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"""
_handshake.py
websocket - WebSocket client library for Python
Copyright 2024 engn33r
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""
import hashlib
import hmac
import os
from base64 import encodebytes as base64encode
from http import HTTPStatus
from ._cookiejar import SimpleCookieJar
from ._exceptions import WebSocketException, WebSocketBadStatusException
from ._http import read_headers
from ._logging import dump, error
from ._socket import send
__all__ = ["handshake_response", "handshake", "SUPPORTED_REDIRECT_STATUSES"]
# websocket supported version.
VERSION = 13
SUPPORTED_REDIRECT_STATUSES = (
HTTPStatus.MOVED_PERMANENTLY,
HTTPStatus.FOUND,
HTTPStatus.SEE_OTHER,
HTTPStatus.TEMPORARY_REDIRECT,
HTTPStatus.PERMANENT_REDIRECT,
)
SUCCESS_STATUSES = SUPPORTED_REDIRECT_STATUSES + (HTTPStatus.SWITCHING_PROTOCOLS,)
CookieJar = SimpleCookieJar()
class handshake_response:
def __init__(self, status: int, headers: dict, subprotocol):
self.status = status
self.headers = headers
self.subprotocol = subprotocol
CookieJar.add(headers.get("set-cookie"))
def handshake(
sock, url: str, hostname: str, port: int, resource: str, **options
) -> handshake_response:
headers, key = _get_handshake_headers(resource, url, hostname, port, options)
header_str = "\r\n".join(headers)
send(sock, header_str)
dump("request header", header_str)
status, resp = _get_resp_headers(sock)
if status in SUPPORTED_REDIRECT_STATUSES:
return handshake_response(status, resp, None)
success, subproto = _validate(resp, key, options.get("subprotocols"))
if not success:
raise WebSocketException("Invalid WebSocket Header")
return handshake_response(status, resp, subproto)
def _pack_hostname(hostname: str) -> str:
# IPv6 address
if ":" in hostname:
return f"[{hostname}]"
return hostname
def _get_handshake_headers(
resource: str, url: str, host: str, port: int, options: dict
) -> tuple:
headers = [f"GET {resource} HTTP/1.1", "Upgrade: websocket"]
if port in [80, 443]:
hostport = _pack_hostname(host)
else:
hostport = f"{_pack_hostname(host)}:{port}"
if options.get("host"):
headers.append(f'Host: {options["host"]}')
else:
headers.append(f"Host: {hostport}")
# scheme indicates whether http or https is used in Origin
# The same approach is used in parse_url of _url.py to set default port
scheme, url = url.split(":", 1)
if not options.get("suppress_origin"):
if "origin" in options and options["origin"] is not None:
headers.append(f'Origin: {options["origin"]}')
elif scheme == "wss":
headers.append(f"Origin: https://{hostport}")
else:
headers.append(f"Origin: http://{hostport}")
key = _create_sec_websocket_key()
# Append Sec-WebSocket-Key & Sec-WebSocket-Version if not manually specified
if not options.get("header") or "Sec-WebSocket-Key" not in options["header"]:
headers.append(f"Sec-WebSocket-Key: {key}")
else:
key = options["header"]["Sec-WebSocket-Key"]
if not options.get("header") or "Sec-WebSocket-Version" not in options["header"]:
headers.append(f"Sec-WebSocket-Version: {VERSION}")
if not options.get("connection"):
headers.append("Connection: Upgrade")
else:
headers.append(options["connection"])
if subprotocols := options.get("subprotocols"):
headers.append(f'Sec-WebSocket-Protocol: {",".join(subprotocols)}')
if header := options.get("header"):
if isinstance(header, dict):
header = [": ".join([k, v]) for k, v in header.items() if v is not None]
headers.extend(header)
server_cookie = CookieJar.get(host)
client_cookie = options.get("cookie", None)
if cookie := "; ".join(filter(None, [server_cookie, client_cookie])):
headers.append(f"Cookie: {cookie}")
headers.extend(("", ""))
return headers, key
def _get_resp_headers(sock, success_statuses: tuple = SUCCESS_STATUSES) -> tuple:
status, resp_headers, status_message = read_headers(sock)
if status not in success_statuses:
content_len = resp_headers.get("content-length")
if content_len:
response_body = sock.recv(
int(content_len)
) # read the body of the HTTP error message response and include it in the exception
else:
response_body = None
raise WebSocketBadStatusException(
f"Handshake status {status} {status_message} -+-+- {resp_headers} -+-+- {response_body}",
status,
status_message,
resp_headers,
response_body,
)
return status, resp_headers
_HEADERS_TO_CHECK = {
"upgrade": "websocket",
"connection": "upgrade",
}
def _validate(headers, key: str, subprotocols) -> tuple:
subproto = None
for k, v in _HEADERS_TO_CHECK.items():
r = headers.get(k, None)
if not r:
return False, None
r = [x.strip().lower() for x in r.split(",")]
if v not in r:
return False, None
if subprotocols:
subproto = headers.get("sec-websocket-protocol", None)
if not subproto or subproto.lower() not in [s.lower() for s in subprotocols]:
error(f"Invalid subprotocol: {subprotocols}")
return False, None
subproto = subproto.lower()
result = headers.get("sec-websocket-accept", None)
if not result:
return False, None
result = result.lower()
if isinstance(result, str):
result = result.encode("utf-8")
value = f"{key}258EAFA5-E914-47DA-95CA-C5AB0DC85B11".encode("utf-8")
hashed = base64encode(hashlib.sha1(value).digest()).strip().lower()
if hmac.compare_digest(hashed, result):
return True, subproto
else:
return False, None
def _create_sec_websocket_key() -> str:
randomness = os.urandom(16)
return base64encode(randomness).decode("utf-8").strip()
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