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 struct object_id *oid, const char *expected_type)
  22 {
  23         int ret = -1;
  24         enum object_type type;
  25         unsigned long size;
  26         void *buffer = read_sha1_file(oid->hash, &type, &size);
  27         const unsigned char *repl = lookup_replace_object(oid->hash);
  28
  29         if (buffer) {
  30                 struct object_id reploid;
  31                 hashcpy(reploid.hash, repl);
  32
  33                 if (type == type_from_string(expected_type))
  34                         ret = check_object_signature(&reploid, buffer, size, expected_type);
  35                 free(buffer);
  36         }
  37         return ret;
  38 }
  39
  40 static int verify_tag(char *buffer, unsigned long size)
  41 {
  42         int typelen;
  43         char type[20];
  44         struct object_id oid;
  45         const char *object, *type_line, *tag_line, *tagger_line, *lb, *rb, *p;
  46         size_t len;
  47
  48         if (size < 84)
  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 (parse_oid_hex(object + 7, &oid, &p))
  59                 return error("char%d: could not get SHA1 hash", 7);
  60
  61         /* Verify type line */
  62         type_line = p + 1;
  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%"PRIuMAX": could not find next \"\\n\"",
  70                                 (uintmax_t) (type_line - buffer));
  71         tag_line++;
  72         if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  73                 return error("char%"PRIuMAX": no \"tag \" found",
  74                                 (uintmax_t) (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%"PRIuMAX": type too long",
  80                                 (uintmax_t) (type_line+5 - buffer));
  81
  82         memcpy(type, type_line+5, typelen);
  83         type[typelen] = 0;
  84
  85         /* Verify that the object matches */
  86         if (verify_object(&oid, type))
  87                 return error("char%d: could not verify object %s", 7, oid_to_hex(&oid));
  88
  89         /* Verify the tag-name: we don't allow control characters or spaces in it */
  90         tag_line += 4;
  91         for (;;) {
  92                 unsigned char c = *tag_line++;
  93                 if (c == '\n')
  94                         break;
  95                 if (c > ' ')
  96                         continue;
  97                 return error("char%"PRIuMAX": could not verify tag name",
  98                                 (uintmax_t) (tag_line - buffer));
  99         }
 100
 101         /* Verify the tagger line */
 102         tagger_line = tag_line;
 103
 104         if (memcmp(tagger_line, "tagger ", 7))
 105                 return error("char%"PRIuMAX": could not find \"tagger \"",
 106                         (uintmax_t) (tagger_line - buffer));
 107
 108         /*
 109          * Check for correct form for name and email
 110          * i.e. " <" followed by "> " on _this_ line
 111          * No angle brackets within the name or email address fields.
 112          * No spaces within the email address field.
 113          */
 114         tagger_line += 7;
 115         if (!(lb = strstr(tagger_line, " <")) || !(rb = strstr(lb+2, "> ")) ||
 116                 strpbrk(tagger_line, "<>\n") != lb+1 ||
 117                 strpbrk(lb+2, "><\n ") != rb)
 118                 return error("char%"PRIuMAX": malformed tagger field",
 119                         (uintmax_t) (tagger_line - buffer));
 120
 121         /* Check for author name, at least one character, space is acceptable */
 122         if (lb == tagger_line)
 123                 return error("char%"PRIuMAX": missing tagger name",
 124                         (uintmax_t) (tagger_line - buffer));
 125
 126         /* timestamp, 1 or more digits followed by space */
 127         tagger_line = rb + 2;
 128         if (!(len = strspn(tagger_line, "0123456789")))
 129                 return error("char%"PRIuMAX": missing tag timestamp",
 130                         (uintmax_t) (tagger_line - buffer));
 131         tagger_line += len;
 132         if (*tagger_line != ' ')
 133                 return error("char%"PRIuMAX": malformed tag timestamp",
 134                         (uintmax_t) (tagger_line - buffer));
 135         tagger_line++;
 136
 137         /* timezone, 5 digits [+-]hhmm, max. 1400 */
 138         if (!((tagger_line[0] == '+' || tagger_line[0] == '-') &&
 139               strspn(tagger_line+1, "0123456789") == 4 &&
 140               tagger_line[5] == '\n' && atoi(tagger_line+1) <= 1400))
 141                 return error("char%"PRIuMAX": malformed tag timezone",
 142                         (uintmax_t) (tagger_line - buffer));
 143         tagger_line += 6;
 144
 145         /* Verify the blank line separating the header from the body */
 146         if (*tagger_line != '\n')
 147                 return error("char%"PRIuMAX": trailing garbage in tag header",
 148                         (uintmax_t) (tagger_line - buffer));
 149
 150         /* The actual stuff afterwards we don't care about.. */
 151         return 0;
 152 }
 153
 154 int cmd_mktag(int argc, const char **argv, const char *prefix)
 155 {
 156         struct strbuf buf = STRBUF_INIT;
 157         struct object_id result;
 158
 159         if (argc != 1)
 160                 usage("git mktag");
 161
 162         if (strbuf_read(&buf, 0, 4096) < 0) {
 163                 die_errno("could not read from stdin");
 164         }
 165
 166         /* Verify it for some basic sanity: it needs to start with
 167            "object <sha1>\ntype\ntagger " */
 168         if (verify_tag(buf.buf, buf.len) < 0)
 169                 die("invalid tag signature file");
 170
 171         if (write_object_file(buf.buf, buf.len, tag_type, &result) < 0)
 172                 die("unable to write tag file");
 173
 174         strbuf_release(&buf);
 175         printf("%s\n", oid_to_hex(&result));
 176         return 0;
 177 }