crypto/engine/eng_dyn.c

   1 /*
   2  * Written by Geoff Thorpe (geoff@geoffthorpe.net) for the OpenSSL project
   3  * 2001.
   4  */
   5 /* ====================================================================
   6  * Copyright (c) 1999-2001 The OpenSSL Project.  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  *
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in
  17  *    the documentation and/or other materials provided with the
  18  *    distribution.
  19  *
  20  * 3. All advertising materials mentioning features or use of this
  21  *    software must display the following acknowledgment:
  22  *    "This product includes software developed by the OpenSSL Project
  23  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  24  *
  25  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  26  *    endorse or promote products derived from this software without
  27  *    prior written permission. For written permission, please contact
  28  *    licensing@OpenSSL.org.
  29  *
  30  * 5. Products derived from this software may not be called "OpenSSL"
  31  *    nor may "OpenSSL" appear in their names without prior written
  32  *    permission of the OpenSSL Project.
  33  *
  34  * 6. Redistributions of any form whatsoever must retain the following
  35  *    acknowledgment:
  36  *    "This product includes software developed by the OpenSSL Project
  37  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  38  *
  39  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  40  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  41  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  42  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  43  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  44  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  45  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  46  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  48  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  49  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  50  * OF THE POSSIBILITY OF SUCH DAMAGE.
  51  * ====================================================================
  52  *
  53  * This product includes cryptographic software written by Eric Young
  54  * (eay@cryptsoft.com).  This product includes software written by Tim
  55  * Hudson (tjh@cryptsoft.com).
  56  *
  57  */
  58
  59 #include "eng_int.h"
  60 #include "internal/dso.h"
  61 #include <openssl/crypto.h>
  62
  63 /*
  64  * Shared libraries implementing ENGINEs for use by the "dynamic" ENGINE
  65  * loader should implement the hook-up functions with the following
  66  * prototypes.
  67  */
  68
  69 /* Our ENGINE handlers */
  70 static int dynamic_init(ENGINE *e);
  71 static int dynamic_finish(ENGINE *e);
  72 static int dynamic_ctrl(ENGINE *e, int cmd, long i, void *p,
  73                         void (*f) (void));
  74 /* Predeclare our context type */
  75 typedef struct st_dynamic_data_ctx dynamic_data_ctx;
  76 /* The implementation for the important control command */
  77 static int dynamic_load(ENGINE *e, dynamic_data_ctx *ctx);
  78
  79 #define DYNAMIC_CMD_SO_PATH             ENGINE_CMD_BASE
  80 #define DYNAMIC_CMD_NO_VCHECK           (ENGINE_CMD_BASE + 1)
  81 #define DYNAMIC_CMD_ID                  (ENGINE_CMD_BASE + 2)
  82 #define DYNAMIC_CMD_LIST_ADD            (ENGINE_CMD_BASE + 3)
  83 #define DYNAMIC_CMD_DIR_LOAD            (ENGINE_CMD_BASE + 4)
  84 #define DYNAMIC_CMD_DIR_ADD             (ENGINE_CMD_BASE + 5)
  85 #define DYNAMIC_CMD_LOAD                (ENGINE_CMD_BASE + 6)
  86
  87 /* The constants used when creating the ENGINE */
  88 static const char *engine_dynamic_id = "dynamic";
  89 static const char *engine_dynamic_name = "Dynamic engine loading support";
