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nx_secure/src/nx_secure_tls_process_client_key_exchange.c
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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) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_tls.h"
static UCHAR _nx_secure_client_padded_pre_master[600];
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_tls_process_client_key_exchange PORTABLE C */
/* 6.1.7 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function processes an incoming ClientKeyExchange message, */
/* which contains the encrypted Pre-Master Secret. This function */
/* decrypts the Pre-Master Secret and saves it in the TLS session */
/* control block for use in generating session key material later. */
/* */
/* INPUT */
/* */
/* tls_session TLS control block */
/* packet_buffer Pointer to message data */
/* message_length Length of message data (bytes)*/
/* id TLS or DTLS */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_secure_tls_generate_premaster_secret */
/* Generate the shared secret */
/* used to generate keys later */
/* _nx_secure_x509_local_device_certificate_get */
/* Get the local certificate */
/* for its keys */
/* _nx_secure_tls_find_curve_method Find named curve used */
/* [nx_crypto_init] Initialize crypto */
/* [nx_crypto_operation] Crypto operation */
/* */
/* CALLED BY */
/* */
/* _nx_secure_dtls_server_handshake DTLS server state machine */
/* _nx_secure_tls_server_handshake TLS server state machine */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Timothy Stapko Initial Version 6.0 */
/* 09-30-2020 Timothy Stapko Modified comment(s), update */
/* ECC find curve method, */
/* verified memcpy use cases, */
/* resulting in version 6.1 */
/* 06-02-2021 Timothy Stapko Modified comment(s), */
/* supported hardware EC */
/* private key, */
/* resulting in version 6.1.7 */
/* */
/**************************************************************************/
UINT _nx_secure_tls_process_client_key_exchange(NX_SECURE_TLS_SESSION *tls_session,
UCHAR *packet_buffer, UINT message_length, UINT id)
{
USHORT length;
UINT status;
UCHAR *encrypted_pre_master_secret;
const NX_CRYPTO_METHOD *public_cipher_method;
NX_SECURE_X509_CERT *local_certificate;
UINT user_defined_key;
VOID *handler = NX_NULL;
UCHAR rand_byte;
UINT i;
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
NX_SECURE_EC_PRIVATE_KEY *ec_privkey;
NX_SECURE_TLS_ECDHE_HANDSHAKE_DATA *ecdhe_data;
NX_CRYPTO_EXTENDED_OUTPUT extended_output;
const NX_CRYPTO_METHOD *curve_method;
const NX_CRYPTO_METHOD *ecdh_method;
UCHAR *private_key;
UINT private_key_length;
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
#ifndef NX_SECURE_ENABLE_PSK_CIPHERSUITES
NX_PARAMETER_NOT_USED(id);
#endif /* NX_SECURE_ENABLE_PSK_CIPHERSUITES */
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);
}
/* Process key material. The contents of the handshake record differ according to the
ciphersuite chosen in the Client/Server Hello negotiation. */
#ifdef NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE
/* Check for ECJ-PAKE ciphersuites and generate the pre-master-secret. */
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECJPAKE)
{
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret_size = 32;
public_cipher_method = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth;
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_ECJPAKE_CLIENT_KEY_EXCHANGE_PROCESS,
tls_session -> nx_secure_public_auth_handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
NX_NULL, 0,
packet_buffer,
message_length,
NX_NULL,
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret,
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret_size,
tls_session -> nx_secure_public_auth_metadata_area,
tls_session -> nx_secure_public_auth_metadata_size,
NX_NULL, NX_NULL);
if (status)
{
return(status);
}
if (public_cipher_method -> nx_crypto_cleanup)
{
