events: Make ForwardedRoomKeyToDeviceEventContent non-exhaustive

ruma-events/src/forwarded_room_key.rs

@@ -5,7 +5,11 @@ use ruma_identifiers::{EventEncryptionAlgorithm, RoomId};
 use serde::{Deserialize, Serialize};
 
 /// The payload for `ForwardedRoomKeyEvent`.
+///
+/// To create an instance of this type, first create a `ForwardedRoomKeyToDeviceEventContentInit`
+/// and convert it via `ForwardedRoomKeyToDeviceEventContent::from` / `.into()`.
 #[derive(Clone, Debug, Deserialize, Serialize, BasicEventContent)]
+#[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
 #[ruma_event(type = "m.forwarded_room_key")]
 pub struct ForwardedRoomKeyToDeviceEventContent {
     /// The encryption algorithm the key in this event is to be used with.
@@ -38,3 +42,54 @@ pub struct ForwardedRoomKeyToDeviceEventContent {
     /// A's Curve25519 key between B and C.
     pub forwarding_curve25519_key_chain: Vec<String>,
 }
+
+/// Initial set of fields of `ForwardedRoomKeyToDeviceEventContent`.
+///
+/// This struct will not be updated even if additional fields are added to `ConditionalPushRule` in
+/// a new (non-breaking) release of the Matrix specification.
+#[derive(Debug)]
+pub struct ForwardedRoomKeyToDeviceEventContentInit {
+    /// The encryption algorithm the key in this event is to be used with.
+    pub algorithm: EventEncryptionAlgorithm,
+
+    /// The room where the key is used.
+    pub room_id: RoomId,
+
+    /// The Curve25519 key of the device which initiated the session originally.
+    pub sender_key: String,
+
+    /// The ID of the session that the key is for.
+    pub session_id: String,
+
+    /// The key to be exchanged.
+    pub session_key: String,
+
+    /// The Ed25519 key of the device which initiated the session originally.
+    ///
+    /// It is "claimed" because the receiving device has no way to tell that the original
+    /// room_key actually came from a device which owns the private part of this key unless
+    /// they have done device verification.
+    pub sender_claimed_ed25519_key: String,
+
+    /// Chain of Curve25519 keys.
+    ///
+    /// It starts out empty, but each time the key is forwarded to another device, the
+    /// previous sender in the chain is added to the end of the list. For example, if the
+    /// key is forwarded from A to B to C, this field is empty between A and B, and contains
+    /// A's Curve25519 key between B and C.
+    pub forwarding_curve25519_key_chain: Vec<String>,
+}
+
+impl From<ForwardedRoomKeyToDeviceEventContentInit> for ForwardedRoomKeyToDeviceEventContent {
+    fn from(init: ForwardedRoomKeyToDeviceEventContentInit) -> Self {
+        Self {
+            algorithm: init.algorithm,
+            room_id: init.room_id,
+            sender_key: init.sender_key,
+            session_id: init.session_id,
+            session_key: init.session_key,
+            sender_claimed_ed25519_key: init.sender_claimed_ed25519_key,
+            forwarding_curve25519_key_chain: init.forwarding_curve25519_key_chain,
+        }
+    }
+}