Andrew's git - gitweb.git/blob

   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 */
  25static int verify_object(unsigned char *sha1, const char *expected_type)
  26{
  27        int ret = -1;
  28        char type[100];
  29        unsigned long size;
  30        void *buffer = read_sha1_file(sha1, type, &size);
  31
  32        if (buffer) {
  33                if (!strcmp(type, expected_type))
  34                        ret = check_sha1_signature(sha1, buffer, size, type);
  35                free(buffer);
  36        }
  37        return ret;
  38}
  39
  40static 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
  99int 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
 111        // Verify it for some basic sanity: it needs to start with "object <sha1>\ntype "
 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}