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defis_allowed_origin(self,origin:str)->bool:ifself.allow_all_origins:returnTrueifself.allow_origin_regexisnotNoneandself.allow_origin_regex.fullmatch(origin):returnTruereturnorigininself.allow_origins

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defpreflight_response(self,request_headers:Headers)->Response:requested_origin=request_headers["origin"]requested_method=request_headers["access-control-request-method"]requested_headers=request_headers.get("access-control-request-headers")requested_private_network=request_headers.get("access-control-request-private-network")headers=dict(self.preflight_headers)failures:list[str]=[]ifself.is_allowed_origin(origin=requested_origin):ifself.preflight_explicit_allow_origin:# The "else" case is already accounted for in self.preflight_headers# and the value would be "*".headers["Access-Control-Allow-Origin"]=requested_originelse:failures.append("origin")ifrequested_methodnotinself.allow_methods:failures.append("method")# If we allow all headers, then we have to mirror back any requested# headers in the response.ifself.allow_all_headersandrequested_headersisnotNone:headers["Access-Control-Allow-Headers"]=requested_headerselifrequested_headersisnotNone:forheaderin[h.lower()forhinrequested_headers.split(",")]:ifheader.strip()notinself.allow_headers:failures.append("headers")breakifrequested_private_networkisnotNone:ifself.allow_private_network:headers["Access-Control-Allow-Private-Network"]="true"else:failures.append("private-network")# We don't strictly need to use 400 responses here, since its up to# the browser to enforce the CORS policy, but its more informative# if we do.iffailures:failure_text="Disallowed CORS "+", ".join(failures)returnPlainTextResponse(failure_text,status_code=400,headers=headers)returnPlainTextResponse("OK",status_code=200,headers=headers)

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asyncdefsimple_response(self,scope:Scope,receive:Receive,send:Send,request_headers:Headers)->None:send=functools.partial(self.send,send=send,request_headers=request_headers)awaitself.app(scope,receive,send)

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asyncdefsend(self,message:Message,send:Send,request_headers:Headers)->None:ifmessage["type"]!="http.response.start":awaitsend(message)returnmessage.setdefault("headers",[])headers=MutableHeaders(scope=message)headers.update(self.simple_headers)origin=request_headers["Origin"]has_cookie="cookie"inrequest_headers# If request includes any cookie headers, then we must respond# with the specific origin instead of '*'.ifself.allow_all_originsandhas_cookie:self.allow_explicit_origin(headers,origin)# If we only allow specific origins, then we have to mirror back# the Origin header in the response.elifnotself.allow_all_originsandself.is_allowed_origin(origin=origin):self.allow_explicit_origin(headers,origin)awaitsend(message)

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@staticmethoddefallow_explicit_origin(headers:MutableHeaders,origin:str)->None:headers["Access-Control-Allow-Origin"]=originheaders.add_vary_header("Origin")