crypto/srp/srp_vfy.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 <openssl/buffer.h>
  65 # include <openssl/rand.h>
  66 # include <openssl/txt_db.h>
  67
  68 # define SRP_RANDOM_SALT_LEN 20
  69 # define MAX_LEN 2500
  70
  71 static char b64table[] =
  72     "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz./";
  73
  74 /*
  75  * the following two conversion routines have been inspired by code from
  76  * Stanford
  77  */
  78
  79 /*
  80  * Convert a base64 string into raw byte array representation.
  81  */
  82 static int t_fromb64(unsigned char *a, const char *src)
  83 {
  84     char *loc;
  85     int i, j;
  86     int size;
  87
  88     while (*src && (*src == ' ' || *src == '\t' || *src == '\n'))
  89         ++src;
  90     size = strlen(src);
  91     i = 0;
  92     while (i < size) {
  93         loc = strchr(b64table, src[i]);
  94         if (loc == (char *)0)
  95             break;
  96         else
  97             a[i] = loc - b64table;
  98         ++i;
  99     }
 100     /* if nothing valid to process we have a zero length response */
 101     if (i == 0)
 102         return 0;
 103     size = i;
 104     i = size - 1;
 105     j = size;
 106     while (1) {
 107         a[j] = a[i];
 108         if (--i < 0)
 109             break;
 110         a[j] |= (a[i] & 3) << 6;
 111         --j;
 112         a[j] = (unsigned char)((a[i] & 0x3c) >> 2);
 113         if (--i < 0)
 114             break;
 115         a[j] |= (a[i] & 0xf) << 4;
 116         --j;
 117         a[j] = (unsigned char)((a[i] & 0x30) >> 4);
 118         if (--i < 0)
 119             break;
 120         a[j] |= (a[i] << 2);
 121
 122         a[--j] = 0;
 123         if (--i < 0)
 124             break;
 125     }
 126     while (a[j] == 0 && j <= size)
 127         ++j;
 128     i = 0;
 129     while (j <= size)
 130         a[i++] = a[j++];
 131     return i;
 132 }
 133
 134 /*
 135  * Convert a raw byte string into a null-terminated base64 ASCII string.
 136  */
 137 static char *t_tob64(char *dst, const unsigned char *src, int size)
 138 {
 139     int c, pos = size % 3;
 140     unsigned char b0 = 0, b1 = 0, b2 = 0, notleading = 0;
 141     char *olddst = dst;
 142
 143     switch (pos) {
 144     case 1:
 145         b2 = src[0];
 146         break;
 147     case 2:
 148         b1 = src[0];
 149         b2 = src[1];
 150         break;
 151     }
 152
 153     while (1) {
 154         c = (b0 & 0xfc) >> 2;
 155         if (notleading || c != 0) {
 156             *dst++ = b64table[c];
 157             notleading = 1;
 158         }
 159         c = ((b0 & 3) << 4) | ((b1 & 0xf0) >> 4);
 160         if (notleading || c != 0) {
 161             *dst++ = b64table[c];
 162             notleading = 1;
 163         }
 164         c = ((b1 & 0xf) << 2) | ((b2 & 0xc0) >> 6);
 165         if (notleading || c != 0) {
 166             *dst++ = b64table[c];
 167             notleading = 1;
 168         }
 169         c = b2 & 0x3f;
 170         if (notleading || c != 0) {
 171             *dst++ = b64table[c];
 172             notleading = 1;
 173         }
 174         if (pos >= size)
 175             break;
 176         else {
 177             b0 = src[pos++];
 178             b1 = src[pos++];
 179             b2 = src[pos++];
 180         }
 181     }
 182
 183     *dst++ = '\0';
 184     return olddst;
 185 }
 186
 187 static void SRP_user_pwd_free(SRP_user_pwd *user_pwd)
 188 {
 189     if (user_pwd == NULL)
 190         return;
 191     BN_free(user_pwd->s);
 192     BN_clear_free(user_pwd->v);
 193     OPENSSL_free(user_pwd->id);
 194     OPENSSL_free(user_pwd->info);
