crypto/srp/srp_vfy.c

   1 /*
   2  * Copyright 2004-2023 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright (c) 2004, EdelKey Project. All Rights Reserved.
   4  *
   5  * Licensed under the Apache License 2.0 (the "License").  You may not use
   6  * this file except in compliance with the License.  You can obtain a copy
   7  * in the file LICENSE in the source distribution or at
   8  * https://www.openssl.org/source/license.html
   9  *
  10  * Originally written by Christophe Renou and Peter Sylvester,
  11  * for the EdelKey project.
  12  */
  13
  14 /* All the SRP APIs in this file are deprecated */
  15 #define OPENSSL_SUPPRESS_DEPRECATED
  16
  17 #ifndef OPENSSL_NO_SRP
  18 # include "internal/cryptlib.h"
  19 # include "crypto/evp.h"
  20 # include <openssl/sha.h>
  21 # include <openssl/srp.h>
  22 # include <openssl/evp.h>
  23 # include <openssl/buffer.h>
  24 # include <openssl/rand.h>
  25 # include <openssl/txt_db.h>
  26 # include <openssl/err.h>
  27
  28 # define SRP_RANDOM_SALT_LEN 20
  29 # define MAX_LEN 2500
  30
  31 /*
  32  * Note that SRP uses its own variant of base 64 encoding. A different base64
  33  * alphabet is used and no padding '=' characters are added. Instead we pad to
  34  * the front with 0 bytes and subsequently strip off leading encoded padding.
  35  * This variant is used for compatibility with other SRP implementations -
  36  * notably libsrp, but also others. It is also required for backwards
  37  * compatibility in order to load verifier files from other OpenSSL versions.
  38  */
  39
  40 /*
  41  * Convert a base64 string into raw byte array representation.
  42  * Returns the length of the decoded data, or -1 on error.
  43  */
  44 static int t_fromb64(unsigned char *a, size_t alen, const char *src)
  45 {
  46     EVP_ENCODE_CTX *ctx;
  47     int outl = 0, outl2 = 0;
  48     size_t size, padsize;
  49     const unsigned char *pad = (const unsigned char *)"00";
  50
  51     while (*src == ' ' || *src == '\t' || *src == '\n')
  52         ++src;
  53     size = strlen(src);
  54     padsize = 4 - (size & 3);
  55     padsize &= 3;
  56
  57     /* Four bytes in src become three bytes output. */
  58     if (size > INT_MAX || ((size + padsize) / 4) * 3 > alen)
  59         return -1;
  60
  61     ctx = EVP_ENCODE_CTX_new();
  62     if (ctx == NULL)
  63         return -1;
  64
  65     /*
  66      * This should never occur because 1 byte of data always requires 2 bytes of
  67      * encoding, i.e.
  68      *  0 bytes unencoded = 0 bytes encoded
  69      *  1 byte unencoded  = 2 bytes encoded
  70      *  2 bytes unencoded = 3 bytes encoded
  71      *  3 bytes unencoded = 4 bytes encoded
  72      *  4 bytes unencoded = 6 bytes encoded
  73      *  etc
  74      */
  75     if (padsize == 3) {
  76         outl = -1;
  77         goto err;
  78     }
  79
  80     /* Valid padsize values are now 0, 1 or 2 */
  81
  82     EVP_DecodeInit(ctx);
  83     evp_encode_ctx_set_flags(ctx, EVP_ENCODE_CTX_USE_SRP_ALPHABET);
  84
  85     /* Add any encoded padding that is required */
  86     if (padsize != 0
  87             && EVP_DecodeUpdate(ctx, a, &outl, pad, padsize) < 0) {
  88         outl = -1;
  89         goto err;
  90     }
  91     if (EVP_DecodeUpdate(ctx, a, &outl2, (const unsigned char *)src, size) < 0) {
  92         outl = -1;
  93         goto err;
  94     }
  95     outl += outl2;
  96     EVP_DecodeFinal(ctx, a + outl, &outl2);
  97     outl += outl2;
  98
  99     /* Strip off the leading padding */
 100     if (padsize != 0) {
 101         if ((int)padsize >= outl) {
 102             outl = -1;
 103             goto err;
 104         }
 105
 106         /*
 107          * If we added 1 byte of padding prior to encoding then we have 2 bytes
 108          * of "real" data which gets spread across 4 encoded bytes like this:
 109          *   (6 bits pad)(2 bits pad | 4 bits data)(6 bits data)(6 bits data)
 110          * So 1 byte of pre-encoding padding results in 1 full byte of encoded
 111          * padding.
