/* $OpenBSD: ex_data.c,v 1.20 2018/03/17 16:20:01 beck Exp $ */

/*

 * Overhaul notes;

 *

 * This code is now *mostly* thread-safe. It is now easier to understand in what

 * ways it is safe and in what ways it is not, which is an improvement. Firstly,

 * all per-class stacks and index-counters for ex_data are stored in the same

 * global LHASH table (keyed by class). This hash table uses locking for all

 * access with the exception of CRYPTO_cleanup_all_ex_data(), which must only be

 * called when no other threads can possibly race against it (even if it was

 * locked, the race would mean it's possible the hash table might have been

 * recreated after the cleanup). As classes can only be added to the hash table,

 * and within each class, the stack of methods can only be incremented, the

 * locking mechanics are simpler than they would otherwise be. For example, the

 * new/dup/free ex_data functions will lock the hash table, copy the method

 * pointers it needs from the relevant class, then unlock the hash table before

 * actually applying those method pointers to the task of the new/dup/free

 * operations. As they can't be removed from the method-stack, only

 * supplemented, there's no race conditions associated with using them outside

 * the lock. The get/set_ex_data functions are not locked because they do not

 * involve this global state at all - they operate directly with a previously

 * obtained per-class method index and a particular "ex_data" variable. These

 * variables are usually instantiated per-context (eg. each RSA structure has

 * one) so locking on read/write access to that variable can be locked locally

 * if required (eg. using the "RSA" lock to synchronise access to a

 * per-RSA-structure ex_data variable if required).

 * [Geoff]

 */

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 *

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 *

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *    "This product includes cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 *

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

/* ====================================================================

 * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in

 *    the documentation and/or other materials provided with the

 *    distribution.

 *

 * 3. All advertising materials mentioning features or use of this

 *    software must display the following acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@openssl.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR

 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 * ====================================================================

 *

 * This product includes cryptographic software written by Eric Young

 * (eay@cryptsoft.com).  This product includes software written by Tim

 * Hudson (tjh@cryptsoft.com).

 *

 */

#include <openssl/err.h>

#include <openssl/lhash.h>

/* What an "implementation of ex_data functionality" looks like */

struct st_CRYPTO_EX_DATA_IMPL {

  /*********************/

  /* GLOBAL OPERATIONS */

  /* Return a new class index */

  int (*cb_new_class)(void);

  /* Cleanup all state used by the implementation */

  void (*cb_cleanup)(void);

  /************************/

  /* PER-CLASS OPERATIONS */

  /* Get a new method index within a class */

  int (*cb_get_new_index)(int class_index, long argl, void *argp,

      CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func,

      CRYPTO_EX_free *free_func);

  /* Initialise a new CRYPTO_EX_DATA of a given class */

  int (*cb_new_ex_data)(int class_index, void *obj,

      CRYPTO_EX_DATA *ad);

  /* Duplicate a CRYPTO_EX_DATA of a given class onto a copy */

  int (*cb_dup_ex_data)(int class_index, CRYPTO_EX_DATA *to,

      CRYPTO_EX_DATA *from);

  /* Cleanup a CRYPTO_EX_DATA of a given class */

  void (*cb_free_ex_data)(int class_index, void *obj,

      CRYPTO_EX_DATA *ad);

};

/* The implementation we use at run-time */

static const CRYPTO_EX_DATA_IMPL *impl = NULL;

/* To call "impl" functions, use this macro rather than referring to 'impl' directly, eg.

