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/***************************************************************************
* Copyright (c) 2024 Microsoft Corporation
* Copyright (c) 2025-present Eclipse ThreadX Contributors
*
* This program and the accompanying materials are made available under the
* terms of the MIT License which is available at
* https://opensource.org/licenses/MIT.
*
* SPDX-License-Identifier: MIT
**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Secure Component */
/** */
/** Transport Layer Security (TLS) - Generate Session Keys */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_tls.h"
#ifdef NX_SECURE_ENABLE_DTLS
#include "nx_secure_dtls.h"
#endif /* NX_SECURE_ENABLE_DTLS */
/* This local static buffer needs to be large enough to hold both the server random and the client random. */
static UCHAR _nx_secure_tls_gen_keys_random[NX_SECURE_TLS_RANDOM_SIZE << 1];
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_generate_master_secret PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Yanwu Cai, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function generates the session keys used by TLS to encrypt */
/* the data being transmitted. It uses data gathered during the TLS */
/* handshake to generate a block of "key material" that is split into */
/* the various keys needed for each session. */
/* */
/* INPUT */
/* */
/* ciphersuite Selected cipher suite */
/* protocol_version Selected TLS version */
/* session_prf_method Pointer to PRF crypto method */
/* tls_key_material TLS key material */
/* pre_master_sec Pointer to pre-master secret */
/* pre_master_sec_size Size of pre-master secret */
/* master_sec Pointer to master secret */
/* prf_metadata Metadata for PRF crypto method*/
/* prf_metadata_size Size of PRF metadata */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* [nx_crypto_init] Initialize crypto */
/* [nx_crypto_operation] Crypto operation */
/* */
/* CALLED BY */
/* */
/* _nx_secure_tls_generate_keys Generate session keys */
/* */
/**************************************************************************/
UINT _nx_secure_generate_master_secret(const NX_SECURE_TLS_CIPHERSUITE_INFO *ciphersuite, USHORT protocol_version,
const NX_CRYPTO_METHOD *session_prf_method, NX_SECURE_TLS_KEY_MATERIAL *tls_key_material,
UCHAR *pre_master_sec, UINT pre_master_sec_size, UCHAR *master_sec,
VOID *prf_metadata, ULONG prf_metadata_size)
{
;
UINT status;
VOID *handler = NX_NULL;
NX_PARAMETER_NOT_USED(protocol_version);
/* Generate the session keys using the parameters obtained in the handshake.
By this point all the information needed to generate the TLS session key
material should have been gathered and stored in the TLS socket structure. */
/* Generate the Master Secret from the Pre-Master Secret.
From the RFC (TLS 1.1, TLS 1.2):
master_secret = PRF(pre_master_secret, "master secret",
ClientHello.random + ServerHello.random) [0..47];
The master secret is always exactly 48 bytes in length. The length
of the premaster secret will vary depending on key exchange method.
*/
/* The generation of key material is different between RSA and DH. */
if (ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_RSA
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
|| ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECDHE
|| ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECDH
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
#ifdef NX_SECURE_ENABLE_PSK_CIPHERSUITES
|| ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_PSK
#endif
#ifdef NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE
|| ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECJPAKE
#endif
)
{
/* Concatenate random values to feed into PRF. */
NX_SECURE_MEMCPY(_nx_secure_tls_gen_keys_random, tls_key_material -> nx_secure_tls_client_random,
NX_SECURE_TLS_RANDOM_SIZE); /* Use case of memcpy is verified. */
NX_SECURE_MEMCPY(&_nx_secure_tls_gen_keys_random[NX_SECURE_TLS_RANDOM_SIZE],
tls_key_material -> nx_secure_tls_server_random, NX_SECURE_TLS_RANDOM_SIZE); /* Use case of memcpy is verified. */
/* Generate the master secret using the pre-master secret, the defined TLS label, and the concatenated
random values. */
/* If we don't have a PRF method, the version is wrong! */
if (session_prf_method == NX_NULL)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(_nx_secure_tls_gen_keys_random, 0, sizeof(_nx_secure_tls_gen_keys_random));
#endif /* NX_SECURE_KEY_CLEAR */
return(NX_SECURE_TLS_PROTOCOL_VERSION_CHANGED);
}
/* Use the PRF to generate the master secret. */
if (session_prf_method -> nx_crypto_init != NX_NULL)
{
status = session_prf_method -> nx_crypto_init((NX_CRYPTO_METHOD*)session_prf_method,
pre_master_sec, (NX_CRYPTO_KEY_SIZE)pre_master_sec_size,
&handler,
prf_metadata,
prf_metadata_size);
if(status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(_nx_secure_tls_gen_keys_random, 0, sizeof(_nx_secure_tls_gen_keys_random));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
if (session_prf_method -> nx_crypto_operation != NX_NULL)
{
status = session_prf_method -> nx_crypto_operation(NX_CRYPTO_PRF,
handler,
(NX_CRYPTO_METHOD*)session_prf_method,
(UCHAR *)"master secret",
13,
_nx_secure_tls_gen_keys_random,
64,
NX_NULL,
master_sec,
48,
prf_metadata,
prf_metadata_size,
NX_NULL,
NX_NULL);
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(_nx_secure_tls_gen_keys_random, 0, sizeof(_nx_secure_tls_gen_keys_random));
#endif /* NX_SECURE_KEY_CLEAR */
if(status != NX_CRYPTO_SUCCESS)
{
/* Secrets cleared above. */
return(status);
}
}
if (session_prf_method -> nx_crypto_cleanup)
{
status = session_prf_method -> nx_crypto_cleanup(prf_metadata);
if(status != NX_CRYPTO_SUCCESS)
{
/* All secrets cleared above. */
return(status);
}
}
}
else
{
/* The chosen cipher is not supported. Likely an internal error since negotiation has already finished. */
return(NX_SECURE_TLS_UNSUPPORTED_CIPHER);
}
return(NX_SECURE_TLS_SUCCESS);
}
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