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md_rand.c

/* crypto/rand/md_rand.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 (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).
 *
 */

#ifdef MD_RAND_DEBUG
# ifndef NDEBUG
#   define NDEBUG
# endif
#endif

#include <assert.h>
#include <stdio.h>
#include <string.h>

#include "e_os.h"

#include <openssl/rand.h>
#include "rand_lcl.h"

#include <openssl/crypto.h>
#include <openssl/err.h>

#ifdef BN_DEBUG
# define PREDICT
#endif

/* #define PREDICT      1 */

#define STATE_SIZE      1023
static int state_num=0,state_index=0;
static unsigned char state[STATE_SIZE+MD_DIGEST_LENGTH];
static unsigned char md[MD_DIGEST_LENGTH];
static long md_count[2]={0,0};
static double entropy=0;
static int initialized=0;

static unsigned int crypto_lock_rand = 0; /* may be set only when a thread
                                           * holds CRYPTO_LOCK_RAND
                                           * (to prevent double locking) */
/* access to lockin_thread is synchronized by CRYPTO_LOCK_RAND2 */
static unsigned long locking_thread = 0; /* valid iff crypto_lock_rand is set */


#ifdef PREDICT
int rand_predictable=0;
#endif

const char *RAND_version="RAND" OPENSSL_VERSION_PTEXT;

static void ssleay_rand_cleanup(void);
static void ssleay_rand_seed(const void *buf, int num);
static void ssleay_rand_add(const void *buf, int num, double add_entropy);
static int ssleay_rand_bytes(unsigned char *buf, int num);
static int ssleay_rand_pseudo_bytes(unsigned char *buf, int num);
static int ssleay_rand_status(void);

RAND_METHOD rand_ssleay_meth={
      ssleay_rand_seed,
      ssleay_rand_bytes,
      ssleay_rand_cleanup,
      ssleay_rand_add,
      ssleay_rand_pseudo_bytes,
      ssleay_rand_status
      }; 

RAND_METHOD *RAND_SSLeay(void)
      {
      return(&rand_ssleay_meth);
      }

static void ssleay_rand_cleanup(void)
      {
      OPENSSL_cleanse(state,sizeof(state));
      state_num=0;
      state_index=0;
      OPENSSL_cleanse(md,MD_DIGEST_LENGTH);
      md_count[0]=0;
      md_count[1]=0;
      entropy=0;
      initialized=0;
      }

static void ssleay_rand_add(const void *buf, int num, double add)
      {
      int i,j,k,st_idx;
      long md_c[2];
      unsigned char local_md[MD_DIGEST_LENGTH];
      EVP_MD_CTX m;
      int do_not_lock;

      /*
       * (Based on the rand(3) manpage)
       *
       * The input is chopped up into units of 20 bytes (or less for
       * the last block).  Each of these blocks is run through the hash
       * function as follows:  The data passed to the hash function
       * is the current 'md', the same number of bytes from the 'state'
       * (the location determined by in incremented looping index) as
       * the current 'block', the new key data 'block', and 'count'
       * (which is incremented after each use).
       * The result of this is kept in 'md' and also xored into the
       * 'state' at the same locations that were used as input into the
         * hash function.
       */

      /* check if we already have the lock */
      if (crypto_lock_rand)
            {
            CRYPTO_r_lock(CRYPTO_LOCK_RAND2);
            do_not_lock = (locking_thread == CRYPTO_thread_id());
            CRYPTO_r_unlock(CRYPTO_LOCK_RAND2);
            }
      else
            do_not_lock = 0;

      if (!do_not_lock) CRYPTO_w_lock(CRYPTO_LOCK_RAND);
      st_idx=state_index;

      /* use our own copies of the counters so that even
       * if a concurrent thread seeds with exactly the
       * same data and uses the same subarray there's _some_
       * difference */
      md_c[0] = md_count[0];
      md_c[1] = md_count[1];

      memcpy(local_md, md, sizeof md);

