identify_string_decoders.py 文件源码

def find_unusual_xors(functions):
    # TODO find xors in tight loops
    candidate_functions = []
    for fva in functions:
        cva = fva
        while cva != idaapi.BADADDR and cva < idc.FindFuncEnd(fva):
            if idc.GetMnem(cva) == "xor":
                if idc.GetOpnd(cva, 0) != idc.GetOpnd(cva, 1):
                    g_logger.debug("suspicious XOR instruction at 0x%08X in function 0x%08X: %s", cva, fva,
                                   idc.GetDisasm(cva))
                    ph = idc.PrevHead(cva)
                    nh = idc.NextHead(cva)
                    ip = idc.GetDisasm(ph)
                    ia = idc.GetDisasm(nh)
                    if ip and ia:
                        g_logger.debug("Instructions: %s;  %s;  %s", ip, idc.GetDisasm(cva), ia)
                    if ph or nh:
                        if is_security_cookie(cva, ph, nh):
                            g_logger.debug("XOR related to security cookie: %s", idc.GetDisasm(cva))
                        else:
                            g_logger.debug("unusual XOR: %s", idc.GetDisasm(cva))
                            candidate_functions.append(fva)
                            break
            cva = idc.NextHead(cva)
    return candidate_functions