#IceCTF - Thor's a hacker now

I've spend over half an hour on solving this task, beside of that wasn't a hard one. But thanks to this exercise I had to learn using regular expressions in my text editor :) Text file connected to this task looked exactly like that (but was much larger):

00000000: 4c5a 4950 01b3 007f b61b edf0 8440 58e3  LZIP.........@X.
00000010: 91de 1027 5861 8a67 4282 46a4 92f9 4cad  ...'Xa.gB.F...L.
00000020: 2d5d 14eb 3099 2c31 01c2 d13a 74d2 c620  -]..0.,1...:t.. 
00000030: de27 3a8f fa92 0644 5468 2d02 01fa 24bb  .':....DTh-...$.
00000040: 719f a0fd a191 1678 8bff a2c4 2627 9871  q......x....&'.q
00000050: 83bf cff2 f8af 99fa c465 2b7c 6bdf ee3c  .........e+|k..<
00000060: b71b f61b 0b5e 0ce7 d14f f6a8 0466 6470  .....^...O...fdp
00000070: de67 02da 7be1 1abd e9f0 ac87 131a bcc0  .g..{...........
00000080: 0b0b 9f31 9400 48e3 616a 8f3f 4804 79ad  ...1..H.aj.?H.y.
00000090: a6bb 863a f641 01da b1ee c4fe b338 9289  ...:.A.......8..
000000a0: 2a90 8302 4170 773c 88d3 2641 d274 f533  *...Apw<..&A.t.3
000000b0: 84cf e7d9 f687 3b12 1516 970e 04c2 cfdd  ......;.........
000000c0: c1ca dc46 981d 2a7c 1b39 cb0b 4f8c 58cc  ...F..*|.9..O.X.
000000d0: 46b4 9744 4cb1 fbd3 c632 f36d ecbf 4789  F..DL....2.m..G.
000000e0: 00b8 d4fc 51a8 394e de2a 1a2d 3c43 179c  ....Q.9N.*.-<C..
000000f0: 9623 f971 2935 9564 9e15 c771 c3d5 d8b1  .#.q)5.d...q....
00000100: a7fa 3c0c f869 b829 f6d6 f145 6d57 b3a1  ..<..i.)...EmW..
00000110: bd3f 3fc2 a41f 7e35 089c de29 1d55 debf  .??...~5...).U..
00000120: 5400 c548 5c02 cd6c f853 e3e6 56b2 e395  T..H\..l.S..V...
00000130: 29d8 3985 d307 d46e 854c 4987 aab8 a5cb  ).9....n.LI.....
00000140: 2fea 6b20 6d24 34b3 a2a3 c8e4 247c 6681  /.k m$4.....$|f.

It's obviuos what we have to do to obtain the flag - we need to strip this text file from unnecessary things, and fill a new file with hex values. We can use any editor, which is capable of serving regular expressions, but I wrote some code in C to do that:

 

#include &ltstdio .h&gt
#include &ltiostream&gt
#include &ltfstream&gt

using namespace std;

int main(void)
{
 int procent = 0;

 ifstream plik;
 plik.open("ctf2.txt");

 ofstream plik2;
 plik2.open("output.txt");

 char *buf = new char[100];

 for (int i = 0; i < 21117; i++)
 {
  plik.getline(buf, 100);
  for (int j = 0; j < 68; j++)
  {
   if (j >= 10 && j <= 50 && buf[j] != ' ') 
   {
    plik2 << buf[j];
   }
  }
  if (i % 211 == 0) 
  {
   cout << "\r" << procent << "\% done!";
   procent ++;
  }
 }

 plik.close();
 plik2.close();
 
 delete [] buf;
 return 0;
}

ctf2.txt was the task's text file  ----> here,

and code to produce another C code from this raw bytes is downloadable here. Now we have raw hexadecimal which we have to put into file right now. I've used a code like that to do this:

#include &ltiostream&gt
#include &ltfstream&gt
using namespace std;
char tab[] = { /* here goes the tab with all hexes */ };

int main(void)
{
 ofstream plik;
 plik.open("binary.zip", ofstream::binary);
 for (int i = 0; i < sizeof(tab); i++) plik.put(tab[i]);
 plik.close();
 return 0;
}

Next thing to do is to unpack our new archive using lzip (just google this if u don't have one on your machine) and obtain an image with a flag. That's it!