60 lines
2.1 KiB
Python
60 lines
2.1 KiB
Python
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import typing
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from starlette.datastructures import URL, Headers
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from starlette.responses import PlainTextResponse, RedirectResponse, Response
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from starlette.types import ASGIApp, Receive, Scope, Send
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ENFORCE_DOMAIN_WILDCARD = "Domain wildcard patterns must be like '*.example.com'."
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class TrustedHostMiddleware:
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def __init__(
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self,
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app: ASGIApp,
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allowed_hosts: typing.Sequence[str] = None,
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www_redirect: bool = True,
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) -> None:
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if allowed_hosts is None:
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allowed_hosts = ["*"]
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for pattern in allowed_hosts:
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assert "*" not in pattern[1:], ENFORCE_DOMAIN_WILDCARD
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if pattern.startswith("*") and pattern != "*":
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assert pattern.startswith("*."), ENFORCE_DOMAIN_WILDCARD
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self.app = app
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self.allowed_hosts = list(allowed_hosts)
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self.allow_any = "*" in allowed_hosts
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self.www_redirect = www_redirect
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async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
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if self.allow_any or scope["type"] not in (
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"http",
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"websocket",
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): # pragma: no cover
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await self.app(scope, receive, send)
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return
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headers = Headers(scope=scope)
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host = headers.get("host", "").split(":")[0]
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is_valid_host = False
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found_www_redirect = False
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for pattern in self.allowed_hosts:
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if host == pattern or (
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pattern.startswith("*") and host.endswith(pattern[1:])
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):
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is_valid_host = True
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break
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elif "www." + host == pattern:
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found_www_redirect = True
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if is_valid_host:
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await self.app(scope, receive, send)
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else:
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if found_www_redirect and self.www_redirect:
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url = URL(scope=scope)
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redirect_url = url.replace(netloc="www." + url.netloc)
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response = RedirectResponse(url=str(redirect_url)) # type: Response
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else:
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response = PlainTextResponse("Invalid host header", status_code=400)
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await response(scope, receive, send)
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