Source code for cas

import datetime
import logging
from uuid import uuid4

import requests
from lxml import etree
from six.moves.urllib import parse as urllib_parse

logger = logging.getLogger(__name__)


[docs]class CASError(ValueError): pass
[docs]class SingleLogoutMixin(object):
[docs] @classmethod def get_saml_slos(cls, logout_request): """returns saml logout ticket info""" try: root = etree.fromstring(logout_request) return root.xpath( "//samlp:SessionIndex", namespaces={'samlp': "urn:oasis:names:tc:SAML:2.0:protocol"}) except etree.XMLSyntaxError: return None
[docs] @classmethod def verify_logout_request(cls, logout_request, ticket): """verifies the single logout request came from the CAS server returns True if the logout_request is valid, False otherwise """ try: session_index = cls.get_saml_slos(logout_request) session_index = session_index[0].text if session_index == ticket: return True else: return False except (AttributeError, IndexError): return False
[docs]class CASClient(object): def __new__(self, *args, **kwargs): version = kwargs.pop('version') if version in (1, '1'): return CASClientV1(*args, **kwargs) elif version in (2, '2'): return CASClientV2(*args, **kwargs) elif version in (3, '3'): return CASClientV3(*args, **kwargs) elif version == 'CAS_2_SAML_1_0': return CASClientWithSAMLV1(*args, **kwargs) raise ValueError('Unsupported CAS_VERSION %r' % version)
[docs]class CASClientBase(object): logout_redirect_param_name = 'service' def __init__(self, service_url=None, server_url=None, extra_login_params=None, renew=False, username_attribute=None, verify_ssl_certificate=True): self.service_url = service_url self.server_url = server_url self.extra_login_params = extra_login_params or {} self.renew = renew self.username_attribute = username_attribute self.verify_ssl_certificate = verify_ssl_certificate pass
[docs] def verify_ticket(self, ticket): """must return a triple""" raise NotImplementedError()
[docs] def get_login_url(self): """Generates CAS login URL""" params = {'service': self.service_url} if self.renew: params.update({'renew': 'true'}) params.update(self.extra_login_params) url = urllib_parse.urljoin(self.server_url, 'login') query = urllib_parse.urlencode(params) return url + '?' + query
[docs] def get_logout_url(self, redirect_url=None): """Generates CAS logout URL""" url = urllib_parse.urljoin(self.server_url, 'logout') if redirect_url: params = {self.logout_redirect_param_name: redirect_url} url += '?' + urllib_parse.urlencode(params) return url
[docs] def get_proxy_url(self, pgt): """Returns proxy url, given the proxy granting ticket""" params = urllib_parse.urlencode({'pgt': pgt, 'targetService': self.service_url}) return "%s/proxy?%s" % (self.server_url, params)
[docs] def get_proxy_ticket(self, pgt): """Returns proxy ticket given the proxy granting ticket""" response = requests.get(self.get_proxy_url(pgt), verify=self.verify_ssl_certificate) if response.status_code == 200: from lxml import etree root = etree.fromstring(response.content) tickets = root.xpath( "//cas:proxyTicket", namespaces={"cas": "http://www.yale.edu/tp/cas"} ) if len(tickets) == 1: return tickets[0].text errors = root.xpath( "//cas:authenticationFailure", namespaces={"cas": "http://www.yale.edu/tp/cas"} ) if len(errors) == 1: raise CASError(errors[0].attrib['code'], errors[0].text) raise CASError("Bad http code %s" % response.status_code)
[docs]class CASClientV1(CASClientBase): """CAS Client Version 1""" logout_redirect_param_name = 'url'
[docs] def verify_ticket(self, ticket): """Verifies CAS 1.0 authentication ticket. Returns username on success and None on failure. """ params = [('ticket', ticket), ('service', self.service_url)] url = (urllib_parse.urljoin(self.server_url, 'validate') + '?' + urllib_parse.urlencode(params)) page = requests.get( url, stream=True, verify=self.verify_ssl_certificate ) try: page_iterator = page.iter_lines(chunk_size=8192) verified = next(page_iterator).strip() if verified == 'yes': return next(page_iterator).strip(), None, None else: return None, None, None finally: page.close()
[docs]class CASClientV2(CASClientBase): """CAS Client Version 2""" url_suffix = 'serviceValidate' logout_redirect_param_name = 'url' def __init__(self, proxy_callback=None, *args, **kwargs): """proxy_callback is for V2 and V3 so V3 is subclass of V2""" self.proxy_callback = proxy_callback super(CASClientV2, self).__init__(*args, **kwargs)
[docs] def verify_ticket(self, ticket): """Verifies CAS 2.0+/3.0+ XML-based authentication ticket and returns extended attributes""" response = self.get_verification_response(ticket) return self.verify_response(response)
[docs] def get_verification_response(self, ticket): params = { 'ticket': ticket, 'service': self.service_url } if self.proxy_callback: params.update({'pgtUrl': self.proxy_callback}) base_url = urllib_parse.urljoin(self.server_url, self.url_suffix) page = requests.get( base_url, params=params, verify=self.verify_ssl_certificate ) try: return page.content finally: page.close()