      /* state_index <= state_num <= STATE_SIZE */
      state_index += num;
      if (state_index >= STATE_SIZE)
            {
            state_index%=STATE_SIZE;
            state_num=STATE_SIZE;
            }
      else if (state_num < STATE_SIZE)    
            {
            if (state_index > state_num)
                  state_num=state_index;
            }
      /* state_index <= state_num <= STATE_SIZE */

      /* state[st_idx], ..., state[(st_idx + num - 1) % STATE_SIZE]
       * are what we will use now, but other threads may use them
       * as well */

      md_count[1] += (num / MD_DIGEST_LENGTH) + (num % MD_DIGEST_LENGTH > 0);

      if (!do_not_lock) CRYPTO_w_unlock(CRYPTO_LOCK_RAND);

      EVP_MD_CTX_init(&m);
      for (i=0; i<num; i+=MD_DIGEST_LENGTH)
            {
            j=(num-i);
            j=(j > MD_DIGEST_LENGTH)?MD_DIGEST_LENGTH:j;

            MD_Init(&m);
            MD_Update(&m,local_md,MD_DIGEST_LENGTH);
            k=(st_idx+j)-STATE_SIZE;
            if (k > 0)
                  {
                  MD_Update(&m,&(state[st_idx]),j-k);
                  MD_Update(&m,&(state[0]),k);
                  }
            else
                  MD_Update(&m,&(state[st_idx]),j);
                  
            MD_Update(&m,buf,j);
            MD_Update(&m,(unsigned char *)&(md_c[0]),sizeof(md_c));
            MD_Final(&m,local_md);
            md_c[1]++;

            buf=(const char *)buf + j;

            for (k=0; k<j; k++)
                  {
                  /* Parallel threads may interfere with this,
                   * but always each byte of the new state is
                   * the XOR of some previous value of its
                   * and local_md (itermediate values may be lost).
                   * Alway using locking could hurt performance more
                   * than necessary given that conflicts occur only
                   * when the total seeding is longer than the random
                   * state. */
                  state[st_idx++]^=local_md[k];
                  if (st_idx >= STATE_SIZE)
                        st_idx=0;
                  }
            }
      EVP_MD_CTX_cleanup(&m);

      if (!do_not_lock) CRYPTO_w_lock(CRYPTO_LOCK_RAND);
      /* Don't just copy back local_md into md -- this could mean that
       * other thread's seeding remains without effect (except for
       * the incremented counter).  By XORing it we keep at least as
       * much entropy as fits into md. */
      for (k = 0; k < (int)sizeof(md); k++)
            {
            md[k] ^= local_md[k];
            }
      if (entropy < ENTROPY_NEEDED) /* stop counting when we have enough */
          entropy += add;
      if (!do_not_lock) CRYPTO_w_unlock(CRYPTO_LOCK_RAND);
      
#if !defined(OPENSSL_THREADS) && !defined(OPENSSL_SYS_WIN32)
      assert(md_c[1] == md_count[1]);
#endif
      }

static void ssleay_rand_seed(const void *buf, int num)
      {
      ssleay_rand_add(buf, num, (double)num);
      }

static int ssleay_rand_bytes(unsigned char *buf, int num)
      {
      static volatile int stirred_pool = 0;
      int i,j,k,st_num,st_idx;
      int num_ceil;
      int ok;
      long md_c[2];
      unsigned char local_md[MD_DIGEST_LENGTH];
      EVP_MD_CTX m;
#ifndef GETPID_IS_MEANINGLESS
      pid_t curr_pid = getpid();
#endif
      int do_stir_pool = 0;

#ifdef PREDICT
      if (rand_predictable)
            {
            static unsigned char val=0;

            for (i=0; i<num; i++)
                  buf[i]=val++;
            return(1);
            }
#endif

      if (num <= 0)
            return 1;

      EVP_MD_CTX_init(&m);
      /* round upwards to multiple of MD_DIGEST_LENGTH/2 */
      num_ceil = (1 + (num-1)/(MD_DIGEST_LENGTH/2)) * (MD_DIGEST_LENGTH/2);

