Merge pull request #70999 from liggitt/oversized-spdystream-frames

Ensure oversized data frames are not written to spdystreams

Kubernetes-commit: 774f1628843f298c61bed9ea58818c9cceb6d8e7

tools/remotecommand/reader.go

@@ -0,0 +1,41 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package remotecommand
+
+import (
+	"io"
+)
+
+// readerWrapper delegates to an io.Reader so that only the io.Reader interface is implemented,
+// to keep io.Copy from doing things we don't want when copying from the reader to the data stream.
+//
+// If the Stdin io.Reader provided to remotecommand implements a WriteTo function (like bytes.Buffer does[1]),
+// io.Copy calls that method[2] to attempt to write the entire buffer to the stream in one call.
+// That results in an oversized call to spdystream.Stream#Write [3],
+// which results in a single oversized data frame[4] that is too large.
+//
+// [1] https://golang.org/pkg/bytes/#Buffer.WriteTo
+// [2] https://golang.org/pkg/io/#Copy
+// [3] https://github.com/kubernetes/kubernetes/blob/90295640ef87db9daa0144c5617afe889e7992b2/vendor/github.com/docker/spdystream/stream.go#L66-L73
+// [4] https://github.com/kubernetes/kubernetes/blob/90295640ef87db9daa0144c5617afe889e7992b2/vendor/github.com/docker/spdystream/spdy/write.go#L302-L304
+type readerWrapper struct {
+	reader io.Reader
+}
+
+func (r readerWrapper) Read(p []byte) (int, error) {
+	return r.reader.Read(p)
+}

tools/remotecommand/v1.go

@@ -127,7 +127,7 @@ func (p *streamProtocolV1) stream(conn streamCreator) error {
 		// because stdin is not closed until the process exits. If we try to call
 		// stdin.Close(), it returns no error but doesn't unblock the copy. It will
 		// exit when the process exits, instead.
-		go cp(v1.StreamTypeStdin, p.remoteStdin, p.Stdin)
+		go cp(v1.StreamTypeStdin, p.remoteStdin, readerWrapper{p.Stdin})
 	}
 
 	waitCount := 0

tools/remotecommand/v2.go

@@ -101,7 +101,7 @@ func (p *streamProtocolV2) copyStdin() {
 			// the executed command will remain running.
 			defer once.Do(func() { p.remoteStdin.Close() })
 
-			if _, err := io.Copy(p.remoteStdin, p.Stdin); err != nil {
+			if _, err := io.Copy(p.remoteStdin, readerWrapper{p.Stdin}); err != nil {
 				runtime.HandleError(err)
 			}
 		}()