  90 static const ENGINE_CMD_DEFN dynamic_cmd_defns[] = {
  91     {DYNAMIC_CMD_SO_PATH,
  92      "SO_PATH",
  93      "Specifies the path to the new ENGINE shared library",
  94      ENGINE_CMD_FLAG_STRING},
  95     {DYNAMIC_CMD_NO_VCHECK,
  96      "NO_VCHECK",
  97      "Specifies to continue even if version checking fails (boolean)",
  98      ENGINE_CMD_FLAG_NUMERIC},
  99     {DYNAMIC_CMD_ID,
 100      "ID",
 101      "Specifies an ENGINE id name for loading",
 102      ENGINE_CMD_FLAG_STRING},
 103     {DYNAMIC_CMD_LIST_ADD,
 104      "LIST_ADD",
 105      "Whether to add a loaded ENGINE to the internal list (0=no,1=yes,2=mandatory)",
 106      ENGINE_CMD_FLAG_NUMERIC},
 107     {DYNAMIC_CMD_DIR_LOAD,
 108      "DIR_LOAD",
 109      "Specifies whether to load from 'DIR_ADD' directories (0=no,1=yes,2=mandatory)",
 110      ENGINE_CMD_FLAG_NUMERIC},
 111     {DYNAMIC_CMD_DIR_ADD,
 112      "DIR_ADD",
 113      "Adds a directory from which ENGINEs can be loaded",
 114      ENGINE_CMD_FLAG_STRING},
 115     {DYNAMIC_CMD_LOAD,
 116      "LOAD",
 117      "Load up the ENGINE specified by other settings",
 118      ENGINE_CMD_FLAG_NO_INPUT},
 119     {0, NULL, NULL, 0}
 120 };
 121
 122 /*
 123  * Loading code stores state inside the ENGINE structure via the "ex_data"
 124  * element. We load all our state into a single structure and use that as a
 125  * single context in the "ex_data" stack.
 126  */
 127 struct st_dynamic_data_ctx {
 128     /* The DSO object we load that supplies the ENGINE code */
 129     DSO *dynamic_dso;
 130     /*
 131      * The function pointer to the version checking shared library function
 132      */
 133     dynamic_v_check_fn v_check;
 134     /*
 135      * The function pointer to the engine-binding shared library function
 136      */
 137     dynamic_bind_engine bind_engine;
 138     /* The default name/path for loading the shared library */
 139     char *DYNAMIC_LIBNAME;
 140     /* Whether to continue loading on a version check failure */
 141     int no_vcheck;
 142     /* If non-NULL, stipulates the 'id' of the ENGINE to be loaded */
 143     char *engine_id;
 144     /*
 145      * If non-zero, a successfully loaded ENGINE should be added to the
 146      * internal ENGINE list. If 2, the add must succeed or the entire load
 147      * should fail.
 148      */
 149     int list_add_value;
 150     /* The symbol name for the version checking function */
 151     const char *DYNAMIC_F1;
 152     /* The symbol name for the "initialise ENGINE structure" function */
 153     const char *DYNAMIC_F2;
 154     /*
 155      * Whether to never use 'dirs', use 'dirs' as a fallback, or only use
 156      * 'dirs' for loading. Default is to use 'dirs' as a fallback.
 157      */
 158     int dir_load;
 159     /* A stack of directories from which ENGINEs could be loaded */
 160     STACK_OF(OPENSSL_STRING) *dirs;
 161 };
 162
 163 /*
 164  * This is the "ex_data" index we obtain and reserve for use with our context
 165  * structure.
 166  */
 167 static int dynamic_ex_data_idx = -1;
 168
 169 static void int_free_str(char *s)
 170 {
 171     OPENSSL_free(s);
 172 }
 173
 174 /*
 175  * Because our ex_data element may or may not get allocated depending on
 176  * whether a "first-use" occurs before the ENGINE is freed, we have a memory
 177  * leak problem to solve. We can't declare a "new" handler for the ex_data as
 178  * we don't want a dynamic_data_ctx in *all* ENGINE structures of all types
 179  * (this is a bug in the design of CRYPTO_EX_DATA). As such, we just declare
 180  * a "free" handler and that will get called if an ENGINE is being destroyed
 181  * and there was an ex_data element corresponding to our context type.
