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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
#include "crypto/s2n_dhe.h"
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/evp.h>
#include <stdint.h>
#include "crypto/s2n_openssl.h"
#include "error/s2n_errno.h"
#include "stuffer/s2n_stuffer.h"
#include "utils/s2n_blob.h"
#include "utils/s2n_mem.h"
#include "utils/s2n_safety.h"
#define S2N_MIN_DH_PRIME_SIZE_BYTES (2048 / 8)
/* Caller is not responsible for freeing values returned by these accessors
* Per https://www.openssl.org/docs/man1.1.0/crypto/DH_get0_pqg.html
*/
static const BIGNUM *s2n_get_Ys_dh_param(struct s2n_dh_params *dh_params)
{
const BIGNUM *Ys;
/* DH made opaque in Openssl 1.1.0 */
#if S2N_OPENSSL_VERSION_AT_LEAST(1, 1, 0) && !defined(LIBRESSL_VERSION_NUMBER)
DH_get0_key(dh_params->dh, &Ys, NULL);
#else
Ys = dh_params->dh->pub_key;
#endif
return Ys;
}
static const BIGNUM *s2n_get_p_dh_param(struct s2n_dh_params *dh_params)
{
const BIGNUM *p;
#if S2N_OPENSSL_VERSION_AT_LEAST(1, 1, 0) && !defined(LIBRESSL_VERSION_NUMBER)
DH_get0_pqg(dh_params->dh, &p, NULL, NULL);
#else
p = dh_params->dh->p;
#endif
return p;
}
static const BIGNUM *s2n_get_g_dh_param(struct s2n_dh_params *dh_params)
{
const BIGNUM *g;
#if S2N_OPENSSL_VERSION_AT_LEAST(1, 1, 0) && !defined(LIBRESSL_VERSION_NUMBER)
DH_get0_pqg(dh_params->dh, NULL, NULL, &g);
#else
g = dh_params->dh->g;
#endif
return g;
}
static int s2n_check_p_g_dh_params(struct s2n_dh_params *dh_params)
{
notnull_check(dh_params);
notnull_check(dh_params->dh);
const BIGNUM *p = s2n_get_p_dh_param(dh_params);
const BIGNUM *g = s2n_get_g_dh_param(dh_params);
notnull_check(g);
notnull_check(p);
S2N_ERROR_IF(DH_size(dh_params->dh) < S2N_MIN_DH_PRIME_SIZE_BYTES, S2N_ERR_DH_PARAMS_CREATE);
S2N_ERROR_IF(BN_is_zero(g), S2N_ERR_DH_PARAMS_CREATE);
S2N_ERROR_IF(BN_is_zero(p), S2N_ERR_DH_PARAMS_CREATE);
return S2N_SUCCESS;
}
static int s2n_check_pub_key_dh_params(struct s2n_dh_params *dh_params)
{
const BIGNUM *pub_key = s2n_get_Ys_dh_param(dh_params);
notnull_check(pub_key);
S2N_ERROR_IF(BN_is_zero(pub_key), S2N_ERR_DH_PARAMS_CREATE);
return S2N_SUCCESS;
}
static int s2n_set_p_g_Ys_dh_params(struct s2n_dh_params *dh_params, struct s2n_blob *p, struct s2n_blob *g,
struct s2n_blob *Ys)
{
ENSURE_POSIX(p->size <= INT_MAX, S2N_ERR_INTEGER_OVERFLOW);
ENSURE_POSIX(g->size <= INT_MAX, S2N_ERR_INTEGER_OVERFLOW);
ENSURE_POSIX(Ys->size <= INT_MAX, S2N_ERR_INTEGER_OVERFLOW);
BIGNUM *bn_p = BN_bin2bn(( const unsigned char * )p->data, p->size, NULL);
BIGNUM *bn_g = BN_bin2bn(( const unsigned char * )g->data, g->size, NULL);
BIGNUM *bn_Ys = BN_bin2bn(( const unsigned char * )Ys->data, Ys->size, NULL);
#if S2N_OPENSSL_VERSION_AT_LEAST(1, 1, 0) && !defined(LIBRESSL_VERSION_NUMBER)
/* Per https://www.openssl.org/docs/man1.1.0/crypto/DH_get0_pqg.html:
* values that have been passed in should not be freed directly after this function has been called
*/
GUARD_OSSL(DH_set0_pqg(dh_params->dh, bn_p, NULL, bn_g), S2N_ERR_DH_PARAMS_CREATE);
/* Same as DH_set0_pqg */
GUARD_OSSL(DH_set0_key(dh_params->dh, bn_Ys, NULL), S2N_ERR_DH_PARAMS_CREATE);
#else
dh_params->dh->p = bn_p;
