1 /* 2 * dlls/rsaenh/rsa.c 3 * RSA public key cryptographic functions 4 * 5 * Copyright 2004 Michael Jung 6 * Based on public domain code by Tom St Denis (tomstdenis@iahu.ca) 7 * 8 * This library is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU Lesser General Public 10 * License as published by the Free Software Foundation; either 11 * version 2.1 of the License, or (at your option) any later version. 12 * 13 * This library is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 16 * Lesser General Public License for more details. 17 * 18 * You should have received a copy of the GNU Lesser General Public 19 * License along with this library; if not, write to the Free Software 20 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA 21 */ 22 23 /* 24 * This file contains code from the LibTomCrypt cryptographic 25 * library written by Tom St Denis (tomstdenis@iahu.ca). LibTomCrypt 26 * is in the public domain. The code in this file is tailored to 27 * special requirements. Take a look at http://libtomcrypt.org for the 28 * original version. 29 */ 30 31 #include "tomcrypt.h" 32 33 static const struct { 34 int mpi_code, ltc_code; 35 } mpi_to_ltc_codes[] = { 36 { MP_OKAY , CRYPT_OK}, 37 { MP_MEM , CRYPT_MEM}, 38 { MP_VAL , CRYPT_INVALID_ARG}, 39 }; 40 41 /* convert a MPI error to a LTC error (Possibly the most powerful function ever! Oh wait... no) */ 42 static int mpi_to_ltc_error(int err) 43 { 44 int x; 45 46 for (x = 0; x < (int)(sizeof(mpi_to_ltc_codes)/sizeof(mpi_to_ltc_codes[0])); x++) { 47 if (err == mpi_to_ltc_codes[x].mpi_code) { 48 return mpi_to_ltc_codes[x].ltc_code; 49 } 50 } 51 return CRYPT_ERROR; 52 } 53 54 extern int gen_rand_impl(unsigned char *dst, unsigned int len); 55 56 static int rand_prime_helper(unsigned char *dst, int len, void *dat) 57 { 58 return gen_rand_impl(dst, len) ? len : 0; 59 } 60 61 static int rand_prime(mp_int *N, long len) 62 { 63 int type; 64 65 /* get type */ 66 if (len < 0) { 67 type = LTM_PRIME_BBS; 68 len = -len; 69 } else { 70 /* This seems to be what MS CSP's do: */ 71 type = LTM_PRIME_2MSB_ON; 72 /* Original LibTomCrypt: type = 0; */ 73 } 74 75 /* allow sizes between 2 and 256 bytes for a prime size */ 76 if (len < 16 || len > 8192) { 77 printf("Invalid prime size!\n"); 78 return CRYPT_INVALID_PRIME_SIZE; 79 } 80 81 /* New prime generation makes the code even more cryptoish-insane. Do you know what this means!!! 82 -- Gir: Yeah, oh wait, er, no. 83 */ 84 return mpi_to_ltc_error(mp_prime_random_ex(N, mp_prime_rabin_miller_trials(len), len, type, rand_prime_helper, NULL)); 85 } 86 87 int rsa_make_key(int size, long e, rsa_key *key) 88 { 89 mp_int p, q, tmp1, tmp2, tmp3; 90 int err; 91 92 if ((size < (MIN_RSA_SIZE/8)) || (size > (MAX_RSA_SIZE/8))) { 93 return CRYPT_INVALID_KEYSIZE; 94 } 95 96 if ((e < 3) || ((e & 1) == 0)) { 97 return CRYPT_INVALID_ARG; 98 } 99 100 if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != MP_OKAY) { 101 return mpi_to_ltc_error(err); 102 } 103 104 /* make primes p and q (optimization provided by Wayne Scott) */ 105 if ((err = mp_set_int(&tmp3, e)) != MP_OKAY) { goto error; } /* tmp3 = e */ 106 107 /* make prime "p" */ 108 do { 109 if ((err = rand_prime(&p, size*4)) != CRYPT_OK) { goto done; } 110 if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = p-1 */ 111 if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY) { goto error; } /* tmp2 = gcd(p-1, e) */ 112 } while (mp_cmp_d(&tmp2, 1) != 0); /* while e divides p-1 */ 113 114 /* make prime "q" */ 115 do { 116 if ((err = rand_prime(&q, size*4)) != CRYPT_OK) { goto done; } 117 if ((err = mp_sub_d(&q, 1, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = q-1 */ 118 if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY) { goto error; } /* tmp2 = gcd(q-1, e) */ 119 } while (mp_cmp_d(&tmp2, 1) != 0); /* while e divides q-1 */ 120 121 /* tmp1 = lcm(p-1, q-1) */ 122 if ((err = mp_sub_d(&p, 1, &tmp2)) != MP_OKAY) { goto error; } /* tmp2 = p-1 */ 123 /* tmp1 = q-1 (previous do/while loop) */ 124 if ((err = mp_lcm(&tmp1, &tmp2, &tmp1)) != MP_OKAY) { goto error; } /* tmp1 = lcm(p-1, q-1) */ 125 126 /* make key */ 127 if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP, 128 &key->qP, &key->p, &key->q, NULL)) != MP_OKAY) { 129 goto error; 130 } 131 132 if ((err = mp_set_int(&key->e, e)) != MP_OKAY) { goto error2; } /* key->e = e */ 