feat: Add SSPI (Kerberos for Windows) authentication mechanism

kafka/conn.py

@@ -766,7 +766,7 @@ def _sasl_authenticate(self, future):
                 self._sasl_mechanism.receive(recv_token)
 
         if self._sasl_mechanism.is_authenticated():
-            log.info('%s: Authenticated via %s', self, self.config['sasl_mechanism'])
+            log.info('%s: %s', self, self._sasl_mechanism.auth_details())
             return future.success(True)
         else:
             return future.failure(Errors.AuthenticationFailedError('Failed to authenticate via SASL %s' % self.config['sasl_mechanism']))

kafka/sasl/__init__.py

@@ -1,10 +1,13 @@
 from __future__ import absolute_import
 
+import platform
+
 from kafka.sasl.gssapi import SaslMechanismGSSAPI
 from kafka.sasl.msk import SaslMechanismAwsMskIam
 from kafka.sasl.oauth import SaslMechanismOAuth
 from kafka.sasl.plain import SaslMechanismPlain
 from kafka.sasl.scram import SaslMechanismScram
+from kafka.sasl.sspi import SaslMechanismSSPI
 
 
 SASL_MECHANISMS = {}
@@ -20,9 +23,12 @@ def get_sasl_mechanism(name):
     return SASL_MECHANISMS[name]
 
 
-register_sasl_mechanism('GSSAPI', SaslMechanismGSSAPI)
+register_sasl_mechanism('AWS_MSK_IAM', SaslMechanismAwsMskIam)
+if platform.system() == 'Windows':
+    register_sasl_mechanism('GSSAPI', SaslMechanismSSPI)
+else:
+    register_sasl_mechanism('GSSAPI', SaslMechanismGSSAPI)
 register_sasl_mechanism('OAUTHBEARER', SaslMechanismOAuth)
 register_sasl_mechanism('PLAIN', SaslMechanismPlain)
 register_sasl_mechanism('SCRAM-SHA-256', SaslMechanismScram)
 register_sasl_mechanism('SCRAM-SHA-512', SaslMechanismScram)
-register_sasl_mechanism('AWS_MSK_IAM', SaslMechanismAwsMskIam)

kafka/sasl/abc.py

@@ -25,3 +25,8 @@ def is_done(self):
     @abc.abstractmethod
     def is_authenticated(self):
         pass
+
+    def auth_details(self):
+        if not self.is_authenticated:
+            raise RuntimeError('Not authenticated yet!')
+        return 'Authenticated via SASL'

kafka/sasl/gssapi.py

@@ -1,7 +1,5 @@
 from __future__ import absolute_import
 
-import struct
-
 # needed for SASL_GSSAPI authentication:
 try:
     import gssapi
@@ -67,10 +65,12 @@ def receive(self, auth_bytes):
             # Kafka currently doesn't support integrity or confidentiality security layers, so we
             # simply set QoP to 'auth' only (first octet). We reuse the max message size proposed
             # by the server
+            client_flags = self.SASL_QOP_AUTH
+            server_flags = msg[0]
             message_parts = [
-                struct.pack('>b', self.SASL_QOP_AUTH & struct.unpack('>b', msg[0:1])),
+                bytes(client_flags & server_flags),
                 msg[:1],
-                self.auth_id.encode(),
+                self.auth_id.encode('utf-8'),
             ]
             # add authorization identity to the response, and GSS-wrap
             self._next_token = self._client_ctx.wrap(b''.join(message_parts), False).message
@@ -80,3 +80,8 @@ def is_done(self):
 
     def is_authenticated(self):
         return self._is_authenticated
+
+    def auth_details(self):
+        if not self.is_authenticated:
+            raise RuntimeError('Not authenticated yet!')
+        return 'Authenticated as %s to %s via SASL / GSSAPI' % (self._client_ctx.initiator_name, self._client_ctx.target_name)

kafka/sasl/oauth.py

@@ -37,3 +37,8 @@ def _token_extensions(self):
         extensions = getattr(self.token_provider, 'extensions', lambda: [])()
         msg = '\x01'.join(['{}={}'.format(k, v) for k, v in extensions.items()])
         return '\x01' + msg if msg else ''
+
+    def auth_details(self):
+        if not self.is_authenticated:
+            raise RuntimeError('Not authenticated yet!')
+        return 'Authenticated via SASL / OAuth'

kafka/sasl/plain.py

@@ -34,3 +34,8 @@ def is_done(self):
 
     def is_authenticated(self):
         return self._is_authenticated
+
+    def auth_details(self):
+        if not self.is_authenticated:
+            raise RuntimeError('Not authenticated yet!')
+        return 'Authenticated as %s via SASL / Plain' % self.username

kafka/sasl/scram.py

@@ -30,6 +30,8 @@ def __init__(self, **config):
         if config.get('security_protocol', '') == 'SASL_PLAINTEXT':
             log.warning('Exchanging credentials in the clear during Sasl Authentication')
 
+        self.username = config['sasl_plain_username']
+        self.mechanism = config['sasl_mechanism']
         self._scram_client = ScramClient(
             config['sasl_plain_username'],
             config['sasl_plain_password'],
@@ -62,6 +64,11 @@ def is_authenticated(self):
         # receive raises if authentication fails...?
         return self._state == 2
 
