Fix data race in RAND_DRBG_generate
[openssl.git] / crypto / rand / rand_lib.c
index 6bea092..440c19c 100644 (file)
-/* crypto/rand/rand_lib.c */
-/* 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 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
  */
 
 #include <stdio.h>
-#include <sys/types.h>
 #include <time.h>
-#include "rand.h"
+#include "internal/cryptlib.h"
+#include <openssl/opensslconf.h>
+#include "internal/rand_int.h"
+#include <openssl/engine.h>
+#include "internal/thread_once.h"
+#include "rand_lcl.h"
+#include "e_os.h"
+
+#ifndef OPENSSL_NO_ENGINE
+/* non-NULL if default_RAND_meth is ENGINE-provided */
+static ENGINE *funct_ref;
+static CRYPTO_RWLOCK *rand_engine_lock;
+#endif
+static CRYPTO_RWLOCK *rand_meth_lock;
+static const RAND_METHOD *default_RAND_meth;
+static CRYPTO_ONCE rand_init = CRYPTO_ONCE_STATIC_INIT;
+
+int rand_fork_count;
+
+static CRYPTO_RWLOCK *rand_nonce_lock;
+static int rand_nonce_count;
+
+static int rand_cleaning_up = 0;
+
+#ifdef OPENSSL_RAND_SEED_RDTSC
+/*
+ * IMPORTANT NOTE:  It is not currently possible to use this code
+ * because we are not sure about the amount of randomness it provides.
+ * Some SP900 tests have been run, but there is internal skepticism.
+ * So for now this code is not used.
+ */
+# error "RDTSC enabled?  Should not be possible!"
+
+/*
+ * Acquire entropy from high-speed clock
+ *
+ * Since we get some randomness from the low-order bits of the
+ * high-speed clock, it can help.
+ *
+ * Returns the total entropy count, if it exceeds the requested
+ * entropy count. Otherwise, returns an entropy count of 0.
+ */
+size_t rand_acquire_entropy_from_tsc(RAND_POOL *pool)
+{
+    unsigned char c;
+    int i;
+
+    if ((OPENSSL_ia32cap_P[0] & (1 << 4)) != 0) {
+        for (i = 0; i < TSC_READ_COUNT; i++) {
+            c = (unsigned char)(OPENSSL_rdtsc() & 0xFF);
+            rand_pool_add(pool, &c, 1, 4);
+        }
+    }
+    return rand_pool_entropy_available(pool);
+}
+#endif
+
+#ifdef OPENSSL_RAND_SEED_RDCPU
+size_t OPENSSL_ia32_rdseed_bytes(unsigned char *buf, size_t len);
+size_t OPENSSL_ia32_rdrand_bytes(unsigned char *buf, size_t len);
+
+extern unsigned int OPENSSL_ia32cap_P[];
+
+/*
+ * Acquire entropy using Intel-specific cpu instructions
+ *
+ * Uses the RDSEED instruction if available, otherwise uses
+ * RDRAND if available.
+ *
+ * For the differences between RDSEED and RDRAND, and why RDSEED
+ * is the preferred choice, see https://goo.gl/oK3KcN
+ *
+ * Returns the total entropy count, if it exceeds the requested
+ * entropy count. Otherwise, returns an entropy count of 0.
+ */
+size_t rand_acquire_entropy_from_cpu(RAND_POOL *pool)
+{
+    size_t bytes_needed;
+    unsigned char *buffer;
+
+    bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
+    if (bytes_needed > 0) {
+        buffer = rand_pool_add_begin(pool, bytes_needed);
+
+        if (buffer != NULL) {
+            /* Whichever comes first, use RDSEED, RDRAND or nothing */
+            if ((OPENSSL_ia32cap_P[2] & (1 << 18)) != 0) {
+                if (OPENSSL_ia32_rdseed_bytes(buffer, bytes_needed)
+                    == bytes_needed) {
+                    rand_pool_add_end(pool, bytes_needed, 8 * bytes_needed);
+                }
+            } else if ((OPENSSL_ia32cap_P[1] & (1 << (62 - 32))) != 0) {
+                if (OPENSSL_ia32_rdrand_bytes(buffer, bytes_needed)
+                    == bytes_needed) {
+                    rand_pool_add_end(pool, bytes_needed, 8 * bytes_needed);
+                }
+            } else {
+                rand_pool_add_end(pool, 0, 0);
+            }
+        }
+    }
+
+    return rand_pool_entropy_available(pool);
+}
+#endif
+
+
+/*
+ * Implements the get_entropy() callback (see RAND_DRBG_set_callbacks())
+ *
+ * If the DRBG has a parent, then the required amount of entropy input
+ * is fetched using the parent's RAND_DRBG_generate().
