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 "internal/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 = NULL;
  74     int longg;
  75     int longN = BN_num_bytes(N);
  76     BIGNUM *res = NULL;
  77
  78     if (BN_ucmp(g, N) >= 0)
  79         return NULL;
  80
  81     ctxt = EVP_MD_CTX_new();
  82     if (ctxt == NULL)
  83         return NULL;
  84     if ((tmp = OPENSSL_malloc(longN)) == NULL)
  85         goto err;
  86     BN_bn2bin(N, tmp);
  87
  88     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
  89     EVP_DigestUpdate(ctxt, tmp, longN);
  90
  91     memset(tmp, 0, longN);
  92     longg = BN_bn2bin(g, tmp);
  93     /* use the zeros behind to pad on left */
  94     EVP_DigestUpdate(ctxt, tmp + longg, longN - longg);
  95     EVP_DigestUpdate(ctxt, tmp, longg);
  96     OPENSSL_free(tmp);
  97
  98     EVP_DigestFinal_ex(ctxt, digest, NULL);
  99     res = BN_bin2bn(digest, sizeof(digest), NULL);
 100  err:
 101     EVP_MD_CTX_free(ctxt);
 102     return res;
 103 }
 104
 105 BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N)
 106 {
 107     /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
 108
 109     BIGNUM *u = NULL;
 110     unsigned char cu[SHA_DIGEST_LENGTH];
 111     unsigned char *cAB = NULL;
 112     EVP_MD_CTX *ctxt = NULL;
 113     int longN;
 114     if ((A == NULL) || (B == NULL) || (N == NULL))
 115         return NULL;
 116
 117     if (BN_ucmp(A, N) >= 0 || BN_ucmp(B, N) >= 0)
 118         return NULL;
 119
 120     longN = BN_num_bytes(N);
 121
 122     ctxt = EVP_MD_CTX_new();
 123     if (ctxt == NULL)
 124         return NULL;
 125     if ((cAB = OPENSSL_malloc(2 * longN)) == NULL)
 126         goto err;
 127
 128     memset(cAB, 0, longN);
 129
 130     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 131     EVP_DigestUpdate(ctxt, cAB + BN_bn2bin(A, cAB + longN), longN);
 132     EVP_DigestUpdate(ctxt, cAB + BN_bn2bin(B, cAB + longN), longN);
 133     OPENSSL_free(cAB);
 134     EVP_DigestFinal_ex(ctxt, cu, NULL);
 135
 136     if ((u = BN_bin2bn(cu, sizeof(cu), NULL)) == NULL)
 137         goto err;
 138     if (BN_is_zero(u)) {
 139         BN_free(u);
 140         u = NULL;
 141     }
 142  err:
 143     EVP_MD_CTX_free(ctxt);
 144
 145     return u;
 146 }
 147
 148 BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b,
 149                             BIGNUM *N)
 150 {
 151     BIGNUM *tmp = NULL, *S = NULL;
 152     BN_CTX *bn_ctx;
 153
 154     if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)
 155         return NULL;
 156
 157     if ((bn_ctx = BN_CTX_new()) == NULL ||
 158         (tmp = BN_new()) == NULL || (S = BN_new()) == NULL)
 159         goto err;
 160
 161     /* S = (A*v**u) ** b */
 162
 163     if (!BN_mod_exp(tmp, v, u, N, bn_ctx))
 164         goto err;
 165     if (!BN_mod_mul(tmp, A, tmp, N, bn_ctx))
 166         goto err;
 167     if (!BN_mod_exp(S, tmp, b, N, bn_ctx))
 168         goto err;
 169  err:
 170     BN_CTX_free(bn_ctx);
 171     BN_clear_free(tmp);
 172     return S;
 173 }
 174
 175 BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v)
 176 {
 177     BIGNUM *kv = NULL, *gb = NULL;
 178     BIGNUM *B = NULL, *k = NULL;
 179     BN_CTX *bn_ctx;
 180
 181     if (b == NULL || N == NULL || g == NULL || v == NULL ||
 182         (bn_ctx = BN_CTX_new()) == NULL)
 183         return NULL;
 184
 185     if ((kv = BN_new()) == NULL ||
 186         (gb = BN_new()) == NULL || (B = BN_new()) == NULL)
 187         goto err;
 188
 189     /* B = g**b + k*v */
 190
 191     if (!BN_mod_exp(gb, g, b, N, bn_ctx)
 192         || (k = srp_Calc_k(N, g)) == NULL
 193         || !BN_mod_mul(kv, v, k, N, bn_ctx)
 194         || !BN_mod_add(B, gb, kv, N, bn_ctx)) {
 195         BN_free(B);
 196         B = NULL;
 197     }
 198  err:
 199     BN_CTX_free(bn_ctx);
 200     BN_clear_free(kv);
 201     BN_clear_free(gb);
 202     BN_free(k);
 203     return B;
 204 }
 205
 206 BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass)
 207 {
 208     unsigned char dig[SHA_DIGEST_LENGTH];
 209     EVP_MD_CTX *ctxt;
 210     unsigned char *cs;
 211     BIGNUM *res = NULL;
 212
 213     if ((s == NULL) || (user == NULL) || (pass == NULL))
 214         return NULL;
 215
 216     ctxt = EVP_MD_CTX_new();
 217     if (ctxt == NULL)
 218         return NULL;
 219     if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)
 220         goto err;
 221
