mktag.c

   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 four lines are guaranteed to be at least 83 bytes:
  12  * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
  13  * shortest possible type-line, "tag .\n" at 6 bytes is the shortest
  14  * single-character-tag line, and "tagger . <> 0 +0000\n" at 20 bytes is
  15  * the shortest possible tagger-line.
  16  */
  17
  18 /*
  19  * We refuse to tag something we can't verify. Just because.
  20  */
  21 static 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
  42 static 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, *lb, *rb;
  48         size_t len;
  49
  50         if (size < 84)
  51                 return error("wanna fool me ? you obviously got the size wrong !");
  52
  53         buffer[size] = 0;
  54
  55         /* Verify object line */
  56         object = buffer;
  57         if (memcmp(object, "object ", 7))
  58                 return error("char%d: does not start with \"object \"", 0);
  59
  60         if (get_sha1_hex(object + 7, sha1))
  61                 return error("char%d: could not get SHA1 hash", 7);
  62
  63         /* Verify type line */
  64         type_line = object + 48;
  65         if (memcmp(type_line - 1, "\ntype ", 6))
  66                 return error("char%d: could not find \"\\ntype \"", 47);
  67
  68         /* Verify tag-line */
  69         tag_line = strchr(type_line, '\n');
  70         if (!tag_line)
  71                 return error("char" PD_FMT ": could not find next \"\\n\"", type_line - buffer);
  72         tag_line++;
  73         if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  74                 return error("char" PD_FMT ": no \"tag \" found", tag_line - buffer);
  75
  76         /* Get the actual type */
  77         typelen = tag_line - type_line - strlen("type \n");
  78         if (typelen >= sizeof(type))
  79                 return error("char" PD_FMT ": type too long", type_line+5 - buffer);
  80
  81         memcpy(type, type_line+5, typelen);
  82         type[typelen] = 0;
  83
  84         /* Verify that the object matches */
  85         if (verify_object(sha1, type))
  86                 return error("char%d: could not verify object %s", 7, sha1_to_hex(sha1));
  87
  88         /* Verify the tag-name: we don't allow control characters or spaces in it */
  89         tag_line += 4;
  90         for (;;) {
  91                 unsigned char c = *tag_line++;
  92                 if (c == '\n')
  93                         break;
  94                 if (c > ' ')
  95                         continue;
  96                 return error("char" PD_FMT ": could not verify tag name", tag_line - buffer);
  97         }
  98
  99         /* Verify the tagger line */
 100         tagger_line = tag_line;
 101
 102         if (memcmp(tagger_line, "tagger ", 7))
 103                 return error("char" PD_FMT ": could not find \"tagger \"",
 104                         tagger_line - buffer);
 105
 106         /*
 107          * Check for correct form for name and email
 108          * i.e. " <" followed by "> " on _this_ line
 109          * No angle brackets within the name or email address fields.
 110          * No spaces within the email address field.
 111          */
 112         tagger_line += 7;
 113         if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
 114                 strpbrk(tagger_line, "<>\n") != lb+1 ||
 115                 strpbrk(lb+2, "><\n ") != rb)
 116                 return error("char" PD_FMT ": malformed tagger field",
 117                         tagger_line - buffer);
 118
 119         /* Check for author name, at least one character, space is acceptable */
 120         if (lb == tagger_line)
 121                 return error("char" PD_FMT ": missing tagger name",
 122                         tagger_line - buffer);
 123
 124         /* timestamp, 1 or more digits followed by space */
 125         tagger_line = rb + 2;
 126         if (!(len = strspn(tagger_line, "0123456789")))
 127                 return error("char" PD_FMT ": missing tag timestamp",
 128                         tagger_line - buffer);
 129         tagger_line += len;
 130         if (*tagger_line != ' ')
 131                 return error("char" PD_FMT ": malformed tag timestamp",
 132                         tagger_line - buffer);
 133         tagger_line++;
 134
 135         /* timezone, 5 digits [+-]hhmm, max. 1400 */
 136         if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
 137               strspn(tagger_line+1, "0123456789") == 4 &&
 138               tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
 139                 return error("char" PD_FMT ": malformed tag timezone",
 140                         tagger_line - buffer);
 141         tagger_line += 6;
 142
 143         /* Verify the blank line separating the header from the body */
 144         if (*tagger_line != '\n')
 145                 return error("char" PD_FMT ": trailing garbage in tag header",
 146                         tagger_line - buffer);
 147
 148         /* The actual stuff afterwards we don't care about.. */
 149         return 0;
 150 }
 151
 152 #undef PD_FMT
 153
 154 int main(int argc, char **argv)
 155 {
 156         struct strbuf buf = STRBUF_INIT;
 157         unsigned char result_sha1[20];
 158
 159         if (argc != 1)
 160                 usage("git-mktag < signaturefile");
 161
 162         setup_git_directory();
 163
 164         if (strbuf_read(&buf, 0, 4096) < 0) {
 165                 die("could not read from stdin");
 166         }
 167
 168         /* Verify it for some basic sanity: it needs to start with
 169            "object <sha1>\ntype\ntagger " */
 170         if (verify_tag(buf.buf, buf.len) < 0)
 171                 die("invalid tag signature file");
 172
 173         if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
 174                 die("unable to write tag file");
 175
 176         strbuf_release(&buf);
 177         printf("%s\n", sha1_to_hex(result_sha1));
 178         return 0;
 179 }