gnutls fails to use Verisign CA cert without a Basic Constraint

[Simon Josefsson]

Nikos Mavrogiannopoulos <n.mavrogiannopoulos at gmail.com> writes:

> On Sat, 10 Jan 2009 13:05:05 +0100
>
>> Nikos, what do you think?  You wrote the code here, and introduced the
>> work-around flags to deal with V1 certs.
>
> X.509 v1 certificates are quite dangerous to use and should be avoided
> because of the inherited issues with them (a V1 CA certificate cannot be
> distinguished from a V1 server certificate or a V1 person certificate,
> thus if one has a V1 server certificate in his trusted certificate list
> wouldn't want to trust it as a CA as well).
>
> For these reasons V1, certificates are not trusted to be signers by
> default unless the following two flags are set:
>
> 1. GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT
>
> This one allows a v1 certificate from the trusted list to be valid as
> a CA (here one must know that he should not add V1 server certificates
> in his trusted list).
>
> 2. GNUTLS_VERIFY_ALLOW_ANY_X509_V1_CA_CRT
>
> This one is quite dangerous. It allows any intermediate V1 certificate
> to be used as a signer. This means that if I manage to get a CA to give
> me a V1 personal certificate, I can act as a CA if this flag is set.

Good points.

>> For things that aren't documented, I think we can be pragmatic and
>> come up with quick fixes and apply them to the v2.6.x branch as
>> needed.  But anything that changes documented and intended behaviour
>> is not appropriate for our stable branch IMHO.
>
> I didn't follow the issue closely, but I'd be against any change of the
> V1 certificate handling unless there is a good reason to do so. V1
> certificates should not be used any more.

I agree fully.

I believe the proper fix in this situation is to patch GnuTLS as
suggested, and fix the applications to use the
GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT parameter when verifying chains using
GnuTLS.  Douglas, if you can confirm that this solves your problem, we
can release a new stable 2.6.x with the fix relatively quickly.

>> > If the code change on you TODO list to stop when an intermediate CA
>> > cert is found on the trusted CA list, then this would solve my
>> > problem, as the intermediate cert is V3 and has CA:TRUE, and is
>> > trusted.
>> Yup.  Fixing that would be neat, and could go onto the v2.7.x branch
>> which we could release as the next stable branch relatively quickly.
>
> About releasing 2.7, I think we should wait for the TLS 1.2 support to
> be completed or remove it from the supported list.

I agree.

/Simon