From be01ee2de0842f1f40a70a4339caf4e824253a17 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Damir=20Jeli=C4=87?= <poljar@termina.org.uk>
Date: Tue, 4 Aug 2020 12:31:56 +0200
Subject: [PATCH] crypto: Cancel the verification if we find a MAC mismatch.

---
 matrix_sdk_crypto/src/verification/sas/helpers.rs   | 12 ++++++------
 matrix_sdk_crypto/src/verification/sas/sas_state.rs |  7 +++++--
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/matrix_sdk_crypto/src/verification/sas/helpers.rs b/matrix_sdk_crypto/src/verification/sas/helpers.rs
index 33e01a53..34032aad 100644
--- a/matrix_sdk_crypto/src/verification/sas/helpers.rs
+++ b/matrix_sdk_crypto/src/verification/sas/helpers.rs
@@ -8,7 +8,8 @@ use matrix_sdk_common::{
         to_device::{send_event_to_device::Request as ToDeviceRequest, DeviceIdOrAllDevices},
     },
     events::{
-        key::verification::mac::MacEventContent, AnyToDeviceEventContent, EventType, ToDeviceEvent,
+        key::verification::{cancel::CancelCode, mac::MacEventContent},
+        AnyToDeviceEventContent, EventType, ToDeviceEvent,
     },
     identifiers::{DeviceId, UserId},
     uuid::Uuid,
@@ -142,8 +143,7 @@ pub fn receive_mac_event(
     ids: &SasIds,
     flow_id: &str,
     event: &ToDeviceEvent<MacEventContent>,
-) -> (Vec<Device>, Vec<String>) {
-    // TODO check the event and cancel if it isn't ok (sender, transaction id)
+) -> Result<(Vec<Device>, Vec<String>), CancelCode> {
     let mut verified_devices = Vec::new();
 
     let info = extra_mac_info_receive(&ids, flow_id);
@@ -155,7 +155,7 @@ pub fn receive_mac_event(
         .expect("Can't calculate SAS MAC");
 
     if keys != event.content.keys {
-        panic!("Keys mac mismatch")
+        return Err(CancelCode::KeyMismatch);
     }
 
     for (key_id, key_mac) in &event.content.mac {
@@ -182,13 +182,13 @@ pub fn receive_mac_event(
             {
                 verified_devices.push(ids.other_device.clone());
             } else {
-                // TODO cancel here
+                return Err(CancelCode::KeyMismatch);
             }
         }
         // TODO add an else branch for the master key here
     }
 
-    (verified_devices, vec![])
+    Ok((verified_devices, vec![]))
 }
 
 /// Get the extra info that will be used when we generate a MAC and need to send
diff --git a/matrix_sdk_crypto/src/verification/sas/sas_state.rs b/matrix_sdk_crypto/src/verification/sas/sas_state.rs
index ec09f8b7..d6c75fbb 100644
--- a/matrix_sdk_crypto/src/verification/sas/sas_state.rs
+++ b/matrix_sdk_crypto/src/verification/sas/sas_state.rs
@@ -562,7 +562,8 @@ impl SasState<KeyReceived> {
             &self.ids,
             &self.verification_flow_id,
             event,
-        );
+        )
+        .map_err(|c| self.clone().cancel(c))?;
 
         Ok(SasState {
             inner: self.inner,
@@ -606,12 +607,14 @@ impl SasState<Confirmed> {
     ) -> Result<SasState<Done>, SasState<Canceled>> {
         self.check_sender_and_txid(&event.sender, &event.content.transaction_id)
             .map_err(|c| self.clone().cancel(c))?;
+
         let (devices, master_keys) = receive_mac_event(
             &self.inner.lock().unwrap(),
             &self.ids,
             &self.verification_flow_id,
             event,
-        );
+        )
+        .map_err(|c| self.clone().cancel(c))?;
 
         Ok(SasState {
             inner: self.inner,