status = public_cipher_method -> nx_crypto_cleanup(tls_session -> nx_secure_public_auth_metadata_area);
if (status)
{
return(status);
}
}
}
else
#endif
{
#ifdef NX_SECURE_ENABLE_PSK_CIPHERSUITES
/* Check for PSK ciphersuites and generate the pre-master-secret. */
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_PSK)
{
status = _nx_secure_tls_generate_premaster_secret(tls_session, id);
if (status != NX_SUCCESS)
{
return(status);
}
}
else
#endif
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECDH ||
tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECDHE)
{
length = packet_buffer[0];
if (length > message_length)
{
/* The public key length is larger than the header indicated. */
return(NX_SECURE_TLS_INCORRECT_MESSAGE_LENGTH);
}
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECDH)
{
/* Get the local certificate. */
if (tls_session -> nx_secure_tls_credentials.nx_secure_tls_active_certificate != NX_NULL)
{
local_certificate = tls_session -> nx_secure_tls_credentials.nx_secure_tls_active_certificate;
}
else
{
/* Get reference to local device certificate. NX_NULL is passed for name to get default entry. */
status = _nx_secure_x509_local_device_certificate_get(&tls_session -> nx_secure_tls_credentials.nx_secure_tls_certificate_store,
NX_NULL, &local_certificate);
if (status != NX_SUCCESS)
{
local_certificate = NX_NULL;
}
}
if (local_certificate == NX_NULL)
{
/* No certificate found, error! */
return(NX_SECURE_TLS_CERTIFICATE_NOT_FOUND);
}
ec_privkey = &local_certificate -> nx_secure_x509_private_key.ec_private_key;
/* Find out which named curve the local certificate is using. */
status = _nx_secure_tls_find_curve_method(tls_session, (USHORT)(ec_privkey -> nx_secure_ec_named_curve), &curve_method, NX_NULL);
if(status != NX_SUCCESS)
{
return(status);
}
private_key = (UCHAR *)ec_privkey -> nx_secure_ec_private_key;
private_key_length = ec_privkey -> nx_secure_ec_private_key_length;
}
else
{
ecdhe_data = (NX_SECURE_TLS_ECDHE_HANDSHAKE_DATA *)tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data;
/* Find out which named curve the we are using. */
status = _nx_secure_tls_find_curve_method(tls_session, (USHORT)ecdhe_data -> nx_secure_tls_ecdhe_named_curve, &curve_method, NX_NULL);
if(status != NX_SUCCESS)
{
return(status);
}
private_key = ecdhe_data -> nx_secure_tls_ecdhe_private_key;
private_key_length = ecdhe_data -> nx_secure_tls_ecdhe_private_key_length;
}
if (curve_method == NX_NULL)
{
/* No named curve is selected. */
return(NX_SECURE_TLS_UNSUPPORTED_ECC_CURVE);
}
ecdh_method = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_cipher;
if (ecdh_method -> nx_crypto_operation == NX_NULL)
{
return(NX_SECURE_TLS_MISSING_CRYPTO_ROUTINE);
}
if (ecdh_method -> nx_crypto_init != NX_NULL)
{
status = ecdh_method -> nx_crypto_init((NX_CRYPTO_METHOD*)ecdh_method,
NX_NULL,
0,
&handler,
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
status = ecdh_method -> nx_crypto_operation(NX_CRYPTO_EC_CURVE_SET, handler,
(NX_CRYPTO_METHOD*)ecdh_method, NX_NULL, 0,
(UCHAR *)curve_method, sizeof(NX_CRYPTO_METHOD *), NX_NULL,
NX_NULL, 0,
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if (status != NX_CRYPTO_SUCCESS)
{
return(status);
}
/* Import the private key to the ECDH context. */
status = ecdh_method -> nx_crypto_operation(NX_CRYPTO_DH_KEY_PAIR_IMPORT, handler,
(NX_CRYPTO_METHOD*)ecdh_method,
private_key, private_key_length << 3,
NX_NULL, 0, NX_NULL,
NX_NULL,
0,
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if (status != NX_CRYPTO_SUCCESS)
{
return(status);
}
extended_output.nx_crypto_extended_output_data = tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret;
extended_output.nx_crypto_extended_output_length_in_byte = sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret);
extended_output.nx_crypto_extended_output_actual_size = 0;
status = ecdh_method -> nx_crypto_operation(NX_CRYPTO_DH_CALCULATE, handler,
(NX_CRYPTO_METHOD*)ecdh_method, NX_NULL, 0,
&packet_buffer[1],
length, NX_NULL,
