Add proxy support for client socket connections

Related issue: netty#1133

Motivation:

There is no support for client socket connections via a proxy server in
Netty.

Modifications:

- Add a new module 'handler-proxy'
- Add ProxyHandler and its subclasses to support SOCKS 4a/5 and HTTP(S)
  proxy connections
- Add a full parameterized test for most scenarios
- Clean up pom.xml

Result:

A user can make an outgoing connection via proxy servers with only
trivial effort.

all/pom.xml

@@ -189,6 +189,13 @@
       <scope>compile</scope>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-handler-proxy</artifactId>
+      <version>${project.version}</version>
+      <scope>compile</scope>
+      <optional>true</optional>
+    </dependency>
     <dependency>
       <groupId>${project.groupId}</groupId>
       <artifactId>netty-transport</artifactId>

codec-dns/pom.xml

@@ -34,11 +34,6 @@
       <artifactId>netty-codec</artifactId>
       <version>${project.version}</version>
     </dependency>
-    <dependency>
-      <groupId>${project.groupId}</groupId>
-      <artifactId>netty-handler</artifactId>
-      <version>${project.version}</version>
-    </dependency>
 
     <dependency>
       <groupId>org.apache.directory.server</groupId>

codec-http/pom.xml

@@ -38,6 +38,7 @@
       <groupId>${project.groupId}</groupId>
       <artifactId>netty-handler</artifactId>
       <version>${project.version}</version>
+      <optional>true</optional>
     </dependency>
     <dependency>
       <groupId>com.jcraft</groupId>

codec-memcache/pom.xml

@@ -34,11 +34,6 @@
       <artifactId>netty-codec</artifactId>
       <version>${project.version}</version>
     </dependency>
-    <dependency>
-      <groupId>${project.groupId}</groupId>
-      <artifactId>netty-handler</artifactId>
-      <version>${project.version}</version>
-    </dependency>
   </dependencies>
 </project>
 

codec-mqtt/pom.xml

@@ -34,11 +34,7 @@
       <artifactId>netty-codec</artifactId>
       <version>${project.version}</version>
     </dependency>
-    <dependency>
-      <groupId>${project.groupId}</groupId>
-      <artifactId>netty-handler</artifactId>
-      <version>${project.version}</version>
-    </dependency>
+
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-all</artifactId>

codec-socks/pom.xml

@@ -34,11 +34,6 @@
       <artifactId>netty-codec</artifactId>
       <version>${project.version}</version>
     </dependency>
-    <dependency>
-      <groupId>${project.groupId}</groupId>
-      <artifactId>netty-handler</artifactId>
-      <version>${project.version}</version>
-    </dependency>
   </dependencies>
 </project>
 

codec-socks/src/main/java/io/netty/handler/codec/socksx/v4/Socks4CmdResponseDecoder.java

@@ -57,7 +57,6 @@ protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuf, List<Object> o
                 msg = new Socks4CmdResponse(cmdStatus, host, port);
             }
         }
-        ctx.pipeline().remove(this);
         out.add(msg);
     }
 

codec-socks/src/main/java/io/netty/handler/codec/socksx/v5/Socks5CmdResponseDecoder.java

@@ -83,7 +83,6 @@ protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuf, List<Object> o
                 }
             }
         }
-        ctx.pipeline().remove(this);
         out.add(msg);
     }
 

codec-stomp/pom.xml

@@ -34,11 +34,6 @@
       <artifactId>netty-codec</artifactId>
       <version>${project.version}</version>
     </dependency>
-    <dependency>
-      <groupId>${project.groupId}</groupId>
-      <artifactId>netty-handler</artifactId>
-      <version>${project.version}</version>
-    </dependency>
   </dependencies>
 </project>
 

example/pom.xml

@@ -44,6 +44,11 @@
       <artifactId>netty-handler</artifactId>
       <version>${project.version}</version>
     </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-handler-proxy</artifactId>
+      <version>${project.version}</version>
+    </dependency>
     <dependency>
       <groupId>${project.groupId}</groupId>
       <artifactId>netty-codec-http</artifactId>

handler-proxy/pom.xml

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2014 The Netty Project
+  ~
+  ~ The Netty Project licenses this file to you 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.
+  -->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>io.netty</groupId>
+    <artifactId>netty-parent</artifactId>
+    <version>5.0.0.Alpha2-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>netty-handler-proxy</artifactId>
+  <packaging>jar</packaging>
+
+  <name>Netty/Handler/Proxy</name>
+
+  <dependencies>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-transport</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-codec-socks</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-codec-http</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-handler</artifactId>
+      <version>${project.version}</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>
+