 112          * If we added 2 bytes of padding prior to encoding this gets encoded
 113          * as:
 114          *   (6 bits pad)(6 bits pad)(4 bits pad | 2 bits data)(6 bits data)
 115          * So 2 bytes of pre-encoding padding results in 2 full bytes of encoded
 116          * padding, i.e. we have to strip the same number of bytes of padding
 117          * from the encoded data as we added to the pre-encoded data.
 118          */
 119         memmove(a, a + padsize, outl - padsize);
 120         outl -= padsize;
 121     }
 122
 123  err:
 124     EVP_ENCODE_CTX_free(ctx);
 125
 126     return outl;
 127 }
 128
 129 /*
 130  * Convert a raw byte string into a null-terminated base64 ASCII string.
 131  * Returns 1 on success or 0 on error.
 132  */
 133 static int t_tob64(char *dst, const unsigned char *src, int size)
 134 {
 135     EVP_ENCODE_CTX *ctx = EVP_ENCODE_CTX_new();
 136     int outl = 0, outl2 = 0;
 137     unsigned char pad[2] = {0, 0};
 138     size_t leadz = 0;
 139
 140     if (ctx == NULL)
 141         return 0;
 142
 143     EVP_EncodeInit(ctx);
 144     evp_encode_ctx_set_flags(ctx, EVP_ENCODE_CTX_NO_NEWLINES
 145                                   | EVP_ENCODE_CTX_USE_SRP_ALPHABET);
 146
 147     /*
 148      * We pad at the front with zero bytes until the length is a multiple of 3
 149      * so that EVP_EncodeUpdate/EVP_EncodeFinal does not add any of its own "="
 150      * padding
 151      */
 152     leadz = 3 - (size % 3);
 153     if (leadz != 3
 154             && !EVP_EncodeUpdate(ctx, (unsigned char *)dst, &outl, pad,
 155                                  leadz)) {
 156         EVP_ENCODE_CTX_free(ctx);
 157         return 0;
 158     }
 159
 160     if (!EVP_EncodeUpdate(ctx, (unsigned char *)dst + outl, &outl2, src,
 161                           size)) {
 162         EVP_ENCODE_CTX_free(ctx);
 163         return 0;
 164     }
 165     outl += outl2;
 166     EVP_EncodeFinal(ctx, (unsigned char *)dst + outl, &outl2);
 167     outl += outl2;
 168
 169     /* Strip the encoded padding at the front */
 170     if (leadz != 3) {
 171         memmove(dst, dst + leadz, outl - leadz);
 172         dst[outl - leadz] = '\0';
 173     }
 174
 175     EVP_ENCODE_CTX_free(ctx);
 176     return 1;
 177 }
 178
 179 void SRP_user_pwd_free(SRP_user_pwd *user_pwd)
 180 {
 181     if (user_pwd == NULL)
 182         return;
 183     BN_free(user_pwd->s);
 184     BN_clear_free(user_pwd->v);
 185     OPENSSL_free(user_pwd->id);
 186     OPENSSL_free(user_pwd->info);
 187     OPENSSL_free(user_pwd);
 188 }
 189
 190 SRP_user_pwd *SRP_user_pwd_new(void)
 191 {
 192     SRP_user_pwd *ret;
 193
 194     if ((ret = OPENSSL_malloc(sizeof(*ret))) == NULL)
 195         return NULL;
 196     ret->N = NULL;
 197     ret->g = NULL;
 198     ret->s = NULL;
 199     ret->v = NULL;
