fix: Ignore hidden headers in IMF section

Hidden headers are nonstandard, so they aren't DKIM-signed by e.g. OpenDKIM if they appear in IMF
section.

src/mimeparser.rs

@@ -253,6 +253,7 @@ impl MimeMessage {
             &mut chat_disposition_notification_to,
             &mail.headers,
         );
+        headers.retain(|k, _| !is_hidden(k));
 
         // Parse hidden headers.
         let mimetype = mail.ctype.mimetype.parse::<Mime>()?;
@@ -289,12 +290,7 @@ impl MimeMessage {
                     let key = field.get_key().to_lowercase();
 
                     // For now only avatar headers can be hidden.
-                    if !headers.contains_key(&key)
-                        && (key == "chat-user-avatar"
-                            || key == "chat-group-avatar"
-                            || key == "chat-delete"
-                            || key == "chat-edit")
-                    {
+                    if !headers.contains_key(&key) && is_hidden(&key) {
                         headers.insert(key.to_string(), field.get_value());
                     }
                 }
@@ -1987,6 +1983,14 @@ fn is_known(key: &str) -> bool {
     )
 }
 
+/// Returns if the header is hidden and must be ignored in the IMF section.
+fn is_hidden(key: &str) -> bool {
+    matches!(
+        key,
+        "chat-user-avatar" | "chat-group-avatar" | "chat-delete" | "chat-edit"
+    )
+}
+
 /// Parsed MIME part.
 #[derive(Debug, Default, Clone)]
 pub struct Part {

src/mimeparser/mimeparser_tests.rs

@@ -1,11 +1,12 @@
 use mailparse::ParsedMail;
+use std::mem;
 
 use super::*;
 use crate::{
     chat,
     chatlist::Chatlist,
     constants::{Blocked, DC_DESIRED_TEXT_LEN, DC_ELLIPSIS},
-    message::{MessageState, MessengerMessage},
+    message::{self, MessageState, MessengerMessage},
     receive_imf::receive_imf,
     test_utils::{TestContext, TestContextManager},
     tools::time,
@@ -1903,3 +1904,44 @@ This is the epilogue.  It is also to be ignored.";
         "This is explicitly typed plain US-ASCII text.\r\nIt DOES end with a linebreak.\r\n"
     );
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_chat_delete_imf_header() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+    let alice_chat = alice.create_chat(bob).await;
+
+    // Alice sends a message, then sends an invalid deletion request.
+    let sent1 = alice.send_text(alice_chat.id, "wtf").await;
+    let alice_msg = sent1.load_from_db().await;
+    assert_eq!(alice_chat.id.get_msg_cnt(alice).await?, 1);
+
+    message::delete_msgs_ex(alice, &[alice_msg.id], true).await?;
+    let mut sent2 = alice.pop_sent_msg().await;
+    let mut s0 = String::new();
+    let mut s1 = String::new();
+    for l in sent2.payload.lines() {
+        if l.starts_with("Chat-Delete:") {
+            s1 += l;
+            s1 += "\n";
+            continue;
+        }
+        s0 += l;
+        s0 += "\n";
+        if l.starts_with("Message-ID:") && s1.is_empty() {
+            s1 = mem::take(&mut s0);
+        }
+    }
+    sent2.payload = s1 + &s0;
+
+    // Bob receives both messages, the deletion request with "Chat-Delete" in IMF headers is
+    // received as text message.
+    let bob_msg = bob.recv_msg(&sent1).await;
+    assert_eq!(bob_msg.text, "wtf");
+    assert_eq!(bob_msg.chat_id.get_msg_cnt(bob).await?, 1);
+    bob.recv_msg_opt(&sent2).await;
+    assert_eq!(bob_msg.chat_id.get_msg_cnt(bob).await?, 2);
+
+    Ok(())
+}

test-data/message/mail_with_user_and_group_avatars.eml

@@ -1,7 +1,5 @@
 Chat-Group-ID: WVnDtF5azch
 Chat-Group-Name: =?utf-8?q?testgr1?=
-Chat-Group-Avatar: group-image.png
-Chat-User-Avatar: avatar.png
 Subject: =?utf-8?q?Chat=3A_testgr1=3A_hi!_?=
 Date: Thu, 12 Dec 2019 17:24:03 +0000
 X-Mailer: Delta Chat Core 1.0.0-beta.15/CLI
@@ -14,6 +12,8 @@ Content-Type: multipart/mixed; boundary="LV8nfXkpyyn39fsVyoB1b29PKDMeb5"
 
 --LV8nfXkpyyn39fsVyoB1b29PKDMeb5
 Content-Type: text/plain; charset=utf-8
+Chat-Group-Avatar: group-image.png
+Chat-User-Avatar: avatar.png
 
 hi! 
 

test-data/message/mail_with_user_avatar.eml

@@ -1,4 +1,3 @@
-Chat-User-Avatar: avatar.png
 Subject: =?utf-8?q?Chat=3A_this_is_a_message_with_a_=2E=2E=2E?=
 Message-ID: [email protected]
 In-Reply-To: [email protected]
@@ -12,6 +11,7 @@ Content-Type: multipart/mixed; boundary="luTiGu6GBoVLCvTkzVtmZmwsmhkNMw"
 
 --luTiGu6GBoVLCvTkzVtmZmwsmhkNMw
 Content-Type: text/plain; charset=utf-8
+Chat-User-Avatar: avatar.png
 
 this is a message with a profile-image attached
 

test-data/message/mail_with_user_avatar_deleted.eml

@@ -1,14 +1,20 @@
-Content-Type: text/plain; charset=utf-8
-Chat-User-Avatar: 0
 Subject: =?utf-8?q?Chat=3A_profile_image_deleted?=
 Message-ID: [email protected]
 Date: Sun, 08 Dec 2019 23:28:30 +0000
 X-Mailer: Delta Chat Core 1.0.0-beta.12/CLI
 Chat-Version: 1.0
 To: <tunis3@example>
 From: "=?utf-8?q??=" <[email protected]>
+Content-Type: multipart/mixed; boundary="luTiGu6GBoVLCvTkzVtmZmwsmhkNMw"
+
+
+--luTiGu6GBoVLCvTkzVtmZmwsmhkNMw
+Content-Type: text/plain; charset=utf-8
+Chat-User-Avatar: 0
 
 profile image deleted
 
 -- 
 Sent with my Delta Chat Messenger: https://delta.chat
+
+--luTiGu6GBoVLCvTkzVtmZmwsmhkNMw--