/*

 * Copyright 1995-2026 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

 */

/*

 * NB: these functions have been "upgraded", the deprecated versions (which

 * are compatibility wrappers using these functions) are in rsa_depr.c. -

 * Geoff

 */

/*

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

 * internal use.

 */

#include "internal/deprecated.h"

#include <stdio.h>

#include <time.h>

#include "internal/cryptlib.h"

#include <openssl/bn.h>

#include <openssl/self_test.h>

#include "prov/providercommon.h"

#include "rsa_local.h"

static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg);

static int rsa_keygen(OSSL_LIB_CTX *libctx, RSA *rsa, int bits, int primes,

    BIGNUM *e_value, BN_GENCB *cb, int pairwise_test,

    uint32_t a, uint32_t b);

/*

 * NB: this wrapper would normally be placed in rsa_lib.c and the static

 * implementation would probably be in rsa_eay.c. Nonetheless, is kept here

 * so that we don't introduce a new linker dependency. Eg. any application

 * that wasn't previously linking object code related to key-generation won't

 * have to now just because key-generation is part of RSA_METHOD.

 */

int RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)

{

    if (rsa->meth->rsa_keygen != NULL)

        return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);

    return RSA_generate_multi_prime_key(rsa, bits, RSA_DEFAULT_PRIME_NUM,

        e_value, cb);

}

int ossl_rsa_generate_multi_prime_key(RSA *rsa, int bits, int primes,

    BIGNUM *e_value, BN_GENCB *cb,

    uint32_t a, uint32_t b)

{

#ifndef FIPS_MODULE

    /* multi-prime is only supported with the builtin key generation */

    if (rsa->meth->rsa_multi_prime_keygen != NULL) {

        return rsa->meth->rsa_multi_prime_keygen(rsa, bits, primes,

            e_value, cb);

    } else if (rsa->meth->rsa_keygen != NULL) {

        /*

         * However, if rsa->meth implements only rsa_keygen, then we

         * have to honour it in 2-prime case and assume that it wouldn't

         * know what to do with multi-prime key generated by builtin

         * subroutine...

         */

        if (primes == 2)

            return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);

        else

            return 0;

    }

#endif /* FIPS_MODULE */

    return rsa_keygen(rsa->libctx, rsa, bits, primes, e_value, cb, 0, a, b);

}

int RSA_generate_multi_prime_key(RSA *rsa, int bits, int primes,

    BIGNUM *e, BN_GENCB *cb)

{

    return ossl_rsa_generate_multi_prime_key(rsa, bits, primes, e, cb, 0, 0);

}

DEFINE_STACK_OF(BIGNUM)

/*

 * Given input values, q, p, n, d and e, derive the exponents

 * and coefficients for each prime in this key, placing the result

 * on their respective exps and coeffs stacks

 */

#ifndef FIPS_MODULE

int ossl_rsa_multiprime_derive(RSA *rsa,

    STACK_OF(BIGNUM) *factors,

    STACK_OF(BIGNUM) *exps,

    STACK_OF(BIGNUM) *coeffs)

{

    STACK_OF(BIGNUM) *pplist = NULL, *pdlist = NULL;

    BIGNUM *factor = NULL, *newpp = NULL, *newpd = NULL;

    BIGNUM *dval = NULL, *newexp = NULL, *newcoeff = NULL;

    BIGNUM *p = NULL, *q = NULL;

    BIGNUM *dmp1 = NULL, *dmq1 = NULL, *iqmp = NULL;

    BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL;

    BN_CTX *ctx = NULL;

    BIGNUM *tmp = NULL;

    int i;

    int ret = 0;

    ctx = BN_CTX_new_ex(rsa->libctx);

    if (ctx == NULL)

        goto err;