 200     ret->id = NULL;
 201     ret->info = NULL;
 202     return ret;
 203 }
 204
 205 void SRP_user_pwd_set_gN(SRP_user_pwd *vinfo, const BIGNUM *g,
 206                          const BIGNUM *N)
 207 {
 208     vinfo->N = N;
 209     vinfo->g = g;
 210 }
 211
 212 int SRP_user_pwd_set1_ids(SRP_user_pwd *vinfo, const char *id,
 213                           const char *info)
 214 {
 215     OPENSSL_free(vinfo->id);
 216     OPENSSL_free(vinfo->info);
 217     if (id != NULL && NULL == (vinfo->id = OPENSSL_strdup(id)))
 218         return 0;
 219     return (info == NULL || NULL != (vinfo->info = OPENSSL_strdup(info)));
 220 }
 221
 222 static int SRP_user_pwd_set_sv(SRP_user_pwd *vinfo, const char *s,
 223                                const char *v)
 224 {
 225     unsigned char tmp[MAX_LEN];
 226     int len;
 227
 228     vinfo->v = NULL;
 229     vinfo->s = NULL;
 230
 231     len = t_fromb64(tmp, sizeof(tmp), v);
 232     if (len < 0)
 233         return 0;
 234     if (NULL == (vinfo->v = BN_bin2bn(tmp, len, NULL)))
 235         return 0;
 236     len = t_fromb64(tmp, sizeof(tmp), s);
 237     if (len < 0)
 238         goto err;
 239     vinfo->s = BN_bin2bn(tmp, len, NULL);
 240     if (vinfo->s == NULL)
 241         goto err;
 242     return 1;
 243  err:
 244     BN_free(vinfo->v);
 245     vinfo->v = NULL;
 246     return 0;
 247 }
 248
 249 int SRP_user_pwd_set0_sv(SRP_user_pwd *vinfo, BIGNUM *s, BIGNUM *v)
 250 {
 251     BN_free(vinfo->s);
 252     BN_clear_free(vinfo->v);
 253     vinfo->v = v;
 254     vinfo->s = s;
 255     return (vinfo->s != NULL && vinfo->v != NULL);
 256 }
 257
 258 static SRP_user_pwd *srp_user_pwd_dup(SRP_user_pwd *src)
 259 {
 260     SRP_user_pwd *ret;
 261
 262     if (src == NULL)
 263         return NULL;
 264     if ((ret = SRP_user_pwd_new()) == NULL)
 265         return NULL;
 266
 267     SRP_user_pwd_set_gN(ret, src->g, src->N);
 268     if (!SRP_user_pwd_set1_ids(ret, src->id, src->info)
 269         || !SRP_user_pwd_set0_sv(ret, BN_dup(src->s), BN_dup(src->v))) {
 270             SRP_user_pwd_free(ret);
 271             return NULL;
 272     }
 273     return ret;
 274 }
 275
 276 SRP_VBASE *SRP_VBASE_new(char *seed_key)
 277 {
 278     SRP_VBASE *vb = OPENSSL_malloc(sizeof(*vb));
 279
 280     if (vb == NULL)
 281         return NULL;
 282     if ((vb->users_pwd = sk_SRP_user_pwd_new_null()) == NULL
 283         || (vb->gN_cache = sk_SRP_gN_cache_new_null()) == NULL) {
 284         sk_SRP_user_pwd_free(vb->users_pwd);
 285         OPENSSL_free(vb);
 286         return NULL;
 287     }
 288     vb->default_g = NULL;
 289     vb->default_N = NULL;
 290     vb->seed_key = NULL;
 291     if ((seed_key != NULL) && (vb->seed_key = OPENSSL_strdup(seed_key)) == NULL) {
 292         sk_SRP_user_pwd_free(vb->users_pwd);
 293         sk_SRP_gN_cache_free(vb->gN_cache);