 * EX_IMPL(get_new_index)(...);

*/

#define EX_IMPL(a) impl->cb_##a

/* Predeclare the "default" ex_data implementation */

static int int_new_class(void);

static void int_cleanup(void);

static int int_get_new_index(int class_index, long argl, void *argp,

    CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func,

    CRYPTO_EX_free *free_func);

static int int_new_ex_data(int class_index, void *obj,

    CRYPTO_EX_DATA *ad);

static int int_dup_ex_data(int class_index, CRYPTO_EX_DATA *to,

    CRYPTO_EX_DATA *from);

static void int_free_ex_data(int class_index, void *obj,

    CRYPTO_EX_DATA *ad);

static CRYPTO_EX_DATA_IMPL impl_default = {

  int_new_class,

  int_cleanup,

  int_get_new_index,

  int_new_ex_data,

  int_dup_ex_data,

  int_free_ex_data

};

/* Internal function that checks whether "impl" is set and if not, sets it to

 * the default. */

static void

impl_check(void)

{

  CRYPTO_w_lock(CRYPTO_LOCK_EX_DATA);

  if (!impl)

    impl = &impl_default;

  CRYPTO_w_unlock(CRYPTO_LOCK_EX_DATA);

}

/* A macro wrapper for impl_check that first uses a non-locked test before

 * invoking the function (which checks again inside a lock). */

#define IMPL_CHECK if(!impl) impl_check();

/* API functions to get/set the "ex_data" implementation */

const CRYPTO_EX_DATA_IMPL *

CRYPTO_get_ex_data_implementation(void)

{

  IMPL_CHECK

  return impl;

}

int

CRYPTO_set_ex_data_implementation(const CRYPTO_EX_DATA_IMPL *i)

{

  int toret = 0;

  CRYPTO_w_lock(CRYPTO_LOCK_EX_DATA);

  if (!impl) {

    impl = i;

    toret = 1;

  }

  CRYPTO_w_unlock(CRYPTO_LOCK_EX_DATA);

  return toret;

}

/****************************************************************************/

/* Interal (default) implementation of "ex_data" support. API functions are

 * further down. */

/* The type that represents what each "class" used to implement locally. A STACK

 * of CRYPTO_EX_DATA_FUNCS plus a index-counter. The 'class_index' is the global

 * value representing the class that is used to distinguish these items. */

typedef struct st_ex_class_item {

  int class_index;

  STACK_OF(CRYPTO_EX_DATA_FUNCS) *meth;

  int meth_num;

} EX_CLASS_ITEM;

/* When assigning new class indexes, this is our counter */

static int ex_class = CRYPTO_EX_INDEX_USER;

/* The global hash table of EX_CLASS_ITEM items */

DECLARE_LHASH_OF(EX_CLASS_ITEM);

static LHASH_OF(EX_CLASS_ITEM) *ex_data = NULL;

/* The callbacks required in the "ex_data" hash table */

static unsigned long

ex_class_item_hash(const EX_CLASS_ITEM *a)

{

  return a->class_index;

}

static IMPLEMENT_LHASH_HASH_FN(ex_class_item, EX_CLASS_ITEM)

static int

ex_class_item_cmp(const EX_CLASS_ITEM *a, const EX_CLASS_ITEM *b)

{

  return a->class_index - b->class_index;

}

static IMPLEMENT_LHASH_COMP_FN(ex_class_item, EX_CLASS_ITEM)

/* Internal functions used by the "impl_default" implementation to access the

 * state */

static int

ex_data_check(void)

{

  int toret = 1;

  CRYPTO_w_lock(CRYPTO_LOCK_EX_DATA);

  if (!ex_data &&

      (ex_data = lh_EX_CLASS_ITEM_new()) == NULL)

    toret = 0;

  CRYPTO_w_unlock(CRYPTO_LOCK_EX_DATA);

  return toret;

}

/* This macros helps reduce the locking from repeated checks because the

 * ex_data_check() function checks ex_data again inside a lock. */

#define EX_DATA_CHECK(iffail) if(!ex_data && !ex_data_check()) {iffail}

/* This "inner" callback is used by the callback function that follows it */

static void

def_cleanup_util_cb(CRYPTO_EX_DATA_FUNCS *funcs)

{

  free(funcs);

}

/* This callback is used in lh_doall to destroy all EX_CLASS_ITEM values from

 * "ex_data" prior to the ex_data hash table being itself destroyed. Doesn't do

 * any locking. */

static void

def_cleanup_cb(void *a_void)

