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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 "stuffer/s2n_stuffer.h"
#include "tls/s2n_connection.h"
#include "tls/s2n_tls.h"
#include "tls/s2n_tls13_handshake.h"
#include "utils/s2n_blob.h"
/* Length of the synthetic message header */
#define MESSAGE_HASH_HEADER_LENGTH 4
int s2n_conn_update_handshake_hashes(struct s2n_connection *conn, struct s2n_blob *data)
{
POSIX_ENSURE_REF(conn);
POSIX_ENSURE_REF(data);
struct s2n_handshake_hashes *hashes = conn->handshake.hashes;
POSIX_ENSURE_REF(hashes);
if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_MD5)) {
/* The handshake MD5 hash state will fail the s2n_hash_is_available() check
* since MD5 is not permitted in FIPS mode. This check will not be used as
* the handshake MD5 hash state is specifically used by the TLS 1.0 and TLS 1.1
* PRF, which is required to comply with the TLS 1.0 and 1.1 RFCs and is approved
* as per NIST Special Publication 800-52 Revision 1.
*/
POSIX_GUARD(s2n_hash_update(&hashes->md5, data->data, data->size));
}
if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA1)) {
POSIX_GUARD(s2n_hash_update(&hashes->sha1, data->data, data->size));
}
const uint8_t md5_sha1_required =
(s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_MD5)
&& s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA1));
if (md5_sha1_required) {
/* The MD5_SHA1 hash can still be used for TLS 1.0 and 1.1 in FIPS mode for
* the handshake hashes. This will only be used for the signature check in the
* CertificateVerify message and the PRF. NIST SP 800-52r1 approves use
* of MD5_SHA1 for these use cases (see footnotes 15 and 20, and section
* 3.3.2) */
POSIX_GUARD(s2n_hash_update(&hashes->md5_sha1, data->data, data->size));
}
if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA224)) {
POSIX_GUARD(s2n_hash_update(&hashes->sha224, data->data, data->size));
}
if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA256)) {
POSIX_GUARD(s2n_hash_update(&hashes->sha256, data->data, data->size));
}
if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA384)) {
POSIX_GUARD(s2n_hash_update(&hashes->sha384, data->data, data->size));
}
if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA512)) {
POSIX_GUARD(s2n_hash_update(&hashes->sha512, data->data, data->size));
}
return S2N_SUCCESS;
}
/* When a HelloRetryRequest message is used, the hash transcript needs to be recreated.
* This is done with a synthetic message header, and the hash of ClientHello1.
*
* https://tools.ietf.org/html/rfc8446#section-4.4.1
*/
int s2n_server_hello_retry_recreate_transcript(struct s2n_connection *conn)
{
POSIX_ENSURE_REF(conn);
struct s2n_handshake_hashes *hashes = conn->handshake.hashes;
POSIX_ENSURE_REF(hashes);
s2n_tls13_connection_keys(keys, conn);
uint8_t hash_digest_length = keys.size;
/* Create the MessageHash (our synthetic message) */
uint8_t msghdr[MESSAGE_HASH_HEADER_LENGTH] = { 0 };
msghdr[0] = TLS_MESSAGE_HASH;
msghdr[MESSAGE_HASH_HEADER_LENGTH - 1] = hash_digest_length;
/* Grab the current transcript hash to use as the ClientHello1 value. */
struct s2n_hash_state *client_hello1_hash = &hashes->hash_workspace;
uint8_t client_hello1_digest_out[S2N_MAX_DIGEST_LEN] = { 0 };
POSIX_GUARD_RESULT(s2n_handshake_copy_hash_state(conn, keys.hash_algorithm, client_hello1_hash));
POSIX_GUARD(s2n_hash_digest(client_hello1_hash, client_hello1_digest_out, hash_digest_length));
/* Step 1: Reset the hash state */
POSIX_GUARD_RESULT(s2n_handshake_reset_hash_state(conn, keys.hash_algorithm));
/* Step 2: Update the transcript with the synthetic message */
struct s2n_blob msg_blob = { 0 };
POSIX_GUARD(s2n_blob_init(&msg_blob, msghdr, MESSAGE_HASH_HEADER_LENGTH));
POSIX_GUARD(s2n_conn_update_handshake_hashes(conn, &msg_blob));
/* Step 3: Update the transcript with the ClientHello1 hash */
POSIX_GUARD(s2n_blob_init(&msg_blob, client_hello1_digest_out, hash_digest_length));
POSIX_GUARD(s2n_conn_update_handshake_hashes(conn, &msg_blob));
return S2N_SUCCESS;
}
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