Re: [TLS] Empty CertificateRequest.supported_signature_algorithms in TLS 1.2
Eric Rescorla <ekr@rtfm.com> Wed, 21 November 2018 22:01 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 21 Nov 2018 14:00:55 -0800
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To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [TLS] Empty CertificateRequest.supported_signature_algorithms
in TLS 1.2
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On Wed, Nov 21, 2018 at 1:50 PM Martin Thomson <martin.thomson@gmail.com> wrote: > In attempting to fix a bug related to this, a question came up about > what the semantics of an empty value is here. Some implementations > seem to infer that empty means {*,SHA1}, which effectively assumes > that an empty value is equivalent to an absent signature_algorithms > extension (Section 7.4.1.4.1) > > The text on CertificateRequest is less clear about what to do. That's > understandable because it doesn't have to deal with the value being > absent because it's not optional. All we have to go on is this from > Section 7.4.8: > > The hash and signature algorithms used in the signature MUST be > one of those present in the supported_signature_algorithms field > of the CertificateRequest message. > > We think that treating an empty supported_signature_algorithms field > as an error is the best response and plan to implement that change. > We'll send a fatal alert if we receive one. > Yes, I believe this is the right approach. -Ekr > This is consistent with our handling of the signature_algorithms > extension, where we treat an empty list as a failure. > > _______________________________________________ > TLS mailing list > TLS@ietf.org > https://www.ietf.org/mailman/listinfo/tls >
- [TLS] Empty CertificateRequest.supported_signat... Martin Thomson
- Re: [TLS] Empty CertificateRequest.supported_si... Viktor Dukhovni
- Re: [TLS] Empty CertificateRequest.supported_si... Eric Rescorla
- Re: [TLS] Empty CertificateRequest.supported_si... David Benjamin
- Re: [TLS] Empty CertificateRequest.supported_si... Martin Thomson