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#!/usr/bin/python3
from pwn import *
elf = context.binary = ELF("fastbin_dup")
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 & data.
# Returns chunk index.
def malloc(size, data):
global index
io.send("1")
io.sendafter("size: ", f"{size}")
io.sendafter("data: ", data)
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("> ")
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
io.timeout = 0.1
# =============================================================================
# =-=-=- EXAMPLE -=-=-=
# Set the username field.
username = "George"
io.sendafter("username: ", username)
io.recvuntil("> ")
# Request two 0x30-sized chunks and fill them with data.
chunk_A = malloc(0x28, "A"*0x28)
chunk_B = malloc(0x28, "B"*0x28)
# Free the first chunk, then the second.
free(chunk_A)
free(chunk_B)
# =============================================================================
io.interactive()
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