 294         OPENSSL_free(vb);
 295         return NULL;
 296     }
 297     return vb;
 298 }
 299
 300 void SRP_VBASE_free(SRP_VBASE *vb)
 301 {
 302     if (!vb)
 303         return;
 304     sk_SRP_user_pwd_pop_free(vb->users_pwd, SRP_user_pwd_free);
 305     sk_SRP_gN_cache_free(vb->gN_cache);
 306     OPENSSL_free(vb->seed_key);
 307     OPENSSL_free(vb);
 308 }
 309
 310 static SRP_gN_cache *SRP_gN_new_init(const char *ch)
 311 {
 312     unsigned char tmp[MAX_LEN];
 313     int len;
 314     SRP_gN_cache *newgN = OPENSSL_malloc(sizeof(*newgN));
 315
 316     if (newgN == NULL)
 317         return NULL;
 318
 319     len = t_fromb64(tmp, sizeof(tmp), ch);
 320     if (len < 0)
 321         goto err;
 322
 323     if ((newgN->b64_bn = OPENSSL_strdup(ch)) == NULL)
 324         goto err;
 325
 326     if ((newgN->bn = BN_bin2bn(tmp, len, NULL)))
 327         return newgN;
 328
 329     OPENSSL_free(newgN->b64_bn);
 330  err:
 331     OPENSSL_free(newgN);
 332     return NULL;
 333 }
 334
 335 static void SRP_gN_free(SRP_gN_cache *gN_cache)
 336 {
 337     if (gN_cache == NULL)
 338         return;
 339     OPENSSL_free(gN_cache->b64_bn);
 340     BN_free(gN_cache->bn);
 341     OPENSSL_free(gN_cache);
 342 }
 343
 344 static SRP_gN *SRP_get_gN_by_id(const char *id, STACK_OF(SRP_gN) *gN_tab)
 345 {
 346     int i;
 347
 348     SRP_gN *gN;
 349     if (gN_tab != NULL) {
 350         for (i = 0; i < sk_SRP_gN_num(gN_tab); i++) {
 351             gN = sk_SRP_gN_value(gN_tab, i);
 352             if (gN && (id == NULL || strcmp(gN->id, id) == 0))
 353                 return gN;
 354         }
 355     }
 356
 357     return SRP_get_default_gN(id);
 358 }
 359
 360 static BIGNUM *SRP_gN_place_bn(STACK_OF(SRP_gN_cache) *gN_cache, char *ch)
 361 {
 362     int i;
 363     if (gN_cache == NULL)
 364         return NULL;
 365
 366     /* search if we have already one... */
 367     for (i = 0; i < sk_SRP_gN_cache_num(gN_cache); i++) {
 368         SRP_gN_cache *cache = sk_SRP_gN_cache_value(gN_cache, i);
 369         if (strcmp(cache->b64_bn, ch) == 0)
 370             return cache->bn;
 371     }
 372     {                           /* it is the first time that we find it */
 373         SRP_gN_cache *newgN = SRP_gN_new_init(ch);
 374         if (newgN) {
 375             if (sk_SRP_gN_cache_insert(gN_cache, newgN, 0) > 0)
 376                 return newgN->bn;
 377             SRP_gN_free(newgN);
 378         }
 379     }
 380     return NULL;
 381 }
 382
 383 /*
 384  * This function parses the verifier file generated by the srp app.
 385  * The format for each entry is:
 386  * V base64(verifier) base64(salt) username gNid userinfo(optional)
 387  * or
 388  * I base64(N) base64(g)
 389  * Note that base64 is the SRP variant of base64 encoding described
 390  * in t_fromb64().
