fd
hint
Mommy! what is a file descriptor in Linux?
* try to play the wargame your self but if you are ABSOLUTE beginner, follow this tutorial link:
https://youtu.be/971eZhMHQQw
ssh fd@pwnable.kr -p2222 (pw:guest)
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连上去后，查看根目录以及.c文件；
fd@pwnable:~$ ls -la
total 40
drwxr-x--- 5 root fd 4096 Oct 26 2016 .
drwxr-xr-x 116 root root 4096 Nov 11 14:52 ..
d--------- 2 root root 4096 Jun 12 2014 .bash_history
-r-sr-x--- 1 fd_pwn fd 7322 Jun 11 2014 fd
-rw-r--r-- 1 root root 418 Jun 11 2014 fd.c
-r--r----- 1 fd_pwn root 50 Jun 11 2014 flag
-rw------- 1 root root 128 Oct 26 2016 .gdb_history
dr-xr-xr-x 2 root root 4096 Dec 19 2016 .irssi
drwxr-xr-x 2 root root 4096 Oct 23 2016 .pwntools-cache
fd@pwnable:~$ cat fd.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char buf[32];
int main(int argc, char* argv[], char* envp[]){
if(argc<2){
printf("pass argv[1] a number\n");
return 0;
}
int fd = atoi( argv[1] ) - 0x1234;
int len = 0;
len = read(fd, buf, 32);
if(!strcmp("LETMEWIN\n", buf)){
printf("good job :)\n");
system("/bin/cat flag");
exit(0);
}
printf("learn about Linux file IO\n");
return 0;
}
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需要输入参数，使得read(fd, buf, 32)读取"LETMEWIN"到buf上，需要使fd=0，即fd=0x1234=4660
fd@pwnable:~$ ./fd 4660
LETMEWIN
good job :)
mommy! I think I know what a file descriptor is!!
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即可得到flag；
