API refactor

venv/lib/python3.12/site-packages/kafka/sasl/gssapi.py

@@ -0,0 +1,96 @@
+from __future__ import absolute_import
+
+import struct
+
+# needed for SASL_GSSAPI authentication:
+try:
+    import gssapi
+    from gssapi.raw.misc import GSSError
+except (ImportError, OSError):
+    #no gssapi available, will disable gssapi mechanism
+    gssapi = None
+    GSSError = None
+
+from kafka.sasl.abc import SaslMechanism
+
+
+class SaslMechanismGSSAPI(SaslMechanism):
+    # Establish security context and negotiate protection level
+    # For reference RFC 2222, section 7.2.1
+
+    SASL_QOP_AUTH = 1
+    SASL_QOP_AUTH_INT = 2
+    SASL_QOP_AUTH_CONF = 4
+
+    def __init__(self, **config):
+        assert gssapi is not None, 'GSSAPI lib not available'
+        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
+        self.gssapi_name = None
+        if config.get('sasl_kerberos_name', None) is not None:
+            self.auth_id = str(config['sasl_kerberos_name'])
+            if isinstance(config['sasl_kerberos_name'], gssapi.Name):
+                self.gssapi_name = 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
+        if self.gssapi_name is None:
+            self.gssapi_name = gssapi.Name(self.auth_id, name_type=gssapi.NameType.hostbased_service).canonicalize(gssapi.MechType.kerberos)
+        self._client_ctx = gssapi.SecurityContext(name=self.gssapi_name, usage='initiate')
+        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._is_authenticated:
+            self._is_done = True
+        return self._next_token or b''
+
+    def receive(self, auth_bytes):
+        if not self._client_ctx.complete:
+            # The server will send a token back. Processing of this token either
+            # establishes a security context, or it needs further token exchange.
+            # The gssapi will be able to identify the needed next step.
+            self._next_token = self._client_ctx.step(auth_bytes)
+        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:
+            # unwraps message containing supported protection levels and msg size
+            msg = self._client_ctx.unwrap(auth_bytes).message
+            # 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 = struct.Struct('>b').unpack(msg[0:1])[0]
+            message_parts = [
+                struct.Struct('>b').pack(client_flags & server_flags),
+                msg[1:], # always agree to max message size from server
+                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
+            # We need to identify the last token in auth_bytes();
+            # we can't rely on client_ctx.complete because it becomes True after generating
+            # the second-to-last token (after calling .step(auth_bytes) for the final time)
+            # We could introduce an additional state variable (i.e., self._final_token),
+            # but instead we just set _is_authenticated. Since the plugin interface does
+            # not read is_authenticated() until after is_done() is True, this should be fine.
+            self._is_authenticated = True
+
+    def is_done(self):
+        return self._is_done
+
+    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)