 391  */
 392
 393 int SRP_VBASE_init(SRP_VBASE *vb, char *verifier_file)
 394 {
 395     int error_code = SRP_ERR_MEMORY;
 396     STACK_OF(SRP_gN) *SRP_gN_tab = sk_SRP_gN_new_null();
 397     char *last_index = NULL;
 398     int i;
 399     char **pp;
 400
 401     SRP_gN *gN = NULL;
 402     SRP_user_pwd *user_pwd = NULL;
 403
 404     TXT_DB *tmpdb = NULL;
 405     BIO *in = BIO_new(BIO_s_file());
 406
 407     if (SRP_gN_tab == NULL)
 408         goto err;
 409
 410     error_code = SRP_ERR_OPEN_FILE;
 411
 412     if (in == NULL || BIO_read_filename(in, verifier_file) <= 0)
 413         goto err;
 414
 415     error_code = SRP_ERR_VBASE_INCOMPLETE_FILE;
 416
 417     if ((tmpdb = TXT_DB_read(in, DB_NUMBER)) == NULL)
 418         goto err;
 419
 420     error_code = SRP_ERR_MEMORY;
 421
 422     if (vb->seed_key) {
 423         last_index = SRP_get_default_gN(NULL)->id;
 424     }
 425     for (i = 0; i < sk_OPENSSL_PSTRING_num(tmpdb->data); i++) {
 426         pp = sk_OPENSSL_PSTRING_value(tmpdb->data, i);
 427         if (pp[DB_srptype][0] == DB_SRP_INDEX) {
 428             /*
 429              * we add this couple in the internal Stack
 430              */
 431
 432             if ((gN = OPENSSL_malloc(sizeof(*gN))) == NULL)
 433                 goto err;
 434
 435             if ((gN->id = OPENSSL_strdup(pp[DB_srpid])) == NULL
 436                 || (gN->N = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpverifier]))
 437                         == NULL
 438                 || (gN->g = SRP_gN_place_bn(vb->gN_cache, pp[DB_srpsalt]))
 439                         == NULL
 440                 || sk_SRP_gN_insert(SRP_gN_tab, gN, 0) == 0)
 441                 goto err;
 442
 443             gN = NULL;
 444
 445             if (vb->seed_key != NULL) {
 446                 last_index = pp[DB_srpid];
 447             }
 448         } else if (pp[DB_srptype][0] == DB_SRP_VALID) {
 449             /* it is a user .... */
 450             const SRP_gN *lgN;
 451
 452             if ((lgN = SRP_get_gN_by_id(pp[DB_srpgN], SRP_gN_tab)) != NULL) {
 453                 error_code = SRP_ERR_MEMORY;
 454                 if ((user_pwd = SRP_user_pwd_new()) == NULL)
 455                     goto err;
 456
 457                 SRP_user_pwd_set_gN(user_pwd, lgN->g, lgN->N);
 458                 if (!SRP_user_pwd_set1_ids
 459                     (user_pwd, pp[DB_srpid], pp[DB_srpinfo]))
 460                     goto err;
 461
 462                 error_code = SRP_ERR_VBASE_BN_LIB;
 463                 if (!SRP_user_pwd_set_sv
 464                     (user_pwd, pp[DB_srpsalt], pp[DB_srpverifier]))
 465                     goto err;
 466
 467                 if (sk_SRP_user_pwd_insert(vb->users_pwd, user_pwd, 0) == 0)
 468                     goto err;
 469                 user_pwd = NULL; /* abandon responsibility */
 470             }
 471         }
 472     }
 473
 474     if (last_index != NULL) {
 475         /* this means that we want to simulate a default user */
 476
 477         if (((gN = SRP_get_gN_by_id(last_index, SRP_gN_tab)) == NULL)) {
 478             error_code = SRP_ERR_VBASE_BN_LIB;
