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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 "api/s2n.h"
#include "crypto/s2n_certificate.h"
#include "error/s2n_errno.h"
#include "extensions/s2n_extension_list.h"
#include "stuffer/s2n_stuffer.h"
#include "tls/s2n_cipher_suites.h"
#include "tls/s2n_config.h"
#include "tls/s2n_connection.h"
#include "tls/s2n_signature_algorithms.h"
#include "tls/s2n_signature_scheme.h"
#include "tls/s2n_tls.h"
#include "utils/s2n_array.h"
#include "utils/s2n_safety.h"
/* RFC's that define below values:
* - https://tools.ietf.org/html/rfc5246#section-7.4.4
* - https://tools.ietf.org/search/rfc4492#section-5.5
*/
typedef enum {
S2N_CERT_TYPE_RSA_SIGN = 1,
S2N_CERT_TYPE_DSS_SIGN = 2,
S2N_CERT_TYPE_RSA_FIXED_DH = 3,
S2N_CERT_TYPE_DSS_FIXED_DH = 4,
S2N_CERT_TYPE_RSA_EPHEMERAL_DH_RESERVED = 5,
S2N_CERT_TYPE_DSS_EPHEMERAL_DH_RESERVED = 6,
S2N_CERT_TYPE_FORTEZZA_DMS_RESERVED = 20,
S2N_CERT_TYPE_ECDSA_SIGN = 64,
S2N_CERT_TYPE_RSA_FIXED_ECDH = 65,
S2N_CERT_TYPE_ECDSA_FIXED_ECDH = 66,
} s2n_cert_type;
static uint8_t s2n_cert_type_preference_list[] = {
S2N_CERT_TYPE_RSA_SIGN,
S2N_CERT_TYPE_ECDSA_SIGN
};
/*
* Include DSS sign certificate type in server certificate request.
* Only will be used if cert_req_dss_legacy_compat_enabled is set by calling
* s2n_config_enable_cert_req_dss_legacy_compat.
*/
static uint8_t s2n_cert_type_preference_list_legacy_dss[] = {
S2N_CERT_TYPE_RSA_SIGN,
S2N_CERT_TYPE_DSS_SIGN,
S2N_CERT_TYPE_ECDSA_SIGN
};
static int s2n_recv_client_cert_preferences(struct s2n_stuffer *in, s2n_cert_type *chosen_cert_type_out)
{
uint8_t cert_types_len;
POSIX_GUARD(s2n_stuffer_read_uint8(in, &cert_types_len));
uint8_t *their_cert_type_pref_list = s2n_stuffer_raw_read(in, cert_types_len);
POSIX_ENSURE_REF(their_cert_type_pref_list);
/* Iterate through our preference list from most to least preferred, and return the first match that we find. */
for (size_t our_cert_pref_idx = 0; our_cert_pref_idx < sizeof(s2n_cert_type_preference_list); our_cert_pref_idx++) {
for (int their_cert_idx = 0; their_cert_idx < cert_types_len; their_cert_idx++) {
if (their_cert_type_pref_list[their_cert_idx] == s2n_cert_type_preference_list[our_cert_pref_idx]) {
*chosen_cert_type_out = s2n_cert_type_preference_list[our_cert_pref_idx];
return 0;
}
}
}
POSIX_BAIL(S2N_ERR_CERT_TYPE_UNSUPPORTED);
}
static int s2n_set_cert_chain_as_client(struct s2n_connection *conn)
{
if (s2n_config_get_num_default_certs(conn->config) > 0) {
POSIX_GUARD(s2n_choose_sig_scheme_from_peer_preference_list(conn, &conn->handshake_params.server_sig_hash_algs,
&conn->handshake_params.client_cert_sig_scheme));
struct s2n_cert_chain_and_key *cert = s2n_config_get_single_default_cert(conn->config);
POSIX_ENSURE_REF(cert);
conn->handshake_params.our_chain_and_key = cert;
conn->handshake_params.client_cert_pkey_type = s2n_cert_chain_and_key_get_pkey_type(cert);
}
return 0;
}
int s2n_tls13_cert_req_recv(struct s2n_connection *conn)
