Hi, thanks for your detailed answers. Yes, we are in contact with the developers of the implementations in question and fixes are going to be implemented. I just wanted to get an idea of what is considered the correct or at least most appropriate behaviour in each case. Thanks and Cheers >>> Martin Thomson <martin.thom...@gmail.com> 10.09.16 12.39 Uhr >>> I think that Martin (R) provided you with the answers I would have. Have you filed bugs against the servers in question for the issues that you have seen? On 10 September 2016 at 00:23, Andreas Walz <andreas.w...@hs-offenburg.de> wrote: > Dear all, > > we are working on an approach/framework for testing TLS implementations > (currently only servers, but clients are planned for the future as well). > While running our tests against a bunch of different TLS (server) > implementations, we found several types of suspicious behaviour (see below). > As the TLS specification left me with doubts on what the correct behaviour > should be, I'd like to raise this questions here (please let me know if this > is not the appropriate place or this has been answered before). > > (1) Several server implementations seem to ignore the list of proposed > compression methods in a ClientHello and simply select null compression even > if that has not been in the ClientHello's list. The specification is rather > clear that null compression MUST be part of the list. However, I'm not aware > of any clear statement about what a compliant server should do in case it > receives a ClientHello without null compression. My best guess would have > been that in such cases the server should abort the handshake (at least if > it does not support whatever the client proposed). > > (2) In a ClientHello several server implementations don't ignore data > following the extension list. That is, they somehow seem to ignore the > length field of the extension list and simply consider everything following > the list of compression methods as extensions. Aside from this certainly > being a deviation from the specification, I was wondering whether a server > should silently ignore data following the extension list (e.g. for the sake > of upward compatibility) or (as one could infer from RFC5246, p. 42) send > e.g. a "decode_error" alert. > > (3) If a ClientHello contains multiple extensions of the same type, several > server implementations proceed with the handshake (even if they parse these > specific extensions). The specification again is clear that "there MUST NOT > be more than one extension of the same type". However, what should a server > do in case there are? Again, my guess would be that it should abort the > handshake. Should this also be the case for extensions that a server simply > ignores (as it e.g. doesn't know them)? > > Thank you very much. > > Cheers, > Andi > > > _______________________________________________ > TLS mailing list > TLS@ietf.org > https://www.ietf.org/mailman/listinfo/tls >
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