fix: use protected Date header when available

Author: link2xt

Diff for: src/mimeparser.rs

@@ -264,7 +264,7 @@ impl MimeMessage {
                     // messages are shown as unencrypted anyway.
 
                     timestamp_sent =
-                        Self::get_timestamp_sent(&mail.headers, timestamp_sent, timestamp_rcvd);
+                        Self::get_timestamp_sent(&part.headers, timestamp_sent, timestamp_rcvd);
                     MimeMessage::merge_headers(
                         context,
                         &mut headers,
@@ -345,6 +345,18 @@ impl MimeMessage {
                     }
 
                     decrypted_msg = Some(msg);
+
+                    if let Some(protected_timestamp_sent) = decrypted_mail
+                        .headers
+                        .get_header_value(HeaderDef::Date)
+                        .and_then(|v| mailparse::dateparse(&v).ok())
+                    {
+                        timestamp_sent = min(
+                            protected_timestamp_sent,
+                            timestamp_rcvd + constants::TIMESTAMP_SENT_TOLERANCE,
+                        )
+                    }
+
                     if let Some(protected_aheader_value) = decrypted_mail
                         .headers
                         .get_header_value(HeaderDef::Autocrypt)

Diff for: src/mimeparser/mimeparser_tests.rs

@@ -1982,3 +1982,32 @@ async fn test_chat_edit_imf_header() -> Result<()> {
 
     Ok(())
 }
+
+/// Tests that timestamp of encrypted but not signed message is protected.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_protected_date() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+
+    alice.set_config(Config::SignUnencrypted, Some("1")).await?;
+
+    let alice_chat = alice.create_email_chat(bob).await;
+    let alice_msg_id = chat::send_text_msg(alice, alice_chat.id, "Hello!".to_string()).await?;
+    let alice_msg = Message::load_from_db(alice, alice_msg_id).await?;
+    assert_eq!(alice_msg.get_showpadlock(), false);
+
+    let mut sent_msg = alice.pop_sent_msg().await;
+    sent_msg.payload = sent_msg.payload.replacen(
+        "Date:",
+        "Date: Wed, 17 Mar 2021 14:30:53 +0100 (CET)\r\nX-Not-Date:",
+        1
+    );
+    let bob_msg = bob.recv_msg(&sent_msg).await;
+    assert_eq!(alice_msg.get_text(), bob_msg.get_text());
+
+    // Timestamp that the sender has put into the message
+    // should always be displayed as is on the receiver.
+    assert_eq!(alice_msg.get_timestamp(), bob_msg.get_timestamp());
+    Ok(())
+}