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)
  49                return error("wanna fool me ? you obviously got the size wrong !\n");
  50
  51        buffer[size] = 0;
  52
  53        /* Verify object line */
  54        object = buffer;
  55        if (memcmp(object, "object ", 7))
  56                return error("char%d: does not start with \"object \"\n", 0);
  57
  58        if (get_sha1_hex(object + 7, sha1))
  59                return error("char%d: could not get SHA1 hash\n", 7);
  60
  61        /* Verify type line */
  62        type_line = object + 48;
  63        if (memcmp(type_line - 1, "\ntype ", 6))
  64                return error("char%d: could not find \"\\ntype \"\n", 47);
  65
  66        /* Verify tag-line */
  67        tag_line = strchr(type_line, '\n');
  68        if (!tag_line)
  69                return error("char%td: could not find next \"\\n\"\n", type_line - buffer);
  70        tag_line++;
  71        if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  72                return error("char%td: no \"tag \" found\n", tag_line - buffer);
  73
  74        /* Get the actual type */
  75        typelen = tag_line - type_line - strlen("type \n");
  76        if (typelen >= sizeof(type))
  77                return error("char%td: type too long\n", type_line+5 - buffer);
  78
  79        memcpy(type, type_line+5, typelen);
  80        type[typelen] = 0;
  81
  82        /* Verify that the object matches */
  83        if (get_sha1_hex(object + 7, sha1))
  84                return error("char%d: could not get SHA1 hash but this is really odd since i got it before !\n", 7);
  85
  86        if (verify_object(sha1, type))
  87                return error("char%d: could not verify object %s\n", 7, sha1);
  88
  89        /* Verify the tag-name: we don't allow control characters or spaces in it */
  90        tag_line += 4;
  91        for (;;) {
  92                unsigned char c = *tag_line++;
  93                if (c == '\n')
  94                        break;
  95                if (c > ' ')
  96                        continue;
  97                return error("char%td: could not verify tag name\n", tag_line - buffer);
  98        }
  99
 100        /* Verify the tagger line */
 101        tagger_line = tag_line;
 102
 103        if (memcmp(tagger_line, "tagger", 6) || (tagger_line[6] == '\n'))
 104                return error("char%td: could not find \"tagger\"\n", tagger_line - buffer);
 105
 106        /* The actual stuff afterwards we don't care about.. */
 107        return 0;
 108}
 109
 110int main(int argc, char **argv)
 111{
 112        unsigned long size = 4096;
 113        char *buffer = malloc(size);
 114        unsigned char result_sha1[20];
 115
 116        if (argc != 1)
 117                usage("cat <signaturefile> | git-mktag");
 118
 119        setup_git_directory();
 120
 121        if (read_pipe(0, &buffer, &size)) {
 122                free(buffer);
 123                die("could not read from stdin");
 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
 133        free(buffer);
 134
 135        printf("%s\n", sha1_to_hex(result_sha1));
 136        return 0;
 137}