/*

 * Copyright 1995-2025 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (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

 */

/*

 * DH low level APIs are deprecated for public use, but still ok for

 * internal use.

 */

#include "internal/deprecated.h"

#include <stdio.h>

#include "internal/cryptlib.h"

#include <openssl/bn.h>

#include <openssl/self_test.h>

#include "dh_local.h"

#include "crypto/dh.h"

/*-

 * Check that p and g are suitable enough

 *

 * p is odd

 * 1 < g < p - 1

 */

int DH_check_params_ex(const DH *dh)

{

    int errflags = 0;

    if (!DH_check_params(dh, &errflags))

        return 0;

    if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);

    if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);

    if ((errflags & DH_MODULUS_TOO_SMALL) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);

    if ((errflags & DH_MODULUS_TOO_LARGE) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);

    return errflags == 0;

}

#ifdef FIPS_MODULE

int DH_check_params(const DH *dh, int *ret)

{

    int nid;

    *ret = 0;

    /*

     * SP800-56A R3 Section 5.5.2 Assurances of Domain Parameter Validity

     * (1a) The domain parameters correspond to any approved safe prime group.

     */

    nid = DH_get_nid((DH *)dh);

    if (nid != NID_undef)

        return 1;

    /*

     * OR

     * (2b) FFC domain params conform to FIPS-186-4 explicit domain param

     * validity tests.

     */

    return ossl_ffc_params_FIPS186_4_validate(dh->libctx, &dh->params,

                                              FFC_PARAM_TYPE_DH, ret, NULL);

}

#else

int DH_check_params(const DH *dh, int *ret)

{

    int ok = 0;

    BIGNUM *tmp = NULL;

    BN_CTX *ctx = NULL;

    *ret = 0;

    ctx = BN_CTX_new_ex(dh->libctx);

    if (ctx == NULL)

        goto err;

    BN_CTX_start(ctx);

    tmp = BN_CTX_get(ctx);

    if (tmp == NULL)

        goto err;

    if (!BN_is_odd(dh->params.p))

        *ret |= DH_CHECK_P_NOT_PRIME;

    if (BN_is_negative(dh->params.g)

        || BN_is_zero(dh->params.g)

        || BN_is_one(dh->params.g))

        *ret |= DH_NOT_SUITABLE_GENERATOR;

    if (BN_copy(tmp, dh->params.p) == NULL || !BN_sub_word(tmp, 1))

        goto err;

    if (BN_cmp(dh->params.g, tmp) >= 0)

        *ret |= DH_NOT_SUITABLE_GENERATOR;

    if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS)

        *ret |= DH_MODULUS_TOO_SMALL;

    if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS)

        *ret |= DH_MODULUS_TOO_LARGE;

    ok = 1;

 err:

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

    return ok;

}

#endif /* FIPS_MODULE */

/*-

 * Check that p is a safe prime and

 * g is a suitable generator.

 */

int DH_check_ex(const DH *dh)

{

    int errflags = 0;

    if (!DH_check(dh, &errflags))

        return 0;

    if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);

    if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_Q_NOT_PRIME);

    if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_Q_VALUE);

    if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_J_VALUE);

    if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_UNABLE_TO_CHECK_GENERATOR);

    if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);

    if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_SAFE_PRIME);

    if ((errflags & DH_MODULUS_TOO_SMALL) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);

    if ((errflags & DH_MODULUS_TOO_LARGE) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);

    return errflags == 0;

}

/* Note: according to documentation - this only checks the params */

int DH_check(const DH *dh, int *ret)

{

#ifdef FIPS_MODULE

    return DH_check_params(dh, ret);

#else

    int ok = 0, r, q_good = 0;

    BN_CTX *ctx = NULL;

    BIGNUM *t1 = NULL, *t2 = NULL;

    int nid = DH_get_nid((DH *)dh);

    *ret = 0;

    if (nid != NID_undef)

        return 1;

    /* Don't do any checks at all with an excessively large modulus */

    if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {

        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);

        *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_P_NOT_PRIME;

        return 0;

    }

    if (!DH_check_params(dh, ret))

        return 0;

    ctx = BN_CTX_new_ex(dh->libctx);

    if (ctx == NULL)

        goto err;

    BN_CTX_start(ctx);

    t1 = BN_CTX_get(ctx);

    t2 = BN_CTX_get(ctx);

    if (t2 == NULL)

        goto err;

    if (dh->params.q != NULL) {

        if (BN_ucmp(dh->params.p, dh->params.q) > 0)

            q_good = 1;

        else

            *ret |= DH_CHECK_INVALID_Q_VALUE;

    }

    if (q_good) {

        if (BN_cmp(dh->params.g, BN_value_one()) <= 0)

            *ret |= DH_NOT_SUITABLE_GENERATOR;

        else if (BN_cmp(dh->params.g, dh->params.p) >= 0)

            *ret |= DH_NOT_SUITABLE_GENERATOR;

        else {

            /* Check g^q == 1 mod p */

            if (!BN_mod_exp(t1, dh->params.g, dh->params.q, dh->params.p, ctx))

                goto err;

            if (!BN_is_one(t1))

                *ret |= DH_NOT_SUITABLE_GENERATOR;

        }

        r = BN_check_prime(dh->params.q, ctx, NULL);

        if (r < 0)

            goto err;

        if (!r)

            *ret |= DH_CHECK_Q_NOT_PRIME;