 195     OPENSSL_free(user_pwd);
 196 }
 197
 198 static SRP_user_pwd *SRP_user_pwd_new(void)
 199 {
 200     SRP_user_pwd *ret = OPENSSL_malloc(sizeof(*ret));
 201     if (ret == NULL)
 202         return NULL;
 203     ret->N = NULL;
 204     ret->g = NULL;
 205     ret->s = NULL;
 206     ret->v = NULL;
 207     ret->id = NULL;
 208     ret->info = NULL;
 209     return ret;
 210 }
 211
 212 static void SRP_user_pwd_set_gN(SRP_user_pwd *vinfo, const BIGNUM *g,
 213                                 const BIGNUM *N)
 214 {
 215     vinfo->N = N;
 216     vinfo->g = g;
 217 }
 218
 219 static int SRP_user_pwd_set_ids(SRP_user_pwd *vinfo, const char *id,
 220                                 const char *info)
 221 {
 222     if (id != NULL && NULL == (vinfo->id = OPENSSL_strdup(id)))
 223         return 0;
 224     return (info == NULL || NULL != (vinfo->info = OPENSSL_strdup(info)));
 225 }
 226
 227 static int SRP_user_pwd_set_sv(SRP_user_pwd *vinfo, const char *s,
 228                                const char *v)
 229 {
 230     unsigned char tmp[MAX_LEN];
 231     int len;
 232
 233     if (strlen(s) > MAX_LEN || strlen(v) > MAX_LEN)
 234         return 0;
 235     len = t_fromb64(tmp, v);
 236     if (NULL == (vinfo->v = BN_bin2bn(tmp, len, NULL)))
 237         return 0;
 238     len = t_fromb64(tmp, s);
 239     return ((vinfo->s = BN_bin2bn(tmp, len, NULL)) != NULL);
 240 }
 241
 242 static int SRP_user_pwd_set_sv_BN(SRP_user_pwd *vinfo, BIGNUM *s, BIGNUM *v)
 243 {
 244     vinfo->v = v;
 245     vinfo->s = s;
 246     return (vinfo->s != NULL && vinfo->v != NULL);
 247 }
 248
 249 SRP_VBASE *SRP_VBASE_new(char *seed_key)
 250 {
 251     SRP_VBASE *vb = OPENSSL_malloc(sizeof(*vb));
 252
 253     if (vb == NULL)
 254         return NULL;
 255     if ((vb->users_pwd = sk_SRP_user_pwd_new_null()) == NULL
 256         || (vb->gN_cache = sk_SRP_gN_cache_new_null()) == NULL) {
 257         OPENSSL_free(vb);
 258         return NULL;
 259     }
 260     vb->default_g = NULL;
 261     vb->default_N = NULL;
 262     vb->seed_key = NULL;
 263     if ((seed_key != NULL) && (vb->seed_key = OPENSSL_strdup(seed_key)) == NULL) {
 264         sk_SRP_user_pwd_free(vb->users_pwd);
 265         sk_SRP_gN_cache_free(vb->gN_cache);
 266         OPENSSL_free(vb);
 267         return NULL;
 268     }
 269     return vb;
 270 }
 271
 272 void SRP_VBASE_free(SRP_VBASE *vb)
 273 {
 274     if (!vb)
 275         return;
 276     sk_SRP_user_pwd_pop_free(vb->users_pwd, SRP_user_pwd_free);
 277     sk_SRP_gN_cache_free(vb->gN_cache);
 278     OPENSSL_free(vb->seed_key);
 279     OPENSSL_free(vb);
 280 }
 281
 282 static SRP_gN_cache *SRP_gN_new_init(const char *ch)
 283 {
 284     unsigned char tmp[MAX_LEN];
 285     int len;
 286     SRP_gN_cache *newgN = OPENSSL_malloc(sizeof(*newgN));
 287
 288     if (newgN == NULL)
 289         return NULL;
 290
 291     if ((newgN->b64_bn = OPENSSL_strdup(ch)) == NULL)
 292         goto err;
 293
 294     len = t_fromb64(tmp, ch);
 295     if ((newgN->bn = BN_bin2bn(tmp, len, NULL)))
 296         return newgN;
 297
 298     OPENSSL_free(newgN->b64_bn);
 299  err:
 300     OPENSSL_free(newgN);
 301     return NULL;
 302 }
 303
 304 static void SRP_gN_free(SRP_gN_cache *gN_cache)
 305 {
 306     if (gN_cache == NULL)
 307         return;
 308     OPENSSL_free(gN_cache->b64_bn);
 309     BN_free(gN_cache->bn);
 310     OPENSSL_free(gN_cache);
 311 }
 312
 313 static SRP_gN *SRP_get_gN_by_id(const char *id, STACK_OF(SRP_gN) *gN_tab)
 314 {
 315     int i;
 316
 317     SRP_gN *gN;
 318     if (gN_tab != NULL)
 319         for (i = 0; i < sk_SRP_gN_num(gN_tab); i++) {
