Andrew's git - gitweb.git/blob

   1#include "cache.h"
   2#include "tag.h"
   3
   4/*
   5 * A signature file has a very simple fixed format: three lines
   6 * of "object <sha1>" + "type <typename>" + "tag <tagname>",
   7 * followed by some free-form signature that git itself doesn't
   8 * care about, but that can be verified with gpg or similar.
   9 *
  10 * The first three lines are guaranteed to be at least 63 bytes:
  11 * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
  12 * shortest possible type-line, and "tag .\n" at 6 bytes is the
  13 * shortest single-character-tag line. 
  14 *
  15 * We also artificially limit the size of the full object to 8kB.
  16 * Just because I'm a lazy bastard, and if you can't fit a signature
  17 * in that size, you're doing something wrong.
  18 */
  19
  20// Some random size
  21#define MAXSIZE (8192)
  22
  23/*
  24 * We refuse to tag something we can't verify. Just because.
  25 */
  26static int verify_object(unsigned char *sha1, const char *expected_type)
  27{
  28        int ret = -1;
  29        char type[100];
  30        unsigned long size;
  31        void *buffer = read_sha1_file(sha1, type, &size);
  32
  33        if (buffer) {
  34                if (!strcmp(type, expected_type))
  35                        ret = check_sha1_signature(sha1, buffer, size, type);
  36                free(buffer);
  37        }
  38        return ret;
  39}
  40
  41static int verify_tag(char *buffer, unsigned long size)
  42{
  43        int typelen;
  44        char type[20];
  45        unsigned char sha1[20];
  46        const char *object, *type_line, *tag_line, *tagger_line;
  47
  48        if (size < 64 || size > MAXSIZE-1)
  49                return -1;
  50        buffer[size] = 0;
  51
  52        /* Verify object line */
  53        object = buffer;
  54        if (memcmp(object, "object ", 7))
  55                return -1;
  56        if (get_sha1_hex(object + 7, sha1))
  57                return -1;
  58
  59        /* Verify type line */
  60        type_line = object + 48;
  61        if (memcmp(type_line - 1, "\ntype ", 6))
  62                return -1;
  63
  64        /* Verify tag-line */
  65        tag_line = strchr(type_line, '\n');
  66        if (!tag_line)
  67                return -1;
  68        tag_line++;
  69        if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  70                return -1;
  71
  72        /* Get the actual type */
  73        typelen = tag_line - type_line - strlen("type \n");
  74        if (typelen >= sizeof(type))
  75                return -1;
  76        memcpy(type, type_line+5, typelen);
  77        type[typelen] = 0;
  78
  79        /* Verify that the object matches */
  80        if (get_sha1_hex(object + 7, sha1))
  81                return -1;
  82        if (verify_object(sha1, type))
  83                return -1;
  84
  85        /* Verify the tag-name: we don't allow control characters or spaces in it */
  86        tag_line += 4;
  87        for (;;) {
  88                unsigned char c = *tag_line++;
  89                if (c == '\n')
  90                        break;
  91                if (c > ' ')
  92                        continue;
  93                return -1;
  94        }
  95
  96        /* Verify the tagger line */
  97        tagger_line = tag_line;
  98
  99        if (memcmp(tagger_line, "tagger", 6) || (tagger_line[6] == '\n'))
 100                return -1;
 101
 102        /* The actual stuff afterwards we don't care about.. */
 103        return 0;
 104}
 105
 106int main(int argc, char **argv)
 107{
 108        unsigned long size;
 109        char buffer[MAXSIZE];
 110        unsigned char result_sha1[20];
 111
 112        if (argc != 1)
 113                usage("cat <signaturefile> | git-mktag");
 114
 115        setup_git_directory();
 116
 117        // Read the signature
 118        size = 0;
 119        for (;;) {
 120                int ret = xread(0, buffer + size, MAXSIZE - size);
 121                if (ret <= 0)
 122                        break;
 123                size += ret;
 124        }
 125
 126        // Verify it for some basic sanity: it needs to start with "object <sha1>\ntype\ntagger "
 127        if (verify_tag(buffer, size) < 0)
 128                die("invalid tag signature file");
 129
 130        if (write_sha1_file(buffer, size, tag_type, result_sha1) < 0)
 131                die("unable to write tag file");
 132        printf("%s\n", sha1_to_hex(result_sha1));
 133        return 0;
 134}