limit webxdc-sizes for a better ux (#2971)

* limit webxdc-sizes for a better ux

* Update src/webxdc.rs

Co-authored-by: Asiel Díaz Benítez <adbenitez@nauta.cu>

* Update src/webxdc.rs

Co-authored-by: Asiel Díaz Benítez <adbenitez@nauta.cu>

Co-authored-by: Asiel Díaz Benítez <adbenitez@nauta.cu>

src/chat.rs

@@ -25,8 +25,8 @@ use crate::context::Context;
 use crate::dc_receive_imf::ReceivedMsg;
 use crate::dc_tools::{
     dc_create_id, dc_create_outgoing_rfc724_mid, dc_create_smeared_timestamp,
-    dc_create_smeared_timestamps, dc_get_abs_path, dc_gm2local_offset, improve_single_line_input,
-    time, IsNoneOrEmpty,
+    dc_create_smeared_timestamps, dc_get_abs_path, dc_get_filebytes, dc_gm2local_offset,
+    improve_single_line_input, time, IsNoneOrEmpty,
 };
 use crate::ephemeral::{delete_expired_messages, schedule_ephemeral_task, Timer as EphemeralTimer};
 use crate::events::EventType;
@@ -37,7 +37,7 @@ use crate::mimeparser::SystemMessage;
 use crate::param::{Param, Params};
 use crate::peerstate::{Peerstate, PeerstateVerifiedStatus};
 use crate::stock_str;
-use crate::webxdc::WEBXDC_SUFFIX;
+use crate::webxdc::{WEBXDC_SENDING_LIMIT, WEBXDC_SUFFIX};
 
 /// An chat item, such as a message or a marker.
 #[derive(Debug, Copy, Clone)]
@@ -1842,12 +1842,22 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
             }
         }
 
-        if msg.viewtype == Viewtype::Webxdc && blob.suffix() != Some(WEBXDC_SUFFIX) {
-            bail!(
-                "webxdc message {} does not have suffix {}",
-                blob,
-                WEBXDC_SUFFIX
-            );
+        if msg.viewtype == Viewtype::Webxdc {
+            if blob.suffix() != Some(WEBXDC_SUFFIX) {
+                bail!(
+                    "webxdc message {} does not have suffix {}",
+                    blob,
+                    WEBXDC_SUFFIX
+                );
+            } else if dc_get_filebytes(context, blob.to_abs_path()).await
+                > WEBXDC_SENDING_LIMIT as u64
+            {
+                bail!(
+                    "webxdc message {} exceeds acceptable size of {} bytes",
+                    blob.as_name(),
+                    WEBXDC_SENDING_LIMIT
+                );
+            }
         }
 
         info!(

src/webxdc.rs

@@ -20,6 +20,23 @@ use zip::ZipArchive;
 pub const WEBXDC_SUFFIX: &str = "xdc";
 const WEBXDC_DEFAULT_ICON: &str = "__webxdc__/default-icon.png";
 
+/// Defines the maximal size in bytes of an .xdc file that can be sent.
+///
+/// We introduce a limit to force developer to create small .xdc
+/// to save user's traffic and disk space for a better ux.
+///
+/// The 100K limit should also let .xdc pass worse-quality auto-download filters
+/// which are usually 160K incl. base64 overhead.
+///
+/// The limit is also an experiment to see how small we can go;
+/// it is planned to raise that limit as needed in subsequent versions.
+pub(crate) const WEBXDC_SENDING_LIMIT: usize = 102400;
+
+/// Be more tolerant for .xdc sizes on receiving -
+/// might be, the senders version uses already a larger limit
+/// and not showing the .xdc on some devices would be even worse ux.
+const WEBXDC_RECEIVING_LIMIT: usize = 1048576;
+
 /// Raw information read from manifest.toml
 #[derive(Debug, Deserialize)]
 #[non_exhaustive]
@@ -79,7 +96,16 @@ impl Context {
             let reader = std::io::Cursor::new(buf);
             if let Ok(mut archive) = zip::ZipArchive::new(reader) {
                 if let Ok(_index_html) = archive.by_name("index.html") {
-                    return Ok(true);
+                    if buf.len() <= WEBXDC_RECEIVING_LIMIT {
+                        return Ok(true);
+                    } else {
+                        error!(
+                            self,
+                            "{} exceeds acceptable size of {} bytes.",
+                            &filename,
+                            WEBXDC_SENDING_LIMIT
+                        );
+                    }
                 }
             }
         }
@@ -369,6 +395,16 @@ mod tests {
     use async_std::fs::File;
     use async_std::io::WriteExt;
 
+    #[allow(clippy::assertions_on_constants)]
+    #[async_std::test]
+    async fn test_webxdc_file_limits() -> Result<()> {
+        assert!(WEBXDC_SENDING_LIMIT >= 32768);
+        assert!(WEBXDC_SENDING_LIMIT < 16777216);
+        assert!(WEBXDC_RECEIVING_LIMIT >= WEBXDC_SENDING_LIMIT * 2);
+        assert!(WEBXDC_RECEIVING_LIMIT < 16777216);
+        Ok(())
+    }
+
     #[async_std::test]
     async fn test_is_webxdc_file() -> Result<()> {
         let t = TestContext::new().await;