+    def auth_details(self):
+        if not self.is_authenticated:
+            raise RuntimeError('Not authenticated yet!')
+        return 'Authenticated as %s via SASL / %s' % (self.username, self.mechanism)
+
 
 class ScramClient:
     MECHANISMS = {

kafka/sasl/sspi.py

@@ -0,0 +1,111 @@
+from __future__ import absolute_import
+
+import logging
+
+# Windows-only
+try:
+    import sspi
+    import pywintypes
+    import sspicon
+    import win32security
+except ImportError:
+    sspi = None
+
+from kafka.sasl.abc import SaslMechanism
+
+
+log = logging.getLogger(__name__)
+
+
+class SaslMechanismSSPI(SaslMechanism):
+    # Establish security context and negotiate protection level
+    # For reference see RFC 4752, section 3
+
+    SASL_QOP_AUTH = 1
+    SASL_QOP_AUTH_INT = 2
+    SASL_QOP_AUTH_CONF = 4
+
+    def __init__(self, **config):
+        assert sspi is not None, 'No GSSAPI lib available (gssapi or sspi)'
+        if 'sasl_kerberos_name' not in config and 'sasl_kerberos_service_name' not in config:
+            raise ValueError('sasl_kerberos_service_name or sasl_kerberos_name required for GSSAPI sasl configuration')
+        self._is_done = False
+        self._is_authenticated = False
+        if config.get('sasl_kerberos_name', None) is not None:
+            self.auth_id = str(config['sasl_kerberos_name'])
+        else:
+            kerberos_domain_name = config.get('sasl_kerberos_domain_name', '') or config.get('host', '')
+            self.auth_id = config['sasl_kerberos_service_name'] + '/' + kerberos_domain_name
+        scheme = "Kerberos"  # Do not try with Negotiate for SASL authentication. Tokens are different.
+        # https://docs.microsoft.com/en-us/windows/win32/secauthn/context-requirements
+        flags = (
+            sspicon.ISC_REQ_MUTUAL_AUTH |      # mutual authentication
+            sspicon.ISC_REQ_INTEGRITY |        # check for integrity
+            sspicon.ISC_REQ_SEQUENCE_DETECT |  # enable out-of-order messages
+            sspicon.ISC_REQ_CONFIDENTIALITY    # request confidentiality
+        )
+        self._client_ctx = sspi.ClientAuth(scheme, targetspn=self.auth_id, scflags=flags)
+        self._next_token = self._client_ctx.step(None)
+
+    def auth_bytes(self):
+        # GSSAPI Auth does not have a final broker->client message
+        # so mark is_done after the final auth_bytes are provided
+        # in practice we'll still receive a response when using SaslAuthenticate
+        # but not when using the prior unframed approach.
+        if self._client_ctx.authenticated:
+            self._is_done = True
+            self._is_authenticated = True
+        return self._next_token or b''
+
+    def receive(self, auth_bytes):
+        log.debug("Received token from server (size %s)", len(auth_bytes))
+        if not self._client_ctx.authenticated:
+            # calculate an output token from kafka token (or None on first iteration)
+            # https://docs.microsoft.com/en-us/windows/win32/api/sspi/nf-sspi-initializesecuritycontexta
+            # https://docs.microsoft.com/en-us/windows/win32/secauthn/initializesecuritycontext--kerberos
+            # authorize method will wrap for us our token in sspi structures
+            error, auth = self._client_ctx.authorize(auth_bytes)
+            if len(auth) > 0 and len(auth[0].Buffer):
+                log.debug("Got token from context")
+                # this buffer must be sent to the server whatever the result is
+                self._next_token = auth[0].Buffer
+            else:
+                log.debug("Got no token, exchange finished")
+                # seems to be the end of the loop
+                self._next_token = b''
+        elif self._is_done:
+            # The final step of gssapi is send, so we do not expect any additional bytes
+            # however, allow an empty message to support SaslAuthenticate response
+            if auth_bytes != b'':
+                raise ValueError("Unexpected receive auth_bytes after sasl/gssapi completion")
+        else:
+            # Process the security layer negotiation token, sent by the server
+            # once the security context is established.
+
+            # The following part is required by SASL, but not by classic Kerberos.
+            # See RFC 4752
+
+            # unwraps message containing supported protection levels and msg size
+            msg, _was_encrypted = self._client_ctx.unwrap(auth_bytes)
+
+            # Kafka currently doesn't support integrity or confidentiality security layers, so we
+            # simply set QoP to 'auth' only (first octet). We reuse the max message size proposed
+            # by the server
+            client_flags = self.SASL_QOP_AUTH
+            server_flags = msg[0]
+            message_parts = [
+                bytes(client_flags & server_flags),
+                msg[:1],
+                self.auth_id.encode('utf-8'),
+            ]
+            # add authorization identity to the response, and GSS-wrap
+            self._next_token = self._client_ctx.wrap(b''.join(message_parts), False)
+
+    def is_done(self):
+        return self._is_done
+
+    def is_authenticated(self):
+        return self._is_authenticated
+
+    def auth_details(self):
+        return 'Authenticated as %s to %s via SASL / SSPI/GSSAPI \\o/' % (self._client_ctx.initiator_name, self._client_ctx.service_name)