release/src/router/openssl/ssl/tls_srp.c

   1 /* ssl/tls_srp.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) 2004-2011 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 #include "ssl_locl.h"
  61 #ifndef OPENSSL_NO_SRP
  62
  63 # include <openssl/rand.h>
  64 # include <openssl/srp.h>
  65 # include <openssl/err.h>
  66
  67 int SSL_CTX_SRP_CTX_free(struct ssl_ctx_st *ctx)
  68 {
  69     if (ctx == NULL)
  70         return 0;
  71     OPENSSL_free(ctx->srp_ctx.login);
  72     BN_free(ctx->srp_ctx.N);
  73     BN_free(ctx->srp_ctx.g);
  74     BN_free(ctx->srp_ctx.s);
  75     BN_free(ctx->srp_ctx.B);
  76     BN_free(ctx->srp_ctx.A);
  77     BN_free(ctx->srp_ctx.a);
  78     BN_free(ctx->srp_ctx.b);
  79     BN_free(ctx->srp_ctx.v);
  80     ctx->srp_ctx.TLS_ext_srp_username_callback = NULL;
  81     ctx->srp_ctx.SRP_cb_arg = NULL;
  82     ctx->srp_ctx.SRP_verify_param_callback = NULL;
  83     ctx->srp_ctx.SRP_give_srp_client_pwd_callback = NULL;
  84     ctx->srp_ctx.N = NULL;
  85     ctx->srp_ctx.g = NULL;
  86     ctx->srp_ctx.s = NULL;
  87     ctx->srp_ctx.B = NULL;
  88     ctx->srp_ctx.A = NULL;
  89     ctx->srp_ctx.a = NULL;
  90     ctx->srp_ctx.b = NULL;
  91     ctx->srp_ctx.v = NULL;
  92     ctx->srp_ctx.login = NULL;
  93     ctx->srp_ctx.info = NULL;
  94     ctx->srp_ctx.strength = SRP_MINIMAL_N;
  95     ctx->srp_ctx.srp_Mask = 0;
  96     return (1);
  97 }
  98
  99 int SSL_SRP_CTX_free(struct ssl_st *s)
 100 {
 101     if (s == NULL)
 102         return 0;
 103     OPENSSL_free(s->srp_ctx.login);
 104     BN_free(s->srp_ctx.N);
 105     BN_free(s->srp_ctx.g);
 106     BN_free(s->srp_ctx.s);
 107     BN_free(s->srp_ctx.B);
 108     BN_free(s->srp_ctx.A);
 109     BN_free(s->srp_ctx.a);
 110     BN_free(s->srp_ctx.b);
 111     BN_free(s->srp_ctx.v);
 112     s->srp_ctx.TLS_ext_srp_username_callback = NULL;
 113     s->srp_ctx.SRP_cb_arg = NULL;
 114     s->srp_ctx.SRP_verify_param_callback = NULL;
 115     s->srp_ctx.SRP_give_srp_client_pwd_callback = NULL;
 116     s->srp_ctx.N = NULL;
 117     s->srp_ctx.g = NULL;
 118     s->srp_ctx.s = NULL;
 119     s->srp_ctx.B = NULL;
 120     s->srp_ctx.A = NULL;
 121     s->srp_ctx.a = NULL;
 122     s->srp_ctx.b = NULL;
 123     s->srp_ctx.v = NULL;
 124     s->srp_ctx.login = NULL;
 125     s->srp_ctx.info = NULL;
 126     s->srp_ctx.strength = SRP_MINIMAL_N;
 127     s->srp_ctx.srp_Mask = 0;
 128     return (1);
 129 }
 130
 131 int SSL_SRP_CTX_init(struct ssl_st *s)
 132 {
 133     SSL_CTX *ctx;
 134
 135     if ((s == NULL) || ((ctx = s->ctx) == NULL))
 136         return 0;
 137     s->srp_ctx.SRP_cb_arg = ctx->srp_ctx.SRP_cb_arg;
 138     /* set client Hello login callback */
 139     s->srp_ctx.TLS_ext_srp_username_callback =
 140         ctx->srp_ctx.TLS_ext_srp_username_callback;
 141     /* set SRP N/g param callback for verification */
 142     s->srp_ctx.SRP_verify_param_callback =
 143         ctx->srp_ctx.SRP_verify_param_callback;
 144     /* set SRP client passwd callback */
 145     s->srp_ctx.SRP_give_srp_client_pwd_callback =
 146         ctx->srp_ctx.SRP_give_srp_client_pwd_callback;
 147
 148     s->srp_ctx.N = NULL;
 149     s->srp_ctx.g = NULL;
 150     s->srp_ctx.s = NULL;
 151     s->srp_ctx.B = NULL;
 152     s->srp_ctx.A = NULL;
 153     s->srp_ctx.a = NULL;
 154     s->srp_ctx.b = NULL;