+ *
+ * Otherwise, the entropy is polled from the system entropy sources
+ * using rand_pool_acquire_entropy().
+ *
+ * If a random pool has been added to the DRBG using RAND_add(), then
+ * its entropy will be used up first.
+ */
+size_t rand_drbg_get_entropy(RAND_DRBG *drbg,
+                             unsigned char **pout,
+                             int entropy, size_t min_len, size_t max_len,
+                             int prediction_resistance)
+{
+    size_t ret = 0;
+    size_t entropy_available = 0;
+    RAND_POOL *pool;
+
+    if (drbg->parent && drbg->strength > drbg->parent->strength) {
+        /*
+         * We currently don't support the algorithm from NIST SP 800-90C
+         * 10.1.2 to use a weaker DRBG as source
+         */
+        RANDerr(RAND_F_RAND_DRBG_GET_ENTROPY, RAND_R_PARENT_STRENGTH_TOO_WEAK);
+        return 0;
+    }
+
+    if (drbg->pool != NULL) {
+        pool = drbg->pool;
+        pool->entropy_requested = entropy;
+    } else {
+        pool = rand_pool_new(entropy, min_len, max_len);
+        if (pool == NULL)
+            return 0;
+    }
+
+    if (drbg->parent) {
+        size_t bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
+        unsigned char *buffer = rand_pool_add_begin(pool, bytes_needed);
+
+        if (buffer != NULL) {
+            size_t bytes = 0;
+
+            /*
+             * Get random from parent, include our state as additional input.
+             * Our lock is already held, but we need to lock our parent before
+             * generating bits from it. (Note: taking the lock will be a no-op
+             * if locking if drbg->parent->lock == NULL.)
+             */
+            rand_drbg_lock(drbg->parent);
+            if (RAND_DRBG_generate(drbg->parent,
+                                   buffer, bytes_needed,
+                                   prediction_resistance,
+                                   NULL, 0) != 0)
+                bytes = bytes_needed;
+            drbg->reseed_next_counter
+                = tsan_load(&drbg->parent->reseed_prop_counter);
+            rand_drbg_unlock(drbg->parent);
+
+            rand_pool_add_end(pool, bytes, 8 * bytes);
+            entropy_available = rand_pool_entropy_available(pool);
+        }
+
+    } else {
+        if (prediction_resistance) {
+            /*
+             * We don't have any entropy sources that comply with the NIST
+             * standard to provide prediction resistance (see NIST SP 800-90C,
+             * Section 5.4).