 222     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 223     EVP_DigestUpdate(ctxt, user, strlen(user));
 224     EVP_DigestUpdate(ctxt, ":", 1);
 225     EVP_DigestUpdate(ctxt, pass, strlen(pass));
 226     EVP_DigestFinal_ex(ctxt, dig, NULL);
 227
 228     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 229     BN_bn2bin(s, cs);
 230     EVP_DigestUpdate(ctxt, cs, BN_num_bytes(s));
 231     OPENSSL_free(cs);
 232     EVP_DigestUpdate(ctxt, dig, sizeof(dig));
 233     EVP_DigestFinal_ex(ctxt, dig, NULL);
 234
 235     res = BN_bin2bn(dig, sizeof(dig), NULL);
 236  err:
 237     EVP_MD_CTX_free(ctxt);
 238     return res;
 239 }
 240
 241 BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g)
 242 {
 243     BN_CTX *bn_ctx;
 244     BIGNUM *A = NULL;
 245
 246     if (a == NULL || N == NULL || g == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 247         return NULL;
 248
 249     if ((A = BN_new()) != NULL && !BN_mod_exp(A, g, a, N, bn_ctx)) {
 250         BN_free(A);
 251         A = NULL;
 252     }
 253     BN_CTX_free(bn_ctx);
 254     return A;
 255 }
 256
 257 BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x,
 258                             BIGNUM *a, BIGNUM *u)
 259 {
 260     BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;
 261     BN_CTX *bn_ctx;
 262
 263     if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL
 264         || a == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 265         return NULL;
 266
 267     if ((tmp = BN_new()) == NULL ||
 268         (tmp2 = BN_new()) == NULL ||
 269         (tmp3 = BN_new()) == NULL ||
 270         (K = BN_new()) == NULL)
 271         goto err;
 272
 273     if (!BN_mod_exp(tmp, g, x, N, bn_ctx))
 274         goto err;
 275     if ((k = srp_Calc_k(N, g)) == NULL)
 276         goto err;
 277     if (!BN_mod_mul(tmp2, tmp, k, N, bn_ctx))
 278         goto err;
 279     if (!BN_mod_sub(tmp, B, tmp2, N, bn_ctx))
 280         goto err;
 281     if (!BN_mod_mul(tmp3, u, x, N, bn_ctx))
 282         goto err;
 283     if (!BN_mod_add(tmp2, a, tmp3, N, bn_ctx))
 284         goto err;
 285     if (!BN_mod_exp(K, tmp, tmp2, N, bn_ctx))
 286         goto err;
 287
 288  err:
 289     BN_CTX_free(bn_ctx);
 290     BN_clear_free(tmp);
 291     BN_clear_free(tmp2);
 292     BN_clear_free(tmp3);
 293     BN_free(k);
 294     return K;
 295 }
 296
 297 int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N)
 298 {
 299     BIGNUM *r;
 300     BN_CTX *bn_ctx;
 301     int ret = 0;
 302
 303     if (B == NULL || N == NULL || (bn_ctx = BN_CTX_new()) == NULL)
 304         return 0;
 305
 306     if ((r = BN_new()) == NULL)
 307         goto err;
 308     /* Checks if B % N == 0 */
 309     if (!BN_nnmod(r, B, N, bn_ctx))
 310         goto err;
 311     ret = !BN_is_zero(r);
 312  err:
 313     BN_CTX_free(bn_ctx);
 314     BN_free(r);
 315     return ret;
 316 }
 317
 318 int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N)
 319 {
 320     /* Checks if A % N == 0 */
 321     return SRP_Verify_B_mod_N(A, N);
 322 }
 323
 324 static SRP_gN knowngN[] = {
 325     {"8192", (BIGNUM *)&bn_generator_19, (BIGNUM *)&bn_group_8192},
 326     {"6144", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_6144},
 327     {"4096", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_4096},
 328     {"3072", (BIGNUM *)&bn_generator_5, (BIGNUM *)&bn_group_3072},
 329     {"2048", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_2048},
 330     {"1536", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_1536},
 331     {"1024", (BIGNUM *)&bn_generator_2, (BIGNUM *)&bn_group_1024},
 332 };
 333
 334 # define KNOWN_GN_NUMBER sizeof(knowngN) / sizeof(SRP_gN)
 335
 336 /*
 337  * Check if G and N are kwown parameters. The values have been generated
 338  * from the ietf-tls-srp draft version 8
 339  */
 340 char *SRP_check_known_gN_param(BIGNUM *g, BIGNUM *N)
 341 {
 342     size_t i;
 343     if ((g == NULL) || (N == NULL))
 344         return 0;
 345
 346     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
 347         if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)
 348             return knowngN[i].id;
 349     }
 350     return NULL;
 351 }
 352
 353 SRP_gN *SRP_get_default_gN(const char *id)
 354 {
 355     size_t i;
 356
 357     if (id == NULL)
 358         return knowngN;
 359     for (i = 0; i < KNOWN_GN_NUMBER; i++) {
 360         if (strcmp(knowngN[i].id, id) == 0)
 361             return knowngN + i;
 362     }
 363     return NULL;
 364 }
 365 #endif