Android Java层Socket Hook点分析教学文档<\/h1>

前言<\/h2>
Socket作为网络通信的基础接口，在Android应用开发中广泛使用。通过分析Socket源码并寻找Hook点，可以定位通信过程中的关键加密API和潜在漏洞点，扩展攻击面。本文将从TCP和UDP两种协议出发，详细分析Java层的Socket Hook点。<\/p>

一、Socket基础实现<\/h2>

1.1 Socket基本实现过程<\/h3>
创建socket<\/li>
绑定地址和端口<\/li>
进行连接(TCP)或直接发送数据(UDP)<\/li>
数据传输<\/li>
关闭socket<\/li> <\/ol>
1.2 TCP与UDP区别<\/h3>
TCP：面向连接，可靠传输，有流量控制和拥塞控制<\/li>
UDP：无连接，不可靠传输，效率高<\/li> <\/ul>
二、TCP Socket Hook点分析<\/h2>

2.1 TCP客户端实现<\/h3>
public<\/span> class<\/span> TcpClient<\/span> {<\/span>
<\/span><\/span>    public<\/span> static<\/span> String ip =<\/span> "x.x.x.x"<\/span>;<\/span>
<\/span><\/span>    public<\/span> static<\/span> int<\/span> port =<\/span> xxxx;<\/span>
<\/span><\/span>    public<\/span> static<\/span> boolean<\/span> connected =<\/span> false<\/span>;<\/span>
<\/span><\/span>    public<\/span> static<\/span> Socket socket =<\/span> null<\/span>;<\/span>
<\/span><\/span>    public<\/span> static<\/span> OutputStream outputstream =<\/span> null<\/span>;<\/span>
<\/span><\/span>    public<\/span> static<\/span> InputStream inputStream =<\/span> null<\/span>;<\/span>
<\/span><\/span>    
<\/span><\/span>    \/\/ 主要方法
<\/span><\/span><\/span><\/span>    public<\/span> static<\/span> void<\/span> start<\/span>()<\/span> {<\/span> servicethread();<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> close<\/span>()<\/span> {<\/span> \/* 关闭连接 *\/<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> sendmsg<\/span>(<\/span>final<\/span> String msg)<\/span> {<\/span> \/* 发送消息 *\/<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> heartthread<\/span>()<\/span> {<\/span> \/* 心跳线程 *\/<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> receivethread<\/span>()<\/span> {<\/span> \/* 接收线程 *\/<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> servicethread<\/span>()<\/span> {<\/span> \/* 服务线程 *\/<\/span> }<\/span>
<\/span><\/span>}<\/span>
<\/span><\/span><\/code><\/pre>2.2 TCP发送数据调用链<\/h3>

java.net.SocketOutputStream.write(byte b[])<\/code><\/li>
java.net.SocketOutputStream.socketWrite(byte b[], int off, int len)<\/code><\/li>
java.net.SocketOutputStream.socketWrite0(FileDescriptor fd, byte[] b, int off, int len)<\/code> (JNI函数)<\/li>
<\/ol>
2.3 TCP接收数据调用链<\/h3>