+             */
+            RANDerr(RAND_F_RAND_DRBG_GET_ENTROPY,
+                    RAND_R_PREDICTION_RESISTANCE_NOT_SUPPORTED);
+            goto err;
+        }
+
+        /* Get entropy by polling system entropy sources. */
+        entropy_available = rand_pool_acquire_entropy(pool);
+    }
+
+    if (entropy_available > 0) {
+        ret   = rand_pool_length(pool);
+        *pout = rand_pool_detach(pool);
+    }
+
+ err:
+    /* we need to reset drbg->pool in the error case */
+    if (ret == 0 && drbg->pool != NULL)
+        drbg->pool = NULL;
+
+    rand_pool_free(pool);
+    return ret;
+}
+
+/*
+ * Implements the cleanup_entropy() callback (see RAND_DRBG_set_callbacks())
+ *
+ */
+void rand_drbg_cleanup_entropy(RAND_DRBG *drbg,
+                               unsigned char *out, size_t outlen)
+{
+    if (drbg->pool == NULL)
+        OPENSSL_secure_clear_free(out, outlen);
+    else
+        drbg->pool = NULL;
+}
+
+
+/*
+ * Implements the get_nonce() callback (see RAND_DRBG_set_callbacks())
+ *
+ */
+size_t rand_drbg_get_nonce(RAND_DRBG *drbg,
+                           unsigned char **pout,
+                           int entropy, size_t min_len, size_t max_len)
+{
+    size_t ret = 0;
+    RAND_POOL *pool;
+
+    struct {
+        void * instance;
+        int count;
+    } data = { 0 };
+
+    pool = rand_pool_new(0, min_len, max_len);
+    if (pool == NULL)
+        return 0;
+
+    if (rand_pool_add_nonce_data(pool) == 0)
+        goto err;
+
+    data.instance = drbg;
+    CRYPTO_atomic_add(&rand_nonce_count, 1, &data.count, rand_nonce_lock);
+
+    if (rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0) == 0)
+        goto err;
+
+    ret   = rand_pool_length(pool);
+    *pout = rand_pool_detach(pool);
+
+ err:
+    rand_pool_free(pool);
+
+    return ret;
+}
+
+/*
+ * Implements the cleanup_nonce() callback (see RAND_DRBG_set_callbacks())
+ *
+ */
+void rand_drbg_cleanup_nonce(RAND_DRBG *drbg,
+                             unsigned char *out, size_t outlen)
+{
+    OPENSSL_secure_clear_free(out, outlen);
+}
+
+/*
+ * Generate additional data that can be used for the drbg. The data does
+ * not need to contain entropy, but it's useful if it contains at least
+ * some bits that are unpredictable.
+ *
+ * Returns 0 on failure.
+ *
+ * On success it allocates a buffer at |*pout| and returns the length of
+ * the data. The buffer should get freed using OPENSSL_secure_clear_free().
+ */
+size_t rand_drbg_get_additional_data(unsigned char **pout, size_t max_len)
+{
+    size_t ret = 0;
+    RAND_POOL *pool;
+
+    pool = rand_pool_new(0, 0, max_len);
+    if (pool == NULL)
+        return 0;
+
+    if (rand_pool_add_additional_data(pool) == 0)
+        goto err;
+
+    ret = rand_pool_length(pool);
+    *pout = rand_pool_detach(pool);
+
+ err:
+    rand_pool_free(pool);
+
+    return ret;
+}
+
+void rand_drbg_cleanup_additional_data(unsigned char *out, size_t outlen)
+{
+    OPENSSL_secure_clear_free(out, outlen);
+}
+
+void rand_fork(void)
+{
+    rand_fork_count++;
+}
+
+DEFINE_RUN_ONCE_STATIC(do_rand_init)
+{
+#ifndef OPENSSL_NO_ENGINE
+    rand_engine_lock = CRYPTO_THREAD_lock_new();
+    if (rand_engine_lock == NULL)
+        return 0;
+#endif
+
+    rand_meth_lock = CRYPTO_THREAD_lock_new();
+    if (rand_meth_lock == NULL)
+        goto err1;
+
+    rand_nonce_lock = CRYPTO_THREAD_lock_new();
+    if (rand_nonce_lock == NULL)
+        goto err2;
+
+    if (!rand_cleaning_up && !rand_pool_init())
+        goto err3;
+
+    return 1;
+
+err3:
+    rand_pool_cleanup();
+err2:
+    CRYPTO_THREAD_lock_free(rand_meth_lock);
+    rand_meth_lock = NULL;
+err1:
+#ifndef OPENSSL_NO_ENGINE
+    CRYPTO_THREAD_lock_free(rand_engine_lock);
+    rand_engine_lock = NULL;
+#endif
+    return 0;
+}
+
+void rand_cleanup_int(void)
+{
+    const RAND_METHOD *meth = default_RAND_meth;
+
+    rand_cleaning_up = 1;
+
+    if (meth != NULL && meth->cleanup != NULL)
+        meth->cleanup();
+    RAND_set_rand_method(NULL);
+    rand_pool_cleanup();
+#ifndef OPENSSL_NO_ENGINE
+    CRYPTO_THREAD_lock_free(rand_engine_lock);
+    rand_engine_lock = NULL;
+#endif
+    CRYPTO_THREAD_lock_free(rand_meth_lock);
+    rand_meth_lock = NULL;
+    CRYPTO_THREAD_lock_free(rand_nonce_lock);
+    rand_nonce_lock = NULL;
+}
+
+/*
+ * RAND_close_seed_files() ensures that any seed file decriptors are
+ * closed after use.
