Attempt to implement exec-plugins support in kubeconfig

config/exec_provider.py

@@ -0,0 +1,90 @@
+# Copyright 2018 The Kubernetes Authors.
+#
+# 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 json
+import os
+import subprocess
+import sys
+
+from .config_exception import ConfigException
+
+
+class ExecProvider(object):
+    """
+    Implementation of the proposal for out-of-tree client authentication providers
+    as described here --
+    https://github.com/kubernetes/community/blob/master/contributors/design-proposals/auth/kubectl-exec-plugins.md
+
+    Missing from implementation:
+
+    * TLS cert support
+    * caching
+    """
+
+    def __init__(self, exec_config):
+        for key in ['command', 'apiVersion']:
+            if key not in exec_config:
+                raise ConfigException(
+                    'exec: malformed request. missing key \'%s\'' % key)
+        self.api_version = exec_config['apiVersion']
+        self.args = [exec_config['command']]
+        if 'args' in exec_config:
+            self.args.extend(exec_config['args'])
+        self.env = os.environ.copy()
+        if 'env' in exec_config:
+            additional_vars = {}
+            for item in exec_config['env']:
+                name = item['name']
+                value = item['value']
+                additional_vars[name] = value
+            self.env.update(additional_vars)
+
+    def run(self, previous_response=None):
+        kubernetes_exec_info = {
+            'apiVersion': self.api_version,
+            'kind': 'ExecCredential',
+            'spec': {
+                'interactive': sys.stdout.isatty()
+            }
+        }
+        if previous_response:
+            kubernetes_exec_info['spec']['response'] = previous_response
+        self.env['KUBERNETES_EXEC_INFO'] = json.dumps(kubernetes_exec_info)
+        process = subprocess.Popen(
+            self.args,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            env=self.env,
+            universal_newlines=True)
+        (stdout, stderr) = process.communicate()
+        exit_code = process.wait()
+        if exit_code != 0:
+            msg = 'exec: process returned %d' % exit_code
+            stderr = stderr.strip()
+            if stderr:
+                msg += '. %s' % stderr
+            raise ConfigException(msg)
+        try:
+            data = json.loads(stdout)
+        except ValueError as de:
+            raise ConfigException(
+                'exec: failed to decode process output: %s' % de)
+        for key in ('apiVersion', 'kind', 'status'):
+            if key not in data:
+                raise ConfigException(
+                    'exec: malformed response. missing key \'%s\'' % key)
+        if data['apiVersion'] != self.api_version:
+            raise ConfigException(
+                'exec: plugin api version %s does not match %s' %
+                (data['apiVersion'], self.api_version))
+        return data['status']

config/exec_provider_test.py

@@ -0,0 +1,140 @@
+# Copyright 2018 The Kubernetes Authors.
+#
+# 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 os
+import unittest
+
+import mock
+
+from .config_exception import ConfigException
+from .exec_provider import ExecProvider
+
+
+class ExecProviderTest(unittest.TestCase):
+
+    def setUp(self):
+        self.input_ok = {
+            'command': 'aws-iam-authenticator token -i dummy',
+            'apiVersion': 'client.authentication.k8s.io/v1beta1'
+        }
+        self.output_ok = """
+        {
+            "apiVersion": "client.authentication.k8s.io/v1beta1",
+            "kind": "ExecCredential",
+            "status": {
+                "token": "dummy"
+            }
+        }
+        """
+
+    def test_missing_input_keys(self):
+        exec_configs = [{}, {'command': ''}, {'apiVersion': ''}]
+        for exec_config in exec_configs:
+            with self.assertRaises(ConfigException) as context:
+                ExecProvider(exec_config)
+            self.assertIn('exec: malformed request. missing key',
+                          context.exception.args[0])
+
+    @mock.patch('subprocess.Popen')
+    def test_error_code_returned(self, mock):
+        instance = mock.return_value
+        instance.wait.return_value = 1
+        instance.communicate.return_value = ('', '')
+        with self.assertRaises(ConfigException) as context:
+            ep = ExecProvider(self.input_ok)
+            ep.run()
+        self.assertIn('exec: process returned %d' %
+                      instance.wait.return_value, context.exception.args[0])
+
+    @mock.patch('subprocess.Popen')
+    def test_nonjson_output_returned(self, mock):
+        instance = mock.return_value
+        instance.wait.return_value = 0
+        instance.communicate.return_value = ('', '')
+        with self.assertRaises(ConfigException) as context:
+            ep = ExecProvider(self.input_ok)
+            ep.run()
+        self.assertIn('exec: failed to decode process output',
+                      context.exception.args[0])
+
+    @mock.patch('subprocess.Popen')
+    def test_missing_output_keys(self, mock):
+        instance = mock.return_value
+        instance.wait.return_value = 0
+        outputs = [
+            """
+            {
+                "kind": "ExecCredential",
+                "status": {
+                    "token": "dummy"
+                }
+            }
+            """, """
+            {
+                "apiVersion": "client.authentication.k8s.io/v1beta1",
+                "status": {
+                    "token": "dummy"
+                }
+            }
+            """, """
+            {
+                "apiVersion": "client.authentication.k8s.io/v1beta1",
+                "kind": "ExecCredential"
+            }
+            """
+        ]
+        for output in outputs:
+            instance.communicate.return_value = (output, '')
+            with self.assertRaises(ConfigException) as context:
+                ep = ExecProvider(self.input_ok)
+                ep.run()
+            self.assertIn('exec: malformed response. missing key',
+                          context.exception.args[0])
+
+    @mock.patch('subprocess.Popen')
+    def test_mismatched_api_version(self, mock):
+        instance = mock.return_value
+        instance.wait.return_value = 0
+        wrong_api_version = 'client.authentication.k8s.io/v1'
+        output = """
+        {
+            "apiVersion": "%s",
+            "kind": "ExecCredential",
+            "status": {
+                "token": "dummy"
+            }
+        }
+        """ % wrong_api_version
+        instance.communicate.return_value = (output, '')
+        with self.assertRaises(ConfigException) as context:
+            ep = ExecProvider(self.input_ok)
+            ep.run()
+        self.assertIn(
+            'exec: plugin api version %s does not match' %
+            wrong_api_version,
+            context.exception.args[0])
+
+    @mock.patch('subprocess.Popen')
+    def test_ok_01(self, mock):
+        instance = mock.return_value
+        instance.wait.return_value = 0
+        instance.communicate.return_value = (self.output_ok, '')
+        ep = ExecProvider(self.input_ok)
+        result = ep.run()
+        self.assertTrue(isinstance(result, dict))
+        self.assertTrue('token' in result)
+
+
+if __name__ == '__main__':
+    unittest.main()

