Security implications of (not using) GNUTLS_VERIFY_DO_NOT_ALLOW_SAME

[Nikos Mavrogiannopoulos]

On Mon, Jun 21, 2010 at 12:43 PM, Lars Noschinski
<lars at public.noschinski.de> wrote:

>> I don't see any normal situation where this flag is useful.
>>
>> I'm not sure the behaviour you see is actually intended, I don't see why
>> it should reject the chain here.  So it may be a bug...
>>
>> The flag _may_ be useful if you have a X.509 Version 1 certificate as a
>> trust anchor.  You may want to trust a X.509v1 CA for verifying server
>> certificates signed by the X.509v1 CA, but you definitely do not want to
>> accept that certificate as the server certificate (because there are no
>> name restriction extensions).  On the other hand, you shouldn't use
>> X.509v1 certificates anyway...
>
> Just to clarify: Using GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT without
> GNUTLS_VERIFY_DO_NOT_ALLOW_SAME is a sane choice (if one stills needs to
> deal with X.509v1 certificates).

The GNUTLS_VERIFY_DO_NOT_ALLOW_SAME is a flag, to make the trusted
certificate list, a list that can only certify other keys. That is it
will not allow a certificate from this list to be used as a server
certificate. So how it works it depends on your usage of this list. If
you add end server certificates there maybe
GNUTLS_VERIFY_DO_NOT_ALLOW_SAME is not a good option for you. But for
other uses it is quite sensible.

regards,
Nikos