133 if ((err = mp_invmod(&key->e, &tmp1, &key->d)) != MP_OKAY) { goto error2; } /* key->d = 1/e mod lcm(p-1,q-1) */ 134 if ((err = mp_mul(&p, &q, &key->N)) != MP_OKAY) { goto error2; } /* key->N = pq */ 135 136 /* optimize for CRT now */ 137 /* find d mod q-1 and d mod p-1 */ 138 if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY) { goto error2; } /* tmp1 = q-1 */ 139 if ((err = mp_sub_d(&q, 1, &tmp2)) != MP_OKAY) { goto error2; } /* tmp2 = p-1 */ 140 if ((err = mp_mod(&key->d, &tmp1, &key->dP)) != MP_OKAY) { goto error2; } /* dP = d mod p-1 */ 141 if ((err = mp_mod(&key->d, &tmp2, &key->dQ)) != MP_OKAY) { goto error2; } /* dQ = d mod q-1 */ 142 if ((err = mp_invmod(&q, &p, &key->qP)) != MP_OKAY) { goto error2; } /* qP = 1/q mod p */ 143 144 if ((err = mp_copy(&p, &key->p)) != MP_OKAY) { goto error2; } 145 if ((err = mp_copy(&q, &key->q)) != MP_OKAY) { goto error2; } 146 147 /* shrink ram required */ 148 if ((err = mp_shrink(&key->e)) != MP_OKAY) { goto error2; } 149 if ((err = mp_shrink(&key->d)) != MP_OKAY) { goto error2; } 150 if ((err = mp_shrink(&key->N)) != MP_OKAY) { goto error2; } 151 if ((err = mp_shrink(&key->dQ)) != MP_OKAY) { goto error2; } 152 if ((err = mp_shrink(&key->dP)) != MP_OKAY) { goto error2; } 153 if ((err = mp_shrink(&key->qP)) != MP_OKAY) { goto error2; } 154 if ((err = mp_shrink(&key->p)) != MP_OKAY) { goto error2; } 155 if ((err = mp_shrink(&key->q)) != MP_OKAY) { goto error2; } 156 157 /* set key type (in this case it's CRT optimized) */ 158 key->type = PK_PRIVATE; 159 160 /* return ok and free temps */ 161 err = CRYPT_OK; 162 goto done; 163 error2: 164 mp_clear_multi(&key->d, &key->e, &key->N, &key->dQ, &key->dP, 165 &key->qP, &key->p, &key->q, NULL); 166 error: 167 err = mpi_to_ltc_error(err); 168 done: 169 mp_clear_multi(&tmp3, &tmp2, &tmp1, &p, &q, NULL); 170 return err; 171 } 172 173 void rsa_free(rsa_key *key) 174 { 175 mp_clear_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP, 176 &key->qP, &key->p, &key->q, NULL); 177 } 178 179 /* compute an RSA modular exponentiation */ 180 int rsa_exptmod(const unsigned char *in, unsigned long inlen, 181 unsigned char *out, unsigned long *outlen, int which, 182 rsa_key *key) 183 { 184 mp_int tmp, tmpa, tmpb; 185 unsigned long x; 186 int err; 187 188 /* is the key of the right type for the operation? */ 189 if (which == PK_PRIVATE && (key->type != PK_PRIVATE)) { 190 return CRYPT_PK_NOT_PRIVATE; 191 } 192 193 /* must be a private or public operation */ 194 if (which != PK_PRIVATE && which != PK_PUBLIC) { 195 return CRYPT_PK_INVALID_TYPE; 196 } 197 198 /* init and copy into tmp */ 199 if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != MP_OKAY) { return mpi_to_ltc_error(err); } 200 if ((err = mp_read_unsigned_bin(&tmp, in, (int)inlen)) != MP_OKAY) { goto error; } 201 202 /* sanity check on the input */ 203 if (mp_cmp(&key->N, &tmp) == MP_LT) { 204 err = CRYPT_PK_INVALID_SIZE; 205 goto done; 206 } 207 208 /* are we using the private exponent and is the key optimized? */ 209 if (which == PK_PRIVATE) { 210 /* tmpa = tmp^dP mod p */ 211 if ((err = mpi_to_ltc_error(mp_exptmod(&tmp, &key->dP, &key->p, &tmpa))) != MP_OKAY) { goto error; } 212 213 /* tmpb = tmp^dQ mod q */ 214 if ((err = mpi_to_ltc_error(mp_exptmod(&tmp, &key->dQ, &key->q, &tmpb))) != MP_OKAY) { goto error; } 215 216 /* tmp = (tmpa - tmpb) * qInv (mod p) */ 217 if ((err = mp_sub(&tmpa, &tmpb, &tmp)) != MP_OKAY) { goto error; } 218 if ((err = mp_mulmod(&tmp, &key->qP, &key->p, &tmp)) != MP_OKAY) { goto error; } 219 220 /* tmp = tmpb + q * tmp */ 221 if ((err = mp_mul(&tmp, &key->q, &tmp)) != MP_OKAY) { goto error; } 222 if ((err = mp_add(&tmp, &tmpb, &tmp)) != MP_OKAY) { goto error; } 223 } else { 224 /* exptmod it */ 225 if ((err = mp_exptmod(&tmp, &key->e, &key->N, &tmp)) != MP_OKAY) { goto error; } 226 } 227 228 /* read it back */ 229 x = (unsigned long)mp_unsigned_bin_size(&key->N); 230 if (x > *outlen) { 231 err = CRYPT_BUFFER_OVERFLOW; 232 goto done; 233 } 234 *outlen = x; 235 236 /* convert it */ 237 memset(out, 0, x); 238 if ((err = mp_to_unsigned_bin(&tmp, out+(x-mp_unsigned_bin_size(&tmp)))) != MP_OKAY) { goto error; } 239 240 /* clean up and return */ 241 err = CRYPT_OK; 242 goto done; 243 error: 244 err = mpi_to_ltc_error(err); 245 done: 246 mp_clear_multi(&tmp, &tmpa, &tmpb, NULL); 247 return err; 248 } 249