All posts about #ctf



ROP Emporium - ret2csu

ret2csu, the final ROP Emporium challenge. This one is GLIBC-specific but nonetheless it is a fun exercise which forces you to look beyond the standard functions which the application author wrote and instead explore other parts of the binary which are essentially provided by the ecosystem.

Exploring the binary

Not …




ROP Emporium - pivot

The pivot challenge creates a situation where stack space is limited. This means that our full payload cannot be stored on the stack and instead must be located elsewhere in memory. However in order to start executing the code pointed to from the new stack we have to swap stacks …




ROP Emporium - fluff

Fluff was a challenge that is actually challenging, up to the point where you have a realisation and from there on it's fairly straightforward.

Exploring the binary

Nothing special going on still with this binary in terms of canaries or the likes:

[*] '/home/jasper/ropemporium/fluff/fluff'
    Arch:     amd64-64-little
    RELRO …



ROP Emporium - badchars

The previous challenge taught a very important pattern of "the mover" by performing chunked writes of arbitrary data into memory. This next challenge deals with a illegal or bad characters. Most everyone who has written exploits before has run into them at some point. Manually searching for which bytes are …




ROP Emporium - write4

With basic knowledge of how the GOT and PLT work and how function calls go through them along with a basic understanding of the amd64 ABI calling convention we can start looking for real gadgets now. In fact in this assignment we'll look at a really helpful way of loading …




ROP Emporium - callme

After familiarising ourselves with a simple buffer overflow in ret2win to overwrite the return address first, and then searching and using our first real gadget in split we will now focus on the Procedure Linkage Table (PLT). While here the functions that need to be called will all be using …




ROP Emporium - split

In the previous post I tried to explain what ROP is and how I solved the ROP Emporium ret2win. This write-up will be about the second challenge: split. We'll look at finding our first gadget and how to go about using it in a chain.

Exploring the binary

First explore …




ROP Emporium - ret2win

Over the past couple of week I've set myself the goal of learning how Return Oriented Programming (ROP) really works. Coincidentally, over at Hack the Box there have recently been multiple instances where one needed to exploit a binary using ROP. Whilst doing some research on the topic I ran …