[PATCH] Rename and extend read_tree_with_tree_or_commit_sha1
[git/git.git] / git-mktag.c
1 #include "cache.h"
2
3 /*
4 * A signature file has a very simple fixed format: three lines
5 * of "object <sha1>" + "type <typename>" + "tag <tagname>",
6 * followed by some free-form signature that git itself doesn't
7 * care about, but that can be verified with gpg or similar.
8 *
9 * The first three lines are guaranteed to be at least 63 bytes:
10 * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
11 * shortest possible type-line, and "tag .\n" at 6 bytes is the
12 * shortest single-character-tag line.
13 *
14 * We also artificially limit the size of the full object to 8kB.
15 * Just because I'm a lazy bastard, and if you can't fit a signature
16 * in that size, you're doing something wrong.
17 */
18
19 // Some random size
20 #define MAXSIZE (8192)
21
22 /*
23 * We refuse to tag something we can't verify. Just because.
24 */
25 static int verify_object(unsigned char *sha1, const char *expected_type)
26 {
27 int ret = -1;
28 unsigned long mapsize;
29 void *map = map_sha1_file(sha1, &mapsize);
30
31 if (map) {
32 char type[100];
33 unsigned long size;
34 void *buffer = unpack_sha1_file(map, mapsize, type, &size);
35
36 if (buffer) {
37 if (!strcmp(type, expected_type))
38 ret = check_sha1_signature(sha1, buffer, size, type);
39 free(buffer);
40 }
41 munmap(map, mapsize);
42 }
43 return ret;
44 }
45
46 static int verify_tag(char *buffer, unsigned long size)
47 {
48 int typelen;
49 char type[20];
50 unsigned char sha1[20];
51 const char *object, *type_line, *tag_line;
52
53 if (size < 64 || size > MAXSIZE-1)
54 return -1;
55 buffer[size] = 0;
56
57 /* Verify object line */
58 object = buffer;
59 if (memcmp(object, "object ", 7))
60 return -1;
61 if (get_sha1_hex(object + 7, sha1))
62 return -1;
63
64 /* Verify type line */
65 type_line = object + 48;
66 if (memcmp(type_line - 1, "\ntype ", 6))
67 return -1;
68
69 /* Verify tag-line */
70 tag_line = strchr(type_line, '\n');
71 if (!tag_line)
72 return -1;
73 tag_line++;
74 if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
75 return -1;
76
77 /* Get the actual type */
78 typelen = tag_line - type_line - strlen("type \n");
79 if (typelen >= sizeof(type))
80 return -1;
81 memcpy(type, type_line+5, typelen);
82 type[typelen] = 0;
83
84 /* Verify that the object matches */
85 if (get_sha1_hex(object + 7, sha1))
86 return -1;
87 if (verify_object(sha1, type))
88 return -1;
89
90 /* Verify the tag-name: we don't allow control characters or spaces in it */
91 tag_line += 4;
92 for (;;) {
93 unsigned char c = *tag_line++;
94 if (c == '\n')
95 break;
96 if (c > ' ')
97 continue;
98 return -1;
99 }
100
101 /* The actual stuff afterwards we don't care about.. */
102 return 0;
103 }
104
105 int main(int argc, char **argv)
106 {
107 unsigned long size;
108 char buffer[MAXSIZE];
109 unsigned char result_sha1[20];
110
111 if (argc != 1)
112 usage("cat <signaturefile> | git-mktag");
113
114 // Read the signature
115 size = read(0, buffer, MAXSIZE);
116
117 // Verify it for some basic sanity: it needs to start with "object <sha1>\ntype "
118 if (verify_tag(buffer, size) < 0)
119 die("invalid tag signature file");
120
121 if (write_sha1_file(buffer, size, "tag", result_sha1) < 0)
122 die("unable to write tag file");
123 printf("%s\n", sha1_to_hex(result_sha1));
124 return 0;
125 }