        /* Check p == 1 mod q  i.e. q divides p - 1 */

        if (!BN_div(t1, t2, dh->params.p, dh->params.q, ctx))

            goto err;

        if (!BN_is_one(t2))

            *ret |= DH_CHECK_INVALID_Q_VALUE;

        if (dh->params.j != NULL

            && BN_cmp(dh->params.j, t1))

            *ret |= DH_CHECK_INVALID_J_VALUE;

    }

    r = BN_check_prime(dh->params.p, ctx, NULL);

    if (r < 0)

        goto err;

    if (!r)

        *ret |= DH_CHECK_P_NOT_PRIME;

    else if (dh->params.q == NULL) {

        if (!BN_rshift1(t1, dh->params.p))

            goto err;

        r = BN_check_prime(t1, ctx, NULL);

        if (r < 0)

            goto err;

        if (!r)

            *ret |= DH_CHECK_P_NOT_SAFE_PRIME;

    }

    ok = 1;

 err:

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

    return ok;

#endif /* FIPS_MODULE */

}

int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)

{

    int errflags = 0;

    if (!DH_check_pub_key(dh, pub_key, &errflags))

        return 0;

    if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_SMALL);

    if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_LARGE);

    if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)

        ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_INVALID);

    return errflags == 0;

}

/*

 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.

 */

int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)

{

    /* Don't do any checks at all with an excessively large modulus */

    if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {

        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);

        *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID;

        return 0;

    }

    if (dh->params.q != NULL && BN_ucmp(dh->params.p, dh->params.q) < 0) {

        *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID;

        return 1;

    }

    return ossl_ffc_validate_public_key(&dh->params, pub_key, ret);

}

/*

 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.

 * To only be used with ephemeral FFC public keys generated using the approved

 * safe-prime groups.

 */

int ossl_dh_check_pub_key_partial(const DH *dh, const BIGNUM *pub_key, int *ret)

{

    return ossl_ffc_validate_public_key_partial(&dh->params, pub_key, ret)

           && *ret == 0;

}

int ossl_dh_check_priv_key(const DH *dh, const BIGNUM *priv_key, int *ret)

{

    int ok = 0;

    BIGNUM *two_powN = NULL, *upper;

    *ret = 0;

    two_powN = BN_new();

    if (two_powN == NULL)

        return 0;

    if (dh->params.q != NULL) {

        upper = dh->params.q;

#ifndef FIPS_MODULE

    } else if (dh->params.p != NULL) {

        /*

         * We do not have q so we just check the key is within some

         * reasonable range, or the number of bits is equal to dh->length.

         */

        int length = dh->length;

        if (length == 0) {

            length = BN_num_bits(dh->params.p) - 1;

            if (BN_num_bits(priv_key) <= length

                && BN_num_bits(priv_key) > 1)

                ok = 1;

        } else if (BN_num_bits(priv_key) == length) {

            ok = 1;

        }

        goto end;

#endif

    } else {

        goto end;

    }

    /* Is it from an approved Safe prime group ?*/

    if (DH_get_nid((DH *)dh) != NID_undef && dh->length != 0) {

        if (!BN_lshift(two_powN, BN_value_one(), dh->length))

            goto end;

        if (BN_cmp(two_powN, dh->params.q) < 0)

            upper = two_powN;

    }

    if (!ossl_ffc_validate_private_key(upper, priv_key, ret))

        goto end;

    ok = 1;

end:

    BN_free(two_powN);

    return ok;

}

/*

 * FFC pairwise check from SP800-56A R3.

 *    Section 5.6.2.1.4 Owner Assurance of Pair-wise Consistency

 */

int ossl_dh_check_pairwise(const DH *dh, int return_on_null_numbers)

{

    int ret = 0;

    BN_CTX *ctx = NULL;

    BIGNUM *pub_key = NULL;

    OSSL_SELF_TEST *st = NULL;

    OSSL_CALLBACK *stcb = NULL;

    void *stcbarg = NULL;

    if (dh->params.p == NULL

        || dh->params.g == NULL

        || dh->priv_key == NULL

        || dh->pub_key == NULL)

        return return_on_null_numbers;

    OSSL_SELF_TEST_get_callback(dh->libctx, &stcb, &stcbarg);

    st = OSSL_SELF_TEST_new(stcb, stcbarg);

    if (st == NULL)

        goto err;

    OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT,

                           OSSL_SELF_TEST_DESC_PCT_DH);

    ctx = BN_CTX_new_ex(dh->libctx);

    if (ctx == NULL)

        goto err;

    pub_key = BN_new();

    if (pub_key == NULL)

        goto err;

    /* recalculate the public key = (g ^ priv) mod p */

    if (!ossl_dh_generate_public_key(ctx, dh, dh->priv_key, pub_key))

        goto err;

#ifdef FIPS_MODULE

    {

        int len;

        unsigned char bytes[1024] = {0};    /* Max key size of 8192 bits */

        if (BN_num_bytes(pub_key) > (int)sizeof(bytes))

            goto err;

        len = BN_bn2bin(pub_key, bytes);

        OSSL_SELF_TEST_oncorrupt_byte(st, bytes);

        if (BN_bin2bn(bytes, len, pub_key) == NULL)

            goto err;

    }

#endif

    /* check it matches the existing public_key */

    ret = BN_cmp(pub_key, dh->pub_key) == 0;

 err:

    BN_free(pub_key);

    BN_CTX_free(ctx);

    OSSL_SELF_TEST_onend(st, ret);

    OSSL_SELF_TEST_free(st);

    return ret;

}