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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.
*/
/**
* This module implements key logging as defined by the NSS Key Log Format
*
* See https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format
*
* This key log file is a series of lines. Comment lines begin with a sharp
* character ('#') and are ignored. Secrets follow the format
* <Label> <space> <ClientRandom> <space> <Secret> where:
*
* <Label> describes the following secret.
* <ClientRandom> is 32 bytes Random value from the Client Hello message, encoded as 64 hexadecimal characters.
* <Secret> depends on the Label (see below).
*
* The following labels are defined, followed by a description of the secret:
*
* RSA: 48 bytes for the premaster secret, encoded as 96 hexadecimal characters (removed in NSS 3.34)
* CLIENT_RANDOM: 48 bytes for the master secret, encoded as 96 hexadecimal characters (for SSL 3.0, TLS 1.0, 1.1 and 1.2)
* CLIENT_EARLY_TRAFFIC_SECRET: the hex-encoded early traffic secret for the client side (for TLS 1.3)
* CLIENT_HANDSHAKE_TRAFFIC_SECRET: the hex-encoded handshake traffic secret for the client side (for TLS 1.3)
* SERVER_HANDSHAKE_TRAFFIC_SECRET: the hex-encoded handshake traffic secret for the server side (for TLS 1.3)
* CLIENT_TRAFFIC_SECRET_0: the first hex-encoded application traffic secret for the client side (for TLS 1.3)
* SERVER_TRAFFIC_SECRET_0: the first hex-encoded application traffic secret for the server side (for TLS 1.3)
* EARLY_EXPORTER_SECRET: the hex-encoded early exporter secret (for TLS 1.3).
* EXPORTER_SECRET: the hex-encoded exporter secret (for TLS 1.3)
*/
#include "api/s2n.h"
#include "tls/s2n_config.h"
#include "tls/s2n_connection.h"
#include "tls/s2n_crypto_constants.h"
#include "tls/s2n_quic_support.h" /* this currently holds the s2n_secret_type_t enum */
#include "utils/s2n_blob.h"
#include "utils/s2n_safety.h"
/* hex requires 2 chars per byte */
#define HEX_ENCODING_SIZE 2
S2N_RESULT s2n_key_log_hex_encode(struct s2n_stuffer *output, uint8_t *bytes, size_t len)
{
RESULT_ENSURE_MUT(output);
RESULT_ENSURE_REF(bytes);
const uint8_t chars[] = "0123456789abcdef";
for (size_t i = 0; i < len; i++) {
uint8_t upper = bytes[i] >> 4;
uint8_t lower = bytes[i] & 0x0f;
RESULT_GUARD_POSIX(s2n_stuffer_write_uint8(output, chars[upper]));
RESULT_GUARD_POSIX(s2n_stuffer_write_uint8(output, chars[lower]));
}
return S2N_RESULT_OK;
}
S2N_RESULT s2n_key_log_tls13_secret(struct s2n_connection *conn, const struct s2n_blob *secret, s2n_secret_type_t secret_type)
{
RESULT_ENSURE_REF(conn);
RESULT_ENSURE_REF(conn->config);
RESULT_ENSURE_REF(secret);
/* only emit keys if the callback has been set */
if (!conn->config->key_log_cb) {
return S2N_RESULT_OK;
}
const uint8_t client_early_traffic_label[] = "CLIENT_EARLY_TRAFFIC_SECRET ";
const uint8_t client_handshake_label[] = "CLIENT_HANDSHAKE_TRAFFIC_SECRET ";
const uint8_t server_handshake_label[] = "SERVER_HANDSHAKE_TRAFFIC_SECRET ";
const uint8_t client_traffic_label[] = "CLIENT_TRAFFIC_SECRET_0 ";
