open-source
文件
file: 8b6405c25fe447fa804c6833a0d72808.c
sha1: 23b35fa93a496385b904e1b74d487e589c436949
源码分析
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[]) {
if (argc != 4) {
printf("what?\n");
exit(1);
}
unsigned int first = atoi(argv[1]);
if (first != 0xcafe) {
printf("you are wrong, sorry.\n");
exit(2);
}
unsigned int second = atoi(argv[2]);
if (second % 5 == 3 || second % 17 != 8) {
printf("ha, you won't get it!\n");
exit(3);
}
if (strcmp("h4cky0u", argv[3])) {
printf("so close, dude!\n");
exit(4);
}
printf("Brr wrrr grr\n");
unsigned int hash = first * 31337 + (second % 17) * 11 + strlen(argv[3]) - 1615810207;
printf("Get your key: ");
printf("%x\n", hash);
return 0;
}
运行需要提供三个参数第一个是0xcafe，第二个需要满足second % 5 == 3 || second % 17 != 8，第三个是h4cky0u。即可得到key。
使用gcc编译运行输入三个参数得到结果：
> ./a.out 51966 25 h4cky0u
Brr wrrr grr
Get your key: c0ffee
我编译时报错，提示缺少头文件
stdlib.h，正确导入之后就可以编译成功了。
flag
c0ffee
