b1301e606d
During SAML ECP authentication 2 specially formatted HTTP headers *MUST* be included in the request in order for the SP (Service Provider) to recognize the client is ECP capable and to start the SAML ECP flow. One is the PAOS header and the other is the Accept header which must include the "application/vnd.paos+xml" media type. Media types in the Accept header are separated by a comma (,). Unfortunately keystoneauth uses a semicolon (;) as the media type separator. The HTTP spec reserves the semicolon in the Accept header to attach parameters to the media type. For example Accept: type1;params1,type2;params2 Using a semicolon as a media type separator is syntactically invalid and can cause failures in servers that parse the Accept header. For example mod_auth_mellon emits this error message and fails to process the ECP request: request supplied valid PAOS header but omitted PAOS media type in Accept header have_paos_media_type=False valid_paos_header=True is_paos=False This indicates only 1 of the 2 required conditions were met. Change-Id: I6469990a57762fc47b297d7b5b2b4cb4872df4ba Signed-off-by: John Dennis <jdennis@redhat.com> Closes-Bug: 1656946
302 lines
11 KiB
Python
302 lines
11 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import abc
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try:
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from lxml import etree
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except ImportError:
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etree = None
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import requests
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import requests.auth
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from keystoneauth1 import access
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from keystoneauth1 import exceptions
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from keystoneauth1.identity import v3
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_PAOS_NAMESPACE = 'urn:liberty:paos:2003-08'
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_ECP_NAMESPACE = 'urn:oasis:names:tc:SAML:2.0:profiles:SSO:ecp'
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_PAOS_HEADER = 'application/vnd.paos+xml'
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_PAOS_VER = 'ver="%s";"%s"' % (_PAOS_NAMESPACE, _ECP_NAMESPACE)
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_XML_NAMESPACES = {
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'ecp': _ECP_NAMESPACE,
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'S': 'http://schemas.xmlsoap.org/soap/envelope/',
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'paos': _PAOS_NAMESPACE,
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}
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_XBASE = '/S:Envelope/S:Header/'
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_XPATH_SP_RELAY_STATE = '//ecp:RelayState'
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_XPATH_SP_CONSUMER_URL = _XBASE + 'paos:Request/@responseConsumerURL'
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_XPATH_IDP_CONSUMER_URL = _XBASE + 'ecp:Response/@AssertionConsumerServiceURL'
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_SOAP_FAULT = """
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<S:Envelope xmlns:S="http://schemas.xmlsoap.org/soap/envelope/">
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<S:Body>
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<S:Fault>
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<faultcode>S:Server</faultcode>
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<faultstring>responseConsumerURL from SP and
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assertionConsumerServiceURL from IdP do not match
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</faultstring>
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</S:Fault>
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</S:Body>
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</S:Envelope>
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"""
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class SamlException(Exception):
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"""Base SAML plugin exception."""
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class InvalidResponse(SamlException):
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"""Invalid Response from SAML authentication."""
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class ConsumerMismatch(SamlException):
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"""The SP and IDP consumers do not match."""
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def _response_xml(response, name):
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try:
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return etree.XML(response.content)
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except etree.XMLSyntaxError as e:
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msg = 'SAML2: Error parsing XML returned from %s: %s' % (name, e)
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raise InvalidResponse(msg)
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def _str_from_xml(xml, path):
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l = xml.xpath(path, namespaces=_XML_NAMESPACES)
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if len(l) != 1:
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raise IndexError('%s should provide a single element list' % path)
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return l[0]
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class _SamlAuth(requests.auth.AuthBase):
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"""A generic SAML ECP plugin for requests.
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This is a multi-step process including multiple HTTP requests.
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Authentication consists of:
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* HTTP GET request to the Service Provider.
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It's crucial to include HTTP headers indicating we are expecting SOAP
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message in return. Service Provider should respond with a SOAP
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message.
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* HTTP POST request to the external Identity Provider service with
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ECP extension enabled. The content sent is a header removed SOAP
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message returned from the Service Provider. It's also worth noting
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that ECP extension to the SAML2 doesn't define authentication method.
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The most popular is HttpBasicAuth with just user and password.
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Other possibilities could be X509 certificates or Kerberos.
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Upon successful authentication the user should receive a SAML2
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assertion.
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* HTTP POST request again to the Service Provider. The body of the
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request includes SAML2 assertion issued by a trusted Identity
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Provider. The request should be sent to the Service Provider
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consumer url specified in the SAML2 assertion.
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Providing the authentication was successful and both Service Provider
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and Identity Providers are trusted to each other, the Service
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Provider will issue an unscoped token with a list of groups the
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federated user is a member of.