{
struct s2n_stuffer *in = &conn->handshake.io;
/* read request context length */
uint8_t request_context_length;
POSIX_GUARD(s2n_stuffer_read_uint8(in, &request_context_length));
/* RFC 8446: This field SHALL be zero length unless used for the post-handshake authentication */
S2N_ERROR_IF(request_context_length != 0, S2N_ERR_BAD_MESSAGE);
POSIX_GUARD(s2n_extension_list_recv(S2N_EXTENSION_LIST_CERT_REQ, conn, in));
POSIX_GUARD(s2n_set_cert_chain_as_client(conn));
return S2N_SUCCESS;
}
int s2n_cert_req_recv(struct s2n_connection *conn)
{
struct s2n_stuffer *in = &conn->handshake.io;
s2n_cert_type cert_type = 0;
POSIX_GUARD(s2n_recv_client_cert_preferences(in, &cert_type));
if (conn->actual_protocol_version == S2N_TLS12) {
POSIX_GUARD(s2n_recv_supported_sig_scheme_list(in, &conn->handshake_params.server_sig_hash_algs));
}
uint16_t cert_authorities_len = 0;
POSIX_GUARD(s2n_stuffer_read_uint16(in, &cert_authorities_len));
/* For now we don't parse X.501 encoded CA Distinguished Names.
* Don't fail just yet as we still may succeed if we provide
* right certificate or if ClientAuth is optional. */
POSIX_GUARD(s2n_stuffer_skip_read(in, cert_authorities_len));
/* In the future we may have more advanced logic to match a set of configured certificates against
* The cert authorities extension and the signature algorithms advertised.
* For now, this will just set the only certificate configured.
*/
POSIX_GUARD(s2n_set_cert_chain_as_client(conn));
return 0;
}
int s2n_tls13_cert_req_send(struct s2n_connection *conn)
{
struct s2n_stuffer *out = &conn->handshake.io;
/* Write 0 length request context https://tools.ietf.org/html/rfc8446#section-4.3.2 */
POSIX_GUARD(s2n_stuffer_write_uint8(out, 0));
POSIX_GUARD(s2n_extension_list_send(S2N_EXTENSION_LIST_CERT_REQ, conn, out));
return S2N_SUCCESS;
}
int s2n_cert_req_send(struct s2n_connection *conn)
{
struct s2n_stuffer *out = &conn->handshake.io;
uint8_t client_cert_preference_list_size = sizeof(s2n_cert_type_preference_list);
if (conn->config->cert_req_dss_legacy_compat_enabled) {
client_cert_preference_list_size = sizeof(s2n_cert_type_preference_list_legacy_dss);
}
POSIX_GUARD(s2n_stuffer_write_uint8(out, client_cert_preference_list_size));
for (int i = 0; i < client_cert_preference_list_size; i++) {
if (conn->config->cert_req_dss_legacy_compat_enabled) {
POSIX_GUARD(s2n_stuffer_write_uint8(out, s2n_cert_type_preference_list_legacy_dss[i]));
} else {
POSIX_GUARD(s2n_stuffer_write_uint8(out, s2n_cert_type_preference_list[i]));
}
}
if (conn->actual_protocol_version == S2N_TLS12) {
POSIX_GUARD(s2n_send_supported_sig_scheme_list(conn, out));
}
/* RFC 5246 7.4.4 - If the certificate_authorities list is empty, then the
* client MAY send any certificate of the appropriate ClientCertificateType */
uint16_t acceptable_cert_authorities_len = 0;
POSIX_GUARD(s2n_stuffer_write_uint16(out, acceptable_cert_authorities_len));
return 0;
}
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