{

  EX_CLASS_ITEM *item = (EX_CLASS_ITEM *)a_void;

  sk_CRYPTO_EX_DATA_FUNCS_pop_free(item->meth, def_cleanup_util_cb);

  free(item);

}

/* Return the EX_CLASS_ITEM from the "ex_data" hash table that corresponds to a

 * given class. Handles locking. */

static EX_CLASS_ITEM *

def_get_class(int class_index)

{

  EX_CLASS_ITEM d, *p, *gen;

  EX_DATA_CHECK(return NULL;)

  d.class_index = class_index;

  if (!OPENSSL_init_crypto(0, NULL))

    return NULL;

  CRYPTO_w_lock(CRYPTO_LOCK_EX_DATA);

  p = lh_EX_CLASS_ITEM_retrieve(ex_data, &d);

  if (!p) {

    gen = malloc(sizeof(EX_CLASS_ITEM));

    if (gen) {

      gen->class_index = class_index;

      gen->meth_num = 0;

      gen->meth = sk_CRYPTO_EX_DATA_FUNCS_new_null();

      if (!gen->meth)

        free(gen);

      else {

        /* Because we're inside the ex_data lock, the

         * return value from the insert will be NULL */

        (void)lh_EX_CLASS_ITEM_insert(ex_data, gen);

        p = gen;

      }

    }

  }

  CRYPTO_w_unlock(CRYPTO_LOCK_EX_DATA);

  if (!p)

    CRYPTOerror(ERR_R_MALLOC_FAILURE);

  return p;

}

/* Add a new method to the given EX_CLASS_ITEM and return the corresponding

 * index (or -1 for error). Handles locking. */

static int

def_add_index(EX_CLASS_ITEM *item, long argl, void *argp,

    CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func)

{

  int toret = -1;

  CRYPTO_EX_DATA_FUNCS *a = malloc(sizeof(CRYPTO_EX_DATA_FUNCS));

  if (!a) {

    CRYPTOerror(ERR_R_MALLOC_FAILURE);

    return -1;

  }

  a->argl = argl;

  a->argp = argp;

  a->new_func = new_func;

  a->dup_func = dup_func;

  a->free_func = free_func;

  CRYPTO_w_lock(CRYPTO_LOCK_EX_DATA);

  while (sk_CRYPTO_EX_DATA_FUNCS_num(item->meth) <= item->meth_num) {

    if (!sk_CRYPTO_EX_DATA_FUNCS_push(item->meth, NULL)) {

      CRYPTOerror(ERR_R_MALLOC_FAILURE);

      free(a);

      goto err;

    }

  }

  toret = item->meth_num++;

  (void)sk_CRYPTO_EX_DATA_FUNCS_set(item->meth, toret, a);

err:

  CRYPTO_w_unlock(CRYPTO_LOCK_EX_DATA);

  return toret;

}

/**************************************************************/

/* The functions in the default CRYPTO_EX_DATA_IMPL structure */

static int

int_new_class(void)

{

  int toret;

  CRYPTO_w_lock(CRYPTO_LOCK_EX_DATA);

  toret = ex_class++;

  CRYPTO_w_unlock(CRYPTO_LOCK_EX_DATA);

  return toret;

}

static void

int_cleanup(void)

{

  EX_DATA_CHECK(return;)

  lh_EX_CLASS_ITEM_doall(ex_data, def_cleanup_cb);

  lh_EX_CLASS_ITEM_free(ex_data);

  ex_data = NULL;

  impl = NULL;

}

static int

int_get_new_index(int class_index, long argl, void *argp,

    CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func,

    CRYPTO_EX_free *free_func)

{

  EX_CLASS_ITEM *item = def_get_class(class_index);

  if (!item)

    return -1;

  return def_add_index(item, argl, argp, new_func, dup_func, free_func);

