Merge branch 'mg/gpg-parse-tighten'

Detect and reject a signature block that has more than one GPG
signature.

* mg/gpg-parse-tighten:
  gpg-interface.c: detect and reject multiple signatures on commits

diff --git a/gpg-interface.c b/gpg-interface.c
index db17d65f8ac977ddc5204130cb0af6a7565ae04b..d72a43b7748c470d82150776291c5a6a91857cd5 100644 (file)
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -75,48 +75,80 @@ void signature_check_clear(struct signature_check *sigc)
        FREE_AND_NULL(sigc->key);
 }
 
+/* An exclusive status -- only one of them can appear in output */
+#define GPG_STATUS_EXCLUSIVE   (1<<0)
+
 static struct {
        char result;
        const char *check;
+       unsigned int flags;
 } sigcheck_gpg_status[] = {
-       { 'G', "\n[GNUPG:] GOODSIG " },
-       { 'B', "\n[GNUPG:] BADSIG " },
-       { 'U', "\n[GNUPG:] TRUST_NEVER" },
-       { 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
-       { 'E', "\n[GNUPG:] ERRSIG "},
-       { 'X', "\n[GNUPG:] EXPSIG "},
-       { 'Y', "\n[GNUPG:] EXPKEYSIG "},
-       { 'R', "\n[GNUPG:] REVKEYSIG "},
+       { 'G', "GOODSIG ", GPG_STATUS_EXCLUSIVE },
+       { 'B', "BADSIG ", GPG_STATUS_EXCLUSIVE },
+       { 'U', "TRUST_NEVER", 0 },
+       { 'U', "TRUST_UNDEFINED", 0 },
+       { 'E', "ERRSIG ", GPG_STATUS_EXCLUSIVE },
+       { 'X', "EXPSIG ", GPG_STATUS_EXCLUSIVE },
+       { 'Y', "EXPKEYSIG ", GPG_STATUS_EXCLUSIVE },
+       { 'R', "REVKEYSIG ", GPG_STATUS_EXCLUSIVE },
 };
 
 static void parse_gpg_output(struct signature_check *sigc)
 {
        const char *buf = sigc->gpg_status;
+       const char *line, *next;
        int i;
-
-       /* Iterate over all search strings */
-       for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
-               const char *found, *next;
-
-               if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
-                       found = strstr(buf, sigcheck_gpg_status[i].check);
-                       if (!found)
-                               continue;
-                       found += strlen(sigcheck_gpg_status[i].check);
-               }
-               sigc->result = sigcheck_gpg_status[i].result;
-               /* The trust messages are not followed by key/signer information */
-               if (sigc->result != 'U') {
-                       next = strchrnul(found, ' ');
-                       sigc->key = xmemdupz(found, next - found);
-                       /* The ERRSIG message is not followed by signer information */
-                       if (*next && sigc-> result != 'E') {
-                               found = next + 1;
-                               next = strchrnul(found, '\n');
-                               sigc->signer = xmemdupz(found, next - found);
+       int seen_exclusive_status = 0;
+
+       /* Iterate over all lines */
+       for (line = buf; *line; line = strchrnul(line+1, '\n')) {
+               while (*line == '\n')
+                       line++;
+               /* Skip lines that don't start with GNUPG status */
+               if (!skip_prefix(line, "[GNUPG:] ", &line))
+                       continue;
+
+               /* Iterate over all search strings */
+               for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
+                       if (skip_prefix(line, sigcheck_gpg_status[i].check, &line)) {
+                               if (sigcheck_gpg_status[i].flags & GPG_STATUS_EXCLUSIVE) {
+                                       if (seen_exclusive_status++)
+                                               goto found_duplicate_status;
+                               }
+
+                               sigc->result = sigcheck_gpg_status[i].result;
+                               /* The trust messages are not followed by key/signer information */
+                               if (sigc->result != 'U') {
+                                       next = strchrnul(line, ' ');
+                                       free(sigc->key);
+                                       sigc->key = xmemdupz(line, next - line);
+                                       /* The ERRSIG message is not followed by signer information */
+                                       if (*next && sigc->result != 'E') {
+                                               line = next + 1;
+                                               next = strchrnul(line, '\n');
+                                               free(sigc->signer);
+                                               sigc->signer = xmemdupz(line, next - line);
+                                       }
+                               }
+
+                               break;
                        }
                }
        }
+       return;
+
+found_duplicate_status:
+       /*
+        * GOODSIG, BADSIG etc. can occur only once for each signature.
+        * Therefore, if we had more than one then we're dealing with multiple
+        * signatures.  We don't support them currently, and they're rather
+        * hard to create, so something is likely fishy and we should reject
+        * them altogether.
+        */
+       sigc->result = 'E';
+       /* Clear partial data to avoid confusion */
+       FREE_AND_NULL(sigc->signer);
+       FREE_AND_NULL(sigc->key);
 }
 
 int check_signature(const char *payload, size_t plen, const char *signature,

diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 4e37ff8f169615a893ee5d0594ff056b0284b724..180f0be9149ffa2e5fed83172a782e57229cff24 100755 (executable)
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -234,4 +234,30 @@ test_expect_success GPG 'check config gpg.format values' '
        test_must_fail git commit -S --amend -m "fail"
 '
 
+test_expect_success GPG 'detect fudged commit with double signature' '
+       sed -e "/gpgsig/,/END PGP/d" forged1 >double-base &&
+       sed -n -e "/gpgsig/,/END PGP/p" forged1 | \
+               sed -e "s/^gpgsig//;s/^ //" | gpg --dearmor >double-sig1.sig &&
+       gpg -o double-sig2.sig -u 29472784 --detach-sign double-base &&
+       cat double-sig1.sig double-sig2.sig | gpg --enarmor >double-combined.asc &&
+       sed -e "s/^\(-.*\)ARMORED FILE/\1SIGNATURE/;1s/^/gpgsig /;2,\$s/^/ /" \
+               double-combined.asc > double-gpgsig &&
+       sed -e "/committer/r double-gpgsig" double-base >double-commit &&
+       git hash-object -w -t commit double-commit >double-commit.commit &&
+       test_must_fail git verify-commit $(cat double-commit.commit) &&
+       git show --pretty=short --show-signature $(cat double-commit.commit) >double-actual &&
+       grep "BAD signature from" double-actual &&
+       grep "Good signature from" double-actual
+'
+
+test_expect_success GPG 'show double signature with custom format' '
+       cat >expect <<-\EOF &&
+       E
+
+
+       EOF
+       git log -1 --format="%G?%n%GK%n%GS" $(cat double-commit.commit) >actual &&
+       test_cmp expect actual
+'
+
 test_done