    BN_CTX_start(ctx);

    pplist = sk_BIGNUM_new_null();

    if (pplist == NULL)

        goto err;

    pdlist = sk_BIGNUM_new_null();

    if (pdlist == NULL)

        goto err;

    r0 = BN_CTX_get(ctx);

    r1 = BN_CTX_get(ctx);

    r2 = BN_CTX_get(ctx);

    if (r2 == NULL)

        goto err;

    BN_set_flags(r0, BN_FLG_CONSTTIME);

    BN_set_flags(r1, BN_FLG_CONSTTIME);

    BN_set_flags(r2, BN_FLG_CONSTTIME);

    if (BN_copy(r1, rsa->n) == NULL)

        goto err;

    p = sk_BIGNUM_value(factors, 0);

    q = sk_BIGNUM_value(factors, 1);

    /* Build list of partial products of primes */

    for (i = 0; i < sk_BIGNUM_num(factors); i++) {

        switch (i) {

        case 0:

            /* our first prime, p */

            if (!BN_sub(r2, p, BN_value_one()))

                goto err;

            BN_set_flags(r2, BN_FLG_CONSTTIME);

            if (BN_mod_inverse(r1, r2, rsa->e, ctx) == NULL)

                goto err;

            break;

        case 1:

            /* second prime q */

            if (!BN_mul(r1, p, q, ctx))

                goto err;

            tmp = BN_dup(r1);

            if (tmp == NULL)

                goto err;

            if (!sk_BIGNUM_insert(pplist, tmp, sk_BIGNUM_num(pplist)))

                goto err;

            tmp = NULL;

            break;

        default:

            factor = sk_BIGNUM_value(factors, i);

            /* all other primes */

            if (!BN_mul(r1, r1, factor, ctx))

                goto err;

            tmp = BN_dup(r1);

            if (tmp == NULL)

                goto err;

            if (!sk_BIGNUM_insert(pplist, tmp, sk_BIGNUM_num(pplist)))

                goto err;

            tmp = NULL;

            break;

        }

    }

    /* build list of relative d values */

    /* p -1 */

    if (!BN_sub(r1, p, BN_value_one()))

        goto err;

    if (!BN_sub(r2, q, BN_value_one()))

        goto err;

    if (!BN_mul(r0, r1, r2, ctx))

        goto err;

    for (i = 2; i < sk_BIGNUM_num(factors); i++) {

        factor = sk_BIGNUM_value(factors, i);

        dval = BN_new();

        if (dval == NULL)

            goto err;

        BN_set_flags(dval, BN_FLG_CONSTTIME);

        if (!BN_sub(dval, factor, BN_value_one()))

            goto err;

        if (!BN_mul(r0, r0, dval, ctx))

            goto err;

        if (!sk_BIGNUM_insert(pdlist, dval, sk_BIGNUM_num(pdlist)))

            goto err;

        dval = NULL;

    }

    /* Calculate dmp1, dmq1 and additional exponents */

    dmp1 = BN_secure_new();

    if (dmp1 == NULL)

        goto err;

    dmq1 = BN_secure_new();

    if (dmq1 == NULL)

        goto err;

    if (!BN_mod(dmp1, rsa->d, r1, ctx))

        goto err;

    if (!sk_BIGNUM_insert(exps, dmp1, sk_BIGNUM_num(exps)))

        goto err;

    dmp1 = NULL;

    if (!BN_mod(dmq1, rsa->d, r2, ctx))

        goto err;

    if (!sk_BIGNUM_insert(exps, dmq1, sk_BIGNUM_num(exps)))

        goto err;

    dmq1 = NULL;

    for (i = 2; i < sk_BIGNUM_num(factors); i++) {

        newpd = sk_BIGNUM_value(pdlist, i - 2);

        newexp = BN_new();

        if (newexp == NULL)

            goto err;

        if (!BN_mod(newexp, rsa->d, newpd, ctx))

            goto err;

        if (!sk_BIGNUM_insert(exps, newexp, sk_BIGNUM_num(exps)))

            goto err;

        newexp = NULL;

