mirror of https://github.com/morpheus65535/bazarr
384 lines
14 KiB
Python
384 lines
14 KiB
Python
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# -*- coding: utf-8 -*-
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"""
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core
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~~~~
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Core functionality shared between the extension and the decorator.
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:copyright: (c) 2016 by Cory Dolphin.
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:license: MIT, see LICENSE for more details.
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"""
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import re
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import logging
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try:
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# on python 3
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from collections.abc import Iterable
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except ImportError:
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# on python 2.7 and pypy
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from collections import Iterable
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from datetime import timedelta
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from six import string_types
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from flask import request, current_app
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from werkzeug.datastructures import Headers, MultiDict
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LOG = logging.getLogger(__name__)
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# Response Headers
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ACL_ORIGIN = 'Access-Control-Allow-Origin'
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ACL_METHODS = 'Access-Control-Allow-Methods'
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ACL_ALLOW_HEADERS = 'Access-Control-Allow-Headers'
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ACL_EXPOSE_HEADERS = 'Access-Control-Expose-Headers'
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ACL_CREDENTIALS = 'Access-Control-Allow-Credentials'
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ACL_MAX_AGE = 'Access-Control-Max-Age'
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# Request Header
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ACL_REQUEST_METHOD = 'Access-Control-Request-Method'
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ACL_REQUEST_HEADERS = 'Access-Control-Request-Headers'
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ALL_METHODS = ['GET', 'HEAD', 'POST', 'OPTIONS', 'PUT', 'PATCH', 'DELETE']
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CONFIG_OPTIONS = ['CORS_ORIGINS', 'CORS_METHODS', 'CORS_ALLOW_HEADERS',
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'CORS_EXPOSE_HEADERS', 'CORS_SUPPORTS_CREDENTIALS',
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'CORS_MAX_AGE', 'CORS_SEND_WILDCARD',
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'CORS_AUTOMATIC_OPTIONS', 'CORS_VARY_HEADER',
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'CORS_RESOURCES', 'CORS_INTERCEPT_EXCEPTIONS',
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'CORS_ALWAYS_SEND']
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# Attribute added to request object by decorator to indicate that CORS
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# was evaluated, in case the decorator and extension are both applied
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# to a view.
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FLASK_CORS_EVALUATED = '_FLASK_CORS_EVALUATED'
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# Strange, but this gets the type of a compiled regex, which is otherwise not
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# exposed in a public API.
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RegexObject = type(re.compile(''))
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DEFAULT_OPTIONS = dict(origins='*',
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methods=ALL_METHODS,
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allow_headers='*',
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expose_headers=None,
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supports_credentials=False,
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max_age=None,
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send_wildcard=False,
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automatic_options=True,
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vary_header=True,
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resources=r'/*',
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intercept_exceptions=True,
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always_send=True)
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def parse_resources(resources):
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if isinstance(resources, dict):
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# To make the API more consistent with the decorator, allow a
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# resource of '*', which is not actually a valid regexp.
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resources = [(re_fix(k), v) for k, v in resources.items()]
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# Sort by regex length to provide consistency of matching and
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# to provide a proxy for specificity of match. E.G. longer
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# regular expressions are tried first.
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def pattern_length(pair):
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maybe_regex, _ = pair
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return len(get_regexp_pattern(maybe_regex))
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return sorted(resources,
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key=pattern_length,
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reverse=True)
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elif isinstance(resources, string_types):
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return [(re_fix(resources), {})]
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elif isinstance(resources, Iterable):
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return [(re_fix(r), {}) for r in resources]
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# Type of compiled regex is not part of the public API. Test for this
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# at runtime.
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elif isinstance(resources, RegexObject):
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return [(re_fix(resources), {})]
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else:
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raise ValueError("Unexpected value for resources argument.")
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def get_regexp_pattern(regexp):
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"""
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Helper that returns regexp pattern from given value.
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:param regexp: regular expression to stringify
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:type regexp: _sre.SRE_Pattern or str
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:returns: string representation of given regexp pattern
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:rtype: str
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"""
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try:
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return regexp.pattern
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except AttributeError:
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return str(regexp)
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def get_cors_origins(options, request_origin):
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origins = options.get('origins')
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wildcard = r'.*' in origins
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# If the Origin header is not present terminate this set of steps.