+ */
+void RAND_keep_random_devices_open(int keep)
+{
+    rand_pool_keep_random_devices_open(keep);
+}
+
+/*
+ * RAND_poll() reseeds the default RNG using random input
+ *
+ * The random input is obtained from polling various entropy
+ * sources which depend on the operating system and are
+ * configurable via the --with-rand-seed configure option.
+ */
+int RAND_poll(void)
+{
+    int ret = 0;
+
+    RAND_POOL *pool = NULL;
+
+    const RAND_METHOD *meth = RAND_get_rand_method();
+
+    if (meth == RAND_OpenSSL()) {
+        /* fill random pool and seed the master DRBG */
+        RAND_DRBG *drbg = RAND_DRBG_get0_master();
+
+        if (drbg == NULL)
+            return 0;
+
+        rand_drbg_lock(drbg);
+        ret = rand_drbg_restart(drbg, NULL, 0, 0);
+        rand_drbg_unlock(drbg);
+
+        return ret;
+
+    } else {
+        /* fill random pool and seed the current legacy RNG */
+        pool = rand_pool_new(RAND_DRBG_STRENGTH,
+                             RAND_DRBG_STRENGTH / 8,
+                             RAND_POOL_MAX_LENGTH);
+        if (pool == NULL)
+            return 0;
 
-#ifdef NO_RAND
-static RAND_METHOD *rand_meth=NULL;
+        if (rand_pool_acquire_entropy(pool) == 0)
+            goto err;
+
+        if (meth->add == NULL
+            || meth->add(rand_pool_buffer(pool),
+                         rand_pool_length(pool),
+                         (rand_pool_entropy(pool) / 8.0)) == 0)
+            goto err;
+
+        ret = 1;
+    }
+
+err:
+    rand_pool_free(pool);
+    return ret;
+}
+
+/*
+ * Allocate memory and initialize a new random pool
+ */
+
+RAND_POOL *rand_pool_new(int entropy_requested, size_t min_len, size_t max_len)
+{
+    RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
+
+    if (pool == NULL) {
+        RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
+        return NULL;
+    }
+
+    pool->min_len = min_len;
+    pool->max_len = (max_len > RAND_POOL_MAX_LENGTH) ?
+        RAND_POOL_MAX_LENGTH : max_len;
+
+    pool->buffer = OPENSSL_secure_zalloc(pool->max_len);
+    if (pool->buffer == NULL) {
+        RANDerr(RAND_F_RAND_POOL_NEW, ERR_R_MALLOC_FAILURE);
+        goto err;
+    }
+
+    pool->entropy_requested = entropy_requested;
+
+    return pool;
+
+err:
+    OPENSSL_free(pool);
+    return NULL;
+}
+
+/*
+ * Attach new random pool to the given buffer
+ *
+ * This function is intended to be used only for feeding random data
+ * provided by RAND_add() and RAND_seed() into the <master> DRBG.
+ */
+RAND_POOL *rand_pool_attach(const unsigned char *buffer, size_t len,
+                            size_t entropy)
+{
+    RAND_POOL *pool = OPENSSL_zalloc(sizeof(*pool));
+
+    if (pool == NULL) {
+        RANDerr(RAND_F_RAND_POOL_ATTACH, ERR_R_MALLOC_FAILURE);
+        return NULL;
+    }
+
+    /*
+     * The const needs to be cast away, but attached buffers will not be
+     * modified (in contrary to allocated buffers which are zeroed and
+     * freed in the end).
