crypto/srp/srp_lib.c

   1 /*
   2  * Written by Christophe Renou (christophe.renou@edelweb.fr) with the
   3  * precious help of Peter Sylvester (peter.sylvester@edelweb.fr) for the
   4  * EdelKey project and contributed to the OpenSSL project 2004.
   5  */
   6 /* ====================================================================
   7  * Copyright (c) 2004 The OpenSSL Project.  All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  *
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in
  18  *    the documentation and/or other materials provided with the
  19  *    distribution.
  20  *
  21  * 3. All advertising materials mentioning features or use of this
  22  *    software must display the following acknowledgment:
  23  *    "This product includes software developed by the OpenSSL Project
  24  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  25  *
  26  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  27  *    endorse or promote products derived from this software without
  28  *    prior written permission. For written permission, please contact
  29  *    licensing@OpenSSL.org.
  30  *
  31  * 5. Products derived from this software may not be called "OpenSSL"
  32  *    nor may "OpenSSL" appear in their names without prior written
  33  *    permission of the OpenSSL Project.
  34  *
  35  * 6. Redistributions of any form whatsoever must retain the following
  36  *    acknowledgment:
  37  *    "This product includes software developed by the OpenSSL Project
  38  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  39  *
  40  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  41  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  43  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  44  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  45  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  46  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  47  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  49  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  50  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  51  * OF THE POSSIBILITY OF SUCH DAMAGE.
  52  * ====================================================================
  53  *
  54  * This product includes cryptographic software written by Eric Young
  55  * (eay@cryptsoft.com).  This product includes software written by Tim
  56  * Hudson (tjh@cryptsoft.com).
  57  *
  58  */
  59 #ifndef OPENSSL_NO_SRP
  60 # include "internal/cryptlib.h"
  61 # include <openssl/sha.h>
  62 # include <openssl/srp.h>
  63 # include <openssl/evp.h>
  64 # include "internal/bn_srp.h"
  65
  66 static BIGNUM *srp_Calc_k(BIGNUM *N, BIGNUM *g)
  67 {
  68     /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
  69
  70     unsigned char digest[SHA_DIGEST_LENGTH];
  71     unsigned char *tmp;
  72     EVP_MD_CTX *ctxt = NULL;
  73     int longg;
  74     int longN = BN_num_bytes(N);
  75     BIGNUM *res = NULL;
  76
  77     if (BN_ucmp(g, N) >= 0)
  78         return NULL;
  79
  80     ctxt = EVP_MD_CTX_new();
  81     if (ctxt == NULL)
  82         return NULL;
  83     if ((tmp = OPENSSL_malloc(longN)) == NULL)
  84         goto err;
  85     BN_bn2bin(N, tmp);
  86
  87     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
  88     EVP_DigestUpdate(ctxt, tmp, longN);
  89
  90     memset(tmp, 0, longN);
  91     longg = BN_bn2bin(g, tmp);
  92     /* use the zeros behind to pad on left */
  93     EVP_DigestUpdate(ctxt, tmp + longg, longN - longg);
  94     EVP_DigestUpdate(ctxt, tmp, longg);
  95     OPENSSL_free(tmp);
  96
  97     EVP_DigestFinal_ex(ctxt, digest, NULL);
  98     res = BN_bin2bn(digest, sizeof(digest), NULL);
  99  err:
 100     EVP_MD_CTX_free(ctxt);
 101     return res;
 102 }
 103
 104 BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N)
 105 {
 106     /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
