feat(sdk-crypto): Add Identity local tofu trust flag.

crates/matrix-sdk-crypto/src/identities/manager.rs

@@ -542,7 +542,7 @@ impl IdentityManager {
             *changed_private_identity = self.check_private_identity(&identity).await;
             Ok(identity.into())
         } else {
-            let identity = ReadOnlyUserIdentity::new(master_key, self_signing)?;
+            let identity = ReadOnlyUserIdentity::new(master_key, self_signing, true)?;
             Ok(identity.into())
         }
     }
@@ -1329,7 +1329,7 @@ pub(crate) mod tests {
     use std::ops::Deref;
 
     use futures_util::pin_mut;
-    use matrix_sdk_test::{async_test, response_from_file};
+    use matrix_sdk_test::{async_test, response_from_file, test_json};
     use ruma::{
         api::{client::keys::get_keys::v3::Response as KeysQueryResponse, IncomingResponse},
         device_id, user_id, TransactionId,
@@ -1893,4 +1893,92 @@ pub(crate) mod tests {
             .unwrap()
             .unwrap();
     }
+
+    #[async_test]
+    async fn test_manager_identity_updates() {
+        use test_json::keys_query_sets::IdentityChangeDataSet as DataSet;
+
+        let manager = manager_test_helper(user_id(), device_id()).await;
+        let other_user = DataSet::user_id();
+        let devices = manager.store.get_user_devices(other_user).await.unwrap();
+        assert_eq!(devices.devices().count(), 0);
+
+        let identity = manager.store.get_user_identity(other_user).await.unwrap();
+        assert!(identity.is_none());
+
+        manager
+            .receive_keys_query_response(
+                &TransactionId::new(),
+                &DataSet::key_query_with_identity_a(),
+            )
+            .await
+            .unwrap();
+
+        let identity = manager.store.get_user_identity(other_user).await.unwrap().unwrap();
+        let other_identity = identity.other().unwrap();
+
+        // There should be now an identity and it should be tofu trusted as it is the
+        // first time we see an identity for that user
+        assert!(other_identity.is_tofu_trusted());
+        let first_device = manager
+            .store
+            .get_readonly_device(other_user, DataSet::first_device_id())
+            .await
+            .unwrap()
+            .unwrap();
+        assert!(first_device.is_cross_signed_by_owner(&identity));
+
+        // We receive a new keys update for that user, with a new identity
+        manager
+            .receive_keys_query_response(
+                &TransactionId::new(),
+                &DataSet::key_query_with_identity_b(),
+            )
+            .await
+            .unwrap();
+
+        let identity = manager.store.get_user_identity(other_user).await.unwrap().unwrap();
+        let other_identity = identity.other().unwrap();
+
+        // The previous tofu identity has been replaced, it is not tofu trusted until
+        // validated by the user
+        assert!(!other_identity.is_tofu_trusted());
+
+        let second_device = manager
+            .store
+            .get_readonly_device(other_user, DataSet::second_device_id())
+            .await
+            .unwrap()
+            .unwrap();
+        // There is a new device signed by the new identity
+        assert!(second_device.is_cross_signed_by_owner(&identity));
+
+        // The first device should not be signed by the new identity
+        let first_device = manager
+            .store
+            .get_readonly_device(other_user, DataSet::first_device_id())
+            .await
+            .unwrap()
+            .unwrap();
+        assert!(!first_device.is_cross_signed_by_owner(&identity));
+
+        let remember_previous_identity = other_identity.clone();
+        // We receive a new keys update for that user, with no identity anymore
+        // Notice that there is no server API to delete identity, but we want to test
+        // here that a home server cannot clear the identity and serve a new one
+        // after that would get automatically tofu trusted.
+        manager
+            .receive_keys_query_response(
+                &TransactionId::new(),
+                &DataSet::key_query_with_identity_no_identity(),
+            )
+            .await
+            .unwrap();
+
+        let identity = manager.store.get_user_identity(other_user).await.unwrap().unwrap();
+        let other_identity = identity.other().unwrap();
+
+        assert_eq!(other_identity, &remember_previous_identity);
+        assert!(!other_identity.is_tofu_trusted());
+    }
 }

