/* crypto/dh/dh_key.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.]

 */

#include <stdio.h>

#include "cryptlib.h"

#include <openssl/bn.h>

#include <openssl/rand.h>

#include <openssl/dh.h>

static int generate_key(DH *dh);

static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);

static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,

                         const BIGNUM *a, const BIGNUM *p,

                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);

static int dh_init(DH *dh);

static int dh_finish(DH *dh);

int DH_generate_key(DH *dh)

{

#ifdef OPENSSL_FIPS

    if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD)

        && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW)) {

        DHerr(DH_F_DH_GENERATE_KEY, DH_R_NON_FIPS_METHOD);

        return 0;

    }

#endif

    return dh->meth->generate_key(dh);

}

int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)

{

#ifdef OPENSSL_FIPS

    if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD)

        && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW)) {

        DHerr(DH_F_DH_COMPUTE_KEY, DH_R_NON_FIPS_METHOD);

        return 0;

    }

#endif

    return dh->meth->compute_key(key, pub_key, dh);

}

int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)

{

    int rv, pad;

    rv = dh->meth->compute_key(key, pub_key, dh);

    if (rv <= 0)

        return rv;

    pad = BN_num_bytes(dh->p) - rv;

    if (pad > 0) {

        memmove(key + pad, key, rv);

        memset(key, 0, pad);

    }

    return rv + pad;

}

static DH_METHOD dh_ossl = {

    "OpenSSL DH Method",

    generate_key,

    compute_key,

    dh_bn_mod_exp,

    dh_init,

    dh_finish,

    0,

    NULL,

    NULL

};

const DH_METHOD *DH_OpenSSL(void)

{

    return &dh_ossl;

}

static int generate_key(DH *dh)

{

    int ok = 0;

    int generate_new_key = 0;

    unsigned l;

    BN_CTX *ctx;

    BN_MONT_CTX *mont = NULL;

    BIGNUM *pub_key = NULL, *priv_key = NULL;

    ctx = BN_CTX_new();

    if (ctx == NULL)

        goto err;

    if (dh->priv_key == NULL) {

        priv_key = BN_new();

        if (priv_key == NULL)

            goto err;

        generate_new_key = 1;

    } else

        priv_key = dh->priv_key;

    if (dh->pub_key == NULL) {

        pub_key = BN_new();

        if (pub_key == NULL)

            goto err;

    } else

        pub_key = dh->pub_key;

    if (dh->flags & DH_FLAG_CACHE_MONT_P) {

        mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,

                                      CRYPTO_LOCK_DH, dh->p, ctx);

        if (!mont)

            goto err;

    }

    if (generate_new_key) {

        if (dh->q) {

            do {

                if (!BN_rand_range(priv_key, dh->q))

                    goto err;

            }

            while (BN_is_zero(priv_key) || BN_is_one(priv_key));

        } else {

            /* secret exponent length */

            l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;

            if (!BN_rand(priv_key, l, 0, 0))

                goto err;

        }

    }

    {

        BIGNUM local_prk;

        BIGNUM *prk;

        if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {

            BN_init(&local_prk);

            prk = &local_prk;

            BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);

        } else

            prk = priv_key;

        if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont))

            goto err;

    }

    dh->pub_key = pub_key;

    dh->priv_key = priv_key;

    ok = 1;

 err:

    if (ok != 1)

        DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);

    if ((pub_key != NULL) && (dh->pub_key == NULL))

        BN_free(pub_key);

    if ((priv_key != NULL) && (dh->priv_key == NULL))

        BN_free(priv_key);

    BN_CTX_free(ctx);

    return (ok);

}

static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)

{

    BN_CTX *ctx = NULL;

    BN_MONT_CTX *mont = NULL;

    BIGNUM *tmp;

    int ret = -1;

    int check_result;

    if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {

        DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);

        goto err;

    }

    ctx = BN_CTX_new();

    if (ctx == NULL)

        goto err;

    BN_CTX_start(ctx);

    tmp = BN_CTX_get(ctx);

    if (tmp == NULL)

        goto err;

    if (dh->priv_key == NULL) {

        DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);

        goto err;

    }

    if (dh->flags & DH_FLAG_CACHE_MONT_P) {

        mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,

                                      CRYPTO_LOCK_DH, dh->p, ctx);

        if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {

            /* XXX */

            BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);

        }

        if (!mont)

            goto err;

    }

    if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {

        DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);

        goto err;

    }

    if (!dh->

        meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {

        DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);

        goto err;

    }

    ret = BN_bn2bin(tmp, key);

 err:

    if (ctx != NULL) {

        BN_CTX_end(ctx);

        BN_CTX_free(ctx);

    }

    return (ret);

}

static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,

                         const BIGNUM *a, const BIGNUM *p,

                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)

{

    /*

     * If a is only one word long and constant time is false, use the faster

     * exponenentiation function.

     */

    if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) {

        BN_ULONG A = a->d[0];

        return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx);

    } else

        return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);

}

static int dh_init(DH *dh)

{

    dh->flags |= DH_FLAG_CACHE_MONT_P;

    return (1);

}

static int dh_finish(DH *dh)

{

    if (dh->method_mont_p)

        BN_MONT_CTX_free(dh->method_mont_p);

    return (1);

}