Bug#691864: libgnutls28: gnutls does not sort certificate chain to be verified

[Daniel Kahn Gillmor]

Control: severity 691864 wishlist
Control: retitle 691864 please allow mis-ordered certificate chains
Control: fixed 691864 3.1.3-1

On 10/30/2012 10:00 AM, Michal Suchanek wrote:
> eg. server has certificate S which is signed by intermediate I which is
> signed by CA root R. The server supplies chain S R I which is verified
> by gnutls 3.1 but not 3.0. Such servers exist in the wild so this is
> clearly an interoporebility issue.

it is clearly an interoperability issue, but the peers that are causing
it are the peers with the mis-ordered certificates, not GnuTLS.

GnuTLS 3.0 is following the RFC, which states:

 https://tools.ietf.org/html/rfc5246#section-7.4.2

      The sender's
      certificate MUST come first in the list.  Each following
      certificate MUST directly certify the one preceding it.

> In gnutls 3.1.3 GNUTLS_VERIFY_ALLOW_UNSORTED_CHAIN flag is available and
> defaults to on. When this flag is set such chain is verified without
> issues.

The fact that GnuTLS 3.1 is willing to work around this situation does
not indicate that strict RFC-compliance is a bug in GnuTLS 3.0, much
less a bug of severity: important.

	--dkg

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