const uint8_t server_traffic_label[] = "SERVER_TRAFFIC_SECRET_0 ";
const uint8_t exporter_secret_label[] = "EXPORTER_SECRET ";
const uint8_t *label = NULL;
uint8_t label_size = 0;
switch (secret_type) {
case S2N_CLIENT_EARLY_TRAFFIC_SECRET:
label = client_early_traffic_label;
label_size = sizeof(client_early_traffic_label) - 1;
break;
case S2N_CLIENT_HANDSHAKE_TRAFFIC_SECRET:
label = client_handshake_label;
label_size = sizeof(client_handshake_label) - 1;
break;
case S2N_SERVER_HANDSHAKE_TRAFFIC_SECRET:
label = server_handshake_label;
label_size = sizeof(server_handshake_label) - 1;
break;
case S2N_CLIENT_APPLICATION_TRAFFIC_SECRET:
label = client_traffic_label;
label_size = sizeof(client_traffic_label) - 1;
break;
case S2N_SERVER_APPLICATION_TRAFFIC_SECRET:
label = server_traffic_label;
label_size = sizeof(server_traffic_label) - 1;
break;
case S2N_EXPORTER_SECRET:
label = exporter_secret_label;
label_size = sizeof(exporter_secret_label) - 1;
break;
default:
/* Ignore the secret types we don't understand */
return S2N_RESULT_OK;
}
const uint8_t len = label_size
+ S2N_TLS_RANDOM_DATA_LEN * HEX_ENCODING_SIZE
+ 1 /* SPACE */
+ secret->size * HEX_ENCODING_SIZE;
DEFER_CLEANUP(struct s2n_stuffer output, s2n_stuffer_free);
RESULT_GUARD_POSIX(s2n_stuffer_alloc(&output, len));
RESULT_GUARD_POSIX(s2n_stuffer_write_bytes(&output, label, label_size));
RESULT_GUARD(s2n_key_log_hex_encode(&output, conn->handshake_params.client_random, S2N_TLS_RANDOM_DATA_LEN));
RESULT_GUARD_POSIX(s2n_stuffer_write_uint8(&output, ' '));
RESULT_GUARD(s2n_key_log_hex_encode(&output, secret->data, secret->size));
uint8_t *data = s2n_stuffer_raw_read(&output, len);
RESULT_ENSURE_REF(data);
conn->config->key_log_cb(conn->config->key_log_ctx, conn, data, len);
return S2N_RESULT_OK;
}
S2N_RESULT s2n_key_log_tls12_secret(struct s2n_connection *conn)
{
RESULT_ENSURE_REF(conn);
RESULT_ENSURE_REF(conn->config);
/* only emit keys if the callback has been set */
if (!conn->config->key_log_cb) {
return S2N_RESULT_OK;
}
/* CLIENT_RANDOM: 48 bytes for the master secret, encoded as 96 hexadecimal characters (for SSL 3.0, TLS 1.0, 1.1 and 1.2) */
const uint8_t label[] = "CLIENT_RANDOM ";
const uint8_t label_size = sizeof(label) - 1;
const uint8_t len = label_size
+ S2N_TLS_RANDOM_DATA_LEN * HEX_ENCODING_SIZE
+ 1 /* SPACE */
+ S2N_TLS_SECRET_LEN * HEX_ENCODING_SIZE;
DEFER_CLEANUP(struct s2n_stuffer output, s2n_stuffer_free);
RESULT_GUARD_POSIX(s2n_stuffer_alloc(&output, len));
RESULT_GUARD_POSIX(s2n_stuffer_write_bytes(&output, label, label_size));
RESULT_GUARD(s2n_key_log_hex_encode(&output, conn->handshake_params.client_random, S2N_TLS_RANDOM_DATA_LEN));
RESULT_GUARD_POSIX(s2n_stuffer_write_uint8(&output, ' '));
RESULT_GUARD(s2n_key_log_hex_encode(&output, conn->secrets.version.tls12.master_secret, S2N_TLS_SECRET_LEN));
uint8_t *data = s2n_stuffer_raw_read(&output, len);
RESULT_ENSURE_REF(data);
conn->config->key_log_cb(conn->config->key_log_ctx, conn, data, len);
return S2N_RESULT_OK;
}
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