404 lines
12 KiB
Rust
404 lines
12 KiB
Rust
/*
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*
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* Copyright (c) 2020-2022 Project CHIP Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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use core::{cell::RefCell, fmt::Write, time::Duration};
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use super::{
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common::{SCStatusCodes, PROTO_ID_SECURE_CHANNEL},
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spake2p::{Spake2P, VerifierData},
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};
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use crate::{
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alloc, crypto,
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error::{Error, ErrorCode},
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mdns::{Mdns, ServiceMode},
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secure_channel::common::{complete_with_status, OpCode},
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tlv::{self, get_root_node_struct, FromTLV, OctetStr, TLVWriter, TagType, ToTLV},
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transport::{
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exchange::{Exchange, ExchangeId},
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packet::Packet,
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session::{CloneData, SessionMode},
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},
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utils::{epoch::Epoch, rand::Rand},
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};
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use log::{error, info};
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struct PaseSession {
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mdns_service_name: heapless::String<16>,
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verifier: VerifierData,
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}
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pub struct PaseMgr {
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session: Option<PaseSession>,
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timeout: Option<Timeout>,
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epoch: Epoch,
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rand: Rand,
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}
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impl PaseMgr {
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#[inline(always)]
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pub fn new(epoch: Epoch, rand: Rand) -> Self {
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Self {
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session: None,
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timeout: None,
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epoch,
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rand,
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}
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}
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pub fn is_pase_session_enabled(&self) -> bool {
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self.session.is_some()
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}
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pub fn enable_pase_session(
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&mut self,
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verifier: VerifierData,
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discriminator: u16,
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mdns: &dyn Mdns,
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) -> Result<(), Error> {
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let mut buf = [0; 8];
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(self.rand)(&mut buf);
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let num = u64::from_be_bytes(buf);
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let mut mdns_service_name = heapless::String::<16>::new();
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write!(&mut mdns_service_name, "{:016X}", num).unwrap();
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mdns.add(
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&mdns_service_name,
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ServiceMode::Commissionable(discriminator),
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)?;
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self.session = Some(PaseSession {
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mdns_service_name,
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verifier,
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});
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Ok(())
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}
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pub fn disable_pase_session(&mut self, mdns: &dyn Mdns) -> Result<(), Error> {
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if let Some(session) = self.session.as_ref() {
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mdns.remove(&session.mdns_service_name)?;
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}
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self.session = None;
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Ok(())
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}
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}
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// This file basically deals with the handlers for the PASE secure channel protocol
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// TLV extraction and encoding is done in this file.
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// We create a Spake2p object and set it up in the exchange-data. This object then
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// handles Spake2+ specific stuff.
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const PASE_DISCARD_TIMEOUT_SECS: Duration = Duration::from_secs(60);
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const SPAKE2_SESSION_KEYS_INFO: [u8; 11] = *b"SessionKeys";
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struct Timeout {
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start_time: Duration,
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exch_id: ExchangeId,
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}
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impl Timeout {
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fn new(exchange: &Exchange, epoch: Epoch) -> Self {
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Self {
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start_time: epoch(),
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exch_id: exchange.id().clone(),
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}
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}
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fn is_sess_expired(&self, epoch: Epoch) -> bool {
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epoch() - self.start_time > PASE_DISCARD_TIMEOUT_SECS
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}
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}
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pub struct Pake<'a> {
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pase: &'a RefCell<PaseMgr>,
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}
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impl<'a> Pake<'a> {
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pub const fn new(pase: &'a RefCell<PaseMgr>) -> Self {
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// TODO: Can any PBKDF2 calculation be pre-computed here
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Self { pase }
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}
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pub async fn handle(
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&mut self,
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exchange: &mut Exchange<'_>,
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rx: &mut Packet<'_>,
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tx: &mut Packet<'_>,
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mdns: &dyn Mdns,
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) -> Result<(), Error> {
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let mut spake2p = alloc!(Spake2P::new());
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self.handle_pbkdfparamrequest(exchange, rx, tx, &mut spake2p)
