def__init__(self,app:ASGIApp,allow_origins:typing.Sequence[str]=(),allow_methods:typing.Sequence[str]=("GET",),allow_headers:typing.Sequence[str]=(),allow_credentials:bool=False,allow_origin_regex:str|None=None,expose_headers:typing.Sequence[str]=(),max_age:int=600,)->None:if"*"inallow_methods:allow_methods=ALL_METHODScompiled_allow_origin_regex=Noneifallow_origin_regexisnotNone:compiled_allow_origin_regex=re.compile(allow_origin_regex)allow_all_origins="*"inallow_originsallow_all_headers="*"inallow_headerspreflight_explicit_allow_origin=notallow_all_originsorallow_credentialssimple_headers={}ifallow_all_origins:simple_headers["Access-Control-Allow-Origin"]="*"ifallow_credentials:simple_headers["Access-Control-Allow-Credentials"]="true"ifexpose_headers:simple_headers["Access-Control-Expose-Headers"]=", ".join(expose_headers)preflight_headers={}ifpreflight_explicit_allow_origin:# The origin value will be set in preflight_response() if it is allowed.preflight_headers["Vary"]="Origin"else:preflight_headers["Access-Control-Allow-Origin"]="*"preflight_headers.update({"Access-Control-Allow-Methods":", ".join(allow_methods),"Access-Control-Max-Age":str(max_age),})allow_headers=sorted(SAFELISTED_HEADERS|set(allow_headers))ifallow_headersandnotallow_all_headers:preflight_headers["Access-Control-Allow-Headers"]=", ".join(allow_headers)ifallow_credentials:preflight_headers["Access-Control-Allow-Credentials"]="true"self.app=appself.allow_origins=allow_originsself.allow_methods=allow_methodsself.allow_headers=[h.lower()forhinallow_headers]self.allow_all_origins=allow_all_originsself.allow_all_headers=allow_all_headersself.preflight_explicit_allow_origin=preflight_explicit_allow_originself.allow_origin_regex=compiled_allow_origin_regexself.simple_headers=simple_headersself.preflight_headers=preflight_headers
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")headers=dict(self.preflight_headers)failures=[]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")break# 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)
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)