Now I have a good mov gadget candidate at address 0x00052252
ropr is a blazing fast multithreaded ROP Gadget finder
ROP (Return Oriented Programming) Gadgets are small snippets of a few assembly instructions typically ending in a ret instruction which already exists as executable code within each binary or library. These gadgets may be used for binary exploitation and to subvert vulnerable executables.
When the addresses of many ROP Gadgets are written into a buffer we have formed an ROP Chain. If an attacker can move the stack pointer into this ROP Chain then control can be completely transferred to the attacker.
Most executables contain enough gadgets to write a turing-complete ROP Chain. For those that don’t, one can always use dynamic libraries contained in the same address-space such as libc once we know their addresses.
The beauty of using ROP Gadgets is that no new executable code needs to be written anywhere – an attacker may achieve their objective using only the code that already exists in the program.
Typically the first requirement to use ROP Gadgets is to have a place to write your ROP Chain – this can be any readable buffer. Simply write the addresses of each gadget you would like to use into this buffer. If the buffer is too small there may not be enough room to write a long ROP Chain into and so an attacker should be careful to craft their ROP Chain to be efficient enough to fit into the space available.
The next requirement is to be able to control the stack – This can take the form of a stack overflow – which allows the ROP Chain to be written directly under the stack pointer, or a “stack pivot” – which is usually a single gadget which moves the stack pointer to the rest of the ROP Chain.
Once the stack pointer is at the start of your ROP Chain, the next ret instruction will trigger the gadgets to be executed in sequence – each using the next as its return address on its own stack frame.
It is also possible to add function pointers into an ROP Chain – taking care that function arguments be supplied after the next element of the ROP Chain. This is typically combined with a “pop gadget”, which pops the arguments off the stack in order to smoothly transition to the next gadget after the function arguments.
cargo install ropr
the application will install to ~/.cargo/bin
git clone https://github.com/Ben-Lichtman/ropr cd ropr cargo build --release
the resulting binary will be located in target/release/ropr
git clone https://github.com/Ben-Lichtman/ropr cd ropr cargo install --path .
For example, if I was looking for a way to fill rax with a value from another register, I may choose to filter by the regex ^mov eax, …;:
Now I can add some filters to the command line for the highest quality results: