crypto: Don't share group sessions with blacklisted devices.

matrix_sdk_crypto/src/device.rs

@@ -131,11 +131,18 @@ impl Device {
         self.trust_state.load(Ordering::Relaxed)
     }
 
-    /// Is the device locally marked trusted.
+    /// Is the device locally marked as trusted.
     pub fn is_trusted(&self) -> bool {
         self.trust_state() == TrustState::Verified
     }
 
+    /// Is the device locally marked as blacklisted.
+    ///
+    /// Blacklisted devices won't receive any group sessions.
+    pub fn is_blacklisted(&self) -> bool {
+        self.trust_state() == TrustState::BlackListed
+    }
+
     /// Set the trust state of the device to the given state.
     ///
     /// Note: This should only done in the cryptostore where the trust state can

matrix_sdk_crypto/src/machine.rs

@@ -1014,9 +1014,11 @@ impl OlmMachine {
 
         for user_id in users {
             for device in self.store.get_user_devices(user_id).await?.devices() {
+                if !device.is_blacklisted() {
                     devices.push(device.clone());
                 }
             }
+        }
 
         let mut requests = Vec::new();
         let key_content = session.as_json().await;