mktag.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "exec_cmd.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 four lines are guaranteed to be at least 83 bytes:
  13  * "object <sha1>\n" is 48 bytes, "type tag\n" at 9 bytes is the
  14  * shortest possible type-line, "tag .\n" at 6 bytes is the shortest
  15  * single-character-tag line, and "tagger . <> 0 +0000\n" at 20 bytes is
  16  * the shortest possible tagger-line.
  17  */
  18
  19 /*
  20  * We refuse to tag something we can't verify. Just because.
  21  */
  22 static int verify_object(const unsigned char *sha1, const char *expected_type)
  23 {
  24         int ret = -1;
  25         enum object_type type;
  26         unsigned long size;
  27         const unsigned char *repl;
  28         void *buffer = read_sha1_file_repl(sha1, &type, &size, &repl);
  29
  30         if (buffer) {
  31                 if (type == type_from_string(expected_type))
  32                         ret = check_sha1_signature(repl, buffer, size, expected_type);
  33                 free(buffer);
  34         }
  35         return ret;
  36 }
  37
  38 #ifdef NO_C99_FORMAT
  39 #define PD_FMT "%d"
  40 #else
  41 #define PD_FMT "%td"
  42 #endif
  43
  44 static int verify_tag(char *buffer, unsigned long size)
  45 {
  46         int typelen;
  47         char type[20];
  48         unsigned char sha1[20];
  49         const char *object, *type_line, *tag_line, *tagger_line, *lb, *rb;
  50         size_t len;
  51
  52         if (size < 84)
  53                 return error("wanna fool me ? you obviously got the size wrong !");
  54
  55         buffer[size] = 0;
  56
  57         /* Verify object line */
  58         object = buffer;
  59         if (memcmp(object, "object ", 7))
  60                 return error("char%d: does not start with \"object \"", 0);
  61
  62         if (get_sha1_hex(object + 7, sha1))
  63                 return error("char%d: could not get SHA1 hash", 7);
  64
  65         /* Verify type line */
  66         type_line = object + 48;
  67         if (memcmp(type_line - 1, "\ntype ", 6))
  68                 return error("char%d: could not find \"\\ntype \"", 47);
  69
  70         /* Verify tag-line */
  71         tag_line = strchr(type_line, '\n');
  72         if (!tag_line)
  73                 return error("char" PD_FMT ": could not find next \"\\n\"", type_line - buffer);
  74         tag_line++;
  75         if (memcmp(tag_line, "tag ", 4) || tag_line[4] == '\n')
  76                 return error("char" PD_FMT ": no \"tag \" found", tag_line - buffer);
  77
  78         /* Get the actual type */
  79         typelen = tag_line - type_line - strlen("type \n");
  80         if (typelen >= sizeof(type))
  81                 return error("char" PD_FMT ": type too long", type_line+5 - buffer);
  82
  83         memcpy(type, type_line+5, typelen);
  84         type[typelen] = 0;
  85
  86         /* Verify that the object matches */
  87         if (verify_object(sha1, type))
  88                 return error("char%d: could not verify object %s", 7, sha1_to_hex(sha1));
  89
  90         /* Verify the tag-name: we don't allow control characters or spaces in it */
  91         tag_line += 4;
  92         for (;;) {
  93                 unsigned char c = *tag_line++;
  94                 if (c == '\n')
  95                         break;
  96                 if (c > ' ')
  97                         continue;
  98                 return error("char" PD_FMT ": could not verify tag name", 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" PD_FMT ": could not find \"tagger \"",
 106                         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" PD_FMT ": malformed tagger field",
 119                         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" PD_FMT ": missing tagger name",
 124                         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" PD_FMT ": missing tag timestamp",
 130                         tagger_line - buffer);
 131         tagger_line += len;
 132         if (*tagger_line != ' ')
 133                 return error("char" PD_FMT ": malformed tag timestamp",
 134                         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" PD_FMT ": malformed tag timezone",
 142                         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" PD_FMT ": trailing garbage in tag header",
 148                         tagger_line - buffer);
 149
 150         /* The actual stuff afterwards we don't care about.. */
 151         return 0;
 152 }
 153
 154 #undef PD_FMT
 155
 156 int main(int argc, char **argv)
 157 {
 158         struct strbuf buf = STRBUF_INIT;
 159         unsigned char result_sha1[20];
 160
 161         if (argc != 1)
 162                 usage("git mktag < signaturefile");
 163
 164         git_extract_argv0_path(argv[0]);
 165
 166         setup_git_directory();
 167
 168         if (strbuf_read(&buf, 0, 4096) < 0) {
 169                 die("could not read from stdin");
 170         }
 171
 172         /* Verify it for some basic sanity: it needs to start with
 173            "object <sha1>\ntype\ntagger " */
 174         if (verify_tag(buf.buf, buf.len) < 0)
 175                 die("invalid tag signature file");
 176
 177         if (write_sha1_file(buf.buf, buf.len, tag_type, result_sha1) < 0)
 178                 die("unable to write tag file");
 179
 180         strbuf_release(&buf);
 181         printf("%s\n", sha1_to_hex(result_sha1));
 182         return 0;
 183 }