The following errata report has been submitted for RFC5288, "AES Galois Counter Mode (GCM) Cipher Suites for TLS".
-------------------------------------- You may review the report below and at: http://www.rfc-editor.org/errata_search.php?rfc=5288&eid=4694 -------------------------------------- Type: Technical Reported by: Aaron Zauner <[email protected]> Section: 6.1 Original Text ------------- AES-GCM security requires that the counter is never reused. The IV construction in Section 3 is designed to prevent counter reuse. Implementers should also understand the practical considerations of IV handling outlined in Section 9 of [GCM]. Corrected Text -------------- Security of AES-GCM requires that the "nonce" (number used once) is never reused. The IV construction in Section 3 does not prevent implementers from reusing the nonce by mistake. It is paramount that the implementer be aware of the security implications when a nonce is re-used even once. Nonce re-use in AES-GCM results in catastrophic failure of it's authenticity. Hence, TLS sessions can be effectively attacked through forgery by an adversary. In the case of e.g. HTTPS sessions content injection is possible, XSS and other attack vectors. Notes ----- Obviously the original wording is so ambiguous that implementers got it wrong in the real world. Related to: https://www.blackhat.com/us-16/briefings.html#nonce-disrespecting-adversaries-practical-forgery-attacks-on-gcm-in-tls It may be worth adding a reference to [JOUX] http://csrc.nist.gov/groups/ST/toolkit/BCM/documents/...38.../GCM/Joux_comments.pdf and maybe the paper we're intending to release on the actual HTTPS forgery/injection attack. I'd actually like to change the nonce construction to that of the ChaCha20/Poly1305 document, but I figure this will cause massive breakage for already deployed implementations. TLS 1.3 fixes this issue per design. 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. -------------------------------------- RFC5288 (draft-ietf-tls-rsa-aes-gcm-03) -------------------------------------- Title : AES Galois Counter Mode (GCM) Cipher Suites for TLS Publication Date : August 2008 Author(s) : J. Salowey, A. Choudhury, D. McGrew Category : PROPOSED STANDARD Source : Transport Layer Security Area : Security Stream : IETF Verifying Party : IESG _______________________________________________ TLS mailing list [email protected] https://www.ietf.org/mailman/listinfo/tls
