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【ACTF2022】Inflated（C++异常处理控制流下的OLLVM混淆）
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发表于: 2022-7-21 18:03
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一般碰到C++异常逆向，确定了异常分发、处理部分，直接把call throw改为jmp catch块，再F5即可
PS: 多个catch块根据rdx来当为异常处理数值决定哪个为对应的catch块
（关于以上，这篇讲的很详细）
https://4nsw3r.top/2022/02/03/SCTF-REVERSE-CplusExceptionEncrypt-%E8%B5%9B%E5%90%8E%E5%A4%8D%E7%8E%B0/#Clang-x64
然而，这题没这么简单，套了个ollvm！？基于异常处理的ollvm，无论从哪个角度都没法使用之前的老套路
耐心看完这两篇文章就会有所收获，对于此题的被异常处理搞乱掉的cfg就会有所理解
https://www.cnblogs.com/catch/p/3604516.html
https://www.cnblogs.com/catch/p/3619379.html
要是平常的ollvm都可以按照这篇来解决
https://bluesadi.github.io/0x401RevTrain-Tools/angr/10_%E5%88%A9%E7%94%A8angr%E7%AC%A6%E5%8F%B7%E6%89%A7%E8%A1%8C%E5%8E%BB%E9%99%A4%E6%8E%A7%E5%88%B6%E6%B5%81%E5%B9%B3%E5%9D%A6%E5%8C%96/
其他的原理讲的非常好，问题是这题并不是那么简单，但为了去ollvm我们的思路也是一样的，所以要对ollvm的cfg熟悉，并懂得我们该如何恢复一个被ollvm混淆后的代码
现在就开始写我对这题的看法！
参考Write up:
https://github.com/Lnkvct/CTF-for-Fun/blob/main/Challenges/Inflated-ACTF2022/writeup.md
https://www.cnblogs.com/FW-ltlly/p/16472171.html
lchild师傅的Write up（pdf所以没法给链接）
（感觉好久没写wp了）
无壳64位
在讲这题ollvm与异常处理之前，有必要先搞懂我们到底是怎么输入的
一共有三处getc处理我们第一段输入的地方
程序最先开始运行的是 407629，这里我们可以输入上下左右箭头与特定的数字
（同时我们的输入还会决定异常类型）
Official Write up: The value of the first field of the thrown StdObfException object comes from the second input passed to the construct of StdObfException.
（这图好大...有没有什么办法处理这些图片还有博客页面的方法）
那么异常处理先不深究，继续回来箭头如何处理这个问题
那么箭头其实为三字节码，上下左右箭头分别对应 ^[[A ^[[B ^[[C ^[[D
（此时开始动调，我第一次输入为上箭头，同时注意RAX）
那么在 407629 第一次处理箭头会读取为1B
随后到 40553A 读取为5B
最后到达 405676 可以发现我们的上箭头代码所对应的字符为A
以上就解释了第一段输入的处理，等到最后解密第一段输入就会用到此
引用这张图，想要去掉ollvm最基本的是要认识这几个块
https://security.tencent.com/index.php/blog/msg/112
先抛去原题，来认识一下这些名词
那参考文章，总结来说，利用angr符号执行去除控制流平坦化的步骤可以归结为三个步骤：
简单来说就是获取所有的块，利用angr符号执行我们的真实块，查看真实块之间的流程，再抛去我们不要的块，patch程序，完成！
（那么具体的实现看文章）
https://bluesadi.github.io/0x401RevTrain-Tools/angr/10_%E5%88%A9%E7%94%A8angr%E7%AC%A6%E5%8F%B7%E6%89%A7%E8%A1%8C%E5%8E%BB%E9%99%A4%E6%8E%A7%E5%88%B6%E6%B5%81%E5%B9%B3%E5%9D%A6%E5%8C%96/
然而这题...，根本不像啊！可以看出这题的CFG根本看不懂，不像单单ollvm混淆过的cfg那么漂亮
为了搞懂CFG为什么成这样了，得先了解下异常的原理，参考原文
https://www.cnblogs.com/catch/p/3604516.html
对于最基本的thown catch不再赘述，这篇讲到很清楚
https://4nsw3r.top/2022/02/03/SCTF-REVERSE-CplusExceptionEncrypt-%E8%B5%9B%E5%90%8E%E5%A4%8D%E7%8E%B0/#Clang-x64
如果当前函数没有catch，就沿着函数的调用链继续往上抛，然后出现两种情况
在某个函数中找到相应的catch
没找到相应的catch，调用 std::terminate() （这个函数是把程序abort）
如果想找到了相应的catch，执行相应的操作
从抛异常到开始 -> 执行Landing pad代码 这整个过程叫作Stack unwind
Stack unwind
stack unwind的过程可以简单看成函数调用的逆过程，这个过程在实现上由一个专门的stack unwind库来实现
stack unwind库在intel平台上
属于Itanium ABI 接口中的一部分
ltanium C++ ABI定义了一系列函数以及数据结构来建立整个异常处理的流程及框架，主要函数包括以下列：
其中 _Unwind_RaiseException() 函数进行stack unwind，它在用户执行throw的时被调用
主要功能
从当前函数开始，对调用链上的每一个函数都调用一个叫做 personality routine 的函数（__gxx_personality_v0）
_Unwind_RaiseException() 会在内部把函数栈调用现场重现，然后传给 personality routine，该函数主要做两件事情
那么稍稍总结一下，就是当程序抛出异常就要进行 stack unwind 操作
而这个操作具体是 _Unwind_RaiseException() 中的 personality routine() 实现了检查catch和清理栈上的局部变量
基于前面介绍的 ltanium ABI，编译器层面也定义了一系列 ABI 与之交互
当我们在代码中写下 throw xxx，编译器会分配一个数据结构 __cxa_exception 来表示该异常，该异常也有一个头部，定义如下
当用户 throw 一个异常时，编译器会帮我们调用相应的函数分配出如下的结构
其中 __cxa_exception 就是头部，exception_obj 则是 "throw xxx" 中的 xxx，这两部分在内存中是连续的。
异常对象由函数 __cxa_allocate_exception() 进行创建
最后由 __cxa_free_exception() 进行销毁
当我们在程序里执行了抛出异常的操作，编译器为我们做了如下的事情：
总结太Bravo了！
有了这些前置知识，再看题目中的异常，由前面描述可知实现 unwind stack 的具体过程是通过 __gxx_personality_v0（即personality routine）实现
这时候我们再去IDA里调整此函数
光标在函数，按Y修改类型
scan_eh_tab
回忆__gxx_personality_v0函数功能
在personality routine()下的 scan_eh_tab() 该函数有我们最关心的两个值，同时也是魔改处
与源码对比：https://code.woboq.org/llvm/libcxxabi/src/cxa_personality.cpp.html#__cxxabiv1::scan_eh_tab
Shfit + F1 -> INS 导入结构体
光标在scan_eh_tab函数上按Y修改
Landing pad（指向catch块的分发处，只单单拿到landing pad还不够，这时候还缺少一个对应异常类型ttypeIndex）
首先要求父类为StdObfException的异常
最后的ttypeIndex由 thrown_object_ptr（由我们的第一段输入所决定的thrown_object_ptr） 和 原始固定固定typeIndex 决定
Official Write up: And we have figured out that the ttypeIndex is determined by the first field of the thrown StdObfException object and the lptinfo passed to __cxa_throw. The value of the first field of the thrown StdObfException object comes from the second input passed to the construct of StdObfException.
