kube_config.py

# Copyright 2016 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 atexit
import base64
import os
import tempfile

import urllib3
import yaml
from oauth2client.client import GoogleCredentials

from kubernetes.client import ApiClient, ConfigurationObject, configuration

from .config_exception import ConfigException

KUBE_CONFIG_DEFAULT_LOCATION = '~/.kube/config'
_temp_files = {}


def _cleanup_temp_files():
    global _temp_files
    for temp_file in _temp_files.values():
        try:
            os.remove(temp_file)
        except OSError:
            pass
    _temp_files = {}


def _create_temp_file_with_content(content):
    if len(_temp_files) == 0:
        atexit.register(_cleanup_temp_files)
    # Because we may change context several times, try to remember files we
    # created and reuse them at a small memory cost.
    content_key = str(content)
    if content_key in _temp_files:
        return _temp_files[content_key]
    _, name = tempfile.mkstemp()
    _temp_files[content_key] = name
    with open(name, 'wb') as fd:
        fd.write(content.encode() if isinstance(content, str) else content)
    return name


class FileOrData(object):
    """Utility class to read content of obj[%data_key_name] or file's
     content of obj[%file_key_name] and represent it as file or data.
     Note that the data is preferred. The obj[%file_key_name] will be used iff
     obj['%data_key_name'] is not set or empty. Assumption is file content is
     raw data and data field is base64 string. The assumption can be changed
     with base64_file_content flag. If set to False, the content of the file
     will assumed to be base64 and read as is. The default True value will
     result in base64 encode of the file content after read."""

    def __init__(self, obj, file_key_name, data_key_name=None,
                 file_base_path="", base64_file_content=True):
        if not data_key_name:
            data_key_name = file_key_name + "-data"
        self._file = None
        self._data = None
        self._base64_file_content = base64_file_content
        if data_key_name in obj:
            self._data = obj[data_key_name]
        elif file_key_name in obj:
            self._file = os.path.normpath(
                os.path.join(file_base_path, obj[file_key_name]))

    def as_file(self):
        """If obj[%data_key_name] exists, return name of a file with base64
        decoded obj[%data_key_name] content otherwise obj[%file_key_name]."""
        use_data_if_no_file = not self._file and self._data
        if use_data_if_no_file:
            if self._base64_file_content:
                self._file = _create_temp_file_with_content(
                    base64.decodestring(self._data.encode()))
            else:
                self._file = _create_temp_file_with_content(self._data)
        if self._file and not os.path.isfile(self._file):
            raise ConfigException("File does not exists: %s" % self._file)
        return self._file

    def as_data(self):
        """If obj[%data_key_name] exists, Return obj[%data_key_name] otherwise
        base64 encoded string of obj[%file_key_name] file content."""
        use_file_if_no_data = not self._data and self._file
        if use_file_if_no_data:
            with open(self._file) as f:
                if self._base64_file_content:
                    self._data = bytes.decode(
                        base64.encodestring(str.encode(f.read())))
                else:
                    self._data = f.read()
        return self._data


class KubeConfigLoader(object):

    def __init__(self, config_dict, active_context=None,
                 get_google_credentials=None,
                 client_configuration=configuration,
                 config_base_path=""):
        self._config = ConfigNode('kube-config', config_dict)
        self._current_context = None
        self._user = None
        self._cluster = None
        self.set_active_context(active_context)
        self._config_base_path = config_base_path
        if get_google_credentials:
            self._get_google_credentials = get_google_credentials
        else:
            self._get_google_credentials = lambda: (
                GoogleCredentials.get_application_default()
                .get_access_token().access_token)
        self._client_configuration = client_configuration

    def set_active_context(self, context_name=None):
        if context_name is None:
            context_name = self._config['current-context']
        self._current_context = self._config['contexts'].get_with_name(
            context_name)
        if self._current_context['context'].safe_get('user'):
            self._user = self._config['users'].get_with_name(
                self._current_context['context']['user'])['user']
        else:
            self._user = None
        self._cluster = self._config['clusters'].get_with_name(
            self._current_context['context']['cluster'])['cluster']

    def _load_authentication(self):
        """Read authentication from kube-config user section if exists.

        This function goes through various authentication methods in user
        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. username/password
        """
        if not self._user:
            return
        if self._load_gcp_token():
            return
        if self._load_user_token():
            return
        self._load_user_pass_token()

    def _load_gcp_token(self):
        if 'auth-provider' not in self._user:
            return
        if 'name' not in self._user['auth-provider']:
            return
        if self._user['auth-provider']['name'] != 'gcp':
            return
        # Ignore configs in auth-provider and rely on GoogleCredentials
        # caching and refresh mechanism.
        # TODO: support gcp command based token ("cmd-path" config).
        self.token = "Bearer %s" % self._get_google_credentials()
        return self.token

    def _load_user_token(self):
        token = FileOrData(
            self._user, 'tokenFile', 'token',
            file_base_path=self._config_base_path,
            base64_file_content=False).as_data()
        if token:
            self.token = "Bearer %s" % token
            return True

    def _load_user_pass_token(self):
        if 'username' in self._user and 'password' in self._user:
            self.token = urllib3.util.make_headers(
                basic_auth=(self._user['username'] + ':' +
                            self._user['password'])).get('authorization')
            return True

    def _load_cluster_info(self):
        if 'server' in self._cluster:
            self.host = self._cluster['server']
            if self.host.startswith("https"):
                self.ssl_ca_cert = FileOrData(
                    self._cluster, 'certificate-authority',
                    file_base_path=self._config_base_path).as_file()
                self.cert_file = FileOrData(
                    self._user, 'client-certificate',
                    file_base_path=self._config_base_path).as_file()
                self.key_file = FileOrData(
                    self._user, 'client-key',
                    file_base_path=self._config_base_path).as_file()
        if 'insecure-skip-tls-verify' in self._cluster:
            self.verify_ssl = not self._cluster['insecure-skip-tls-verify']

    def _set_config(self):
        if 'token' in self.__dict__:
            self._client_configuration.api_key['authorization'] = self.token
        # copy these keys directly from self to configuration object
        keys = ['host', 'ssl_ca_cert', 'cert_file', 'key_file', 'verify_ssl']
        for key in keys:
            if key in self.__dict__:
                setattr(self._client_configuration, key, getattr(self, key))

    def load_and_set(self):
        self._load_authentication()
        self._load_cluster_info()
        self._set_config()

    def list_contexts(self):
        return [context.value for context in self._config['contexts']]

    @property
    def current_context(self):
        return self._current_context.value


class ConfigNode(object):
    """Remembers each config key's path and construct a relevant exception
    message in case of missing keys. The assumption is all access keys are
    present in a well-formed kube-config."""

    def __init__(self, name, value):
        self.name = name
        self.value = value

    def __contains__(self, key):
        return key in self.value

    def __len__(self):
        return len(self.value)

    def safe_get(self, key):
        if (isinstance(self.value, list) and isinstance(key, int) or
                key in self.value):
            return self.value[key]

    def __getitem__(self, key):
        v = self.safe_get(key)
        if not v:
            raise ConfigException(
                'Invalid kube-config file. Expected key %s in %s'
                % (key, self.name))
        if isinstance(v, dict) or isinstance(v, list):
            return ConfigNode('%s/%s' % (self.name, key), v)
        else:
            return v

    def get_with_name(self, name):
        if not isinstance(self.value, list):
            raise ConfigException(
                'Invalid kube-config file. Expected %s to be a list'
                % self.name)
        for v in self.value:
            if 'name' not in v:
                raise ConfigException(
                    'Invalid kube-config file. '
                    'Expected all values in %s list to have \'name\' key'
                    % self.name)
            if v['name'] == name:
                return ConfigNode('%s[name=%s]' % (self.name, name), v)
        raise ConfigException(
            'Invalid kube-config file. '
            'Expected object with name %s in %s list' % (name, self.name))


def _get_kube_config_loader_for_yaml_file(filename, **kwargs):
    with open(filename) as f:
        return KubeConfigLoader(
            config_dict=yaml.load(f),
            config_base_path=os.path.abspath(os.path.dirname(filename)),
            **kwargs)


def list_kube_config_contexts(config_file=None):

    if config_file is None:
        config_file = os.path.expanduser(KUBE_CONFIG_DEFAULT_LOCATION)

    loader = _get_kube_config_loader_for_yaml_file(config_file)
    return loader.list_contexts(), loader.current_context


def load_kube_config(config_file=None, context=None,
                     client_configuration=configuration):
    """Loads authentication and cluster information from kube-config file
    and stores them in kubernetes.client.configuration.

    :param config_file: Name of the kube-config file.
    :param context: set the active context. If is set to None, current_context
        from config file will be used.
    :param client_configuration: The kubernetes.client.ConfigurationObject to
        set configs to.
    """

    if config_file is None:
        config_file = os.path.expanduser(KUBE_CONFIG_DEFAULT_LOCATION)

    _get_kube_config_loader_for_yaml_file(
        config_file, active_context=context,
        client_configuration=client_configuration).load_and_set()


def new_client_from_config(config_file=None, context=None):
    """Loads configuration the same as load_kube_config but returns an ApiClient
    to be used with any API object. This will allow the caller to concurrently
    talk with multiple clusters."""
    client_config = ConfigurationObject()
    load_kube_config(config_file=config_file, context=context,
                     client_configuration=client_config)
    return ApiClient(config=client_config)