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Re: [TLS] TLSv1.2 - Is zero signature allowed in client CertificateVerify message?

Richard Barnes <rlb@ipv.sx> Tue, 03 September 2019 14:36 UTC

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From: Richard Barnes <rlb@ipv.sx>
Date: Tue, 03 Sep 2019 10:35:57 -0400
Message-ID: <CAL02cgS0OsUxXz2ht=4uY-ZYqOdmYYCc6VqrHo5LrEusATwEtA@mail.gmail.com>
To: M K Saravanan <mksarav@gmail.com>
Cc: "<tls@ietf.org>" <tls@ietf.org>
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Subject: Re: [TLS] TLSv1.2 - Is zero signature allowed in client CertificateVerify message?
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I don't believe that's a valid signature according to rsa_pkcs1_sha256, so
yeah, this is probably an error.
--Richard

On Sun, Sep 1, 2019 at 11:33 PM M K Saravanan <mksarav@gmail.com> wrote:

> Hi,
>
> Is zero signature allowed in client CertificateVerify message (I am
> guessing may be to indicate error condition??). I don't see any thing
> related to zero signature in the TLS 1.2 RFC (or may be I am not looking
> into the right section?)
>
> Today I saw a packet like this and server was terminating the connection
> due to the failure of client cert auth. (because of zero signature in
> client cert verify message).
>
> [image: image.png]
>
> Under what circumstances a client can send a zero signature in the client
> CertificateVerify message?  Is this behaviour TLS 1.2 RFC compliant?
>
> with regards,
> Saravanan
>
>
>
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