 107
 108     BIGNUM *u = NULL;
 109     unsigned char cu[SHA_DIGEST_LENGTH];
 110     unsigned char *cAB = NULL;
 111     EVP_MD_CTX *ctxt = NULL;
 112     int longN;
 113     if ((A == NULL) || (B == NULL) || (N == NULL))
 114         return NULL;
 115
 116     if (BN_ucmp(A, N) >= 0 || BN_ucmp(B, N) >= 0)
 117         return NULL;
 118
 119     longN = BN_num_bytes(N);
 120
 121     ctxt = EVP_MD_CTX_new();
 122     if (ctxt == NULL)
 123         return NULL;
 124     if ((cAB = OPENSSL_malloc(2 * longN)) == NULL)
 125         goto err;
 126
 127     memset(cAB, 0, longN);
 128
 129     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 130     EVP_DigestUpdate(ctxt, cAB + BN_bn2bin(A, cAB + longN), longN);
 131     EVP_DigestUpdate(ctxt, cAB + BN_bn2bin(B, cAB + longN), longN);
 132     OPENSSL_free(cAB);
 133     EVP_DigestFinal_ex(ctxt, cu, NULL);
 134
 135     if ((u = BN_bin2bn(cu, sizeof(cu), NULL)) == NULL)
 136         goto err;
 137     if (BN_is_zero(u)) {
 138         BN_free(u);
 139         u = NULL;
 140     }
 141  err:
 142     EVP_MD_CTX_free(ctxt);
 143
 144     return u;
 145 }
 146
 147 BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b,
 148                             BIGNUM *N)
 149 {
 150     BIGNUM *tmp = NULL, *S = NULL;
 151     BN_CTX *bn_ctx;
 152
 153     if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)
 154         return NULL;
 155
 156     if ((bn_ctx = BN_CTX_new()) == NULL ||
 157         (tmp = BN_new()) == NULL || (S = BN_new()) == NULL)
 158         goto err;
 159
 160     /* S = (A*v**u) ** b */
 161
 162     if (!BN_mod_exp(tmp, v, u, N, bn_ctx))
 163         goto err;
 164     if (!BN_mod_mul(tmp, A, tmp, N, bn_ctx))
 165         goto err;
 166     if (!BN_mod_exp(S, tmp, b, N, bn_ctx))
 167         goto err;
 168  err:
 169     BN_CTX_free(bn_ctx);
 170     BN_clear_free(tmp);
 171     return S;
 172 }
 173
 174 BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v)
 175 {
 176     BIGNUM *kv = NULL, *gb = NULL;
 177     BIGNUM *B = NULL, *k = NULL;
 178     BN_CTX *bn_ctx;
 179
 180     if (b == NULL || N == NULL || g == NULL || v == NULL ||
 181         (bn_ctx = BN_CTX_new()) == NULL)
 182         return NULL;
 183
 184     if ((kv = BN_new()) == NULL ||
 185         (gb = BN_new()) == NULL || (B = BN_new()) == NULL)
 186         goto err;
 187
 188     /* B = g**b + k*v */
 189
 190     if (!BN_mod_exp(gb, g, b, N, bn_ctx)
 191         || (k = srp_Calc_k(N, g)) == NULL
 192         || !BN_mod_mul(kv, v, k, N, bn_ctx)
 193         || !BN_mod_add(B, gb, kv, N, bn_ctx)) {
 194         BN_free(B);
 195         B = NULL;
 196     }
 197  err:
 198     BN_CTX_free(bn_ctx);
 199     BN_clear_free(kv);
 200     BN_clear_free(gb);
 201     BN_free(k);
 202     return B;
 203 }
 204
 205 BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass)
 206 {
 207     unsigned char dig[SHA_DIGEST_LENGTH];
 208     EVP_MD_CTX *ctxt;
 209     unsigned char *cs;
 210     BIGNUM *res = NULL;
 211
 212     if ((s == NULL) || (user == NULL) || (pass == NULL))
 213         return NULL;
 214
 215     ctxt = EVP_MD_CTX_new();
 216     if (ctxt == NULL)
 217         return NULL;
 218     if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)
 219         goto err;
 220
 221     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 222     EVP_DigestUpdate(ctxt, user, strlen(user));
 223     EVP_DigestUpdate(ctxt, ":", 1);
 224     EVP_DigestUpdate(ctxt, pass, strlen(pass));
 225     EVP_DigestFinal_ex(ctxt, dig, NULL);
 226
 227     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 228     BN_bn2bin(s, cs);
 229     EVP_DigestUpdate(ctxt, cs, BN_num_bytes(s));
 230     OPENSSL_free(cs);
 231     EVP_DigestUpdate(ctxt, dig, sizeof(dig));
 232     EVP_DigestFinal_ex(ctxt, dig, NULL);
 233
 234     res = BN_bin2bn(dig, sizeof(dig), NULL);
 235  err:
 236     EVP_MD_CTX_free(ctxt);
 237     return res;
 238 }
