encode: fix response corruption when handle_errors is used (#7235)

encode: fix response corruption when handle_errors is used (#7235) * encode: fix response corruption when handle_errors is used * Move disabled check before hdr assignment

Siomachkin committed Sep 2, 2025 at 23:34 UTC 5473eb95d8e94505b8c06955bd200f37179c54a2

1 file changed +19 -1

modules/caddyhttp/encode/encode.go

+19 -1

@@ -177,7 +177,17 @@ func (enc *Encode) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyh

177 break

178 }

179 }

180 - return next.ServeHTTP(w, r)

180 +

181 + err := next.ServeHTTP(w, r)

182 + // If there was an error, disable encoding completely

183 + // This prevents corruption when handle_errors processes the response

184 + if err != nil {

185 + if ew, ok := w.(*responseWriter); ok {

186 + ew.disabled = true

187 + }

188 + }

189 +

190 + return err

191 }

192

193 func (enc *Encode) addEncoding(e Encoding) error {

@@ -233,6 +243,7 @@ type responseWriter struct {

243 statusCode int

244 wroteHeader bool

245 isConnect bool

246 + disabled bool // disable encoding (for error responses)

247 }

248

249 // WriteHeader stores the status to write when the time comes

@@ -425,7 +436,14 @@ func (rw *responseWriter) Unwrap() http.ResponseWriter {

436

437 // init should be called before we write a response, if rw.buf has contents.

438 func (rw *responseWriter) init() {

439 + // Don't initialize encoder for error responses

440 + // This prevents response corruption when handle_errors is used

441 + if rw.disabled {

442 + return

443 + }

444 +

445 hdr := rw.Header()

446 +

447 if hdr.Get("Content-Encoding") == "" && isEncodeAllowed(hdr) &&

448 rw.config.Match(rw) {

449 rw.w = rw.config.writerPools[rw.encodingName].Get().(Encoder)