      /*
       * (Based on the rand(3) manpage:)
       *
       * For each group of 10 bytes (or less), we do the following:
       *
       * Input into the hash function the local 'md' (which is initialized from
       * the global 'md' before any bytes are generated), the bytes that are to
       * be overwritten by the random bytes, and bytes from the 'state'
       * (incrementing looping index). From this digest output (which is kept
       * in 'md'), the top (up to) 10 bytes are returned to the caller and the
       * bottom 10 bytes are xored into the 'state'.
       * 
       * Finally, after we have finished 'num' random bytes for the
       * caller, 'count' (which is incremented) and the local and global 'md'
       * are fed into the hash function and the results are kept in the
       * global 'md'.
       */

      CRYPTO_w_lock(CRYPTO_LOCK_RAND);

      /* prevent ssleay_rand_bytes() from trying to obtain the lock again */
      CRYPTO_w_lock(CRYPTO_LOCK_RAND2);
      locking_thread = CRYPTO_thread_id();
      CRYPTO_w_unlock(CRYPTO_LOCK_RAND2);
      crypto_lock_rand = 1;

      if (!initialized)
            {
            RAND_poll();
            initialized = 1;
            }
      
      if (!stirred_pool)
            do_stir_pool = 1;
      
      ok = (entropy >= ENTROPY_NEEDED);
      if (!ok)
            {
            /* If the PRNG state is not yet unpredictable, then seeing
             * the PRNG output may help attackers to determine the new
             * state; thus we have to decrease the entropy estimate.
             * Once we've had enough initial seeding we don't bother to
             * adjust the entropy count, though, because we're not ambitious
             * to provide *information-theoretic* randomness.
             *
             * NOTE: This approach fails if the program forks before
             * we have enough entropy. Entropy should be collected
             * in a separate input pool and be transferred to the
             * output pool only when the entropy limit has been reached.
             */
            entropy -= num;
            if (entropy < 0)
                  entropy = 0;
            }

      if (do_stir_pool)
            {
            /* In the output function only half of 'md' remains secret,
             * so we better make sure that the required entropy gets
             * 'evenly distributed' through 'state', our randomness pool.
             * The input function (ssleay_rand_add) chains all of 'md',
             * which makes it more suitable for this purpose.
             */

            int n = STATE_SIZE; /* so that the complete pool gets accessed */
            while (n > 0)
                  {
#if MD_DIGEST_LENGTH > 20
# error "Please adjust DUMMY_SEED."
#endif
#define DUMMY_SEED "...................." /* at least MD_DIGEST_LENGTH */
                  /* Note that the seed does not matter, it's just that
                   * ssleay_rand_add expects to have something to hash. */
                  ssleay_rand_add(DUMMY_SEED, MD_DIGEST_LENGTH, 0.0);
                  n -= MD_DIGEST_LENGTH;
                  }
            if (ok)
                  stirred_pool = 1;
            }

      st_idx=state_index;
      st_num=state_num;
      md_c[0] = md_count[0];
      md_c[1] = md_count[1];
      memcpy(local_md, md, sizeof md);

      state_index+=num_ceil;
      if (state_index > state_num)
            state_index %= state_num;

      /* state[st_idx], ..., state[(st_idx + num_ceil - 1) % st_num]
       * are now ours (but other threads may use them too) */

      md_count[0] += 1;

      /* before unlocking, we must clear 'crypto_lock_rand' */
      crypto_lock_rand = 0;
      CRYPTO_w_unlock(CRYPTO_LOCK_RAND);