}

/* Thread-safe by copying a class's array of "CRYPTO_EX_DATA_FUNCS" entries in

 * the lock, then using them outside the lock. NB: Thread-safety only applies to

 * the global "ex_data" state (ie. class definitions), not thread-safe on 'ad'

 * itself. */

static int

int_new_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad)

{

  int mx, i;

  void *ptr;

  CRYPTO_EX_DATA_FUNCS **storage = NULL;

  EX_CLASS_ITEM *item = def_get_class(class_index);

  if (!item)

    /* error is already set */

    return 0;

  ad->sk = NULL;

  CRYPTO_r_lock(CRYPTO_LOCK_EX_DATA);

  mx = sk_CRYPTO_EX_DATA_FUNCS_num(item->meth);

  if (mx > 0) {

    storage = reallocarray(NULL, mx, sizeof(CRYPTO_EX_DATA_FUNCS*));

    if (!storage)

      goto skip;

    for (i = 0; i < mx; i++)

      storage[i] = sk_CRYPTO_EX_DATA_FUNCS_value(

          item->meth, i);

  }

skip:

  CRYPTO_r_unlock(CRYPTO_LOCK_EX_DATA);

  if ((mx > 0) && !storage) {

    CRYPTOerror(ERR_R_MALLOC_FAILURE);

    return 0;

  }

  for (i = 0; i < mx; i++) {

    if (storage[i] && storage[i]->new_func) {

      ptr = CRYPTO_get_ex_data(ad, i);

      storage[i]->new_func(obj, ptr, ad, i,

          storage[i]->argl, storage[i]->argp);

    }

  }

  free(storage);

  return 1;

}

/* Same thread-safety notes as for "int_new_ex_data" */

static int

int_dup_ex_data(int class_index, CRYPTO_EX_DATA *to, CRYPTO_EX_DATA *from)

{

  int mx, j, i;

  char *ptr;

  CRYPTO_EX_DATA_FUNCS **storage = NULL;

  EX_CLASS_ITEM *item;

  if (!from->sk)

    /* 'to' should be "blank" which *is* just like 'from' */

    return 1;

  if ((item = def_get_class(class_index)) == NULL)

    return 0;

  CRYPTO_r_lock(CRYPTO_LOCK_EX_DATA);

  mx = sk_CRYPTO_EX_DATA_FUNCS_num(item->meth);

  j = sk_void_num(from->sk);

  if (j < mx)

    mx = j;

  if (mx > 0) {

    storage = reallocarray(NULL, mx, sizeof(CRYPTO_EX_DATA_FUNCS*));

    if (!storage)

      goto skip;

    for (i = 0; i < mx; i++)

      storage[i] = sk_CRYPTO_EX_DATA_FUNCS_value(

          item->meth, i);

  }

skip:

  CRYPTO_r_unlock(CRYPTO_LOCK_EX_DATA);

  if ((mx > 0) && !storage) {

    CRYPTOerror(ERR_R_MALLOC_FAILURE);

    return 0;

  }

  for (i = 0; i < mx; i++) {

    ptr = CRYPTO_get_ex_data(from, i);

    if (storage[i] && storage[i]->dup_func)

      storage[i]->dup_func(to, from, &ptr, i,

          storage[i]->argl, storage[i]->argp);

    CRYPTO_set_ex_data(to, i, ptr);

  }

  free(storage);

  return 1;

}

/* Same thread-safety notes as for "int_new_ex_data" */

static void

int_free_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad)

{

  int mx, i;

  EX_CLASS_ITEM *item;

  void *ptr;

  CRYPTO_EX_DATA_FUNCS **storage = NULL;

  if ((item = def_get_class(class_index)) == NULL)

    return;

  CRYPTO_r_lock(CRYPTO_LOCK_EX_DATA);

  mx = sk_CRYPTO_EX_DATA_FUNCS_num(item->meth);

  if (mx > 0) {

    storage = reallocarray(NULL, mx, sizeof(CRYPTO_EX_DATA_FUNCS*));

    if (!storage)

      goto skip;

    for (i = 0; i < mx; i++)

      storage[i] = sk_CRYPTO_EX_DATA_FUNCS_value(

          item->meth, i);