    }

    /* Calculate iqmp and additional coefficients */

    iqmp = BN_new();

    if (iqmp == NULL)

        goto err;

    if (BN_mod_inverse(iqmp, sk_BIGNUM_value(factors, 1),

            sk_BIGNUM_value(factors, 0), ctx)

        == NULL)

        goto err;

    if (!sk_BIGNUM_insert(coeffs, iqmp, sk_BIGNUM_num(coeffs)))

        goto err;

    iqmp = NULL;

    for (i = 2; i < sk_BIGNUM_num(factors); i++) {

        newpp = sk_BIGNUM_value(pplist, i - 2);

        newcoeff = BN_new();

        if (newcoeff == NULL)

            goto err;

        if (BN_mod_inverse(newcoeff, newpp, sk_BIGNUM_value(factors, i),

                ctx)

            == NULL)

            goto err;

        if (!sk_BIGNUM_insert(coeffs, newcoeff, sk_BIGNUM_num(coeffs)))

            goto err;

        newcoeff = NULL;

    }

    ret = 1;

err:

    BN_free(newcoeff);

    BN_free(newexp);

    BN_free(dval);

    BN_free(tmp);

    sk_BIGNUM_pop_free(pplist, BN_free);

    sk_BIGNUM_pop_free(pdlist, BN_free);

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

    BN_clear_free(dmp1);

    BN_clear_free(dmq1);

    BN_clear_free(iqmp);

    return ret;

}

static int rsa_multiprime_keygen(RSA *rsa, int bits, int primes,

    BIGNUM *e_value, BN_GENCB *cb)

{

    BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *tmp, *tmp2, *prime;

    int n = 0, bitsr[RSA_MAX_PRIME_NUM], bitse = 0;

    int i = 0, quo = 0, rmd = 0, adj = 0, retries = 0;

    RSA_PRIME_INFO *pinfo = NULL;

    STACK_OF(RSA_PRIME_INFO) *prime_infos = NULL;

    STACK_OF(BIGNUM) *factors = NULL;

    STACK_OF(BIGNUM) *exps = NULL;

    STACK_OF(BIGNUM) *coeffs = NULL;

    BN_CTX *ctx = NULL;

    BN_ULONG bitst = 0;

    unsigned long error = 0;

    int ok = -1;

    if (bits < RSA_MIN_MODULUS_BITS) {

        ERR_raise(ERR_LIB_RSA, RSA_R_KEY_SIZE_TOO_SMALL);

        return 0;

    }

    if (e_value == NULL) {

        ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);

        return 0;

    }

    /* A bad value for e can cause infinite loops */

    if (!ossl_rsa_check_public_exponent(e_value)) {

        ERR_raise(ERR_LIB_RSA, RSA_R_PUB_EXPONENT_OUT_OF_RANGE);

        return 0;

    }

    if (primes < RSA_DEFAULT_PRIME_NUM || primes > ossl_rsa_multip_cap(bits)) {

        ERR_raise(ERR_LIB_RSA, RSA_R_KEY_PRIME_NUM_INVALID);

        return 0;

    }

    factors = sk_BIGNUM_new_null();

    if (factors == NULL)

        return 0;

    exps = sk_BIGNUM_new_null();

    if (exps == NULL)

        goto err;

    coeffs = sk_BIGNUM_new_null();

    if (coeffs == NULL)

        goto err;

    ctx = BN_CTX_new_ex(rsa->libctx);

    if (ctx == NULL)

        goto err;

    BN_CTX_start(ctx);

    r0 = BN_CTX_get(ctx);

    r1 = BN_CTX_get(ctx);

    r2 = BN_CTX_get(ctx);

    if (r2 == NULL)

        goto err;

    /* divide bits into 'primes' pieces evenly */

    quo = bits / primes;

    rmd = bits % primes;

    for (i = 0; i < primes; i++)

        bitsr[i] = (i < rmd) ? quo + 1 : quo;

    rsa->dirty_cnt++;