      while (num > 0)
            {
            /* num_ceil -= MD_DIGEST_LENGTH/2 */
            j=(num >= MD_DIGEST_LENGTH/2)?MD_DIGEST_LENGTH/2:num;
            num-=j;
            MD_Init(&m);
#ifndef GETPID_IS_MEANINGLESS
            if (curr_pid) /* just in the first iteration to save time */
                  {
                  MD_Update(&m,(unsigned char*)&curr_pid,sizeof curr_pid);
                  curr_pid = 0;
                  }
#endif
            MD_Update(&m,local_md,MD_DIGEST_LENGTH);
            MD_Update(&m,(unsigned char *)&(md_c[0]),sizeof(md_c));
#ifndef PURIFY
#if 0 /* Don't add uninitialised data. */
            MD_Update(&m,buf,j); /* purify complains */
#endif
#endif
            k=(st_idx+MD_DIGEST_LENGTH/2)-st_num;
            if (k > 0)
                  {
                  MD_Update(&m,&(state[st_idx]),MD_DIGEST_LENGTH/2-k);
                  MD_Update(&m,&(state[0]),k);
                  }
            else
                  MD_Update(&m,&(state[st_idx]),MD_DIGEST_LENGTH/2);
            MD_Final(&m,local_md);

            for (i=0; i<MD_DIGEST_LENGTH/2; i++)
                  {
                  state[st_idx++]^=local_md[i]; /* may compete with other threads */
                  if (st_idx >= st_num)
                        st_idx=0;
                  if (i < j)
                        *(buf++)=local_md[i+MD_DIGEST_LENGTH/2];
                  }
            }

      MD_Init(&m);
      MD_Update(&m,(unsigned char *)&(md_c[0]),sizeof(md_c));
      MD_Update(&m,local_md,MD_DIGEST_LENGTH);
      CRYPTO_w_lock(CRYPTO_LOCK_RAND);
      MD_Update(&m,md,MD_DIGEST_LENGTH);
      MD_Final(&m,md);
      CRYPTO_w_unlock(CRYPTO_LOCK_RAND);

      EVP_MD_CTX_cleanup(&m);
      if (ok)
            return(1);
      else
            {
            RANDerr(RAND_F_SSLEAY_RAND_BYTES,RAND_R_PRNG_NOT_SEEDED);
            ERR_add_error_data(1, "You need to read the OpenSSL FAQ, "
                  "http://www.openssl.org/support/faq.html");
            return(0);
            }
      }

/* pseudo-random bytes that are guaranteed to be unique but not
   unpredictable */
static int ssleay_rand_pseudo_bytes(unsigned char *buf, int num) 
      {
      int ret;
      unsigned long err;

      ret = RAND_bytes(buf, num);
      if (ret == 0)
            {
            err = ERR_peek_error();
            if (ERR_GET_LIB(err) == ERR_LIB_RAND &&
                ERR_GET_REASON(err) == RAND_R_PRNG_NOT_SEEDED)
                  ERR_clear_error();
            }
      return (ret);
      }

static int ssleay_rand_status(void)
      {
      int ret;
      int do_not_lock;

      /* check if we already have the lock
       * (could happen if a RAND_poll() implementation calls RAND_status()) */
      if (crypto_lock_rand)
            {
            CRYPTO_r_lock(CRYPTO_LOCK_RAND2);
            do_not_lock = (locking_thread == CRYPTO_thread_id());
            CRYPTO_r_unlock(CRYPTO_LOCK_RAND2);
            }
      else
            do_not_lock = 0;
      
      if (!do_not_lock)
            {
            CRYPTO_w_lock(CRYPTO_LOCK_RAND);
            
            /* prevent ssleay_rand_bytes() from trying to obtain the lock again */
            CRYPTO_w_lock(CRYPTO_LOCK_RAND2);
            locking_thread = CRYPTO_thread_id();
            CRYPTO_w_unlock(CRYPTO_LOCK_RAND2);
            crypto_lock_rand = 1;
            }
      
      if (!initialized)
            {
            RAND_poll();
            initialized = 1;
            }

      ret = entropy >= ENTROPY_NEEDED;

      if (!do_not_lock)
            {
            /* before unlocking, we must clear 'crypto_lock_rand' */
            crypto_lock_rand = 0;
            
            CRYPTO_w_unlock(CRYPTO_LOCK_RAND);
            }
      
      return ret;
      }

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