dh_params->dh->g = bn_g;
dh_params->dh->pub_key = bn_Ys;
#endif
return S2N_SUCCESS;
}
int s2n_check_all_dh_params(struct s2n_dh_params *dh_params)
{
GUARD(s2n_check_p_g_dh_params(dh_params));
GUARD(s2n_check_pub_key_dh_params(dh_params));
return S2N_SUCCESS;
}
int s2n_pkcs3_to_dh_params(struct s2n_dh_params *dh_params, struct s2n_blob *pkcs3)
{
notnull_check(dh_params);
PRECONDITION_POSIX(s2n_blob_validate(pkcs3));
uint8_t *original_ptr = pkcs3->data;
dh_params->dh = d2i_DHparams(NULL, ( const unsigned char ** )( void * )&pkcs3->data, pkcs3->size);
GUARD(s2n_check_p_g_dh_params(dh_params));
if (pkcs3->data - original_ptr != pkcs3->size) {
DH_free(dh_params->dh);
S2N_ERROR(S2N_ERR_INVALID_PKCS3);
}
pkcs3->data = original_ptr;
/* Require at least 2048 bits for the DH size */
if (DH_size(dh_params->dh) < S2N_MIN_DH_PRIME_SIZE_BYTES) {
DH_free(dh_params->dh);
S2N_ERROR(S2N_ERR_DH_TOO_SMALL);
}
/* Check the generator and prime */
GUARD(s2n_dh_params_check(dh_params));
return S2N_SUCCESS;
}
int s2n_dh_p_g_Ys_to_dh_params(struct s2n_dh_params *server_dh_params, struct s2n_blob *p, struct s2n_blob *g,
struct s2n_blob *Ys)
{
ENSURE_POSIX_REF(server_dh_params);
PRECONDITION_POSIX(s2n_blob_validate(p));
PRECONDITION_POSIX(s2n_blob_validate(g));
PRECONDITION_POSIX(s2n_blob_validate(Ys));
server_dh_params->dh = DH_new();
ENSURE_POSIX(server_dh_params->dh != NULL, S2N_ERR_DH_PARAMS_CREATE);
GUARD(s2n_set_p_g_Ys_dh_params(server_dh_params, p, g, Ys));
GUARD(s2n_check_all_dh_params(server_dh_params));
return S2N_SUCCESS;
}
int s2n_dh_params_to_p_g_Ys(struct s2n_dh_params *server_dh_params, struct s2n_stuffer *out, struct s2n_blob *output)
{
GUARD(s2n_check_all_dh_params(server_dh_params));
PRECONDITION_POSIX(s2n_stuffer_validate(out));
PRECONDITION_POSIX(s2n_blob_validate(output));
const BIGNUM *bn_p = s2n_get_p_dh_param(server_dh_params);
const BIGNUM *bn_g = s2n_get_g_dh_param(server_dh_params);
const BIGNUM *bn_Ys = s2n_get_Ys_dh_param(server_dh_params);
uint16_t p_size = BN_num_bytes(bn_p);
uint16_t g_size = BN_num_bytes(bn_g);
uint16_t Ys_size = BN_num_bytes(bn_Ys);
uint8_t *p = NULL;
uint8_t *g = NULL;
uint8_t *Ys = NULL;
output->data = s2n_stuffer_raw_write(out, 0);
notnull_check(output->data);
GUARD(s2n_stuffer_write_uint16(out, p_size));
p = s2n_stuffer_raw_write(out, p_size);
notnull_check(p);
ENSURE_POSIX(BN_bn2bin(bn_p, p) == p_size, S2N_ERR_DH_SERIALIZING);
GUARD(s2n_stuffer_write_uint16(out, g_size));
g = s2n_stuffer_raw_write(out, g_size);
notnull_check(g);
ENSURE_POSIX(BN_bn2bin(bn_g, g) == g_size, S2N_ERR_DH_SERIALIZING);
GUARD(s2n_stuffer_write_uint16(out, Ys_size));
Ys = s2n_stuffer_raw_write(out, Ys_size);
notnull_check(Ys);
ENSURE_POSIX(BN_bn2bin(bn_Ys, Ys) == Ys_size, S2N_ERR_DH_SERIALIZING);
output->size = p_size + 2 + g_size + 2 + Ys_size + 2;
return S2N_SUCCESS;
}
int s2n_dh_compute_shared_secret_as_client(struct s2n_dh_params *server_dh_params, struct s2n_stuffer *Yc_out,
struct s2n_blob *shared_key)
{
struct s2n_dh_params client_params = { 0 };
uint8_t * client_pub_key = NULL;
uint16_t client_pub_key_size = 0;
int shared_key_size = 0;
GUARD(s2n_dh_params_check(server_dh_params));
