[Pkg-gnutls-maint] Bug#481132: Bug#481132: libgnutls26: flags key usage error where OpenSSL does not

[Simon Josefsson]

"brian m. carlson" <sandals at crustytoothpaste.ath.cx> writes:

> Package: libgnutls26
> Version: 2.2.3-1
> Severity: important
>
> I regenerated my SSL certificates today (due to the security advisory)
> and mutt now refuses to connect to my SMTP server with STARTTLS.  This
> is obviously unsuitable.
>
> Using cyrus-clients-2.3's smtptest (which uses OpenSSL) does not object
> to the certificate.  You can find the old certificate, which worked
> fine, at
> http://crustytoothpaste.ath.cx/cgi-bin/pyca/view-cert.py/ServerCerts/server?18
> .  I generated them exactly the same way, and they appear to have
> exactly the same extensions.  The MTA is sendmail, which uses OpenSSL.
>
> Feel free to test against my machine if you want.
>
> Transcript of session:
>
> lakeview ok % gnutls-cli -p 587 -s crustytoothpaste.ath.cx

Hi!  Thanks for the report.  Unfortunately, I think your certificate is
incorrect, you'll need the digitalSignature Key Usage Bit as well.

RFC 2246 and 4346:

      DHE_RSA                 RSA public key that can be used for
                              signing.
...
   All certificate profiles and key and cryptographic formats are
   defined by the IETF PKIX working group [PKIX].  When a key usage
   extension is present, the digitalSignature bit MUST be set for the
   key to be eligible for signing, as described above, and the
   keyEncipherment bit MUST be present to allow encryption, as described
   above.  The keyAgreement bit must be set on Diffie-Hellman
   certificates.

See a similar recent report:

http://thread.gmane.org/gmane.comp.encryption.gpg.gnutls.devel/2788/focus=2789

/Simon