 182  */
 183 static void dynamic_data_ctx_free_func(void *parent, void *ptr,
 184                                        CRYPTO_EX_DATA *ad, int idx, long argl,
 185                                        void *argp)
 186 {
 187     if (ptr) {
 188         dynamic_data_ctx *ctx = (dynamic_data_ctx *)ptr;
 189         DSO_free(ctx->dynamic_dso);
 190         OPENSSL_free(ctx->DYNAMIC_LIBNAME);
 191         OPENSSL_free(ctx->engine_id);
 192         sk_OPENSSL_STRING_pop_free(ctx->dirs, int_free_str);
 193         OPENSSL_free(ctx);
 194     }
 195 }
 196
 197 /*
 198  * Construct the per-ENGINE context. We create it blindly and then use a lock
 199  * to check for a race - if so, all but one of the threads "racing" will have
 200  * wasted their time. The alternative involves creating everything inside the
 201  * lock which is far worse.
 202  */
 203 static int dynamic_set_data_ctx(ENGINE *e, dynamic_data_ctx **ctx)
 204 {
 205     dynamic_data_ctx *c = OPENSSL_zalloc(sizeof(*c));
 206
 207     if (c == NULL) {
 208         ENGINEerr(ENGINE_F_DYNAMIC_SET_DATA_CTX, ERR_R_MALLOC_FAILURE);
 209         return 0;
 210     }
 211     c->dirs = sk_OPENSSL_STRING_new_null();
 212     if (c->dirs == NULL) {
 213         ENGINEerr(ENGINE_F_DYNAMIC_SET_DATA_CTX, ERR_R_MALLOC_FAILURE);
 214         OPENSSL_free(c);
 215         return 0;
 216     }
 217     c->DYNAMIC_F1 = "v_check";
 218     c->DYNAMIC_F2 = "bind_engine";
 219     c->dir_load = 1;
 220     CRYPTO_THREAD_write_lock(global_engine_lock);
 221     if ((*ctx = (dynamic_data_ctx *)ENGINE_get_ex_data(e,
 222                                                        dynamic_ex_data_idx))
 223         == NULL) {
 224         /* Good, we're the first */
 225         ENGINE_set_ex_data(e, dynamic_ex_data_idx, c);
 226         *ctx = c;
 227         c = NULL;
 228     }
 229     CRYPTO_THREAD_unlock(global_engine_lock);
 230     /*
 231      * If we lost the race to set the context, c is non-NULL and *ctx is the
 232      * context of the thread that won.
 233      */
 234     if (c)
 235         sk_OPENSSL_STRING_free(c->dirs);
 236     OPENSSL_free(c);
 237     return 1;
 238 }
 239
 240 /*
 241  * This function retrieves the context structure from an ENGINE's "ex_data",
 242  * or if it doesn't exist yet, sets it up.
 243  */
 244 static dynamic_data_ctx *dynamic_get_data_ctx(ENGINE *e)
 245 {
 246     dynamic_data_ctx *ctx;
 247     if (dynamic_ex_data_idx < 0) {
 248         /*
 249          * Create and register the ENGINE ex_data, and associate our "free"
 250          * function with it to ensure any allocated contexts get freed when
 251          * an ENGINE goes underground.
 252          */
 253         int new_idx = ENGINE_get_ex_new_index(0, NULL, NULL, NULL,
 254                                               dynamic_data_ctx_free_func);
 255         if (new_idx == -1) {
 256             ENGINEerr(ENGINE_F_DYNAMIC_GET_DATA_CTX, ENGINE_R_NO_INDEX);
 257             return NULL;
 258         }
 259         CRYPTO_THREAD_write_lock(global_engine_lock);
 260         /* Avoid a race by checking again inside this lock */
 261         if (dynamic_ex_data_idx < 0) {
 262             /* Good, someone didn't beat us to it */
 263             dynamic_ex_data_idx = new_idx;
 264             new_idx = -1;
 265         }
 266         CRYPTO_THREAD_unlock(global_engine_lock);
 267         /*
 268          * In theory we could "give back" the index here if (new_idx>-1), but
 269          * it's not possible and wouldn't gain us much if it were.
