/usr/lib/python3/dist-packages/requests_kerberos/kerberos_.py is in python3-requests-kerberos 0.11.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import kerberos
except ImportError:
import winkerberos as kerberos
import re
import logging
from requests.auth import AuthBase
from requests.models import Response
from requests.compat import urlparse, StringIO
from requests.structures import CaseInsensitiveDict
from requests.cookies import cookiejar_from_dict
from .exceptions import MutualAuthenticationError, KerberosExchangeError
log = logging.getLogger(__name__)
# Different types of mutual authentication:
# with mutual_authentication set to REQUIRED, all responses will be
# authenticated with the exception of errors. Errors will have their contents
# and headers stripped. If a non-error response cannot be authenticated, a
# MutualAuthenticationError exception will be raised.
# with mutual_authentication set to OPTIONAL, mutual authentication will be
# attempted if supported, and if supported and failed, a
# MutualAuthenticationError exception will be raised. Responses which do not
# support mutual authentication will be returned directly to the user.
# with mutual_authentication set to DISABLED, mutual authentication will not be
# attempted, even if supported.
REQUIRED = 1
OPTIONAL = 2
DISABLED = 3
class SanitizedResponse(Response):
"""The :class:`Response <Response>` object, which contains a server's
response to an HTTP request.
This differs from `requests.models.Response` in that it's headers and
content have been sanitized. This is only used for HTTP Error messages
which do not support mutual authentication when mutual authentication is
required."""
def __init__(self, response):
super(SanitizedResponse, self).__init__()
self.status_code = response.status_code
self.encoding = response.encoding
self.raw = response.raw
self.reason = response.reason
self.url = response.url
self.request = response.request
self.connection = response.connection
self._content_consumed = True
self._content = ""
self.cookies = cookiejar_from_dict({})
self.headers = CaseInsensitiveDict()
self.headers['content-length'] = '0'
for header in ('date', 'server'):
if header in response.headers:
self.headers[header] = response.headers[header]
def _negotiate_value(response):
"""Extracts the gssapi authentication token from the appropriate header"""
if hasattr(_negotiate_value, 'regex'):
regex = _negotiate_value.regex
else:
# There's no need to re-compile this EVERY time it is called. Compile
# it once and you won't have the performance hit of the compilation.
regex = re.compile('(?:.*,)*\s*Negotiate\s*([^,]*),?', re.I)
_negotiate_value.regex = regex
authreq = response.headers.get('www-authenticate', None)
if authreq:
match_obj = regex.search(authreq)
if match_obj:
return match_obj.group(1)
return None
class HTTPKerberosAuth(AuthBase):
"""Attaches HTTP GSSAPI/Kerberos Authentication to the given Request
object."""
def __init__(
self, mutual_authentication=REQUIRED,
service="HTTP", delegate=False, force_preemptive=False,
principal=None, hostname_override=None, sanitize_mutual_error_response=True):
self.context = {}
self.mutual_authentication = mutual_authentication
self.delegate = delegate
self.pos = None
self.service = service
self.force_preemptive = force_preemptive
self.principal = principal
self.hostname_override = hostname_override
self.sanitize_mutual_error_response = sanitize_mutual_error_response
def generate_request_header(self, response, host, is_preemptive=False):
"""
Generates the GSSAPI authentication token with kerberos.
If any GSSAPI step fails, raise KerberosExchangeError
with failure detail.
"""
# Flags used by kerberos module.
gssflags = kerberos.GSS_C_MUTUAL_FLAG | kerberos.GSS_C_SEQUENCE_FLAG
if self.delegate:
gssflags |= kerberos.GSS_C_DELEG_FLAG
try:
kerb_stage = "authGSSClientInit()"
# contexts still need to be stored by host, but hostname_override
# allows use of an arbitrary hostname for the kerberos exchange
# (eg, in cases of aliased hosts, internal vs external, CNAMEs
# w/ name-based HTTP hosting)
kerb_host = self.hostname_override if self.hostname_override is not None else host
kerb_spn = "{0}@{1}".format(self.service, kerb_host)
result, self.context[host] = kerberos.authGSSClientInit(kerb_spn,
gssflags=gssflags, principal=self.principal)
if result < 1:
raise EnvironmentError(result, kerb_stage)
# if we have a previous response from the server, use it to continue
# the auth process, otherwise use an empty value
negotiate_resp_value = '' if is_preemptive else _negotiate_value(response)
kerb_stage = "authGSSClientStep()"
result = kerberos.authGSSClientStep(self.context[host],
negotiate_resp_value)
if result < 0:
raise EnvironmentError(result, kerb_stage)
kerb_stage = "authGSSClientResponse()"
gss_response = kerberos.authGSSClientResponse(self.context[host])
return "Negotiate {0}".format(gss_response)
except kerberos.GSSError as error:
log.exception(
"generate_request_header(): {0} failed:".format(kerb_stage))
log.exception(error)
raise KerberosExchangeError("%s failed: %s" % (kerb_stage, str(error.args)))
except EnvironmentError as error:
# ensure we raised this for translation to KerberosExchangeError
# by comparing errno to result, re-raise if not
if error.errno != result:
raise
message = "{0} failed, result: {1}".format(kerb_stage, result)
log.error("generate_request_header(): {0}".format(message))
raise KerberosExchangeError(message)
def authenticate_user(self, response, **kwargs):
"""Handles user authentication with gssapi/kerberos"""
host = urlparse(response.url).hostname
try:
auth_header = self.generate_request_header(response, host)
except KerberosExchangeError:
# GSS Failure, return existing response
return response
log.debug("authenticate_user(): Authorization header: {0}".format(
auth_header))
