keyid.c

   1 /*
   2  * keyid.c - Routines to calculate key IDs.
   3  *
   4  * Jonathan McDowell <noodles@earth.li>
   5  *
   6  * Copyright 2002 Project Purple
   7  */
   8
   9 #include <sys/types.h>
  10
  11 #include "keyid.h"
  12 #include "keystructs.h"
  13 #include "md5.h"
  14 #include "sha.h"
  15
  16 /**
  17  *      get_keyid - Given a public key returns the keyid.
  18  *      @publickey: The key to calculate the fingerprint for.
  19  */
  20 uint64_t get_keyid(struct openpgp_publickey *publickey)
  21 {
  22         SHA1_CONTEXT sha_ctx;
  23         uint64_t keyid = 0;
  24         int offset = 0;
  25         int i = 0;
  26         unsigned char c;
  27         unsigned char *buff = NULL;
  28
  29         switch (publickey->publickey->data[0]) {
  30         case 2:
  31         case 3:
  32                 /*
  33                  * For a type 2 or 3 key the keyid is the last 64 bits of the
  34                  * public modulus n, which is stored as an MPI from offset 8
  35                  * onwards.
  36                  *
  37                  * We need to ensure it's an RSA key.
  38                  */
  39                 if (publickey->publickey->data[7] == 1) {
  40                         offset = (publickey->publickey->data[8] << 8) +
  41                                 publickey->publickey->data[9];
  42                         offset = ((offset + 7) / 8) + 2;
  43
  44                         for (keyid = 0, i = 0; i < 8; i++) {
  45                                 keyid <<= 8;
  46                                 keyid += publickey->publickey->data[offset++];
  47                         }
  48                 } else {
  49                         fputs("Type 2 or 3 key, but not RSA.\n", stderr);
  50                 }
  51                 break;
  52         case 4:
  53                 /*
  54                  * For a type 4 key the keyid is the last 64 bits of the
  55                  * fingerprint, which is the 160 bit SHA-1 hash of the packet
  56                  * tag, 2 octet packet length and the public key packet
  57                  * including version field.
  58                  */
  59                 sha1_init(&sha_ctx);
  60                 /*
  61                  * TODO: Can this be 0x99? Are all public key packets old
  62                  * format with 2 bytes of length data?
  63                  */
  64                 c = 0x99;
  65                 sha1_write(&sha_ctx, &c, sizeof(c));
  66                 c = publickey->publickey->length >> 8;
  67                 sha1_write(&sha_ctx, &c, sizeof(c));
  68                 c = publickey->publickey->length & 0xFF;
  69                 sha1_write(&sha_ctx, &c, sizeof(c));
  70                 sha1_write(&sha_ctx, publickey->publickey->data,
  71                         publickey->publickey->length);
  72                 sha1_final(&sha_ctx);
  73                 buff = sha1_read(&sha_ctx);
  74
  75                 assert(buff != NULL);
  76
  77                 for (keyid = 0, i = 12; i < 20; i++) {
  78                         keyid <<= 8;
  79                         keyid += buff[i];
  80                 }
  81
  82                 break;
  83         default:
  84                 fprintf(stderr, "Unknown key type: %d\n",
  85                                 publickey->publickey->data[0]);
  86         }
  87
  88         return keyid;
  89 }