mktag.c: improve verification of tagger field and tests

Since nearly its birth, git's tags have included a "tagger" field which
describes the name of tagger, email of tagger, and date and time of tagging.
But, this field was only loosely tested by git-mktag. Provide some thorough
testing for this field and also ensure that the tag header is separated
from the tag body by an empty line to reduce the convenience of creating
a flawed tag.

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

mktag.c

@@ -8,10 +8,11 @@
  * message and a signature block that git itself doesn't care about,
  * but that can be verified with gpg or similar.
  *
- * The first three lines are guaranteed to be at least 63 bytes:
+ * The first four lines are guaranteed to be at least 83 bytes:
  * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
- * shortest possible type-line, and "tag .\n" at 6 bytes is the
- * shortest single-character-tag line.
+ * shortest possible type-line, "tag .\n" at 6 bytes is the shortest
+ * single-character-tag line, and "tagger . <> 0 +0000\n" at 20 bytes is
+ * the shortest possible tagger-line.
  */
 
 /*
@@ -43,9 +44,9 @@ static int verify_tag(char *buffer, unsigned long size)
 	int typelen;
 	char type[20];
 	unsigned char sha1[20];
-	const char *object, *type_line, *tag_line, *tagger_line;
+	const char *object, *type_line, *tag_line, *tagger_line, *lb, *rb;
 
-	if (size < 64)
+	if (size < 84)
 		return error("wanna fool me ? you obviously got the size wrong !");
 
 	buffer[size] = 0;
@@ -97,11 +98,53 @@ static int verify_tag(char *buffer, unsigned long size)
 	/* Verify the tagger line */
 	tagger_line = tag_line;
 
-	if (memcmp(tagger_line, "tagger", 6) || (tagger_line[6] == '\n'))
-		return error("char" PD_FMT ": could not find \"tagger\"", tagger_line - buffer);
+	if (memcmp(tagger_line, "tagger ", 7) || (tagger_line[7] == '\n'))
+		return error("char" PD_FMT ": could not find \"tagger \"",
+			tagger_line - buffer);
 
-	/* TODO: check for committer info + blank line? */
-	/* Also, the minimum length is probably + "tagger .", or 63+8=71 */
+	/*
+	 * Check for correct form for name and email
+	 * i.e. " <" followed by "> " on _this_ line
+	 */
+	tagger_line += 7;
+	if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
+		strchr(tagger_line, '\n') < rb)
+		return error("char" PD_FMT ": malformed tagger",
+			tagger_line - buffer);
+
+	/* Check for author name, at least one character, space is acceptable */
+	if (lb == tagger_line)
+		return error("char" PD_FMT ": missing tagger name",
+			tagger_line - buffer);
+
+	/* timestamp */
+	tagger_line = rb + 2;
+	if (*tagger_line == ' ')
+		return error("char" PD_FMT ": malformed tag timestamp",
+			tagger_line - buffer);
+	for (;;) {
+		unsigned char c = *tagger_line++;
+		if (c == ' ')
+			break;
+		if (isdigit(c))
+			continue;
+		return error("char" PD_FMT ": malformed tag timestamp",
+			tagger_line - buffer);
+	}
+
+	/* timezone, 5 digits [+-]hhmm, max. 1400 */
+	if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
+	      isdigit(tagger_line[1]) && isdigit(tagger_line[2]) &&
+	      isdigit(tagger_line[3]) && isdigit(tagger_line[4]) &&
+	      tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
+		return error("char" PD_FMT ": malformed tag timezone",
+			tagger_line - buffer);
+	tagger_line += 6;
+
+	/* Verify the blank line separating the header from the body */
+	if (*tagger_line != '\n')
+		return error("char" PD_FMT ": trailing garbage in tag header",
+			tagger_line - buffer);
 