response.request.headers['Authorization'] = auth_header
# Consume the content so we can reuse the connection for the next
# request.
response.content
response.raw.release_conn()
_r = response.connection.send(response.request, **kwargs)
_r.history.append(response)
log.debug("authenticate_user(): returning {0}".format(_r))
return _r
def handle_401(self, response, **kwargs):
"""Handles 401's, attempts to use gssapi/kerberos authentication"""
log.debug("handle_401(): Handling: 401")
if _negotiate_value(response) is not None:
_r = self.authenticate_user(response, **kwargs)
log.debug("handle_401(): returning {0}".format(_r))
return _r
else:
log.debug("handle_401(): Kerberos is not supported")
log.debug("handle_401(): returning {0}".format(response))
return response
def handle_other(self, response):
"""Handles all responses with the exception of 401s.
This is necessary so that we can authenticate responses if requested"""
log.debug("handle_other(): Handling: %d" % response.status_code)
if self.mutual_authentication in (REQUIRED, OPTIONAL):
is_http_error = response.status_code >= 400
if _negotiate_value(response) is not None:
log.debug("handle_other(): Authenticating the server")
if not self.authenticate_server(response):
# Mutual authentication failure when mutual auth is wanted,
# raise an exception so the user doesn't use an untrusted
# response.
log.error("handle_other(): Mutual authentication failed")
raise MutualAuthenticationError("Unable to authenticate "
"{0}".format(response))
# Authentication successful
log.debug("handle_other(): returning {0}".format(response))
return response
elif is_http_error or self.mutual_authentication == OPTIONAL:
if not response.ok:
log.error("handle_other(): Mutual authentication unavailable "
"on {0} response".format(response.status_code))
if(self.mutual_authentication == REQUIRED and
self.sanitize_mutual_error_response):
return SanitizedResponse(response)
else:
return response
else:
# Unable to attempt mutual authentication when mutual auth is
# required, raise an exception so the user doesnt use an
# untrusted response.
log.error("handle_other(): Mutual authentication failed")
raise MutualAuthenticationError("Unable to authenticate "
"{0}".format(response))
else:
log.debug("handle_other(): returning {0}".format(response))
return response
def authenticate_server(self, response):
"""
Uses GSSAPI to authenticate the server.
Returns True on success, False on failure.
"""
log.debug("authenticate_server(): Authenticate header: {0}".format(
_negotiate_value(response)))
host = urlparse(response.url).hostname
try:
result = kerberos.authGSSClientStep(self.context[host],
_negotiate_value(response))
except kerberos.GSSError:
log.exception("authenticate_server(): authGSSClientStep() failed:")
return False
if result < 1:
log.error("authenticate_server(): authGSSClientStep() failed: "
"{0}".format(result))
return False
log.debug("authenticate_server(): returning {0}".format(response))
return True
def handle_response(self, response, **kwargs):
"""Takes the given response and tries kerberos-auth, as needed."""
num_401s = kwargs.pop('num_401s', 0)
if self.pos is not None:
# Rewind the file position indicator of the body to where
# it was to resend the request.
response.request.body.seek(self.pos)
if response.status_code == 401 and num_401s < 2:
# 401 Unauthorized. Handle it, and if it still comes back as 401,
# that means authentication failed.
_r = self.handle_401(response, **kwargs)
log.debug("handle_response(): returning %s", _r)
log.debug("handle_response() has seen %d 401 responses", num_401s)
num_401s += 1
return self.handle_response(_r, num_401s=num_401s, **kwargs)
elif response.status_code == 401 and num_401s >= 2:
# Still receiving 401 responses after attempting to handle them.
# Authentication has failed. Return the 401 response.
log.debug("handle_response(): returning 401 %s", response)
return response
else:
_r = self.handle_other(response)
log.debug("handle_response(): returning %s", _r)
return _r
def deregister(self, response):
"""Deregisters the response handler"""
response.request.deregister_hook('response', self.handle_response)
def __call__(self, request):
if self.force_preemptive:
# add Authorization header before we receive a 401
# by the 401 handler
host = urlparse(request.url).hostname
auth_header = self.generate_request_header(None, host, is_preemptive=True)
log.debug("HTTPKerberosAuth: Preemptive Authorization header: {0}".format(auth_header))
request.headers['Authorization'] = auth_header
request.register_hook('response', self.handle_response)
try:
self.pos = request.body.tell()
except AttributeError:
# In the case of HTTPKerberosAuth being reused and the body
# of the previous request was a file-like object, pos has
# the file position of the previous body. Ensure it's set to
# None.
self.pos = None
return request
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