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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 */
/** */
/** Datagram Transport Layer Security (DTLS) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_dtls.h"
#ifdef NX_SECURE_ENABLE_DTLS
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_dtls_send_serverhello PORTABLE C */
/* 6.4.3 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function generates a ServerHello message, which is used to */
/* respond to an incoming ClientHello message and provide the remote */
/* TLS Client with the chosen ciphersuite and key generation data. */
/* */
/* INPUT */
/* */
/* dtls_session DTLS control block */
/* send_packet Packet used to send message */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* [nx_crypto_operation] Crypto operation */
/* [nx_secure_tls_session_time_function] Get the current time for the */
/* DTLS timestamp */
/* */
/* CALLED BY */
/* */
/* _nx_secure_dtls_server_handshake DTLS server state machine */
/* */
/**************************************************************************/
UINT _nx_secure_dtls_send_serverhello(NX_SECURE_DTLS_SESSION *dtls_session, NX_PACKET *send_packet)
{
UINT length;
UINT gmt_time;
UINT random_value;
UINT i;
USHORT ciphersuite;
#ifdef NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE
UINT status;
UCHAR *extension_total_length_ptr;
USHORT extension_total_length;
USHORT extension_length;
USHORT extension_type;
NX_CRYPTO_METHOD *crypto_method;
NX_CRYPTO_EXTENDED_OUTPUT extended_output;
#endif
UCHAR *packet_buffer;
NX_SECURE_TLS_SESSION *tls_session;
USHORT protocol_version;
/* Build up the ServerHello message.
* Structure:
* | 2 | 4 + 28 | 1 | <SID len> | 2 | 1 | 2 | <Ext. Len> |
* | TLS version | Random (time + random) | SID length | Session ID | Ciphersuite | Compression | Ext. Len | Extensions |
*/
tls_session = &dtls_session -> nx_secure_dtls_tls_session;
if ((6u + sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random) +
tls_session -> nx_secure_tls_session_id_length) >
((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)(send_packet -> nx_packet_prepend_ptr)))
{
/* Packet buffer is too small. */
return(NX_SECURE_TLS_PACKET_BUFFER_TOO_SMALL);
}
packet_buffer = send_packet -> nx_packet_prepend_ptr;
/* Use our length as an index into the buffer. */
length = 0;
/* First two bytes of the hello following the header are the TLS major and minor version numbers. */
/* DTLS version. */
protocol_version = tls_session -> nx_secure_tls_protocol_version;
packet_buffer[length] = (UCHAR)((protocol_version & 0xFF00) >> 8);
packet_buffer[length + 1] = (UCHAR)(protocol_version & 0x00FF);
length += 2;
/* Set the Server random data, used in key generation. First 4 bytes is GMT time. */
gmt_time = 0;
if (tls_session -> nx_secure_tls_session_time_function != NX_NULL)
{
gmt_time = tls_session -> nx_secure_tls_session_time_function();
}
NX_CHANGE_ULONG_ENDIAN(gmt_time);
NX_SECURE_MEMCPY(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random, (UCHAR *)&gmt_time, sizeof(gmt_time)); /* Use case of memcpy is verified. */
/* Next 28 bytes is random data. */
for (i = 0; i < 28; i += (UINT)sizeof(random_value))
{
random_value = (UINT)NX_RAND();
*(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random + (i + 4)) = (UCHAR)(random_value);
*(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random + (i + 5)) = (UCHAR)(random_value >> 8);
*(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random + (i + 6)) = (UCHAR)(random_value >> 16);
*(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random + (i + 7)) = (UCHAR)(random_value >> 24);
}
/* Copy the random data into the packet. */
NX_SECURE_MEMCPY(&packet_buffer[length], tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random,
sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random)); /* Use case of memcpy is verified. */
