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#!/usr/bin/python
# urllib2 with kerberos proof of concept
# Copyright 2008 Lime Nest LLC
# Copyright 2008 Lime Spot LLC
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import re
import logging
import sys
import urllib2 as u2
import kerberos as k
log = logging.getLogger("http_kerberos_auth_handler")
class AbstractKerberosAuthHandler:
"""auth handler for urllib2 that does Kerberos HTTP Negotiate Authentication
"""
def negotiate_value(self, headers):
"""checks for "Negotiate" in proper auth header
"""
authreq = headers.get(self.auth_header, None)
log.debug('authreqs = %s', authreqs)
if authreq:
rx = re.compile('(?:.*,)*\s*Negotiate\s*([^,]*),?', re.I)
mo = rx.search(authreq)
if mo:
return mo.group(1)
else:
log.debug("regex failed on: %s", authreq)
else:
log.debug("%s header not found", self.auth_header)
return None
def __init__(self):
self.retried = 0
self.context = None
def generate_request_header(self, req, headers, neg_value):
self.retried += 1
log.debug("retry count: %d", self.retried)
host = req.get_host()
log.debug("req.get_host() returned %s", host)
domain = host.rsplit(':', 1)[0]
result, self.context = k.authGSSClientInit("HTTP@%s" % domain)
if result < 1:
log.warning("authGSSClientInit returned result %d", result)
return None
log.debug("authGSSClientInit() succeeded")
result = k.authGSSClientStep(self.context, neg_value)
if result < 0:
log.warning("authGSSClientStep returned result %d", result)
return None
log.debug("authGSSClientStep() succeeded")
response = k.authGSSClientResponse(self.context)
log.debug("authGSSClientResponse() succeeded")
return "Negotiate %s" % response
def authenticate_server(self, headers):
neg_value = self.negotiate_value(headers)
if neg_value is None:
log.critical("mutual auth failed. No negotiate header")
return None
result = k.authGSSClientStep(self.context, neg_value)
if result < 1:
# this is a critical security warning
# should change to a raise --Tim
log.critical("mutual auth failed: authGSSClientStep returned result %d", result)
pass
def clean_context(self):
if self.context is not None:
log.debug("cleaning context")
k.authGSSClientClean(self.context)
self.context = None
def http_error_auth_reqed(self, host, req, headers):
neg_value = self.negotiate_value(headers) #Check for auth_header
if neg_value is not None:
if not self.retried > 0:
return self.retry_http_kerberos_auth(req, headers, neg_value)
else:
return None
else:
self.retried = 0
def retry_http_kerberos_auth(self, req, headers, neg_value):
try:
neg_hdr = self.generate_request_header(req, headers, neg_value)
if neg_hdr is None:
log.debug("neg_hdr was None")
return None
req.add_unredirected_header(self.authz_header, neg_hdr)
resp = self.parent.open(req)
if resp.getcode() != 200:
self.authenticate_server(resp.info())
return resp
except k.GSSError, e:
self.clean_context()
self.retried = 0
log.critical("GSSAPI Error: %s/%s", e[0][0], e[1][0])
return None
self.clean_context()
self.retried = 0
class ProxyKerberosAuthHandler(u2.BaseHandler, AbstractKerberosAuthHandler):
"""Kerberos Negotiation handler for HTTP proxy auth
"""
authz_header = 'Proxy-Authorization'
auth_header = 'proxy-authenticate'
handler_order = 480 # before Digest auth
def http_error_407(self, req, fp, code, msg, headers):
log.debug("inside http_error_407")
host = req.get_host()
retry = self.http_error_auth_reqed(host, req, headers)
self.retried = 0
return retry
class HTTPKerberosAuthHandler(u2.BaseHandler, AbstractKerberosAuthHandler):
"""Kerberos Negotiation handler for HTTP auth
"""
authz_header = 'Authorization'
auth_header = 'www-authenticate'
handler_order = 480 # before Digest auth
def http_error_401(self, req, fp, code, msg, headers):
log.debug("inside http_error_401")
host = req.get_host()
retry = self.http_error_auth_reqed(host, req, headers)
self.retried = 0
return retry
def test():
logging.basicConfig(format='%(asctime)s %(levelname)s %(message)s',
level=logging.DEBUG)
log.info("starting test")
opener = u2.build_opener()
opener.add_handler(HTTPKerberosAuthHandler())
resp = opener.open(sys.argv[1])
print dir(resp), resp.info(), resp.code
if __name__ == '__main__':
test()
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