java.net.SocketInputStream.read(byte b[])<\/code><\/li>
java.net.SocketInputStream.socketRead(byte b[], int off, int len)<\/code><\/li>
java.net.SocketInputStream.socketRead0(FileDescriptor fd, byte[] b, int off, int len)<\/code> (JNI函数)<\/li>
<\/ol>
2.4 TCP Hook代码示例<\/h3>
function<\/span> hooktcp<\/span>() {
<\/span><\/span>    Java<\/span>.perform<\/span>(function<\/span>() {
<\/span><\/span>        \/\/ Hook Socket构造函数
<\/span><\/span><\/span><\/span>        var<\/span> SocketClass<\/span> =<\/span> Java<\/span>.use<\/span>('java.net.Socket'<\/span>);
<\/span><\/span>        SocketClass<\/span>.$init<\/span>.overload<\/span>('java.lang.String'<\/span>, 'int'<\/span>).implementation<\/span> =<\/span> function<\/span>(arg0<\/span>, arg1<\/span>) {
<\/span><\/span>            console<\/span>.log<\/span>("["<\/span> +<\/span> Process<\/span>.getCurrentThreadId<\/span>() +<\/span> "]new Socket connection: "<\/span> +<\/span> arg0<\/span> +<\/span> "port: "<\/span> +<\/span> arg1<\/span>);
<\/span><\/span>            return<\/span> this<\/span>.$init<\/span>(arg0<\/span>, arg1<\/span>);
<\/span><\/span>        }
<\/span><\/span>        
<\/span><\/span>        \/\/ Hook socketRead0()
<\/span><\/span><\/span><\/span>        var<\/span> SocketInputStreamClass<\/span> =<\/span> Java<\/span>.use<\/span>('java.net.SocketInputStream'<\/span>);
<\/span><\/span>        SocketInputStreamClass<\/span>.socketRead0<\/span>.implementation<\/span> =<\/span> function<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>, arg4<\/span>) {
<\/span><\/span>            var<\/span> size<\/span> =<\/span> this<\/span>.socketRead0<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>, arg4<\/span>);
<\/span><\/span>            console<\/span>.log<\/span>("["<\/span> +<\/span> Process<\/span>.getCurrentThreadId<\/span>() +<\/span> "]socketRead0 > size: "<\/span> +<\/span> size<\/span>);
<\/span><\/span>            return<\/span> size<\/span>;
<\/span><\/span>        }
<\/span><\/span>        
<\/span><\/span>        \/\/ Hook socketWrite0()
<\/span><\/span><\/span><\/span>        var<\/span> SocketOutputStreamClass<\/span> =<\/span> Java<\/span>.use<\/span>('java.net.SocketOutputStream'<\/span>);
<\/span><\/span>        SocketOutputStreamClass<\/span>.socketWrite0<\/span>.implementation<\/span> =<\/span> function<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>) {
<\/span><\/span>            var<\/span> size<\/span> =<\/span> this<\/span>.socketWrite0<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>);
<\/span><\/span>            console<\/span>.log<\/span>("["<\/span> +<\/span> Process<\/span>.getCurrentThreadId<\/span>() +<\/span> "]socketWrite0 > size: "<\/span> +<\/span> arg3<\/span> +<\/span> "--content: "<\/span> +<\/span> JSON<\/span>.stringify<\/span>(arg1<\/span>));
<\/span><\/span>            return<\/span> size<\/span>;
<\/span><\/span>        }
<\/span><\/span>    });
<\/span><\/span>}
<\/span><\/span><\/code><\/pre>三、UDP Socket Hook点分析<\/h2>
3.1 UDP客户端实现<\/h3>
public<\/span> class<\/span> UdpClient<\/span> {<\/span>
<\/span><\/span>    public<\/span> static<\/span> final<\/span> String DEST_IP =<\/span> "x.x.x.x"<\/span>;<\/span>
<\/span><\/span>    public<\/span> static<\/span> final<\/span> int<\/span> DEST_PORT =<\/span> xxxx;<\/span>
<\/span><\/span>    public<\/span> static<\/span> final<\/span> int<\/span> DATA_LEN =<\/span> 4096<\/span>;<\/span>
<\/span><\/span>    public<\/span> static<\/span> byte<\/span>[]<\/span> inBuff =<\/span> new<\/span> byte<\/span>[<\/span>DATA_LEN];<\/span>
<\/span><\/span>    public<\/span> static<\/span> DatagramSocket socket;<\/span>
<\/span><\/span>    
<\/span><\/span>    \/\/ 主要方法
<\/span><\/span><\/span><\/span>    public<\/span> static<\/span> void<\/span> udpsend<\/span>(<\/span>String content)<\/span> {<\/span> \/* 发送UDP数据 *\/<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> receivethread<\/span>()<\/span> {<\/span> \/* 接收线程 *\/<\/span> }<\/span>
<\/span><\/span>    public<\/span> static<\/span> void<\/span> start<\/span>()<\/span> {<\/span> \/* 启动UDP客户端 *\/<\/span> }<\/span>
<\/span><\/span>}<\/span>
<\/span><\/span><\/code><\/pre>3.2 UDP发送数据调用链<\/h3>

java.net.DatagramSocket.send(DatagramPacket p)<\/code><\/li>
java.net.PlainDatagramSocketImpl.send(DatagramPacket p)<\/code><\/li>
libcore.io.IoBridge.sendto(FileDescriptor fd, byte[] bytes, int byteOffset, int byteCount, int flags, InetAddress inetAddress, int port)<\/code><\/li>
libcore.io.Libcore.os.sendto(fd, bytes, byteOffset, byteCount, flags, inetAddress, port)<\/code><\/li>
libcore.io.BlockGuardOs.os.sendto(fd, bytes, byteOffset, byteCount, flags, inetAddress, port)<\/code><\/li>
libcore.io.ForwardingOs.os.sendto.(fd, bytes, byteOffset, byteCount, flags, inetAddress, port)<\/code><\/li>
libcore.io.Linux.sendto(FileDescriptor fd, byte[] bytes, int byteOffset, int byteCount, int flags, InetAddress inetAddress, int port)<\/code><\/li>
libcore.io.Linux.sendtoBytes(FileDescriptor fd, Object buffer, int byteOffset, int byteCount, int flags, InetAddress inetAddress, int port)<\/code> (JNI函数)<\/li>
<\/ol>
3.3 UDP接收数据调用链<\/h3>