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# The request is outside the scope of this specification.-- W3Spec
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if request_origin:
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LOG.debug("CORS request received with 'Origin' %s", request_origin)
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# If the allowed origins is an asterisk or 'wildcard', always match
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if wildcard and options.get('send_wildcard'):
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LOG.debug("Allowed origins are set to '*'. Sending wildcard CORS header.")
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return ['*']
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# If the value of the Origin header is a case-sensitive match
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# for any of the values in list of origins
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elif try_match_any(request_origin, origins):
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LOG.debug("The request's Origin header matches. Sending CORS headers.", )
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# Add a single Access-Control-Allow-Origin header, with either
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# the value of the Origin header or the string "*" as value.
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# -- W3Spec
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return [request_origin]
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else:
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LOG.debug("The request's Origin header does not match any of allowed origins.")
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return None
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elif options.get('always_send'):
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if wildcard:
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# If wildcard is in the origins, even if 'send_wildcard' is False,
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# simply send the wildcard. Unless supports_credentials is True,
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# since that is forbidded by the spec..
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# It is the most-likely to be correct thing to do (the only other
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# option is to return nothing, which almost certainly not what
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# the developer wants if the '*' origin was specified.
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if options.get('supports_credentials'):
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return None
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else:
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return ['*']
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else:
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# Return all origins that are not regexes.
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return sorted([o for o in origins if not probably_regex(o)])
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# Terminate these steps, return the original request untouched.
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else:
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LOG.debug("The request did not contain an 'Origin' header. This means the browser or client did not request CORS, ensure the Origin Header is set.")
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return None
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def get_allow_headers(options, acl_request_headers):
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if acl_request_headers:
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request_headers = [h.strip() for h in acl_request_headers.split(',')]
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# any header that matches in the allow_headers
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matching_headers = filter(
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lambda h: try_match_any(h, options.get('allow_headers')),
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request_headers
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)
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return ', '.join(sorted(matching_headers))
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return None
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def get_cors_headers(options, request_headers, request_method):
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origins_to_set = get_cors_origins(options, request_headers.get('Origin'))
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headers = MultiDict()
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if not origins_to_set: # CORS is not enabled for this route
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return headers
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for origin in origins_to_set:
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headers.add(ACL_ORIGIN, origin)
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headers[ACL_EXPOSE_HEADERS] = options.get('expose_headers')
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if options.get('supports_credentials'):
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headers[ACL_CREDENTIALS] = 'true' # case sensative
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# This is a preflight request
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# http://www.w3.org/TR/cors/#resource-preflight-requests
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if request_method == 'OPTIONS':
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acl_request_method = request_headers.get(ACL_REQUEST_METHOD, '').upper()
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# If there is no Access-Control-Request-Method header or if parsing
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# failed, do not set any additional headers
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if acl_request_method and acl_request_method in options.get('methods'):
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# If method is not a case-sensitive match for any of the values in
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# list of methods do not set any additional headers and terminate
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# this set of steps.
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headers[ACL_ALLOW_HEADERS] = get_allow_headers(options, request_headers.get(ACL_REQUEST_HEADERS))
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headers[ACL_MAX_AGE] = options.get('max_age')
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headers[ACL_METHODS] = options.get('methods')
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else:
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LOG.info("The request's Access-Control-Request-Method header does not match allowed methods. CORS headers will not be applied.")
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# http://www.w3.org/TR/cors/#resource-implementation
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if options.get('vary_header'):
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# Only set header if the origin returned will vary dynamically,
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# i.e. if we are not returning an asterisk, and there are multiple
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# origins that can be matched.
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if headers[ACL_ORIGIN] == '*':
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pass
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elif (len(options.get('origins')) > 1 or
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len(origins_to_set) > 1 or
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any(map(probably_regex, options.get('origins')))):
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headers.add('Vary', 'Origin')
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return MultiDict((k, v) for k, v in headers.items() if v)
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def set_cors_headers(resp, options):
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"""
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Performs the actual evaluation of Flas-CORS options and actually
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modifies the response object.
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This function is used both in the decorator and the after_request
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callback
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"""
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# If CORS has already been evaluated via the decorator, skip
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if hasattr(resp, FLASK_CORS_EVALUATED):
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LOG.debug('CORS have been already evaluated, skipping')
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return resp
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# Some libraries, like OAuthlib, set resp.headers to non Multidict
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# objects (Werkzeug Headers work as well). This is a problem because
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# headers allow repeated values.
