Bitsctf 2017 writeup

Bitsctf 2017 writeup.md

pwn1

• pwn1 is really basic problem about buffer overflow.
• When we excute program, they just print buffer address to us to calculate address easier.
• Buffer size is only 0x10 so I'll write shellcode after ret
• This simple python script will help you to pwning it.

third

• This problem is not hard too. Only difficulty is that I couldn't see library function name.
• I make my own function table too make reversing more easily

0x7f8: srand
0x7f0: rand
0x7d8: printf
0x810: scarf
0x818: exit
0x808: fopen
0x7e8: read
0x7e0: fclose

• But function name maybe different with real.
• I made some c program that create same number with third program.
• This simple python script will give you flag

mission-impropable

• This file type is Intel hex type file. I heard about it at this time. I recommand you to read this blog if you are korean.
• I tried to recover it to bin but I failed to do it correctly. So I use linux strings command to my imperfect program.
• flag: BITCTF{B4d_bad_U5B}

Riskv and Reword

• It was too hard to me to guess solution. I refer this blog

Sherlock

• If you see that ebook carefully you can see some strange things. letter I isn't capital in that book and some letter is capital even if that's middle in word.
• If you collect capital letter than you can get strings like ZEROONEZEROZERO... than change it to real number like 0100...
• Now change it to ascii letter than we can get flag
• flag: BITSCTF{h1d3_1n_pl41n_5173}