/*

 * Copyright 2018-2023 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright (c) 2018-2019, Oracle and/or its affiliates.  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

 */

/*

 * According to NIST SP800-131A "Transitioning the use of cryptographic

 * algorithms and key lengths" Generation of 1024 bit RSA keys are no longer

 * allowed for signatures (Table 2) or key transport (Table 5). In the code

 * below any attempt to generate 1024 bit RSA keys will result in an error (Note

 * that digital signature verification can still use deprecated 1024 bit keys).

 *

 * FIPS 186-4 relies on the use of the auxiliary primes p1, p2, q1 and q2 that

 * must be generated before the module generates the RSA primes p and q.

 * Table B.1 in FIPS 186-4 specifies RSA modulus lengths of 2048 and

 * 3072 bits only, the min/max total length of the auxiliary primes.

 * FIPS 186-5 Table A.1 includes an additional entry for 4096 which has been

 * included here.

 */

#include <stdio.h>

#include <openssl/bn.h>

#include "bn_local.h"

#include "crypto/bn.h"

#include "internal/nelem.h"

#if BN_BITS2 == 64

# define BN_DEF(lo, hi) (BN_ULONG)hi<<32|lo

#else

# define BN_DEF(lo, hi) lo, hi

#endif

/* 1 / sqrt(2) * 2^256, rounded up */

static const BN_ULONG inv_sqrt_2_val[] = {

    BN_DEF(0x83339916UL, 0xED17AC85UL), BN_DEF(0x893BA84CUL, 0x1D6F60BAUL),

    BN_DEF(0x754ABE9FUL, 0x597D89B3UL), BN_DEF(0xF9DE6484UL, 0xB504F333UL)

};

const BIGNUM ossl_bn_inv_sqrt_2 = {

    (BN_ULONG *)inv_sqrt_2_val,

    OSSL_NELEM(inv_sqrt_2_val),

    OSSL_NELEM(inv_sqrt_2_val),

    0,

    BN_FLG_STATIC_DATA

};

/*

 * FIPS 186-5 Table A.1. "Min length of auxiliary primes p1, p2, q1, q2".

 * (FIPS 186-5 has an entry for >= 4096 bits).

 *

 * Params:

 *     nbits The key size in bits.

 * Returns:

 *     The minimum size of the auxiliary primes or 0 if nbits is invalid.

 */

static int bn_rsa_fips186_5_aux_prime_min_size(int nbits)

{

    if (nbits >= 4096)

        return 201;

    if (nbits >= 3072)

        return 171;

    if (nbits >= 2048)

        return 141;

    return 0;

}

/*

 * FIPS 186-5 Table A.1 "Max of len(p1) + len(p2) and

 * len(q1) + len(q2) for p,q Probable Primes".

 * (FIPS 186-5 has an entry for >= 4096 bits).

 * Params:

 *     nbits The key size in bits.

 * Returns:

 *     The maximum length or 0 if nbits is invalid.

 */

static int bn_rsa_fips186_5_aux_prime_max_sum_size_for_prob_primes(int nbits)

{

    if (nbits >= 4096)

        return 2030;

    if (nbits >= 3072)

        return 1518;

    if (nbits >= 2048)

        return 1007;

    return 0;

}

/*

 * Find the first odd integer that is a probable prime.

 *

 * See section FIPS 186-4 B.3.6 (Steps 4.2/5.2).

 *

 * Params:

 *     Xp1 The passed in starting point to find a probably prime.

 *     p1 The returned probable prime (first odd integer >= Xp1)

 *     ctx A BN_CTX object.

 *     cb An optional BIGNUM callback.

 * Returns: 1 on success otherwise it returns 0.

 */

static int bn_rsa_fips186_4_find_aux_prob_prime(const BIGNUM *Xp1,

                                                BIGNUM *p1, BN_CTX *ctx,

                                                BN_GENCB *cb)

{

    int ret = 0;

    int i = 0;

    int tmp = 0;

    if (BN_copy(p1, Xp1) == NULL)

        return 0;

    BN_set_flags(p1, BN_FLG_CONSTTIME);

    /* Find the first odd number >= Xp1 that is probably prime */

    for(;;) {

        i++;

        BN_GENCB_call(cb, 0, i);

        /* MR test with trial division */

        tmp = BN_check_prime(p1, ctx, cb);

        if (tmp > 0)

            break;

        if (tmp < 0)

            goto err;

        /* Get next odd number */

        if (!BN_add_word(p1, 2))

            goto err;

    }

    BN_GENCB_call(cb, 2, i);

    ret = 1;

err:

    return ret;

}

/*

 * Generate a probable prime (p or q).

 *

 * See FIPS 186-4 B.3.6 (Steps 4 & 5)

 *

 * Params:

 *     p The returned probable prime.

 *     Xpout An optionally returned random number used during generation of p.

 *     p1, p2 The returned auxiliary primes. If NULL they are not returned.

