java远程执行调试类

package com.dfb.dong.loader;
/**
* 為了多次載入執行類而加入的加载器
* 把defineClass方法开放出来，只有外部显式调用的时候才会使用到loadByte方法
* 由虚拟机调用时，仍然按照原有的双亲委派规则使用loadClass方法进行类加载
* @author zhoudong
*
*/
public class HotSwapClassLoader extends ClassLoader{

public HotSwapClassLoader()
{
super(HotSwapClassLoader.class.getClassLoader());
}

@SuppressWarnings("rawtypes")
public Class loadByte(byte [] classByte)
{
return defineClass(null, classByte,0,classByte.length);
}
}

package com.dfb.dong.modifier;

import com.dfb.dong.util.ByteUtils;

/**
* 修改Class文件，暂时只提供修改常量池常量的功能
* @author zhoudong
*
*/
public class ClassModifier {

/**
* Class文件中常量池的起始偏移
*/
private static final int CONSTANT_POOL_COUNT_INDEX = 8;
/**
* CONSTANT_Uff8_info常量的tag标志
*/
private static final int CONSTANT_Utf8_info = 1;
/**
* 常量池中11中常量所占的长度，CONSTATN_UTF8_INFO型常量除外，因为它不是定长的
*/
private static final int [] CONSTANT_ITEM_LENGTH={-1,-1,-1,5,5,9,9,3,3,5,5,5,5};
private static final int u1 = 1;
private static final int u2 = 2;

private byte[] classByte;

public ClassModifier(byte []classByte)
{
this.classByte = classByte;
}
/**
* 修改常量池中CONSTANT_Uft8_info常量的内容
* @param oldStr 修改前的字符串
* @param newStr 修改后的字符串
* @return 修改结果
*/
public byte[] modifyUTF8Constant(String oldStr,String newStr)
{
int cpc = getConstantPoolCount();//获取常量值
int offset = CONSTANT_POOL_COUNT_INDEX + u2;//常量值开始位置，常量表示符占两个字节
for(int i=0;i<cpc;i++)
{
int tag = ByteUtils.bytes2Int(classByte, offset, u1);//常量值占一个字节
if(tag == CONSTANT_Utf8_info)//常量标志
{
int len = ByteUtils.bytes2Int(classByte, offset+u1, u2);//一个常量占两个字节
offset += (u1+u2);
String str = ByteUtils.bytes2String(classByte, offset, len);
if(str.equalsIgnoreCase(oldStr))
{
byte[] strBytes = ByteUtils.string2Bytes(newStr);
byte[] strLen = ByteUtils.int2Bytes(newStr.length(), u2);
classByte = ByteUtils.bytesReplace(classByte, offset-u2, u2, strLen);
classByte = ByteUtils.bytesReplace(classByte, offset, len, strBytes);
return classByte;
}else{
offset += len;
}
}else{
offset += CONSTANT_ITEM_LENGTH[tag];
}
}
return classByte;

}
/**
* 获取常量池中常量的数量
* @return 常量池数量
*/
private int getConstantPoolCount() {
return ByteUtils.bytes2Int(classByte, CONSTANT_POOL_COUNT_INDEX, u2);//常量池数量值占两个字节，从class文件的第八位到第十位为常量池数量位置
}
}

package com.dfb.dong.system;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.PrintStream;

/**
* 为JavaClass劫持java.lang.System提供支持
* 除了out和err外，其余的都直接转发给System处理
* @author zhoudong
*
*/
public class HackSystem {

public final static InputStream in = System.in;
private static ByteArrayOutputStream buffer = new ByteArrayOutputStream();
public final static PrintStream out = new PrintStream(buffer);
public final static PrintStream err = out;
public static String getBufferString()
{
return buffer.toString();
}
public static void clearBuffer()
{
buffer.reset();
}
public static void setSecurityManager(final SecurityManager s)
{
System.setSecurityManager(s);
}
public static SecurityManager getSecurityManager()
{
return System.getSecurityManager();
}
public static long currentTimeMillis()
{
return System.currentTimeMillis();
}
public static void arraycopy(Object src,int srcPos,Object dest,int destPos,
int length)
{
System.arraycopy(src, srcPos, dest, destPos, length);
}
public static int identityHashCode(Object x)
{
return System.identityHashCode(x);
}
/**
* 下面所有的方法都与java.lang.System的名称一样
* 实现都是字节转调System的对应方法
*/
}

package com.dfb.dong.util;
/**
* Bytes 数组处理工具
* @author zhoudong
*
*/
public class ByteUtils {

public static int bytes2Int(byte[] b,int start,int len)
{
int sum = 0;
int end = start + len;
for(int i=start;i<end;i++)
{
int n = ((int)b[i]) & 0xff;
n<<=(--len)*8;
sum = n + sum;
}
return sum;
}

public static byte[] int2Bytes(int value,int len)
{
byte[] b = new byte[len];
for(int i=0;i<len;i++)
{
b[len-i-1] = (byte) ((value>>8*i)&0xff);
}
return b;
}

public static String bytes2String(byte[]b,int start,int len)
{
return new String(b,start,len);
}
public static byte[] string2Bytes(String str)
{
return str.getBytes();
}
public static byte[] bytesReplace(byte[] originalBytes,int offset,int len,byte[] replaceBytes)
{
byte[] newBytes = new byte[originalBytes.length+(replaceBytes.length-len)];
System.arraycopy(originalBytes, 0, newBytes, 0, offset);
System.arraycopy(replaceBytes, 0, newBytes, offset, replaceBytes.length);
System.arraycopy(originalBytes, offset+len,newBytes ,offset+replaceBytes.length,
originalBytes.length-offset-len);
return newBytes;
}
}

package com.dfb.dong.executer;

import java.lang.reflect.Method;

import com.dfb.dong.loader.HotSwapClassLoader;
import com.dfb.dong.modifier.ClassModifier;
import com.dfb.dong.system.HackSystem;

/**
* JavaClass执行工具
* @author zhoudong
*
*/
public class JavaClassExecuter {

/**
* 执行外部传过来的代表一个Java类的byte数组
* 将输入类的byte数组中代表java.lang.System的CONSTANT_Uft8_info常量修改为劫持后的HackSystem类
* 执行方法为该类的static main(String [] atgs)方法，输出结果为该类向System.out/err输出的信息
*
* @param classByte 代表一个java类的byte数组
* @return 执行结果
*/
public static String excute(byte [] classByte)
{
HackSystem.clearBuffer();
ClassModifier cm = new ClassModifier(classByte);
byte[] modiBytes = cm.modifyUTF8Constant("java/lang/System", "com/dfb/dong/system/HackSystem");
HotSwapClassLoader loader = new HotSwapClassLoader();
Class clazz = loader.loadByte(modiBytes);
try {
Method method = clazz.getMethod("main", new Class[]{String[].class});
method.invoke(null, new String[]{null});
} catch (Throwable e) {
e.printStackTrace(HackSystem.out);
}
return HackSystem.getBufferString();
}
}