那么这两个值到底具体指的是什么？？
其实上面已经给出了答案，反复调试可知，可以发现我们的第一段输入设置了父类StdObfException
the first field of the thrown StdObfException object 指的就是我们的输入
the lptinfo passed to __cxa_throw 指的就是当 ___cxa_allocate_exception 创建的异常，也就是固定的
现在知道了魔改后的流程是从哪里来到哪里去，人工方式就是跳到landing pad再设置rdx为ttypeIndex就可以到达我们所对应的catch块
那么现在知道了routine personality 中的 scan_eh_tab被修改了，而IDA平常能识别throw catch这些块的原因就是这些正常的源码
然而landingpad与ttypeIndex都被修改了，所以导致了IDA识别的CFG成了这个样子
我们根本没法用肉眼知道throw的块在哪，只有通过动调才能确定，然而这就导致了原先的deflat脚本都不不行了
原因主要为两点
原因还有种种就不一一举例，就无法正常原先deflat所需要的CFG块
以下开始就是跟着官方脚本复现
我们再回忆一下正常的ollvm的执行流程
Prologue（入口块）-> Main dispatcher（主分发器）-> Sub dispathers（子分发器）-> Relevant blocks（真实块）-> Predispather（预分发器）-> Main dispatcher（主分发器）...
总结一下这道题的CFG
我们的下一个真实块取决于系统生产的lptinfo和我们的第一段输入所导致的StdObfException，在每个真实块的结束，我们不只是跳往与预分发器，而是调用 __cxa_throw 进行第二次调度，我们称二次调用为 second dispatch
所以我们的执行流就是
... -> main dispatcher -> sub dispatchers -> relevant block -> throw StdObfException exception -> Secondary dispatchers -> pre-dispatcher -> main dispatcher -> ...
除此之外，程序还抛出了一些真正的异常，对于这些异常，第二次调用发生于Landing pad末尾
... -> main dispatcher -> sub dispatchers -> relevant block that throws real exceptions -> the according real LandingPad block -> throw StdObfException exception -> Secondary dispatchers -> pre-dispatcher -> main dispatcher -> ...
去该平坦化控制流，有两个步骤：
我们可以从主分发器开始寻找，找到所有子分发器的后继者，这些后继者本身不是子分发器
官方WP中一眼丁真发现子分发器由该指令格式组成
于是由此区别出来
首先判断是否为子分发器，然后排除法找到所有真实块
Relevant blocks:
官网WP指出抽象出来）留个坑，以后熟了试试
Official Write up: A good idea is to abstract the throw StdObfException -> catch process and do the one basic block symbolic execution (You can refer to Deobfuscation: recovering an OLLVM-protected program or 利用符号执行去除控制流平坦化 for more information).
于是官网WP又给了个更有趣的方法，GDB脚本！
为了找到真实块之间的流程，通过普通的执行然后打印真实块需要的信息！
但是我们不一样能得到所有的流程因为部分可能没执行到，但是我们依然可以利用提取出来的信息去恢复部分控制流，并弄清楚如何输入可以恢复更多流程。（怎么好像梦到过我在这写wp...）
生成GDB的脚本如下
于是可以获取真实块接下来的landing pad与异常类型
然后就写个PARSER分析
Flows:
修复程序环节！
当我们已经确定了执行流程，像抛异常 子分发器什么都是多余的了，统统patch掉
对于后继块只有一个的真实块，只需要jmp过去
官方完整脚本
Work flow:
（按照以上流程，test.gdb可能会报个错，程序把本身有个\n是脚本中需要打印的，但直接转义成真换行了需要手动恢复）
观看修复后的流程
之前也提到过，由于我们的输入部分流可能执行不到，很明显我们刚刚根本没有输入上下左右箭头啥的
所以关于处理上下左右箭头的代码无了
这个时候就可以更改我们的输入（指的是输入箭头再输入字符）再来一遍
成功解析出我们的第一段输入
由于两个文件分析过程不贴了，可以直接看官方WP给出的源码
这个部分完全跟着lchild的分析来了
接着就是第二段输入
首先是经过一段Base64解码操作，再经过取模除十操作得到一个数组
之后计算了九个数值，和一堆pang臭的代码，不过干的事情不是很复杂
第一个循环是复制，后两个循环判断行列，不难发现这是个数独，拿网站一把梭了
具体参考lchild师傅的Write up
# https://sudoku.vip/sudoku-x-solver/
第一个解密就直接移回去即可
第二个解密出数独的值，列移动，取出值恢复原权位值，最后Base64即可！
最后输入上上下下右左右左3417再二段
GetFlag!!
对于我这种0 throw catch小白0 ollvm小白，过程中是补了不少文章...学识尚浅如果有错误的地方欢迎指出，一定会严加学习修改！
最后拿到flag，也是对这题的一个happy ending，真是REVERSE生涯中目前做的最难的一题了
回忆起最开始wjh师傅教我的unicorn再到Helen师傅出的login，这次又上了台阶！逆向真是越来越有趣了。--7.21 00:55
40762940553A（专门用来处理箭头）
405676（专门用来处理箭头）
40762940553A（专门用来处理箭头）
405676（专门用来处理箭头）
void func1(){ cs a; // stack unwind时被析构。
throw 3;
}void func2(){ cs b;
func1();
}void func3(){ cs c;
try
{
func2();
}
catch (int)
{
//进入这里之前， func1, func2已经被unwind.
}
}void func1(){ cs a; // stack unwind时被析构。
throw 3;
}void func2(){ cs b;
func1();
}void func3(){ cs c;
try
{
func2();
}
catch (int)
{
//进入这里之前， func1, func2已经被unwind.
}
}_Unwind_RaiseException,_Unwind_Resume,_Unwind_DeleteException,_Unwind_GetGR,_Unwind_SetGR,_Unwind_GetIP,_Unwind_SetIP,_Unwind_GetRegionStart,_Unwind_GetLanguageSpecificData,_Unwind_ForcedUnwind_Unwind_RaiseException,_Unwind_Resume,_Unwind_DeleteException,_Unwind_GetGR,_Unwind_SetGR,_Unwind_GetIP,_Unwind_SetIP,_Unwind_GetRegionStart,_Unwind_GetLanguageSpecificData,_Unwind_ForcedUnwindstruct __cxa_exception { std::type_info * exceptionType;
void (*exceptionDestructor) (void *);
unexpected_handler unexpectedHandler;
terminate_handler terminateHandler;
__cxa_exception * nextException;
int handlerCount;
int handlerSwitchValue;
const char * actionRecord;
const char * languageSpecificData;
void * catchTemp;
void * adjustedPtr;
_Unwind_Exception unwindHeader;
};struct __cxa_exception { std::type_info * exceptionType;
void (*exceptionDestructor) (void *);
unexpected_handler unexpectedHandler;
terminate_handler terminateHandler;
__cxa_exception * nextException;
int handlerCount;
int handlerSwitchValue;
const char * actionRecord;
const char * languageSpecificData;
void * catchTemp;
void * adjustedPtr;
_Unwind_Exception unwindHeader;
};_Unwind_Reason_Code __fastcall _gxx_personality_v0( int Version,
_Unwind_Action actions,
__int64 exceptionClass,
_Unwind_Exception *exceptionObject,
_Unwind_Context *context)
_Unwind_Reason_Code __fastcall _gxx_personality_v0( int Version,
_Unwind_Action actions,
__int64 exceptionClass,
_Unwind_Exception *exceptionObject,
_Unwind_Context *context)
struct scan_results{int64_t ttypeIndex; const uint8_t* actionRecord;
const uint8_t* languageSpecificData;
uintptr_t landingPad; void* adjustedPtr;
_Unwind_Reason_Code reason; };struct scan_results{int64_t ttypeIndex; const uint8_t* actionRecord;
const uint8_t* languageSpecificData;
uintptr_t landingPad; void* adjustedPtr;
_Unwind_Reason_Code reason; };void scan_eh_tab(scan_results *results, _Unwind_Action actions, bool native_exception, _Unwind_Exception *unwind_exception, _Unwind_Context *context)
void scan_eh_tab(scan_results *results, _Unwind_Action actions, bool native_exception, _Unwind_Exception *unwind_exception, _Unwind_Context *context)
sub dispathers such as:cmpjxsub dispathers such as:cmpjxisCmpRI = lambda instr: instr.mnemonic == "cmp" and\
hasattr(instr.operands[0], "_X86RegisterOperand__key") and\
hasattr(instr.operands[1], "_X86ImmediateOperand__key")
isCJmp = lambda instr: instr.mnemonic.startswith("j") and \
instr.mnemonic != "jmp"
isSubDispatcher = lambda bb: (len(bb.instrs) == 2) and\
isCmpRI(bb.instrs[0]) and isCJmp(bb.instrs[1])
isCmpRI = lambda instr: instr.mnemonic == "cmp" and\
hasattr(instr.operands[0], "_X86RegisterOperand__key") and\
hasattr(instr.operands[1], "_X86ImmediateOperand__key")
isCJmp = lambda instr: instr.mnemonic.startswith("j") and \
instr.mnemonic != "jmp"
isSubDispatcher = lambda bb: (len(bb.instrs) == 2) and\
isCmpRI(bb.instrs[0]) and isCJmp(bb.instrs[1])
class PatchHelper:
## ......
# To get all cfgs
def block(self, addr):
bb = self.cfg.find_basic_block(addr)
if bb is None:
bb = barf.bb_builder.strategy._disassemble_bb(addr, barf.binary.ea_end, {})
return bb
def get_relevant_blocks(cfg, patch_helper, main_dispatcher):
isCmpRI = lambda instr: instr.mnemonic == "cmp" and\
hasattr(instr.operands[0], "_X86RegisterOperand__key") and\
hasattr(instr.operands[1], "_X86ImmediateOperand__key")
isCJmp = lambda instr: instr.mnemonic.startswith("j") and \
instr.mnemonic != "jmp"
isSubDispatcher = lambda bb: (len(bb.instrs) == 2) and\
isCmpRI(bb.instrs[0]) and isCJmp(bb.instrs[1])
relevant_blocks = []
visited = set()
q = SimpleQueue()
q.put(patch_helper.block(main_dispatcher))
while not q.empty():
bb = q.get()
# Either Sub Patchers or Relevant blocks?
if isSubDispatcher(bb):
for succ, cond in bb.branches:
if succ in visited:
continue
q.put(patch_helper.block(succ))
visited.add(succ)
else:
relevant_blocks.append(bb)
return relevant_blocks
class PatchHelper:
## ......
# To get all cfgs
def block(self, addr):
bb = self.cfg.find_basic_block(addr)
if bb is None:
bb = barf.bb_builder.strategy._disassemble_bb(addr, barf.binary.ea_end, {})
return bb
def get_relevant_blocks(cfg, patch_helper, main_dispatcher):
isCmpRI = lambda instr: instr.mnemonic == "cmp" and\
hasattr(instr.operands[0], "_X86RegisterOperand__key") and\
hasattr(instr.operands[1], "_X86ImmediateOperand__key")
isCJmp = lambda instr: instr.mnemonic.startswith("j") and \
instr.mnemonic != "jmp"
isSubDispatcher = lambda bb: (len(bb.instrs) == 2) and\
isCmpRI(bb.instrs[0]) and isCJmp(bb.instrs[1])
relevant_blocks = []
visited = set()
q = SimpleQueue()
q.put(patch_helper.block(main_dispatcher))
while not q.empty():
bb = q.get()
# Either Sub Patchers or Relevant blocks?
if isSubDispatcher(bb):
for succ, cond in bb.branches:
if succ in visited:
continue
q.put(patch_helper.block(succ))
visited.add(succ)
else:
relevant_blocks.append(bb)
return relevant_blocks
*******************relevant blocks************************
main_dispatcher:0x404a80
relevant_blocks: ['0x409437', '0x406443', '0x404ab8', '0x408031', '0x407842', '0x407d31', '0x407437', '0x407f4f', '0x4076bd', '0x407a6b', '0x40723e', '0x407fc4', '0x409458', '0x407bc7', '0x40732f', '0x407ebc', '0x407566', '0x407960', '0x4070fa', '0x405e7a', '0x4078e3', '0x407e5a', '0x4074ca', '0x405c87', '0x407741', '0x407af5', '0x4072b4', '0x405ded', '0x4077b6', '0x407c6b', '0x4073a4', '0x405b29', '0x4075f9', '0x407a06', '0x4071aa', '0x406cfe', '0x406c94', '0x406ef0', '0x406859', '0x40707d', '0x406b62', '0x406f5f', '0x4065c9', '0x406e5d', '0x406a72', '0x406d7b', '0x406704', '0x406def', '0x406964', '0x40944b', '0x4064a5', '0x405469', '0x405a5f', '0x404fae', '0x40532c', '0x40589c', '0x404d58', '0x4053d3', '0x405923', '0x404ec5', '0x40529a', '0x4057b8', '0x404bc4', '0x405f2a', '0x4056f0', '0x406299', '0x4068f0', '0x4063b0', '0x406bf9', '0x406323', '0x406646', '0x40620f', '0x406b00', '0x4060e7', '0x4067bb', '0x40617c', '0x4069e3', '0x40606d', '0x406521', '0x4051fe', '0x405647', '0x404e14', '0x4055b5', '0x4050cc', '0x40550b', '0x404ca4']
*******************relevant blocks************************
main_dispatcher:0x404a80
relevant_blocks: ['0x409437', '0x406443', '0x404ab8', '0x408031', '0x407842', '0x407d31', '0x407437', '0x407f4f', '0x4076bd', '0x407a6b', '0x40723e', '0x407fc4', '0x409458', '0x407bc7', '0x40732f', '0x407ebc', '0x407566', '0x407960', '0x4070fa', '0x405e7a', '0x4078e3', '0x407e5a', '0x4074ca', '0x405c87', '0x407741', '0x407af5', '0x4072b4', '0x405ded', '0x4077b6', '0x407c6b', '0x4073a4', '0x405b29', '0x4075f9', '0x407a06', '0x4071aa', '0x406cfe', '0x406c94', '0x406ef0', '0x406859', '0x40707d', '0x406b62', '0x406f5f', '0x4065c9', '0x406e5d', '0x406a72', '0x406d7b', '0x406704', '0x406def', '0x406964', '0x40944b', '0x4064a5', '0x405469', '0x405a5f', '0x404fae', '0x40532c', '0x40589c', '0x404d58', '0x4053d3', '0x405923', '0x404ec5', '0x40529a', '0x4057b8', '0x404bc4', '0x405f2a', '0x4056f0', '0x406299', '0x4068f0', '0x4063b0', '0x406bf9', '0x406323', '0x406646', '0x40620f', '0x406b00', '0x4060e7', '0x4067bb', '0x40617c', '0x4069e3', '0x40606d', '0x406521', '0x4051fe', '0x405647', '0x404e14', '0x4055b5', '0x4050cc', '0x40550b', '0x404ca4']
cmds = """\
set pagination offb *0x40A3D4commands silent
printf "landingPad: %x\\n", $rdx
continue
endb _ZN18StdSubObfExceptionC2Eccommands silent
printf "selector: %x\\n", $rsi
continue
end define mytrace break $arg0
commands
silent
printf "%x\\n", $pc
python gdb.execute('continue')
end
end"""for bb in relevant_blocks:
cmds += (f"mytrace *{hex(bb.address)} \n")
cmds += "run\n"
with open("test.gdb", "w") as f:
f.write(cmds)
cmds = """\
set pagination offb *0x40A3D4commands silent
printf "landingPad: %x\\n", $rdx
continue
endb _ZN18StdSubObfExceptionC2Eccommands silent
printf "selector: %x\\n", $rsi
continue
end define mytrace break $arg0
commands
silent
printf "%x\\n", $pc