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"""
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def __init__(self, identity_provider_url, requests_auth):
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super(_SamlAuth, self).__init__()
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self.identity_provider_url = identity_provider_url
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self.requests_auth = requests_auth
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def __call__(self, request):
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try:
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accept = request.headers['Accept']
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except KeyError:
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request.headers['Accept'] = _PAOS_HEADER
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else:
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request.headers['Accept'] = ','.join([accept, _PAOS_HEADER])
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request.headers['PAOS'] = _PAOS_VER
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request.register_hook('response', self._handle_response)
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return request
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def _handle_response(self, response, **kwargs):
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if (response.status_code == 200 and
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response.headers.get('Content-Type') == _PAOS_HEADER):
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response = self._ecp_retry(response, **kwargs)
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return response
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def _ecp_retry(self, sp_response, **kwargs):
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history = [sp_response]
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def send(*send_args, **send_kwargs):
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req = requests.Request(*send_args, **send_kwargs)
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return sp_response.connection.send(req.prepare(), **kwargs)
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authn_request = _response_xml(sp_response, 'Service Provider')
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relay_state = _str_from_xml(authn_request, _XPATH_SP_RELAY_STATE)
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sp_consumer_url = _str_from_xml(authn_request, _XPATH_SP_CONSUMER_URL)
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authn_request.remove(authn_request[0])
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idp_response = send('POST',
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self.identity_provider_url,
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headers={'Content-type': 'text/xml'},
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data=etree.tostring(authn_request),
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auth=self.requests_auth)
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history.append(idp_response)
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authn_response = _response_xml(idp_response, 'Identity Provider')
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idp_consumer_url = _str_from_xml(authn_response,
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_XPATH_IDP_CONSUMER_URL)
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if sp_consumer_url != idp_consumer_url:
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# send fault message to the SP, discard the response
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send('POST',
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sp_consumer_url,
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data=_SOAP_FAULT,
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headers={'Content-Type': _PAOS_HEADER})
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# prepare error message and raise an exception.
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msg = ('Consumer URLs from Service Provider %(service_provider)s '
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'%(sp_consumer_url)s and Identity Provider '
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'%(identity_provider)s %(idp_consumer_url)s are not equal')
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msg = msg % {
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'service_provider': sp_response.request.url,
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'sp_consumer_url': sp_consumer_url,
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'identity_provider': self.identity_provider_url,
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'idp_consumer_url': idp_consumer_url
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}
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raise ConsumerMismatch(msg)
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authn_response[0][0] = relay_state
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# idp_consumer_url is the URL on the SP that handles the ECP body
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# returned and creates an authenticated session.
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final_resp = send('POST',
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idp_consumer_url,
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headers={'Content-Type': _PAOS_HEADER},
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cookies=idp_response.cookies,
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data=etree.tostring(authn_response))
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history.append(final_resp)
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# the SP should then redirect us back to the original URL to retry the
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# original request.
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if final_resp.status_code in (requests.codes.found,
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requests.codes.other):
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# Consume content and release the original connection
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# to allow our new request to reuse the same one.
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sp_response.content
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sp_response.raw.release_conn()
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req = sp_response.request.copy()
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req.url = final_resp.headers['location']
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req.prepare_cookies(final_resp.cookies)
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final_resp = sp_response.connection.send(req, **kwargs)
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history.append(final_resp)
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final_resp.history.extend(history)
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return final_resp
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class _FederatedSaml(v3.FederationBaseAuth):
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def __init__(self, auth_url, identity_provider, protocol,
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identity_provider_url, **kwargs):
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super(_FederatedSaml, self).__init__(auth_url,
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identity_provider,
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protocol,
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**kwargs)
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self.identity_provider_url = identity_provider_url
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@abc.abstractmethod
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def get_requests_auth(self):
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raise NotImplementedError()
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def get_unscoped_auth_ref(self, session, **kwargs):
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method = self.get_requests_auth()
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auth = _SamlAuth(self.identity_provider_url, method)
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try:
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resp = session.get(self.federated_token_url,
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requests_auth=auth,
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authenticated=False)
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except SamlException as e:
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raise exceptions.AuthorizationFailure(str(e))
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return access.create(resp=resp)
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class Password(_FederatedSaml):
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r"""Implement authentication plugin for SAML2 protocol.
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ECP stands for `Enhanced Client or Proxy` and is a SAML2 extension
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for federated authentication where a transportation layer consists of
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HTTP protocol and XML SOAP messages.
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`Read for more information
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<https://wiki.shibboleth.net/confluence/display/CONCEPT/ECP>`_ on ECP.
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Reference the `SAML2 ECP specification <https://www.oasis-open.org/\
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committees/download.php/49979/saml-ecp-v2.0-wd09.pdf>`_.
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Currently only HTTPBasicAuth mechanism is available for the IdP
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authenication.
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:param auth_url: URL of the Identity Service
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:type auth_url: string
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:param identity_provider: name of the Identity Provider the client will
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authenticate against. This parameter will be used
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to build a dynamic URL used to obtain unscoped
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OpenStack token.
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:type identity_provider: string
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:param identity_provider_url: An Identity Provider URL, where the SAML2
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authn request will be sent.
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:type identity_provider_url: string
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:param username: User's login
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:type username: string
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:param password: User's password
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:type password: string
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:param protocol: Protocol to be used for the authentication.
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The name must be equal to one configured at the
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keystone sp side. This value is used for building
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dynamic authentication URL.
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Typical value would be: saml2
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:type protocol: string
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"""
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def __init__(self, auth_url, identity_provider, protocol,
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identity_provider_url, username, password, **kwargs):
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super(Password, self).__init__(auth_url,
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identity_provider,
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protocol,
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identity_provider_url,
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**kwargs)
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self.username = username
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self.password = password
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def get_requests_auth(self):
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return requests.auth.HTTPBasicAuth(self.username, self.password)
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