fix: don't leak Group-ID in Message-ID

Chat assignment based on In-Reply-To and References works good enough
even if the message cannot be decrypted.

src/chat.rs

@@ -1795,13 +1795,7 @@ impl Chat {
         let mut location_id = 0;
 
         let from = context.get_primary_self_addr().await?;
-        let new_rfc724_mid = {
-            let grpid = match self.typ {
-                Chattype::Group => Some(self.grpid.as_str()),
-                _ => None,
-            };
-            create_outgoing_rfc724_mid(grpid, &from)
-        };
+        let new_rfc724_mid = create_outgoing_rfc724_mid(&from);
 
         if self.typ == Chattype::Single {
             if let Some(id) = context
@@ -4151,7 +4145,7 @@ pub async fn add_device_msg_with_importance(
     if let Some(msg) = msg {
         chat_id = ChatId::get_for_contact(context, ContactId::DEVICE).await?;
 
-        let rfc724_mid = create_outgoing_rfc724_mid(None, "@device");
+        let rfc724_mid = create_outgoing_rfc724_mid("@device");
         prepare_msg_blob(context, msg).await?;
 
         let timestamp_sent = create_smeared_timestamp(context);
@@ -4291,7 +4285,7 @@ pub(crate) async fn add_info_msg_with_cmd(
     parent: Option<&Message>,
     from_id: Option<ContactId>,
 ) -> Result<MsgId> {
-    let rfc724_mid = create_outgoing_rfc724_mid(None, "@device");
+    let rfc724_mid = create_outgoing_rfc724_mid("@device");
     let ephemeral_timer = chat_id.get_ephemeral_timer(context).await?;
 
     let mut param = Params::new();
@@ -5932,11 +5926,11 @@ mod tests {
         // Alice has an SMTP-server replacing the `Message-ID:`-header (as done eg. by outlook.com).
         let sent_msg = alice.pop_sent_msg().await;
         let msg = sent_msg.payload();
-        assert_eq!(msg.match_indices("Message-ID: <Gr.").count(), 2);
-        assert_eq!(msg.match_indices("References: <Gr.").count(), 1);
-        let msg = msg.replace("Message-ID: <Gr.", "Message-ID: <XXX");
-        assert_eq!(msg.match_indices("Message-ID: <Gr.").count(), 0);
-        assert_eq!(msg.match_indices("References: <Gr.").count(), 1);
+        assert_eq!(msg.match_indices("Message-ID: <Mr.").count(), 2);
+        assert_eq!(msg.match_indices("References: <Mr.").count(), 1);
+        let msg = msg.replace("Message-ID: <Mr.", "Message-ID: <XXX");
+        assert_eq!(msg.match_indices("Message-ID: <Mr.").count(), 0);
+        assert_eq!(msg.match_indices("References: <Mr.").count(), 1);
 
         // Bob receives this message, he may detect group by `References:`- or `Chat-Group:`-header
         receive_imf(&bob, msg.as_bytes(), false).await.unwrap();
@@ -5953,7 +5947,7 @@ mod tests {
         send_text_msg(&bob, bob_chat.id, "ho!".to_string()).await?;
         let sent_msg = bob.pop_sent_msg().await;
         let msg = sent_msg.payload();
-        let msg = msg.replace("Message-ID: <Gr.", "Message-ID: <XXX");
+        let msg = msg.replace("Message-ID: <Mr.", "Message-ID: <XXX");
         let msg = msg.replace("Chat-", "XXXX-");
         assert_eq!(msg.match_indices("Chat-").count(), 0);
 

src/context.rs

@@ -1359,7 +1359,7 @@ mod tests {
              \n\
              hello\n",
             contact.get_addr(),
-            create_outgoing_rfc724_mid(None, contact.get_addr())
+            create_outgoing_rfc724_mid(contact.get_addr())
         );
         println!("{msg}");
         receive_imf(t, msg.as_bytes(), false).await.unwrap();

src/mimefactory.rs

@@ -551,7 +551,7 @@ impl<'a> MimeFactory<'a> {
 
         let rfc724_mid = match self.loaded {
             Loaded::Message { .. } => self.msg.rfc724_mid.clone(),
-            Loaded::Mdn { .. } => create_outgoing_rfc724_mid(None, &self.from_addr),
+            Loaded::Mdn { .. } => create_outgoing_rfc724_mid(&self.from_addr),
         };
         let rfc724_mid_headervalue = render_rfc724_mid(&rfc724_mid);
         let rfc724_mid_header = Header::new("Message-ID".into(), rfc724_mid_headervalue);

src/tools.rs

@@ -281,15 +281,12 @@ pub(crate) fn create_id() -> String {
 /// - this function is called for all outgoing messages.
 /// - the message ID should be globally unique
 /// - do not add a counter or any private data as this leaks information unnecessarily
-pub(crate) fn create_outgoing_rfc724_mid(grpid: Option<&str>, from_addr: &str) -> String {
+pub(crate) fn create_outgoing_rfc724_mid(from_addr: &str) -> String {
     let hostname = from_addr
         .find('@')
         .and_then(|k| from_addr.get(k..))
         .unwrap_or("@nohost");
-    match grpid {
-        Some(grpid) => format!("Gr.{}.{}{}", grpid, create_id(), hostname),
-        None => format!("Mr.{}.{}{}", create_id(), create_id(), hostname),
-    }
+    format!("Mr.{}.{}{}", create_id(), create_id(), hostname)
 }
 
 /// Extract the group id (grpid) from a message id (mid)
@@ -1013,21 +1010,10 @@ DKIM Results: Passed=true, Works=true, Allow_Keychange=true";
 
     #[test]
     fn test_create_outgoing_rfc724_mid() {
-        // create a normal message-id
-        let mid = create_outgoing_rfc724_mid(None, "foo@bar.de");
+        let mid = create_outgoing_rfc724_mid("foo@bar.de");
         assert!(mid.starts_with("Mr."));
         assert!(mid.ends_with("bar.de"));
         assert!(extract_grpid_from_rfc724_mid(mid.as_str()).is_none());
-
-        // create a message-id containing a group-id
-        let grpid = create_id();
-        let mid = create_outgoing_rfc724_mid(Some(&grpid), "foo@bar.de");
-        assert!(mid.starts_with("Gr."));
-        assert!(mid.ends_with("bar.de"));
-        assert_eq!(
-            extract_grpid_from_rfc724_mid(mid.as_str()),
-            Some(grpid.as_str())
-        );
     }
 
     #[test]