 479             goto err;
 480         }
 481         vb->default_g = gN->g;
 482         vb->default_N = gN->N;
 483         gN = NULL;
 484     }
 485     error_code = SRP_NO_ERROR;
 486
 487  err:
 488     /*
 489      * there may be still some leaks to fix, if this fails, the application
 490      * terminates most likely
 491      */
 492
 493     if (gN != NULL) {
 494         OPENSSL_free(gN->id);
 495         OPENSSL_free(gN);
 496     }
 497
 498     SRP_user_pwd_free(user_pwd);
 499
 500     TXT_DB_free(tmpdb);
 501     BIO_free_all(in);
 502
 503     sk_SRP_gN_free(SRP_gN_tab);
 504
 505     return error_code;
 506
 507 }
 508
 509 static SRP_user_pwd *find_user(SRP_VBASE *vb, char *username)
 510 {
 511     int i;
 512     SRP_user_pwd *user;
 513
 514     if (vb == NULL)
 515         return NULL;
 516
 517     for (i = 0; i < sk_SRP_user_pwd_num(vb->users_pwd); i++) {
 518         user = sk_SRP_user_pwd_value(vb->users_pwd, i);
 519         if (strcmp(user->id, username) == 0)
 520             return user;
 521     }
 522
 523     return NULL;
 524 }
 525
 526 int SRP_VBASE_add0_user(SRP_VBASE *vb, SRP_user_pwd *user_pwd)
 527 {
 528     if (sk_SRP_user_pwd_push(vb->users_pwd, user_pwd) <= 0)
 529         return 0;
 530     return 1;
 531 }
 532
 533 # ifndef OPENSSL_NO_DEPRECATED_1_1_0
 534 /*
 535  * DEPRECATED: use SRP_VBASE_get1_by_user instead.
 536  * This method ignores the configured seed and fails for an unknown user.
 537  * Ownership of the returned pointer is not released to the caller.
 538  * In other words, caller must not free the result.
 539  */
 540 SRP_user_pwd *SRP_VBASE_get_by_user(SRP_VBASE *vb, char *username)
 541 {
 542     return find_user(vb, username);
 543 }
 544 # endif
 545
 546 /*
 547  * Ownership of the returned pointer is released to the caller.
 548  * In other words, caller must free the result once done.
 549  */
 550 SRP_user_pwd *SRP_VBASE_get1_by_user(SRP_VBASE *vb, char *username)
 551 {
 552     SRP_user_pwd *user;
 553     unsigned char digv[SHA_DIGEST_LENGTH];
 554     unsigned char digs[SHA_DIGEST_LENGTH];
 555     EVP_MD_CTX *ctxt = NULL;
 556     EVP_MD *md = NULL;
 557
 558     if (vb == NULL)
 559         return NULL;
 560
 561     if ((user = find_user(vb, username)) != NULL)
 562         return srp_user_pwd_dup(user);
 563
 564     if ((vb->seed_key == NULL) ||
 565         (vb->default_g == NULL) || (vb->default_N == NULL))
 566         return NULL;
 567
 568 /* if the user is unknown we set parameters as well if we have a seed_key */
 569
 570     if ((user = SRP_user_pwd_new()) == NULL)
 571         return NULL;
 572
 573     SRP_user_pwd_set_gN(user, vb->default_g, vb->default_N);
 574
 575     if (!SRP_user_pwd_set1_ids(user, username, NULL))
 576         goto err;
 577
 578     if (RAND_priv_bytes(digv, SHA_DIGEST_LENGTH) <= 0)
 579         goto err;
 580     md = EVP_MD_fetch(NULL, SN_sha1, NULL);
 581     if (md == NULL)
 582         goto err;
 583     ctxt = EVP_MD_CTX_new();
 584     if (ctxt == NULL
 585         || !EVP_DigestInit_ex(ctxt, md, NULL)
 586         || !EVP_DigestUpdate(ctxt, vb->seed_key, strlen(vb->seed_key))