 320             gN = sk_SRP_gN_value(gN_tab, i);
 321             if (gN && (id == NULL || strcmp(gN->id, id) == 0))
 322                 return gN;
 323         }
 324
 325     return SRP_get_default_gN(id);
 326 }
 327
 328 static BIGNUM *SRP_gN_place_bn(STACK_OF(SRP_gN_cache) *gN_cache, char *ch)
 329 {
 330     int i;
 331     if (gN_cache == NULL)
 332         return NULL;
 333
 334     /* search if we have already one... */
 335     for (i = 0; i < sk_SRP_gN_cache_num(gN_cache); i++) {
 336         SRP_gN_cache *cache = sk_SRP_gN_cache_value(gN_cache, i);
 337         if (strcmp(cache->b64_bn, ch) == 0)
 338             return cache->bn;
 339     }
 340     {                           /* it is the first time that we find it */
 341         SRP_gN_cache *newgN = SRP_gN_new_init(ch);
 342         if (newgN) {
 343             if (sk_SRP_gN_cache_insert(gN_cache, newgN, 0) > 0)
 344                 return newgN->bn;
 345             SRP_gN_free(newgN);
 346         }
 347     }
 348     return NULL;
 349 }
 350
 351 /*
 352  * this function parses verifier file. Format is:
 353  * string(index):base64(N):base64(g):0
 354  * string(username):base64(v):base64(salt):int(index)
 355  */
 356
 357 int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file)
 358 {
 359     int error_code;
 360     STACK_OF(SRP_gN) *SRP_gN_tab = sk_SRP_gN_new_null();
 361     char *last_index = NULL;
 362     int i;
 363     char **pp;
 364
 365     SRP_gN *gN = NULL;
 366     SRP_user_pwd *user_pwd = NULL;
 367
 368     TXT_DB *tmpdb = NULL;
 369     BIO *in = BIO_new(BIO_s_file());
 370
 371     error_code = SRP_ERR_OPEN_FILE;
 372
 373     if (in == NULL || BIO_read_filename(in, verifier_file) <= 0)
 374         goto err;
 375
 376     error_code = SRP_ERR_VBASE_INCOMPLETE_FILE;
 377
 378     if ((tmpdb = TXT_DB_read(in, DB_NUMBER)) == NULL)
 379         goto err;
 380
 381     error_code = SRP_ERR_MEMORY;
 382
 383     if (vb->seed_key) {
 384         last_index = SRP_get_default_gN(NULL)->id;
 385     }
 386     for (i = 0; i < sk_OPENSSL_PSTRING_num(tmpdb->data); i++) {
 387         pp = sk_OPENSSL_PSTRING_value(tmpdb->data, i);
 388         if (pp[DB_srptype][0] == DB_SRP_INDEX) {
 389             /*
 390              * we add this couple in the internal Stack
 391              */
 392
 393             if ((gN = OPENSSL_malloc(sizeof(*gN))) == NULL)
 394                 goto err;
 395
 396             if ((gN->id = OPENSSL_strdup(pp[DB_srpid])) == NULL
 397                 || (gN->N = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpverifier]))
 398                         == NULL
 399                 || (gN->g = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpsalt]))
 400                         == NULL
 401                 || sk_SRP_gN_insert(SRP_gN_tab, gN, 0) == 0)
 402                 goto err;
 403
 404             gN = NULL;
 405
 406             if (vb->seed_key != NULL) {
 407                 last_index = pp[DB_srpid];
 408             }
 409         } else if (pp[DB_srptype][0] == DB_SRP_VALID) {
 410             /* it is a user .... */
 411             const SRP_gN *lgN;
 412
 413             if ((lgN = SRP_get_gN_by_id(pp[DB_srpgN], SRP_gN_tab)) != NULL) {
 414                 error_code = SRP_ERR_MEMORY;
 415                 if ((user_pwd = SRP_user_pwd_new()) == NULL)
 416                     goto err;
 417
 418                 SRP_user_pwd_set_gN(user_pwd, lgN->g, lgN->N);
 419                 if (!SRP_user_pwd_set_ids
 420                     (user_pwd, pp[DB_srpid], pp[DB_srpinfo]))
 421                     goto err;
 422
 423                 error_code = SRP_ERR_VBASE_BN_LIB;