 *     Xp An optional passed in value (that is random number used during

 *        generation of p).

 *     Xp1, Xp2 Optional passed in values that are normally generated

 *              internally. Used to find p1, p2.

 *     nlen The bit length of the modulus (the key size).

 *     e The public exponent.

 *     ctx A BN_CTX object.

 *     cb An optional BIGNUM callback.

 * Returns: 1 on success otherwise it returns 0.

 */

int ossl_bn_rsa_fips186_4_gen_prob_primes(BIGNUM *p, BIGNUM *Xpout,

                                          BIGNUM *p1, BIGNUM *p2,

                                          const BIGNUM *Xp, const BIGNUM *Xp1,

                                          const BIGNUM *Xp2, int nlen,

                                          const BIGNUM *e, BN_CTX *ctx,

                                          BN_GENCB *cb)

{

    int ret = 0;

    BIGNUM *p1i = NULL, *p2i = NULL, *Xp1i = NULL, *Xp2i = NULL;

    int bitlen;

    if (p == NULL || Xpout == NULL)

        return 0;

    BN_CTX_start(ctx);

    p1i = (p1 != NULL) ? p1 : BN_CTX_get(ctx);

    p2i = (p2 != NULL) ? p2 : BN_CTX_get(ctx);

    Xp1i = (Xp1 != NULL) ? (BIGNUM *)Xp1 : BN_CTX_get(ctx);

    Xp2i = (Xp2 != NULL) ? (BIGNUM *)Xp2 : BN_CTX_get(ctx);

    if (p1i == NULL || p2i == NULL || Xp1i == NULL || Xp2i == NULL)

        goto err;

    bitlen = bn_rsa_fips186_5_aux_prime_min_size(nlen);

    if (bitlen == 0)

        goto err;

    /* (Steps 4.1/5.1): Randomly generate Xp1 if it is not passed in */

    if (Xp1 == NULL) {

        /* Set the top and bottom bits to make it odd and the correct size */

        if (!BN_priv_rand_ex(Xp1i, bitlen, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ODD,

                             0, ctx))

            goto err;

    }

    /* (Steps 4.1/5.1): Randomly generate Xp2 if it is not passed in */

    if (Xp2 == NULL) {

        /* Set the top and bottom bits to make it odd and the correct size */

        if (!BN_priv_rand_ex(Xp2i, bitlen, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ODD,

                             0, ctx))

            goto err;

    }

    /* (Steps 4.2/5.2) - find first auxiliary probable primes */

    if (!bn_rsa_fips186_4_find_aux_prob_prime(Xp1i, p1i, ctx, cb)

            || !bn_rsa_fips186_4_find_aux_prob_prime(Xp2i, p2i, ctx, cb))

        goto err;

    /* (Table B.1) auxiliary prime Max length check */

    if ((BN_num_bits(p1i) + BN_num_bits(p2i)) >=

            bn_rsa_fips186_5_aux_prime_max_sum_size_for_prob_primes(nlen))

        goto err;

    /* (Steps 4.3/5.3) - generate prime */

    if (!ossl_bn_rsa_fips186_4_derive_prime(p, Xpout, Xp, p1i, p2i, nlen, e,

                                            ctx, cb))

        goto err;

    ret = 1;

err:

    /* Zeroize any internally generated values that are not returned */

    if (p1 == NULL)

        BN_clear(p1i);

    if (p2 == NULL)

        BN_clear(p2i);

    if (Xp1 == NULL)

        BN_clear(Xp1i);

    if (Xp2 == NULL)

        BN_clear(Xp2i);

    BN_CTX_end(ctx);

    return ret;

}

/*

 * Constructs a probable prime (a candidate for p or q) using 2 auxiliary

 * prime numbers and the Chinese Remainder Theorem.

 *

 * See FIPS 186-4 C.9 "Compute a Probable Prime Factor Based on Auxiliary

 * Primes". Used by FIPS 186-4 B.3.6 Section (4.3) for p and Section (5.3) for q.

 *

 * Params:

 *     Y The returned prime factor (private_prime_factor) of the modulus n.

 *     X The returned random number used during generation of the prime factor.

 *     Xin An optional passed in value for X used for testing purposes.

 *     r1 An auxiliary prime.

 *     r2 An auxiliary prime.

 *     nlen The desired length of n (the RSA modulus).

 *     e The public exponent.

 *     ctx A BN_CTX object.

 *     cb An optional BIGNUM callback object.

 * Returns: 1 on success otherwise it returns 0.

 * Assumptions:

 *     Y, X, r1, r2, e are not NULL.

