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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_send_client_key_exchange PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function encrypts the Pre-Master Secret (generated earlier) */
/* and populates an NX_PACKET with the complete ClientKeyExchange */
/* message (to be sent by the caller). It also will send ephemeral */
/* keys for ciphersuites that require them. */
/* */
/* INPUT */
/* */
/* tls_session TLS control block */
/* send_packet Outgoing TLS packet */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_secure_x509_remote_endpoint_certificate_get */
/* Get cert for remote host */
/* [nx_crypto_operation] Public-key ciphers */
/* [nx_crypto_init] Initialize Crypto Method */
/* _nx_secure_tls_remote_certificate_free_all */
/* Free all remote certificates */
/* */
/* CALLED BY */
/* */
/* _nx_secure_dtls_client_handshake DTLS client state machine */
/* _nx_secure_tls_client_handshake TLS client state machine */
/* */
/* 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 */
/* */
/**************************************************************************/
UINT _nx_secure_tls_send_client_key_exchange(NX_SECURE_TLS_SESSION *tls_session,
NX_PACKET *send_packet)
{
UINT status;
UINT data_size;
UCHAR *encrypted_data_ptr;
UCHAR *packet_buffer;
UCHAR rand_byte;
UINT i;
const NX_CRYPTO_METHOD *public_cipher_method;
NX_SECURE_X509_CERT *remote_certificate;
VOID *handler = NX_NULL;
#ifdef NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE
NX_CRYPTO_EXTENDED_OUTPUT extended_output;
#endif /* NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE */
/* Send a ClientKeyExchange message.
* Structure:
* | 2 | <Length> |
* | Length | Encrypted Pre-Master Secret |
*
* ECDHE ephemeral key structure:
* | 2 | <Length> |
* | Length | EC Diffie-Hellman Client Params |
*/
packet_buffer = send_packet -> nx_packet_append_ptr;
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);
}
#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)
{
data_size = (UINT)(1 + tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data[0]);
if ((data_size > sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data)) ||
(data_size > ((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)(send_packet -> nx_packet_append_ptr))))
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
/* Packet buffer too small. */
return(NX_SECURE_TLS_PACKET_BUFFER_TOO_SMALL);
}
NX_SECURE_MEMCPY(packet_buffer, tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data, data_size); /* Use case of memcpy is verified. */
}
else
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
{
/* Pointer to the output encrypted pre-master secret. */
encrypted_data_ptr = &packet_buffer[2];
#ifdef NX_SECURE_ENABLE_PSK_CIPHERSUITES
/* Check for PSK ciphersuites. */
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_PSK)
{
if ((tls_session -> nx_secure_tls_credentials.nx_secure_tls_client_psk.nx_secure_tls_psk_id_hint_size >
sizeof(tls_session -> nx_secure_tls_credentials.nx_secure_tls_client_psk.nx_secure_tls_psk_id_hint)) ||
(tls_session -> nx_secure_tls_credentials.nx_secure_tls_client_psk.nx_secure_tls_psk_id_hint_size >
(((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)(send_packet -> nx_packet_append_ptr)) - 2)))
{
/* Packet buffer too small. */
return(NX_SECURE_TLS_PACKET_BUFFER_TOO_SMALL);
}
/* Send the PSK Identity string to the remote server along with its length. */
NX_SECURE_MEMCPY(encrypted_data_ptr, tls_session -> nx_secure_tls_credentials.nx_secure_tls_client_psk.nx_secure_tls_psk_id,
tls_session -> nx_secure_tls_credentials.nx_secure_tls_client_psk.nx_secure_tls_psk_id_size); /* Use case of memcpy is verified. */
/* Make sure our size is correct. */
data_size = tls_session -> nx_secure_tls_credentials.nx_secure_tls_client_psk.nx_secure_tls_psk_id_size;
/* Put the length into our outgoing packet buffer. */
packet_buffer[0] = (UCHAR)((data_size & 0xFF00) >> 8);
packet_buffer[1] = (UCHAR)(data_size & 0x00FF);
data_size += 2;
}
else
#endif
#ifdef NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE
if (tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECJPAKE)
{
data_size = 0;
public_cipher_method = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth;
extended_output.nx_crypto_extended_output_data = packet_buffer;
extended_output.nx_crypto_extended_output_length_in_byte =
(ULONG)send_packet -> nx_packet_data_end - (ULONG)packet_buffer;
extended_output.nx_crypto_extended_output_actual_size = 0;
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_ECJPAKE_CLIENT_KEY_EXCHANGE_GENERATE,
tls_session -> nx_secure_public_auth_handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
NX_NULL, 0,
NX_NULL, 0, NX_NULL,
(UCHAR *)&extended_output,
sizeof(extended_output),
tls_session -> nx_secure_public_auth_metadata_area,
tls_session -> nx_secure_public_auth_metadata_size,
NX_NULL, NX_NULL);
if (status)
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
return(status);
}
data_size += extended_output.nx_crypto_extended_output_actual_size;
}
else
#endif
{
/* Extract the data to be verified from the remote certificate processed earlier. */
status = _nx_secure_x509_remote_endpoint_certificate_get(&tls_session -> nx_secure_tls_credentials.nx_secure_tls_certificate_store,
&remote_certificate);
if (status)
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
/* No certificate found, error! */
return(NX_SECURE_TLS_NO_CERT_SPACE_ALLOCATED);
}
/* Get the public cipher method from the ciphersuite. */
public_cipher_method = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_cipher;
/* If using RSA, the length is equal to the key size. */
data_size = remote_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_modulus_length;
/* PKCS#1 v1.5 padding. The scheme is to start with the block type (0x00, 0x02 for PKCS#1)
then pad with non-zero bytes (random is cryptographically more secure), followed with
a single 0 byte right before the payload, which comes at the end of the RSA block. */
NX_SECURE_MEMSET(_nx_secure_client_padded_pre_master, 0x0, sizeof(_nx_secure_client_padded_pre_master));
_nx_secure_client_padded_pre_master[1] = 0x2; /* Block type is 0x00, 0x02 */
for (i = 2; i < (data_size - NX_SECURE_TLS_RSA_PREMASTER_SIZE - 1); ++i)
{
/* PKCS#1 padding must be random, but CANNOT be 0. */
do
{
rand_byte = (UCHAR)NX_RAND();
} while (rand_byte == 0);
_nx_secure_client_padded_pre_master[i] = rand_byte;
}
if ((data_size < NX_SECURE_TLS_RSA_PREMASTER_SIZE) ||
(((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)(send_packet -> nx_packet_append_ptr)) < (2u + data_size)))
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
/* Invalid certificate modulus length. */
return(NX_SECURE_TLS_INVALID_CERTIFICATE);
}
/* Now put the pre-master data into the padded buffer - must be at the end. */
NX_SECURE_MEMCPY(&_nx_secure_client_padded_pre_master[data_size - NX_SECURE_TLS_RSA_PREMASTER_SIZE],
tls_session -> nx_secure_tls_key_material.nx_secure_tls_pre_master_secret, NX_SECURE_TLS_RSA_PREMASTER_SIZE); /* Use case of memcpy is verified. */
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 *)remote_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_modulus,
(NX_CRYPTO_KEY_SIZE)(remote_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)
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
#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);
}
}
if (public_cipher_method -> nx_crypto_operation != NX_NULL)
{
/* Now encrypt the pre-master secret using the public key provided by the remote host
and place the result in the outgoing packet buffer. */
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_DECRYPT,
handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)remote_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_exponent,
(NX_CRYPTO_KEY_SIZE)(remote_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_exponent_length << 3),
_nx_secure_client_padded_pre_master,
data_size,
NX_NULL,
encrypted_data_ptr,
data_size,
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)
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
#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);
}
}
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)
{
_nx_secure_tls_remote_certificate_free_all(tls_session);
#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);
}
}
/* Put the length into our outgoing packet buffer. */
packet_buffer[0] = (UCHAR)((data_size & 0xFF00) >> 8);
packet_buffer[1] = (UCHAR)(data_size & 0x00FF);
data_size += 2;
}
}
/* Let the caller know how many bytes we wrote. +2 for the length we just added. */
send_packet -> nx_packet_append_ptr = send_packet -> nx_packet_append_ptr + data_size;
send_packet -> nx_packet_length = send_packet -> nx_packet_length + data_size;
#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(NX_SECURE_TLS_SUCCESS);
}