matrix-continuwuity: fix exploit in create_invite_route function (#472955)

diff --git a/src/api/server/invite.rs b/src/api/server/invite.rs

index 78a65fe8..d284fedd 100644

--- a/src/api/server/invite.rs

+++ b/src/api/server/invite.rs

@@ -61,6 +61,46 @@ pub(crate) async fn create_invite_route(

 	let mut signed_event = utils::to_canonical_object(&body.event)

 		.map_err(|_| err!(Request(InvalidParam("Invite event is invalid."))))?;

+	// Ensure this is a membership event

+	if signed_event

+		.get("type")

+		.expect("event must have a type")

+		.as_str()

+		.expect("type must be a string")

+		!= "m.room.member"

+	{

+		return Err!(Request(BadJson(

+			"Not allowed to send non-membership event to invite endpoint."

+		)));

+	}

+

+	let content: RoomMemberEventContent = serde_json::from_value(

+		signed_event

+			.get("content")

+			.ok_or_else(|| err!(Request(BadJson("Event missing content property"))))?

+			.clone()

+			.into(),

+	)

+	.map_err(|e| err!(Request(BadJson(warn!("Event content is empty or invalid: {e}")))))?;

+

+	// Ensure this is an invite membership event

+	if content.membership != MembershipState::Invite {

+		return Err!(Request(BadJson(

+			"Not allowed to send a non-invite membership event to invite endpoint."

+		)));

+	}

+

+	// Ensure the sending user isn't a lying bozo

+	let sender_server = signed_event

+		.get("sender")

+		.try_into()

+		.map(UserId::server_name)

+		.map_err(|e| err!(Request(InvalidParam("Invalid sender property: {e}"))))?;

+	if sender_server != body.origin() {

+		return Err!(Request(Forbidden("Sender's server does not match the origin server.",)));

+	}

+

+	// Ensure the target user belongs to this server

 	let recipient_user: OwnedUserId = signed_event

 		.get("state_key")

 		.try_into()

    hash = "sha256-UHlKAYgIkVtZJV+H2Xl7HssV03Q3XNxluMfLRY2e+Do=";

  };

  # https://forgejo.ellis.link/continuwuation/continuwuity/commit/b2bead67ac8bc45de9a612578f295e5b7fc6c2b5

  # https://forgejo.ellis.link/continuwuation/continuwuity/commit/7fa4fa98628593c1a963f5aa8dbc3657d604b047

  # this patch is probably unneeded with the next release

  patches = [ ./continuwuity-exploit-fix.diff ];

  cargoHash = "sha256-imfpl+72zlqeEREdTGFG3bsMdPTXe/sb1uGvMC6BGT0=";

  nativeBuildInputs = [