 155     s->srp_ctx.v = NULL;
 156     s->srp_ctx.login = NULL;
 157     s->srp_ctx.info = ctx->srp_ctx.info;
 158     s->srp_ctx.strength = ctx->srp_ctx.strength;
 159
 160     if (((ctx->srp_ctx.N != NULL) &&
 161          ((s->srp_ctx.N = BN_dup(ctx->srp_ctx.N)) == NULL)) ||
 162         ((ctx->srp_ctx.g != NULL) &&
 163          ((s->srp_ctx.g = BN_dup(ctx->srp_ctx.g)) == NULL)) ||
 164         ((ctx->srp_ctx.s != NULL) &&
 165          ((s->srp_ctx.s = BN_dup(ctx->srp_ctx.s)) == NULL)) ||
 166         ((ctx->srp_ctx.B != NULL) &&
 167          ((s->srp_ctx.B = BN_dup(ctx->srp_ctx.B)) == NULL)) ||
 168         ((ctx->srp_ctx.A != NULL) &&
 169          ((s->srp_ctx.A = BN_dup(ctx->srp_ctx.A)) == NULL)) ||
 170         ((ctx->srp_ctx.a != NULL) &&
 171          ((s->srp_ctx.a = BN_dup(ctx->srp_ctx.a)) == NULL)) ||
 172         ((ctx->srp_ctx.v != NULL) &&
 173          ((s->srp_ctx.v = BN_dup(ctx->srp_ctx.v)) == NULL)) ||
 174         ((ctx->srp_ctx.b != NULL) &&
 175          ((s->srp_ctx.b = BN_dup(ctx->srp_ctx.b)) == NULL))) {
 176         SSLerr(SSL_F_SSL_SRP_CTX_INIT, ERR_R_BN_LIB);
 177         goto err;
 178     }
 179     if ((ctx->srp_ctx.login != NULL) &&
 180         ((s->srp_ctx.login = BUF_strdup(ctx->srp_ctx.login)) == NULL)) {
 181         SSLerr(SSL_F_SSL_SRP_CTX_INIT, ERR_R_INTERNAL_ERROR);
 182         goto err;
 183     }
 184     s->srp_ctx.srp_Mask = ctx->srp_ctx.srp_Mask;
 185
 186     return (1);
 187  err:
 188     OPENSSL_free(s->srp_ctx.login);
 189     BN_free(s->srp_ctx.N);
 190     BN_free(s->srp_ctx.g);
 191     BN_free(s->srp_ctx.s);
 192     BN_free(s->srp_ctx.B);
 193     BN_free(s->srp_ctx.A);
 194     BN_free(s->srp_ctx.a);
 195     BN_free(s->srp_ctx.b);
 196     BN_free(s->srp_ctx.v);
 197     return (0);
 198 }
 199
 200 int SSL_CTX_SRP_CTX_init(struct ssl_ctx_st *ctx)
 201 {
 202     if (ctx == NULL)
 203         return 0;
 204
 205     ctx->srp_ctx.SRP_cb_arg = NULL;
 206     /* set client Hello login callback */
 207     ctx->srp_ctx.TLS_ext_srp_username_callback = NULL;
 208     /* set SRP N/g param callback for verification */
 209     ctx->srp_ctx.SRP_verify_param_callback = NULL;
 210     /* set SRP client passwd callback */
 211     ctx->srp_ctx.SRP_give_srp_client_pwd_callback = NULL;
 212
 213     ctx->srp_ctx.N = NULL;
 214     ctx->srp_ctx.g = NULL;
 215     ctx->srp_ctx.s = NULL;
 216     ctx->srp_ctx.B = NULL;
 217     ctx->srp_ctx.A = NULL;
 218     ctx->srp_ctx.a = NULL;
 219     ctx->srp_ctx.b = NULL;
 220     ctx->srp_ctx.v = NULL;
 221     ctx->srp_ctx.login = NULL;
 222     ctx->srp_ctx.srp_Mask = 0;
 223     ctx->srp_ctx.info = NULL;
 224     ctx->srp_ctx.strength = SRP_MINIMAL_N;
 225
 226     return (1);
 227 }
 228
 229 /* server side */
 230 int SSL_srp_server_param_with_username(SSL *s, int *ad)
 231 {
 232     unsigned char b[SSL_MAX_MASTER_KEY_LENGTH];
 233     int al;
 234
 235     *ad = SSL_AD_UNKNOWN_PSK_IDENTITY;
 236     if ((s->srp_ctx.TLS_ext_srp_username_callback != NULL) &&
 237         ((al =
 238           s->srp_ctx.TLS_ext_srp_username_callback(s, ad,
 239                                                    s->srp_ctx.SRP_cb_arg)) !=
 240          SSL_ERROR_NONE))
 241         return al;
 242
 243     *ad = SSL_AD_INTERNAL_ERROR;
 244     if ((s->srp_ctx.N == NULL) ||
 245         (s->srp_ctx.g == NULL) ||