length += sizeof(tls_session -> nx_secure_tls_key_material.nx_secure_tls_server_random);
/* Session ID length is one byte. */
packet_buffer[length] = tls_session -> nx_secure_tls_session_id_length;
length++;
/* Session ID follows. */
if (tls_session -> nx_secure_tls_session_id_length > 0)
{
NX_SECURE_MEMCPY(&packet_buffer[length], tls_session -> nx_secure_tls_session_id, tls_session -> nx_secure_tls_session_id_length); /* Use case of memcpy is verified. */
length += tls_session -> nx_secure_tls_session_id_length;
}
/* Finally, our chosen ciphersuite - this is selected when we receive the Client Hello. */
ciphersuite = tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_ciphersuite;
packet_buffer[length] = (UCHAR)(ciphersuite >> 8);
packet_buffer[length + 1] = (UCHAR)ciphersuite;
length += 2;
/* Compression method - for now this is NULL. */
packet_buffer[length] = 0x0;
length++;
/* TLS extensions will go here once supported. */
#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)
{
if (((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)(send_packet -> nx_packet_prepend_ptr)) < 12u)
{
/* Packet buffer is too small. */
return(NX_SECURE_TLS_PACKET_BUFFER_TOO_SMALL);
}
crypto_method = (NX_CRYPTO_METHOD*)tls_session -> nx_secure_tls_session_ciphersuite -> nx_secure_tls_public_auth;
extension_total_length_ptr = &packet_buffer[length];
extension_total_length = 10;
length += 2;
/* ec_point_formats Extension. */
extension_type = NX_SECURE_TLS_EXTENSION_EC_POINT_FORMATS;
packet_buffer[length] = (UCHAR)((extension_type >> 8) & 0xFF);
packet_buffer[length + 1] = (UCHAR)(extension_type & 0xFF);
length += 2;
/* ec_point_formats Length: 2. */
extension_length = 2;
packet_buffer[length] = (UCHAR)((extension_length >> 8) & 0xFF);
packet_buffer[length + 1] = (UCHAR)(extension_length & 0xFF);
length += 2;
/* EC point formats Length: 1. */
packet_buffer[length] = 1;
length += 1;
/* EC point format: uncompressed(0). */
packet_buffer[length] = 0;
length += 1;
/* ecjpake_key_kp_pair Extension. */
extension_type = NX_SECURE_TLS_EXTENSION_ECJPAKE_KEY_KP_PAIR;
packet_buffer[length] = (UCHAR)((extension_type >> 8) & 0xFF);
packet_buffer[length + 1] = (UCHAR)(extension_type & 0xFF);
length += 2;
/* ecjpake_key_kp_pair Length. */
length += 2;
extended_output.nx_crypto_extended_output_data = &packet_buffer[length];
extended_output.nx_crypto_extended_output_length_in_byte =
(ULONG)send_packet -> nx_packet_data_end - (ULONG)&packet_buffer[length];
extended_output.nx_crypto_extended_output_actual_size = 0;
status = crypto_method -> nx_crypto_operation(NX_CRYPTO_ECJPAKE_SERVER_HELLO_GENERATE,
NX_NULL,
crypto_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)
{
return(status);
}
/* Set length for ecjpake_key_kp_pair extension. */
extension_length = (USHORT)extended_output.nx_crypto_extended_output_actual_size;
packet_buffer[length - 2] = (UCHAR)((extension_length >> 8) & 0xFF);
packet_buffer[length - 1] = (UCHAR)(extension_length & 0xFF);
extension_total_length = (USHORT)(extension_total_length +
extended_output.nx_crypto_extended_output_actual_size);
length += extended_output.nx_crypto_extended_output_actual_size;
/* Set extension total length. */
extension_total_length_ptr[0] = (UCHAR)((extension_total_length >> 8) & 0xFF);
extension_total_length_ptr[1] = (UCHAR)(extension_total_length & 0xFF);
}
#endif
/* Finally, we have a complete length and can put it into the buffer. Before that,
save off and return the number of bytes we wrote and need to send. */
send_packet -> nx_packet_append_ptr = send_packet -> nx_packet_prepend_ptr + length;
send_packet -> nx_packet_length = send_packet -> nx_packet_length + length;
return(NX_SECURE_TLS_SUCCESS);
}
#endif /* NX_SECURE_ENABLE_DTLS */
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