Update to the Cryptographic Message Syntax (CMS) for Algorithm Identifier Protection
RFC 8933
Document | Type |
RFC - Proposed Standard
(October 2020; No errata)
Updates RFC 5652
|
|
---|---|---|---|
Author | Russ Housley | ||
Last updated | 2020-10-09 | ||
Replaces | draft-housley-lamps-cms-update-alg-id-protect | ||
Stream | IETF | ||
Formats | plain text html xml pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Tim Hollebeek | ||
Shepherd write-up | Show (last changed 2020-06-30) | ||
IESG | IESG state | RFC 8933 (Proposed Standard) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Roman Danyliw | ||
Send notices to | Tim Hollebeek <tim.hollebeek@digicert.com> | ||
IANA | IANA review state | IANA OK - No Actions Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) R. Housley Request for Comments: 8933 Vigil Security Updates: 5652 October 2020 Category: Standards Track ISSN: 2070-1721 Update to the Cryptographic Message Syntax (CMS) for Algorithm Identifier Protection Abstract This document updates the Cryptographic Message Syntax (CMS) specified in RFC 5652 to ensure that algorithm identifiers in signed- data and authenticated-data content types are adequately protected. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8933. Copyright Notice Copyright (c) 2020 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. Table of Contents 1. Introduction 2. Terminology 3. Required Use of the Same Hash Algorithm 3.1. RFC 5652, Section 5.3 3.2. RFC 5652, Section 5.4 3.3. RFC 5652, Section 5.6 3.4. Backward Compatibility Considerations 3.5. Timestamp Compatibility Considerations 4. Recommended Inclusion of the CMSAlgorithmProtection Attribute 4.1. RFC 5652, Section 14 5. IANA Considerations 6. Security Considerations 7. References 7.1. Normative References 7.2. Informative References Acknowledgements Author's Address 1. Introduction This document updates the Cryptographic Message Syntax (CMS) [RFC5652] to ensure that algorithm identifiers in signed-data and authenticated-data content types are adequately protected. The CMS signed-data content type [RFC5652], unlike X.509 certificates [RFC5280], can be vulnerable to algorithm substitution attacks. In an algorithm substitution attack, the attacker changes either the algorithm identifier or the parameters associated with the algorithm identifier to change the verification process used by the recipient. The X.509 certificate structure protects the algorithm identifier and the associated parameters by signing them. In an algorithm substitution attack, the attacker looks for a different algorithm that produces the same result as the algorithm used by the originator. As an example, if the signer of a message used SHA-256 [SHS] as the digest algorithm to hash the message content, then the attacker looks for a weaker hash algorithm that produces a result that is of the same length. The attacker's goal is to find a different message that results in the same hash value, which is called a cross-algorithm collision. Today, there are many hash functions that produce 256-bit results. One of them may be found to be weak in the future. Further, when a digest algorithm produces a larger result than is needed by a digital signature algorithm, the digest value is reduced to the size needed by the signature algorithm. This can be done both by truncation and modulo operations, with the simplest being straightforward truncation. In this situation, the attacker needs to find a collision with the reduced digest value. As an example, if the message signer uses SHA-512 [SHS] as the digest algorithm and the Elliptic Curve Digital Signature Algorithm (ECDSA) with the P-256 curve [DSS] as the signature algorithm, then the attacker needs to find a collision with the first half of the digest. Similar attacks can be mounted against parameterized algorithm identifiers. When randomized hash functions are employed, such as the example in [RFC6210], the algorithm identifier parameter includes a random value that can be manipulated by an attacker looking for collisions. Some other algorithm identifiers include complex parameter structures, and each value provides another opportunity for manipulation by an attacker.Show full document text