+     */
+    pool->buffer = (unsigned char *) buffer;
+    pool->len = len;
+
+    pool->attached = 1;
+
+    pool->min_len = pool->max_len = pool->len;
+    pool->entropy = entropy;
+
+    return pool;
+}
+
+/*
+ * Free |pool|, securely erasing its buffer.
+ */
+void rand_pool_free(RAND_POOL *pool)
+{
+    if (pool == NULL)
+        return;
+
+    /*
+     * Although it would be advisable from a cryptographical viewpoint,
+     * we are not allowed to clear attached buffers, since they are passed
+     * to rand_pool_attach() as `const unsigned char*`.
+     * (see corresponding comment in rand_pool_attach()).
+     */
+    if (!pool->attached)
+        OPENSSL_secure_clear_free(pool->buffer, pool->max_len);
+    OPENSSL_free(pool);
+}
+
+/*
+ * Return the |pool|'s buffer to the caller (readonly).
+ */
+const unsigned char *rand_pool_buffer(RAND_POOL *pool)
+{
+    return pool->buffer;
+}
+
+/*
+ * Return the |pool|'s entropy to the caller.
+ */
+size_t rand_pool_entropy(RAND_POOL *pool)
+{
+    return pool->entropy;
+}
+
+/*
+ * Return the |pool|'s buffer length to the caller.
+ */
+size_t rand_pool_length(RAND_POOL *pool)
+{
+    return pool->len;
+}
+
+/*
+ * Detach the |pool| buffer and return it to the caller.
+ * It's the responsibility of the caller to free the buffer
+ * using OPENSSL_secure_clear_free().
+ */
+unsigned char *rand_pool_detach(RAND_POOL *pool)
+{
+    unsigned char *ret = pool->buffer;
+    pool->buffer = NULL;
+    return ret;
+}
+
+
+/*
+ * If |entropy_factor| bits contain 1 bit of entropy, how many bytes does one
+ * need to obtain at least |bits| bits of entropy?
+ */
+#define ENTROPY_TO_BYTES(bits, entropy_factor) \
+    (((bits) * (entropy_factor) + 7) / 8)
+
+
+/*
+ * Checks whether the |pool|'s entropy is available to the caller.
+ * This is the case when entropy count and buffer length are high enough.
+ * Returns
+ *
+ *  |entropy|  if the entropy count and buffer size is large enough
+ *      0      otherwise
+ */
+size_t rand_pool_entropy_available(RAND_POOL *pool)
+{
+    if (pool->entropy < pool->entropy_requested)
+        return 0;
+
+    if (pool->len < pool->min_len)
+        return 0;
+
+    return pool->entropy;
+}
+
+/*
+ * Returns the (remaining) amount of entropy needed to fill
+ * the random pool.
+ */
+
+size_t rand_pool_entropy_needed(RAND_POOL *pool)
+{
+    if (pool->entropy < pool->entropy_requested)
+        return pool->entropy_requested - pool->entropy;
+
+    return 0;
+}
+
+/*
+ * Returns the number of bytes needed to fill the pool, assuming
+ * the input has 1 / |entropy_factor| entropy bits per data bit.
+ * In case of an error, 0 is returned.
+ */
+
+size_t rand_pool_bytes_needed(RAND_POOL *pool, unsigned int entropy_factor)
+{
+    size_t bytes_needed;
+    size_t entropy_needed = rand_pool_entropy_needed(pool);
+
+    if (entropy_factor < 1) {
+        RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_ARGUMENT_OUT_OF_RANGE);
+        return 0;
+    }
+
+    bytes_needed = ENTROPY_TO_BYTES(entropy_needed, entropy_factor);
+
+    if (bytes_needed > pool->max_len - pool->len) {
+        /* not enough space left */
+        RANDerr(RAND_F_RAND_POOL_BYTES_NEEDED, RAND_R_RANDOM_POOL_OVERFLOW);
+        return 0;
+    }
+
+    if (pool->len < pool->min_len &&
+        bytes_needed < pool->min_len - pool->len)
+        /* to meet the min_len requirement */
+        bytes_needed = pool->min_len - pool->len;
+
+    return bytes_needed;
+}
+
+/* Returns the remaining number of bytes available */
+size_t rand_pool_bytes_remaining(RAND_POOL *pool)
+{
+    return pool->max_len - pool->len;
+}
+
+/*
+ * Add random bytes to the random pool.
