Re: ECDSA test key/files

Aleksey Sanin <[email protected]> Fri, 3 Mar 2017 15:45:24 -0800
Newsgroups	gmane.text.xml.xmlsec
Message-ID	<[email protected]>
Yes, this sounds like a bug. Any chance you can also fix
OpenSSL implementation then?

Aleksey

On 3/3/17 3:21 PM, Miklos Vajna wrote:
> Hi,
> 
> I found one more problem around the ECDSA test files.
> 
> For example, tests/aleksey-xmldsig-01/enveloping-sha256-ecdsa-sha256.xml
> has a <SignatureValue> that is of 64 bytes after base64 decode.
> 
> However, when I tried to test the signature verifier with other ECDSA
> testcases, the signature value was longer. Example:
> The last attachment to
> <https://bugs.documentfoundation.org/show_bug.cgi?id=105983> has a
> signature that looks like this:
> 
>     <SignatureValue xmlns="http://www.w3.org/2000/09/xmldsig#" Id="SignatureValue_4513a8b22f16c956d127c7844419ed2b006635af4e855d7f1d06ea9d49e4e8af">MEQCIHpA2WCOXQ5z7qcmtIU+LiPgh3WBUBga7Ny0sZ8Jh9FhAiB0Mr6G+9zMTmkuOOeVZmwuIcQjcSm5SPg+Gfi0T7cdcw==</SignatureValue>
> 
> i.e. it's 70 bytes after base64 decode: it's 2 integers of 32 bytes, but
> it's ASN1 encoded.
> 
> This difference made me curious: which one is incorrect?
> 
> As far as I see this is specified in
> https://www.ietf.org/rfc/rfc3279.txt, section "2.2.3 ECDSA Signature
> Algorithm". It says:
> 
> "To easily transfer these two
>    values as one signature, they MUST be ASN.1 encoded using the
>    following ASN.1 structure:
> 
>       Ecdsa-Sig-Value  ::=  SEQUENCE  {
>            r     INTEGER,
>            s     INTEGER  }"
> 
> So to me, it looks like:
> 
> - the xmlsec openssl backend doesn't do this encoding, even if it's a
>   must according to the RFC
> - the test file tests this bad behavior
> - because i used the test files as a reference for the behavior, now I
>   implemented the same in the nss backend as well
> 
> Would it be OK if I change (send a pull request that changes) the test
> files to contain this required ASN1 encoding? Fixing the NSS backend is
> easy to read/write the encoded form, I can do that. I can also try to
> fix the openssl backend to conform to the RFC.
> 
> Thanks,
> 
> Miklos
> 
> 
> 
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>

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