openssl/crypto/bn/bn_rand.c

/* crypto/bn/bn_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).
 *
 */

#include <stdio.h>
#include <time.h>
#include "internal/cryptlib.h"
#include "bn_lcl.h"
#include <openssl/rand.h>
#include <openssl/sha.h>

static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
{
    unsigned char *buf = NULL;
    int ret = 0, bit, bytes, mask;
    time_t tim;

    if (bits < 0 || (bits == 1 && top > 0)) {
        BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
        return 0;
    }

    if (bits == 0) {
        BN_zero(rnd);
        return 1;
    }

    bytes = (bits + 7) / 8;
    bit = (bits - 1) % 8;
    mask = 0xff << (bit + 1);

    buf = OPENSSL_malloc(bytes);
    if (buf == NULL) {
        BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
        goto err;
    }

    /* make a random number and set the top and bottom bits */
    time(&tim);
    RAND_add(&tim, sizeof(tim), 0.0);

    if (pseudorand) {
        if (RAND_bytes(buf, bytes) <= 0)
            goto err;
    } else {
        if (RAND_bytes(buf, bytes) <= 0)
            goto err;
    }

    if (pseudorand == 2) {
        /*
         * generate patterns that are more likely to trigger BN library bugs
         */
        int i;
        unsigned char c;

        for (i = 0; i < bytes; i++) {
            if (RAND_bytes(&c, 1) <= 0)
                goto err;
            if (c >= 128 && i > 0)
                buf[i] = buf[i - 1];
            else if (c < 42)
                buf[i] = 0;
            else if (c < 84)
                buf[i] = 255;
        }
    }

    if (top >= 0) {
        if (top) {
            if (bit == 0) {
                buf[0] = 1;
                buf[1] |= 0x80;
            } else {
                buf[0] |= (3 << (bit - 1));
            }
        } else {
            buf[0] |= (1 << bit);
        }
    }
    buf[0] &= ~mask;
    if (bottom)                 /* set bottom bit if requested */
        buf[bytes - 1] |= 1;
    if (!BN_bin2bn(buf, bytes, rnd))
        goto err;
    ret = 1;
 err:
    OPENSSL_clear_free(buf, bytes);
    bn_check_top(rnd);
    return (ret);
}

int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
{
    return bnrand(0, rnd, bits, top, bottom);
}

int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
{
    return bnrand(1, rnd, bits, top, bottom);
}

int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
{
    return bnrand(2, rnd, bits, top, bottom);
}

/* random number r:  0 <= r < range */
static int bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
{
    int (*bn_rand) (BIGNUM *, int, int, int) =
        pseudo ? BN_pseudo_rand : BN_rand;
    int n;
    int count = 100;

    if (range->neg || BN_is_zero(range)) {
        BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
        return 0;
    }

    n = BN_num_bits(range);     /* n > 0 */

    /* BN_is_bit_set(range, n - 1) always holds */

    if (n == 1)
        BN_zero(r);
    else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
        /*
         * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
         * than range
         */
        do {
            if (!bn_rand(r, n + 1, -1, 0))
                return 0;
            /*
             * If r < 3*range, use r := r MOD range (which is either r, r -
             * range, or r - 2*range). Otherwise, iterate once more. Since
             * 3*range = 11..._2, each iteration succeeds with probability >=
             * .75.
             */
            if (BN_cmp(r, range) >= 0) {
                if (!BN_sub(r, r, range))
                    return 0;
                if (BN_cmp(r, range) >= 0)
                    if (!BN_sub(r, r, range))
                        return 0;
            }

            if (!--count) {
                BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
                return 0;
            }

        }
        while (BN_cmp(r, range) >= 0);
    } else {
        do {
            /* range = 11..._2  or  range = 101..._2 */
            if (!bn_rand(r, n, -1, 0))
                return 0;

            if (!--count) {
                BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
                return 0;
            }
        }
        while (BN_cmp(r, range) >= 0);
    }

    bn_check_top(r);
    return 1;
}

int BN_rand_range(BIGNUM *r, const BIGNUM *range)
{
    return bn_rand_range(0, r, range);
}

int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
{
    return bn_rand_range(1, r, range);
}

/*
 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
 * BN_rand_range, it also includes the contents of |priv| and |message| in
 * the generation so that an RNG failure isn't fatal as long as |priv|
 * remains secret. This is intended for use in DSA and ECDSA where an RNG
 * weakness leads directly to private key exposure unless this function is
 * used.
 */
int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
                          const BIGNUM *priv, const unsigned char *message,
                          size_t message_len, BN_CTX *ctx)
{
    SHA512_CTX sha;
    /*
     * We use 512 bits of random data per iteration to ensure that we have at
     * least |range| bits of randomness.
     */
    unsigned char random_bytes[64];
    unsigned char digest[SHA512_DIGEST_LENGTH];
    unsigned done, todo;
    /* We generate |range|+8 bytes of random output. */
    const unsigned num_k_bytes = BN_num_bytes(range) + 8;
    unsigned char private_bytes[96];
    unsigned char *k_bytes;
    int ret = 0;

    k_bytes = OPENSSL_malloc(num_k_bytes);
    if (k_bytes == NULL)
        goto err;

    /* We copy |priv| into a local buffer to avoid exposing its length. */
    todo = sizeof(priv->d[0]) * priv->top;
    if (todo > sizeof(private_bytes)) {
        /*
         * No reasonable DSA or ECDSA key should have a private key this
         * large and we don't handle this case in order to avoid leaking the
         * length of the private key.
         */
        BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
        goto err;
    }
    memcpy(private_bytes, priv->d, todo);
    memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);

    for (done = 0; done < num_k_bytes;) {
        if (RAND_bytes(random_bytes, sizeof(random_bytes)) != 1)
            goto err;
        SHA512_Init(&sha);
        SHA512_Update(&sha, &done, sizeof(done));
        SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
        SHA512_Update(&sha, message, message_len);
        SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
        SHA512_Final(digest, &sha);

        todo = num_k_bytes - done;
        if (todo > SHA512_DIGEST_LENGTH)
            todo = SHA512_DIGEST_LENGTH;
        memcpy(k_bytes + done, digest, todo);
        done += todo;
    }

    if (!BN_bin2bn(k_bytes, num_k_bytes, out))
        goto err;
    if (BN_mod(out, out, range, ctx) != 1)
        goto err;
    ret = 1;

 err:
    OPENSSL_free(k_bytes);
    return ret;
}