 246         (s->srp_ctx.s == NULL) || (s->srp_ctx.v == NULL))
 247         return SSL3_AL_FATAL;
 248
 249     if (RAND_bytes(b, sizeof(b)) <= 0)
 250         return SSL3_AL_FATAL;
 251     s->srp_ctx.b = BN_bin2bn(b, sizeof(b), NULL);
 252     OPENSSL_cleanse(b, sizeof(b));
 253
 254     /* Calculate:  B = (kv + g^b) % N  */
 255
 256     return ((s->srp_ctx.B =
 257              SRP_Calc_B(s->srp_ctx.b, s->srp_ctx.N, s->srp_ctx.g,
 258                         s->srp_ctx.v)) !=
 259             NULL) ? SSL_ERROR_NONE : SSL3_AL_FATAL;
 260 }
 261
 262 /*
 263  * If the server just has the raw password, make up a verifier entry on the
 264  * fly
 265  */
 266 int SSL_set_srp_server_param_pw(SSL *s, const char *user, const char *pass,
 267                                 const char *grp)
 268 {
 269     SRP_gN *GN = SRP_get_default_gN(grp);
 270     if (GN == NULL)
 271         return -1;
 272     s->srp_ctx.N = BN_dup(GN->N);
 273     s->srp_ctx.g = BN_dup(GN->g);
 274     if (s->srp_ctx.v != NULL) {
 275         BN_clear_free(s->srp_ctx.v);
 276         s->srp_ctx.v = NULL;
 277     }
 278     if (s->srp_ctx.s != NULL) {
 279         BN_clear_free(s->srp_ctx.s);
 280         s->srp_ctx.s = NULL;
 281     }
 282     if (!SRP_create_verifier_BN
 283         (user, pass, &s->srp_ctx.s, &s->srp_ctx.v, GN->N, GN->g))
 284         return -1;
 285
 286     return 1;
 287 }
 288
 289 int SSL_set_srp_server_param(SSL *s, const BIGNUM *N, const BIGNUM *g,
 290                              BIGNUM *sa, BIGNUM *v, char *info)
 291 {
 292     if (N != NULL) {
 293         if (s->srp_ctx.N != NULL) {
 294             if (!BN_copy(s->srp_ctx.N, N)) {
 295                 BN_free(s->srp_ctx.N);
 296                 s->srp_ctx.N = NULL;
 297             }
 298         } else
 299             s->srp_ctx.N = BN_dup(N);
 300     }
 301     if (g != NULL) {
 302         if (s->srp_ctx.g != NULL) {
 303             if (!BN_copy(s->srp_ctx.g, g)) {
 304                 BN_free(s->srp_ctx.g);
 305                 s->srp_ctx.g = NULL;
 306             }
 307         } else
 308             s->srp_ctx.g = BN_dup(g);
 309     }
 310     if (sa != NULL) {
 311         if (s->srp_ctx.s != NULL) {
 312             if (!BN_copy(s->srp_ctx.s, sa)) {
 313                 BN_free(s->srp_ctx.s);
 314                 s->srp_ctx.s = NULL;
 315             }
 316         } else
 317             s->srp_ctx.s = BN_dup(sa);
 318     }
 319     if (v != NULL) {
 320         if (s->srp_ctx.v != NULL) {
 321             if (!BN_copy(s->srp_ctx.v, v)) {
 322                 BN_free(s->srp_ctx.v);
 323                 s->srp_ctx.v = NULL;
 324             }
 325         } else
 326             s->srp_ctx.v = BN_dup(v);
 327     }
 328     s->srp_ctx.info = info;
 329
 330     if (!(s->srp_ctx.N) ||
 331         !(s->srp_ctx.g) || !(s->srp_ctx.s) || !(s->srp_ctx.v))
 332         return -1;
 333
 334     return 1;
 335 }
 336
 337 int SRP_generate_server_master_secret(SSL *s, unsigned char *master_key)
 338 {
 339     BIGNUM *K = NULL, *u = NULL;
 340     int ret = -1, tmp_len;
 341     unsigned char *tmp = NULL;
 342
 343     if (!SRP_Verify_A_mod_N(s->srp_ctx.A, s->srp_ctx.N))
 344         goto err;
 345     if (!(u = SRP_Calc_u(s->srp_ctx.A, s->srp_ctx.B, s->srp_ctx.N)))
 346         goto err;
 347     if (!
