refactor(sdk-crypto): Room key sharing, introduce extensible strategy

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

@@ -2263,7 +2263,8 @@ pub(crate) mod tests {
         error::{EventError, SetRoomSettingsError},
         machine::{EncryptionSyncChanges, OlmMachine},
         olm::{
-            BackedUpRoomKey, ExportedRoomKey, InboundGroupSession, OutboundGroupSession, VerifyJson,
+            BackedUpRoomKey, CollectStrategy, ExportedRoomKey, InboundGroupSession,
+            OutboundGroupSession, VerifyJson,
         },
         store::{BackupDecryptionKey, Changes, CryptoStore, MemoryStore, RoomSettings},
         types::{
@@ -3083,8 +3084,10 @@ pub(crate) mod tests {
         let room_id = room_id!("!test:example.org");
 
         let encryption_settings = EncryptionSettings::default();
-        let encryption_settings =
-            EncryptionSettings { only_allow_trusted_devices: true, ..encryption_settings };
+        let encryption_settings = EncryptionSettings {
+            sharing_strategy: CollectStrategy::new_device_based(true),
+            ..encryption_settings
+        };
 
         let to_device_requests = alice
             .share_room_key(room_id, iter::once(bob.user_id()), encryption_settings)

crates/matrix-sdk-crypto/src/olm/group_sessions/mod.rs

@@ -17,12 +17,15 @@ use serde::{Deserialize, Serialize};
 
 mod inbound;
 mod outbound;
+mod share_strategy;
 
 pub use inbound::{InboundGroupSession, PickledInboundGroupSession};
 pub(crate) use outbound::ShareState;
 pub use outbound::{
     EncryptionSettings, OutboundGroupSession, PickledOutboundGroupSession, ShareInfo,
 };
+pub(crate) use share_strategy::{CollectRecipientsHelper, CollectRecipientsResult};
+pub use share_strategy::{CollectStrategy, DeviceBasedStrategy};
 use thiserror::Error;
 pub use vodozemac::megolm::{ExportedSessionKey, SessionKey};
 use vodozemac::{megolm::SessionKeyDecodeError, Curve25519PublicKey};

crates/matrix-sdk-crypto/src/olm/group_sessions/outbound.rs

@@ -42,7 +42,7 @@ pub use vodozemac::{
     PickleError,
 };
 
-use super::SessionCreationError;
+use super::{share_strategy::CollectStrategy, SessionCreationError};
 #[cfg(feature = "experimental-algorithms")]
 use crate::types::events::room::encrypted::MegolmV2AesSha2Content;
 use crate::{
@@ -85,10 +85,10 @@ pub struct EncryptionSettings {
     pub rotation_period_msgs: u64,
     /// The history visibility of the room when the session was created.
     pub history_visibility: HistoryVisibility,
-    /// Should untrusted devices receive the room key, or should they be
-    /// excluded from the conversation.
+    /// The strategy used to distribute the room keys to participant.
+    /// Default will send to all devices.
     #[serde(default)]
-    pub only_allow_trusted_devices: bool,
+    pub sharing_strategy: CollectStrategy,
 }
 
 impl Default for EncryptionSettings {
@@ -98,7 +98,7 @@ impl Default for EncryptionSettings {
             rotation_period: ROTATION_PERIOD,
             rotation_period_msgs: ROTATION_MESSAGES,
             history_visibility: HistoryVisibility::Shared,
-            only_allow_trusted_devices: false,
+            sharing_strategy: CollectStrategy::default(),
         }
     }
 }
@@ -122,7 +122,7 @@ impl EncryptionSettings {
             rotation_period,
             rotation_period_msgs,
             history_visibility,
-            only_allow_trusted_devices,
+            sharing_strategy: CollectStrategy::new_device_based(only_allow_trusted_devices),
         }
     }
 }