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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_process_newsessionticket PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function processes a NewSessionTicket message from a TLS */
/* Server. The message contains data used to generate a PSK that can */
/* be used for session resumption should the same client attempt */
/* another connection within the lifespan of the ticket. */
/* */
/* INPUT */
/* */
/* tls_session TLS control block */
/* send_packet Packet used to send message */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* N/A */
/* */
/* CALLED BY */
/* */
/* _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, */
/* fixed compiler warnings, */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
#if (NX_SECURE_TLS_TLS_1_3_ENABLED)
UINT _nx_secure_tls_process_newsessionticket(NX_SECURE_TLS_SESSION *tls_session, UCHAR *packet_buffer,
UINT message_length)
{
UINT status = NX_SUCCESS;
UINT lifetime;
UINT nonce;
UINT nonce_len;
UINT ticket_len;
UCHAR *ticket;
UINT psk_count;
NX_SECURE_TLS_PSK_STORE *ticket_psk;
/* From RFC 8446:
struct {
uint32 ticket_lifetime;
uint32 ticket_age_add;
opaque ticket_nonce<0..255>;
opaque ticket<1..2^16-1>;
Extension extensions<0..2^16-2>;
} NewSessionTicket;
| 4 | 4 | 1 | <nonce_len> | 2 | <ticket_len> | 2 | <extensions_len> |
| lifetime | age add | nonce_len | nonce | ticket_len | ticket | extensions_len | extensions |
ticket_lifetime: Indicates the lifetime in seconds as a 32-bit
unsigned integer in network byte order from the time of ticket
issuance. Servers MUST NOT use any value greater than
604800 seconds (7 days). The value of zero indicates that the
ticket should be discarded immediately. Clients MUST NOT cache
tickets for longer than 7 days, regardless of the ticket_lifetime,
and MAY delete tickets earlier based on local policy. A server
MAY treat a ticket as valid for a shorter period of time than what
is stated in the ticket_lifetime.
ticket_age_add: A securely generated, random 32-bit value that is
used to obscure the age of the ticket that the client includes in
the "pre_shared_key" extension. The client-side ticket age is
added to this value modulo 2^32 to obtain the value that is
transmitted by the client. The server MUST generate a fresh value
for each ticket it sends.
ticket_nonce: A per-ticket value that is unique across all tickets
issued on this connection.
ticket: The value of the ticket to be used as the PSK identity. The
ticket itself is an opaque label. It MAY be either a database
lookup key or a self-encrypted and self-authenticated value.
extensions: A set of extension values for the ticket. The
"Extension" format is defined in Section 4.2. Clients MUST ignore
unrecognized extensions.
The sole extension currently defined for NewSessionTicket is
"early_data", indicating that the ticket may be used to send 0-RTT
data (Section 4.2.10). It contains the following value:
max_early_data_size: The maximum amount of 0-RTT data that the
client is allowed to send when using this ticket, in bytes. Only
Application Data payload (i.e., plaintext but not padding or the
inner content type byte) is counted. A server receiving more than
max_early_data_size bytes of 0-RTT data SHOULD terminate the
connection with an "unexpected_message" alert. Note that servers
that reject early data due to lack of cryptographic material will
be unable to differentiate padding from content, so clients
SHOULD NOT depend on being able to send large quantities of
padding in early data records.
The PSK associated with the ticket is computed as:
HKDF-Expand-Label(resumption_master_secret,
"resumption", ticket_nonce, Hash.length)
*/
/* Get a PSK entry into which we can copy the ticket data we received. */
psk_count = tls_session->nx_secure_tls_credentials.nx_secure_tls_psk_count;
psk_count++;
if(psk_count >= NX_SECURE_TLS_MAX_PSK_KEYS)
{
psk_count = 0;
}
ticket_psk = &(tls_session->nx_secure_tls_credentials.nx_secure_tls_psk_store[psk_count]);
/* First, the ticket lifetime in ms - 604800 is the maximum. */
lifetime = (UINT)((packet_buffer[0] << 24) + (packet_buffer[1] << 16) + (packet_buffer[2] << 8) + packet_buffer[3]);
packet_buffer = &packet_buffer[4];
if(lifetime > NX_SECURE_TLS_MAX_SESSION_TICKET_AGE)
{
return(NX_SECURE_TLS_INVALID_SESSION_TICKET);
}
/* Save the lifetime of the ticket. */
ticket_psk->nx_secure_tls_psk_ticket_lifetime = lifetime;
/* Skip the age add value. */
packet_buffer = &packet_buffer[4];
/* Get the nonce length. */
nonce_len = packet_buffer[0];
packet_buffer = &packet_buffer[1];
/* Get the nonce. */
if(nonce_len > message_length || nonce_len > NX_SECURE_TLS_MAX_PSK_NONCE_SIZE)
{
return(NX_SECURE_TLS_INVALID_SESSION_TICKET);
}
nonce = (UINT)((packet_buffer[0] << 24) + (packet_buffer[1] << 16) + (packet_buffer[2] << 8) + packet_buffer[3]);;
packet_buffer = &packet_buffer[nonce_len];
/* Now for the ticket ID itself. 16-bit length with the ticket being a label
used as the PSK identity. */
ticket_len = (USHORT)((packet_buffer[0] << 8) + packet_buffer[1]);
packet_buffer = &packet_buffer[2];
ticket = (UCHAR *)(&packet_buffer[0]);
if(ticket_len > message_length || ticket_len > NX_SECURE_TLS_MAX_PSK_ID_SIZE)
{
return(NX_SECURE_TLS_INVALID_SESSION_TICKET);
}
packet_buffer = &packet_buffer[ticket_len];
/* Copy ticket to PSK store - the ticket is the PSK ID used to identify the PSK in the future. */
NX_SECURE_MEMCPY(ticket_psk->nx_secure_tls_psk_id, ticket, ticket_len); /* Use case of memcpy is verified. */
ticket_psk->nx_secure_tls_psk_id_size = ticket_len;
/* We can now generate the PSK for this session using our ticket nonce and the cryptographic
secrets we created earlier in the handshake. */
status = _nx_secure_tls_1_3_session_psk_generate(tls_session, ticket_psk, (UCHAR *)nonce, nonce_len);
return(status);
}
#endif
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