 348         (K =
 349          SRP_Calc_server_key(s->srp_ctx.A, s->srp_ctx.v, u, s->srp_ctx.b,
 350                              s->srp_ctx.N)))
 351         goto err;
 352
 353     tmp_len = BN_num_bytes(K);
 354     if ((tmp = OPENSSL_malloc(tmp_len)) == NULL)
 355         goto err;
 356     BN_bn2bin(K, tmp);
 357     ret =
 358         s->method->ssl3_enc->generate_master_secret(s, master_key, tmp,
 359                                                     tmp_len);
 360  err:
 361     if (tmp) {
 362         OPENSSL_cleanse(tmp, tmp_len);
 363         OPENSSL_free(tmp);
 364     }
 365     BN_clear_free(K);
 366     BN_clear_free(u);
 367     return ret;
 368 }
 369
 370 /* client side */
 371 int SRP_generate_client_master_secret(SSL *s, unsigned char *master_key)
 372 {
 373     BIGNUM *x = NULL, *u = NULL, *K = NULL;
 374     int ret = -1, tmp_len;
 375     char *passwd = NULL;
 376     unsigned char *tmp = NULL;
 377
 378     /*
 379      * Checks if b % n == 0
 380      */
 381     if (SRP_Verify_B_mod_N(s->srp_ctx.B, s->srp_ctx.N) == 0)
 382         goto err;
 383     if (!(u = SRP_Calc_u(s->srp_ctx.A, s->srp_ctx.B, s->srp_ctx.N)))
 384         goto err;
 385     if (s->srp_ctx.SRP_give_srp_client_pwd_callback == NULL)
 386         goto err;
 387     if (!
 388         (passwd =
 389          s->srp_ctx.SRP_give_srp_client_pwd_callback(s,
 390                                                      s->srp_ctx.SRP_cb_arg)))
 391         goto err;
 392     if (!(x = SRP_Calc_x(s->srp_ctx.s, s->srp_ctx.login, passwd)))
 393         goto err;
 394     if (!
 395         (K =
 396          SRP_Calc_client_key(s->srp_ctx.N, s->srp_ctx.B, s->srp_ctx.g, x,
 397                              s->srp_ctx.a, u)))
 398         goto err;
 399
 400     tmp_len = BN_num_bytes(K);
 401     if ((tmp = OPENSSL_malloc(tmp_len)) == NULL)
 402         goto err;
 403     BN_bn2bin(K, tmp);
 404     ret =
 405         s->method->ssl3_enc->generate_master_secret(s, master_key, tmp,
 406                                                     tmp_len);
 407  err:
 408     if (tmp) {
 409         OPENSSL_cleanse(tmp, tmp_len);
 410         OPENSSL_free(tmp);
 411     }
 412     BN_clear_free(K);
 413     BN_clear_free(x);
 414     if (passwd) {
 415         OPENSSL_cleanse(passwd, strlen(passwd));
 416         OPENSSL_free(passwd);
 417     }
 418     BN_clear_free(u);
 419     return ret;
 420 }
 421
 422 int srp_verify_server_param(SSL *s, int *al)
 423 {
 424     SRP_CTX *srp = &s->srp_ctx;
 425     /*
 426      * Sanity check parameters: we can quickly check B % N == 0 by checking B
 427      * != 0 since B < N
 428      */
 429     if (BN_ucmp(srp->g, srp->N) >= 0 || BN_ucmp(srp->B, srp->N) >= 0
 430         || BN_is_zero(srp->B)) {
 431         *al = SSL3_AD_ILLEGAL_PARAMETER;
 432         return 0;
 433     }
 434
 435     if (BN_num_bits(srp->N) < srp->strength) {
 436         *al = TLS1_AD_INSUFFICIENT_SECURITY;
 437         return 0;
 438     }
 439
 440     if (srp->SRP_verify_param_callback) {
 441         if (srp->SRP_verify_param_callback(s, srp->SRP_cb_arg) <= 0) {
 442             *al = TLS1_AD_INSUFFICIENT_SECURITY;
 443             return 0;
 444         }
 445     } else if (!SRP_check_known_gN_param(srp->g, srp->N)) {
 446         *al = TLS1_AD_INSUFFICIENT_SECURITY;
 447         return 0;
 448     }
 449
 450     return 1;
 451 }
 452
 453 int SRP_Calc_A_param(SSL *s)
 454 {
 455     unsigned char rnd[SSL_MAX_MASTER_KEY_LENGTH];
 456
 457     RAND_bytes(rnd, sizeof(rnd));
 458     s->srp_ctx.a = BN_bin2bn(rnd, sizeof(rnd), s->srp_ctx.a);
 459     OPENSSL_cleanse(rnd, sizeof(rnd));
 460
 461     if (!
