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

The client should just abort the handshake and probably send an alert like
internal_error since it cannot usefully proceed.

On Tue, Sep 3, 2019 at 11:27 AM M K Saravanan <mksarav@gmail.com> wrote:

> Thanks Richard for the reply.  Let me rephrase my question:
>
> If a client encounter any error condition (e.g. does not have access to
> the private key for whatever reason) in generating the signature, can it
> send zero bytes in the signature field of CertificateVerify message to
> indicate the error condition?  Is this allowed in TLS 1.2 RFC?
>
> with regards,
> Saravanan
>
>
> On Tue, 3 Sep 2019 at 22:36, Richard Barnes <rlb@ipv.sx> wrote:
>
>> 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
>>>
>>>
>>>
>>> _______________________________________________
>>> TLS mailing list
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>>> https://www.ietf.org/mailman/listinfo/tls
>>>
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Re: [TLS] TLSv1.2 - Is zero signature allowed in client CertificateVerify message?

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