java.net.DatagramSocket.receive(DatagramPacket p)<\/code><\/li>
java.net.PlainDatagramSocketImpl.receive(DatagramPacket p)<\/code><\/li>
libcore.io.IoBridge.recvfrom(FileDescriptor fd, byte[] bytes, int byteOffset, int byteCount, int flags, InetSocketAddress srcAddress)<\/code><\/li>
libcore.io.Libcore.os.recvfrom(fd, bytes, byteOffset, byteCount, flags, srcAddress)<\/code><\/li>
libcore.io.BlockGuardOs.os.recvfrom(fd, bytes, byteOffset, byteCount, flags, srcAddress)<\/code><\/li>
libcore.io.ForwardingOs.os.recvfrom(fd, bytes, byteOffset, byteCount, flags, srcAddress)<\/code><\/li>
libcore.io.Linux.recvfrom(FileDescriptor fd, byte[] bytes, int byteOffset, int byteCount, int flags, InetSocketAddress srcAddress)<\/code><\/li>
libcore.io.Linux.recvfromBytes(FileDescriptor fd, Object buffer, int byteOffset, int byteCount, int flags, InetSocketAddress srcAddress)<\/code> (JNI函数)<\/li>
<\/ol>
3.4 UDP Hook代码示例<\/h3>
function<\/span> hookudp<\/span>() {
<\/span><\/span>    Java<\/span>.perform<\/span>(function<\/span>() {
<\/span><\/span>        var<\/span> LinuxClass<\/span> =<\/span> Java<\/span>.use<\/span>('libcore.io.Linux'<\/span>);
<\/span><\/span>        
<\/span><\/span>        \/\/ Hook 数据接收
<\/span><\/span><\/span><\/span>        LinuxClass<\/span>.recvfromBytes<\/span>.implementation<\/span> =<\/span> function<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>, arg4<\/span>, arg5<\/span>) {
<\/span><\/span>            var<\/span> size<\/span> =<\/span> this<\/span>.recvfromBytes<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>, arg4<\/span>, arg5<\/span>);
<\/span><\/span>            var<\/span> byteArray<\/span> =<\/span> Java<\/span>.array<\/span>('byte'<\/span>, arg1<\/span>);
<\/span><\/span>            var<\/span> content<\/span> =<\/span> ""<\/span>;
<\/span><\/span>            for<\/span>(var<\/span> i<\/span> =<\/span> 0<\/span>; i<\/span> <<\/span> size<\/span>; i<\/span>++<\/span>){
<\/span><\/span>                content<\/span> =<\/span> content<\/span> +<\/span> String.fromCharCode<\/span>(byteArray<\/span>[i<\/span>]);
<\/span><\/span>            }
<\/span><\/span>            console<\/span>.log<\/span>("address"<\/span> +<\/span> arg5<\/span> +<\/span> "["<\/span> +<\/span> Process<\/span>.getCurrentThreadId<\/span>() +<\/span> "]socketRead0 > size: "<\/span> +<\/span> size<\/span> +<\/span> "--content: "<\/span> +<\/span> content<\/span>);
<\/span><\/span>            printJavaStack<\/span>('recvfromBytes...'<\/span>);
<\/span><\/span>            return<\/span> size<\/span>;
<\/span><\/span>        }
<\/span><\/span>        
<\/span><\/span>        \/\/ Hook 数据发送
<\/span><\/span><\/span><\/span>        LinuxClass<\/span>.sendtoBytes<\/span>.overload<\/span>('java.io.FileDescriptor'<\/span>, 'java.lang.Object'<\/span>, 'int'<\/span>, 'int'<\/span>, 'int'<\/span>, 'java.net.InetAddress'<\/span>, 'int'<\/span>).implementation<\/span> =<\/span> function<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>, arg4<\/span>, arg5<\/span>, arg6<\/span>) {
<\/span><\/span>            var<\/span> size<\/span> =<\/span> this<\/span>.sendtoBytes<\/span>(arg0<\/span>, arg1<\/span>, arg2<\/span>, arg3<\/span>, arg4<\/span>, arg5<\/span>, arg6<\/span>);
<\/span><\/span>            var<\/span> byteArray<\/span> =<\/span> Java<\/span>.array<\/span>('byte'<\/span>, arg1<\/span>);
<\/span><\/span>            var<\/span> content<\/span> =<\/span> ""<\/span>;
<\/span><\/span>            for<\/span>(var<\/span> i<\/span> =<\/span> 0<\/span>; i<\/span> <<\/span> size<\/span>; i<\/span>++<\/span>){
<\/span><\/span>                content<\/span> =<\/span> content<\/span> +<\/span> String.fromCharCode<\/span>(byteArray<\/span>[i<\/span>]);
<\/span><\/span>            }
<\/span><\/span>            console<\/span>.log<\/span>("address"<\/span> +<\/span> arg5<\/span> +<\/span> ":"<\/span> +<\/span> arg6<\/span> +<\/span> "["<\/span> +<\/span> Process<\/span>.getCurrentThreadId<\/span>() +<\/span> "]sendtoBytes > len: "<\/span> +<\/span> size<\/span> +<\/span> "--content: "<\/span> +<\/span> content<\/span>);
<\/span><\/span>            printJavaStack<\/span>('sendtoBytes()...'<\/span>);
<\/span><\/span>            return<\/span> size<\/span>;
<\/span><\/span>        }
<\/span><\/span>    });
<\/span><\/span>}
<\/span><\/span><\/code><\/pre>四、Hook点选择策略<\/h2>
4.1 关键Hook点选择<\/h3>


