fix: base64-encode webxdc updates

Webxdc update messages may contain
long lines that get hard-wrapped
and may corrupt JSON if the message
is not encrypted.

base64-encode the update part
to avoid hard wrapping.

This is not necessary for encrypted
messages, but does not introduce
size overhead as OpenPGP messages
are compressed.

python/tests/test_1_online.py

@@ -324,6 +324,27 @@ def test_webxdc_message(acfactory, data, lp):
     assert len(list(ac2.direct_imap.conn.fetch(AND(seen=True)))) == 1
 
 
+def test_webxdc_huge_update(acfactory, data, lp):
+    ac1, ac2 = acfactory.get_online_accounts(2)
+    chat = ac1.create_chat(ac2)
+
+    msg1 = Message.new_empty(ac1, "webxdc")
+    msg1.set_text("message1")
+    msg1.set_file(data.get_path("webxdc/minimal.xdc"))
+    msg1 = chat.send_msg(msg1)
+    assert msg1.is_webxdc()
+    assert msg1.filename
+
+    msg2 = ac2._evtracker.wait_next_incoming_message()
+    assert msg2.is_webxdc()
+
+    payload = "A" * 1000
+    assert msg1.send_status_update({"payload": payload}, "some test data")
+    ac2._evtracker.get_matching("DC_EVENT_WEBXDC_STATUS_UPDATE")
+    update = msg2.get_status_updates()[0]
+    assert update["payload"] == payload
+
+
 def test_webxdc_download_on_demand(acfactory, data, lp):
     ac1, ac2 = acfactory.get_online_accounts(2)
     acfactory.introduce_each_other([ac1, ac2])

src/mimefactory.rs

@@ -1368,7 +1368,7 @@ impl<'a> MimeFactory<'a> {
 ///
 /// This line length limit is an
 /// [RFC5322 requirement](https://tools.ietf.org/html/rfc5322#section-2.1.1).
-fn wrapped_base64_encode(buf: &[u8]) -> String {
+pub(crate) fn wrapped_base64_encode(buf: &[u8]) -> String {
     let base64 = base64::engine::general_purpose::STANDARD.encode(buf);
     let mut chars = base64.chars();
     std::iter::repeat_with(|| chars.by_ref().take(78).collect::<String>())

src/webxdc.rs

@@ -18,6 +18,7 @@ use crate::contact::ContactId;
 use crate::context::Context;
 use crate::download::DownloadState;
 use crate::message::{Message, MessageState, MsgId, Viewtype};
+use crate::mimefactory::wrapped_base64_encode;
 use crate::mimeparser::SystemMessage;
 use crate::param::Param;
 use crate::param::Params;
@@ -535,13 +536,16 @@ impl Context {
     }
 
     pub(crate) fn build_status_update_part(&self, json: &str) -> PartBuilder {
+        let encoded_body = wrapped_base64_encode(json.as_bytes());
+
         PartBuilder::new()
             .content_type(&"application/json".parse::<mime::Mime>().unwrap())
             .header((
                 "Content-Disposition",
                 "attachment; filename=\"status-update.json\"",
             ))
-            .body(json)
+            .header(("Content-Transfer-Encoding", "base64"))
+            .body(encoded_body)
     }
 
     /// Receives status updates from receive_imf to the database
@@ -1785,7 +1789,6 @@ mod tests {
         assert_eq!(bob_instance.get_filename(), Some("minimal.xdc".to_string()));
         assert!(sent1.payload().contains("Content-Type: application/json"));
         assert!(sent1.payload().contains("status-update.json"));
-        assert!(sent1.payload().contains(r#""payload":{"foo":"bar"}"#));
         assert_eq!(
             bob.get_webxdc_status_updates(bob_instance.id, StatusUpdateSerial(0))
                 .await?,