crypto/srp/srp_lib.c

   1 /* crypto/srp/srp_lib.c */
   2 /*
   3  * Written by Christophe Renou (christophe.renou@edelweb.fr) with the
   4  * precious help of Peter Sylvester (peter.sylvester@edelweb.fr) for the
   5  * EdelKey project and contributed to the OpenSSL project 2004.
   6  */
   7 /* ====================================================================
   8  * Copyright (c) 2004 The OpenSSL Project.  All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  *
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  *
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in
  19  *    the documentation and/or other materials provided with the
  20  *    distribution.
  21  *
  22  * 3. All advertising materials mentioning features or use of this
  23  *    software must display the following acknowledgment:
  24  *    "This product includes software developed by the OpenSSL Project
  25  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  26  *
  27  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  28  *    endorse or promote products derived from this software without
  29  *    prior written permission. For written permission, please contact
  30  *    licensing@OpenSSL.org.
  31  *
  32  * 5. Products derived from this software may not be called "OpenSSL"
  33  *    nor may "OpenSSL" appear in their names without prior written
  34  *    permission of the OpenSSL Project.
  35  *
  36  * 6. Redistributions of any form whatsoever must retain the following
  37  *    acknowledgment:
  38  *    "This product includes software developed by the OpenSSL Project
  39  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  42  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  44  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  45  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  46  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  47  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  48  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  49  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  50  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  51  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  52  * OF THE POSSIBILITY OF SUCH DAMAGE.
  53  * ====================================================================
  54  *
  55  * This product includes cryptographic software written by Eric Young
  56  * (eay@cryptsoft.com).  This product includes software written by Tim
  57  * Hudson (tjh@cryptsoft.com).
  58  *
  59  */
  60 #ifndef OPENSSL_NO_SRP
  61 # include "cryptlib.h"
  62 # include <openssl/sha.h>
  63 # include <openssl/srp.h>
  64 # include <openssl/evp.h>
  65 # include "internal/bn_srp.h"
  66
  67 static BIGNUM *srp_Calc_k(BIGNUM *N, BIGNUM *g)
  68 {
  69     /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
  70
  71     unsigned char digest[SHA_DIGEST_LENGTH];
  72     unsigned char *tmp;
  73     EVP_MD_CTX ctxt;
  74     int longg;
  75     int longN = BN_num_bytes(N);
  76
  77     if (BN_ucmp(g, N) >= 0)
  78         return NULL;
  79
  80     if ((tmp = OPENSSL_malloc(longN)) == NULL)
  81         return NULL;
  82     BN_bn2bin(N, tmp);
  83
  84     EVP_MD_CTX_init(&ctxt);
  85     EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
  86     EVP_DigestUpdate(&ctxt, tmp, longN);
  87
  88     memset(tmp, 0, longN);
  89     longg = BN_bn2bin(g, tmp);
  90     /* use the zeros behind to pad on left */
  91     EVP_DigestUpdate(&ctxt, tmp + longg, longN - longg);
  92     EVP_DigestUpdate(&ctxt, tmp, longg);
  93     OPENSSL_free(tmp);
  94
  95     EVP_DigestFinal_ex(&ctxt, digest, NULL);
