/*
* Copyright 1995-2019 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_local.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 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;
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;
}
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ok;
}
