Andrew's git - gitweb.git/blob

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