Clear service decoders on oversized frames

src/exec_service.rs

@@ -32,6 +32,7 @@ impl FrameDecoder {
             }
             let len = u32::from_be_bytes(self.buf[..4].try_into().unwrap()) as usize;
             if len > FRAME_MAX_LEN {
+                self.buf.clear();
                 bail!("exec protocol frame too large: {len} bytes");
             }
             if self.buf.len() < 4 + len {
@@ -69,3 +70,23 @@ fn encode_frame(payload: &[u8]) -> Result<Vec<u8>> {
     out.extend_from_slice(payload);
     Ok(out)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn oversized_frame_clears_decoder_state() {
+        let mut decoder = FrameDecoder::default();
+        let too_large = ((FRAME_MAX_LEN + 1) as u32).to_be_bytes();
+        assert!(decoder.push(&too_large).is_err());
+
+        let valid = encode_response(&ExecResponse::Exit { code: Some(0) }).unwrap();
+        let frames = decoder.push(&valid).unwrap();
+        assert_eq!(frames.len(), 1);
+        assert_eq!(
+            decode_response(&frames[0]).unwrap(),
+            ExecResponse::Exit { code: Some(0) }
+        );
+    }
+}

src/file_transfer.rs

@@ -123,6 +123,7 @@ impl FrameDecoder {
             }
             let len = u32::from_be_bytes(self.buf[..4].try_into().unwrap()) as usize;
             if len > FRAME_MAX_LEN {
+                self.buf.clear();
                 bail!("file protocol frame too large: {len} bytes");
             }
             if self.buf.len() < 4 + len {
@@ -288,6 +289,18 @@ mod tests {
         assert_eq!(frames.len(), 1);
     }
 
+    #[test]
+    fn oversized_frame_clears_decoder_state() {
+        let mut decoder = FrameDecoder::default();
+        let too_large = ((FRAME_MAX_LEN + 1) as u32).to_be_bytes();
+        assert!(decoder.push(&too_large).is_err());
+
+        let valid = encode_response(&FileResponse::Ok).unwrap();
+        let frames = decoder.push(&valid).unwrap();
+        assert_eq!(frames.len(), 1);
+        assert_eq!(decode_response(&frames[0]).unwrap(), FileResponse::Ok);
+    }
+
     #[test]
     fn copy_endpoint_parses_scp_style_but_not_windows_drive() {
         assert_eq!(