfftQ3CkzhMB4v3 jl/7NMB8GA1UdEQQYMBaBFEFsaWNlRFNTQGV4YW1wbGUuY29tMAkGByqGSM44BAMDMAAwLQ IUVQykGR9CK4lxIjONg2q1PWdrv0UCFQCfYVNSVAtcst3a53Yd4hBSW0NevTFjMGECAQEwG DASMRAwDgYDVQQDEwdDYXJsRFNTAgIAyDAHBgUrDgMCGjAJBgcqhkjOOAQDBC4wLAIUM/mG f6gkgp9Z0XtRdGimJeB/BxUCFGFFJqwYRt1WYcIOQoGiaowqGzVI ------=_NextBoundry____Fri,_06_Sep_2002_00:25:21-- 4. IANA Considerations Melnikov Expires April 14, 2014 [Page 4] Internet-DrafAuthentication-Results Registration for S/MIME October 2013 IANA is requested to add the the following entries to the "Email Authentication Methods" subregistry of the "Email Authentication Parameters" registry: +--------+-----------+--------+------------------+------------------+ | Method | Defined | ptype | property | value | +--------+-----------+--------+------------------+------------------+ | smime | [RFC5751] | body | smime-part | The MIME body | | | | | | part reference | | | | | | which contains | | | | | | the signature. | | | | | | See definition | | | | | | of
in | | | | | | Section 6.4.5 of | | | | | | [RFC3501] | | | | | | | | smime | [RFC5751] | body | smime-identifier | The email | | | | | | address | | | | | | [RFC5322] | | | | | | associated with | | | | | | the S/MIME | | | | | | signature. Note | | | | | | that this email | | | | | | address can | | | | | | correspond to a | | | | | | counter | | | | | | signature. | +--------+-----------+--------+------------------+------------------+ IANA is requested to add the the following entries to the "Email Authentication Result Names" subregistry of the "Email Authentication Parameters" registry: +-------------+--------------+------------+---------------+---------+ | Code | Defined | Auth | Meaning | Status | | | | Method | | | +-------------+--------------+------------+---------------+---------+ | none | this | smime | [this memo] | active | | | document | | Section 3.1 | | | | | | | | | pass | this | smime | [this memo] | active | | | document | | Section 3.1 | | | | | | | | | fail | this | smime | [this memo] | active | | | document | | Section 3.1 | | | | | | | | | policy | this | smime | [this memo] | active | Melnikov Expires April 14, 2014 [Page 5] Internet-DrafAuthentication-Results Registration for S/MIME October 2013 | | document | | Section 3.1 | | | | | | | | | neutral | this | smime | [this memo] | active | | | document | | Section 3.1 | | | | | | | | | temperror | this | smime | [this memo] | active | | | document | | Section 3.1 | | | | | | | | | permerror | this | smime | [this memo] | active | | | document | | Section 3.1 | | +-------------+--------------+------------+---------------+---------+ 5. Security Considerations This document doesn't add new security considerations not already covered by [RFC7001] and [RFC5751]. In particular security considerations related to use of weak cryptography over plaintext, weakening and breaking of cryptographic algorithms over time, as well as changing the behavior of message processing based on presence of a signature specified in [RFC5751] are relevant to this document. Similarly, the following security considerations specified in [RFC7001] are particularly relevant to this document: Forged Header Fields, Misleading Results, Internal MTA Lists and Compromised Internal Hosts. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC 3501, March 2003. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008. [RFC7001] Kucherawy, M., "Message Header Field for Indicating Message Authentication Status", RFC 7001, September 2013. [RFC5751] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification", RFC 5751, January 2010. Melnikov Expires April 14, 2014 [Page 6] Internet-DrafAuthentication-Results Registration for S/MIME October 2013 6.2. Informative References [RFC3183] Dean, T. and W. Ottaway, "Domain Security Services using S /MIME", RFC 3183, October 2001. Appendix A. Acknowledgements Thank you to Murray S. Kucherawy, David Wilson and Steve Kille for comments and corrections on this document. Author's Address Alexey Melnikov Isode Ltd 5 Castle Business Village 36 Station Road Hampton, Middlesex TW12 2BX UK EMail: Alexey.Melnikov@isode.com Melnikov Expires April 14, 2014 [Page 7]