builtin/mktag.c

   1 #include "builtin.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(const 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         const unsigned char *repl = lookup_replace_object(sha1);
  28
  29         if (buffer) {
  30                 if (type == type_from_string(expected_type))
  31                         ret = check_sha1_signature(repl, buffer, size, expected_type);
  32                 free(buffer);
  33         }
  34         return ret;
  35 }
  36
  37 static int verify_tag(char *buffer, unsigned long size)
  38 {
  39         int typelen;
  40         char type[20];
  41         unsigned char sha1[20];
  42         const char *object, *type_line, *tag_line, *tagger_line, *lb, *rb;
  43         size_t len;
  44
  45         if (size < 84)
  46                 return error("wanna fool me ? you obviously got the size wrong !");
  47
  48         buffer[size] = 0;
  49
  50         /* Verify object line */
  51         object = buffer;
  52         if (memcmp(object, "object ", 7))
  53                 return error("char%d: does not start with \"object \"", 0);
  54
  55         if (get_sha1_hex(object + 7, sha1))
  56                 return error("char%d: could not get SHA1 hash", 7);
  57
  58         /* Verify type line */
  59         type_line = object + 48;
  60         if (memcmp(type_line - 1, "\ntype ", 6))
  61                 return error("char%d: could not find \"\\ntype \"", 47);
  62
  63         /* Verify tag-line */
  64         tag_line = strchr(type_line, '\n');
  65         if (!tag_line)
  66                 return error("char%"PRIuMAX": could not find next \"\\n\"",
  67                                 (uintmax_t) (type_line - buffer));
  68         tag_line++;
  69         if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  70                 return error("char%"PRIuMAX": no \"tag \" found",
  71                                 (uintmax_t) (tag_line - buffer));
  72
  73         /* Get the actual type */
  74         typelen = tag_line - type_line - strlen("type \n");
  75         if (typelen >= sizeof(type))
  76                 return error("char%"PRIuMAX": type too long",
  77                                 (uintmax_t) (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%"PRIuMAX": could not verify tag name",
  95                                 (uintmax_t) (tag_line - buffer));
  96         }
  97
  98         /* Verify the tagger line */
  99         tagger_line = tag_line;
 100
 101         if (memcmp(tagger_line, "tagger ", 7))
 102                 return error("char%"PRIuMAX": could not find \"tagger \"",
 103                         (uintmax_t) (tagger_line - buffer));
 104
 105         /*
 106          * Check for correct form for name and email
 107          * i.e. " <" followed by "> " on _this_ line
 108          * No angle brackets within the name or email address fields.
 109          * No spaces within the email address field.
 110          */
 111         tagger_line += 7;
 112         if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
 113                 strpbrk(tagger_line, "<>\n") != lb+1 ||
 114                 strpbrk(lb+2, "><\n ") != rb)
 115                 return error("char%"PRIuMAX": malformed tagger field",
 116                         (uintmax_t) (tagger_line - buffer));
 117
 118         /* Check for author name, at least one character, space is acceptable */
 119         if (lb == tagger_line)
 120                 return error("char%"PRIuMAX": missing tagger name",
 121                         (uintmax_t) (tagger_line - buffer));
 122
 123         /* timestamp, 1 or more digits followed by space */
 124         tagger_line = rb + 2;
 125         if (!(len = strspn(tagger_line, "0123456789")))
 126                 return error("char%"PRIuMAX": missing tag timestamp",
 127                         (uintmax_t) (tagger_line - buffer));
 128         tagger_line += len;
 129         if (*tagger_line != ' ')
 130                 return error("char%"PRIuMAX": malformed tag timestamp",
 131                         (uintmax_t) (tagger_line - buffer));
 132         tagger_line++;
 133
 134         /* timezone, 5 digits [+-]hhmm, max. 1400 */
 135         if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
 136               strspn(tagger_line+1, "0123456789") == 4 &&
 137               tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
 138                 return error("char%"PRIuMAX": malformed tag timezone",
 139                         (uintmax_t) (tagger_line - buffer));
 140         tagger_line += 6;
 141
 142         /* Verify the blank line separating the header from the body */
 143         if (*tagger_line != '\n')
 144                 return error("char%"PRIuMAX": trailing garbage in tag header",
 145                         (uintmax_t) (tagger_line - buffer));
 146
 147         /* The actual stuff afterwards we don't care about.. */
 148         return 0;
 149 }
 150
 151 int cmd_mktag(int argc, const char **argv, const char *prefix)
 152 {
 153         struct strbuf buf = STRBUF_INIT;
 154         unsigned char result_sha1[20];
 155
 156         if (argc != 1)
 157                 usage("git mktag < signaturefile");
 158
 159         if (strbuf_read(&buf, 0, 4096) < 0) {
 160                 die_errno("could not read from stdin");
 161         }
 162
 163         /* Verify it for some basic sanity: it needs to start with
 164            "object <sha1>\ntype\ntagger " */
 165         if (verify_tag(buf.buf, buf.len) < 0)
 166                 die("invalid tag signature file");
 167
 168         if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
 169                 die("unable to write tag file");
 170
 171         strbuf_release(&buf);
 172         printf("%s\n", sha1_to_hex(result_sha1));
 173         return 0;
 174 }