python gdb.execute('continue')
end
end"""for bb in relevant_blocks:
cmds += (f"mytrace *{hex(bb.address)} \n")
cmds += "run\n"
with open("test.gdb", "w") as f:
f.write(cmds)
cat teatin0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdefgdb inflated -x test.gdb --batch < testin > testout
cat teatin0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdefgdb inflated -x test.gdb --batch < testin > testout
Breakpoint 1 at 0x40a3d4
......Breakpoint 88 at 0x404ca4
4075f9selector: 0
landingPad: 4089bf
4072b4selector: 0
landingPad: 408503
4075f9selector: 2
landingPad: 4089bf
4060e7selector: 0
......40617cselector: 0
landingPad: 409100
409437[Inferior 1 (process 13732) exited normally]
Breakpoint 1 at 0x40a3d4
......Breakpoint 88 at 0x404ca4
4075f9selector: 0
landingPad: 4089bf
4072b4selector: 0
landingPad: 408503
4075f9selector: 2
landingPad: 4089bf
4060e7selector: 0
......40617cselector: 0
landingPad: 409100
409437[Inferior 1 (process 13732) exited normally]
def parse_logs(logfn, prologue, patch_helper):
with open(logfn, "r") as f:
t = f.readlines()
i = 0
selector_s = "selector: "
landingpad_s = "landingPad: "
relations = set()
laddr = prologue
lselector = 0
landingpad = 0
while i < len(t):
try:
addr = int(t[i], 16)
except:
i += 1
continue
if not laddr is None:
relations.add((laddr, lselector, addr))
if t[i+1].startswith(selector_s):
selector = int(t[i+1][len(selector_s):], 16)
i += 2
elif t[i+1].startswith(landingpad_s):
landingpad = int(t[i+1][len(landingpad_s):], 16)
relations.add((addr, -1, landingpad))
addr = landingpad
while not patch_helper.is_unreachable(patch_helper.block(addr).direct_branch):
addr = patch_helper.block(addr).direct_branch
if t[i+2].startswith(selector_s):
selector = int(t[i+2][len(selector_s):], 16)
i += 3
elif t[i+1].startswith("[Inferior "):
i += 1
else:
print("Warning: %x doesn't have selector. "%addr)
exit(0)
laddr = addr
lselector = selector
return list(relations)
print('************************flow******************************')
relations = parse_logs(sys.argv[3], prologue, patch_helper)
relations.sort(key = lambda x:x)
flow = {}
for bb, selector, child in relations:
if bb in flow:
while len(flow[bb]) < selector:
flow[bb].append(-1)
flow[bb].append(child)
assert(len(flow[bb]) == selector+1)
else:
flow[bb] = [child]
for (k, v) in list(flow.items()):
print('%#x:' % k, [hex(child) for child in v])
def parse_logs(logfn, prologue, patch_helper):
with open(logfn, "r") as f:
t = f.readlines()
i = 0
selector_s = "selector: "
landingpad_s = "landingPad: "
relations = set()
laddr = prologue
lselector = 0
landingpad = 0
while i < len(t):
try:
addr = int(t[i], 16)
except:
i += 1
continue
if not laddr is None:
relations.add((laddr, lselector, addr))
if t[i+1].startswith(selector_s):
selector = int(t[i+1][len(selector_s):], 16)
i += 2
elif t[i+1].startswith(landingpad_s):
landingpad = int(t[i+1][len(landingpad_s):], 16)
relations.add((addr, -1, landingpad))
addr = landingpad
while not patch_helper.is_unreachable(patch_helper.block(addr).direct_branch):
addr = patch_helper.block(addr).direct_branch
if t[i+2].startswith(selector_s):
selector = int(t[i+2][len(selector_s):], 16)
i += 3
elif t[i+1].startswith("[Inferior "):
i += 1
else:
print("Warning: %x doesn't have selector. "%addr)
exit(0)
laddr = addr
lselector = selector
return list(relations)
print('************************flow******************************')
relations = parse_logs(sys.argv[3], prologue, patch_helper)
relations.sort(key = lambda x:x)
flow = {}
for bb, selector, child in relations:
if bb in flow:
while len(flow[bb]) < selector:
flow[bb].append(-1)
flow[bb].append(child)
assert(len(flow[bb]) == selector+1)
else:
flow[bb] = [child]
for (k, v) in list(flow.items()):
print('%#x:' % k, [hex(child) for child in v])
************************flow******************************
0x404820: ['0x4075f9']
0x404ab8: ['0x404ab8', '0x406c94']
0x404bc4: ['0x407bc7']
0x404ca4: ['0x406bf9']
0x404ec5: ['0x4053d3']
0x404fae: ['0x406b00']
0x4051fe: ['0x40707d']
0x4053d3: ['0x406521']
0x405469: ['0x407d31']
0x4056f0: ['0x405a5f', '0x4056f0']
0x4057b8: ['0x404ab8']
0x405923: ['0x405923', '0x406e5d']
0x405a5f: ['0x4067bb']
0x405b29: ['0x406964', '0x406646']
0x405c87: ['0x405c87', '0x407437']
0x405f2a: ['0x405f2a', '0x4063b0']
0x4060e7: ['0x40723e']
0x40617c: ['0x409437']
0x40620f: ['0x405f2a']
0x406299: ['0x404bc4', '0x4057b8']
0x4063b0: ['0x4063b0', '0x405469']
0x4064a5: ['0x406704', '0x40620f']
0x406521: ['0x4074ca', '0x404bc4']
0x4065c9: ['0x40723e']
0x406646: ['0x406964']
0x406704: ['0x405c87']
0x4067bb: ['0x4082b6']
0x406964: ['0x405b29', '0x404ca4']
0x4069e3: ['0x408281']
0x406a72: ['0x404fae']
0x406b00: ['0x406299']
0x406bf9: ['0x405923']
0x406c94: ['0x4074ca']
0x406cfe: ['0x40723e']
0x406e5d: ['0x406e5d', '0x4077b6']
0x406f5f: ['0x406f5f', '0x407566']
0x40707d: ['0x40707d', '0x407960']
0x4070fa: ['0x406f5f']
0x4071aa: ['0x4056f0']