 270          */
 271     }
 272     ctx = (dynamic_data_ctx *)ENGINE_get_ex_data(e, dynamic_ex_data_idx);
 273     /* Check if the context needs to be created */
 274     if ((ctx == NULL) && !dynamic_set_data_ctx(e, &ctx))
 275         /* "set_data" will set errors if necessary */
 276         return NULL;
 277     return ctx;
 278 }
 279
 280 static ENGINE *engine_dynamic(void)
 281 {
 282     ENGINE *ret = ENGINE_new();
 283     if (ret == NULL)
 284         return NULL;
 285     if (!ENGINE_set_id(ret, engine_dynamic_id) ||
 286         !ENGINE_set_name(ret, engine_dynamic_name) ||
 287         !ENGINE_set_init_function(ret, dynamic_init) ||
 288         !ENGINE_set_finish_function(ret, dynamic_finish) ||
 289         !ENGINE_set_ctrl_function(ret, dynamic_ctrl) ||
 290         !ENGINE_set_flags(ret, ENGINE_FLAGS_BY_ID_COPY) ||
 291         !ENGINE_set_cmd_defns(ret, dynamic_cmd_defns)) {
 292         ENGINE_free(ret);
 293         return NULL;
 294     }
 295     return ret;
 296 }
 297
 298 void int_engine_load_dynamic(void)
 299 {
 300     ENGINE *toadd = engine_dynamic();
 301     if (!toadd)
 302         return;
 303     ENGINE_add(toadd);
 304     /*
 305      * If the "add" worked, it gets a structural reference. So either way, we
 306      * release our just-created reference.
 307      */
 308     ENGINE_free(toadd);
 309     /*
 310      * If the "add" didn't work, it was probably a conflict because it was
 311      * already added (eg. someone calling ENGINE_load_blah then calling
 312      * ENGINE_load_builtin_engines() perhaps).
 313      */
 314     ERR_clear_error();
 315 }
 316
 317 static int dynamic_init(ENGINE *e)
 318 {
 319     /*
 320      * We always return failure - the "dynamic" engine itself can't be used
 321      * for anything.
 322      */
 323     return 0;
 324 }
 325
 326 static int dynamic_finish(ENGINE *e)
 327 {
 328     /*
 329      * This should never be called on account of "dynamic_init" always
 330      * failing.
 331      */
 332     return 0;
 333 }
 334
 335 static int dynamic_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f) (void))
 336 {
 337     dynamic_data_ctx *ctx = dynamic_get_data_ctx(e);
 338     int initialised;
 339
 340     if (!ctx) {
 341         ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ENGINE_R_NOT_LOADED);
 342         return 0;
 343     }
 344     initialised = ((ctx->dynamic_dso == NULL) ? 0 : 1);
 345     /* All our control commands require the ENGINE to be uninitialised */
 346     if (initialised) {
 347         ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ENGINE_R_ALREADY_LOADED);
 348         return 0;
 349     }
 350     switch (cmd) {
 351     case DYNAMIC_CMD_SO_PATH:
 352         /* a NULL 'p' or a string of zero-length is the same thing */
 353         if (p && (strlen((const char *)p) < 1))
 354             p = NULL;
 355         OPENSSL_free(ctx->DYNAMIC_LIBNAME);
 356         if (p)
 357             ctx->DYNAMIC_LIBNAME = OPENSSL_strdup(p);
 358         else
 359             ctx->DYNAMIC_LIBNAME = NULL;
 360         return (ctx->DYNAMIC_LIBNAME ? 1 : 0);
 361     case DYNAMIC_CMD_NO_VCHECK:
 362         ctx->no_vcheck = ((i == 0) ? 0 : 1);
 363         return 1;
 364     case DYNAMIC_CMD_ID:
 365         /* a NULL 'p' or a string of zero-length is the same thing */
 366         if (p && (strlen((const char *)p) < 1))
 367             p = NULL;
 368         OPENSSL_free(ctx->engine_id);
 369         if (p)
 370             ctx->engine_id = OPENSSL_strdup(p);
