message deletion request API (#6576)

this PR adds an API allowing users to delete their messages on other
member's devices

this PR is build on top of
https://github.com/deltachat/deltachat-core-rust/pull/6573 which should
be merged first

a test is missing, otherwise ready for review; it is working already in
https://github.com/deltachat/deltachat-ios/pull/2611

deltachat-ffi/deltachat.h

@@ -1056,6 +1056,21 @@ uint32_t        dc_send_text_msg             (dc_context_t* context, uint32_t ch
 void            dc_send_edit_request         (dc_context_t* context, uint32_t msg_id, const char* new_text);
 
 
+/**
+ * Send chat members a request to delete the given messages.
+ *
+ * Only outgoing messages can be deleted this way
+ * and all messages must be in the same chat.
+ * No tombstone or sth. like that is left.
+ *
+ * @memberof dc_context_t
+ * @param context The context object as returned from dc_context_new().
+ * @param msg_ids An array of uint32_t containing all message IDs to delete.
+ * @param msg_cnt The number of messages IDs in the msg_ids array.
+ */
+ void            dc_send_delete_request       (dc_context_t* context, const uint32_t* msg_ids, int msg_cnt);
+
+
 /**
  * Send invitation to a videochat.
  *

deltachat-ffi/src/lib.rs

@@ -1058,6 +1058,25 @@ pub unsafe extern "C" fn dc_send_edit_request(
         .unwrap_or_log_default(ctx, "Failed to send text edit")
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn dc_send_delete_request(
+    context: *mut dc_context_t,
+    msg_ids: *const u32,
+    msg_cnt: libc::c_int,
+) {
+    if context.is_null() || msg_ids.is_null() || msg_cnt <= 0 {
+        eprintln!("ignoring careless call to dc_send_delete_request()");
+        return;
+    }
+    let ctx = &*context;
+    let msg_ids = convert_and_prune_message_ids(msg_ids, msg_cnt);
+
+    block_on(message::delete_msgs_ex(ctx, &msg_ids, true))
+        .context("failed dc_send_delete_request() call")
+        .log_err(ctx)
+        .ok();
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn dc_send_videochat_invitation(
     context: *mut dc_context_t,

src/chat/chat_tests.rs

@@ -3802,3 +3802,44 @@ async fn test_cannot_send_edit_request() -> Result<()> {
 
     Ok(())
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_send_delete_request() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let alice = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+    let alice_chat = alice.create_chat(bob).await;
+    let bob_chat = bob.create_chat(alice).await;
+
+    // Bobs sends a message to Alice, so Alice learns Bob's key
+    let sent0 = bob.send_text(bob_chat.id, "¡ola!").await;
+    alice.recv_msg(&sent0).await;
+
+    // Alice sends a message, then sends a 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?, 2);
+
+    message::delete_msgs_ex(alice, &[alice_msg.id], true).await?;
+    let sent2 = alice.pop_sent_msg().await;
+    assert_eq!(alice_chat.id.get_msg_cnt(alice).await?, 1);
+
+    // Bob receives both messages and has nothing the end
+    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?, 2);
+
+    bob.recv_msg_opt(&sent2).await;
+    assert_eq!(bob_msg.chat_id.get_msg_cnt(bob).await?, 1);
+
+    // Alice has another device, and there is also nothing at the end
+    let alice2 = &tcm.alice().await;
+    alice2.recv_msg(&sent0).await;
+    let alice2_msg = alice2.recv_msg(&sent1).await;
+    assert_eq!(alice2_msg.chat_id.get_msg_cnt(alice2).await?, 2);
+
+    alice2.recv_msg_opt(&sent2).await;
+    assert_eq!(alice2_msg.chat_id.get_msg_cnt(alice2).await?, 1);
+
+    Ok(())
+}

src/headerdef.rs

@@ -80,6 +80,9 @@ pub enum HeaderDef {
     ChatDispositionNotificationTo,
     ChatWebrtcRoom,
 