    /* We need the RSA components non-NULL */

    if (!rsa->n && ((rsa->n = BN_new()) == NULL))

        goto err;

    if (!rsa->d && ((rsa->d = BN_secure_new()) == NULL))

        goto err;

    BN_set_flags(rsa->d, BN_FLG_CONSTTIME);

    if (!rsa->e && ((rsa->e = BN_new()) == NULL))

        goto err;

    if (!rsa->p && ((rsa->p = BN_secure_new()) == NULL))

        goto err;

    BN_set_flags(rsa->p, BN_FLG_CONSTTIME);

    if (!rsa->q && ((rsa->q = BN_secure_new()) == NULL))

        goto err;

    BN_set_flags(rsa->q, BN_FLG_CONSTTIME);

    /* initialize multi-prime components */

    if (primes > RSA_DEFAULT_PRIME_NUM) {

        rsa->version = RSA_ASN1_VERSION_MULTI;

        prime_infos = sk_RSA_PRIME_INFO_new_reserve(NULL, primes - 2);

        if (prime_infos == NULL)

            goto err;

        if (rsa->prime_infos != NULL) {

            /* could this happen? */

            sk_RSA_PRIME_INFO_pop_free(rsa->prime_infos,

                ossl_rsa_multip_info_free);

        }

        rsa->prime_infos = prime_infos;

        /* prime_info from 2 to |primes| -1 */

        for (i = 2; i < primes; i++) {

            pinfo = ossl_rsa_multip_info_new();

            if (pinfo == NULL)

                goto err;

            (void)sk_RSA_PRIME_INFO_push(prime_infos, pinfo);

        }

    }

    if (BN_copy(rsa->e, e_value) == NULL)

        goto err;

    /* generate p, q and other primes (if any) */

    for (i = 0; i < primes; i++) {

        adj = 0;

        retries = 0;

        if (i == 0) {

            prime = rsa->p;

        } else if (i == 1) {

            prime = rsa->q;

        } else {

            pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);

            prime = pinfo->r;

        }

        BN_set_flags(prime, BN_FLG_CONSTTIME);

        for (;;) {

        redo:

            if (!BN_generate_prime_ex2(prime, bitsr[i] + adj, 0, NULL, NULL,

                    cb, ctx))

                goto err;

            /*

             * prime should not be equal to p, q, r_3...

             * (those primes prior to this one)

             */

            {

                int j;

                for (j = 0; j < i; j++) {

                    BIGNUM *prev_prime;

                    if (j == 0)

                        prev_prime = rsa->p;

                    else if (j == 1)

                        prev_prime = rsa->q;

                    else

                        prev_prime = sk_RSA_PRIME_INFO_value(prime_infos,

                            j - 2)

                                         ->r;

                    if (!BN_cmp(prime, prev_prime)) {

                        goto redo;

                    }

                }

            }

            if (!BN_sub(r2, prime, BN_value_one()))

                goto err;

            ERR_set_mark();

            BN_set_flags(r2, BN_FLG_CONSTTIME);

            if (BN_mod_inverse(r1, r2, rsa->e, ctx) != NULL) {

                /* GCD == 1 since inverse exists */

                break;

            }

            error = ERR_peek_last_error();

            if (ERR_GET_LIB(error) == ERR_LIB_BN

                && ERR_GET_REASON(error) == BN_R_NO_INVERSE) {

                /* GCD != 1 */

                ERR_pop_to_mark();

            } else {

                goto err;

            }

            if (!BN_GENCB_call(cb, 2, n++))

                goto err;

        }

        bitse += bitsr[i];

        /* calculate n immediately to see if it's sufficient */

        if (i == 1) {

            /* we get at least 2 primes */

            if (!BN_mul(r1, rsa->p, rsa->q, ctx))

                goto err;

