86 lines
3.5 KiB
Python
86 lines
3.5 KiB
Python
from __future__ import annotations
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import json
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import typing
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from base64 import b64decode, b64encode
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import itsdangerous
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from itsdangerous.exc import BadSignature
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from starlette.datastructures import MutableHeaders, Secret
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from starlette.requests import HTTPConnection
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from starlette.types import ASGIApp, Message, Receive, Scope, Send
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class SessionMiddleware:
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def __init__(
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self,
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app: ASGIApp,
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secret_key: str | Secret,
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session_cookie: str = "session",
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max_age: int | None = 14 * 24 * 60 * 60, # 14 days, in seconds
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path: str = "/",
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same_site: typing.Literal["lax", "strict", "none"] = "lax",
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https_only: bool = False,
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domain: str | None = None,
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) -> None:
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self.app = app
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self.signer = itsdangerous.TimestampSigner(str(secret_key))
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self.session_cookie = session_cookie
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self.max_age = max_age
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self.path = path
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self.security_flags = "httponly; samesite=" + same_site
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if https_only: # Secure flag can be used with HTTPS only
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self.security_flags += "; secure"
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if domain is not None:
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self.security_flags += f"; domain={domain}"
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async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
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if scope["type"] not in ("http", "websocket"): # pragma: no cover
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await self.app(scope, receive, send)
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return
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connection = HTTPConnection(scope)
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initial_session_was_empty = True
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if self.session_cookie in connection.cookies:
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data = connection.cookies[self.session_cookie].encode("utf-8")
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try:
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data = self.signer.unsign(data, max_age=self.max_age)
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scope["session"] = json.loads(b64decode(data))
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initial_session_was_empty = False
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except BadSignature:
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scope["session"] = {}
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else:
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scope["session"] = {}
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async def send_wrapper(message: Message) -> None:
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if message["type"] == "http.response.start":
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if scope["session"]:
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# We have session data to persist.
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data = b64encode(json.dumps(scope["session"]).encode("utf-8"))
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data = self.signer.sign(data)
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headers = MutableHeaders(scope=message)
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header_value = "{session_cookie}={data}; path={path}; {max_age}{security_flags}".format( # noqa E501
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session_cookie=self.session_cookie,
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data=data.decode("utf-8"),
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path=self.path,
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max_age=f"Max-Age={self.max_age}; " if self.max_age else "",
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security_flags=self.security_flags,
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)
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headers.append("Set-Cookie", header_value)
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elif not initial_session_was_empty:
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# The session has been cleared.
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headers = MutableHeaders(scope=message)
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header_value = "{session_cookie}={data}; path={path}; {expires}{security_flags}".format( # noqa E501
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session_cookie=self.session_cookie,
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data="null",
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path=self.path,
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expires="expires=Thu, 01 Jan 1970 00:00:00 GMT; ",
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security_flags=self.security_flags,
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)
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headers.append("Set-Cookie", header_value)
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await send(message)
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await self.app(scope, receive, send_wrapper)
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