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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 "tls/s2n_renegotiate.h"
#include "error/s2n_errno.h"
#include "stuffer/s2n_stuffer.h"
#include "tls/s2n_connection.h"
#include "utils/s2n_safety.h"
/* We don't want to introduce a new blocked status for renegotiation
* because that would potentially require applications to update their
* blocked status handling logic for no reason.
*
* It is impossible to use both early data and renegotiation for the same handshake,
* and both are just application data received during the handshake.
* Therefore, we will alias S2N_BLOCKED_ON_EARLY_DATA for reuse with renegotiation.
*/
const s2n_blocked_status S2N_BLOCKED_ON_APPLICATION_DATA = S2N_BLOCKED_ON_EARLY_DATA;
S2N_RESULT s2n_renegotiate_validate(struct s2n_connection *conn)
{
RESULT_ENSURE_REF(conn);
RESULT_ENSURE(conn->mode == S2N_CLIENT, S2N_ERR_NO_RENEGOTIATION);
RESULT_ENSURE(conn->secure_renegotiation, S2N_ERR_NO_RENEGOTIATION);
RESULT_ENSURE(conn->handshake.renegotiation, S2N_ERR_INVALID_STATE);
return S2N_RESULT_OK;
}
/*
* Prepare a connection to be reused for a second handshake.
*
* s2n-tls was not originally designed to support renegotiation.
* s2n_connection is a very large structure with configuration fields set by the application
* mixed in with internal state fields set by the handshake.
* Ensuring all existing internal state fields (and any new fields added) are safe to reuse for
* a renegotiated handshake would be extremely prone to errors.
* For safety, we instead wipe the entire connection and only restore fields we know we need
* in order to continue sending and receiving encrypted data.
*
* Any configuration fields set by the application will need to be set by the application again.
*/
int s2n_renegotiate_wipe(struct s2n_connection *conn)
{
POSIX_ENSURE_REF(conn);
/* We use this method to reset both clients and servers when testing.
* However, outside of tests, it should only be called for client connections
* because we only support renegotiation for clients.
*/
POSIX_ENSURE(conn->mode == S2N_CLIENT || s2n_in_unit_test(), S2N_ERR_NO_RENEGOTIATION);
/* Best effort check for pending input or output data.
* This method should not be called until the application has stopped sending and receiving.
* Saving partial read or parital write state would complicate this problem.
*/
POSIX_ENSURE(s2n_stuffer_data_available(&conn->header_in) == 0, S2N_ERR_INVALID_STATE);
POSIX_ENSURE(s2n_stuffer_data_available(&conn->in) == 0, S2N_ERR_INVALID_STATE);
POSIX_ENSURE(s2n_stuffer_data_available(&conn->out) == 0, S2N_ERR_INVALID_STATE);
/* Save the crypto parameters.
* We need to continue encrypting / decrypting with the old secure parameters.
*/
DEFER_CLEANUP(struct s2n_crypto_parameters *secure_crypto_params = conn->secure,
s2n_crypto_parameters_free);
conn->secure = NULL;
/* Save the fragment length so we continue properly fragmenting our records
* until a new fragment length is chosen.
*/
uint16_t max_frag_len = conn->max_outgoing_fragment_length;
/* Save the protocol versions.
* Various checks when sending and receiving records rely on the protocol version. */
uint8_t actual_protocol_version = conn->actual_protocol_version;
uint8_t server_protocol_version = conn->server_protocol_version;
uint8_t client_protocol_version = conn->client_protocol_version;
POSIX_ENSURE(actual_protocol_version < S2N_TLS13, S2N_ERR_PROTOCOL_VERSION_UNSUPPORTED);
/* Save byte tracking.
* This isn't strictly necessary, but potentially useful. */
uint64_t wire_bytes_in = conn->wire_bytes_in;
uint64_t wire_bytes_out = conn->wire_bytes_out;
/* Save io settings */
bool send_managed = conn->managed_send_io;
s2n_send_fn *send_fn = conn->send;
void *send_ctx = conn->send_io_context;
bool recv_managed = conn->managed_recv_io;
s2n_recv_fn *recv_fn = conn->recv;
void *recv_ctx = conn->recv_io_context;
/* Treat IO as unmanaged, since we don't want to clean it up yet */
conn->managed_send_io = false;
conn->managed_recv_io = false;
/* Save the secure_renegotiation flag.
