/*

 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the OpenSSL license (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

 */

#include <stdio.h>

#include <time.h>

#include "internal/cryptlib.h"

#include <openssl/bn.h>

#include "rsa_locl.h"

static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,

                              BN_GENCB *cb);

/*

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

                                 BIGNUM *e_value, BN_GENCB *cb)

{

    /* 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;

    }

    return rsa_builtin_keygen(rsa, bits, primes, e_value, cb);

}

static int rsa_builtin_keygen(RSA *rsa, int bits, int primes, BIGNUM *e_value,

                              BN_GENCB *cb)

{

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

    int ok = -1, 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;

    BN_CTX *ctx = NULL;

    BN_ULONG bitst = 0;

    unsigned long error = 0;

    if (bits < RSA_MIN_MODULUS_BITS) {

        ok = 0;             /* we set our own err */

        RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_SIZE_TOO_SMALL);

        goto err;

    }

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

        ok = 0;             /* we set our own err */

        RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, RSA_R_KEY_PRIME_NUM_INVALID);

        goto err;

    }

    ctx = BN_CTX_new();

    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;

    /* 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;

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

        goto err;

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

        goto err;

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

        goto err;

    if (!rsa->dmp1 && ((rsa->dmp1 = BN_secure_new()) == NULL))

        goto err;

    if (!rsa->dmq1 && ((rsa->dmq1 = BN_secure_new()) == NULL))

        goto err;

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

        goto err;

    /* 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, rsa_multip_info_free);

        }

        rsa->prime_infos = prime_infos;

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

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

            pinfo = 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_ex(prime, bitsr[i] + adj, 0, NULL, NULL, cb))

                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;

            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 effcient 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;

                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;

    }

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

        tmp = rsa->p;

        rsa->p = rsa->q;

        rsa->q = tmp;

    }

    /* 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;

    }

    {

        BIGNUM *pr0 = BN_new();

        if (pr0 == NULL)

            goto err;

        BN_with_flags(pr0, r0, BN_FLG_CONSTTIME);

        if (!BN_mod_inverse(rsa->d, rsa->e, pr0, ctx)) {

            BN_free(pr0);

            goto err;               /* d */

        }

        /* We MUST free pr0 before any further use of r0 */

        BN_free(pr0);

    }

    {

        BIGNUM *d = BN_new();

        if (d == NULL)

            goto err;

        BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);

        /* calculate d mod (p-1) and d mod (q - 1) */

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

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

            BN_free(d);

            goto err;

        }

        /* calculate CRT exponents */

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

            pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);

            /* pinfo->d == r_i - 1 */

            if (!BN_mod(pinfo->d, d, pinfo->d, ctx)) {

                BN_free(d);

                goto err;

            }

        }

        /* We MUST free d before any further use of rsa->d */

        BN_free(d);

    }

    {

        BIGNUM *p = BN_new();

        if (p == NULL)

            goto err;

        BN_with_flags(p, rsa->p, BN_FLG_CONSTTIME);

        /* calculate inverse of q mod p */

        if (!BN_mod_inverse(rsa->iqmp, rsa->q, p, ctx)) {

            BN_free(p);

            goto err;

        }

        /* calculate CRT coefficient for other primes */

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

            pinfo = sk_RSA_PRIME_INFO_value(prime_infos, i - 2);

            BN_with_flags(p, pinfo->r, BN_FLG_CONSTTIME);

            if (!BN_mod_inverse(pinfo->t, pinfo->pp, p, ctx)) {

                BN_free(p);

                goto err;

            }

        }

        /* We MUST free p before any further use of rsa->p */

        BN_free(p);

    }

    ok = 1;

 err:

    if (ok == -1) {

        RSAerr(RSA_F_RSA_BUILTIN_KEYGEN, ERR_LIB_BN);

        ok = 0;

    }

    if (ctx != NULL)

        BN_CTX_end(ctx);

    BN_CTX_free(ctx);

    return ok;

}