0x40723e: ['0x4072b4']
0x4072b4: ['0x4075f9', '0x4071aa']
0x407437: ['0x407437', '0x4064a5']
0x4074ca: ['0x404ec5', '0x407c6b']
0x407566: ['0x407566', '0x407a6b']
0x4075f9: ['0x4072b4', '-0x1', '0x4060e7', '0x406cfe', '0x4078e3', '0x4065c9']
0x4076bd: ['0x404ec5']
0x4077b6: ['0x406bf9', '0x4070fa']
0x4078e3: ['0x40723e']
0x407960: ['0x4081f5']
0x407a6b: ['0x4070fa', '0x406704']
0x407bc7: ['0x406a72', '0x407bc7']
0x407c6b: ['0x4069e3']
0x407d31: ['0x407d31', '0x407ebc']
0x407ebc: ['0x407ebc', '0x40617c']
0x4081f5: ['0x405b29']
0x408281: ['0x4051fe']
0x4082b6: ['0x4076bd']
************************flow******************************
0x404820: ['0x4075f9']
0x404ab8: ['0x404ab8', '0x406c94']
0x404bc4: ['0x407bc7']
0x404ca4: ['0x406bf9']
0x404ec5: ['0x4053d3']
0x404fae: ['0x406b00']
0x4051fe: ['0x40707d']
0x4053d3: ['0x406521']
0x405469: ['0x407d31']
0x4056f0: ['0x405a5f', '0x4056f0']
0x4057b8: ['0x404ab8']
0x405923: ['0x405923', '0x406e5d']
0x405a5f: ['0x4067bb']
0x405b29: ['0x406964', '0x406646']
0x405c87: ['0x405c87', '0x407437']
0x405f2a: ['0x405f2a', '0x4063b0']
0x4060e7: ['0x40723e']
0x40617c: ['0x409437']
0x40620f: ['0x405f2a']
0x406299: ['0x404bc4', '0x4057b8']
0x4063b0: ['0x4063b0', '0x405469']
0x4064a5: ['0x406704', '0x40620f']
0x406521: ['0x4074ca', '0x404bc4']
0x4065c9: ['0x40723e']
0x406646: ['0x406964']
0x406704: ['0x405c87']
0x4067bb: ['0x4082b6']
0x406964: ['0x405b29', '0x404ca4']
0x4069e3: ['0x408281']
0x406a72: ['0x404fae']
0x406b00: ['0x406299']
0x406bf9: ['0x405923']
0x406c94: ['0x4074ca']
0x406cfe: ['0x40723e']
0x406e5d: ['0x406e5d', '0x4077b6']
0x406f5f: ['0x406f5f', '0x407566']
0x40707d: ['0x40707d', '0x407960']
0x4070fa: ['0x406f5f']
0x4071aa: ['0x4056f0']
0x40723e: ['0x4072b4']
0x4072b4: ['0x4075f9', '0x4071aa']
0x407437: ['0x407437', '0x4064a5']
0x4074ca: ['0x404ec5', '0x407c6b']
0x407566: ['0x407566', '0x407a6b']
0x4075f9: ['0x4072b4', '-0x1', '0x4060e7', '0x406cfe', '0x4078e3', '0x4065c9']
0x4076bd: ['0x404ec5']
0x4077b6: ['0x406bf9', '0x4070fa']
0x4078e3: ['0x40723e']
0x407960: ['0x4081f5']
0x407a6b: ['0x4070fa', '0x406704']
0x407bc7: ['0x406a72', '0x407bc7']
0x407c6b: ['0x4069e3']
0x407d31: ['0x407d31', '0x407ebc']
0x407ebc: ['0x407ebc', '0x40617c']
0x4081f5: ['0x405b29']
0x408281: ['0x4051fe']
0x4082b6: ['0x4076bd']
def patch_branches(self, bb, va_targets):
va_start, size = self.get_patchable_from_relblk(bb)
if size < PatchHelper.JMP_SIZE:
print("[Warning] patch_jmp at block %x may fail. size: %d."%(bb.address, size))
org_start = va_start
print(f"va_start: {hex(va_start)}, bb addr: {hex(bb.address)}, size: {size}")
## `cmp esi, v` instr takes 3 bytes while `je xxx` takes 6 bytes
## And the last jmp instr takes 5 bytes.
total_size = 9 * len(va_targets) - 4
if size < total_size:
## If the nop block at the end of current block is not large enough,
## try to find another nop block and then jump to it.
nx_va_start, nx_size = self.get_nop_by_size(total_size)
if nx_size == 0:
print("[Error] `patch_branches` needs a nop block with size larger than %d."%(total_size))
self.patch_jmp(va_start, nx_va_start)
va_start, size = nx_va_start, nx_size
for i, t in enumerate(va_targets[:-1]):
cmp_instr = bytes([0x83,0xfe,i])
self.do_patch(va_start, cmp_instr)
va_start += len(cmp_instr)
cj_instr = bytes([PatchHelper.opcode['j'],PatchHelper.opcode['e']])
if t == -1:
## -1 represent that we do not know the flow for this selector value for now.
cj_instr += struct.pack('<i', self.func_terminate-va_start-6)
# cj_instr = asm(f"je {hex(self.func_terminate)}", vma=va_start)
else:
cj_instr += struct.pack('<i', t-va_start-6)
# cj_instr = asm(f"je {hex(t)}", vma=va_start)
self.do_patch(va_start, cj_instr)
va_start += len(cj_instr)
va_start += self.patch_jmp(va_start, va_targets[-1])
if va_start > org_start+size:
print("[Warning] patches at (%x, %x) overlaps next blk. "%(org_start, va_start))
def patch_branches(self, bb, va_targets):
va_start, size = self.get_patchable_from_relblk(bb)
if size < PatchHelper.JMP_SIZE:
print("[Warning] patch_jmp at block %x may fail. size: %d."%(bb.address, size))
org_start = va_start
print(f"va_start: {hex(va_start)}, bb addr: {hex(bb.address)}, size: {size}")
## `cmp esi, v` instr takes 3 bytes while `je xxx` takes 6 bytes
## And the last jmp instr takes 5 bytes.
total_size = 9 * len(va_targets) - 4
if size < total_size:
## If the nop block at the end of current block is not large enough,
## try to find another nop block and then jump to it.
nx_va_start, nx_size = self.get_nop_by_size(total_size)
if nx_size == 0:
print("[Error] `patch_branches` needs a nop block with size larger than %d."%(total_size))
self.patch_jmp(va_start, nx_va_start)
va_start, size = nx_va_start, nx_size
for i, t in enumerate(va_targets[:-1]):
cmp_instr = bytes([0x83,0xfe,i])
self.do_patch(va_start, cmp_instr)
va_start += len(cmp_instr)
cj_instr = bytes([PatchHelper.opcode['j'],PatchHelper.opcode['e']])
if t == -1:
## -1 represent that we do not know the flow for this selector value for now.
cj_instr += struct.pack('<i', self.func_terminate-va_start-6)
# cj_instr = asm(f"je {hex(self.func_terminate)}", vma=va_start)
else:
cj_instr += struct.pack('<i', t-va_start-6)
# cj_instr = asm(f"je {hex(t)}", vma=va_start)
self.do_patch(va_start, cj_instr)
va_start += len(cj_instr)
va_start += self.patch_jmp(va_start, va_targets[-1])
if va_start > org_start+size:
print("[Warning] patches at (%x, %x) overlaps next blk. "%(org_start, va_start))
## filename: deflat.pyfrom ast import Tuple
from xmlrpc.client import Boolean
from barf.barf import BARF
import angr
import struct
import sys
from pwnlib import elf
from queue import SimpleQueue
# from pwn import *class PatchHelper:
opcode = {'a' :0x87, 'ae':0x83, 'b' :0x82, 'be':0x86, 'c' :0x82, 'e' :0x84, 'z' :0x84, 'g' :0x8F,
'ge':0x8D, 'l' :0x8C, 'le':0x8E, 'na':0x86, 'nae':0x82,'nb':0x83, 'nbe':0x87,'nc':0x83,
'ne':0x85, 'ng':0x8E, 'nge':0x8C,'nl':0x8D, 'nle':0x8F,'no':0x81, 'np':0x8B, 'ns':0x89,
'nz':0x85, 'o' :0x80, 'p' :0x8A, 'pe':0x8A, 'po':0x8B, 's' :0x88, 'nop':0x90,'jmp':0xE9, 'j':0x0F}
JMP_SIZE = 5
def is_unreachable(self, bb):
if isinstance(bb, int):
bb = self.block(bb)
for i in range(len(bb.instrs)):
if bb.instrs[i].mnemonic != "call":
continue
target = bb.instrs[i].operands[0].immediate
if target == self.func_terminate:
return True
def block(self, addr):
bb = self.cfg.find_basic_block(addr)
if bb is None:
bb = barf.bb_builder.strategy._disassemble_bb(addr, barf.binary.ea_end, {})
return bb
@staticmethod
def is_imm(operand):
return (hasattr(operand, "_X86ImmediateOperand__key"))
@staticmethod
def is_reg(operand):
return (hasattr(operand, "_X86RegisterOperand__key"))
def is_call_throw(self, instr):
return instr.mnemonic == "call" and \
self.is_imm(instr.operands[0]) and\
instr.operands[0].immediate == self.func_throw
def is_call_allocate_exception(self, instr):
return instr.mnemonic == "call" and \
self.is_imm(instr.operands[0]) and\
instr.operands[0].immediate == self.func_allocate_exception
def is_call_obf_exception(self, instr):
return instr.mnemonic == "call" and \
self.is_imm(instr.operands[0]) and\
instr.operands[0].immediate == self.func_obf_exception
def skip_call_args(self, bb, i):
while ((bb.instrs[i].mnemonic in ["xor","mov","lea"]) and\
(len(bb.instrs[i].operands) > 0) and (self.is_reg(bb.instrs[i].operands[0])) and\
(bb.instrs[i].operands[0].name in ["edx", "rdx", "esi", "rsi", "edi", "rdi"])) or \
bb.instrs[i].mnemonic == "nop":
i -= 1
return i
def get_patchable_from_relblk(self, bb):
i = 0
end = bb.start_address + bb.size
while i < len(bb.instrs) and not self.is_call_throw(bb.instrs[i]):
i += 1
i = self.skip_call_args(bb, i-1)
if i == len(bb.instrs) - 1:
start = end
else:
start = bb.instrs[i+1].address
self.fill_nops(start, end)
return (start, end-start)
def __init__(self, proj, elf, barf, cfg) -> None:
self.p = proj
obj = proj.loader.main_object
self.func_terminate = obj.symbols_by_name["__clang_call_terminate"].rebased_addr
self.func_throw = obj.plt["__cxa_throw"]
self.func_allocate_exception = obj.plt["__cxa_allocate_exception"]
self.func_obf_exception = obj.symbols_by_name["_ZN18StdSubObfExceptionC2Ec"].rebased_addr
self.elf = elf
self.elfData = bytearray(self.elf.data)
self.barf = barf
self.cfg = cfg
self.nops = []
def append_nop(self, nopblk):
if nopblk[1] > 0:
self.nops.append(nopblk)
def finalize(self):
self.nops.sort()
idx = 0
while idx < len(self.nops) - 1:
if self.nops[idx][0] + self.nops[idx][1] != self.nops[idx+1][0]:
idx += 1
continue
self.nops[idx]=(self.nops[idx][0], self.nops[idx][1]+self.nops[idx+1][1])
del self.nops[idx+1]
def fill_nops(self, va_start, va_end):
assert not self.elf is None
start = self.elf.vaddr_to_offset(va_start)
end = self.elf.vaddr_to_offset(va_end)
for i in range(start, end):
self.elfData[i] = PatchHelper.opcode['nop']
def get_nop_by_size(self, min_size):
for idx, nop in enumerate(self.nops):
if nop[1] > min_size:
del self.nops[idx]
return nop
return (-1, 0)
def do_patch(self, va_start, codes):
start = self.elf.vaddr_to_offset(va_start)
for i in range(len(codes)):
self.elfData[start+i] = codes[i]
def patch_jmp(self, va_start, va_target):
offset = va_target - va_start - PatchHelper.JMP_SIZE
jmp = bytes([PatchHelper.opcode['jmp']])+struct.pack('<i', offset)
self.do_patch(va_start, jmp)
return PatchHelper.JMP_SIZE
def patch_branches(self, bb, va_targets):
va_start, size = self.get_patchable_from_relblk(bb)
if size < PatchHelper.JMP_SIZE:
print("[Warning] patch_jmp at block %x may fail. size: %d."%(bb.address, size))
org_start = va_start
print(f"va_start: {hex(va_start)}, bb addr: {hex(bb.address)}, size: {size}")
## `cmp esi, v` instr takes 3 bytes while `je xxx` takes 6 bytes
## And the last jmp instr takes 5 bytes.
total_size = (3+6) * len(va_targets) - 4
if size < total_size:
## If the nop block at the end of current block is not large enough,
## try to find another nop block and then jump to it.
nx_va_start, nx_size = self.get_nop_by_size(total_size)
if nx_size == 0:
print("\033[31m[Error]\033[0m `patch_branches` needs a nop block with size larger than %d."%(total_size))
self.patch_jmp(va_start, nx_va_start)
va_start, size = nx_va_start, nx_size
for i, t in enumerate(va_targets[:-1]):
cmp_instr = bytes([0x83,0xfe,i])
self.do_patch(va_start, cmp_instr)
va_start += len(cmp_instr)
cj_instr = bytes([PatchHelper.opcode['j'],PatchHelper.opcode['e']])
if t == -1:
## -1 represent that we do not know the flow for this selector value for now.
cj_instr += struct.pack('<i', self.func_terminate-va_start-6)
# cj_instr = asm(f"je {hex(self.func_terminate)}", vma=va_start)
else:
cj_instr += struct.pack('<i', t-va_start-6)
# cj_instr = asm(f"je {hex(t)}", vma=va_start)
self.do_patch(va_start, cj_instr)
va_start += len(cj_instr)
va_start += self.patch_jmp(va_start, va_targets[-1])
if va_start > org_start+size:
print("[Warning] patches at (%x, %x) overlaps next blk. "%(org_start, va_start))
def get_relevant_blocks(cfg, patch_helper, main_dispatcher):
isCmpRI = lambda instr: instr.mnemonic == "cmp" and\
hasattr(instr.operands[0], "_X86RegisterOperand__key") and\
hasattr(instr.operands[1], "_X86ImmediateOperand__key")
isCJmp = lambda instr: instr.mnemonic.startswith("j") and \
instr.mnemonic != "jmp"
isSubDispatcher = lambda bb: (len(bb.instrs) == 2) and\
isCmpRI(bb.instrs[0]) and isCJmp(bb.instrs[1])
relevant_blocks = []
visited = set()
q = SimpleQueue()
q.put(patch_helper.block(main_dispatcher))
while not q.empty():
bb = q.get()
if isSubDispatcher(bb):
patch_helper.append_nop((bb.start_address, bb.size))
for succ, cond in bb.branches:
if succ in visited:
continue
q.put(patch_helper.block(succ))
visited.add(succ)
else:
relevant_blocks.append(bb)
return relevant_blocks
def parse_logs(logfn, prologue, patch_helper):
with open(logfn, "r") as f:
t = f.readlines()
i = 0
selector_s = "selector: "
landingpad_s = "landingPad: "
relations = set()
laddr = prologue
lselector = 0
landingpad = 0
while i < len(t):
try:
addr = int(t[i], 16)
except:
i += 1
continue
if not laddr is None:
relations.add((laddr, lselector, addr))
if t[i+1].startswith(selector_s):
selector = int(t[i+1][len(selector_s):], 16)
i += 2
elif t[i+1].startswith(landingpad_s):
landingpad = int(t[i+1][len(landingpad_s):], 16)
relations.add((addr, -1, landingpad))
addr = landingpad
while not patch_helper.is_unreachable(patch_helper.block(addr).direct_branch):
addr = patch_helper.block(addr).direct_branch
if t[i+2].startswith(selector_s):
selector = int(t[i+2][len(selector_s):], 16)
i += 3
elif t[i+1].startswith("[Inferior "):
i += 1
else:
print("Warning: %x doesn't have selector. "%addr)
exit(0)
laddr = addr
lselector = selector
return list(relations)
def generate_gdb_script(relevant_blocks):
cmds = """\
set pagination offb *0x40A3D4commands silent
printf "landingPad: %x\n", $rdx
continue
endb _ZN18StdSubObfExceptionC2Eccommands silent
printf "selector: %x\n", $rsi
continue
end define mytrace break $arg0
commands
silent
printf "%x\\n", $pc
python gdb.execute('continue')
end
end""" for bb in relevant_blocks:
cmds += (f"mytrace *{hex(bb.address)} \n")
cmds += "run\n"
with open("test.gdb", "w") as f:
f.write(cmds)
if __name__ == '__main__':
if len(sys.argv) < 3:
print('Usage: python deflat.py filename function_address(hex) [logfile]')
exit(0)
# context.arch = "amd64"
# context.os = "linux"
# context.endian = "little"
filename = sys.argv[1]
start = int(sys.argv[2], 16)
origin = elf.ELF(filename)
b = angr.Project(filename, load_options={'auto_load_libs': False, 'main_opts':{'custom_base_addr': 0}})
barf = BARF(filename)
cfg = barf.recover_cfg(start=start)
patch_helper = PatchHelper(b, origin, barf, cfg)
blocks = cfg.basic_blocks
prologue = start
main_dispatcher = patch_helper.block(prologue).direct_branch
relevant_blocks = get_relevant_blocks(cfg, patch_helper, main_dispatcher)
nop = patch_helper.get_patchable_from_relblk(patch_helper.block(prologue))
patch_helper.append_nop(nop)
print('*******************relevant blocks************************')
print('main_dispatcher:%#x' % main_dispatcher)
print('relevant_blocks:', [hex(bb.address) for bb in relevant_blocks])
if len(sys.argv) < 4:
generate_gdb_script(relevant_blocks)
exit(0)
print('************************flow******************************')
relations = parse_logs(sys.argv[3], prologue, patch_helper)
relations.sort(key = lambda x:x)
flow = {}
for bb, selector, child in relations:
if bb in flow:
while len(flow[bb]) < selector:
flow[bb].append(-1)
flow[bb].append(child)
assert(len(flow[bb]) == selector+1)
else:
flow[bb] = [child]
for (k, v) in list(flow.items()):
print('%#x:' % k, [hex(child) for child in v])
print('************************patch*****************************')
patch_helper.finalize()
for (parent, childs) in list(flow.items()):
## Patch jmps
blk = patch_helper.block(parent)
patch_helper.patch_branches(blk, childs)
## Nop call allocate_exception and call obf_exception
for idx, instr in enumerate(blk.instrs):
if patch_helper.is_call_allocate_exception(instr) or\
patch_helper.is_call_obf_exception(instr):
# si = patch_helper.skip_call_args(blk, idx-1)+1
# start = blk.instrs[si].address
start = instr.address
end = instr.address + instr.size
patch_helper.fill_nops(start, end)
with open(filename + '.recovered', 'wb') as f:
f.write(bytes(patch_helper.elfData))
print('Successful! The recovered file: %s' % (filename + '.recovered'))
## filename: deflat.pyfrom ast import Tuple
from xmlrpc.client import Boolean
from barf.barf import BARF
import angr
import struct
import sys
from pwnlib import elf
from queue import SimpleQueue
# from pwn import *class PatchHelper:
opcode = {'a' :0x87, 'ae':0x83, 'b' :0x82, 'be':0x86, 'c' :0x82, 'e' :0x84, 'z' :0x84, 'g' :0x8F,
'ge':0x8D, 'l' :0x8C, 'le':0x8E, 'na':0x86, 'nae':0x82,'nb':0x83, 'nbe':0x87,'nc':0x83,
'ne':0x85, 'ng':0x8E, 'nge':0x8C,'nl':0x8D, 'nle':0x8F,'no':0x81, 'np':0x8B, 'ns':0x89,
'nz':0x85, 'o' :0x80, 'p' :0x8A, 'pe':0x8A, 'po':0x8B, 's' :0x88, 'nop':0x90,'jmp':0xE9, 'j':0x0F}
JMP_SIZE = 5
def is_unreachable(self, bb):
if isinstance(bb, int):
bb = self.block(bb)
for i in range(len(bb.instrs)):
if bb.instrs[i].mnemonic != "call":
continue
target = bb.instrs[i].operands[0].immediate
if target == self.func_terminate:
return True
def block(self, addr):
bb = self.cfg.find_basic_block(addr)
if bb is None:
bb = barf.bb_builder.strategy._disassemble_bb(addr, barf.binary.ea_end, {})
return bb
@staticmethod
def is_imm(operand):
return (hasattr(operand, "_X86ImmediateOperand__key"))
@staticmethod
def is_reg(operand):
return (hasattr(operand, "_X86RegisterOperand__key"))
def is_call_throw(self, instr):
return instr.mnemonic == "call" and \
self.is_imm(instr.operands[0]) and\
instr.operands[0].immediate == self.func_throw
def is_call_allocate_exception(self, instr):
return instr.mnemonic == "call" and \
self.is_imm(instr.operands[0]) and\
instr.operands[0].immediate == self.func_allocate_exception
def is_call_obf_exception(self, instr):
return instr.mnemonic == "call" and \
self.is_imm(instr.operands[0]) and\
instr.operands[0].immediate == self.func_obf_exception
def skip_call_args(self, bb, i):
while ((bb.instrs[i].mnemonic in ["xor","mov","lea"]) and\
(len(bb.instrs[i].operands) > 0) and (self.is_reg(bb.instrs[i].operands[0])) and\
(bb.instrs[i].operands[0].name in ["edx", "rdx", "esi", "rsi", "edi", "rdi"])) or \
