add StringWriter interface to ResponseWriter

http/interceptor.go

@@ -104,11 +104,25 @@ func (i *rwInterceptor) Write(b []byte) (int, error) {
 	return i.w.Write(b)
 }
 
+// WriteString buffers the response body until the request body limit is reach or an
+// interruption is triggered, this buffer is later used to analyse the body in
+// the response processor.
+// If the body isn't accessible or the mime type isn't processable, the response
+// body is being written to the delegate response writer directly.
+func (i *rwInterceptor) WriteString(s string) (n int, err error) {
+	return i.Write([]byte(s))
+}
+
 func (i *rwInterceptor) Header() http.Header {
 	return i.w.Header()
 }
 
-var _ http.ResponseWriter = (*rwInterceptor)(nil)
+type responseWriter interface {
+	http.ResponseWriter
+	io.StringWriter
+}
+
+var _ responseWriter = (*rwInterceptor)(nil)
 
 // wrap wraps the interceptor into a response writer that also preserves
 // the http interfaces implemented by the original response writer to avoid
@@ -175,103 +189,103 @@ func wrap(w http.ResponseWriter, r *http.Request, tx types.Transaction) (
 	switch {
 	case !isHijacker && !isPusher && !isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 		}{i}, responseProcessor
 	case !isHijacker && !isPusher && !isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			io.ReaderFrom
 		}{i, reader}, responseProcessor
 	case !isHijacker && !isPusher && isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Flusher
 		}{i, flusher}, responseProcessor
 	case !isHijacker && !isPusher && isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Flusher
 			io.ReaderFrom
 		}{i, flusher, reader}, responseProcessor
 	case !isHijacker && isPusher && !isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Pusher
 		}{i, pusher}, responseProcessor
 	case !isHijacker && isPusher && !isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Pusher
 			io.ReaderFrom
 		}{i, pusher, reader}, responseProcessor
 	case !isHijacker && isPusher && isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Pusher
 			http.Flusher
 		}{i, pusher, flusher}, responseProcessor
 	case !isHijacker && isPusher && isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Pusher
 			http.Flusher
 			io.ReaderFrom
 		}{i, pusher, flusher, reader}, responseProcessor
 	case isHijacker && !isPusher && !isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 		}{i, hijacker}, responseProcessor
 	case isHijacker && !isPusher && !isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			io.ReaderFrom
 		}{i, hijacker, reader}, responseProcessor
 	case isHijacker && !isPusher && isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			http.Flusher
 		}{i, hijacker, flusher}, responseProcessor
 	case isHijacker && !isPusher && isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			http.Flusher
 			io.ReaderFrom
 		}{i, hijacker, flusher, reader}, responseProcessor
 	case isHijacker && isPusher && !isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			http.Pusher
 		}{i, hijacker, pusher}, responseProcessor
 	case isHijacker && isPusher && !isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			http.Pusher
 			io.ReaderFrom
 		}{i, hijacker, pusher, reader}, responseProcessor
 	case isHijacker && isPusher && isFlusher && !isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			http.Pusher
 			http.Flusher
 		}{i, hijacker, pusher, flusher}, responseProcessor
 	case isHijacker && isPusher && isFlusher && isReader:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 			http.Hijacker
 			http.Pusher
 			http.Flusher
 			io.ReaderFrom
 		}{i, hijacker, pusher, flusher, reader}, responseProcessor
 	default:
 		return struct {
-			http.ResponseWriter
+			responseWriter
 		}{i}, responseProcessor
 	}
 }

http/interceptor_test.go

@@ -8,6 +8,7 @@
 package http
 
 import (
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -44,3 +45,32 @@ func TestWriteHeader(t *testing.T) {
 		t.Errorf("unexpected status code, want %d, have %d", want, have)
 	}
 }
+
+func TestWriteString(t *testing.T) {
+	waf, err := coraza.NewWAF(coraza.NewWAFConfig())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tx := waf.NewTransaction()
+	req, _ := http.NewRequest("GET", "", nil)
+	res := httptest.NewRecorder()
+	rw, responseProcessor := wrap(res, req, tx)
+	n, err := rw.(io.StringWriter).WriteString("hello")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if n != 5 {
+		t.Errorf("unexpected number of bytes written, want 5, have %d", n)
+	}
+
+	err = responseProcessor(tx, req)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+
+	if want, have := "hello", res.Body.String(); want != have {
+		t.Errorf("unexpected response body, want %s, have %s", want, have)
+	}
+}