fix: do not allow non-members to change ephemeral timer settings

src/ephemeral/ephemeral_tests.rs

@@ -1,7 +1,11 @@
 use super::*;
-use crate::chat::{marknoticed_chat, set_muted, ChatVisibility, MuteDuration};
+use crate::chat::{
+    add_contact_to_chat, marknoticed_chat, remove_contact_from_chat, set_muted, ChatVisibility,
+    MuteDuration,
+};
 use crate::config::Config;
 use crate::constants::DC_CHAT_ID_ARCHIVED_LINK;
+use crate::contact::Contact;
 use crate::download::DownloadState;
 use crate::location;
 use crate::message::markseen_msgs;
@@ -779,3 +783,39 @@ async fn test_archived_ephemeral_timer() -> Result<()> {
 
     Ok(())
 }
+
+/// Tests that non-members cannot change ephemeral timer settings.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_ephemeral_timer_non_member() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+
+    let alice_bob_contact_id = Contact::create(alice, "Bob", "bob@example.net").await?;
+    let alice_chat_id =
+        create_group_chat(alice, ProtectionStatus::Unprotected, "Group name").await?;
+    add_contact_to_chat(alice, alice_chat_id, alice_bob_contact_id).await?;
+    send_text_msg(alice, alice_chat_id, "Hi!".to_string()).await?;
+
+    let sent = alice.pop_sent_msg().await;
+    let bob_chat_id = bob.recv_msg(&sent).await.chat_id;
+
+    // Bob wants to modify the timer.
+    bob_chat_id.accept(bob).await?;
+    bob_chat_id
+        .set_ephemeral_timer(bob, Timer::Enabled { duration: 60 })
+        .await?;
+    let sent_ephemeral_timer_change = bob.pop_sent_msg().await;
+
+    // Alice removes Bob before receiving the timer change.
+    remove_contact_from_chat(alice, alice_chat_id, alice_bob_contact_id).await?;
+    alice.recv_msg(&sent_ephemeral_timer_change).await;
+
+    // Timer is not changed because Bob is not a member.
+    assert_eq!(
+        alice_chat_id.get_ephemeral_timer(alice).await?,
+        Timer::Disabled
+    );
+
+    Ok(())
+}

src/receive_imf.rs

@@ -1292,8 +1292,18 @@ async fn add_parts(
         && !mime_parser.parts.is_empty()
         && chat_id.get_ephemeral_timer(context).await? != ephemeral_timer
     {
+        let chat_contacts =
+            HashSet::<ContactId>::from_iter(chat::get_chat_contacts(context, chat_id).await?);
+        let is_from_in_chat =
+            !chat_contacts.contains(&ContactId::SELF) || chat_contacts.contains(&from_id);
+
         info!(context, "Received new ephemeral timer value {ephemeral_timer:?} for chat {chat_id}, checking if it should be applied.");
-        if is_dc_message == MessengerMessage::Yes
+        if !is_from_in_chat {
+            warn!(
+                context,
+                "Ignoring ephemeral timer change to {ephemeral_timer:?} for chat {chat_id} because sender {from_id} is not a member.",
+            );
+        } else if is_dc_message == MessengerMessage::Yes
             && get_previous_message(context, mime_parser)
                 .await?
                 .map(|p| p.ephemeral_timer)