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: four lines
   6 * of "object <sha1>" + "type <typename>" + "tag <tagname>" +
   7 * "tagger <committer>", followed by a blank line, a free-form tag
   8 * message and a signature block that git itself doesn't care about,
   9 * but that can be verified with gpg or similar.
  10 *
  11 * The first three lines are guaranteed to be at least 63 bytes:
  12 * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
  13 * shortest possible type-line, and "tag .\n" at 6 bytes is the
  14 * shortest single-character-tag line. 
  15 *
  16 * We also artificially limit the size of the full object to 8kB.
  17 * Just because I'm a lazy bastard, and if you can't fit a signature
  18 * in that size, you're doing something wrong.
  19 */
  20
  21/* Some random size */
  22#define MAXSIZE (8192)
  23
  24/*
  25 * We refuse to tag something we can't verify. Just because.
  26 */
  27static int verify_object(unsigned char *sha1, const char *expected_type)
  28{
  29        int ret = -1;
  30        enum object_type type;
  31        unsigned long size;
  32        void *buffer = read_sha1_file(sha1, &type, &size);
  33
  34        if (buffer) {
  35                if (type == type_from_string(expected_type))
  36                        ret = check_sha1_signature(sha1, buffer, size, expected_type);
  37                free(buffer);
  38        }
  39        return ret;
  40}
  41
  42#ifdef NO_C99_FORMAT
  43#define PD_FMT "%d"
  44#else
  45#define PD_FMT "%td"
  46#endif
  47
  48static int verify_tag(char *buffer, unsigned long size)
  49{
  50        int typelen;
  51        char type[20];
  52        unsigned char sha1[20];
  53        const char *object, *type_line, *tag_line, *tagger_line;
  54
  55        if (size < 64)
  56                return error("wanna fool me ? you obviously got the size wrong !");
  57
  58        buffer[size] = 0;
  59
  60        /* Verify object line */
  61        object = buffer;
  62        if (memcmp(object, "object ", 7))
  63                return error("char%d: does not start with \"object \"", 0);
  64
  65        if (get_sha1_hex(object + 7, sha1))
  66                return error("char%d: could not get SHA1 hash", 7);
  67
  68        /* Verify type line */
  69        type_line = object + 48;
  70        if (memcmp(type_line - 1, "\ntype ", 6))
  71                return error("char%d: could not find \"\\ntype \"", 47);
  72
  73        /* Verify tag-line */
  74        tag_line = strchr(type_line, '\n');
  75        if (!tag_line)
  76                return error("char" PD_FMT ": could not find next \"\\n\"", type_line - buffer);
  77        tag_line++;
  78        if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  79                return error("char" PD_FMT ": no \"tag \" found", tag_line - buffer);
  80
  81        /* Get the actual type */
  82        typelen = tag_line - type_line - strlen("type \n");
  83        if (typelen >= sizeof(type))
  84                return error("char" PD_FMT ": type too long", type_line+5 - buffer);
  85
  86        memcpy(type, type_line+5, typelen);
  87        type[typelen] = 0;
  88
  89        /* Verify that the object matches */
  90        if (verify_object(sha1, type))
  91                return error("char%d: could not verify object %s", 7, sha1_to_hex(sha1));
  92
  93        /* Verify the tag-name: we don't allow control characters or spaces in it */
  94        tag_line += 4;
  95        for (;;) {
  96                unsigned char c = *tag_line++;
  97                if (c == '\n')
  98                        break;
  99                if (c > ' ')
 100                        continue;
 101                return error("char" PD_FMT ": could not verify tag name", tag_line - buffer);
 102        }
 103
 104        /* Verify the tagger line */
 105        tagger_line = tag_line;
 106
 107        if (memcmp(tagger_line, "tagger", 6) || (tagger_line[6] == '\n'))
 108                return error("char" PD_FMT ": could not find \"tagger\"", tagger_line - buffer);
 109
 110        /* TODO: check for committer info + blank line? */
 111        /* Also, the minimum length is probably + "tagger .", or 63+8=71 */
 112
 113        /* The actual stuff afterwards we don't care about.. */
 114        return 0;
 115}
 116
 117#undef PD_FMT
 118
 119int main(int argc, char **argv)
 120{
 121        unsigned long size = 4096;
 122        char *buffer = xmalloc(size);
 123        unsigned char result_sha1[20];
 124
 125        if (argc != 1)
 126                usage("git-mktag < signaturefile");
 127
 128        setup_git_directory();
 129
 130        if (read_pipe(0, &buffer, &size)) {
 131                free(buffer);
 132                die("could not read from stdin");
 133        }
 134
 135        /* Verify it for some basic sanity: it needs to start with
 136           "object <sha1>\ntype\ntagger " */
 137        if (verify_tag(buffer, size) < 0)
 138                die("invalid tag signature file");
 139
 140        if (write_sha1_file(buffer, size, tag_type, result_sha1) < 0)
 141                die("unable to write tag file");
 142
 143        free(buffer);
 144
 145        printf("%s\n", sha1_to_hex(result_sha1));
 146        return 0;
 147}