构造函数Hook<\/strong>：监控Socket创建时的目标地址和端口<\/p>

java.net.Socket.$init<\/code><\/li>
java.net.DatagramSocket.$init<\/code><\/li>
<\/ul>
<\/li>

数据传输Hook<\/strong>：监控实际发送和接收的数据<\/p>

TCP: socketWrite0<\/code>和socketRead0<\/code><\/li>
UDP: sendtoBytes<\/code>和recvfromBytes<\/code><\/li>
<\/ul>
<\/li>

连接状态Hook<\/strong>：监控连接建立和关闭<\/p>

Socket.connect()<\/code><\/li>
Socket.close()<\/code><\/li>
<\/ul>
<\/li>
<\/ol>
4.2 Hook点选择建议<\/h3>

精确监控<\/strong>：选择调用链最底层的Java方法，避免上层封装带来的干扰<\/li>
性能考虑<\/strong>：Hook点越底层，对性能影响越小<\/li>
数据完整性<\/strong>：选择能获取完整数据包的方法进行Hook<\/li>
<\/ol>
五、实际应用场景<\/h2>
5.1 安全分析场景<\/h3>

协议分析<\/strong>：通过Hook获取应用通信协议格式<\/li>
加密分析<\/strong>：定位加密函数调用位置<\/li>
漏洞挖掘<\/strong>：发现明文传输等安全问题<\/li>
<\/ol>
5.2 逆向工程场景<\/h3>

协议逆向<\/strong>：还原私有通信协议<\/li>
数据拦截<\/strong>：获取应用通信内容<\/li>
功能模拟<\/strong>：模拟客户端与服务端通信<\/li>
<\/ol>
六、注意事项<\/h2>

Android版本差异<\/strong>：不同Android版本的Socket实现可能有差异，需要根据目标版本调整Hook点<\/li>
多线程处理<\/strong>：Socket操作通常在多线程中进行，Hook时需注意线程上下文<\/li>
性能影响<\/strong>：高频网络操作时，复杂的Hook逻辑可能影响应用性能<\/li>
反调试检测<\/strong>：部分应用会检测Hook行为，需要采取对抗措施<\/li>
<\/ol>
七、扩展知识<\/h2>
7.1 Native层Hook<\/h3>
除了Java层Hook外，还可以考虑Hook底层的JNI函数：<\/p>

socketWrite0<\/code>和socketRead0<\/code>的Native实现<\/li>
sendtoBytes<\/code>和recvfromBytes<\/code>的Native实现<\/li>
<\/ul>
7.2 SSL\/TLS Hook<\/h3>
对于HTTPS等加密通信，可以Hook以下类：<\/p>

javax.net.ssl.SSLSocket<\/code><\/li>
org.conscrypt.OpenSSLSocketImpl<\/code><\/li>
com.android.org.conscrypt.ConscryptFileDescriptorSocket<\/code><\/li>
<\/ul>
八、参考资源<\/h2>

Java层socket抓包与源码分析（上）<\/a><\/li>
Java层socket抓包与源码分析（下）<\/a><\/li>
Android源码：AOSP中libcore<\/code>和frameworks\/base<\/code>相关实现<\/li>
<\/ol>
Android Java层Socket Hook点分析教学文档<\/h1>

一、Socket基础实现<\/h2>

二、TCP Socket Hook点分析<\/h2>

三、UDP Socket Hook点分析<\/h2>

四、Hook点选择策略<\/h2>

五、实际应用场景<\/h2>

七、扩展知识<\/h2>

八、参考资源<\/h2> Java层socket抓包与源码分析（上）<\/a><\/li> Java层socket抓包与源码分析（下）<\/a><\/li> Android源码：AOSP中libcore<\/code>和frameworks\/base<\/code>相关实现<\/li> <\/ol>

八、参考资源<\/h2>

Java层socket抓包与源码分析（上）<\/a><\/li>
Java层socket抓包与源码分析（下）<\/a><\/li>
Android源码：AOSP中`libcore<\/code>和frameworks\/base<\/code>相关实现<\/li> <\/ol>`
