forward html-messages properly (#2151)

* add failing tests for forwarding html-mails

* let MsgId.get_html() return an option

* write html-part to local database on forwarding

* add html-part to forwarded non-dc messages

* read HTML-parts from encrypted messages

* avoid clone()

* Received:-header is no longer needed since #2152

* Update src/html.rs

Co-authored-by: Floris Bruynooghe <flub@devork.be>

* Update src/html.rs

Co-authored-by: Floris Bruynooghe <flub@devork.be>

* Update src/mimeparser.rs

Co-authored-by: Floris Bruynooghe <flub@devork.be>

* prefer 'orig' over 'org' as abbreviation for 'original'

* improve comment on tests

* prefer 'try_into()' over 'as u32' to avoid panics on bad data

* simplify ffi

Co-authored-by: Floris Bruynooghe <flub@devork.be>

src/html.rs

@@ -18,6 +18,7 @@ use crate::headerdef::{HeaderDef, HeaderDefMap};
 use crate::message::{Message, MsgId};
 use crate::mimeparser::parse_message_id;
 use crate::plaintext::PlainText;
+use lettre_email::PartBuilder;
 use mailparse::ParsedContentType;
 
 impl Message {
@@ -221,7 +222,7 @@ impl MsgId {
     /// this is the case at least when `Message.has_html()` returns true
     /// (we do not save raw mime unconditionally in the database to save space).
     /// The corresponding ffi-function is `dc_get_msg_html()`.
-    pub async fn get_html(self, context: &Context) -> String {
+    pub async fn get_html(self, context: &Context) -> Option<String> {
         let rawmime: Option<String> = context
             .sql
             .query_get_value(
@@ -232,19 +233,52 @@ impl MsgId {
             .await;
 
         if let Some(rawmime) = rawmime {
-            match HtmlMsgParser::from_bytes(context, rawmime.as_bytes()).await {
-                Err(err) => format!("parser error: {}", err),
-                Ok(parser) => parser.html,
+            if !rawmime.is_empty() {
+                match HtmlMsgParser::from_bytes(context, rawmime.as_bytes()).await {
+                    Err(err) => {
+                        warn!(context, "get_html: parser error: {}", err);
+                        None
+                    }
+                    Ok(parser) => Some(parser.html),
+                }
+            } else {
+                warn!(context, "get_html: empty mime for {}", self);
+                None
             }
         } else {
-            format!("parser error: no mime for {}", self)
+            warn!(context, "get_html: no mime for {}", self);
+            None
         }
     }
+
+    /// Wraps HTML generated by [`MsgId::get_html`] into a text/html mimepart structure.
+    ///
+    /// Used on forwarding messages to avoid leaking the original mime structure
+    /// and also to avoid sending too much, maybe large data.
+    pub async fn get_html_as_mimepart(self, context: &Context) -> Option<PartBuilder> {
+        self.get_html(context).await.map(|s| {
+            PartBuilder::new()
+                .content_type(&"text/html; charset=utf-8".parse::<mime::Mime>().unwrap())
+                .body(s)
+        })
+    }
+
+    // As [`MsgId::get_html_as_mimepart`] but wraps [`MsgId::get_html`] into text/html mime raw string.
+    pub async fn get_html_as_rawmime(self, context: &Context) -> Option<String> {
+        self.get_html_as_mimepart(context)
+            .await
+            .map(|p| p.build().as_string())
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::chat::forward_msgs;
+    use crate::config::Config;
+    use crate::constants::DC_CONTACT_ID_SELF;
+    use crate::dc_receive_imf::dc_receive_imf;
+    use crate::message::MessengerMessage;
     use crate::test_utils::TestContext;
 
