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 <carlewis@gmail.com>
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')