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