        } else if (i != 0) {

            /* modulus n = p * q * r_3 * r_4 ... */

            if (!BN_mul(r1, rsa->n, prime, ctx))

                goto err;

        } else {

            /* i == 0, do nothing */

            if (!BN_GENCB_call(cb, 3, i))

                goto err;

            tmp = BN_dup(prime);

            if (tmp == NULL)

                goto err;

            if (!sk_BIGNUM_insert(factors, tmp, sk_BIGNUM_num(factors))) {

                BN_clear_free(tmp);

                goto err;

            }

            continue;

        }

        /*

         * if |r1|, product of factors so far, is not as long as expected

         * (by checking the first 4 bits are less than 0x9 or greater than

         * 0xF). If so, re-generate the last prime.

         *

         * NOTE: This actually can't happen in two-prime case, because of

         * the way factors are generated.

         *

         * Besides, another consideration is, for multi-prime case, even the

         * length modulus is as long as expected, the modulus could start at

         * 0x8, which could be utilized to distinguish a multi-prime private

         * key by using the modulus in a certificate. This is also covered

         * by checking the length should not be less than 0x9.

         */

        if (!BN_rshift(r2, r1, bitse - 4))

            goto err;

        bitst = BN_get_word(r2);

        if (bitst < 0x9 || bitst > 0xF) {

            /*

             * For keys with more than 4 primes, we attempt longer factor to

             * meet length requirement.

             *

             * Otherwise, we just re-generate the prime with the same length.

             *

             * This strategy has the following goals:

             *

             * 1. 1024-bit factors are efficient when using 3072 and 4096-bit key

             * 2. stay the same logic with normal 2-prime key

             */

            bitse -= bitsr[i];

            if (!BN_GENCB_call(cb, 2, n++))

                goto err;

            if (primes > 4) {

                if (bitst < 0x9)

                    adj++;

                else

                    adj--;

            } else if (retries == 4) {

                /*

                 * re-generate all primes from scratch, mainly used

                 * in 4 prime case to avoid long loop. Max retry times

                 * is set to 4.

                 */

                i = -1;

                bitse = 0;

                sk_BIGNUM_pop_free(factors, BN_clear_free);

                factors = sk_BIGNUM_new_null();

                if (factors == NULL)

                    goto err;

                continue;

            }

            retries++;

            goto redo;

        }

        /* save product of primes for further use, for multi-prime only */

        if (i > 1 && BN_copy(pinfo->pp, rsa->n) == NULL)

            goto err;

        if (BN_copy(rsa->n, r1) == NULL)

            goto err;

        if (!BN_GENCB_call(cb, 3, i))

            goto err;

        tmp = BN_dup(prime);

        if (tmp == NULL)

            goto err;

        if (!sk_BIGNUM_insert(factors, tmp, sk_BIGNUM_num(factors))) {

            BN_clear_free(tmp);

            goto err;

        }

    }

    if (BN_cmp(rsa->p, rsa->q) < 0) {

        tmp = rsa->p;

        rsa->p = rsa->q;

        rsa->q = tmp;

        /* mirror this in our factor stack */

        tmp = sk_BIGNUM_delete(factors, 0);

        if (!sk_BIGNUM_insert(factors, tmp, 1)) {

            /* the factor is no longer on the stack, so free it here */

            BN_clear_free(tmp);

            goto err;

        }

    }

    /* calculate d */

    /* p - 1 */

    if (!BN_sub(r1, rsa->p, BN_value_one()))

        goto err;

    /* q - 1 */

    if (!BN_sub(r2, rsa->q, BN_value_one()))

        goto err;

    /* (p - 1)(q - 1) */

    if (!BN_mul(r0, r1, r2, ctx))

        goto err;

    /* multi-prime */

    for (i = 2; i < primes; i++) {

        pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);

        /* save r_i - 1 to pinfo->d temporarily */

        if (!BN_sub(pinfo->d, pinfo->r, BN_value_one()))

            goto err;

        if (!BN_mul(r0, r0, pinfo->d, ctx))

            goto err;

    }

    BN_set_flags(r0, BN_FLG_CONSTTIME);

    if (BN_mod_inverse(rsa->d, rsa->e, r0, ctx) == NULL) {

        goto err; /* d */

    }

    /* derive any missing exponents and coefficients */

    if (!ossl_rsa_multiprime_derive(rsa, factors, exps, coeffs))

        goto err;

    /*

     * first 2 factors/exps are already tracked in p/q/dmq1/dmp1

     * and the first coeff is in iqmp, so pop those off the stack

     * Note, the first 2 factors/exponents are already tracked by p and q

     * assign dmp1/dmq1 and iqmp

     * the remaining pinfo values are separately allocated, so copy and delete

     * those

     */

    BN_clear_free(sk_BIGNUM_delete(factors, 0));

    BN_clear_free(sk_BIGNUM_delete(factors, 0));

    rsa->dmp1 = sk_BIGNUM_delete(exps, 0);

    rsa->dmq1 = sk_BIGNUM_delete(exps, 0);

    rsa->iqmp = sk_BIGNUM_delete(coeffs, 0);

    for (i = 2; i < primes; i++) {

        pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);

        tmp = sk_BIGNUM_delete(factors, 0);

        BN_copy(pinfo->r, tmp);

        BN_clear_free(tmp);

        tmp = sk_BIGNUM_delete(exps, 0);

        tmp2 = BN_copy(pinfo->d, tmp);

        BN_clear_free(tmp);

        if (tmp2 == NULL)

            goto err;

        tmp = sk_BIGNUM_delete(coeffs, 0);

        tmp2 = BN_copy(pinfo->t, tmp);

        BN_clear_free(tmp);

        if (tmp2 == NULL)

            goto err;

    }

    ok = 1;

err:

    /* On error, these stacks may still contain BIGNUMs. */

    sk_BIGNUM_pop_free(factors, BN_clear_free);

    sk_BIGNUM_pop_free(exps, BN_clear_free);

    sk_BIGNUM_pop_free(coeffs, BN_clear_free);

    if (ok == -1) {

        ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);

        ok = 0;

    }

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

    return ok;

}

#endif /* FIPS_MODULE */

static int rsa_keygen(OSSL_LIB_CTX *libctx, RSA *rsa, int bits, int primes,

    BIGNUM *e_value, BN_GENCB *cb, int pairwise_test,

    uint32_t a, uint32_t b)

{

    int ok = 0;

#ifdef FIPS_MODULE

    ok = ossl_rsa_sp800_56b_generate_key(rsa, bits, e_value, cb, a, b);

    pairwise_test = 1; /* FIPS MODE needs to always run the pairwise test */

#else

    /*

     * Only multi-prime keys or insecure keys with a small key length or a

     * public exponent <= 2^16 will use the older rsa_multiprime_keygen().

     */

    if (primes == 2

        && bits >= 2048

        && (e_value == NULL || BN_num_bits(e_value) > 16))

        ok = ossl_rsa_sp800_56b_generate_key(rsa, bits, e_value, cb, a, b);

    else

        ok = rsa_multiprime_keygen(rsa, bits, primes, e_value, cb);

#endif /* FIPS_MODULE */

    if (pairwise_test && ok > 0) {

        OSSL_CALLBACK *stcb = NULL;

        void *stcbarg = NULL;

        OSSL_SELF_TEST_get_callback(libctx, &stcb, &stcbarg);

        ok = rsa_keygen_pairwise_test(rsa, stcb, stcbarg);

        if (!ok) {

            /* Clear intermediate results */

            BN_clear_free(rsa->d);

            BN_clear_free(rsa->p);

            BN_clear_free(rsa->q);

            BN_clear_free(rsa->dmp1);

            BN_clear_free(rsa->dmq1);

            BN_clear_free(rsa->iqmp);

            rsa->d = NULL;

            rsa->p = NULL;

            rsa->q = NULL;

            rsa->dmp1 = NULL;

            rsa->dmq1 = NULL;

            rsa->iqmp = NULL;

        }

    }

    return ok;

}

/*

 * AS10.35 (and its VEs/TEs) of the FIPS 140-3 standard requires a PCT for every

 * generated key pair. There are 3 options:

 * 1) If the key pair is to be used for key transport (asymmetric cipher), the

 *    PCT consists of encrypting a plaintext, verifying that the result

 *    (ciphertext) is not equal to the plaintext, decrypting the ciphertext, and

 *    verifying that the result is equal to the plaintext.

 * 2) If the key pair is to be used for digital signatures, the PCT consists of

 *    computing and verifying a signature.

 * 3) If the key pair is to be used for key agreement, the exact PCT is defined

 *    in the applicable standards. For RSA-based schemes, this is defined in

 *    SP 800-56Br2 (Section 6.4.1.1) as:

 *    "The owner shall perform a pair-wise consistency test by verifying that m

 *    = (m^e)^d mod n for some integer m satisfying 1 < m < (n - 1)."

 *

 * OpenSSL implements all three use cases: RSA-OAEP for key transport,

 * RSA signatures with PKCS#1 v1.5 or PSS padding, and KAS-IFC-SSC (KAS1/KAS2)

 * using RSASVE.

 *

 * According to FIPS 140-3 IG 10.3.A, if at the time when the PCT is performed

 * the keys' intended usage is not known, then any of the three PCTs described

 * in AS10.35 shall be performed on this key pair.

 *

 * Because of this allowance from the IG, the simplest option is 3, i.e.

 * RSA_public_encrypt() and RSA_private_decrypt() with RSA_NO_PADDING.

 */

static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg)

{

    int ret = 0;

    unsigned char *plaintxt = NULL;

    unsigned char *ciphertxt = NULL;

    unsigned char *decoded = NULL;

    int plaintxt_len;

    int ciphertxt_len;

    int decoded_len;

    int padding = RSA_NO_PADDING;

    OSSL_SELF_TEST *st = NULL;

    st = OSSL_SELF_TEST_new(cb, cbarg);

    if (st == NULL)

        goto err;

    OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT,

        OSSL_SELF_TEST_DESC_PCT_RSA);

    /*

     * For RSA_NO_PADDING, RSA_public_encrypt() and RSA_private_decrypt()

     * require the 'to' and 'from' parameters to have equal length and a

     * maximum of RSA_size() - allocate space for plaintxt, ciphertxt, and

     * decoded.

     */

    plaintxt_len = RSA_size(rsa);

    plaintxt = OPENSSL_calloc(plaintxt_len, 3);

    if (plaintxt == NULL)

        goto err;

    ciphertxt = plaintxt + plaintxt_len;

    decoded = ciphertxt + plaintxt_len;

    /* SP 800-56Br2 Section 6.4.1.1 requires that plaintext is greater than 1 */

    plaintxt[plaintxt_len - 1] = 2;

    ciphertxt_len = RSA_public_encrypt(plaintxt_len, plaintxt, ciphertxt, rsa,

        padding);

    if (ciphertxt_len <= 0)

        goto err;

    OSSL_SELF_TEST_oncorrupt_byte(st, ciphertxt);

    decoded_len = RSA_private_decrypt(ciphertxt_len, ciphertxt, decoded, rsa,

        padding);

    if (decoded_len != plaintxt_len

        || memcmp(decoded, plaintxt, decoded_len) != 0)

        goto err;

    ret = 1;

err:

    OSSL_SELF_TEST_onend(st, ret);

    OSSL_SELF_TEST_free(st);

    OPENSSL_free(plaintxt);

    return ret;

}