 371         else
 372             ctx->engine_id = NULL;
 373         return (ctx->engine_id ? 1 : 0);
 374     case DYNAMIC_CMD_LIST_ADD:
 375         if ((i < 0) || (i > 2)) {
 376             ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ENGINE_R_INVALID_ARGUMENT);
 377             return 0;
 378         }
 379         ctx->list_add_value = (int)i;
 380         return 1;
 381     case DYNAMIC_CMD_LOAD:
 382         return dynamic_load(e, ctx);
 383     case DYNAMIC_CMD_DIR_LOAD:
 384         if ((i < 0) || (i > 2)) {
 385             ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ENGINE_R_INVALID_ARGUMENT);
 386             return 0;
 387         }
 388         ctx->dir_load = (int)i;
 389         return 1;
 390     case DYNAMIC_CMD_DIR_ADD:
 391         /* a NULL 'p' or a string of zero-length is the same thing */
 392         if (!p || (strlen((const char *)p) < 1)) {
 393             ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ENGINE_R_INVALID_ARGUMENT);
 394             return 0;
 395         }
 396         {
 397             char *tmp_str = OPENSSL_strdup(p);
 398             if (!tmp_str) {
 399                 ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ERR_R_MALLOC_FAILURE);
 400                 return 0;
 401             }
 402             sk_OPENSSL_STRING_insert(ctx->dirs, tmp_str, -1);
 403         }
 404         return 1;
 405     default:
 406         break;
 407     }
 408     ENGINEerr(ENGINE_F_DYNAMIC_CTRL, ENGINE_R_CTRL_COMMAND_NOT_IMPLEMENTED);
 409     return 0;
 410 }
 411
 412 static int int_load(dynamic_data_ctx *ctx)
 413 {
 414     int num, loop;
 415     /* Unless told not to, try a direct load */
 416     if ((ctx->dir_load != 2) && (DSO_load(ctx->dynamic_dso,
 417                                           ctx->DYNAMIC_LIBNAME, NULL,
 418                                           0)) != NULL)
 419         return 1;
 420     /* If we're not allowed to use 'dirs' or we have none, fail */
 421     if (!ctx->dir_load || (num = sk_OPENSSL_STRING_num(ctx->dirs)) < 1)
 422         return 0;
 423     for (loop = 0; loop < num; loop++) {
 424         const char *s = sk_OPENSSL_STRING_value(ctx->dirs, loop);
 425         char *merge = DSO_merge(ctx->dynamic_dso, ctx->DYNAMIC_LIBNAME, s);
 426         if (!merge)
 427             return 0;
 428         if (DSO_load(ctx->dynamic_dso, merge, NULL, 0)) {
 429             /* Found what we're looking for */
 430             OPENSSL_free(merge);
 431             return 1;
 432         }
 433         OPENSSL_free(merge);
 434     }
 435     return 0;
 436 }
 437
 438 static int dynamic_load(ENGINE *e, dynamic_data_ctx *ctx)
 439 {
 440     ENGINE cpy;
 441     dynamic_fns fns;
 442
 443     if (ctx->dynamic_dso == NULL)
 444         ctx->dynamic_dso = DSO_new();
 445     if (ctx->dynamic_dso == NULL)
 446         return 0;
 447     if (!ctx->DYNAMIC_LIBNAME) {
 448         if (!ctx->engine_id)
 449             return 0;
 450         DSO_ctrl(ctx->dynamic_dso, DSO_CTRL_SET_FLAGS,
 451                  DSO_FLAG_NAME_TRANSLATION_EXT_ONLY, NULL);
 452         ctx->DYNAMIC_LIBNAME =
 453             DSO_convert_filename(ctx->dynamic_dso, ctx->engine_id);
 454     }
 455     if (!int_load(ctx)) {
 456         ENGINEerr(ENGINE_F_DYNAMIC_LOAD, ENGINE_R_DSO_NOT_FOUND);
 457         DSO_free(ctx->dynamic_dso);
 458         ctx->dynamic_dso = NULL;
 459         return 0;
 460     }
 461     /* We have to find a bind function otherwise it'll always end badly */
 462     if (!
