angr进阶(6)绕过反调试
作者:互联网
angr绕过反调试,一个是通过之前的方式,使用从特定位置开始测试的方法,还有一种通过hook进行反调试的方法。
其原理就在于angr能够符号化表示函数tumctf2016_zwiebe
p.hook_symbol('ptrace', angr.SIM_PROCEDURES['stubs']['ReturnUnconstrained'](return_value=0))
另外,对于代码自修改程序,需要使用如下的方式
p = angr.Project("zwiebe", support_selfmodifying_code=True)
另外,也可以hook到一些关键函数上,达到控制效果。
比如控制scanf就可以达到和控制返回值类似的效果。
1 flag_chars = [claripy.BVS('flag_%d' % i, 32) for i in range(13)] 2 class my_scanf(angr.SimProcedure): 3 def run(self, fmt, ptr): # pylint: disable=arguments-differ,unused-argument 4 self.state.mem[ptr].dword = flag_chars[self.state.globals['scanf_count']] 5 self.state.globals['scanf_count'] += 1 6 7 proj.hook_symbol('__isoc99_scanf', my_scanf(), replace=True) 8 9 sm = proj.factory.simulation_manager() 10 sm.one_active.options.add(angr.options.LAZY_SOLVES) 11 sm.one_active.globals['scanf_count'] = 0 12 13 # search for just before the printf("%c%c...") 14 # If we get to 0x402941, "Wrong" is going to be printed out, so definitely avoid that. 15 sm.explore(find=0x4028E9, avoid=0x402941) 16 17 # evaluate each of the flag chars against the constraints on the found state to construct the flag 18 flag = ''.join(chr(sm.one_found.solver.eval(c)) for c in flag_chars) 19 return flag
标签:进阶,hook,scanf,state,angr,flag,sm,调试 来源: https://www.cnblogs.com/61355ing/p/10525569.html