fix: determine whether a message is an own message by looking at signature. multiple devices can temporarly have different sets of self addresses, and still need to properly recognize incoming versus outgoing messages. Disclaimer: some LLM tooling was initially involved but i went over everything by hand, and also addressed review comments.

src/mimeparser.rs

@@ -373,7 +373,7 @@ impl MimeMessage {
         hop_info += "\n\n";
         hop_info += &dkim_results.to_string();
 
-        let incoming = !context.is_self_addr(&from.addr).await?;
+        let from_is_not_self_addr = !context.is_self_addr(&from.addr).await?;
 
         let mut aheader_values = mail.headers.get_all_values(HeaderDef::Autocrypt.into());
 
@@ -438,7 +438,7 @@ impl MimeMessage {
         };
 
         let mut autocrypt_header = None;
-        if incoming {
+        if from_is_not_self_addr {
             // See `get_all_addresses_from_header()` for why we take the last valid header.
             for val in aheader_values.iter().rev() {
                 autocrypt_header = match Aheader::from_str(val) {
@@ -469,7 +469,7 @@ impl MimeMessage {
             None
         };
 
-        let mut public_keyring = if incoming {
+        let mut public_keyring = if from_is_not_self_addr {
             if let Some(autocrypt_header) = autocrypt_header {
                 vec![autocrypt_header.public_key]
             } else {
@@ -654,6 +654,15 @@ impl MimeMessage {
             .into_iter()
             .last()
             .map(|(fp, recipient_fps)| (fp, recipient_fps.into_iter().collect::<HashSet<_>>()));
+
+        let incoming = if let Some((ref sig_fp, _)) = signature {
+            sig_fp.hex() != key::self_fingerprint(context).await?
+        } else {
+            // rare case of getting a cleartext message
+            // so we determine 'incoming' flag by From-address
+            from_is_not_self_addr
+        };
+
         let mut parser = MimeMessage {
             parts: Vec::new(),
             headers,

src/receive_imf/receive_imf_tests.rs

@@ -13,9 +13,10 @@ use crate::constants::DC_GCL_FOR_FORWARDING;
 use crate::contact;
 use crate::imap::prefetch_should_download;
 use crate::imex::{ImexMode, imex};
+use crate::key;
 use crate::securejoin::get_securejoin_qr;
 use crate::test_utils::{
-    E2EE_INFO_MSGS, TestContext, TestContextManager, get_chat_msg, mark_as_verified,
+    E2EE_INFO_MSGS, TestContext, TestContextManager, alice_keypair, get_chat_msg, mark_as_verified,
 };
 use crate::tools::{SystemTime, time};
 
@@ -5561,3 +5562,31 @@ async fn test_calendar_alternative() -> Result<()> {
 
     Ok(())
 }
+
+/// Tests that outgoing encrypted messages are detected
+/// by verifying own signature, completely ignoring From address.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_outgoing_determined_by_signature() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+
+    // alice_dev2: same key, different address.
+    let different_from = "very@different.from";
+    assert!(!alice.is_self_addr(different_from).await?);
+    let alice_dev2 = &tcm.unconfigured().await;
+    alice_dev2.configure_addr(different_from).await;
+    key::store_self_keypair(alice_dev2, &alice_keypair()).await?;
+    assert_ne!(
+        alice.get_config(Config::Addr).await?.unwrap(),
+        different_from
+    );
+
+    // Send message from alice_dev2 and check alice sees it as outgoing
+    let chat_id = alice_dev2.create_chat_id(bob).await;
+    let sent_msg = alice_dev2.send_text(chat_id, "hello from new device").await;
+    let msg = alice.recv_msg(&sent_msg).await;
+    assert_eq!(msg.state, MessageState::OutDelivered);
+
+    Ok(())
+}