crypto: Error when sending keys to previously-verified users with identity-based strategy

bindings/matrix-sdk-ffi/CHANGELOG.md

@@ -2,6 +2,16 @@
 
 Breaking changes:
 
+- `EventSendState` now has two additional variants: `CrossSigningNotSetup` and
+  `SendingFromUnverifiedDevice`. These indicate that your own device is not
+  properly cross-signed, which is a requirement when using the identity-based
+  strategy, and can only be returned when using the identity-based strategy.
+
+  In addition, the `VerifiedUserHasUnsignedDevice` and
+  `VerifiedUserChangedIdentity` variants can be returned when using the
+  identity-based strategy, in addition to when using the device-based strategy
+  with `error_on_verified_user_problem` is set.
+
 - `EventSendState` now has two additional variants: `VerifiedUserHasUnsignedDevice` and
   `VerifiedUserChangedIdentity`. These reflect problems with verified users in the room
   and as such can only be returned when the room key recipient strategy has

bindings/matrix-sdk-ffi/src/timeline/mod.rs

@@ -918,12 +918,21 @@ pub enum EventSendState {
     ///
     /// Happens only when the room key recipient strategy (as set by
     /// [`ClientBuilder::room_key_recipient_strategy`]) has
-    /// [`error_on_verified_user_problem`](CollectStrategy::DeviceBasedStrategy::error_on_verified_user_problem) set.
+    /// [`error_on_verified_user_problem`](CollectStrategy::DeviceBasedStrategy::error_on_verified_user_problem)
+    /// set, or when using [`CollectStrategy::IdentityBasedStrategy`].
     VerifiedUserChangedIdentity {
         /// The users that were previously verified, but are no longer
         users: Vec<String>,
     },
 
+    /// The user does not have cross-signing set up, but
+    /// [`CollectStrategy::IdentityBasedStrategy`] was used.
+    CrossSigningNotSetup,
+
+    /// The current device is not verified, but
+    /// [`CollectStrategy::IdentityBasedStrategy`] was used.
+    SendingFromUnverifiedDevice,
+
     /// The local event has been sent to the server, but unsuccessfully: The
     /// sending has failed.
     SendingFailed {
@@ -977,6 +986,10 @@ fn event_send_state_from_sending_failed(error: &Error, is_recoverable: bool) ->
             VerifiedUserChangedIdentity(bad_users) => EventSendState::VerifiedUserChangedIdentity {
                 users: bad_users.iter().map(|user_id| user_id.to_string()).collect(),
             },
+
+            CrossSigningNotSetup => EventSendState::CrossSigningNotSetup,
+
+            SendingFromUnverifiedDevice => EventSendState::SendingFromUnverifiedDevice,
         },
 
         _ => EventSendState::SendingFailed { error: error.to_string(), is_recoverable },

crates/matrix-sdk-crypto/CHANGELOG.md

@@ -56,13 +56,19 @@ Breaking changes:
   `OlmMachine::share_room_key` to fail with an error if any verified users on
   the recipient list have unsigned devices, or are no lonver verified.
 
+  When `CallectStrategy::IdentityBasedStrategy` is used,
+  `OlmMachine::share_room_key` will fail with an error if any verified users on
+  the recipient list are no longer verified, or if our own device is not
+  properly cross-signed.
+
   Also remove `CollectStrategy::new_device_based`: callers should construct a
   `CollectStrategy::DeviceBasedStrategy` directly.
 
   `EncryptionSettings::new` now takes a `CollectStrategy` argument, instead of
   a list of booleans.
   ([#3810](https://github.com/matrix-org/matrix-rust-sdk/pull/3810))
   ([#3816](https://github.com/matrix-org/matrix-rust-sdk/pull/3816))
+  ([#3896](https://github.com/matrix-org/matrix-rust-sdk/pull/3896))
 
 - Remove the method `OlmMachine::clear_crypto_cache()`, crypto stores are not
   supposed to have any caches anymore.

crates/matrix-sdk-crypto/src/error.rs

@@ -391,7 +391,7 @@ pub enum SessionRecipientCollectionError {
     ///
     /// Happens only with [`CollectStrategy::DeviceBasedStrategy`] when
     /// [`error_on_verified_user_problem`](`CollectStrategy::DeviceBasedStrategy::error_on_verified_user_problem`)
-    /// is true.
+    /// is true, or with [`CollectStrategy::IdentityBasedStrategy`].
     ///
     /// In order to resolve this, the user can:
     ///
@@ -407,4 +407,24 @@ pub enum SessionRecipientCollectionError {
     /// The caller can then retry the encryption operation.
     #[error("one or more users that were verified have changed their identity")]
     VerifiedUserChangedIdentity(Vec<OwnedUserId>),
+
+    /// Cross-signing has not been configured on our own identity.
+    ///
+    /// Happens only with [`CollectStrategy::IdentityBasedStrategy`].
+    /// (Cross-signing is required for encryption when using
+    /// `IdentityBasedStrategy`.) Apps should detect this condition and prevent
+    /// sending in the UI rather than waiting for this error to be returned when
+    /// encrypting.
+    #[error("Encryption failed because cross-signing is not set up on your account")]
+    CrossSigningNotSetup,
+
+    /// The current device has not been cross-signed by our own identity.
+    ///
+    /// Happens only with [`CollectStrategy::IdentityBasedStrategy`].
+    /// (Cross-signing is required for encryption when using
+    /// `IdentityBasedStrategy`.) Apps should detect this condition and prevent
+    /// sending in the UI rather than waiting for this error to be returned when
+    /// encrypting.
+    #[error("Encryption failed because your device is not verified")]
+    SendingFromUnverifiedDevice,
 }