handler-proxy/src/main/java/io/netty/handler/proxy/HttpProxyHandler.java

@@ -0,0 +1,161 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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 io.netty.handler.proxy;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPipeline;
+import io.netty.handler.codec.AsciiString;
+import io.netty.handler.codec.base64.Base64;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpClientCodec;
+import io.netty.handler.codec.http.HttpHeaders.Names;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.HttpResponse;
+import io.netty.handler.codec.http.HttpResponseStatus;
+import io.netty.handler.codec.http.HttpVersion;
+import io.netty.handler.codec.http.LastHttpContent;
+import io.netty.util.CharsetUtil;
+
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+
+public final class HttpProxyHandler extends ProxyHandler {
+
+    private static final String PROTOCOL = "http";
+    private static final String AUTH_BASIC = "basic";
+
+    private final HttpClientCodec codec = new HttpClientCodec();
+    private final String username;
+    private final String password;
+    private final CharSequence authorization;
+    private HttpResponseStatus status;
+
+    public HttpProxyHandler(SocketAddress proxyAddress) {
+        super(proxyAddress);
+        username = null;
+        password = null;
+        authorization = null;
+    }
+
+    public HttpProxyHandler(SocketAddress proxyAddress, String username, String password) {
+        super(proxyAddress);
+        if (username == null) {
+            throw new NullPointerException("username");
+        }
+        if (password == null) {
+            throw new NullPointerException("password");
+        }
+        this.username = username;
+        this.password = password;
+
+        ByteBuf authz = Unpooled.copiedBuffer(username + ':' + password, CharsetUtil.UTF_8);
+        ByteBuf authzBase64 = Base64.encode(authz, false);
+
+        authorization = new AsciiString(authzBase64.toString(CharsetUtil.US_ASCII));
+
+        authz.release();
+        authzBase64.release();
+    }
+
+    @Override
+    public String protocol() {
+        return PROTOCOL;
+    }
+
+    @Override
+    public String authScheme() {
+        return authorization != null? AUTH_BASIC : AUTH_NONE;
+    }
+
+    public String username() {
+        return username;
+    }
+
+    public String password() {
+        return password;
+    }
+
+    @Override
+    protected void addCodec(ChannelHandlerContext ctx) throws Exception {
+        ChannelPipeline p = ctx.pipeline();
+        String name = ctx.name();
+        p.addBefore(name, null, codec);
+    }
+
+    @Override
+    protected void removeEncoder(ChannelHandlerContext ctx) throws Exception {
+        ctx.pipeline().remove(codec.encoder());
+    }
+
+    @Override
+    protected void removeDecoder(ChannelHandlerContext ctx) throws Exception {
+        ctx.pipeline().remove(codec.decoder());
+    }
+
+    @Override
+    protected Object newInitialMessage(ChannelHandlerContext ctx) throws Exception {
+        InetSocketAddress raddr = destinationAddress();
+        String rhost;
+        if (raddr.isUnresolved()) {
+            rhost = raddr.getHostString();
+        } else {
+            rhost = raddr.getAddress().getHostAddress();
+        }
+
+        FullHttpRequest req = new DefaultFullHttpRequest(
+                HttpVersion.HTTP_1_0, HttpMethod.CONNECT,
+                rhost + ':' + raddr.getPort(),
+                Unpooled.EMPTY_BUFFER, false);
+
+        SocketAddress proxyAddress = proxyAddress();
+        if (proxyAddress instanceof InetSocketAddress) {
+            InetSocketAddress hostAddr = (InetSocketAddress) proxyAddress;
+            req.headers().set(Names.HOST, hostAddr.getHostString() + ':' + hostAddr.getPort());
+        }
+
+        if (authorization != null) {
+            req.headers().set(Names.AUTHORIZATION, authorization);
+        }
+
+        return req;
+    }
+
+    @Override
+    protected boolean handleResponse(ChannelHandlerContext ctx, Object response) throws Exception {
+        if (response instanceof HttpResponse) {
+            if (status != null) {
+                throw new ProxyConnectException(exceptionMessage("too many responses"));
+            }
+            status = ((HttpResponse) response).status();
+        }
+
+        boolean finished = response instanceof LastHttpContent;
+        if (finished) {
+            if (status == null) {
+                throw new ProxyConnectException(exceptionMessage("missing response"));
+            }
+            if (status.code() != 200) {
+                throw new ProxyConnectException(exceptionMessage("status: " + status));
+            }
+        }
+
+        return finished;
+    }
+}

handler-proxy/src/main/java/io/netty/handler/proxy/ProxyConnectException.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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 io.netty.handler.proxy;
+
+import java.net.ConnectException;
+
+public class ProxyConnectException extends ConnectException {
+    private static final long serialVersionUID = 5211364632246265538L;
+
+    public ProxyConnectException() { }
+
+    public ProxyConnectException(String msg) {
+        super(msg);
+    }
+
+    public ProxyConnectException(Throwable cause) {
+        initCause(cause);
+    }
+
+    public ProxyConnectException(String msg, Throwable cause) {
+        super(msg);
+        initCause(cause);
+    }
+}