aboutsummaryrefslogtreecommitdiff
path: root/mktag.c
blob: 931011121e7276513b55fc41691c65a0d924119d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
#include "cache.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 three lines are guaranteed to be at least 63 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. 
 *
 * We also artificially limit the size of the full object to 8kB.
 * Just because I'm a lazy bastard, and if you can't fit a signature
 * in that size, you're doing something wrong.
 */

/* Some random size */
#define MAXSIZE (8192)

/*
 * We refuse to tag something we can't verify. Just because.
 */
static int verify_object(unsigned char *sha1, const char *expected_type)
{
	int ret = -1;
	enum object_type type;
	unsigned long size;
	void *buffer = read_sha1_file(sha1, &type, &size);

	if (buffer) {
		if (type == type_from_string(expected_type))
			ret = check_sha1_signature(sha1, buffer, size, expected_type);
		free(buffer);
	}
	return ret;
}

#ifdef NO_C99_FORMAT
#define PD_FMT "%d"
#else
#define PD_FMT "%td"
#endif

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;

	if (size < 64)
		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" PD_FMT ": could not find next \"\\n\"", type_line - buffer);
	tag_line++;
	if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
		return error("char" PD_FMT ": no \"tag \" found", tag_line - buffer);

	/* Get the actual type */
	typelen = tag_line - type_line - strlen("type \n");
	if (typelen >= sizeof(type))
		return error("char" PD_FMT ": type too long", 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" PD_FMT ": could not verify tag name", tag_line - buffer);
	}

	/* 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);

	/* TODO: check for committer info + blank line? */
	/* Also, the minimum length is probably + "tagger .", or 63+8=71 */

	/* The actual stuff afterwards we don't care about.. */
	return 0;
}

#undef PD_FMT

int main(int argc, char **argv)
{
	unsigned long size = 4096;
	char *buffer = xmalloc(size);
	unsigned char result_sha1[20];

	if (argc != 1)
		usage("git-mktag < signaturefile");

	setup_git_directory();

	if (read_pipe(0, &buffer, &size)) {
		free(buffer);
		die("could not read from stdin");
	}

	/* Verify it for some basic sanity: it needs to start with
	   "object <sha1>\ntype\ntagger " */
	if (verify_tag(buffer, size) < 0)
		die("invalid tag signature file");

	if (write_sha1_file(buffer, size, tag_type, result_sha1) < 0)
		die("unable to write tag file");

	free(buffer);

	printf("%s\n", sha1_to_hex(result_sha1));
	return 0;
}