Java安全之动态加载字节码( 五 ) _生活百科

首先得设置TemplatesImpl对象的三个私有属性，这里我们用反射设置就行，三个属性：_bytecodes、 _name 和 _tfactory

_name：为任意字符串，只要不是null才可以进入defineTransletClasses()

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_bytecodes：由字节码组成的数组，用来存放恶意代码，其值不能为null
_tfactory 需要是一个 TransformerFactoryImpl 对象，因为TemplatesImpl#defineTransletClasses() 方法里有调用_tfactory.getExternalExtensionsMap()，如果是null会出错

另外TemplatesImpl 中对加载的字节码是有一定要求的：这个字节码对应的类必须是com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet 的子类所以，我们需要构造一个特殊的类：
package org.gk0d;import com.sun.org.apache.xalan.internal.xsltc.DOM;import com.sun.org.apache.xalan.internal.xsltc.TransletException;import com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet;import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;import com.sun.org.apache.xml.internal.serializer.SerializationHandler;public class HelloTemplatesImpl extends AbstractTranslet { public void transform(DOM document, SerializationHandler[] handlers) throws TransletException {} public void transform(DOM document, DTMAxisIterator iterator, SerializationHandler handler) throws TransletException {} public HelloTemplatesImpl() { super(); System.out.println("Hello TemplatesImpl"); }}解释以下为什么多了两个transform方法
这里是因为子类需要实现父类里面的抽象方法，同时因为父类是抽象类，可能没有将接口的方法全部实现，这时子类如果不是抽象的，那必须将其他接口方法都实现。这里面 `transform(DOM document, DTMAxisIterator iterator,SerializationHandler handler)是父类里面的抽象方法所以要重写transform(DOM document, SerializationHandler[] handlers)是父类没有实现接口的方法所以要重写同样将其编译为class文件，然后base64编码最后就是写poc了,就新建一个TemplatesImpl对象，把属性设置进去然后执行newTransformer方法触发，主要是咱得先写一个利用反射给私有属性赋值的一个方法setFieldValue：
package org.gk0d;import com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl;import com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl;import java.lang.reflect.Field;import java.util.Base64;public class a { public static void setFieldValue(Object obj, String fieldName, Object Value) throws Exception { Field field = obj.getClass().getDeclaredField(fieldName); field.setAccessible(true); field.set(obj, Value); } public static void main(String[] args) throws Exception {// source: bytecodes/HelloTemplateImpl.java byte[] code = Base64.getDecoder().decode("yv66vgAAADQAIQoABgASCQATABQIABUKABYAFwcAGAcAGQEA" + "CXRyYW5zZm9ybQEAcihMY29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL0RP" + "TTtbTGNvbS9zdW4vb3JnL2FwYWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0" + "aW9uSGFuZGxlcjspVgEABENvZGUBAA9MaW5lTnVtYmVyVGFibGUBAApFeGNlcHRpb25zBwAaAQCm" + "KExjb20vc3VuL29yZy9hcGFjaGUveGFsYW4vaW50ZXJuYWwveHNsdGMvRE9NO0xjb20vc3VuL29y" + "Zy9hcGFjaGUveG1sL2ludGVybmFsL2R0bS9EVE1BeGlzSXRlcmF0b3I7TGNvbS9zdW4vb3JnL2Fw" + "YWNoZS94bWwvaW50ZXJuYWwvc2VyaWFsaXplci9TZXJpYWxpemF0aW9uSGFuZGxlcjspVgEABjxp" + "bml0PgEAAygpVgEAClNvdXJjZUZpbGUBABdIZWxsb1RlbXBsYXRlc0ltcGwuamF2YQwADgAPBwAb" + "DAAcAB0BABNIZWxsbyBUZW1wbGF0ZXNJbXBsBwAeDAAfACABABJIZWxsb1RlbXBsYXRlc0ltcGwB" + "AEBjb20vc3VuL29yZy9hcGFjaGUveGFsYW4vaW50ZXJuYWwveHNsdGMvcnVudGltZS9BYnN0cmFj" + "dFRyYW5zbGV0AQA5Y29tL3N1bi9vcmcvYXBhY2hlL3hhbGFuL2ludGVybmFsL3hzbHRjL1RyYW5z" + "bGV0RXhjZXB0aW9uAQAQamF2YS9sYW5nL1N5c3RlbQEAA291dAEAFUxqYXZhL2lvL1ByaW50U3Ry" + "ZWFtOwEAE2phdmEvaW8vUHJpbnRTdHJlYW0BAAdwcmludGxuAQAVKExqYXZhL2xhbmcvU3RyaW5n" + "OylWACEABQAGAAAAAAADAAEABwAIAAIACQAAABkAAAADAAAAAbEAAAABAAoAAAAGAAEAAAAIAAsA" + "AAAEAAEADAABAAcADQACAAkAAAAZAAAABAAAAAGxAAAAAQAKAAAABgABAAAACgALAAAABAABAAwA" + "AQAOAA8AAQAJAAAALQACAAEAAAANKrcAAbIAAhIDtgAEsQAAAAEACgAAAA4AAwAAAA0ABAAOAAwA" + "DwABABAAAAACABE="); TemplatesImpl obj = new TemplatesImpl(); setFieldValue(obj, "_bytecodes", new byte[][]{code}); setFieldValue(obj, "_name", "HelloTemplatesImpl"); setFieldValue(obj, "_tfactory", new TransformerFactoryImpl()); obj.newTransformer(); }}