 587         || !EVP_DigestUpdate(ctxt, username, strlen(username))
 588         || !EVP_DigestFinal_ex(ctxt, digs, NULL))
 589         goto err;
 590     EVP_MD_CTX_free(ctxt);
 591     ctxt = NULL;
 592     EVP_MD_free(md);
 593     md = NULL;
 594     if (SRP_user_pwd_set0_sv(user,
 595                              BN_bin2bn(digs, SHA_DIGEST_LENGTH, NULL),
 596                              BN_bin2bn(digv, SHA_DIGEST_LENGTH, NULL)))
 597         return user;
 598
 599  err:
 600     EVP_MD_free(md);
 601     EVP_MD_CTX_free(ctxt);
 602     SRP_user_pwd_free(user);
 603     return NULL;
 604 }
 605
 606 /*
 607  * create a verifier (*salt,*verifier,g and N are in base64)
 608  */
 609 char *SRP_create_verifier_ex(const char *user, const char *pass, char **salt,
 610                              char **verifier, const char *N, const char *g,
 611                              OSSL_LIB_CTX *libctx, const char *propq)
 612 {
 613     int len;
 614     char *result = NULL, *vf = NULL;
 615     const BIGNUM *N_bn = NULL, *g_bn = NULL;
 616     BIGNUM *N_bn_alloc = NULL, *g_bn_alloc = NULL, *s = NULL, *v = NULL;
 617     unsigned char tmp[MAX_LEN];
 618     unsigned char tmp2[MAX_LEN];
 619     char *defgNid = NULL;
 620     int vfsize = 0;
 621
 622     if ((user == NULL) ||
 623         (pass == NULL) || (salt == NULL) || (verifier == NULL))
 624         goto err;
 625
 626     if (N) {
 627         if ((len = t_fromb64(tmp, sizeof(tmp), N)) <= 0)
 628             goto err;
 629         N_bn_alloc = BN_bin2bn(tmp, len, NULL);
 630         if (N_bn_alloc == NULL)
 631             goto err;
 632         N_bn = N_bn_alloc;
 633         if ((len = t_fromb64(tmp, sizeof(tmp), g)) <= 0)
 634             goto err;
 635         g_bn_alloc = BN_bin2bn(tmp, len, NULL);
 636         if (g_bn_alloc == NULL)
 637             goto err;
 638         g_bn = g_bn_alloc;
 639         defgNid = "*";
 640     } else {
 641         SRP_gN *gN = SRP_get_default_gN(g);
 642         if (gN == NULL)
 643             goto err;
 644         N_bn = gN->N;
 645         g_bn = gN->g;
 646         defgNid = gN->id;
 647     }
 648
 649     if (*salt == NULL) {
 650         if (RAND_bytes_ex(libctx, tmp2, SRP_RANDOM_SALT_LEN, 0) <= 0)
 651             goto err;
 652
 653         s = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);
 654     } else {
 655         if ((len = t_fromb64(tmp2, sizeof(tmp2), *salt)) <= 0)
 656             goto err;
 657         s = BN_bin2bn(tmp2, len, NULL);
 658     }
 659     if (s == NULL)
 660         goto err;
 661
 662     if (!SRP_create_verifier_BN_ex(user, pass, &s, &v, N_bn, g_bn, libctx,
 663                                    propq))
 664         goto err;
 665
 666     if (BN_bn2bin(v, tmp) < 0)
 667         goto err;
 668     vfsize = BN_num_bytes(v) * 2;
 669     if (((vf = OPENSSL_malloc(vfsize)) == NULL))
 670         goto err;
 671     if (!t_tob64(vf, tmp, BN_num_bytes(v)))
 672         goto err;
 673
 674     if (*salt == NULL) {
 675         char *tmp_salt;
 676
 677         if ((tmp_salt = OPENSSL_malloc(SRP_RANDOM_SALT_LEN * 2)) == NULL) {
 678             goto err;
 679         }