+    /// This message deletes the messages listed in the value by rfc724_mid.
+    ChatDelete,
+
     /// This message obsoletes the text of the message defined here by rfc724_mid.
     ChatEdit,
 

src/message.rs

@@ -12,7 +12,7 @@ use serde::{Deserialize, Serialize};
 use tokio::{fs, io};
 
 use crate::blob::BlobObject;
-use crate::chat::{Chat, ChatId, ChatIdBlocked, ChatVisibility};
+use crate::chat::{send_msg, Chat, ChatId, ChatIdBlocked, ChatVisibility};
 use crate::chatlist_events;
 use crate::config::Config;
 use crate::constants::{
@@ -1711,20 +1711,31 @@ pub(crate) async fn delete_msgs_locally_done(
     Ok(())
 }
 
-/// Deletes requested messages
-/// by moving them to the trash chat
-/// and scheduling for deletion on IMAP.
+/// Delete messages on all devices and on IMAP.
 pub async fn delete_msgs(context: &Context, msg_ids: &[MsgId]) -> Result<()> {
+    delete_msgs_ex(context, msg_ids, false).await
+}
+
+/// Delete messages on all devices, on IMAP and optionally for all chat members.
+/// Deleted messages are moved to the trash chat and scheduling for deletion on IMAP.
+/// When deleting messages for others, all messages must be self-sent and in the same chat.
+pub async fn delete_msgs_ex(
+    context: &Context,
+    msg_ids: &[MsgId],
+    delete_for_all: bool,
+) -> Result<()> {
     let mut modified_chat_ids = HashSet::new();
     let mut deleted_rfc724_mid = Vec::new();
     let mut res = Ok(());
 
     for &msg_id in msg_ids {
         let msg = Message::load_from_db(context, msg_id).await?;
-        delete_msg_locally(context, &msg).await?;
+        ensure!(
+            !delete_for_all || msg.from_id == ContactId::SELF,
+            "Can delete only own messages for others"
+        );
 
         modified_chat_ids.insert(msg.chat_id);
-
         deleted_rfc724_mid.push(msg.rfc724_mid.clone());
 
         let target = context.get_delete_msgs_target().await?;
@@ -1744,13 +1755,32 @@ pub async fn delete_msgs(context: &Context, msg_ids: &[MsgId]) -> Result<()> {
     }
     res?;
 
-    delete_msgs_locally_done(context, msg_ids, modified_chat_ids).await?;
+    if delete_for_all {
+        ensure!(
+            modified_chat_ids.len() == 1,
+            "Can delete only from same chat."
+        );
+        if let Some(chat_id) = modified_chat_ids.iter().next() {
+            let mut msg = Message::new_text("🚮".to_owned());
+            msg.param.set_int(Param::GuaranteeE2ee, 1);
+            msg.param
+                .set(Param::DeleteRequestFor, deleted_rfc724_mid.join(" "));
+            msg.hidden = true;
+            send_msg(context, *chat_id, &mut msg).await?;
+        }
+    } else {
+        context
+            .add_sync_item(SyncData::DeleteMessages {
+                msgs: deleted_rfc724_mid,
+            })
+            .await?;
+    }
 
-    context
-        .add_sync_item(SyncData::DeleteMessages {
-            msgs: deleted_rfc724_mid,
-        })
-        .await?;
+    for &msg_id in msg_ids {
+        let msg = Message::load_from_db(context, msg_id).await?;
+        delete_msg_locally(context, &msg).await?;
+    }
+    delete_msgs_locally_done(context, msg_ids, modified_chat_ids).await?;
 