bb.instrs[i].mnemonic == "nop":
i -= 1
return i
def get_patchable_from_relblk(self, bb):
i = 0
end = bb.start_address + bb.size
while i < len(bb.instrs) and not self.is_call_throw(bb.instrs[i]):
i += 1
i = self.skip_call_args(bb, i-1)
if i == len(bb.instrs) - 1:
start = end
else:
start = bb.instrs[i+1].address
self.fill_nops(start, end)
return (start, end-start)
def __init__(self, proj, elf, barf, cfg) -> None:
self.p = proj
obj = proj.loader.main_object
self.func_terminate = obj.symbols_by_name["__clang_call_terminate"].rebased_addr
self.func_throw = obj.plt["__cxa_throw"]
self.func_allocate_exception = obj.plt["__cxa_allocate_exception"]
self.func_obf_exception = obj.symbols_by_name["_ZN18StdSubObfExceptionC2Ec"].rebased_addr
self.elf = elf
self.elfData = bytearray(self.elf.data)
self.barf = barf
self.cfg = cfg
self.nops = []
def append_nop(self, nopblk):
if nopblk[1] > 0:
self.nops.append(nopblk)
def finalize(self):
self.nops.sort()
idx = 0
while idx < len(self.nops) - 1:
if self.nops[idx][0] + self.nops[idx][1] != self.nops[idx+1][0]:
idx += 1
continue
self.nops[idx]=(self.nops[idx][0], self.nops[idx][1]+self.nops[idx+1][1])
del self.nops[idx+1]
def fill_nops(self, va_start, va_end):
assert not self.elf is None
start = self.elf.vaddr_to_offset(va_start)
end = self.elf.vaddr_to_offset(va_end)
for i in range(start, end):
self.elfData[i] = PatchHelper.opcode['nop']
def get_nop_by_size(self, min_size):
for idx, nop in enumerate(self.nops):
if nop[1] > min_size:
del self.nops[idx]
return nop
return (-1, 0)
def do_patch(self, va_start, codes):
start = self.elf.vaddr_to_offset(va_start)
for i in range(len(codes)):
self.elfData[start+i] = codes[i]
def patch_jmp(self, va_start, va_target):
offset = va_target - va_start - PatchHelper.JMP_SIZE
jmp = bytes([PatchHelper.opcode['jmp']])+struct.pack('<i', offset)
self.do_patch(va_start, jmp)
return PatchHelper.JMP_SIZE
def patch_branches(self, bb, va_targets):
va_start, size = self.get_patchable_from_relblk(bb)
if size < PatchHelper.JMP_SIZE:
print("[Warning] patch_jmp at block %x may fail. size: %d."%(bb.address, size))
org_start = va_start
print(f"va_start: {hex(va_start)}, bb addr: {hex(bb.address)}, size: {size}")
## `cmp esi, v` instr takes 3 bytes while `je xxx` takes 6 bytes
## And the last jmp instr takes 5 bytes.
total_size = (3+6) * len(va_targets) - 4
if size < total_size:
## If the nop block at the end of current block is not large enough,
## try to find another nop block and then jump to it.
nx_va_start, nx_size = self.get_nop_by_size(total_size)
if nx_size == 0:
print("\033[31m[Error]\033[0m `patch_branches` needs a nop block with size larger than %d."%(total_size))
self.patch_jmp(va_start, nx_va_start)
va_start, size = nx_va_start, nx_size
for i, t in enumerate(va_targets[:-1]):
cmp_instr = bytes([0x83,0xfe,i])
self.do_patch(va_start, cmp_instr)
va_start += len(cmp_instr)
cj_instr = bytes([PatchHelper.opcode['j'],PatchHelper.opcode['e']])
if t == -1:
## -1 represent that we do not know the flow for this selector value for now.
cj_instr += struct.pack('<i', self.func_terminate-va_start-6)
# cj_instr = asm(f"je {hex(self.func_terminate)}", vma=va_start)
else:
cj_instr += struct.pack('<i', t-va_start-6)
# cj_instr = asm(f"je {hex(t)}", vma=va_start)
self.do_patch(va_start, cj_instr)
va_start += len(cj_instr)
va_start += self.patch_jmp(va_start, va_targets[-1])
if va_start > org_start+size:
print("[Warning] patches at (%x, %x) overlaps next blk. "%(org_start, va_start))
def get_relevant_blocks(cfg, patch_helper, main_dispatcher):
isCmpRI = lambda instr: instr.mnemonic == "cmp" and\
hasattr(instr.operands[0], "_X86RegisterOperand__key") and\
hasattr(instr.operands[1], "_X86ImmediateOperand__key")
isCJmp = lambda instr: instr.mnemonic.startswith("j") and \
instr.mnemonic != "jmp"
isSubDispatcher = lambda bb: (len(bb.instrs) == 2) and\
isCmpRI(bb.instrs[0]) and isCJmp(bb.instrs[1])
relevant_blocks = []
visited = set()
q = SimpleQueue()
q.put(patch_helper.block(main_dispatcher))
while not q.empty():
bb = q.get()
if isSubDispatcher(bb):
patch_helper.append_nop((bb.start_address, bb.size))
for succ, cond in bb.branches:
if succ in visited:
continue
q.put(patch_helper.block(succ))
visited.add(succ)
else:
relevant_blocks.append(bb)
return relevant_blocks
def parse_logs(logfn, prologue, patch_helper):
with open(logfn, "r") as f:
t = f.readlines()
i = 0
selector_s = "selector: "
landingpad_s = "landingPad: "
relations = set()
laddr = prologue
lselector = 0
landingpad = 0
while i < len(t):
try:
addr = int(t[i], 16)
except:
i += 1
continue
if not laddr is None:
relations.add((laddr, lselector, addr))
if t[i+1].startswith(selector_s):
selector = int(t[i+1][len(selector_s):], 16)
i += 2
elif t[i+1].startswith(landingpad_s):
landingpad = int(t[i+1][len(landingpad_s):], 16)
relations.add((addr, -1, landingpad))
addr = landingpad
while not patch_helper.is_unreachable(patch_helper.block(addr).direct_branch):
addr = patch_helper.block(addr).direct_branch
if t[i+2].startswith(selector_s):
selector = int(t[i+2][len(selector_s):], 16)
i += 3
elif t[i+1].startswith("[Inferior "):
i += 1
else:
print("Warning: %x doesn't have selector. "%addr)
exit(0)
laddr = addr
lselector = selector
return list(relations)
def generate_gdb_script(relevant_blocks):
cmds = """\
set pagination offb *0x40A3D4commands silent
printf "landingPad: %x\n", $rdx
continue
endb _ZN18StdSubObfExceptionC2Eccommands silent
printf "selector: %x\n", $rsi
continue
end define mytrace break $arg0
commands
silent
printf "%x\\n", $pc
python gdb.execute('continue')
end
end""" for bb in relevant_blocks:
cmds += (f"mytrace *{hex(bb.address)} \n")
cmds += "run\n"
with open("test.gdb", "w") as f:
f.write(cmds)
if __name__ == '__main__':
if len(sys.argv) < 3:
print('Usage: python deflat.py filename function_address(hex) [logfile]')
exit(0)
# context.arch = "amd64"
# context.os = "linux"
# context.endian = "little"
filename = sys.argv[1]
start = int(sys.argv[2], 16)
origin = elf.ELF(filename)
b = angr.Project(filename, load_options={'auto_load_libs': False, 'main_opts':{'custom_base_addr': 0}})
barf = BARF(filename)
cfg = barf.recover_cfg(start=start)
patch_helper = PatchHelper(b, origin, barf, cfg)
blocks = cfg.basic_blocks
prologue = start
main_dispatcher = patch_helper.block(prologue).direct_branch
relevant_blocks = get_relevant_blocks(cfg, patch_helper, main_dispatcher)
nop = patch_helper.get_patchable_from_relblk(patch_helper.block(prologue))
patch_helper.append_nop(nop)
[招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
最后于 2022-7-21 22:31
被P.Z编辑
，原因：
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我会一直研究的！ |
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已修正） |
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好文
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Mas0n 
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