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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Secure Component */
/** */
/** Transport Layer Security (TLS) - Generate Session Keys */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_tls.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_tls_session_keys_set PORTABLE C */
/* 6.1.8 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function sets the session keys for a TLS session following the */
/* sending or receiving of a ChangeCipherSpec message. In */
/* renegotiation handshakes, two separate set of session keys will be */
/* in use simultaneously so we need this to be able to separate which */
/* keys are actually in use. */
/* */
/* Once the keys are set, this function initializes the appropriate */
/* session cipher with the new key set. */
/* */
/* INPUT */
/* */
/* tls_session TLS control block */
/* key_set Remote or local keys */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* [nx_crypto_init] Initialize crypto */
/* */
/* CALLED BY */
/* */
/* _nx_secure_dtls_client_handshake DTLS client state machine */
/* _nx_secure_dtls_server_handshake DTLS server state machine */
/* _nx_secure_tls_client_handshake TLS client state machine */
/* _nx_secure_tls_server_handshake TLS server state machine */
/* _nx_secure_tls_process_changecipherspec */
/* Process ChangeCipherSpec */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Timothy Stapko Initial Version 6.0 */
/* 09-30-2020 Timothy Stapko Modified comment(s), */
/* verified memcpy use cases, */
/* resulting in version 6.1 */
/* 08-02-2021 Timothy Stapko Modified comment(s), added */
/* cleanup for session cipher, */
/* resulting in version 6.1.8 */
/* */
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
UINT _nx_secure_tls_session_keys_set(NX_SECURE_TLS_SESSION *tls_session, USHORT key_set)
{
UINT status;
UCHAR *key_block; /* Maximum ciphersuite key size - AES_256_CBC_SHA, 2x32 byte keys + 2x20 byte MAC secrets + 2x16 IVs. */
UINT key_size;
UINT hash_size;
UINT iv_size;
UINT key_offset;
UINT is_client;
const NX_CRYPTO_METHOD *session_cipher_method = NX_NULL;
/* The key material should have already been generated by nx_secure_tls_generate_keys once all
* key generation data was available. This simply switches the appropriate key data over to the active
* key block */
if (key_set == NX_SECURE_TLS_KEY_SET_LOCAL)
{
tls_session -> nx_secure_tls_local_session_active = 1;
}
else
{
tls_session -> nx_secure_tls_remote_session_active = 1;
}
/* Working pointers into our key material blocks. */
key_block = tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data;
/* See if we are setting server or client keys. */
if ((key_set == NX_SECURE_TLS_KEY_SET_REMOTE && tls_session -> nx_secure_tls_socket_type == NX_SECURE_TLS_SESSION_TYPE_CLIENT) ||
(key_set == NX_SECURE_TLS_KEY_SET_LOCAL && tls_session -> nx_secure_tls_socket_type == NX_SECURE_TLS_SESSION_TYPE_SERVER))
{
/* Setting remote keys for a client or local keys for a server: we are setting server keys. */
is_client = NX_FALSE;
}
else
{
/* Local client/local keys or local server/remote keys. */
is_client = NX_TRUE;
}
if (tls_session -> nx_secure_tls_session_ciphersuite == NX_NULL)
{
/* Likely internal error since at this point ciphersuite negotiation was theoretically completed. */
return(NX_SECURE_TLS_UNKNOWN_CIPHERSUITE);
}
/* Get our session cipher method so we can get key sizes. */
session_cipher_method = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_session_cipher;
/* Lookup ciphersuite data for key size. We need 2 keys for each session. */
key_size = session_cipher_method -> nx_crypto_key_size_in_bits >> 3;
/* Lookup ciphersuite data for hash size - used for the MAC secret. */
hash_size = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_hash_size;
/* Lookup initialization vector size. */
iv_size = session_cipher_method -> nx_crypto_IV_size_in_bits >> 3;
/* Partition the key block into our keys and secrets following the TLS spec.*/
key_offset = 0;
if (((hash_size + key_size + iv_size) << 1) > sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data))
{
/* No space for key material data. */
return(NX_SECURE_TLS_CRYPTO_KEYS_TOO_LARGE);
}
/* First, the mac secrets. Check for non-zero in the (unlikely) event we are using a NULL hash. */
