File Checker - Internetwache CTF 2016

It checks if there is a file named .password in current directory.

Then, it reads the file contents and judge in the below function.

code: c

void fcn.0040079c(int64_t arg1, int64_t arg2)

{

(.. snip ..)

var_44h._4_4_ = 0x12ee;

var_3ch = 0x12e0;

var_38h = 0x12bc;

var_34h = 0x12f1;

var_30h = 0x12ee;

var_2ch = 0x12eb;

var_28h = 0x12f2;

var_24h = 0x12d8;

var_20h = 0x12f4;

var_1ch = 0x12ef;

var_18h = 0x12d2;

var_14h = 0x12f4;

var_10h = 0x12ec;

var_ch = 0x12d6;

var_8h = 0x12ba;

*(int32_t *)arg2 = (*(int32_t *)((int64_t)&var_44h + (int64_t)(int32_t)arg1 * 4 + 4) + *(int32_t *)arg2) % 0x1337;

return;

}

This function is used by main function, and return value(arg2) should be 0

arg1 is a character written in .password, so we can calculate the flag by subtracting each integer from 0x1337

In summary, The flag can be calculate by the following code.

code: python

IW{FILE_CHeCKa}