  }

skip:

  CRYPTO_r_unlock(CRYPTO_LOCK_EX_DATA);

  if ((mx > 0) && !storage) {

    CRYPTOerror(ERR_R_MALLOC_FAILURE);

    return;

  }

  for (i = 0; i < mx; i++) {

    if (storage[i] && storage[i]->free_func) {

      ptr = CRYPTO_get_ex_data(ad, i);

      storage[i]->free_func(obj, ptr, ad, i,

          storage[i]->argl, storage[i]->argp);

    }

  }

  free(storage);

  if (ad->sk) {

    sk_void_free(ad->sk);

    ad->sk = NULL;

  }

}

/********************************************************************/

/* API functions that defer all "state" operations to the "ex_data"

 * implementation we have set. */

/* Obtain an index for a new class (not the same as getting a new index within

 * an existing class - this is actually getting a new *class*) */

int

CRYPTO_ex_data_new_class(void)

{

  IMPL_CHECK

  return EX_IMPL(new_class)();

}

/* Release all "ex_data" state to prevent memory leaks. This can't be made

 * thread-safe without overhauling a lot of stuff, and shouldn't really be

 * called under potential race-conditions anyway (it's for program shutdown

 * after all). */

void

CRYPTO_cleanup_all_ex_data(void)

{

  IMPL_CHECK

  EX_IMPL(cleanup)();

}

/* Inside an existing class, get/register a new index. */

int

CRYPTO_get_ex_new_index(int class_index, long argl, void *argp,

    CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func)

{

  int ret = -1;

  IMPL_CHECK

  ret = EX_IMPL(get_new_index)(class_index,

      argl, argp, new_func, dup_func, free_func);

  return ret;

}

/* Initialise a new CRYPTO_EX_DATA for use in a particular class - including

 * calling new() callbacks for each index in the class used by this variable */

int

CRYPTO_new_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad)

{

  IMPL_CHECK

  return EX_IMPL(new_ex_data)(class_index, obj, ad);

}

/* Duplicate a CRYPTO_EX_DATA variable - including calling dup() callbacks for

 * each index in the class used by this variable */

int

CRYPTO_dup_ex_data(int class_index, CRYPTO_EX_DATA *to, CRYPTO_EX_DATA *from)

{

  IMPL_CHECK

  return EX_IMPL(dup_ex_data)(class_index, to, from);

}

/* Cleanup a CRYPTO_EX_DATA variable - including calling free() callbacks for

 * each index in the class used by this variable */

void

CRYPTO_free_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad)

{

  IMPL_CHECK

  EX_IMPL(free_ex_data)(class_index, obj, ad);

}

/* For a given CRYPTO_EX_DATA variable, set the value corresponding to a

 * particular index in the class used by this variable */

int

CRYPTO_set_ex_data(CRYPTO_EX_DATA *ad, int idx, void *val)

{

  int i;

  if (ad->sk == NULL) {

    if ((ad->sk = sk_void_new_null()) == NULL) {

      CRYPTOerror(ERR_R_MALLOC_FAILURE);

      return (0);

    }

  }

  i = sk_void_num(ad->sk);

  while (i <= idx) {

    if (!sk_void_push(ad->sk, NULL)) {

      CRYPTOerror(ERR_R_MALLOC_FAILURE);

      return (0);

    }

    i++;

  }

  sk_void_set(ad->sk, idx, val);

  return (1);

}

/* For a given CRYPTO_EX_DATA_ variable, get the value corresponding to a

 * particular index in the class used by this variable */

void *

CRYPTO_get_ex_data(const CRYPTO_EX_DATA *ad, int idx)

{

  if (ad->sk == NULL)

    return (0);

  else if (idx >= sk_void_num(ad->sk))

    return (0);

  else

    return (sk_void_value(ad->sk, idx));

}