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#!/usr/bin/python3
from pwn import *
elf = context.binary = ELF("one_byte")
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.
# Returns chunk index.
def malloc():
global index
io.sendthen("> ", "1")
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 "edit" option; send index & data.
def edit(index, data):
io.send("3")
io.sendafter("index: ", f"{index}")
io.sendafter("data: ", data)
io.recvuntil("> ")
# Select the "read" option; read 0x58 bytes.
def read(index):
io.send("4")
io.sendafter("index: ", f"{index}")
r = io.recv(0x58)
io.recvuntil("> ")
return r
io = start()
io.recvuntil("> ")
io.timeout = 0.1
# =============================================================================
# =-=-=- EXAMPLE -=-=-=
# Request a chunk.
chunk_A = malloc()
# Edit chunk A.
edit(chunk_A, b"Y"*32)
# Read data from chunk A.
data = read(chunk_A)
log.info(f"Read from chunk_A:\n{data}")
# Free chunk A.
free(chunk_A)
# Because you haven't leaked a libc address yet, libc.sym.<symbol name>
# will only print a symbol's offset, rather than its actual address.
log.info(f"offset of puts() from start of GLIBC shared object: 0x{libc.sym.puts:02x}")
# Once you've leaked an address, e.g. the printf() function, use:
# libc.sym.address = <leaked printf address> - libc.sym.printf
# to correctly set your libc base address to its runtime address. Now future calls
# to libc.sym will use the symbol's actual address rather than its offset.
# =============================================================================
io.interactive()
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