crates/matrix-sdk-crypto/src/identities/user.rs

@@ -375,6 +375,24 @@ pub struct ReadOnlyUserIdentity {
     user_id: OwnedUserId,
     pub(crate) master_key: Arc<MasterPubkey>,
     self_signing_key: Arc<SelfSigningPubkey>,
+    /// The first time an identity is seen for a given user it will be marked as
+    /// tofu trusted. If a new identity is detected for that user, we must
+    /// ensure that this change has been shown and validated by the user. If
+    /// this boolean is set to `false`, sharing room keys to this user might
+    /// fail depending on the room key sharing strategy.
+    #[serde(
+        default = "tofu_trusted_default",
+        serialize_with = "atomic_bool_serializer",
+        deserialize_with = "atomic_bool_deserializer"
+    )]
+    tofu_trusted: Arc<AtomicBool>,
+}
+
+// The tofu_trusted field introduced a new field in the database
+// schema, for backwards compatibility we assume that if the identity is
+// already in the database we considered it as tofu trusted.
+fn tofu_trusted_default() -> Arc<AtomicBool> {
+    Arc::new(true.into())
 }
 
 impl PartialEq for ReadOnlyUserIdentity {
@@ -395,6 +413,7 @@ impl PartialEq for ReadOnlyUserIdentity {
             && self.master_key == other.master_key
             && self.self_signing_key == other.self_signing_key
             && self.master_key.signatures() == other.master_key.signatures()
+            && self.is_tofu_trusted() == other.is_tofu_trusted()
     }
 }
 
@@ -406,19 +425,22 @@ impl ReadOnlyUserIdentity {
     /// * `master_key` - The master key of the user identity.
     ///
     /// * `self signing key` - The self signing key of user identity.
+    /// * `tofu_trusted` - Is this identity tofu trusted.
     ///
     /// Returns a `SignatureError` if the self signing key fails to be correctly
     /// verified by the given master key.
     pub(crate) fn new(
         master_key: MasterPubkey,
         self_signing_key: SelfSigningPubkey,
+        tofu_trusted: bool,
     ) -> Result<Self, SignatureError> {
         master_key.verify_subkey(&self_signing_key)?;
 
         Ok(Self {
             user_id: master_key.user_id().into(),
             master_key: master_key.into(),
             self_signing_key: self_signing_key.into(),
+            tofu_trusted: AtomicBool::new(tofu_trusted).into(),
         })
     }
 
@@ -429,7 +451,12 @@ impl ReadOnlyUserIdentity {
         let self_signing_key =
             identity.self_signing_key.lock().await.as_ref().unwrap().public_key().clone().into();
 
-        Self { user_id: identity.user_id().into(), master_key, self_signing_key }
+        Self {
+            user_id: identity.user_id().into(),
+            master_key,
+            self_signing_key,
+            tofu_trusted: AtomicBool::new(true).into(),
+        }
     }
 
     /// Get the user id of this identity.
@@ -447,6 +474,21 @@ impl ReadOnlyUserIdentity {
         &self.self_signing_key
     }
 
+    /// Check if our identity is verified.
+    pub fn is_tofu_trusted(&self) -> bool {
+        self.tofu_trusted.load(Ordering::SeqCst)
+    }
+
+    /// Mark this identity as tofu trusted by the user
+    pub fn mark_as_tofu_trusted(&self) {
+        self.tofu_trusted.store(true, Ordering::SeqCst)
+    }
+
+    #[cfg(test)]
+    pub fn mark_as_not_tofu_trusted(&self) {
+        self.tofu_trusted.store(false, Ordering::SeqCst)
+    }
+
     /// Update the identity with a new master key and self signing key.
     ///
     /// # Arguments
@@ -465,7 +507,7 @@ impl ReadOnlyUserIdentity {
     ) -> Result<bool, SignatureError> {
         master_key.verify_subkey(&self_signing_key)?;
 
-        let new = Self::new(master_key, self_signing_key)?;
+        let new = Self::new(master_key, self_signing_key, false)?;
         let changed = new != *self;
 
         *self = new;
@@ -776,8 +818,12 @@ pub(crate) mod testing {
         let self_signing: CrossSigningKey =
             response.self_signing_keys.get(user_id).unwrap().deserialize_as().unwrap();
 
-        ReadOnlyUserIdentity::new(master_key.try_into().unwrap(), self_signing.try_into().unwrap())
-            .unwrap()
+        ReadOnlyUserIdentity::new(
+            master_key.try_into().unwrap(),
+            self_signing.try_into().unwrap(),
+            true,
+        )
+        .unwrap()
     }
 }