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if (not isinstance(resp.headers, Headers)
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and not isinstance(resp.headers, MultiDict)):
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resp.headers = MultiDict(resp.headers)
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headers_to_set = get_cors_headers(options, request.headers, request.method)
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LOG.debug('Settings CORS headers: %s', str(headers_to_set))
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for k, v in headers_to_set.items():
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resp.headers.add(k, v)
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return resp
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def probably_regex(maybe_regex):
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if isinstance(maybe_regex, RegexObject):
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return True
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else:
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common_regex_chars = ['*', '\\', ']', '?', '$', '^', '[', ']', '(', ')']
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# Use common characters used in regular expressions as a proxy
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# for if this string is in fact a regex.
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return any((c in maybe_regex for c in common_regex_chars))
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def re_fix(reg):
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"""
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Replace the invalid regex r'*' with the valid, wildcard regex r'/.*' to
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enable the CORS app extension to have a more user friendly api.
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"""
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return r'.*' if reg == r'*' else reg
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def try_match_any(inst, patterns):
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return any(try_match(inst, pattern) for pattern in patterns)
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def try_match(request_origin, maybe_regex):
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"""Safely attempts to match a pattern or string to a request origin."""
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if isinstance(maybe_regex, RegexObject):
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return re.match(maybe_regex, request_origin)
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elif probably_regex(maybe_regex):
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return re.match(maybe_regex, request_origin, flags=re.IGNORECASE)
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else:
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try:
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return request_origin.lower() == maybe_regex.lower()
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except AttributeError:
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return request_origin == maybe_regex
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def get_cors_options(appInstance, *dicts):
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"""
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Compute CORS options for an application by combining the DEFAULT_OPTIONS,
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the app's configuration-specified options and any dictionaries passed. The
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last specified option wins.
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"""
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options = DEFAULT_OPTIONS.copy()
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options.update(get_app_kwarg_dict(appInstance))
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if dicts:
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for d in dicts:
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options.update(d)
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return serialize_options(options)
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def get_app_kwarg_dict(appInstance=None):
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"""Returns the dictionary of CORS specific app configurations."""
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app = (appInstance or current_app)
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# In order to support blueprints which do not have a config attribute
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app_config = getattr(app, 'config', {})
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return {
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k.lower().replace('cors_', ''): app_config.get(k)
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for k in CONFIG_OPTIONS
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if app_config.get(k) is not None
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}
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def flexible_str(obj):
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"""
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A more flexible str function which intelligently handles stringifying
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strings, lists and other iterables. The results are lexographically sorted
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to ensure generated responses are consistent when iterables such as Set
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are used.
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"""
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if obj is None:
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return None
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elif(not isinstance(obj, string_types)
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and isinstance(obj, Iterable)):
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return ', '.join(str(item) for item in sorted(obj))
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else:
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return str(obj)
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def serialize_option(options_dict, key, upper=False):
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if key in options_dict:
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value = flexible_str(options_dict[key])
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options_dict[key] = value.upper() if upper else value
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def ensure_iterable(inst):
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"""
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Wraps scalars or string types as a list, or returns the iterable instance.
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"""
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if isinstance(inst, string_types):
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return [inst]
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elif not isinstance(inst, Iterable):
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return [inst]
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else:
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return inst
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def sanitize_regex_param(param):
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return [re_fix(x) for x in ensure_iterable(param)]
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def serialize_options(opts):
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"""
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A helper method to serialize and processes the options dictionary.
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"""
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options = (opts or {}).copy()
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for key in opts.keys():
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if key not in DEFAULT_OPTIONS:
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LOG.warning("Unknown option passed to Flask-CORS: %s", key)
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# Ensure origins is a list of allowed origins with at least one entry.
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options['origins'] = sanitize_regex_param(options.get('origins'))
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options['allow_headers'] = sanitize_regex_param(options.get('allow_headers'))
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# This is expressly forbidden by the spec. Raise a value error so people
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# don't get burned in production.
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if r'.*' in options['origins'] and options['supports_credentials'] and options['send_wildcard']:
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raise ValueError("Cannot use supports_credentials in conjunction with"
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"an origin string of '*'. See: "
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"http://www.w3.org/TR/cors/#resource-requests")
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serialize_option(options, 'expose_headers')
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serialize_option(options, 'methods', upper=True)
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if isinstance(options.get('max_age'), timedelta):
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options['max_age'] = str(int(options['max_age'].total_seconds()))
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return options
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