 463         (ctx->bind_engine =
 464          (dynamic_bind_engine) DSO_bind_func(ctx->dynamic_dso,
 465                                              ctx->DYNAMIC_F2))) {
 466         ctx->bind_engine = NULL;
 467         DSO_free(ctx->dynamic_dso);
 468         ctx->dynamic_dso = NULL;
 469         ENGINEerr(ENGINE_F_DYNAMIC_LOAD, ENGINE_R_DSO_FAILURE);
 470         return 0;
 471     }
 472     /* Do we perform version checking? */
 473     if (!ctx->no_vcheck) {
 474         unsigned long vcheck_res = 0;
 475         /*
 476          * Now we try to find a version checking function and decide how to
 477          * cope with failure if/when it fails.
 478          */
 479         ctx->v_check =
 480             (dynamic_v_check_fn) DSO_bind_func(ctx->dynamic_dso,
 481                                                ctx->DYNAMIC_F1);
 482         if (ctx->v_check)
 483             vcheck_res = ctx->v_check(OSSL_DYNAMIC_VERSION);
 484         /*
 485          * We fail if the version checker veto'd the load *or* if it is
 486          * deferring to us (by returning its version) and we think it is too
 487          * old.
 488          */
 489         if (vcheck_res < OSSL_DYNAMIC_OLDEST) {
 490             /* Fail */
 491             ctx->bind_engine = NULL;
 492             ctx->v_check = NULL;
 493             DSO_free(ctx->dynamic_dso);
 494             ctx->dynamic_dso = NULL;
 495             ENGINEerr(ENGINE_F_DYNAMIC_LOAD,
 496                       ENGINE_R_VERSION_INCOMPATIBILITY);
 497             return 0;
 498         }
 499     }
 500     /*
 501      * First binary copy the ENGINE structure so that we can roll back if the
 502      * hand-over fails
 503      */
 504     memcpy(&cpy, e, sizeof(ENGINE));
 505     /*
 506      * Provide the ERR, "ex_data", memory, and locking callbacks so the
 507      * loaded library uses our state rather than its own. FIXME: As noted in
 508      * engine.h, much of this would be simplified if each area of code
 509      * provided its own "summary" structure of all related callbacks. It
 510      * would also increase opaqueness.
 511      */
 512     fns.static_state = ENGINE_get_static_state();
 513     CRYPTO_get_mem_functions(&fns.mem_fns.malloc_fn, &fns.mem_fns.realloc_fn,
 514                              &fns.mem_fns.free_fn);
 515     /*
 516      * Now that we've loaded the dynamic engine, make sure no "dynamic"
 517      * ENGINE elements will show through.
 518      */
 519     engine_set_all_null(e);
 520
 521     /* Try to bind the ENGINE onto our own ENGINE structure */
 522     if (!ctx->bind_engine(e, ctx->engine_id, &fns)) {
 523         ctx->bind_engine = NULL;
 524         ctx->v_check = NULL;
 525         DSO_free(ctx->dynamic_dso);
 526         ctx->dynamic_dso = NULL;
 527         ENGINEerr(ENGINE_F_DYNAMIC_LOAD, ENGINE_R_INIT_FAILED);
 528         /* Copy the original ENGINE structure back */
 529         memcpy(e, &cpy, sizeof(ENGINE));
 530         return 0;
 531     }
 532     /* Do we try to add this ENGINE to the internal list too? */
 533     if (ctx->list_add_value > 0) {
 534         if (!ENGINE_add(e)) {
 535             /* Do we tolerate this or fail? */
 536             if (ctx->list_add_value > 1) {
 537                 /*
 538                  * Fail - NB: By this time, it's too late to rollback, and
 539                  * trying to do so allows the bind_engine() code to have
 540                  * created leaks. We just have to fail where we are, after
 541                  * the ENGINE has changed.
 542                  */
 543                 ENGINEerr(ENGINE_F_DYNAMIC_LOAD,
 544                           ENGINE_R_CONFLICTING_ENGINE_ID);
 545                 return 0;
 546             }
 547             /* Tolerate */
 548             ERR_clear_error();
 549         }
 550     }
 551     return 1;
 552 }