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[原创]通过DVM指令还原壳的抽空类
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发表于: 2023-1-13 16:53
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首先参考阅读这篇文章
ART 在 Android 安全攻防中的应用
code_item指令会执行到Execute函数
来自于EnterInterpreterFromInvoke的调用
对应于我的libart.so的地址分别是0x002D8F40 和 0x002D85C0
在0x002D8F40处下断点，第二个参数即为DexFile::CodeItem*的值
地址指针为esp+0x4处
根据CodeItem的定义可以得知
指令的长度为CodeItem+0xC的值*2+0x10
有了这两个参数就可以实时的导出所运行的指令
处于测试的目的我手动调用JAVA函数，并在每一条JAVA指令下打印LOG
最终结果如下
日志信息为
修复时首先在class_def_item 中找到指定的类
然后在encoded_method_list中找到需要修复的函数，就可以跳转到对应的code_item
原始的code_item的值如下
日志中的值为
直接二进制替换
我一共修复了3个函数，分别为getEncString、getEncCode和parseByte2HexStr
对比一下原始的反编译效果如下
以下是修复后的效果
267 static inline JValue Execute(
268 Thread* self,
269 const DexFile::CodeItem* code_item,
270 ShadowFrame& shadow_frame,
271 JValue result_register,
272 bool stay_in_interpreter = false) SHARED_REQUIRES(Locks::mutator_lock_)
267 static inline JValue Execute(
268 Thread* self,
269 const DexFile::CodeItem* code_item,
270 ShadowFrame& shadow_frame,
271 JValue result_register,
272 bool stay_in_interpreter = false) SHARED_REQUIRES(Locks::mutator_lock_)
391 void EnterInterpreterFromInvoke(Thread* self, ArtMethod* method, Object* receiver,
392 uint32_t* args, JValue* result,
393 bool stay_in_interpreter)
391 void EnterInterpreterFromInvoke(Thread* self, ArtMethod* method, Object* receiver,
392 uint32_t* args, JValue* result,
393 bool stay_in_interpreter)
280 // Raw code_item.
281 struct CodeItem {
282 uint16_t registers_size_; // the number of registers used by this code
283 // (locals + parameters)
284 uint16_t ins_size_; // the number of words of incoming arguments to the method
285 // that this code is for
286 uint16_t outs_size_; // the number of words of outgoing argument space required
287 // by this code for method invocation
288 uint16_t tries_size_; // the number of try_items for this instance. If non-zero,
289 // then these appear as the tries array just after the
290 // insns in this instance.
291 uint32_t debug_info_off_; // file offset to debug info stream
292 uint32_t insns_size_in_code_units_; // size of the insns array, in 2 byte code units
293 uint16_t insns_[1]; // actual array of bytecode.
294295 private:
296 DISALLOW_COPY_AND_ASSIGN(CodeItem);
297 };
280 // Raw code_item.
281 struct CodeItem {
282 uint16_t registers_size_; // the number of registers used by this code
283 // (locals + parameters)
284 uint16_t ins_size_; // the number of words of incoming arguments to the method
285 // that this code is for
286 uint16_t outs_size_; // the number of words of outgoing argument space required
287 // by this code for method invocation
288 uint16_t tries_size_; // the number of try_items for this instance. If non-zero,
289 // then these appear as the tries array just after the
290 // insns in this instance.
291 uint32_t debug_info_off_; // file offset to debug info stream
292 uint32_t insns_size_in_code_units_; // size of the insns array, in 2 byte code units
293 uint16_t insns_[1]; // actual array of bytecode.
294295 private:
296 DISALLOW_COPY_AND_ASSIGN(CodeItem);
297 };
function hook_art_module(){ var art_module = Module.findBaseAddress("libart.so");
var Execute = art_module.add(0x002D8F40);
Interceptor.attach(Execute, {
onEnter: function(args)
{
var vm_addr = Memory.readPointer((this.context.esp).add(0x4));
var vm_size = Memory.readUInt(vm_addr.add(0xC));
var code_size = vm_size*2+0x10;
console.log(hexdump(vm_addr, {
offset: 0,
length: code_size,
header: true,
ansi: true
}));
},
onLeave: function (retval) {
}
});
}function hook_art_module(){ var art_module = Module.findBaseAddress("libart.so");
var Execute = art_module.add(0x002D8F40);
Interceptor.attach(Execute, {
onEnter: function(args)
{
var vm_addr = Memory.readPointer((this.context.esp).add(0x4));
var vm_size = Memory.readUInt(vm_addr.add(0xC));
var code_size = vm_size*2+0x10;
console.log(hexdump(vm_addr, {
offset: 0,
length: code_size,
header: true,
ansi: true
}));
},
onLeave: function (retval) {
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最后于 2023-1-16 16:19
被易之生生编辑
，原因： 标点符号
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1、因为是X86环境下实时调试的 堆栈传值是在esp+0x4处 2、是IDA识别时的问题 已更正 |
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懂了 感谢大佬 |
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等等 我还是有疑问 就算是x86环境 此时程序断在函数头 也就是刚执行了call指令 那么esp此时存的应该是返回地址 esp+4是第一个参数 那么第二个参数应该是存在esp+8才对呀 |
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