  96     EVP_MD_CTX_cleanup(&ctxt);
  97     return BN_bin2bn(digest, sizeof(digest), NULL);
  98 }
  99
 100 BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N)
 101 {
 102     /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
 103
 104     BIGNUM *u;
 105     unsigned char cu[SHA_DIGEST_LENGTH];
 106     unsigned char *cAB;
 107     EVP_MD_CTX ctxt;
 108     int longN;
 109     if ((A == NULL) || (B == NULL) || (N == NULL))
 110         return NULL;
 111
 112     if (BN_ucmp(A, N) >= 0 || BN_ucmp(B, N) >= 0)
 113         return NULL;
 114
 115     longN = BN_num_bytes(N);
 116
 117     if ((cAB = OPENSSL_malloc(2 * longN)) == NULL)
 118         return NULL;
 119
 120     memset(cAB, 0, longN);
 121
 122     EVP_MD_CTX_init(&ctxt);
 123     EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
 124     EVP_DigestUpdate(&ctxt, cAB + BN_bn2bin(A, cAB + longN), longN);
 125     EVP_DigestUpdate(&ctxt, cAB + BN_bn2bin(B, cAB + longN), longN);
 126     OPENSSL_free(cAB);
 127     EVP_DigestFinal_ex(&ctxt, cu, NULL);
 128     EVP_MD_CTX_cleanup(&ctxt);
 129
 130     if (!(u = BN_bin2bn(cu, sizeof(cu), NULL)))
 131         return NULL;
 132     if (!BN_is_zero(u))
 133         return u;
 134     BN_free(u);
 135     return NULL;
 136 }
 137
 138 BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b,
 139                             BIGNUM *N)
 140 {
 141     BIGNUM *tmp = NULL, *S = NULL;
 142     BN_CTX *bn_ctx;
 143
 144     if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)
 145         return NULL;
 146
 147     if ((bn_ctx = BN_CTX_new()) == NULL ||
 148         (tmp = BN_new()) == NULL || (S = BN_new()) == NULL)
 149         goto err;
 150
 151     /* S = (A*v**u) ** b */
 152
 153     if (!BN_mod_exp(tmp, v, u, N, bn_ctx))
 154         goto err;
 155     if (!BN_mod_mul(tmp, A, tmp, N, bn_ctx))
 156         goto err;
 157     if (!BN_mod_exp(S, tmp, b, N, bn_ctx))
 158         goto err;
 159  err:
 160     BN_CTX_free(bn_ctx);
 161     BN_clear_free(tmp);
 162     return S;
 163 }
 164
 165 BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v)
 166 {
 167     BIGNUM *kv = NULL, *gb = NULL;
 168     BIGNUM *B = NULL, *k = NULL;
 169     BN_CTX *bn_ctx;
 170
 171     if (b == NULL || N == NULL || g == NULL || v == NULL ||
 172         (bn_ctx = BN_CTX_new()) == NULL)
 173         return NULL;
 174
 175     if ((kv = BN_new()) == NULL ||
 176         (gb = BN_new()) == NULL || (B = BN_new()) == NULL)
 177         goto err;
 178
 179     /* B = g**b + k*v */
 180
 181     if (!BN_mod_exp(gb, g, b, N, bn_ctx) ||
 182         !(k = srp_Calc_k(N, g)) ||
 183         !BN_mod_mul(kv, v, k, N, bn_ctx) ||
 184         !BN_mod_add(B, gb, kv, N, bn_ctx)) {
 185         BN_free(B);
 186         B = NULL;
 187     }
 188  err:
 189     BN_CTX_free(bn_ctx);
 190     BN_clear_free(kv);
 191     BN_clear_free(gb);
 192     BN_free(k);
 193     return B;
 194 }
 195
 196 BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass)
 197 {
 198     unsigned char dig[SHA_DIGEST_LENGTH];
 199     EVP_MD_CTX ctxt;
 200     unsigned char *cs;
 201
 202     if ((s == NULL) || (user == NULL) || (pass == NULL))
 203         return NULL;
 204
 205     if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)
 206         return NULL;
 207
 208     EVP_MD_CTX_init(&ctxt);
 209     EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
 210     EVP_DigestUpdate(&ctxt, user, strlen(user));
 211     EVP_DigestUpdate(&ctxt, ":", 1);
 212     EVP_DigestUpdate(&ctxt, pass, strlen(pass));
 213     EVP_DigestFinal_ex(&ctxt, dig, NULL);
 214
