Re: [PATCH] crypto: signature verification reports valid User IDs

Subject: Re: [PATCH] crypto: signature verification reports valid User IDs

Date: Fri, 08 Dec 2017 13:55:20 -0500

To: David Bremner, Notmuch Mail


From: Daniel Kahn Gillmor

On Fri 2017-12-08 14:36:04 -0400, David Bremner wrote:
> Daniel Kahn Gillmor <> writes:
>> @@ -478,9 +478,10 @@ fi
>>  # we need to have a version >= 2.6.5 to avoid a crypto bug. We need
>>  # 2.6.7 for permissive "From " header handling.
>>  GMIME_MINVER=2.6.7
>> +GMIME3_MINVER=3.0.3
> Does this change mean notmuch won't build at all for people with gmime-3
> < 3.0.3? I understand that's not a problem in Debian, but what about in
> general?

iiuc, if you've only got gmime-3 version < 3.0.3, then you will not be
able to build notmuch.  however, if you have that *and* you have a
version of gmime-2.6, configure will just use gmime 2.6.

If you only have gmime-2.4, or a version of gmime 2.6 before 2.6.7, then
you are SOL.

I think that's an acceptable situation, though.  We're not taking away
too many options from users.

Also, when built against 3.0.0, 3.0.1, or 3.0.2, the identification
information shown during signed messages is strictly *wrong* -- it shows
the assigned ownertrust of a certificate where it should show the
validity.  This is not only wrong, but it's actively dangerous, because
it encourages users to mark keys with elevated ownertrust "just to turn
them green".  This is the equivalent of encouraging users to add
arbitrary root CAs to their list of trusted X.509 anchors.  Not
something a MUA should be doing.

>> +
>> +static const char*
>> +_get_certificate_valid_userid (GMimeCertificate *cert)
>> +{
> Since we already have util/gmime-extra.c to deal with differences
> between gmime-3.0 and 2.6, and since this code is purely gmime related
> (not using any notmuch data or types), it makes sense to me put this
> (split) there. I guess we might use a different prefix for stuff we add,
> although iirc we didn't bother for zlib-extra.c

The (very slight) disadvantage of putting this code in
util/gmime-extra.c is that it will no longer be static, but will instead
be exposed across compilation units.  That said, i don't think that's
actually a big deal, and i understand why you want it in
util/gmime-extra.c. So i'll send a new revision of this patch shortly.

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