 680         if (!t_tob64(tmp_salt, tmp2, SRP_RANDOM_SALT_LEN)) {
 681             OPENSSL_free(tmp_salt);
 682             goto err;
 683         }
 684         *salt = tmp_salt;
 685     }
 686
 687     *verifier = vf;
 688     vf = NULL;
 689     result = defgNid;
 690
 691  err:
 692     BN_free(N_bn_alloc);
 693     BN_free(g_bn_alloc);
 694     OPENSSL_clear_free(vf, vfsize);
 695     BN_clear_free(s);
 696     BN_clear_free(v);
 697     return result;
 698 }
 699
 700 char *SRP_create_verifier(const char *user, const char *pass, char **salt,
 701                           char **verifier, const char *N, const char *g)
 702 {
 703     return SRP_create_verifier_ex(user, pass, salt, verifier, N, g, NULL, NULL);
 704 }
 705
 706 /*
 707  * create a verifier (*salt,*verifier,g and N are BIGNUMs). If *salt != NULL
 708  * then the provided salt will be used. On successful exit *verifier will point
 709  * to a newly allocated BIGNUM containing the verifier and (if a salt was not
 710  * provided) *salt will be populated with a newly allocated BIGNUM containing a
 711  * random salt.
 712  * The caller is responsible for freeing the allocated *salt and *verifier
 713  * BIGNUMS.
 714  */
 715 int SRP_create_verifier_BN_ex(const char *user, const char *pass, BIGNUM **salt,
 716                               BIGNUM **verifier, const BIGNUM *N,
 717                               const BIGNUM *g, OSSL_LIB_CTX *libctx,
 718                               const char *propq)
 719 {
 720     int result = 0;
 721     BIGNUM *x = NULL;
 722     BN_CTX *bn_ctx = BN_CTX_new_ex(libctx);
 723     unsigned char tmp2[MAX_LEN];
 724     BIGNUM *salttmp = NULL, *verif;
 725
 726     if ((user == NULL) ||
 727         (pass == NULL) ||
 728         (salt == NULL) ||
 729         (verifier == NULL) || (N == NULL) || (g == NULL) || (bn_ctx == NULL))
 730         goto err;
 731
 732     if (*salt == NULL) {
 733         if (RAND_bytes_ex(libctx, tmp2, SRP_RANDOM_SALT_LEN, 0) <= 0)
 734             goto err;
 735
 736         salttmp = BN_bin2bn(tmp2, SRP_RANDOM_SALT_LEN, NULL);
 737         if (salttmp == NULL)
 738             goto err;
 739     } else {
 740         salttmp = *salt;
 741     }
 742
 743     x = SRP_Calc_x_ex(salttmp, user, pass, libctx, propq);
 744     if (x == NULL)
 745         goto err;
 746
 747     verif = BN_new();
 748     if (verif == NULL)
 749         goto err;
 750
 751     if (!BN_mod_exp(verif, g, x, N, bn_ctx)) {
 752         BN_clear_free(verif);
 753         goto err;
 754     }
 755
 756     result = 1;
 757     *salt = salttmp;
 758     *verifier = verif;
 759
 760  err:
 761     if (salt != NULL && *salt != salttmp)
 762         BN_clear_free(salttmp);
 763     BN_clear_free(x);
 764     BN_CTX_free(bn_ctx);
 765     return result;
 766 }
 767
 768 int SRP_create_verifier_BN(const char *user, const char *pass, BIGNUM **salt,
 769                            BIGNUM **verifier, const BIGNUM *N,
 770                            const BIGNUM *g)
 771 {
 772     return SRP_create_verifier_BN_ex(user, pass, salt, verifier, N, g, NULL,
 773                                      NULL);
 774 }
 775 #endif