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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 */
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_tls_generate_keys PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Timothy Stapko, 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 */
/* */
/* tls_session TLS control block */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* [nx_secure_generate_master_secret] Generate master secrets */
/* [nx_secure_generate_session_keys] Generate session keys */
/* */
/* 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 */
/* */
/**************************************************************************/
UINT _nx_secure_tls_generate_keys(NX_SECURE_TLS_SESSION *tls_session)
{
UCHAR *pre_master_sec;
UINT pre_master_sec_size;
UCHAR *master_sec;
UINT status;
const NX_CRYPTO_METHOD *session_prf_method = NX_NULL;
const NX_SECURE_TLS_CIPHERSUITE_INFO *ciphersuite;
/* 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.
*/
/* Figure out which ciphersuite we are using. */
ciphersuite = tls_session -> nx_secure_tls_session_ciphersuite;
if (ciphersuite == NX_NULL)
{
/* Likely internal error since at this point ciphersuite negotiation was theoretically completed. */
return(NX_SECURE_TLS_UNKNOWN_CIPHERSUITE);
}
pre_master_sec = tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret;
pre_master_sec_size = tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret_size;
master_sec = tls_session -> nx_secure_tls_key_material.nx_secure_tls_master_secret;
#if (NX_SECURE_TLS_TLS_1_2_ENABLED)
#ifdef NX_SECURE_ENABLE_DTLS
if (tls_session -> nx_secure_tls_protocol_version == NX_SECURE_TLS_VERSION_TLS_1_2 ||
tls_session -> nx_secure_tls_protocol_version == NX_SECURE_DTLS_VERSION_1_2)
#else
if (tls_session -> nx_secure_tls_protocol_version == NX_SECURE_TLS_VERSION_TLS_1_2)
#endif /* NX_SECURE_ENABLE_DTLS */
{
/* For TLS 1.2, the PRF is defined by the ciphersuite. However, if we are using an older ciphersuite,
* default to the TLS 1.2 default PRF, which uses SHA-256-HMAC. */
session_prf_method = ciphersuite -> nx_secure_tls_prf;
}
#endif
#if (NX_SECURE_TLS_TLS_1_0_ENABLED || NX_SECURE_TLS_TLS_1_1_ENABLED)
#ifdef NX_SECURE_ENABLE_DTLS
if (tls_session -> nx_secure_tls_protocol_version == NX_SECURE_TLS_VERSION_TLS_1_0 ||
tls_session -> nx_secure_tls_protocol_version == NX_SECURE_TLS_VERSION_TLS_1_1 ||
tls_session -> nx_secure_tls_protocol_version == NX_SECURE_DTLS_VERSION_1_0)
#else
if (tls_session -> nx_secure_tls_protocol_version == NX_SECURE_TLS_VERSION_TLS_1_0 ||
tls_session -> nx_secure_tls_protocol_version == NX_SECURE_TLS_VERSION_TLS_1_1)
#endif /* NX_SECURE_ENABLE_DTLS */
{
/* TLS 1.0 and TLS 1.1 use the same PRF. */
session_prf_method = tls_session -> nx_secure_tls_crypto_table -> nx_secure_tls_prf_1_method;
}
#endif
status = tls_session -> nx_secure_generate_master_secret(ciphersuite, tls_session -> nx_secure_tls_protocol_version, session_prf_method,
&tls_session -> nx_secure_tls_key_material, pre_master_sec, pre_master_sec_size,
master_sec, tls_session -> nx_secure_tls_prf_metadata_area,
tls_session -> nx_secure_tls_prf_metadata_size);
if (status != NX_SECURE_TLS_SUCCESS)
{
return(status);
}
/* Clear out the Pre-Master Secret (we don't need it anymore and keeping it in memory is dangerous). */
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(pre_master_sec, 0x0, sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret));
#endif /* NX_SECURE_KEY_CLEAR */
status = tls_session -> nx_secure_generate_session_keys(ciphersuite, tls_session -> nx_secure_tls_protocol_version, session_prf_method,
&tls_session -> nx_secure_tls_key_material, master_sec, tls_session -> nx_secure_tls_prf_metadata_area,
tls_session -> nx_secure_tls_prf_metadata_size);
return(status);
}
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