dlls/rsaenh/rsa.c

   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 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 int rand_prime(mp_int *N, long len)
  62 {
  63    int type;
  64
  65    /* allow sizes between 2 and 256 bytes for a prime size */
  66    if (len < 16 || len > 8192) {
  67           printf("Invalid prime size!\n");
  68       return CRYPT_INVALID_PRIME_SIZE;
  69    }
  70
  71    /* get type */
  72    if (len < 0) {
  73       type = LTM_PRIME_BBS;
  74       len = -len;
  75    } else {
  76       /* This seems to be what MS CSP's do: */
  77       type = LTM_PRIME_2MSB_ON;
  78       /* Original LibTomCrypt: type = 0; */
  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, (unsigned char *)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 }