     #[async_std::test]
@@ -393,4 +427,96 @@ test some special html-characters as &lt; &gt; and &amp; but also &quot; and &#x
             .is_some());
         assert!(parser.html.find("cid:").is_none());
     }
+
+    #[async_std::test]
+    async fn test_get_html_empty() {
+        let t = TestContext::new().await;
+        let msg_id = MsgId::new_unset();
+        assert!(msg_id.get_html(&t).await.is_none())
+    }
+
+    #[async_std::test]
+    async fn test_html_forwarding() {
+        // alice receives a non-delta html-message
+        let alice = TestContext::new_alice().await;
+        alice.set_config(Config::ShowEmails, Some("2")).await.ok();
+        let chat = alice.chat_with_contact("", "sender@testrun.org").await;
+        let raw = include_bytes!("../test-data/message/text_alt_plain_html.eml");
+        dc_receive_imf(&alice, raw, "INBOX", 1, false)
+            .await
+            .unwrap();
+        let msg = alice.get_last_msg_in(chat.get_id()).await;
+        assert_ne!(msg.get_from_id(), DC_CONTACT_ID_SELF);
+        assert_eq!(msg.is_dc_message, MessengerMessage::No);
+        assert!(!msg.is_forwarded());
+        assert!(msg.get_text().unwrap().find("this is plain").is_some());
+        assert!(msg.has_html());
+        let html = msg.get_id().get_html(&alice).await.unwrap();
+        assert!(html.find("this is <b>html</b>").is_some());
+
+        // alice: create chat with bob and forward received html-message there
+        let chat = alice.chat_with_contact("", "bob@example.net").await;
+        forward_msgs(&alice, &[msg.get_id()], chat.get_id())
+            .await
+            .unwrap();
+        let msg = alice.get_last_msg_in(chat.get_id()).await;
+        assert_eq!(msg.get_from_id(), DC_CONTACT_ID_SELF);
+        assert_eq!(msg.is_dc_message, MessengerMessage::Yes);
+        assert!(msg.is_forwarded());
+        assert!(msg.get_text().unwrap().find("this is plain").is_some());
+        assert!(msg.has_html());
+        let html = msg.get_id().get_html(&alice).await.unwrap();
+        assert!(html.find("this is <b>html</b>").is_some());
+
+        // bob: check that bob also got the html-part of the forwarded message
+        let bob = TestContext::new_bob().await;
+        let chat = bob.chat_with_contact("", "alice@example.com").await;
+        bob.recv_msg(&alice.pop_sent_msg().await).await;
+        let msg = bob.get_last_msg_in(chat.get_id()).await;
+        assert_ne!(msg.get_from_id(), DC_CONTACT_ID_SELF);
+        assert_eq!(msg.is_dc_message, MessengerMessage::Yes);
+        assert!(msg.is_forwarded());
+        assert!(msg.get_text().unwrap().find("this is plain").is_some());
+        assert!(msg.has_html());
+        let html = msg.get_id().get_html(&bob).await.unwrap();
+        assert!(html.find("this is <b>html</b>").is_some());
+    }
+
+    #[async_std::test]
+    async fn test_html_forwarding_encrypted() {
+        // Alice receives a non-delta html-message
+        // (`ShowEmails=1` lets Alice actually receive non-delta messages for known contacts,
+        // the contact is marked as known by creating a chat using `chat_with_contact()`)
+        let alice = TestContext::new_alice().await;
+        alice.set_config(Config::ShowEmails, Some("1")).await.ok();
+        let chat = alice.chat_with_contact("", "sender@testrun.org").await;
+        let raw = include_bytes!("../test-data/message/text_alt_plain_html.eml");
+        dc_receive_imf(&alice, raw, "INBOX", 1, false)
+            .await
+            .unwrap();
+        let msg = alice.get_last_msg_in(chat.get_id()).await;
+
+        // forward the message to saved-messages,
+        // this will encrypt the message as new_alice() has set up keys
+        let chat = alice.get_self_chat().await;
+        forward_msgs(&alice, &[msg.get_id()], chat.get_id())
+            .await
+            .unwrap();
+        let msg = alice.pop_sent_msg().await;
+
+        // receive the message on another device
+        let alice = TestContext::new_alice().await;
+        assert_eq!(alice.get_config_int(Config::ShowEmails).await, 0); // set to "1" above, make sure it is another db
+        alice.recv_msg(&msg).await;
+        let chat = alice.get_self_chat().await;
+        let msg = alice.get_last_msg_in(chat.get_id()).await;
+        assert_eq!(msg.get_from_id(), DC_CONTACT_ID_SELF);
+        assert_eq!(msg.is_dc_message, MessengerMessage::Yes);
+        assert!(msg.get_showpadlock());
+        assert!(msg.is_forwarded());
+        assert!(msg.get_text().unwrap().find("this is plain").is_some());
+        assert!(msg.has_html());
+        let html = msg.get_id().get_html(&alice).await.unwrap();
+        assert!(html.find("this is <b>html</b>").is_some());
+    }
 }