* This flag should always be true, since we don't support insecure renegotiation,
* but copying its value seems safer than just setting it to 'true'.
*/
bool secure_renegotiation = conn->secure_renegotiation;
POSIX_ENSURE(secure_renegotiation, S2N_ERR_NO_RENEGOTIATION);
/* Save the finished data.
* This is required for the renegotiate_info extension on the new handshake.
*/
uint8_t finished_len = conn->handshake.finished_len;
uint8_t client_finished[sizeof(conn->handshake.client_finished)] = { 0 };
POSIX_CHECKED_MEMCPY(client_finished, conn->handshake.client_finished, finished_len);
uint8_t server_finished[sizeof(conn->handshake.server_finished)] = { 0 };
POSIX_CHECKED_MEMCPY(server_finished, conn->handshake.server_finished, finished_len);
POSIX_GUARD(s2n_connection_wipe(conn));
/* Setup the new crypto parameters.
* The new handshake will negotiate new secure crypto parameters,
* so the current secure crypto parameters become the initial crypto parameters.
*/
POSIX_GUARD_RESULT(s2n_crypto_parameters_free(&conn->initial));
conn->initial = secure_crypto_params;
ZERO_TO_DISABLE_DEFER_CLEANUP(secure_crypto_params);
conn->client = conn->initial;
conn->server = conn->initial;
/* Restore saved values */
POSIX_GUARD_RESULT(s2n_connection_set_max_fragment_length(conn, max_frag_len));
POSIX_CHECKED_MEMCPY(conn->handshake.client_finished, client_finished, finished_len);
POSIX_CHECKED_MEMCPY(conn->handshake.server_finished, server_finished, finished_len);
conn->handshake.finished_len = finished_len;
conn->actual_protocol_version = actual_protocol_version;
conn->server_protocol_version = server_protocol_version;
conn->client_protocol_version = client_protocol_version;
conn->wire_bytes_in = wire_bytes_in;
conn->wire_bytes_out = wire_bytes_out;
conn->managed_send_io = send_managed;
conn->send = send_fn;
conn->send_io_context = send_ctx;
conn->managed_recv_io = recv_managed;
conn->recv = recv_fn;
conn->recv_io_context = recv_ctx;
conn->secure_renegotiation = secure_renegotiation;
conn->handshake.renegotiation = true;
return S2N_SUCCESS;
}
static S2N_RESULT s2n_renegotiate_read_app_data(struct s2n_connection *conn, uint8_t *app_data_buf, ssize_t app_data_buf_size,
ssize_t *app_data_size, s2n_blocked_status *blocked)
{
RESULT_ENSURE_REF(blocked);
ssize_t r = s2n_recv(conn, app_data_buf, app_data_buf_size, blocked);
RESULT_GUARD_POSIX(r);
*app_data_size = r;
*blocked = S2N_BLOCKED_ON_APPLICATION_DATA;
RESULT_BAIL(S2N_ERR_APP_DATA_BLOCKED);
}
int s2n_renegotiate(struct s2n_connection *conn, uint8_t *app_data_buf, ssize_t app_data_buf_size,
ssize_t *app_data_size, s2n_blocked_status *blocked)
{
POSIX_GUARD_RESULT(s2n_renegotiate_validate(conn));
POSIX_ENSURE_REF(app_data_size);
*app_data_size = 0;
/* If there is outstanding application data, pass it back to the application.
* We can't read the next handshake record until we drain the buffer.
*/
if (s2n_peek(conn) > 0) {
POSIX_GUARD_RESULT(s2n_renegotiate_read_app_data(conn,
app_data_buf, app_data_buf_size, app_data_size, blocked));
}
int result = s2n_negotiate(conn, blocked);
/* If we encounter application data while reading handshake records,
* pass it back to the application.
*/
if (result != S2N_SUCCESS && s2n_errno == S2N_ERR_APP_DATA_BLOCKED) {
POSIX_GUARD_RESULT(s2n_renegotiate_read_app_data(conn,
app_data_buf, app_data_buf_size, app_data_size, blocked));
}
return result;
}
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