(UCHAR *)&extended_output,
sizeof(extended_output),
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if (status != NX_CRYPTO_SUCCESS)
{
return(status);
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret_size = extended_output.nx_crypto_extended_output_actual_size;
if (ecdh_method -> nx_crypto_cleanup)
{
status = ecdh_method -> nx_crypto_cleanup(tls_session -> nx_secure_public_cipher_metadata_area);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
}
else
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
{ /* Certificate-based authentication. */
/* Get pre-master-secret length. */
length = (USHORT)((packet_buffer[0] << 8) + (USHORT)packet_buffer[1]);
packet_buffer += 2;
if (length > message_length)
{
/* The payload is larger than the header indicated. */
return(NX_SECURE_TLS_INCORRECT_MESSAGE_LENGTH);
}
/* Pointer to the encrypted pre-master secret in our packet buffer. */
encrypted_pre_master_secret = &packet_buffer[0];
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_ciphersuite == TLS_NULL_WITH_NULL_NULL)
{
/* Special case - NULL ciphersuite. No keys are generated. */
if (length > sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret))
{
length = sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret);
}
NX_SECURE_MEMCPY(tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret, encrypted_pre_master_secret, length); /* Use case of memcpy is verified. */
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret_size = length;
}
/* Get reference to local device certificate. NX_NULL is passed for name to get default entry. */
status = _nx_secure_x509_local_device_certificate_get(&tls_session -> nx_secure_tls_credentials.nx_secure_tls_certificate_store,
NX_NULL, &local_certificate);
if (status)
{
/* No certificate found, error! */
return(NX_SECURE_TLS_CERTIFICATE_NOT_FOUND);
}
/* Get the public cipher method pointer for this session. */
public_cipher_method = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_cipher;
/* Check for user-defined key types. */
user_defined_key = NX_FALSE;
if (((local_certificate -> nx_secure_x509_private_key_type & NX_SECURE_X509_KEY_TYPE_USER_DEFINED_MASK) != 0x0) ||
( local_certificate -> nx_secure_x509_private_key_type == NX_SECURE_X509_KEY_TYPE_HARDWARE))
{
user_defined_key = NX_TRUE;
}
/* See if we are using RSA. Separate from other methods (e.g. ECC, DH) for proper handling of padding. */
if (public_cipher_method -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_RSA &&
local_certificate -> nx_secure_x509_public_algorithm == NX_SECURE_TLS_X509_TYPE_RSA)
{
/* Check for user-defined keys. */
if (user_defined_key)
{
/* A user-defined key is passed directly into the crypto routine. */
status = public_cipher_method -> nx_crypto_operation(local_certificate -> nx_secure_x509_private_key_type,
NX_NULL,
(NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)local_certificate -> nx_secure_x509_private_key.user_key.key_data,
(NX_CRYPTO_KEY_SIZE)(local_certificate -> nx_secure_x509_private_key.user_key.key_length),
encrypted_pre_master_secret,
length,
NX_NULL,
_nx_secure_client_padded_pre_master,
sizeof(_nx_secure_client_padded_pre_master),
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
else
{
/* Generic RSA operation, use pre-parsed RSA key data. */
if (public_cipher_method -> nx_crypto_init != NX_NULL)
{
/* Initialize the crypto method with public key. */
status = public_cipher_method -> nx_crypto_init((NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)local_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_modulus,
(NX_CRYPTO_KEY_SIZE)(local_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_modulus_length << 3),
&handler,
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
if (public_cipher_method -> nx_crypto_operation != NX_NULL)
{
/* Check for P and Q in the private key. If they are present, we can use them to
speed up RSA using the Chinese Remainder Theorem version of the algorithm. */
