fix(crypto): Redecrypt non-UTD messages to remove no-longer-relevant warning shields (#4644)

Fixes element-hq/element-meta#2697
Fixes element-hq/crypto-internal#398

I'm sorry it's a big change. I've tried to break it into decent commits,
and I did a couple of preparatory PRs to make it less painful, but it's
still a bit to get your head around.

The basic idea is that when a session is updated and we call
`retry_event_decryption`, we don't only look at UTDs any more - now we
also look at decrypted events, and re-request their `EncryptionInfo`, in
case it has improved.

---------

Signed-off-by: Andy Balaam <[email protected]>
Co-authored-by: Richard van der Hoff <[email protected]>
Co-authored-by: Benjamin Bouvier <[email protected]>

Author: 3 people

crates/matrix-sdk-base/src/event_cache/store/integration_tests.rs

@@ -48,6 +48,7 @@ pub fn make_test_event(room_id: &RoomId, content: &str) -> TimelineEvent {
             sender_claimed_keys: Default::default(),
         },
         verification_state: VerificationState::Verified,
+        session_id: Some("mysessionid9".to_owned()),
     };
 
     let event = EventFactory::new()

crates/matrix-sdk-common/src/deserialized_responses.rs

@@ -302,6 +302,9 @@ pub struct EncryptionInfo {
     /// Callers that persist this should mark the state as dirty when a device
     /// change is received down the sync.
     pub verification_state: VerificationState,
+    /// The Megolm session ID that was used to encrypt this event, or None if
+    /// this info was stored before we collected this data.
+    pub session_id: Option<String>,
 }
 
 /// Represents a matrix room event that has been returned from `/sync`,
@@ -540,6 +543,19 @@ impl TimelineEventKind {
             TimelineEventKind::PlainText { event } => event,
         }
     }
+
+    /// The Megolm session ID that was used to send this event, if it was
+    /// encrypted.
+    pub fn session_id(&self) -> Option<&str> {
+        match self {
+            TimelineEventKind::Decrypted(decrypted_room_event) => {
+                decrypted_room_event.encryption_info.session_id.as_ref()
+            }
+            TimelineEventKind::UnableToDecrypt { utd_info, .. } => utd_info.session_id.as_ref(),
+            TimelineEventKind::PlainText { .. } => None,
+        }
+        .map(String::as_str)
+    }
 }
 
 #[cfg(not(tarpaulin_include))]
@@ -1042,6 +1058,7 @@ mod tests {
                         sender_claimed_keys: Default::default(),
                     },
                     verification_state: VerificationState::Verified,
+                    session_id: Some("xyz".to_owned()),
                 },
                 unsigned_encryption_info: Some(BTreeMap::from([(
                     UnsignedEventLocation::RelationsReplace,
@@ -1080,6 +1097,7 @@ mod tests {
                                 }
                             },
                             "verification_state": "Verified",
+                            "session_id": "xyz",
                         },
                         "unsigned_encryption_info": {
                             "RelationsReplace": {"UnableToDecrypt": {
@@ -1128,6 +1146,7 @@ mod tests {
             event.encryption_info().unwrap().algorithm_info,
             AlgorithmInfo::MegolmV1AesSha2 { .. }
         );
+        assert_eq!(event.encryption_info().unwrap().session_id, None);
 
         // Test that the previous format, with an undecryptable unsigned event, can also
         // be deserialized.
@@ -1364,6 +1383,7 @@ mod tests {
                 sender_claimed_keys: Default::default(),
             },
             verification_state: VerificationState::Verified,
+            session_id: Some("mysessionid76".to_owned()),
         };
 
         with_settings!({ sort_maps => true, prepend_module_to_snapshot => false }, {
@@ -1393,6 +1413,7 @@ mod tests {
                         ]),
                     },
                     verification_state: VerificationState::Verified,
+                    session_id: Some("mysessionid112".to_owned()),
                 },
                 unsigned_encryption_info: Some(BTreeMap::from([(
                     UnsignedEventLocation::RelationsThreadLatestEvent,

crates/matrix-sdk-common/src/snapshots/snapshot_test_encryption_info.snap

@@ -12,5 +12,6 @@ expression: info
       "sender_claimed_keys": {}
     }
   },
-  "verification_state": "Verified"
+  "verification_state": "Verified",
+  "session_id": "mysessionid76"
 }

crates/matrix-sdk-common/src/snapshots/snapshot_test_sync_timeline_event.snap

@@ -17,6 +17,7 @@ expression: "serde_json::to_value(&room_event).unwrap()"
         },
         "sender": "@sender:example.com",
         "sender_device": "ABCDEFGHIJ",
+        "session_id": "mysessionid112",
         "verification_state": "Verified"
       },
       "event": {

crates/matrix-sdk-crypto/src/machine/mod.rs

@@ -1671,6 +1671,7 @@ impl OlmMachine {
                     .collect(),
             },
             verification_state,
+            session_id: Some(session.session_id().to_owned()),
         })
     }