/*

 * Copyright 2019-2021 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

 */

/*

 * Finite Field cryptography (FFC) is used for DSA and DH.

 * This file contains methods for validation of FFC parameters.

 * It calls the same functions as the generation as the code is very similar.

 */

#include <openssl/err.h>

#include <openssl/bn.h>

#include <openssl/dsaerr.h>

#include <openssl/dherr.h>

#include "internal/ffc.h"

/* FIPS186-4 A.2.2 Unverifiable partial validation of Generator g */

int ossl_ffc_params_validate_unverifiable_g(BN_CTX *ctx, BN_MONT_CTX *mont,

                                            const BIGNUM *p, const BIGNUM *q,

                                            const BIGNUM *g, BIGNUM *tmp,

                                            int *ret)

{

    /*

     * A.2.2 Step (1) AND

     * A.2.4 Step (2)

     * Verify that 2 <= g <= (p - 1)

     */

    if (BN_cmp(g, BN_value_one()) <= 0 || BN_cmp(g, p) >= 0) {

        *ret |= FFC_ERROR_NOT_SUITABLE_GENERATOR;

        return 0;

    }

    /*

     * A.2.2 Step (2) AND

     * A.2.4 Step (3)

     * Check g^q mod p = 1

     */

    if (!BN_mod_exp_mont(tmp, g, q, p, ctx, mont))

        return 0;

    if (BN_cmp(tmp, BN_value_one()) != 0) {

        *ret |= FFC_ERROR_NOT_SUITABLE_GENERATOR;

        return 0;

    }

    return 1;

}

int ossl_ffc_params_FIPS186_4_validate(OSSL_LIB_CTX *libctx,

                                       const FFC_PARAMS *params, int type,

                                       int *res, BN_GENCB *cb)

{

    size_t L, N;

    if (params == NULL || params->p == NULL || params->q == NULL)

        return FFC_PARAM_RET_STATUS_FAILED;

    /* A.1.1.3 Step (1..2) : L = len(p), N = len(q) */

    L = BN_num_bits(params->p);

    N = BN_num_bits(params->q);

    return ossl_ffc_params_FIPS186_4_gen_verify(libctx, (FFC_PARAMS *)params,

                                                FFC_PARAM_MODE_VERIFY, type,

                                                L, N, res, cb);

}

/* This may be used in FIPS mode to validate deprecated FIPS-186-2 Params */

int ossl_ffc_params_FIPS186_2_validate(OSSL_LIB_CTX *libctx,

                                       const FFC_PARAMS *params, int type,

                                       int *res, BN_GENCB *cb)

{

    size_t L, N;

    if (params == NULL || params->p == NULL || params->q == NULL) {

        *res = FFC_CHECK_INVALID_PQ;

        return FFC_PARAM_RET_STATUS_FAILED;

    }

    /* A.1.1.3 Step (1..2) : L = len(p), N = len(q) */

    L = BN_num_bits(params->p);

    N = BN_num_bits(params->q);

    return ossl_ffc_params_FIPS186_2_gen_verify(libctx, (FFC_PARAMS *)params,

                                                FFC_PARAM_MODE_VERIFY, type,

                                                L, N, res, cb);

}

/*

 * This does a simple check of L and N and partial g.

 * It makes no attempt to do a full validation of p, q or g since these require

 * extra parameters such as the digest and seed, which may not be available for

 * this test.

 */

int ossl_ffc_params_simple_validate(OSSL_LIB_CTX *libctx, const FFC_PARAMS *params,

                                    int paramstype, int *res)

{

    int ret;

    int tmpres = 0;

    FFC_PARAMS tmpparams = {0};

    if (params == NULL)

        return 0;

    if (res == NULL)

        res = &tmpres;

    if (!ossl_ffc_params_copy(&tmpparams, params))

        return 0;

    tmpparams.flags = FFC_PARAM_FLAG_VALIDATE_G;

    tmpparams.gindex = FFC_UNVERIFIABLE_GINDEX;

#ifndef FIPS_MODULE

    if (params->flags & FFC_PARAM_FLAG_VALIDATE_LEGACY)

        ret = ossl_ffc_params_FIPS186_2_validate(libctx, &tmpparams, paramstype,

                                                 res, NULL);

    else

#endif

        ret = ossl_ffc_params_FIPS186_4_validate(libctx, &tmpparams, paramstype,

                                                 res, NULL);

#ifndef OPENSSL_NO_DH

    if (ret == FFC_PARAM_RET_STATUS_FAILED

        && (*res & FFC_ERROR_NOT_SUITABLE_GENERATOR) != 0) {

        ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);

    }

#endif

    ossl_ffc_params_cleanup(&tmpparams);

    return ret != FFC_PARAM_RET_STATUS_FAILED;

}

/*

 * If possible (or always in FIPS_MODULE) do full FIPS 186-4 validation.

 * Otherwise do simple check but in addition also check the primality of the

 * p and q.

 */

int ossl_ffc_params_full_validate(OSSL_LIB_CTX *libctx, const FFC_PARAMS *params,

                                  int paramstype, int *res)

{

    int tmpres = 0;

    if (params == NULL)

        return 0;

    if (res == NULL)

        res = &tmpres;

#ifdef FIPS_MODULE

    return ossl_ffc_params_FIPS186_4_validate(libctx, params, paramstype,

                                              res, NULL);

#else

    if (params->seed != NULL) {

        if (params->flags & FFC_PARAM_FLAG_VALIDATE_LEGACY)

            return ossl_ffc_params_FIPS186_2_validate(libctx, params, paramstype,

                                                      res, NULL);

        else

            return ossl_ffc_params_FIPS186_4_validate(libctx, params, paramstype,

                                                      res, NULL);

    } else {

        int ret = 0;

        ret = ossl_ffc_params_simple_validate(libctx, params, paramstype, res);

        if (ret) {

            BN_CTX *ctx;

            if ((ctx = BN_CTX_new_ex(libctx)) == NULL)

                return 0;

            if (BN_check_prime(params->q, ctx, NULL) != 1) {

# ifndef OPENSSL_NO_DSA

                ERR_raise(ERR_LIB_DSA, DSA_R_Q_NOT_PRIME);

# endif

                ret = 0;

            }

            if (ret && BN_check_prime(params->p, ctx, NULL) != 1) {

# ifndef OPENSSL_NO_DSA

                ERR_raise(ERR_LIB_DSA, DSA_R_P_NOT_PRIME);

# endif

                ret = 0;

            }

            BN_CTX_free(ctx);

        }

        return ret;

    }

#endif

}