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.await?;
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self.handle_pasepake1(exchange, rx, tx, &mut spake2p)
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.await?;
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self.handle_pasepake3(exchange, rx, tx, mdns, &mut spake2p)
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.await
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}
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#[allow(non_snake_case)]
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async fn handle_pasepake3(
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&mut self,
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exchange: &mut Exchange<'_>,
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rx: &mut Packet<'_>,
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tx: &mut Packet<'_>,
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mdns: &dyn Mdns,
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spake2p: &mut Spake2P,
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) -> Result<(), Error> {
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rx.check_proto_opcode(OpCode::PASEPake3 as _)?;
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self.update_timeout(exchange, tx, true).await?;
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let cA = extract_pasepake_1_or_3_params(rx.as_slice())?;
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let (status_code, ke) = spake2p.handle_cA(cA);
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let clone_data = if status_code == SCStatusCodes::SessionEstablishmentSuccess {
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// Get the keys
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let ke = ke.ok_or(ErrorCode::Invalid)?;
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let mut session_keys: [u8; 48] = [0; 48];
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crypto::hkdf_sha256(&[], ke, &SPAKE2_SESSION_KEYS_INFO, &mut session_keys)
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.map_err(|_x| ErrorCode::NoSpace)?;
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// Create a session
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let data = spake2p.get_app_data();
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let peer_sessid: u16 = (data & 0xffff) as u16;
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let local_sessid: u16 = ((data >> 16) & 0xffff) as u16;
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let mut clone_data = CloneData::new(
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0,
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0,
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peer_sessid,
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local_sessid,
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exchange.with_session(|sess| Ok(sess.get_peer_addr()))?,
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SessionMode::Pase,
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);
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clone_data.dec_key.copy_from_slice(&session_keys[0..16]);
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clone_data.enc_key.copy_from_slice(&session_keys[16..32]);
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clone_data
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.att_challenge
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.copy_from_slice(&session_keys[32..48]);
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// Queue a transport mgr request to add a new session
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Some(clone_data)
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} else {
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None
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};
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if let Some(clone_data) = clone_data {
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// TODO: Handle NoSpace
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exchange.with_session_mgr_mut(|sess_mgr| sess_mgr.clone_session(&clone_data))?;
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self.pase.borrow_mut().disable_pase_session(mdns)?;
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}
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complete_with_status(exchange, tx, status_code, None).await?;
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Ok(())
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}
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#[allow(non_snake_case)]
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#[allow(clippy::await_holding_refcell_ref)]
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async fn handle_pasepake1(
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&mut self,
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exchange: &mut Exchange<'_>,
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rx: &mut Packet<'_>,
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tx: &mut Packet<'_>,
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spake2p: &mut Spake2P,
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) -> Result<(), Error> {
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rx.check_proto_opcode(OpCode::PASEPake1 as _)?;
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self.update_timeout(exchange, tx, false).await?;
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let pase = self.pase.borrow();
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let session = pase.session.as_ref().ok_or(ErrorCode::NoSession)?;
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let pA = extract_pasepake_1_or_3_params(rx.as_slice())?;
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let mut pB: [u8; 65] = [0; 65];
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let mut cB: [u8; 32] = [0; 32];
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spake2p.start_verifier(&session.verifier)?;
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spake2p.handle_pA(pA, &mut pB, &mut cB, pase.rand)?;
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// Generate response
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tx.reset();
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tx.set_proto_id(PROTO_ID_SECURE_CHANNEL);
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tx.set_proto_opcode(OpCode::PASEPake2 as u8);
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let mut tw = TLVWriter::new(tx.get_writebuf()?);
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let resp = Pake1Resp {
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pb: OctetStr(&pB),
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cb: OctetStr(&cB),
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};
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resp.to_tlv(&mut tw, TagType::Anonymous)?;
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drop(pase);
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exchange.exchange(tx, rx).await
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}
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#[allow(clippy::await_holding_refcell_ref)]
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async fn handle_pbkdfparamrequest(
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&mut self,
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exchange: &mut Exchange<'_>,
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rx: &mut Packet<'_>,
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tx: &mut Packet<'_>,
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spake2p: &mut Spake2P,
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) -> Result<(), Error> {
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rx.check_proto_opcode(OpCode::PBKDFParamRequest as _)?;
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self.update_timeout(exchange, tx, true).await?;
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let pase = self.pase.borrow();
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let session = pase.session.as_ref().ok_or(ErrorCode::NoSession)?;
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let root = tlv::get_root_node(rx.as_slice())?;
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let a = PBKDFParamReq::from_tlv(&root)?;
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if a.passcode_id != 0 {
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error!("Can't yet handle passcode_id != 0");
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Err(ErrorCode::Invalid)?;
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}