+ *
+ * It is expected that the |buffer| contains |len| bytes of
+ * random input which contains at least |entropy| bits of
+ * randomness.
+ *
+ * Returns 1 if the added amount is adequate, otherwise 0
+ */
+int rand_pool_add(RAND_POOL *pool,
+                  const unsigned char *buffer, size_t len, size_t entropy)
+{
+    if (len > pool->max_len - pool->len) {
+        RANDerr(RAND_F_RAND_POOL_ADD, RAND_R_ENTROPY_INPUT_TOO_LONG);
+        return 0;
+    }
+
+    if (len > 0) {
+        memcpy(pool->buffer + pool->len, buffer, len);
+        pool->len += len;
+        pool->entropy += entropy;
+    }
+
+    return 1;
+}
+
+/*
+ * Start to add random bytes to the random pool in-place.
+ *
+ * Reserves the next |len| bytes for adding random bytes in-place
+ * and returns a pointer to the buffer.
+ * The caller is allowed to copy up to |len| bytes into the buffer.
+ * If |len| == 0 this is considered a no-op and a NULL pointer
+ * is returned without producing an error message.
+ *
+ * After updating the buffer, rand_pool_add_end() needs to be called
+ * to finish the udpate operation (see next comment).
+ */
+unsigned char *rand_pool_add_begin(RAND_POOL *pool, size_t len)
+{
+    if (len == 0)
+        return NULL;
+
+    if (len > pool->max_len - pool->len) {
+        RANDerr(RAND_F_RAND_POOL_ADD_BEGIN, RAND_R_RANDOM_POOL_OVERFLOW);
+        return NULL;
+    }
+
+    return pool->buffer + pool->len;
+}
+
+/*
+ * Finish to add random bytes to the random pool in-place.
+ *
+ * Finishes an in-place update of the random pool started by
+ * rand_pool_add_begin() (see previous comment).
+ * It is expected that |len| bytes of random input have been added
+ * to the buffer which contain at least |entropy| bits of randomness.
+ * It is allowed to add less bytes than originally reserved.
+ */
+int rand_pool_add_end(RAND_POOL *pool, size_t len, size_t entropy)
+{
+    if (len > pool->max_len - pool->len) {
+        RANDerr(RAND_F_RAND_POOL_ADD_END, RAND_R_RANDOM_POOL_OVERFLOW);
+        return 0;
+    }
+
+    if (len > 0) {
+        pool->len += len;
+        pool->entropy += entropy;
+    }
+
+    return 1;
+}
+
+int RAND_set_rand_method(const RAND_METHOD *meth)
+{
+    if (!RUN_ONCE(&rand_init, do_rand_init))
+        return 0;
+
+    CRYPTO_THREAD_write_lock(rand_meth_lock);
+#ifndef OPENSSL_NO_ENGINE
+    ENGINE_finish(funct_ref);
+    funct_ref = NULL;
+#endif
+    default_RAND_meth = meth;
+    CRYPTO_THREAD_unlock(rand_meth_lock);
+    return 1;
+}
+
+const RAND_METHOD *RAND_get_rand_method(void)
+{
+    const RAND_METHOD *tmp_meth = NULL;
+
+    if (!RUN_ONCE(&rand_init, do_rand_init))
+        return NULL;
+
+    CRYPTO_THREAD_write_lock(rand_meth_lock);
+    if (default_RAND_meth == NULL) {
+#ifndef OPENSSL_NO_ENGINE
+        ENGINE *e;
+
+        /* If we have an engine that can do RAND, use it. */
+        if ((e = ENGINE_get_default_RAND()) != NULL
+                && (tmp_meth = ENGINE_get_RAND(e)) != NULL) {
+            funct_ref = e;
+            default_RAND_meth = tmp_meth;
+        } else {
+            ENGINE_finish(e);
+            default_RAND_meth = &rand_meth;