 215     EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
 216     BN_bn2bin(s, cs);
 217     EVP_DigestUpdate(&ctxt, cs, BN_num_bytes(s));
 218     OPENSSL_free(cs);
 219     EVP_DigestUpdate(&ctxt, dig, sizeof(dig));
 220     EVP_DigestFinal_ex(&ctxt, dig, NULL);
 221     EVP_MD_CTX_cleanup(&ctxt);
 222
 223     return BN_bin2bn(dig, sizeof(dig), NULL);
 224 }
 225
 226 BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g)
 227 {
 228     BN_CTX *bn_ctx;
 229     BIGNUM *A = NULL;
 230
 231     if (a == NULL || N == NULL || g == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 232         return NULL;
 233
 234     if ((A = BN_new()) != NULL && !BN_mod_exp(A, g, a, N, bn_ctx)) {
 235         BN_free(A);
 236         A = NULL;
 237     }
 238     BN_CTX_free(bn_ctx);
 239     return A;
 240 }
 241
 242 BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x,
 243                             BIGNUM *a, BIGNUM *u)
 244 {
 245     BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;
 246     BN_CTX *bn_ctx;
 247
 248     if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL
 249         || a == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 250         return NULL;
 251
 252     if ((tmp = BN_new()) == NULL ||
 253         (tmp2 = BN_new()) == NULL ||
 254         (tmp3 = BN_new()) == NULL ||
 255         (K = BN_new()) == NULL)
 256         goto err;
 257
 258     if (!BN_mod_exp(tmp, g, x, N, bn_ctx))
 259         goto err;
 260     if (!(k = srp_Calc_k(N, g)))
 261         goto err;
 262     if (!BN_mod_mul(tmp2, tmp, k, N, bn_ctx))
 263         goto err;
 264     if (!BN_mod_sub(tmp, B, tmp2, N, bn_ctx))
 265         goto err;
 266
 267     if (!BN_mod_mul(tmp3, u, x, N, bn_ctx))
 268         goto err;
 269     if (!BN_mod_add(tmp2, a, tmp3, N, bn_ctx))
 270         goto err;
 271     if (!BN_mod_exp(K, tmp, tmp2, N, bn_ctx))
 272         goto err;
 273
 274  err:
 275     BN_CTX_free(bn_ctx);
 276     BN_clear_free(tmp);
 277     BN_clear_free(tmp2);
 278     BN_clear_free(tmp3);
 279     BN_free(k);
 280     return K;
 281 }
 282
 283 int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N)
 284 {
 285     BIGNUM *r;
 286     BN_CTX *bn_ctx;
 287     int ret = 0;
 288
 289     if (B == NULL || N == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 290         return 0;
 291
 292     if ((r = BN_new()) == NULL)
 293         goto err;
 294     /* Checks if B % N == 0 */
 295     if (!BN_nnmod(r, B, N, bn_ctx))
 296         goto err;
 297     ret = !BN_is_zero(r);
 298  err:
 299     BN_CTX_free(bn_ctx);
 300     BN_free(r);
 301     return ret;
 302 }
 303
 304 int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N)
 305 {
 306     /* Checks if A % N == 0 */
 307     return SRP_Verify_B_mod_N(A, N);
 308 }
 309
 310 /*
 311  * Check if G and N are kwown parameters. The values have been generated
 312  * from the ietf-tls-srp draft version 8
 313  */
 314 char *SRP_check_known_gN_param(BIGNUM *g, BIGNUM *N)
 315 {
 316     size_t i;
 317     if ((g == NULL) || (N == NULL))
 318         return 0;
 319
 320     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
 321         if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)
 322             return knowngN[i].id;
 323     }
 324     return NULL;
 325 }
 326
 327 SRP_gN *SRP_get_default_gN(const char *id)
 328 {
 329     size_t i;
 330
 331     if (id == NULL)
 332         return knowngN;
 333     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
 334         if (strcmp(knowngN[i].id, id) == 0)
 335             return knowngN + i;
 336     }
 337     return NULL;
 338 }
 339 #endif