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ec4465ad LT |
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; | |
91d7b8af NP |
28 | char type[100]; |
29 | unsigned long size; | |
30 | void *buffer = read_sha1_file(sha1, type, &size); | |
ec4465ad | 31 | |
91d7b8af NP |
32 | if (buffer) { |
33 | if (!strcmp(type, expected_type)) | |
34 | ret = check_sha1_signature(sha1, buffer, size, type); | |
35 | free(buffer); | |
ec4465ad LT |
36 | } |
37 | return ret; | |
38 | } | |
39 | ||
40 | static int verify_tag(char *buffer, unsigned long size) | |
41 | { | |
42 | int typelen; | |
43 | char type[20]; | |
44 | unsigned char sha1[20]; | |
45 | const char *object, *type_line, *tag_line; | |
46 | ||
47 | if (size < 64 || size > MAXSIZE-1) | |
48 | return -1; | |
49 | buffer[size] = 0; | |
50 | ||
51 | /* Verify object line */ | |
52 | object = buffer; | |
53 | if (memcmp(object, "object ", 7)) | |
54 | return -1; | |
55 | if (get_sha1_hex(object + 7, sha1)) | |
56 | return -1; | |
57 | ||
58 | /* Verify type line */ | |
59 | type_line = object + 48; | |
60 | if (memcmp(type_line - 1, "\ntype ", 6)) | |
61 | return -1; | |
62 | ||
63 | /* Verify tag-line */ | |
64 | tag_line = strchr(type_line, '\n'); | |
65 | if (!tag_line) | |
66 | return -1; | |
67 | tag_line++; | |
68 | if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n') | |
69 | return -1; | |
70 | ||
71 | /* Get the actual type */ | |
72 | typelen = tag_line - type_line - strlen("type \n"); | |
73 | if (typelen >= sizeof(type)) | |
74 | return -1; | |
75 | memcpy(type, type_line+5, typelen); | |
76 | type[typelen] = 0; | |
77 | ||
78 | /* Verify that the object matches */ | |
79 | if (get_sha1_hex(object + 7, sha1)) | |
80 | return -1; | |
81 | if (verify_object(sha1, type)) | |
82 | return -1; | |
83 | ||
84 | /* Verify the tag-name: we don't allow control characters or spaces in it */ | |
85 | tag_line += 4; | |
86 | for (;;) { | |
87 | unsigned char c = *tag_line++; | |
88 | if (c == '\n') | |
89 | break; | |
90 | if (c > ' ') | |
91 | continue; | |
92 | return -1; | |
93 | } | |
94 | ||
95 | /* The actual stuff afterwards we don't care about.. */ | |
96 | return 0; | |
97 | } | |
98 | ||
99 | int main(int argc, char **argv) | |
100 | { | |
101 | unsigned long size; | |
102 | char buffer[MAXSIZE]; | |
103 | unsigned char result_sha1[20]; | |
104 | ||
105 | if (argc != 1) | |
106 | usage("cat <signaturefile> | git-mktag"); | |
107 | ||
108 | // Read the signature | |
109 | size = read(0, buffer, MAXSIZE); | |
110 | ||
40469ee9 | 111 | // Verify it for some basic sanity: it needs to start with "object <sha1>\ntype " |
ec4465ad LT |
112 | if (verify_tag(buffer, size) < 0) |
113 | die("invalid tag signature file"); | |
114 | ||
115 | if (write_sha1_file(buffer, size, "tag", result_sha1) < 0) | |
116 | die("unable to write tag file"); | |
117 | printf("%s\n", sha1_to_hex(result_sha1)); | |
118 | return 0; | |
119 | } |