+        }
 #else
-extern RAND_METHOD rand_ssleay_meth;
-static RAND_METHOD *rand_meth= &rand_ssleay_meth;
+        default_RAND_meth = &rand_meth;
+#endif
+    }
+    tmp_meth = default_RAND_meth;
+    CRYPTO_THREAD_unlock(rand_meth_lock);
+    return tmp_meth;
+}
+
+#ifndef OPENSSL_NO_ENGINE
+int RAND_set_rand_engine(ENGINE *engine)
+{
+    const RAND_METHOD *tmp_meth = NULL;
+
+    if (!RUN_ONCE(&rand_init, do_rand_init))
+        return 0;
+
+    if (engine != NULL) {
+        if (!ENGINE_init(engine))
+            return 0;
+        tmp_meth = ENGINE_get_RAND(engine);
+        if (tmp_meth == NULL) {
+            ENGINE_finish(engine);
+            return 0;
+        }
+    }
+    CRYPTO_THREAD_write_lock(rand_engine_lock);
+    /* This function releases any prior ENGINE so call it first */
+    RAND_set_rand_method(tmp_meth);
+    funct_ref = engine;
+    CRYPTO_THREAD_unlock(rand_engine_lock);
+    return 1;
+}
+#endif
+
+void RAND_seed(const void *buf, int num)
+{
+    const RAND_METHOD *meth = RAND_get_rand_method();
+
+    if (meth->seed != NULL)
+        meth->seed(buf, num);
+}
+
+void RAND_add(const void *buf, int num, double randomness)
+{
+    const RAND_METHOD *meth = RAND_get_rand_method();
+
+    if (meth->add != NULL)
+        meth->add(buf, num, randomness);
+}
+
+/*
+ * This function is not part of RAND_METHOD, so if we're not using
+ * the default method, then just call RAND_bytes().  Otherwise make
+ * sure we're instantiated and use the private DRBG.
+ */
+int RAND_priv_bytes(unsigned char *buf, int num)
+{
+    const RAND_METHOD *meth = RAND_get_rand_method();
+    RAND_DRBG *drbg;
+    int ret;
+
+    if (meth != RAND_OpenSSL())
+        return RAND_bytes(buf, num);
+
+    drbg = RAND_DRBG_get0_private();
+    if (drbg == NULL)
+        return 0;
+
+    ret = RAND_DRBG_bytes(drbg, buf, num);
+    return ret;
+}
+
+int RAND_bytes(unsigned char *buf, int num)
+{
+    const RAND_METHOD *meth = RAND_get_rand_method();
+
+    if (meth->bytes != NULL)
+        return meth->bytes(buf, num);
+    RANDerr(RAND_F_RAND_BYTES, RAND_R_FUNC_NOT_IMPLEMENTED);
+    return -1;
+}
+
+#if OPENSSL_API_COMPAT < 0x10100000L
+int RAND_pseudo_bytes(unsigned char *buf, int num)
+{
+    const RAND_METHOD *meth = RAND_get_rand_method();
+
+    if (meth->pseudorand != NULL)
+        return meth->pseudorand(buf, num);
+    return -1;
+}
 #endif
 
-void RAND_set_rand_method(meth)
-RAND_METHOD *meth;
-       {
-       rand_meth=meth;
-       }
-
-RAND_METHOD *RAND_get_rand_method()
-       {
-       return(rand_meth);
-       }
-
-void RAND_cleanup()
-       {
-       if (rand_meth != NULL)
-               rand_meth->cleanup();
-       }
-
-void RAND_seed(buf,num)
-const void *buf;
-int num;
-       {
-       if (rand_meth != NULL)
-               rand_meth->seed(buf,num);
-       }
-
-void RAND_bytes(buf,num)
-unsigned char *buf;
-int num;
-       {
-       if (rand_meth != NULL)
-               rand_meth->bytes(buf,num);
-       }
+int RAND_status(void)
+{
+    const RAND_METHOD *meth = RAND_get_rand_method();
 
+    if (meth->status != NULL)
+        return meth->status();
+    return 0;
+}