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

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
>>
>>
>>
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>> https://www.ietf.org/mailman/listinfo/tls
>>
>

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

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