get-tar-commit-id: parse comment record

rscharfe · gitster · commit 3548726cd7f5 · 2019-04-01T11:57:39.000+09:00
Parse pax comment records properly and get rid of magic numbers for
acceptable comment length.  This simplifies a later change to handle
longer hashes.

Signed-off-by: Rene Scharfe &lt;l.s.r@web.de&gt;
Signed-off-by: brian m. carlson &lt;sandals@crustytoothpaste.net&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/builtin/get-tar-commit-id.c b/builtin/get-tar-commit-id.c
@@ -21,6 +21,8 @@ int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
 	char *content = buffer + RECORDSIZE;
 	const char *comment;
 	ssize_t n;
+	long len;
+	char *end;
 
 	if (argc != 1)
 		usage(builtin_get_tar_commit_id_usage);
@@ -32,10 +34,17 @@ int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
 		die_errno("git get-tar-commit-id: EOF before reading tar header");
 	if (header->typeflag[0] != 'g')
 		return 1;
-	if (!skip_prefix(content, "52 comment=", &comment))
+
+	len = strtol(content, &end, 10);
+	if (errno == ERANGE || end == content || len < 0)
+		return 1;
+	if (!skip_prefix(end, " comment=", &comment))
+		return 1;
+	len -= comment - content;
+	if (len != GIT_SHA1_HEXSZ + 1)
 		return 1;
 
-	if (write_in_full(1, comment, 41) < 0)
+	if (write_in_full(1, comment, len) < 0)
 		die_errno("git get-tar-commit-id: write error");
 
 	return 0;