 462         (s->srp_ctx.A = SRP_Calc_A(s->srp_ctx.a, s->srp_ctx.N, s->srp_ctx.g)))
 463         return -1;
 464
 465     return 1;
 466 }
 467
 468 BIGNUM *SSL_get_srp_g(SSL *s)
 469 {
 470     if (s->srp_ctx.g != NULL)
 471         return s->srp_ctx.g;
 472     return s->ctx->srp_ctx.g;
 473 }
 474
 475 BIGNUM *SSL_get_srp_N(SSL *s)
 476 {
 477     if (s->srp_ctx.N != NULL)
 478         return s->srp_ctx.N;
 479     return s->ctx->srp_ctx.N;
 480 }
 481
 482 char *SSL_get_srp_username(SSL *s)
 483 {
 484     if (s->srp_ctx.login != NULL)
 485         return s->srp_ctx.login;
 486     return s->ctx->srp_ctx.login;
 487 }
 488
 489 char *SSL_get_srp_userinfo(SSL *s)
 490 {
 491     if (s->srp_ctx.info != NULL)
 492         return s->srp_ctx.info;
 493     return s->ctx->srp_ctx.info;
 494 }
 495
 496 # define tls1_ctx_ctrl ssl3_ctx_ctrl
 497 # define tls1_ctx_callback_ctrl ssl3_ctx_callback_ctrl
 498
 499 int SSL_CTX_set_srp_username(SSL_CTX *ctx, char *name)
 500 {
 501     return tls1_ctx_ctrl(ctx, SSL_CTRL_SET_TLS_EXT_SRP_USERNAME, 0, name);
 502 }
 503
 504 int SSL_CTX_set_srp_password(SSL_CTX *ctx, char *password)
 505 {
 506     return tls1_ctx_ctrl(ctx, SSL_CTRL_SET_TLS_EXT_SRP_PASSWORD, 0, password);
 507 }
 508
 509 int SSL_CTX_set_srp_strength(SSL_CTX *ctx, int strength)
 510 {
 511     return tls1_ctx_ctrl(ctx, SSL_CTRL_SET_TLS_EXT_SRP_STRENGTH, strength,
 512                          NULL);
 513 }
 514
 515 int SSL_CTX_set_srp_verify_param_callback(SSL_CTX *ctx,
 516                                           int (*cb) (SSL *, void *))
 517 {
 518     return tls1_ctx_callback_ctrl(ctx, SSL_CTRL_SET_SRP_VERIFY_PARAM_CB,
 519                                   (void (*)(void))cb);
 520 }
 521
 522 int SSL_CTX_set_srp_cb_arg(SSL_CTX *ctx, void *arg)
 523 {
 524     return tls1_ctx_ctrl(ctx, SSL_CTRL_SET_SRP_ARG, 0, arg);
 525 }
 526
 527 int SSL_CTX_set_srp_username_callback(SSL_CTX *ctx,
 528                                       int (*cb) (SSL *, int *, void *))
 529 {
 530     return tls1_ctx_callback_ctrl(ctx, SSL_CTRL_SET_TLS_EXT_SRP_USERNAME_CB,
 531                                   (void (*)(void))cb);
 532 }
 533
 534 int SSL_CTX_set_srp_client_pwd_callback(SSL_CTX *ctx,
 535                                         char *(*cb) (SSL *, void *))
 536 {
 537     return tls1_ctx_callback_ctrl(ctx, SSL_CTRL_SET_SRP_GIVE_CLIENT_PWD_CB,
 538                                   (void (*)(void))cb);
 539 }
 540
 541 #endif