[gnutls-devel] DER decoding errors due to time format

Nikos Mavrogiannopoulos n.mavrogiannopoulos at gmail.com
Wed May 10 14:06:42 CEST 2017

On Tue, May 9, 2017 at 8:47 PM, Kurt Roeckx <kurt at roeckx.be> wrote:
> On Tue, May 09, 2017 at 02:48:08PM +0200, Nikos Mavrogiannopoulos wrote:
>> Hi,
>>  gnutls 3.5.x is more strict in certificate decoding and performs
>> various checks in the Time fields to ensure they are properly DER
>> formatted. However, it is seems that this caused regressions with
>> certain certificates generated by ovirt as seen in [0]. I am not sure
>> which software was used to generate the problematic ones, however, it
>> is most likely openssl, or some other open source software. Are you
>> aware of other or similar decoding issues which were a result of 3.5.x
>> being more strict in DER rules?
>> The options we have are:
>>  1. Ignore the error and insist on DER correctness in input certificates.
>>  2. Allow incorrect formatted time fields in certificates
>> unconditionally, e.g., with a special libtasn1 flag:
>> https://gitlab.com/gnutls/libtasn1/commit/16bad0c72dcdfbe5512cdd6b46b251ab7484e5dc
>> any other option I've missed? While I favor the first for its
>> simplicity, reality has shown over the years we must yield towards the
>> 'work' part.
> NSS is strict in what it accepts. We've recently changed openssl to be
> more strict too (commit 80770da39ebba0101079477611b7ce2f426653c5,
> https://github.com/openssl/openssl/issues/2620), but maybe not
> strict enough yet.

Thank you, that is really helpful. It seems that Kurt has found out
the culprit. There seem to be a user input validation issue in openssl
when generating certs:


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