if (hash_size > 0)
{
/* Copy new client mac secret over if setting client keys. */
if (is_client)
{
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data[key_offset],
&tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[key_offset], hash_size); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_client_write_mac_secret = &key_block[key_offset];
key_offset += hash_size;
/* Copy new server mac secret if setting server keys. */
if (!is_client)
{
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data[key_offset],
&tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[key_offset], hash_size); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_write_mac_secret = &key_block[key_offset];
key_offset += hash_size;
}
/* Now the keys. Check for non-zero size in the event we are using a NULL cipher (usually for debugging). */
if (key_size > 0)
{
/* Copy new client session key if setting client keys. */
if (is_client)
{
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data[key_offset],
&tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[key_offset], key_size); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_client_write_key = &key_block[key_offset];
key_offset += key_size;
/* Copy new server session key if setting server keys. */
if (!is_client)
{
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data[key_offset],
&tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[key_offset], key_size); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_write_key = &key_block[key_offset];
key_offset += key_size;
}
/* Finally, the IVs. Many ciphers don't use IV's so the iv_size is often zero. */
if (iv_size > 0)
{
/* Copy new client IV if setting client keys. */
if (is_client)
{
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data[key_offset],
&tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[key_offset], iv_size); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_client_iv = &key_block[key_offset];
key_offset += iv_size;
/* Copy new server IV if setting server keys. */
if (!is_client)
{
NX_SECURE_MEMCPY(&tls_session -> nx_secure_tls_key_material.nx_secure_tls_key_material_data[key_offset],
&tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[key_offset], iv_size); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_iv = &key_block[key_offset];
key_offset += iv_size;
}
/* Initialize the crypto method used in the session cipher. */
if (session_cipher_method -> nx_crypto_init != NULL)
{
/* Set client write key. */
if (is_client)
{
if (tls_session -> nx_secure_tls_session_cipher_client_initialized && session_cipher_method -> nx_crypto_cleanup)
{
status = session_cipher_method -> nx_crypto_cleanup(tls_session -> nx_secure_session_cipher_metadata_area_client);
if (status != NX_CRYPTO_SUCCESS)
{
return(status);
}
tls_session -> nx_secure_tls_session_cipher_client_initialized = 0;
}
status = session_cipher_method -> nx_crypto_init((NX_CRYPTO_METHOD*)session_cipher_method,
tls_session -> nx_secure_tls_key_material.nx_secure_tls_client_write_key,
session_cipher_method -> nx_crypto_key_size_in_bits,
&tls_session -> nx_secure_session_cipher_handler_client,
tls_session -> nx_secure_session_cipher_metadata_area_client,
tls_session -> nx_secure_session_cipher_metadata_size);
tls_session -> nx_secure_tls_session_cipher_client_initialized = 1;
}
else
{
if (tls_session -> nx_secure_tls_session_cipher_server_initialized && session_cipher_method -> nx_crypto_cleanup)
{
status = session_cipher_method -> nx_crypto_cleanup(tls_session -> nx_secure_session_cipher_metadata_area_server);
if (status != NX_CRYPTO_SUCCESS)
{
return(status);
}
tls_session -> nx_secure_tls_session_cipher_server_initialized = 0;
}
/* Set server write key. */
status = session_cipher_method -> nx_crypto_init((NX_CRYPTO_METHOD*)session_cipher_method,
tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_write_key,
session_cipher_method -> nx_crypto_key_size_in_bits,
&tls_session -> nx_secure_session_cipher_handler_server,
tls_session -> nx_secure_session_cipher_metadata_area_server,
tls_session -> nx_secure_session_cipher_metadata_size);
tls_session -> nx_secure_tls_session_cipher_server_initialized = 1;
}
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
return(NX_SECURE_TLS_SUCCESS);
}