 */

int ossl_bn_rsa_fips186_4_derive_prime(BIGNUM *Y, BIGNUM *X, const BIGNUM *Xin,

                                       const BIGNUM *r1, const BIGNUM *r2,

                                       int nlen, const BIGNUM *e, BN_CTX *ctx,

                                       BN_GENCB *cb)

{

    int ret = 0;

    int i, imax;

    int bits = nlen >> 1;

    BIGNUM *tmp, *R, *r1r2x2, *y1, *r1x2;

    BIGNUM *base, *range;

    BN_CTX_start(ctx);

    base = BN_CTX_get(ctx);

    range = BN_CTX_get(ctx);

    R = BN_CTX_get(ctx);

    tmp = BN_CTX_get(ctx);

    r1r2x2 = BN_CTX_get(ctx);

    y1 = BN_CTX_get(ctx);

    r1x2 = BN_CTX_get(ctx);

    if (r1x2 == NULL)

        goto err;

    if (Xin != NULL && BN_copy(X, Xin) == NULL)

        goto err;

    /*

     * We need to generate a random number X in the range

     * 1/sqrt(2) * 2^(nlen/2) <= X < 2^(nlen/2).

     * We can rewrite that as:

     * base = 1/sqrt(2) * 2^(nlen/2)

     * range = ((2^(nlen/2))) - (1/sqrt(2) * 2^(nlen/2))

     * X = base + random(range)

     * We only have the first 256 bit of 1/sqrt(2)

     */

    if (Xin == NULL) {

        if (bits < BN_num_bits(&ossl_bn_inv_sqrt_2))

            goto err;

        if (!BN_lshift(base, &ossl_bn_inv_sqrt_2,

                       bits - BN_num_bits(&ossl_bn_inv_sqrt_2))

            || !BN_lshift(range, BN_value_one(), bits)

            || !BN_sub(range, range, base))

            goto err;

    }

    if (!(BN_lshift1(r1x2, r1)

            /* (Step 1) GCD(2r1, r2) = 1 */

            && BN_gcd(tmp, r1x2, r2, ctx)

            && BN_is_one(tmp)

            /* (Step 2) R = ((r2^-1 mod 2r1) * r2) - ((2r1^-1 mod r2)*2r1) */

            && BN_mod_inverse(R, r2, r1x2, ctx)

            && BN_mul(R, R, r2, ctx) /* R = (r2^-1 mod 2r1) * r2 */

            && BN_mod_inverse(tmp, r1x2, r2, ctx)

            && BN_mul(tmp, tmp, r1x2, ctx) /* tmp = (2r1^-1 mod r2)*2r1 */

            && BN_sub(R, R, tmp)

            /* Calculate 2r1r2 */

            && BN_mul(r1r2x2, r1x2, r2, ctx)))

        goto err;

    /* Make positive by adding the modulus */

    if (BN_is_negative(R) && !BN_add(R, R, r1r2x2))

        goto err;

    /*

     * In FIPS 186-4 imax was set to 5 * nlen/2.

     * Analysis by Allen Roginsky (See https://csrc.nist.gov/CSRC/media/Publications/fips/186/4/final/documents/comments-received-fips186-4-december-2015.pdf

     * page 68) indicates this has a 1 in 2 million chance of failure.

     * The number has been updated to 20 * nlen/2 as used in

     * FIPS186-5 Appendix B.9 Step 9.

     */

    imax = 20 * bits; /* max = 20/2 * nbits */

    for (;;) {

        if (Xin == NULL) {

            /*

             * (Step 3) Choose Random X such that

             *    sqrt(2) * 2^(nlen/2-1) <= Random X <= (2^(nlen/2)) - 1.

             */

            if (!BN_priv_rand_range_ex(X, range, 0, ctx) || !BN_add(X, X, base))

                goto err;

        }

        /* (Step 4) Y = X + ((R - X) mod 2r1r2) */

        if (!BN_mod_sub(Y, R, X, r1r2x2, ctx) || !BN_add(Y, Y, X))

            goto err;

        /* (Step 5) */

        i = 0;

        for (;;) {

            /* (Step 6) */

            if (BN_num_bits(Y) > bits) {

                if (Xin == NULL)

                    break; /* Randomly Generated X so Go back to Step 3 */

                else

                    goto err; /* X is not random so it will always fail */

            }

            BN_GENCB_call(cb, 0, 2);

            /* (Step 7) If GCD(Y-1) == 1 & Y is probably prime then return Y */

            if (BN_copy(y1, Y) == NULL

                    || !BN_sub_word(y1, 1)

                    || !BN_gcd(tmp, y1, e, ctx))

                goto err;

            if (BN_is_one(tmp)) {

                int rv = BN_check_prime(Y, ctx, cb);

                if (rv > 0)

                    goto end;

                if (rv < 0)

                    goto err;

            }

            /* (Step 8-10) */

            if (++i >= imax) {

                ERR_raise(ERR_LIB_BN, BN_R_NO_PRIME_CANDIDATE);

                goto err;

            }

            if (!BN_add(Y, Y, r1r2x2))

                goto err;

        }

    }

end:

    ret = 1;

    BN_GENCB_call(cb, 3, 0);

err:

    BN_clear(y1);

    BN_CTX_end(ctx);

    return ret;

}