 239
 240 BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g)
 241 {
 242     BN_CTX *bn_ctx;
 243     BIGNUM *A = NULL;
 244
 245     if (a == NULL || N == NULL || g == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 246         return NULL;
 247
 248     if ((A = BN_new()) != NULL && !BN_mod_exp(A, g, a, N, bn_ctx)) {
 249         BN_free(A);
 250         A = NULL;
 251     }
 252     BN_CTX_free(bn_ctx);
 253     return A;
 254 }
 255
 256 BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x,
 257                             BIGNUM *a, BIGNUM *u)
 258 {
 259     BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;
 260     BN_CTX *bn_ctx;
 261
 262     if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL
 263         || a == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 264         return NULL;
 265
 266     if ((tmp = BN_new()) == NULL ||
 267         (tmp2 = BN_new()) == NULL ||
 268         (tmp3 = BN_new()) == NULL ||
 269         (K = BN_new()) == NULL)
 270         goto err;
 271
 272     if (!BN_mod_exp(tmp, g, x, N, bn_ctx))
 273         goto err;
 274     if ((k = srp_Calc_k(N, g)) == NULL)
 275         goto err;
 276     if (!BN_mod_mul(tmp2, tmp, k, N, bn_ctx))
 277         goto err;
 278     if (!BN_mod_sub(tmp, B, tmp2, N, bn_ctx))
 279         goto err;
 280     if (!BN_mod_mul(tmp3, u, x, N, bn_ctx))
 281         goto err;
 282     if (!BN_mod_add(tmp2, a, tmp3, N, bn_ctx))
 283         goto err;
 284     if (!BN_mod_exp(K, tmp, tmp2, N, bn_ctx))
 285         goto err;
 286
 287  err:
 288     BN_CTX_free(bn_ctx);
 289     BN_clear_free(tmp);
 290     BN_clear_free(tmp2);
 291     BN_clear_free(tmp3);
 292     BN_free(k);
 293     return K;
 294 }
 295
 296 int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N)
 297 {
 298     BIGNUM *r;
 299     BN_CTX *bn_ctx;
 300     int ret = 0;
 301
 302     if (B == NULL || N == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 303         return 0;
 304
 305     if ((r = BN_new()) == NULL)
 306         goto err;
 307     /* Checks if B % N == 0 */
 308     if (!BN_nnmod(r, B, N, bn_ctx))
 309         goto err;
 310     ret = !BN_is_zero(r);
 311  err:
 312     BN_CTX_free(bn_ctx);
 313     BN_free(r);
 314     return ret;
 315 }
 316
 317 int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N)
 318 {
 319     /* Checks if A % N == 0 */
 320     return SRP_Verify_B_mod_N(A, N);
 321 }
 322
 323 static SRP_gN knowngN[] = {
 324     {"8192", (BIGNUM *)&bn_generator_19, (BIGNUM *)&bn_group_8192},
 325     {"6144", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_6144},
 326     {"4096", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_4096},
 327     {"3072", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_3072},
 328     {"2048", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_2048},
 329     {"1536", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_1536},
 330     {"1024", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_1024},
 331 };
 332
 333 # define KNOWN_GN_NUMBER sizeof(knowngN) / sizeof(SRP_gN)
 334
 335 /*
 336  * Check if G and N are known parameters. The values have been generated
 337  * from the ietf-tls-srp draft version 8
 338  */
 339 char *SRP_check_known_gN_param(BIGNUM *g, BIGNUM *N)
 340 {
 341     size_t i;
 342     if ((g == NULL) || (N == NULL))
 343         return 0;
 344
 345     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
 346         if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)
 347             return knowngN[i].id;
 348     }
 349     return NULL;
 350 }
 351
 352 SRP_gN *SRP_get_default_gN(const char *id)
 353 {
 354     size_t i;
 355
 356     if (id == NULL)
 357         return knowngN;
 358     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
 359         if (strcmp(knowngN[i].id, id) == 0)
 360             return knowngN + i;
 361     }
 362     return NULL;
 363 }
 364 #endif