[docs] @classmethod def parse_attributes_xml_element(cls, element): attributes = {} for attribute in element: tag = attribute.tag.split("}").pop() if tag in attributes: if isinstance(attributes[tag], list): attributes[tag].append(attribute.text) else: attributes[tag] = [attributes[tag]] attributes[tag].append(attribute.text) else: if tag == 'attraStyle': pass else: attributes[tag] = attribute.text return attributes
[docs] @classmethod def verify_response(cls, response): logger.debug('%s response - %s', cls.__name__, response) user, attributes, pgtiou = cls.parse_response_xml(response) if len(attributes) == 0: attributes = None return user, attributes, pgtiou
[docs] @classmethod def parse_response_xml(cls, response): try: from xml.etree import ElementTree except ImportError: from elementtree import ElementTree user = None attributes = {} pgtiou = None tree = ElementTree.fromstring(response) if tree[0].tag.endswith('authenticationSuccess'): """ Get namespace for looking for elements by tagname """ namespace = tree.tag[0:tree.tag.index('}')+1] user = tree[0].find('.//' + namespace + 'user').text for element in tree[0]: if element.tag.endswith('proxyGrantingTicket'): pgtiou = element.text elif element.tag.endswith('attributes') or element.tag.endswith('norEduPerson'): attributes = cls.parse_attributes_xml_element(element) return user, attributes, pgtiou
[docs]class CASClientV3(CASClientV2, SingleLogoutMixin): """CAS Client Version 3""" url_suffix = 'p3/serviceValidate' logout_redirect_param_name = 'service'
[docs] @classmethod def parse_attributes_xml_element(cls, element): attributes = {} for attribute in element: tag = attribute.tag.split("}").pop() if tag in attributes: if isinstance(attributes[tag], list): attributes[tag].append(attribute.text) else: attributes[tag] = [attributes[tag]] attributes[tag].append(attribute.text) else: attributes[tag] = attribute.text return attributes
[docs] @classmethod def verify_response(cls, response): logger.debug('%s response - %s', cls.__name__, response) return cls.parse_response_xml(response)
SAML_1_0_NS = 'urn:oasis:names:tc:SAML:1.0:' SAML_1_0_PROTOCOL_NS = '{' + SAML_1_0_NS + 'protocol' + '}' SAML_1_0_ASSERTION_NS = '{' + SAML_1_0_NS + 'assertion' + '}' SAML_ASSERTION_TEMPLATE = """<?xml version="1.0" encoding="UTF-8"?> <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"> <SOAP-ENV:Header/> <SOAP-ENV:Body> <samlp:Request xmlns:samlp="urn:oasis:names:tc:SAML:1.0:protocol" MajorVersion="1" MinorVersion="1" RequestID="{request_id}" IssueInstant="{timestamp}"> <samlp:AssertionArtifact>{ticket}</samlp:AssertionArtifact></samlp:Request> </SOAP-ENV:Body> </SOAP-ENV:Envelope>"""
[docs]class CASClientWithSAMLV1(CASClientV2, SingleLogoutMixin): """CASClient 3.0+ with SAML"""
[docs] def verify_ticket(self, ticket, **kwargs): """Verifies CAS 3.0+ XML-based authentication ticket and returns extended attributes. @date: 2011-11-30 @author: Carlos Gonzalez Vila <[email protected]> Returns username and attributes on success and None,None on failure. """ try: from xml.etree import ElementTree except ImportError: from elementtree import ElementTree page = self.fetch_saml_validation(ticket) try: user = None attributes = {} response = page.content tree = ElementTree.fromstring(response) # Find the authentication status success = tree.find('.//' + SAML_1_0_PROTOCOL_NS + 'StatusCode') if success is not None and success.attrib['Value'].endswith(':Success'): # User is validated name_identifier = tree.find('.//' + SAML_1_0_ASSERTION_NS + 'NameIdentifier') if name_identifier is not None: user = name_identifier.text attrs = tree.findall('.//' + SAML_1_0_ASSERTION_NS + 'Attribute') for at in attrs: if self.username_attribute in list(at.attrib.values()): user = at.find(SAML_1_0_ASSERTION_NS + 'AttributeValue').text attributes['uid'] = user values = at.findall(SAML_1_0_ASSERTION_NS + 'AttributeValue') if len(values) > 1: values_array = [] for v in values: values_array.append(v.text) attributes[at.attrib['AttributeName']] = values_array else: attributes[at.attrib['AttributeName']] = values[0].text return user, attributes, None finally: page.close()
[docs] def fetch_saml_validation(self, ticket): # We do the SAML validation headers = { 'soapaction': 'http://www.oasis-open.org/committees/security', 'cache-control': 'no-cache', 'pragma': 'no-cache', 'accept': 'text/xml', 'connection': 'keep-alive', 'content-type': 'text/xml; charset=utf-8', } params = {'TARGET': self.service_url} saml_validate_url = urllib_parse.urljoin( self.server_url, 'samlValidate', ) return requests.post( saml_validate_url, self.get_saml_assertion(ticket), params=params, headers=headers)
[docs] @classmethod def get_saml_assertion(cls, ticket): """ http://www.jasig.org/cas/protocol#samlvalidate-cas-3.0 SAML request values: RequestID [REQUIRED]: unique identifier for the request IssueInstant [REQUIRED]: timestamp of the request samlp:AssertionArtifact [REQUIRED]: the valid CAS Service Ticket obtained as a response parameter at login. """ # RequestID [REQUIRED] - unique identifier for the request request_id = uuid4() # e.g. 2014-06-02T09:21:03.071189 timestamp = datetime.datetime.now().isoformat() return SAML_ASSERTION_TEMPLATE.format( request_id=request_id, timestamp=timestamp, ticket=ticket, ).encode('utf8')