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openssl/crypto/rsa/rsa_gen.c

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/*
* Copyright 1995-2024 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);
/*
* 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)
{
#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);
}
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, int bits, int primes,
BIGNUM *e_value,
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;
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;
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;
}
/* 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)) {
BN_free(newexp);
goto err;
}
if (!sk_BIGNUM_insert(exps, newexp, sk_BIGNUM_num(exps)))
goto err;
}
/* 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) {
BN_free(newcoeff);
goto err;
}
if (!sk_BIGNUM_insert(coeffs, newcoeff, sk_BIGNUM_num(coeffs)))
goto err;
}
ret = 1;
err:
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)))
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)))
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 */
if (!sk_BIGNUM_insert(factors, sk_BIGNUM_delete(factors, 0), 1))
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, bits, primes, e_value,
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:
sk_BIGNUM_free(factors);
sk_BIGNUM_free(exps);
sk_BIGNUM_free(coeffs);
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)
{
int ok = 0;
#ifdef FIPS_MODULE
ok = ossl_rsa_sp800_56b_generate_key(rsa, bits, e_value, cb);
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);
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) {
ossl_set_error_state(OSSL_SELF_TEST_TYPE_PCT);
/* 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;
}
/*
* For RSA key generation it is not known whether the key pair will be used
* for key transport or signatures. FIPS 140-2 IG 9.9 states that in this case
* either a signature verification OR an encryption operation may be used to
* perform the pairwise consistency check. The simpler encrypt/decrypt operation
* has been chosen for this case.
*/
static int rsa_keygen_pairwise_test(RSA *rsa, OSSL_CALLBACK *cb, void *cbarg)
{
int ret = 0;
unsigned int ciphertxt_len;
unsigned char *ciphertxt = NULL;
const unsigned char plaintxt[16] = {0};
unsigned char *decoded = NULL;
unsigned int decoded_len;
unsigned int plaintxt_len = (unsigned int)sizeof(plaintxt_len);
int padding = RSA_PKCS1_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_PKCS1);
ciphertxt_len = RSA_size(rsa);
/*
* RSA_private_encrypt() and RSA_private_decrypt() requires the 'to'
* parameter to be a maximum of RSA_size() - allocate space for both.
*/
ciphertxt = OPENSSL_zalloc(ciphertxt_len * 2);
if (ciphertxt == NULL)
goto err;
decoded = ciphertxt + ciphertxt_len;
ciphertxt_len = RSA_public_encrypt(plaintxt_len, plaintxt, ciphertxt, rsa,
padding);
if (ciphertxt_len <= 0)
goto err;
if (ciphertxt_len == plaintxt_len
&& memcmp(ciphertxt, plaintxt, plaintxt_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(ciphertxt);
return ret;
}
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