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
  17/*
  18 * We refuse to tag something we can't verify. Just because.
  19 */
  20static int verify_object(unsigned char *sha1, const char *expected_type)
  21{
  22        int ret = -1;
  23        enum object_type type;
  24        unsigned long size;
  25        void *buffer = read_sha1_file(sha1, &type, &size);
  26
  27        if (buffer) {
  28                if (type == type_from_string(expected_type))
  29                        ret = check_sha1_signature(sha1, buffer, size, expected_type);
  30                free(buffer);
  31        }
  32        return ret;
  33}
  34
  35#ifdef NO_C99_FORMAT
  36#define PD_FMT "%d"
  37#else
  38#define PD_FMT "%td"
  39#endif
  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 !");
  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 \"", 0);
  57
  58        if (get_sha1_hex(object + 7, sha1))
  59                return error("char%d: could not get SHA1 hash", 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 \"", 47);
  65
  66        /* Verify tag-line */
  67        tag_line = strchr(type_line, '\n');
  68        if (!tag_line)
  69                return error("char" PD_FMT ": could not find next \"\\n\"", type_line - buffer);
  70        tag_line++;
  71        if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  72                return error("char" PD_FMT ": no \"tag \" found", 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" PD_FMT ": type too long", 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 (verify_object(sha1, type))
  84                return error("char%d: could not verify object %s", 7, sha1_to_hex(sha1));
  85
  86        /* Verify the tag-name: we don't allow control characters or spaces in it */
  87        tag_line += 4;
  88        for (;;) {
  89                unsigned char c = *tag_line++;
  90                if (c == '\n')
  91                        break;
  92                if (c > ' ')
  93                        continue;
  94                return error("char" PD_FMT ": could not verify tag name", tag_line - buffer);
  95        }
  96
  97        /* Verify the tagger line */
  98        tagger_line = tag_line;
  99
 100        if (memcmp(tagger_line, "tagger", 6) || (tagger_line[6] == '\n'))
 101                return error("char" PD_FMT ": could not find \"tagger\"", tagger_line - buffer);
 102
 103        /* TODO: check for committer info + blank line? */
 104        /* Also, the minimum length is probably + "tagger .", or 63+8=71 */
 105
 106        /* The actual stuff afterwards we don't care about.. */
 107        return 0;
 108}
 109
 110#undef PD_FMT
 111
 112int main(int argc, char **argv)
 113{
 114        struct strbuf buf;
 115        unsigned char result_sha1[20];
 116
 117        if (argc != 1)
 118                usage("git-mktag < signaturefile");
 119
 120        setup_git_directory();
 121
 122        strbuf_init(&buf, 0);
 123        if (strbuf_read(&buf, 0, 4096) < 0) {
 124                die("could not read from stdin");
 125        }
 126
 127        /* Verify it for some basic sanity: it needs to start with
 128           "object <sha1>\ntype\ntagger " */
 129        if (verify_tag(buf.buf, buf.len) < 0)
 130                die("invalid tag signature file");
 131
 132        if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
 133                die("unable to write tag file");
 134
 135        strbuf_release(&buf);
 136        printf("%s\n", sha1_to_hex(result_sha1));
 137        return 0;
 138}