config/kube_config.py

@@ -1,4 +1,4 @@
-# Copyright 2016 The Kubernetes Authors.
+# Copyright 2018 The Kubernetes Authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 import base64
 import datetime
 import json
+import logging
 import os
 import tempfile
 import time
@@ -30,6 +31,7 @@
 from six import PY3
 
 from kubernetes.client import ApiClient, Configuration
+from kubernetes.config.exec_provider import ExecProvider
 
 from .config_exception import ConfigException
 from .dateutil import UTC, format_rfc3339, parse_rfc3339
@@ -172,18 +174,19 @@ def _load_authentication(self):
         section of kube-config and stops if it finds a valid authentication
         method. The order of authentication methods is:
 
-            1. GCP auth-provider
-            2. token_data
-            3. token field (point to a token file)
-            4. oidc auth-provider
-            5. username/password
+            1. auth-provider (gcp, azure, oidc)
+            2. token field (point to a token file)
+            3. exec provided plugin
+            4. username/password
         """
         if not self._user:
             return
         if self._load_auth_provider_token():
             return
         if self._load_user_token():
             return
+        if self._load_from_exec_plugin():
+            return
         self._load_user_pass_token()
 
     def _load_auth_provider_token(self):
@@ -340,6 +343,19 @@ def _refresh_oidc(self, provider):
         provider['config'].value['id-token'] = refresh['id_token']
         provider['config'].value['refresh-token'] = refresh['refresh_token']
 
+    def _load_from_exec_plugin(self):
+        if 'exec' not in self._user:
+            return
+        try:
+            status = ExecProvider(self._user['exec']).run()
+            if 'token' not in status:
+                logging.error('exec: missing token field in plugin output')
+                return None
+            self.token = "Bearer %s" % status['token']
+            return True
+        except Exception as e:
+            logging.error(str(e))
+
     def _load_user_token(self):
         token = FileOrData(
             self._user, 'tokenFile', 'token',

config/kube_config_test.py

@@ -1,4 +1,4 @@
-# Copyright 2016 The Kubernetes Authors.
+# Copyright 2018 The Kubernetes Authors.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -422,6 +422,13 @@ class TestKubeConfigLoader(BaseTestCase):
                     "user": "non_existing_user"
                 }
             },
+            {
+                "name": "exec_cred_user",
+                "context": {
+                    "cluster": "default",
+                    "user": "exec_cred_user"
+                }
+            },
         ],
         "clusters": [
             {
@@ -573,6 +580,16 @@ class TestKubeConfigLoader(BaseTestCase):
                     "client-key-data": TEST_CLIENT_KEY_BASE64,
                 }
             },
+            {
+                "name": "exec_cred_user",
+                "user": {
+                    "exec": {
+                        "apiVersion": "client.authentication.k8s.io/v1beta1",
+                        "command": "aws-iam-authenticator",
+                        "args": ["token", "-i", "dummy-cluster"]
+                    }
+                }
+            },
         ]
     }
 
@@ -849,6 +866,20 @@ def test_non_existing_user(self):
             active_context="non_existing_user").load_and_set(actual)
         self.assertEqual(expected, actual)
 
+    @mock.patch('kubernetes.config.kube_config.ExecProvider.run')
+    def test_user_exec_auth(self, mock):
+        token = "dummy"
+        mock.return_value = {
+            "token": token
+        }
+        expected = FakeConfig(host=TEST_HOST, api_key={
+                              "authorization": BEARER_TOKEN_FORMAT % token})
+        actual = FakeConfig()
+        KubeConfigLoader(
+            config_dict=self.TEST_KUBE_CONFIG,
+            active_context="exec_cred_user").load_and_set(actual)
+        self.assertEqual(expected, actual)
+
 
 if __name__ == '__main__':
     unittest.main()