This problem is worth 275 pts, but I think it is easier than other red problems. XD
We can reverse it happily beacuse the programe wasn't stipped.
The problem is a game about transcation of 0days.
We can enter the password and cheat the game, but it's useless. XD
The game print the message:
Welcome to 0day Warz - The goal of the game is to get the $100M USD by the end of the game. You have been given a loan of $2000, with some high interest rate of 25% a day!`
The programe for the goal of game:
However, if understanding the game rule, we can know the condition is impossible to reach.
So we must find another vulunerbility.
In fact, there is a bof when
It cannot overflow to return address, but we can use it to change function pointers. :D
The programe use
It's create two garbage-collectors and put function pointer
string_free to gc.
Then, gc will trigger when we do
We can overwrite function ptr to
action_hiscore, and we can overwrite the return address.
Now, we can write the exploit.
Honestly, I am not familar with x64 architecture exploit....
I waste a lot of time to debug my code. :(
By the way, args on x64 is in register.
So we must find some gadget to control arguments at first.
Then, we can use
put() to leak arbitrary address.
There exist a little bug.... stdout dupped to socket.
We won't receive the content immediately.
To solve this bug, I return to
action_hiscore() again because it has
fflush() at the end of function.
After leak the address, we can calulate the address of
Next, We need a string of "/bin/sh".
Luckily, we can find it in libc, too. XD
So we can call
system("/bin/sh") to get the shell.
My partitial exploit: