gpg-interface: remove other signature headers before verifying

When we have a multiply signed commit, we need to remove the signature
in the header before verifying the object, since the trailing signature
will not be over both pieces of data.  Do so, and verify that we
validate the signature appropriately.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/gpg-interface.c b/gpg-interface.c
index c6274c14af435b593ba928f9ca7b8bbec96bc28e..127aecfc2b071f9a745a871a9ea205931eeb672f 100644 (file)
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "commit.h"
 #include "config.h"
 #include "run-command.h"
 #include "strbuf.h"
@@ -366,6 +367,7 @@ int parse_signature(const char *buf, size_t size, struct strbuf *payload, struct
        size_t match = parse_signed_buffer(buf, size);
        if (match != size) {
                strbuf_add(payload, buf, match);
+               remove_signature(payload);
                strbuf_add(signature, buf + match, size - match);
                return 1;
        }

diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index 05f411c82130e644a15782896f95ea41bba6f6c8..6fb4e3cf11bee2b9fe95d6db0c04ffa56c0d0176 100755 (executable)
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -17,6 +17,13 @@ tag_exists () {
        git show-ref --quiet --verify refs/tags/"$1"
 }
 
+test_expect_success 'setup' '
+       test_oid_cache <<-EOM
+       othersigheader sha1:gpgsig-sha256
+       othersigheader sha256:gpgsig
+       EOM
+'
+
 test_expect_success 'listing all tags in an empty tree should succeed' '
        git tag -l &&
        git tag
@@ -1371,6 +1378,24 @@ test_expect_success GPG \
        'test_config gpg.program echo &&
         test_must_fail git tag -s -m tail tag-gpg-failure'
 
+# try to produce invalid signature
+test_expect_success GPG 'git verifies tag is valid with double signature' '
+       git tag -s -m tail tag-gpg-double-sig &&
+       git cat-file tag tag-gpg-double-sig >tag &&
+       othersigheader=$(test_oid othersigheader) &&
+       sed -ne "/^\$/q;p" tag >new-tag &&
+       cat <<-EOM >>new-tag &&
+       $othersigheader -----BEGIN PGP SIGNATURE-----
+        someinvaliddata
+        -----END PGP SIGNATURE-----
+       EOM
+       sed -e "1,/^tagger/d" tag >>new-tag &&
+       new_tag=$(git hash-object -t tag -w new-tag) &&
+       git update-ref refs/tags/tag-gpg-double-sig $new_tag &&
+       git verify-tag tag-gpg-double-sig &&
+       git fsck
+'
+
 # try to sign with bad user.signingkey
 test_expect_success GPGSM \
        'git tag -s fails if gpgsm is misconfigured (bad key)' \