最近由前辈推荐，去到http://pwnable.kr/ 开始人生中第一次正经的刷题。 Toddler's Bottle.... :(
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://www.youtube.com/watch?v=blAxTfcW9VU
ssh fd@pwnable.kr -p2222 (pw:guest)
第一题fd主要是为了介绍玩法，源码如下
#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;
}
输入参数必须大于等于2，argv[0]指向程序运行的全路径名，之后从argv[1]开始即为实际传入的参数。
File descriptor 0为stdin，0x1234=4660。
构造输入：
fd@ubuntu:~$ ./fd 4660
LETMEWIN
good job :)
mommy! I think I know what a file descriptor is!!