if (local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_prime_p != NX_NULL &&
local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_prime_q != NX_NULL)
{
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_SET_PRIME_P,
handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
NX_NULL,
0,
(VOID *)local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_prime_p,
local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_prime_p_length,
NX_NULL,
NX_NULL,
0,
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_SET_PRIME_Q,
handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
NX_NULL,
0,
(VOID *)local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_prime_q,
local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_prime_q_length,
NX_NULL,
NX_NULL,
0,
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
/* Decrypt the pre-master-secret using the private key provided by the user
and place the result in the session key material space in our socket. */
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_DECRYPT,
handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_exponent,
(NX_CRYPTO_KEY_SIZE)(local_certificate -> nx_secure_x509_private_key.rsa_private_key.nx_secure_rsa_private_exponent_length << 3),
encrypted_pre_master_secret,
length,
NX_NULL,
_nx_secure_client_padded_pre_master,
sizeof(_nx_secure_client_padded_pre_master),
tls_session -> nx_secure_public_cipher_metadata_area,
tls_session -> nx_secure_public_cipher_metadata_size,
NX_NULL, NX_NULL);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
if (public_cipher_method -> nx_crypto_cleanup)
{
status = public_cipher_method -> nx_crypto_cleanup(tls_session -> nx_secure_public_cipher_metadata_area);
if(status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(_nx_secure_client_padded_pre_master, 0, sizeof(_nx_secure_client_padded_pre_master));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
}
/* Check padding - first 2 bytes should be 0x00, 0x02 for PKCS#1 padding. A 0x00 byte should immediately
precede the data. */
if (_nx_secure_client_padded_pre_master[0] != 0x00 ||
_nx_secure_client_padded_pre_master[1] != 0x02 ||
_nx_secure_client_padded_pre_master[length - NX_SECURE_TLS_RSA_PREMASTER_SIZE - 1] != 0x00)
{
/* Invalid padding. To avoid Bleichenbacher's attack, use random numbers to
generate premaster secret and continue the operation (which will be properly
taken care of later in _nx_secure_tls_process_finished()).
This is described in RFC 5246, section 7.4.7.1, page 58-59. */
/* Generate premaster secret using random numbers. */
for (i = 0; i < NX_SECURE_TLS_RSA_PREMASTER_SIZE; ++i)
{
/* PKCS#1 padding must be random, but CANNOT be 0. */
do
{
rand_byte = (UCHAR)NX_RAND();
} while (rand_byte == 0);
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret[i] = rand_byte;
}
}
else
{
/* Extract the 48 bytes of the actual pre-master secret from the data we just decrypted, stripping the padding, which
comes at the beginning of the decrypted block (the pre-master secret is the last 48 bytes. */
NX_SECURE_MEMCPY(tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret,
&_nx_secure_client_padded_pre_master[length - NX_SECURE_TLS_RSA_PREMASTER_SIZE], NX_SECURE_TLS_RSA_PREMASTER_SIZE); /* Use case of memcpy is verified. */
}
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret_size = NX_SECURE_TLS_RSA_PREMASTER_SIZE;
} /* End RSA-specific section. */
else
{
/* Unknown or invalid public cipher. */
return(NX_SECURE_TLS_UNSUPPORTED_PUBLIC_CIPHER);
}
}
}
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(_nx_secure_client_padded_pre_master, 0, sizeof(_nx_secure_client_padded_pre_master));
#endif /* NX_SECURE_KEY_CLEAR */
#ifdef NX_SECURE_TLS_SERVER_DISABLED
/* If TLS Server is disabled and we have processed a ClientKeyExchange, something is wrong... */
tls_session -> nx_secure_tls_client_state = NX_SECURE_TLS_CLIENT_STATE_ERROR;
return(NX_SECURE_TLS_INVALID_STATE);
#else
return(NX_SUCCESS);
#endif
}