Andrew K. Choi
91c7e04474
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112 lines
4.9 KiB
Python
112 lines
4.9 KiB
Python
from __future__ import absolute_import
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import logging
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# Windows-only
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try:
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import sspi
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import pywintypes
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import sspicon
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import win32security
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except ImportError:
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sspi = None
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from kafka.sasl.abc import SaslMechanism
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log = logging.getLogger(__name__)
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class SaslMechanismSSPI(SaslMechanism):
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# Establish security context and negotiate protection level
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# For reference see RFC 4752, section 3
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SASL_QOP_AUTH = 1
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SASL_QOP_AUTH_INT = 2
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SASL_QOP_AUTH_CONF = 4
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def __init__(self, **config):
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assert sspi is not None, 'No GSSAPI lib available (gssapi or sspi)'
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if 'sasl_kerberos_name' not in config and 'sasl_kerberos_service_name' not in config:
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raise ValueError('sasl_kerberos_service_name or sasl_kerberos_name required for GSSAPI sasl configuration')
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self._is_done = False
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self._is_authenticated = False
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if config.get('sasl_kerberos_name', None) is not None:
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self.auth_id = str(config['sasl_kerberos_name'])
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else:
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kerberos_domain_name = config.get('sasl_kerberos_domain_name', '') or config.get('host', '')
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self.auth_id = config['sasl_kerberos_service_name'] + '/' + kerberos_domain_name
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scheme = "Kerberos" # Do not try with Negotiate for SASL authentication. Tokens are different.
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# https://docs.microsoft.com/en-us/windows/win32/secauthn/context-requirements
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flags = (
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sspicon.ISC_REQ_MUTUAL_AUTH | # mutual authentication
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sspicon.ISC_REQ_INTEGRITY | # check for integrity
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sspicon.ISC_REQ_SEQUENCE_DETECT | # enable out-of-order messages
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sspicon.ISC_REQ_CONFIDENTIALITY # request confidentiality
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)
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self._client_ctx = sspi.ClientAuth(scheme, targetspn=self.auth_id, scflags=flags)
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self._next_token = self._client_ctx.step(None)
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def auth_bytes(self):
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# GSSAPI Auth does not have a final broker->client message
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# so mark is_done after the final auth_bytes are provided
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# in practice we'll still receive a response when using SaslAuthenticate
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# but not when using the prior unframed approach.
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if self._client_ctx.authenticated:
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self._is_done = True
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self._is_authenticated = True
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return self._next_token or b''
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def receive(self, auth_bytes):
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log.debug("Received token from server (size %s)", len(auth_bytes))
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if not self._client_ctx.authenticated:
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# calculate an output token from kafka token (or None on first iteration)
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# https://docs.microsoft.com/en-us/windows/win32/api/sspi/nf-sspi-initializesecuritycontexta
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# https://docs.microsoft.com/en-us/windows/win32/secauthn/initializesecuritycontext--kerberos
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# authorize method will wrap for us our token in sspi structures
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error, auth = self._client_ctx.authorize(auth_bytes)
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if len(auth) > 0 and len(auth[0].Buffer):
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log.debug("Got token from context")
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# this buffer must be sent to the server whatever the result is
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self._next_token = auth[0].Buffer
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else:
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log.debug("Got no token, exchange finished")
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# seems to be the end of the loop
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self._next_token = b''
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elif self._is_done:
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# The final step of gssapi is send, so we do not expect any additional bytes
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# however, allow an empty message to support SaslAuthenticate response
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if auth_bytes != b'':
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raise ValueError("Unexpected receive auth_bytes after sasl/gssapi completion")
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else:
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# Process the security layer negotiation token, sent by the server
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# once the security context is established.
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# The following part is required by SASL, but not by classic Kerberos.
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# See RFC 4752
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# unwraps message containing supported protection levels and msg size
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msg, _was_encrypted = self._client_ctx.unwrap(auth_bytes)
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# Kafka currently doesn't support integrity or confidentiality security layers, so we
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# simply set QoP to 'auth' only (first octet). We reuse the max message size proposed
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# by the server
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client_flags = self.SASL_QOP_AUTH
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server_flags = msg[0]
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message_parts = [
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bytes(client_flags & server_flags),
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msg[:1],
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self.auth_id.encode('utf-8'),
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]
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# add authorization identity to the response, and GSS-wrap
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self._next_token = self._client_ctx.wrap(b''.join(message_parts), False)
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def is_done(self):
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return self._is_done
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def is_authenticated(self):
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return self._is_authenticated
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def auth_details(self):
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return 'Authenticated as %s to %s via SASL / SSPI/GSSAPI \\o/' % (self._client_ctx.initiator_name, self._client_ctx.service_name)
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