 424                 if (!SRP_user_pwd_set_sv
 425                     (user_pwd, pp[DB_srpsalt], pp[DB_srpverifier]))
 426                     goto err;
 427
 428                 if (sk_SRP_user_pwd_insert(vb->users_pwd, user_pwd, 0) == 0)
 429                     goto err;
 430                 user_pwd = NULL; /* abandon responsability */
 431             }
 432         }
 433     }
 434
 435     if (last_index != NULL) {
 436         /* this means that we want to simulate a default user */
 437
 438         if (((gN = SRP_get_gN_by_id(last_index, SRP_gN_tab)) == NULL)) {
 439             error_code = SRP_ERR_VBASE_BN_LIB;
 440             goto err;
 441         }
 442         vb->default_g = gN->g;
 443         vb->default_N = gN->N;
 444         gN = NULL;
 445     }
 446     error_code = SRP_NO_ERROR;
 447
 448  err:
 449     /*
 450      * there may be still some leaks to fix, if this fails, the application
 451      * terminates most likely
 452      */
 453
 454     if (gN != NULL) {
 455         OPENSSL_free(gN->id);
 456         OPENSSL_free(gN);
 457     }
 458
 459     SRP_user_pwd_free(user_pwd);
 460
 461     TXT_DB_free(tmpdb);
 462     BIO_free_all(in);
 463
 464     sk_SRP_gN_free(SRP_gN_tab);
 465
 466     return error_code;
 467
 468 }
 469
 470 SRP_user_pwd *SRP_VBASE_get_by_user(SRP_VBASE *vb, char *username)
 471 {
 472     int i;
 473     SRP_user_pwd *user;
 474     unsigned char digv[SHA_DIGEST_LENGTH];
 475     unsigned char digs[SHA_DIGEST_LENGTH];
 476     EVP_MD_CTX *ctxt = NULL;
 477
 478     if (vb == NULL)
 479         return NULL;
 480     for (i = 0; i < sk_SRP_user_pwd_num(vb->users_pwd); i++) {
 481         user = sk_SRP_user_pwd_value(vb->users_pwd, i);
 482         if (strcmp(user->id, username) == 0)
 483             return user;
 484     }
 485     if ((vb->seed_key == NULL) ||
 486         (vb->default_g == NULL) || (vb->default_N == NULL))
 487         return NULL;
 488
 489 /* if the user is unknown we set parameters as well if we have a seed_key */
 490
 491     if ((user = SRP_user_pwd_new()) == NULL)
 492         return NULL;
 493
 494     SRP_user_pwd_set_gN(user, vb->default_g, vb->default_N);
 495
 496     if (!SRP_user_pwd_set_ids(user, username, NULL))
 497         goto err;
 498
 499     if (RAND_bytes(digv, SHA_DIGEST_LENGTH) <= 0)
 500         goto err;
 501     ctxt = EVP_MD_CTX_new();
 502     EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL);
 503     EVP_DigestUpdate(ctxt, vb->seed_key, strlen(vb->seed_key));
 504     EVP_DigestUpdate(ctxt, username, strlen(username));
 505     EVP_DigestFinal_ex(ctxt, digs, NULL);
 506     EVP_MD_CTX_free(ctxt);
 507     ctxt = NULL;
 508     if (SRP_user_pwd_set_sv_BN(user,
 509                                BN_bin2bn(digs, SHA_DIGEST_LENGTH, NULL),
 510                                BN_bin2bn(digv, SHA_DIGEST_LENGTH, NULL)))
 511         return user;
 512
 513  err:
 514     EVP_MD_CTX_free(ctxt);
 515     SRP_user_pwd_free(user);
 516     return NULL;
 517 }
 518
 519 /*
 520  * create a verifier (*salt,*verifier,g and N are in base64)
 521  */
 522 char *SRP_create_verifier(const char *user, const char *pass, char **salt,
 523                           char **verifier, const char *N, const char *g)
 524 {
 525     int len;
 526     char *result = NULL, *vf = NULL;
 527     BIGNUM *N_bn = NULL, *g_bn = NULL, *s = NULL, *v = NULL;
 528     unsigned char tmp[MAX_LEN];
 529     unsigned char tmp2[MAX_LEN];
 530     char *defgNid = NULL;
 531     int vfsize = 0;
 532
 533     if ((user == NULL) ||
 534         (pass == NULL) || (salt == NULL) || (verifier == NULL))