GUARD(s2n_dh_params_copy(server_dh_params, &client_params));
GUARD(s2n_dh_generate_ephemeral_key(&client_params));
GUARD(s2n_alloc(shared_key, DH_size(server_dh_params->dh)));
const BIGNUM *client_pub_key_bn = s2n_get_Ys_dh_param(&client_params);
ENSURE_POSIX_REF(client_pub_key_bn);
client_pub_key_size = BN_num_bytes(client_pub_key_bn);
GUARD(s2n_stuffer_write_uint16(Yc_out, client_pub_key_size));
client_pub_key = s2n_stuffer_raw_write(Yc_out, client_pub_key_size);
if (client_pub_key == NULL) {
GUARD(s2n_free(shared_key));
GUARD(s2n_dh_params_free(&client_params));
S2N_ERROR(S2N_ERR_DH_WRITING_PUBLIC_KEY);
}
if (BN_bn2bin(client_pub_key_bn, client_pub_key) != client_pub_key_size) {
GUARD(s2n_free(shared_key));
GUARD(s2n_dh_params_free(&client_params));
S2N_ERROR(S2N_ERR_DH_COPYING_PUBLIC_KEY);
}
/* server_dh_params already validated */
const BIGNUM *server_pub_key_bn = s2n_get_Ys_dh_param(server_dh_params);
shared_key_size = DH_compute_key(shared_key->data, server_pub_key_bn, client_params.dh);
if (shared_key_size < 0) {
GUARD(s2n_free(shared_key));
GUARD(s2n_dh_params_free(&client_params));
S2N_ERROR(S2N_ERR_DH_SHARED_SECRET);
}
shared_key->size = shared_key_size;
GUARD(s2n_dh_params_free(&client_params));
return S2N_SUCCESS;
}
int s2n_dh_compute_shared_secret_as_server(struct s2n_dh_params *server_dh_params, struct s2n_stuffer *Yc_in,
struct s2n_blob *shared_key)
{
uint16_t Yc_length = 0;
struct s2n_blob Yc = { 0 };
int shared_key_size = 0;
BIGNUM * pub_key = NULL;
GUARD(s2n_check_all_dh_params(server_dh_params));
GUARD(s2n_stuffer_read_uint16(Yc_in, &Yc_length));
Yc.size = Yc_length;
Yc.data = s2n_stuffer_raw_read(Yc_in, Yc.size);
notnull_check(Yc.data);
pub_key = BN_bin2bn(( const unsigned char * )Yc.data, Yc.size, NULL);
notnull_check(pub_key);
int server_dh_params_size = DH_size(server_dh_params->dh);
ENSURE_POSIX(server_dh_params_size <= INT32_MAX, S2N_ERR_INTEGER_OVERFLOW);
GUARD(s2n_alloc(shared_key, server_dh_params_size));
shared_key_size = DH_compute_key(shared_key->data, pub_key, server_dh_params->dh);
if (shared_key_size <= 0) {
BN_free(pub_key);
S2N_ERROR(S2N_ERR_DH_SHARED_SECRET);
}
shared_key->size = shared_key_size;
BN_free(pub_key);
return S2N_SUCCESS;
}
int s2n_dh_params_check(struct s2n_dh_params *dh_params)
{
notnull_check(dh_params);
notnull_check(dh_params->dh);
int codes = 0;
GUARD_OSSL(DH_check(dh_params->dh, &codes), S2N_ERR_DH_PARAMETER_CHECK);
ENSURE_POSIX(codes == 0, S2N_ERR_DH_PARAMETER_CHECK);
return S2N_SUCCESS;
}
int s2n_dh_params_copy(struct s2n_dh_params *from, struct s2n_dh_params *to)
{
GUARD(s2n_check_p_g_dh_params(from));
notnull_check(to);
to->dh = DHparams_dup(from->dh);
ENSURE_POSIX(to->dh != NULL, S2N_ERR_DH_COPYING_PARAMETERS);
return S2N_SUCCESS;
}
int s2n_dh_generate_ephemeral_key(struct s2n_dh_params *dh_params)
{
GUARD(s2n_check_p_g_dh_params(dh_params));
GUARD_OSSL(DH_generate_key(dh_params->dh), S2N_ERR_DH_GENERATING_PARAMETERS);
return S2N_SUCCESS;
}
int s2n_dh_params_free(struct s2n_dh_params *dh_params)
{
notnull_check(dh_params);
DH_free(dh_params->dh);
dh_params->dh = NULL;
return S2N_SUCCESS;
}
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