pypush-plus-plus/apns.py

from __future__ import annotations

import random
import socket
import threading
import time
from hashlib import sha1

import tlslite

import albert

COURIER_HOST = "windows.courier.push.apple.com"  # TODO: Get this from config
COURIER_PORT = 5223
ALPN = [b"apns-security-v2"]


# Connect to the courier server
def _connect(private_key: str, cert: str) -> tlslite.TLSConnection:
    # Connect to the courier server
    sock = socket.create_connection((COURIER_HOST, COURIER_PORT))
    # Wrap the socket in TLS
    sock = tlslite.TLSConnection(sock)
    # Parse the certificate and private key
    cert = tlslite.X509CertChain([tlslite.X509().parse(cert)])
    private_key = tlslite.parsePEMKey(private_key, private=True)
    # Handshake with the server
    sock.handshakeClientCert(cert, private_key, alpn=ALPN)

    return sock


class APNSConnection:
    incoming_queue = []

    def _queue_filler(self):
        while True and not self.sock.closed:
            # print(self.sock.closed)
            # print("QUEUE: Waiting for payload...")
            # self.sock.read(1)
            # print("QUEUE: Got payload?")
            payload = _deserialize_payload(self.sock)
            # print("QUEUE: Got payload?")

            if payload is not None:
                # print("QUEUE: Received payload: " + str(payload))
                self.incoming_queue.append(payload)
        # print("QUEUE: Thread ended")

    def _pop_by_id(self, id: int) -> tuple[int, list[tuple[int, bytes]]] | None:
        # print("QUEUE: Looking for id " + str(id) + " in " + str(self.incoming_queue))
        for i in range(len(self.incoming_queue)):
            if self.incoming_queue[i][0] == id:
                return self.incoming_queue.pop(i)
        return None

    def wait_for_packet(self, id: int) -> tuple[int, list[tuple[int, bytes]]]:
        payload = self._pop_by_id(id)
        while payload is None:
            payload = self._pop_by_id(id)
            time.sleep(0.1)
        return payload

    def __init__(self, private_key=None, cert=None):
        # Generate the private key and certificate if they're not provided
        if private_key is None or cert is None:
            self.private_key, self.cert = albert.generate_push_cert()
        else:
            self.private_key, self.cert = private_key, cert

        self.sock = _connect(self.private_key, self.cert)

        # Start the queue filler thread
        self.queue_filler_thread = threading.Thread(
            target=self._queue_filler, daemon=True
        )
        self.queue_filler_thread.start()

    def connect(self, root: bool = True, token: bytes = None):
        flags = 0b01000001
        if root:
            flags |= 0b0100

        if token is None:
            payload = _serialize_payload(
                7, [(2, 0x01.to_bytes()), (5, flags.to_bytes(4))]
            )
        else:
            payload = _serialize_payload(
                7, [(1, token), (2, 0x01.to_bytes()), (5, flags.to_bytes(4))]
            )

        self.sock.write(payload)

        payload = self.wait_for_packet(8)

        if (
            payload == None
            or payload[0] != 8
            or _get_field(payload[1], 1) != 0x00.to_bytes()
        ):
            raise Exception("Failed to connect")

        new_token = _get_field(payload[1], 3)
        if new_token is not None:
            self.token = new_token
        elif token is not None:
            self.token = token
        else:
            raise Exception("No token")

        return self.token

    def filter(self, topics: list[str]):
        fields = [(1, self.token)]

        for topic in topics:
            fields.append((2, sha1(topic.encode()).digest()))

        payload = _serialize_payload(9, fields)

        self.sock.write(payload)

    def send_message(self, topic: str, payload: str, id=None):
        if id is None:
            id = random.randbytes(4)

        payload = _serialize_payload(
            0x0A,
            [
                (4, id),
                (1, sha1(topic.encode()).digest()),
                (2, self.token),
                (3, payload),
            ],
        )

        self.sock.write(payload)

        payload = self.wait_for_packet(0x0B)

        if payload[1][0][1] != 0x00.to_bytes():
            raise Exception("Failed to send message")

    def set_state(self, state: int):
        self.sock.write(
            _serialize_payload(
                0x14, [(1, state.to_bytes(1)), (2, 0x7FFFFFFF.to_bytes(4))]
            )
        )

    def keep_alive(self):
        self.sock.write(_serialize_payload(0x0C, []))

    # TODO: Find a way to make this non-blocking
    # def expect_message(self) -> tuple[int, list[tuple[int, bytes]]] | None:
    #   return _deserialize_payload(self.sock)


def _serialize_field(id: int, value: bytes) -> bytes:
    return id.to_bytes() + len(value).to_bytes(2, "big") + value


def _serialize_payload(id: int, fields: list[(int, bytes)]) -> bytes:
    payload = b""

    for fid, value in fields:
        if fid is not None:
            payload += _serialize_field(fid, value)

    return id.to_bytes() + len(payload).to_bytes(4, "big") + payload


def _deserialize_field(stream: bytes) -> tuple[int, bytes]:
    id = int.from_bytes(stream[:1], "big")
    length = int.from_bytes(stream[1:3], "big")
    value = stream[3 : 3 + length]
    return id, value


# Note: Takes a stream, not a buffer, as we do not know the length of the payload
# WILL BLOCK IF THE STREAM IS EMPTY
def _deserialize_payload(stream) -> tuple[int, list[tuple[int, bytes]]] | None:
    id = int.from_bytes(stream.read(1), "big")

    if id == 0x0:
        return None

    length = int.from_bytes(stream.read(4), "big")

    buffer = stream.read(length)

    fields = []

    while len(buffer) > 0:
        fid, value = _deserialize_field(buffer)
        fields.append((fid, value))
        buffer = buffer[3 + len(value) :]

    return id, fields


def _deserialize_payload_from_buffer(
    buffer: bytes,
) -> tuple[int, list[tuple[int, bytes]]] | None:
    id = int.from_bytes(buffer[:1], "big")

    if id == 0x0:
        return None

    length = int.from_bytes(buffer[1:5], "big")

    buffer = buffer[5:]

    if len(buffer) < length:
        raise Exception("Buffer is too short")

    fields = []

    while len(buffer) > 0:
        fid, value = _deserialize_field(buffer)
        fields.append((fid, value))
        buffer = buffer[3 + len(value) :]

    return id, fields


# Returns the value of the first field with the given id
def _get_field(fields: list[tuple[int, bytes]], id: int) -> bytes:
    for field_id, value in fields:
        if field_id == id:
            return value
    return None