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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"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_tls_send_server_key_exchange PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function generates a ServerKeyExchange message, which is used */
/* when the chosen ciphersuite requires additional information for key */
/* generation, such as when using Diffie-Hellman ciphers. */
/* */
/* INPUT */
/* */
/* tls_session TLS control block */
/* send_packet Packet used to send message */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_secure_tlx_ecc_generate_keys Generate keys for ECC exchange*/
/* [nx_crypto_init] Initialize Crypto Method */
/* [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), */
/* verified memcpy use cases, */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
UINT _nx_secure_tls_send_server_key_exchange(NX_SECURE_TLS_SESSION *tls_session,
NX_PACKET *send_packet)
{
UINT length;
const NX_SECURE_TLS_CIPHERSUITE_INFO *ciphersuite;
#if defined(NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE) || defined(NX_SECURE_ENABLE_ECC_CIPHERSUITE)
UINT status;
#endif /* defined(NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE) || defined(NX_SECURE_ENABLE_ECC_CIPHERSUITE) */
#if defined(NX_SECURE_ENABLE_PSK_CIPHERSUITES) || defined(NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE) || defined(NX_SECURE_ENABLE_ECC_CIPHERSUITE)
UCHAR *packet_buffer;
#endif /* defined(NX_SECURE_ENABLE_PSK_CIPHERSUITES) || defined(NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE) || defined(NX_SECURE_ENABLE_ECC_CIPHERSUITE) */
#ifdef NX_SECURE_ENABLE_PSK_CIPHERSUITES
USHORT identity_length;
UCHAR *identity;
#endif
#if defined(NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE)
USHORT named_curve;
NX_CRYPTO_METHOD *crypto_method;
NX_CRYPTO_EXTENDED_OUTPUT extended_output;
#endif /* defined(NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE) */
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
NX_SECURE_TLS_ECDHE_HANDSHAKE_DATA *ecdhe_data;
#endif
/* Build up the server key exchange message. Structure:
* | 2 | <key data length> |
* | Key data length | Key data (opaque) |
*/
/* 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);
}
length = 0;
/* In the future, any Diffie-Hellman-based ciphersuites will populate this message with key
data. RSA ciphersuites do not use this message. */
#ifdef NX_SECURE_ENABLE_PSK_CIPHERSUITES
/* Get a pointer to fill our packet. */
packet_buffer = send_packet -> nx_packet_append_ptr;
/* Check for PSK ciphersuites. */
if (ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_PSK)
{
/* If PSK is being used, the server sends an identity value to the client so
the client can respond with the appropriate PSK. */
/* Get identity hint and length. */
identity = tls_session -> nx_secure_tls_credentials.nx_secure_tls_psk_store[0].nx_secure_tls_psk_id_hint;
identity_length = (USHORT)tls_session -> nx_secure_tls_credentials.nx_secure_tls_psk_store[0].nx_secure_tls_psk_id_hint_size;
if ((identity_length + 2u) > ((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)packet_buffer))
{
/* Packet buffer too small. */
return(NX_SECURE_TLS_PACKET_BUFFER_TOO_SMALL);
}
/* Use identity hint length for key data length. */
packet_buffer[length] = (UCHAR)((identity_length & 0xFF00) >> 8);
packet_buffer[length + 1] = (UCHAR)(identity_length & 0x00FF);
length = (USHORT)(length + 2);
/* Extract the identity hint and put it into the packet buffer. */
NX_SECURE_MEMCPY(&packet_buffer[length], identity, identity_length); /* Use case of memcpy is verified. */
/* Advance our total length. */
length = (USHORT)(length + identity_length);
}
#endif
#ifdef NX_SECURE_ENABLE_ECJPAKE_CIPHERSUITE
/* Check for ECJ-PAKE ciphersuites. */
if (ciphersuite -> nx_secure_tls_public_auth -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECJPAKE)
{
/* Get a pointer to fill our packet. */
packet_buffer = send_packet -> nx_packet_append_ptr;
if (((ULONG)(send_packet -> nx_packet_data_end) - (ULONG)(&packet_buffer[length])) < 3)
{
/* Packet buffer too small. */
return(NX_SECURE_TLS_PACKET_BUFFER_TOO_SMALL);
}
/* ECCurveType: named_curve (3). */
packet_buffer[length] = 3;
length += 1;
/* NamedCurve: secp256r1 (23) */
named_curve = (USHORT)NX_CRYPTO_EC_SECP256R1;
packet_buffer[length] = (UCHAR)((named_curve >> 8) & 0xFF);
packet_buffer[length + 1] = (UCHAR)(named_curve & 0xFF);
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;
crypto_method = (NX_CRYPTO_METHOD*)ciphersuite -> nx_secure_tls_public_auth;
status = crypto_method -> nx_crypto_operation(NX_CRYPTO_ECJPAKE_SERVER_KEY_EXCHANGE_GENERATE,
&tls_session -> nx_secure_public_auth_handler,
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);
}
length += extended_output.nx_crypto_extended_output_actual_size;
}
#endif
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
/* Check for ECDHE ciphersuites. */
if (ciphersuite -> nx_secure_tls_public_cipher -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_ECDHE)
{
ecdhe_data = (NX_SECURE_TLS_ECDHE_HANDSHAKE_DATA *)tls_session -> nx_secure_tls_key_material.nx_secure_tls_new_key_material_data;
packet_buffer = send_packet -> nx_packet_append_ptr;
length = (UINT)(send_packet->nx_packet_data_end - send_packet->nx_packet_append_ptr);
status = _nx_secure_tls_ecc_generate_keys(tls_session, ecdhe_data -> nx_secure_tls_ecdhe_named_curve, NX_TRUE,
packet_buffer, &length, ecdhe_data);
if (status != NX_SUCCESS)
{
return(status);
}
}
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
/* Finally, we have a complete length and can adjust our packet accordingly. */
send_packet -> nx_packet_append_ptr = send_packet -> nx_packet_append_ptr + length;
send_packet -> nx_packet_length = send_packet -> nx_packet_length + length;
return(NX_SECURE_TLS_SUCCESS);
}