 535         goto err;
 536
 537     if (N) {
 538         if ((len = t_fromb64(tmp, N)) == 0)
 539             goto err;
 540         N_bn = BN_bin2bn(tmp, len, NULL);
 541         if ((len = t_fromb64(tmp, g)) == 0)
 542             goto err;
 543         g_bn = BN_bin2bn(tmp, len, NULL);
 544         defgNid = "*";
 545     } else {
 546         SRP_gN *gN = SRP_get_gN_by_id(g, NULL);
 547         if (gN == NULL)
 548             goto err;
 549         N_bn = gN->N;
 550         g_bn = gN->g;
 551         defgNid = gN->id;
 552     }
 553
 554     if (*salt == NULL) {
 555         if (RAND_bytes(tmp2, SRP_RANDOM_SALT_LEN) <= 0)
 556             goto err;
 557
 558         s = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);
 559     } else {
 560         if ((len = t_fromb64(tmp2, *salt)) == 0)
 561             goto err;
 562         s = BN_bin2bn(tmp2, len, NULL);
 563     }
 564
 565     if (!SRP_create_verifier_BN(user, pass, &s, &v, N_bn, g_bn))
 566         goto err;
 567
 568     BN_bn2bin(v, tmp);
 569     vfsize = BN_num_bytes(v) * 2;
 570     if (((vf = OPENSSL_malloc(vfsize)) == NULL))
 571         goto err;
 572     t_tob64(vf, tmp, BN_num_bytes(v));
 573
 574     if (*salt == NULL) {
 575         char *tmp_salt;
 576
 577         if ((tmp_salt = OPENSSL_malloc(SRP_RANDOM_SALT_LEN * 2)) == NULL) {
 578             goto err;
 579         }
 580         t_tob64(tmp_salt, tmp2, SRP_RANDOM_SALT_LEN);
 581         *salt = tmp_salt;
 582     }
 583
 584     *verifier = vf;
 585     vf = NULL;
 586     result = defgNid;
 587
 588  err:
 589     if (N) {
 590         BN_free(N_bn);
 591         BN_free(g_bn);
 592     }
 593     OPENSSL_clear_free(vf, vfsize);
 594     BN_clear_free(s);
 595     BN_clear_free(v);
 596     return result;
 597 }
 598
 599 /*
 600  * create a verifier (*salt,*verifier,g and N are BIGNUMs). If *salt != NULL
 601  * then the provided salt will be used. On successful exit *verifier will point
 602  * to a newly allocated BIGNUM containing the verifier and (if a salt was not
 603  * provided) *salt will be populated with a newly allocated BIGNUM containing a
 604  * random salt.
 605  * The caller is responsible for freeing the allocated *salt and *verifier
 606  * BIGNUMS.
 607  */
 608 int SRP_create_verifier_BN(const char *user, const char *pass, BIGNUM **salt,
 609                            BIGNUM **verifier, const BIGNUM *N,
 610                            const BIGNUM *g)
 611 {
 612     int result = 0;
 613     BIGNUM *x = NULL;
 614     BN_CTX *bn_ctx = BN_CTX_new();
 615     unsigned char tmp2[MAX_LEN];
 616     BIGNUM *salttmp = NULL;
 617
 618     if ((user == NULL) ||
 619         (pass == NULL) ||
 620         (salt == NULL) ||
 621         (verifier == NULL) || (N == NULL) || (g == NULL) || (bn_ctx == NULL))
 622         goto err;
 623
 624     if (*salt == NULL) {
 625         if (RAND_bytes(tmp2, SRP_RANDOM_SALT_LEN) <= 0)
 626             goto err;
 627
 628         salttmp = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);
 629     } else {
 630         salttmp = *salt;
 631     }
 632
 633     x = SRP_Calc_x(salttmp, user, pass);
 634
 635     *verifier = BN_new();
 636     if (*verifier == NULL)
 637         goto err;
 638
 639     if (!BN_mod_exp(*verifier, g, x, N, bn_ctx)) {
 640         BN_clear_free(*verifier);
 641         goto err;
 642     }
 643
 644     result = 1;
 645     *salt = salttmp;
 646
 647  err:
 648     if (salt != NULL && *salt != salttmp)
 649         BN_clear_free(salttmp);
 650     BN_clear_free(x);
 651     BN_CTX_free(bn_ctx);
 652     return result;
 653 }
 654
 655 #endif