 	/* The actual stuff afterwards we don't care about.. */
 	return 0;

t/t3800-mktag.sh

@@ -44,6 +44,8 @@ cat >tag.sig <<EOF
 xxxxxx 139e9b33986b1c2670fff52c5067603117b3e895
 type tag
 tag mytag
+tagger . <> 0 +0000
+
 EOF
 
 check_verify_failure '"object" line label check' '^error: char0: .*"object "$'
@@ -55,6 +57,8 @@ cat >tag.sig <<EOF
 object zz9e9b33986b1c2670fff52c5067603117b3e895
 type tag
 tag mytag
+tagger . <> 0 +0000
+
 EOF
 
 check_verify_failure '"object" line SHA1 check' '^error: char7: .*SHA1 hash$'
@@ -66,6 +70,8 @@ cat >tag.sig <<EOF
 object 779e9b33986b1c2670fff52c5067603117b3e895
 xxxx tag
 tag mytag
+tagger . <> 0 +0000
+
 EOF
 
 check_verify_failure '"type" line label check' '^error: char47: .*"\\ntype "$'
@@ -85,6 +91,8 @@ cat >tag.sig <<EOF
 object 779e9b33986b1c2670fff52c5067603117b3e895
 type tag
 xxx mytag
+tagger . <> 0 +0000
+
 EOF
 
 check_verify_failure '"tag" line label check #1' \
@@ -121,6 +129,8 @@ cat >tag.sig <<EOF
 object 779e9b33986b1c2670fff52c5067603117b3e895
 type tagggg
 tag mytag
+tagger . <> 0 +0000
+
 EOF
 
 check_verify_failure 'verify object (SHA1/type) check' \
@@ -133,6 +143,8 @@ cat >tag.sig <<EOF
 object $head
 type commit
 tag my	tag
+tagger . <> 0 +0000
+
 EOF
 
 check_verify_failure 'verify tag-name check' \
@@ -145,6 +157,8 @@ cat >tag.sig <<EOF
 object $head
 type commit
 tag mytag
+
+This is filler
 EOF
 
 check_verify_failure '"tagger" line label check #1' \
@@ -158,19 +172,124 @@ object $head
 type commit
 tag mytag
 tagger
+
+This is filler
 EOF
 
 check_verify_failure '"tagger" line label check #2' \
 	'^error: char70: could not find "tagger "$'
 
 ############################################################
-# 13. create valid tag
+# 13. detect missing tag author name
 
 cat >tag.sig <<EOF
 object $head
 type commit
 tag mytag
-tagger another@example.com
+tagger  <> 0 +0000
+
+This is filler
+EOF
+
+check_verify_failure 'detect missing tag author name' \
+	'^error: char77: missing tagger name$'
+
+############################################################
+# 14. detect missing tag author name
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <
+ > 0 +0000
+
+EOF
+
+check_verify_failure 'detect malformed tagger' \
+	'^error: char77: malformed tagger$'
+
+############################################################
+# 15. allow empty tag email
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <> 0 +0000
+
+EOF
+
+test_expect_success \
+    'allow empty tag email' \
+    'git-mktag <tag.sig >.git/refs/tags/mytag 2>message'
+
+############################################################
+# 16. detect missing tag timestamp
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com>  
+
+EOF
+
+check_verify_failure 'detect missing tag timestamp' \
+	'^error: char107: malformed tag timestamp$'
+
+############################################################
+# 17. detect invalid tag timestamp
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> Tue Mar 25 15:47:44 2008
+
+EOF
+
+check_verify_failure 'detect invalid tag timestamp' \
+	'^error: char108: malformed tag timestamp$'
+
+############################################################
+# 18. detect invalid tag timezone
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> 1206478233 GMT
+
+EOF
+
+check_verify_failure 'detect invalid tag timezone' \
+	'^error: char118: malformed tag timezone$'
+
+############################################################
+# 19. detect invalid header entry
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> 1206478233 -0500
+this line should not be here
+
+EOF
+
+check_verify_failure 'detect invalid header entry' \
+	'^error: char124: trailing garbage in tag header$'
+
+############################################################
+# 20. create valid tag
+
+cat >tag.sig <<EOF
+object $head
+type commit
+tag mytag
+tagger T A Gger <tagger@example.com> 1206478233 -0500
+
 EOF
 
 test_expect_success \
@@ -178,7 +297,7 @@ test_expect_success \
     'git-mktag <tag.sig >.git/refs/tags/mytag 2>message'
 
 ############################################################
-# 14. check mytag
+# 21. check mytag
 
 test_expect_success \
     'check mytag' \