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let mut our_random: [u8; 32] = [0; 32];
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(self.pase.borrow().rand)(&mut our_random);
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let local_sessid = exchange.with_session_mgr_mut(|mgr| Ok(mgr.get_next_sess_id()))?;
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let spake2p_data: u32 = ((local_sessid as u32) << 16) | a.initiator_ssid as u32;
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spake2p.set_app_data(spake2p_data);
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// Generate response
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tx.reset();
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tx.set_proto_id(PROTO_ID_SECURE_CHANNEL);
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tx.set_proto_opcode(OpCode::PBKDFParamResponse as u8);
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let mut tw = TLVWriter::new(tx.get_writebuf()?);
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let mut resp = PBKDFParamResp {
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init_random: a.initiator_random,
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our_random: OctetStr(&our_random),
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local_sessid,
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params: None,
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};
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if !a.has_params {
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let params_resp = PBKDFParamRespParams {
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count: session.verifier.count,
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salt: OctetStr(&session.verifier.salt),
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};
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resp.params = Some(params_resp);
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}
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resp.to_tlv(&mut tw, TagType::Anonymous)?;
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spake2p.set_context(rx.as_slice(), tx.as_mut_slice())?;
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drop(pase);
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exchange.exchange(tx, rx).await
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}
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#[allow(clippy::await_holding_refcell_ref)]
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async fn update_timeout(
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&mut self,
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exchange: &mut Exchange<'_>,
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tx: &mut Packet<'_>,
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new: bool,
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) -> Result<(), Error> {
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self.check_session(exchange, tx).await?;
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let mut pase = self.pase.borrow_mut();
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if pase
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.timeout
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.as_ref()
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.map(|sd| sd.is_sess_expired(pase.epoch))
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.unwrap_or(false)
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{
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pase.timeout = None;
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}
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let status = if let Some(sd) = pase.timeout.as_mut() {
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if &sd.exch_id != exchange.id() {
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info!("Other PAKE session in progress");
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Some(SCStatusCodes::Busy)
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} else {
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None
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}
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} else if new {
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None
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} else {
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error!("PAKE session not found or expired");
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Some(SCStatusCodes::SessionNotFound)
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};
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if let Some(status) = status {
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drop(pase);
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complete_with_status(exchange, tx, status, None).await
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} else {
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pase.timeout = Some(Timeout::new(exchange, pase.epoch));
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Ok(())
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}
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}
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async fn check_session(
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&mut self,
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exchange: &mut Exchange<'_>,
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tx: &mut Packet<'_>,
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) -> Result<(), Error> {
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if self.pase.borrow().session.is_none() {
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error!("PASE not enabled");
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complete_with_status(exchange, tx, SCStatusCodes::InvalidParameter, None).await
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} else {
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Ok(())
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}
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}
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}
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#[derive(ToTLV)]
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#[tlvargs(start = 1)]
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struct Pake1Resp<'a> {
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pb: OctetStr<'a>,
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cb: OctetStr<'a>,
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}
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#[derive(ToTLV)]
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#[tlvargs(start = 1)]
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struct PBKDFParamRespParams<'a> {
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count: u32,
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salt: OctetStr<'a>,
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}
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#[derive(ToTLV)]
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#[tlvargs(start = 1)]
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struct PBKDFParamResp<'a> {
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init_random: OctetStr<'a>,
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our_random: OctetStr<'a>,
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local_sessid: u16,
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params: Option<PBKDFParamRespParams<'a>>,
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}
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#[allow(non_snake_case)]
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fn extract_pasepake_1_or_3_params(buf: &[u8]) -> Result<&[u8], Error> {
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let root = get_root_node_struct(buf)?;
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let pA = root.find_tag(1)?.slice()?;
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Ok(pA)
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}
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#[derive(FromTLV)]
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#[tlvargs(lifetime = "'a", start = 1)]
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struct PBKDFParamReq<'a> {
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initiator_random: OctetStr<'a>,
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initiator_ssid: u16,
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passcode_id: u16,
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has_params: bool,
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}
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