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         assert(publickey != NULL);
  30
  31         switch (publickey->publickey->data[0]) {
  32         case 2:
  33         case 3:
  34                 /*
  35                  * For a type 2 or 3 key the keyid is the last 64 bits of the
  36                  * public modulus n, which is stored as an MPI from offset 8
  37                  * onwards.
  38                  *
  39                  * We need to ensure it's an RSA key.
  40                  */
  41                 if (publickey->publickey->data[7] == 1) {
  42                         offset = (publickey->publickey->data[8] << 8) +
  43                                 publickey->publickey->data[9];
  44                         offset = ((offset + 7) / 8) + 2;
  45
  46                         for (keyid = 0, i = 0; i < 8; i++) {
  47                                 keyid <<= 8;
  48                                 keyid += publickey->publickey->data[offset++];
  49                         }
  50                 } else {
  51                         fputs("Type 2 or 3 key, but not RSA.\n", stderr);
  52                 }
  53                 break;
  54         case 4:
  55                 /*
  56                  * For a type 4 key the keyid is the last 64 bits of the
  57                  * fingerprint, which is the 160 bit SHA-1 hash of the packet
  58                  * tag, 2 octet packet length and the public key packet
  59                  * including version field.
  60                  */
  61                 sha1_init(&sha_ctx);
  62                 /*
  63                  * TODO: Can this be 0x99? Are all public key packets old
  64                  * format with 2 bytes of length data?
  65                  */
  66                 c = 0x99;
  67                 sha1_write(&sha_ctx, &c, sizeof(c));
  68                 c = publickey->publickey->length >> 8;
  69                 sha1_write(&sha_ctx, &c, sizeof(c));
  70                 c = publickey->publickey->length & 0xFF;
  71                 sha1_write(&sha_ctx, &c, sizeof(c));
  72                 sha1_write(&sha_ctx, publickey->publickey->data,
  73                         publickey->publickey->length);
  74                 sha1_final(&sha_ctx);
  75                 buff = sha1_read(&sha_ctx);
  76
  77                 assert(buff != NULL);
  78
  79                 for (keyid = 0, i = 12; i < 20; i++) {
  80                         keyid <<= 8;
  81                         keyid += buff[i];
  82                 }
  83
  84                 break;
  85         default:
  86                 fprintf(stderr, "Unknown key type: %d\n",
  87                                 publickey->publickey->data[0]);
  88         }
  89
  90         return keyid;
  91 }