[PATCH 1/1] gpg-interface: limit search for primary key fingerprint

[Hans Jerry Illikainen <hji@dyntopia.com>]

The VALIDSIG status line from GnuPG with --status-fd has a field that
specifies the fingerprint of the primary key that made the signature.
However, that field is only available for OpenPGP signatures; not for
CMS/X.509.

An unbounded search for a non-existent primary key fingerprint for X509
signatures results in the following status line being interpreted as the
fingerprint.

Signed-off-by: Hans Jerry Illikainen <hji@dyntopia.com>
---
 gpg-interface.c | 20 +++++++++++++++-----
 t/t4202-log.sh  |  6 ++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/gpg-interface.c b/gpg-interface.c
index d60115ca40..01c7ef42d4 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -148,21 +148,31 @@ static void parse_gpg_output(struct signature_check *sigc)
 				}
 				/* Do we have fingerprint? */
 				if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
+					const char *limit;
+
 					next = strchrnul(line, ' ');
 					free(sigc->fingerprint);
 					sigc->fingerprint = xmemdupz(line, next - line);
 
-					/* Skip interim fields */
+					/* Skip interim fields.  The search is
+					 * limited to the same line since only
+					 * OpenPGP signatures has a field with
+					 * the primary fingerprint. */
+					limit = strchrnul(line, '\n');
 					for (j = 9; j > 0; j--) {
-						if (!*next)
+						if (!*next || next >= limit)
 							break;
 						line = next + 1;
 						next = strchrnul(line, ' ');
 					}
 
-					next = strchrnul(line, '\n');
-					free(sigc->primary_key_fingerprint);
-					sigc->primary_key_fingerprint = xmemdupz(line, next - line);
+					if (j == 0) {
+						next = strchrnul(line, '\n');
+						free(sigc->primary_key_fingerprint);
+						sigc->primary_key_fingerprint =
+							xmemdupz(line,
+								 next - line);
+					}
 				}
 
 				break;
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index e803ba402e..5d893b3137 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1580,6 +1580,12 @@ test_expect_success GPGSM 'setup signed branch x509' '
 	git commit -S -m signed_commit
 '
 
+test_expect_success GPGSM 'log x509 fingerprint' '
+	echo "F8BF62E0693D0694816377099909C779FA23FD65 | " >expect &&
+	git log -n1 --format="%GF | %GP" signed-x509 >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success GPG 'log --graph --show-signature' '
 	git log --graph --show-signature -n1 signed >actual &&
 	grep "^| gpg: Signature made" actual &&
-- 
2.24.0.156.g69483321b9.dirty