Re: [smime] [Technical Errata Reported] RFC5084 (4774)

[Russ Housley <[e-mail]>]

Quan:

I do not think that we can change the DEFAULT value associated with these OIDs.  Changing the meaning of an absent aes-ICVlen will result in too many interoperability problems.  However, we could put out a very short RFC that updates RFC 5084 to recommend the use of 16 octet authentication tags in all situations.  

Russ


On Aug 11, 2016, at 2:49 PM, Quan Nguyen <[e-mail]> wrote:

> 
> 
> On Thu, Aug 11, 2016 at 11:47 AM, RFC Errata System <[e-mail]> wrote:
> The following errata report has been submitted for RFC5084,
> "Using AES-CCM and AES-GCM Authenticated Encryption in the Cryptographic Message Syntax (CMS)".
> 
> --------------------------------------
> You may review the report below and at:
> http://www.rfc-editor.org/errata_search.php?rfc=5084&eid=4774
> 
> --------------------------------------
> Type: Technical
> Reported by: QUAN NGUYEN <[e-mail]>
> 
> Section: 3.2
> 
> Original Text
> -------------
> aes-ICVlen       AES-GCM-ICVlen DEFAULT 12
> 
> A length of 12 octets is RECOMMENDED.
> 
> Corrected Text
> --------------
> aes-ICVlen       AES-GCM-ICVlen DEFAULT 16
> 
> A length of 16 octets is RECOMMENDED.
> 
> Notes
> -----
> Many JCE providers including OpenJDK, BouncyCastle, Conscrypt have a bug to use 12 bytes authentication tag (aes-ICVlen) as default if the code path [1] uses CMS. According to Ferguson's attack (http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/comments/CWC-GCM/Ferguson2.pdf), if a user encrypts 2^32 block length message, then 12 bytes authentication tag length has only 96 - 32 = 64 bits security which is not good enough nowadays. Furthermore, once a forgery happens then authentication is leaked.
> 
> Sorry, I meant "authentication key" is leaked. 
> 
> [1] In other code paths, all providers use 16 bytes authentication tag as default.
> 
> Instructions:
> -------------
> This erratum is currently posted as "Reported". If necessary, please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party (IESG)
> can log in to change the status and edit the report, if necessary.
> 
> --------------------------------------
> RFC5084 (draft-ietf-smime-cms-aes-ccm-and-gcm-03)
> --------------------------------------
> Title               : Using AES-CCM and AES-GCM Authenticated Encryption in the Cryptographic Message Syntax (CMS)
> Publication Date    : November 2007
> Author(s)           : R. Housley
> Category            : PROPOSED STANDARD
> Source              : S/MIME Mail Security
> Area                : Security
> Stream              : IETF
> Verifying Party     : IESG
> 
>