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#!/usr/bin/python3
from pwn import *
elf = context.binary = ELF("malloc_testbed")
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.
# Return chunk index.
def malloc(size):
global index
io.send("1")
io.sendafter("size: ", f"{size}")
io.recvuntil("> ")
index += 1
return index - 1
# Select the "free" option; send index.
def free(index):
io.send("2")
io.sendafter("index: ", f"{index}")
io.recvuntil("> ")
# Select the "free address" option; send address.
def free_address(address):
io.send("3")
io.sendafter("address: ", f"{address}")
io.recvuntil("> ")
# Select the "edit" option; send index & data.
def edit(index, data):
io.send("4")
io.sendafter("index: ", f"{index}")
io.sendafter("data: ", data)
io.recvuntil("> ")
# Select the "read" option; send index.
# Return data from read operation.
def read(index):
io.send("5")
io.sendafter("index: ", f"{index}")
r = io.recvuntil("\n1) malloc", drop=True)
io.recvuntil("> ")
return r
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)
# This binary leaks the address of its m_array.
io.recvuntil("m_array @ ")
m_array = int(io.recvline(), 16)
io.recvuntil("> ")
io.timeout = 0.1
# =============================================================================
# =-=-=- EXAMPLE -=-=-=
# Log some useful addresses.
log.info(f"libc is at 0x{libc.address:02x}")
log.info(f"heap is at 0x{heap:02x}")
log.info(f"m_array is at 0x{m_array:02x}")
# Request 2 chunks.
chunk_A = malloc(0x88)
chunk_B = malloc(0x18)
# Free "chunk_A".
free(chunk_A)
# Edit "chunk_B".
edit(chunk_B, "Y"*8)
# Read data from the "chunk_B".
log.info(f"reading chunk_B: {read(chunk_B)[:8]}")
# =============================================================================
io.interactive()
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