Fix PRNG.

[openssl.git] / crypto / rand / 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) 1998-2000 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) */
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)
        {
        memset(state,0,sizeof(state));
        state_num=0;
        state_index=0;
        memset(md,0,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];
        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 */
        do_not_lock = crypto_lock_rand && (locking_thread == CRYPTO_thread_id());

        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);

        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;
                        }
                }
        memset((char *)&m,0,sizeof(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 < 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, 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];
        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;
        
        /* 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_lock_rand = 1;
        locking_thread = CRYPTO_thread_id();

        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;
        locking_thread = 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
                MD_Update(&m,buf,j); /* purify complains */
#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);

        memset(&m,0,sizeof(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)
                        (void)ERR_get_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()) */
        do_not_lock = crypto_lock_rand && (locking_thread == CRYPTO_thread_id());
        
        if (!do_not_lock)
                {
                CRYPTO_w_lock(CRYPTO_LOCK_RAND);
                
                /* prevent ssleay_rand_bytes() from trying to obtain the lock again */
                crypto_lock_rand = 1;
                locking_thread = CRYPTO_thread_id();
                }
        
        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;
                locking_thread = 0;
                
                CRYPTO_w_unlock(CRYPTO_LOCK_RAND);
                }
        
        return ret;
        }