Re: crypto test failures on Fedora and OpenSUSE

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

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Hi folks--

On Sun 2020-06-28 08:33:42 -0300, David Bremner wrote:
> I dug a bit further down, and this is what is returned from gpgme
> (line 345 in g_mime_gpgme_get_signatures)
>
> sig = {next = 0x0,
>     summary = GPGME_SIGSUM_KEY_MISSING, 
>     fpr = 0x4ac480 "5AEAB11F5E33DCE875DDB75B6D92612D94E46381", status = 9, 
>     notations = 0x0, timestamp = 1559167762, exp_timestamp = 0, wrong_key_usage = 0, 
>     pka_trust = 0, chain_model = 0, is_de_vs = 0, _unused = 0, 
>     validity = GPGME_VALIDITY_UNKNOWN, validity_reason = 0, 
>     pubkey_algo = GPGME_PK_RSA, hash_algo = GPGME_MD_SHA256, pka_address = 0x0, 
>     key = 0x0}
>
> At this point I'm leaning towards declaring it a gpgme problem in
> fedora32, and suggesting that relevant distros mark the test broken. I
> am of course open to more informed opinions.

The problem does indeed appear to be with gpgme, in versions 1.13.0 and
1.13.1.

In particular, it is a problem with the resolution of
https://dev.gnupg.org/T3464, which is ultimately fixed upstream, but is
not yet fixed in a released version of gpgme.

The upstream commit, which should be patched into gpgme on Fedora and
OpenSUSE (and anywhere else that depends on gpgme) is:

    https://dev.gnupg.org/rMae4d7761a15b82eb98b0bcc72af2ae2e8973e1f9

(patch attached here as well)

We don't see this on Debian because gpgme in debian has carried this
patch for over a year now.

In gpgme 1.12.0 and earlier, this bug did not exist.  But gpgme 1.13.0
introduced the bug in an attempt to avoid error diagnostics when *not*
trying to verify a signature while using a session key.  The fix in
1.13.0 inadvertently introduced an error when the caller does actually
try to verify a signature, which is what we see here.

      --dkg


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From ae4d7761a15b82eb98b0bcc72af2ae2e8973e1f9 Mon Sep 17 00:00:00 2001
From: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
Date: Wed, 29 May 2019 17:56:01 -0400
Subject: [GPGME PATCH] gpg: Avoid error diagnostics with
 --override-session-key when verifying

* src/engine-gpg.c (gpg_decrypt): only send --no-keyring when we are
not verifying.

--

Without this change, the signature verification would fail.  This
problem was introduced in bded8ebc59c7fdad2617f4c9232a58047656834c in
an attempt to avoid an error when *not* verifying.  Clearly more test
suite coverage is needed to avoid introducing this sort of problem in
the future.

GnuPG-bug-id: 3464
Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
---
 src/engine-gpg.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/engine-gpg.c b/src/engine-gpg.c
index 5c335cb2..223404ed 100644
--- a/src/engine-gpg.c
+++ b/src/engine-gpg.c
@@ -1717,12 +1717,15 @@ gpg_decrypt (void *engine,
                                          strlen (override_session_key), 1);
           if (!err)
             {
-              /* We add --no-keyring because a keyring is not required
-               * when we are overriding the session key.  It would
+              /* When we are not trying to verify signatures as well,
+               * we add --no-keyring because a keyring is not required
+               * for decryption when overriding the session key.  It would
                * work without that option but --no-keyring avoids that
                * gpg return a failure due to a missing key log_error()
                * diagnostic.  --no-keyring is supported since 2.1.14. */
-              err = add_arg (gpg, "--no-keyring");
+
+              if (!(flags & GPGME_DECRYPT_VERIFY))
+                  err = add_arg (gpg, "--no-keyring");
               if (!err)
                 err = add_arg (gpg, "--override-session-key-fd");
               if (!err)
-- 
2.27.0


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