From a4146b706c0a0577f9ce65d711ad64a6847e3e24 Mon Sep 17 00:00:00 2001
From: JLofgren <john.lofgren@gmail.com>
Date: Mon, 16 Apr 2018 16:27:36 -0500
Subject: [PATCH] Do not enforce arbitrary max header list size in HpackEncoder
 (#7853)

Motivation:

When connecting to an HTTP/2 server that did not set any value for the
SETTINGS_MAX_HEADER_LIST_SIZE in the settings frame, the netty client was
imposing an arbitrary maximum header list size of 8kB. There should be no need
for the client to enforce such a limit if the server has not specified any
limit. This caused an issue for a grpc-java client that needed to send a large
header to a server via an Envoy proxy server. The error condition is
demonstrated here: https://github.com/JLofgren/demo-grpc-java-bug-4284

Fixes grpc-java issue #4284 - https://github.com/grpc/grpc-java/issues/4284
and netty issue #7825 - https://github.com/netty/netty/issues/7825

Modifications:

In HpackEncoder use MAX_HEADER_LIST_SIZE as default maxHeader list size.

Result:

HpackEncoder will only enforce a max header list size if the server has
specified a limit in its settings frame.
---
 .../handler/codec/http2/HpackEncoder.java     |  3 +-
 .../handler/codec/http2/HpackEncoderTest.java | 42 +++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/codec-http2/src/main/java/io/netty/handler/codec/http2/HpackEncoder.java b/codec-http2/src/main/java/io/netty/handler/codec/http2/HpackEncoder.java
index b9a7703042..7719072a49 100644
--- a/codec-http2/src/main/java/io/netty/handler/codec/http2/HpackEncoder.java
+++ b/codec-http2/src/main/java/io/netty/handler/codec/http2/HpackEncoder.java
@@ -41,7 +41,6 @@ import java.util.Arrays;
 import java.util.Map;
 
 import static io.netty.handler.codec.http2.HpackUtil.equalsConstantTime;
-import static io.netty.handler.codec.http2.Http2CodecUtil.DEFAULT_HEADER_LIST_SIZE;
 import static io.netty.handler.codec.http2.Http2CodecUtil.DEFAULT_HEADER_TABLE_SIZE;
 import static io.netty.handler.codec.http2.Http2CodecUtil.MAX_HEADER_LIST_SIZE;
 import static io.netty.handler.codec.http2.Http2CodecUtil.MAX_HEADER_TABLE_SIZE;
@@ -86,7 +85,7 @@ final class HpackEncoder {
     public HpackEncoder(boolean ignoreMaxHeaderListSize, int arraySizeHint) {
         this.ignoreMaxHeaderListSize = ignoreMaxHeaderListSize;
         maxHeaderTableSize = DEFAULT_HEADER_TABLE_SIZE;
-        maxHeaderListSize = DEFAULT_HEADER_LIST_SIZE;
+        maxHeaderListSize = MAX_HEADER_LIST_SIZE;
         // Enforce a bound of [2, 128] because hashMask is a byte. The max possible value of hashMask is one less
         // than the length of this array, and we want the mask to be > 0.
         headerFields = new HeaderEntry[findNextPositivePowerOfTwo(max(2, min(arraySizeHint, 128)))];
diff --git a/codec-http2/src/test/java/io/netty/handler/codec/http2/HpackEncoderTest.java b/codec-http2/src/test/java/io/netty/handler/codec/http2/HpackEncoderTest.java
index 2996b5db6b..b1dce05c38 100644
--- a/codec-http2/src/test/java/io/netty/handler/codec/http2/HpackEncoderTest.java
+++ b/codec-http2/src/test/java/io/netty/handler/codec/http2/HpackEncoderTest.java
@@ -56,4 +56,46 @@ public class HpackEncoderTest {
             buf.release();
         }
     }
+
+    /**
+     * The encoder should not impose an arbitrary limit on the header size if
+     * the server has not specified any limit.
+     * @throws Http2Exception
+     */
+    @Test
+    public void testWillEncode16MBHeaderByDefault() throws Http2Exception {
+        ByteBuf buf = Unpooled.buffer();
+        String bigHeaderName = "x-big-header";
+        int bigHeaderSize = 1024 * 1024 * 16;
+        String bigHeaderVal = new String(new char[bigHeaderSize]).replace('\0', 'X');
+        Http2Headers headersIn = new DefaultHttp2Headers().add(
+                "x-big-header", bigHeaderVal);
+        Http2Headers headersOut = new DefaultHttp2Headers();
+
+        try {
+            hpackEncoder.encodeHeaders(0, buf, headersIn, Http2HeadersEncoder.NEVER_SENSITIVE);
+            hpackDecoder.setMaxHeaderListSize(bigHeaderSize + 1024, bigHeaderSize + 1024);
+            hpackDecoder.decode(0, buf, headersOut, false);
+        } finally {
+            buf.release();
+        }
+        assertEquals(headersOut.get(bigHeaderName).toString(), bigHeaderVal);
+    }
+
+    @Test(expected = Http2Exception.class)
+    public void testSetMaxHeaderListSizeEnforcedAfterSet() throws Http2Exception {
+        ByteBuf buf = Unpooled.buffer();
+        Http2Headers headers = new DefaultHttp2Headers().add(
+                "x-big-header",
+                new String(new char[1024 * 16]).replace('\0', 'X')
+        );
+
+        hpackEncoder.setMaxHeaderListSize(1000);
+
+        try {
+            hpackEncoder.encodeHeaders(0, buf, headers, Http2HeadersEncoder.NEVER_SENSITIVE);
+        } finally {
+            buf.release();
+        }
+    }
 }