http3: move length limiting logic to the body (#4439)

The length limit is a property of the (request and response) body. As
such, it's better implemented there than by wrapping the HTTP stream.

http3/http_stream.go

@@ -8,6 +8,7 @@ import (
 	"strconv"
 
 	"github.com/quic-go/quic-go"
+	"github.com/quic-go/quic-go/internal/protocol"
 
 	"github.com/quic-go/qpack"
 )
@@ -100,6 +101,10 @@ func (s *stream) Write(b []byte) (int, error) {
 	return s.Stream.Write(b)
 }
 
+func (s *stream) StreamID() protocol.StreamID {
+	return s.Stream.StreamID()
+}
+
 // The stream conforms to the quic.Stream interface, but instead of writing to and reading directly
 // from the QUIC stream, it writes to and reads from the HTTP stream.
 type requestStream struct {
@@ -197,13 +202,11 @@ func (s *requestStream) ReadResponse() (*http.Response, error) {
 
 	// Check that the server doesn't send more data in DATA frames than indicated by the Content-Length header (if set).
 	// See section 4.1.2 of RFC 9114.
-	var httpStr Stream
+	contentLength := int64(-1)
 	if _, ok := res.Header["Content-Length"]; ok && res.ContentLength >= 0 {
-		httpStr = newLengthLimitedStream(s.stream, res.ContentLength)
-	} else {
-		httpStr = s.stream
+		contentLength = res.ContentLength
 	}
-	respBody := newResponseBody(httpStr, s.reqDone)
+	respBody := newResponseBody(s.stream, contentLength, s.reqDone)
 
 	// Rules for when to set Content-Length are defined in https://tools.ietf.org/html/rfc7230#section-3.3.2.
 	_, hasTransferEncoding := res.Header["Transfer-Encoding"]
@@ -231,45 +234,3 @@ func (s *requestStream) ReadResponse() (*http.Response, error) {
 	res.Body = s.responseBody
 	return res, nil
 }
-
-var errTooMuchData = errors.New("peer sent too much data")
-
-type lengthLimitedStream struct {
-	*stream
-
-	remainingContentLength int64
-	resetStream            bool
-}
-
-var _ Stream = &lengthLimitedStream{}
-
-func newLengthLimitedStream(str *stream, contentLength int64) *lengthLimitedStream {
-	return &lengthLimitedStream{
-		stream:                 str,
-		remainingContentLength: contentLength,
-	}
-}
-
-func (s *lengthLimitedStream) checkContentLengthViolation() error {
-	if s.remainingContentLength < 0 || s.remainingContentLength == 0 && s.hasMoreData() {
-		if !s.resetStream {
-			s.CancelRead(quic.StreamErrorCode(ErrCodeMessageError))
-			s.CancelWrite(quic.StreamErrorCode(ErrCodeMessageError))
-			s.resetStream = true
-		}
-		return errTooMuchData
-	}
-	return nil
-}
-
-func (s *lengthLimitedStream) Read(b []byte) (int, error) {
-	if err := s.checkContentLengthViolation(); err != nil {
-		return 0, err
-	}
-	n, err := s.stream.Read(b[:min(int64(len(b)), s.remainingContentLength)])
-	s.remainingContentLength -= int64(n)
-	if err := s.checkContentLengthViolation(); err != nil {
-		return n, err
-	}
-	return n, err
-}