Thanks again for your review, Tero. The resolutions discussed in this thread have been applied to the -32 draft. -- Mike -----Original Message----- From: Tero Kivinen [mailto:kivinen@xxxxxx] Sent: Monday, September 22, 2014 6:42 AM To: Mike Jones Cc: iesg@xxxxxxxx; secdir@xxxxxxxx; ietf@xxxxxxxx; draft-ietf-jose-json-web-signature.all@xxxxxxxxxxxxxx; jose@xxxxxxxx Subject: RE: Secdir review of draft-ietf-jose-json-web-signature-31 Mike Jones writes: > Tero - for your point "2) Hash inside "alg" and inside the signature", > could you please write proposed security considerations text > addressing this issue? I'd think it should describe the need for > implementations to ensure that signature verification is done for the > exact algorithm specified in the "alg" header parameter, no matter > what algorithm information may (or may not) have been encoded into the > signature value in an algorithm-specific manner. Something like this: In case of algorithms where there is algorithm parameters specified also inside the actual signature, the implementations MUST verify that the parameters inside the signature and the parameters specified by the "alg" Header Parameter match. This includes for example the RSASSA-PKCS-v1_5 algorithms ("RS*") where the signature contains the hash algorithm and most libraries actually use the hash algorithm specified inside the signature when verifying the signature. This test is required as the steps in the section 5.2 verify that algorithms specified by the "alg" Header Parameter are acceptable, and if those algorithms could be different the attacker could be able to claim to use strong hash algorithm while actually using weak one inside the signature. > For your point "3) There is no explicit warning about the "alg" > "none"", I plan to add the additional step that you suggested. In my text above I assumed you had already added step in section 5.2 to verify that "alg" is acceptable. > For your point "4) Thumbprint formats" if you or someone else wants to > define an additional thumbprint format for use in IoT contexts (or any > other contexts), I encourage you to write an Internet Draft that does > so, registering the new header parameter defined in the JSON Web > Signature and Encryption Header Parameters registry. That can of course be done, but I would have hoped the initial version of the specification would also be usable in the IoT context, where the use of raw public keys will most likely arise. -- kivinen@xxxxxx