1 files changed, 174 insertions, 0 deletions
diff --git a/builtin/mktag.c b/builtin/mktag.c
new file mode 100644
index 0000000000..324a267163
--- /dev/null
+++ b/builtin/mktag.c
@@ -0,0 +1,174 @@
+#include "builtin.h"
+#include "tag.h"
+
+/*
+ * A signature file has a very simple fixed format: four lines
+ * of "object <sha1>" + "type <typename>" + "tag <tagname>" +
+ * "tagger <committer>", followed by a blank line, a free-form tag
+ * message and a signature block that git itself doesn't care about,
+ * but that can be verified with gpg or similar.
+ *
+ * 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, "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.
+ */
+
+/*
+ * We refuse to tag something we can't verify. Just because.
+ */
+static int verify_object(const unsigned char *sha1, const char *expected_type)
+{
+	int ret = -1;
+	enum object_type type;
+	unsigned long size;
+	const unsigned char *repl;
+	void *buffer = read_sha1_file_repl(sha1, &type, &size, &repl);
+
+	if (buffer) {
+		if (type == type_from_string(expected_type))
+			ret = check_sha1_signature(repl, buffer, size, expected_type);
+		free(buffer);
+	}
+	return ret;
+}
+
+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, *lb, *rb;
+	size_t len;
+
+	if (size < 84)
+		return error("wanna fool me ? you obviously got the size wrong !");
+
+	buffer[size] = 0;
+
+	/* Verify object line */
+	object = buffer;
+	if (memcmp(object, "object ", 7))
+		return error("char%d: does not start with \"object \"", 0);
+
+	if (get_sha1_hex(object + 7, sha1))
+		return error("char%d: could not get SHA1 hash", 7);
+
+	/* Verify type line */
+	type_line = object + 48;
+	if (memcmp(type_line - 1, "\ntype ", 6))
+		return error("char%d: could not find \"\\ntype \"", 47);
+
+	/* Verify tag-line */
+	tag_line = strchr(type_line, '\n');
+	if (!tag_line)
+		return error("char%"PRIuMAX": could not find next \"\\n\"",
+				(uintmax_t) (type_line - buffer));
+	tag_line++;
+	if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
+		return error("char%"PRIuMAX": no \"tag \" found",
+				(uintmax_t) (tag_line - buffer));
+
+	/* Get the actual type */
+	typelen = tag_line - type_line - strlen("type \n");
+	if (typelen >= sizeof(type))
+		return error("char%"PRIuMAX": type too long",
+				(uintmax_t) (type_line+5 - buffer));
+
+	memcpy(type, type_line+5, typelen);
+	type[typelen] = 0;
+
+	/* Verify that the object matches */
+	if (verify_object(sha1, type))
+		return error("char%d: could not verify object %s", 7, sha1_to_hex(sha1));
+
+	/* Verify the tag-name: we don't allow control characters or spaces in it */
+	tag_line += 4;
+	for (;;) {
+		unsigned char c = *tag_line++;
+		if (c == '\n')
+			break;
+		if (c > ' ')
+			continue;
+		return error("char%"PRIuMAX": could not verify tag name",
+				(uintmax_t) (tag_line - buffer));
+	}
+
+	/* Verify the tagger line */
+	tagger_line = tag_line;
+
+	if (memcmp(tagger_line, "tagger ", 7))
+		return error("char%"PRIuMAX": could not find \"tagger \"",
+			(uintmax_t) (tagger_line - buffer));
+
+	/*
+	 * Check for correct form for name and email
+	 * i.e. " <" followed by "> " on _this_ line
+	 * No angle brackets within the name or email address fields.
+	 * No spaces within the email address field.
+	 */
+	tagger_line += 7;
+	if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
+		strpbrk(tagger_line, "<>\n") != lb+1 ||
+		strpbrk(lb+2, "><\n ") != rb)
+		return error("char%"PRIuMAX": malformed tagger field",
+			(uintmax_t) (tagger_line - buffer));
+
+	/* Check for author name, at least one character, space is acceptable */
+	if (lb == tagger_line)
+		return error("char%"PRIuMAX": missing tagger name",
+			(uintmax_t) (tagger_line - buffer));
+
+	/* timestamp, 1 or more digits followed by space */
+	tagger_line = rb + 2;
+	if (!(len = strspn(tagger_line, "0123456789")))
+		return error("char%"PRIuMAX": missing tag timestamp",
+			(uintmax_t) (tagger_line - buffer));
+	tagger_line += len;
+	if (*tagger_line != ' ')
+		return error("char%"PRIuMAX": malformed tag timestamp",
+			(uintmax_t) (tagger_line - buffer));
+	tagger_line++;
+
+	/* timezone, 5 digits [+-]hhmm, max. 1400 */
+	if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
+	      strspn(tagger_line+1, "0123456789") == 4 &&
+	      tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
+		return error("char%"PRIuMAX": malformed tag timezone",
+			(uintmax_t) (tagger_line - buffer));
+	tagger_line += 6;
+
+	/* Verify the blank line separating the header from the body */
+	if (*tagger_line != '\n')
+		return error("char%"PRIuMAX": trailing garbage in tag header",
+			(uintmax_t) (tagger_line - buffer));
+
+	/* The actual stuff afterwards we don't care about.. */
+	return 0;
+}
+
+int cmd_mktag(int argc, const char **argv, const char *prefix)
+{
+	struct strbuf buf = STRBUF_INIT;
+	unsigned char result_sha1[20];
+
+	if (argc != 1)
+		usage("git mktag < signaturefile");
+
+	if (strbuf_read(&buf, 0, 4096) < 0) {
+		die_errno("could not read from stdin");
+	}
+
+	/* Verify it for some basic sanity: it needs to start with
+	   "object <sha1>\ntype\ntagger " */
+	if (verify_tag(buf.buf, buf.len) < 0)
+		die("invalid tag signature file");
+
+	if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
+		die("unable to write tag file");
+
+	strbuf_release(&buf);
+	printf("%s\n", sha1_to_hex(result_sha1));
+	return 0;
+}