     // Interrupt Inbox loop to start message deletion, run housekeeping and call send_sync_msg().
     context.scheduler.interrupt_inbox().await;

src/mimefactory.rs

@@ -734,6 +734,12 @@ impl MimeFactory {
                     )
                     .into(),
                 ));
+            } else if let Some(rfc724_mid_list) = msg.param.get(Param::DeleteRequestFor) {
+                headers.push((
+                    "Chat-Delete",
+                    mail_builder::headers::message_id::MessageId::new(rfc724_mid_list.to_string())
+                        .into(),
+                ));
             }
         }
 
@@ -861,7 +867,10 @@ impl MimeFactory {
             if header_name == "message-id" {
                 unprotected_headers.push(header.clone());
                 hidden_headers.push(header.clone());
-            } else if header_name == "chat-user-avatar" || header_name == "chat-edit" {
+            } else if header_name == "chat-user-avatar"
+                || header_name == "chat-delete"
+                || header_name == "chat-edit"
+            {
                 hidden_headers.push(header.clone());
             } else if header_name == "autocrypt"
                 && !context.get_config_bool(Config::ProtectAutocrypt).await?

src/mimeparser.rs

@@ -292,6 +292,7 @@ impl MimeMessage {
                     if !headers.contains_key(&key)
                         && (key == "chat-user-avatar"
                             || key == "chat-group-avatar"
+                            || key == "chat-delete"
                             || key == "chat-edit")
                     {
                         headers.insert(key.to_string(), field.get_value());
@@ -450,6 +451,7 @@ impl MimeMessage {
                     HeaderDef::ChatGroupMemberAdded,
                     HeaderDef::ChatGroupMemberTimestamps,
                     HeaderDef::ChatGroupPastMembers,
+                    HeaderDef::ChatDelete,
                     HeaderDef::ChatEdit,
                 ] {
                     headers.remove(h.get_headername());

src/param.rs

@@ -207,6 +207,9 @@ pub enum Param {
     /// For messages: Whether [crate::message::Viewtype::Sticker] should be forced.
     ForceSticker = b'X',
 
+    /// For messages: Message is a deletion request. The value is a list of rfc724_mid of the messages to delete.
+    DeleteRequestFor = b'M',
+
     /// For messages: Message is a text edit message. the value of this parameter is the rfc724_mid of the original message.
     TextEditFor = b'I',
 

src/receive_imf.rs

@@ -1532,6 +1532,38 @@ async fn add_parts(
                 "Edit message: rfc724_mid {rfc724_mid:?} not found."
             );
         }
+    } else if let Some(rfc724_mid_list) = mime_parser.get_header(HeaderDef::ChatDelete) {
+        chat_id = DC_CHAT_ID_TRASH;
+        if let Some(part) = mime_parser.parts.first() {
+            if part.param.get_bool(Param::GuaranteeE2ee).unwrap_or(false) {
+                let mut modified_chat_ids = HashSet::new();
+                let mut msg_ids = Vec::new();
+
+                let rfc724_mid_vec: Vec<&str> = rfc724_mid_list.split_whitespace().collect();
+                for rfc724_mid in rfc724_mid_vec {
+                    if let Some((msg_id, _)) =
+                        message::rfc724_mid_exists(context, rfc724_mid).await?
+                    {
+                        if let Some(msg) = Message::load_from_db_optional(context, msg_id).await? {
+                            if msg.from_id == from_id {
+                                message::delete_msg_locally(context, &msg).await?;
+                                msg_ids.push(msg.id);
+                                modified_chat_ids.insert(msg.chat_id);
+                            } else {
+                                warn!(context, "Delete message: Bad sender.");
+                            }
+                        } else {
+                            warn!(context, "Delete message: Database entry does not exist.");
+                        }
+                    } else {
+                        warn!(context, "Delete message: {rfc724_mid:?} not found.");
+                    }
+                }
+                message::delete_msgs_locally_done(context, &msg_ids, modified_chat_ids).await?;
+            } else {
+                warn!(context, "Delete message: Not encrypted.");
+            }
+        }
     }
 
     let mut parts = mime_parser.parts.iter().peekable();