internal/lib/auth.py

#!/usr/bin/env python
#
# Copyright 2016 - The Android Open Source Project
#
# 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.
"""Module for handling Authentication.

Possible cases of authentication are noted below.

--------------------------------------------------------
     account                   | authentcation
--------------------------------------------------------

google account (e.g. gmail)*   | normal oauth2


service account*               | oauth2 + private key

--------------------------------------------------------

* For now, non-google employees (i.e. non @google.com account) or
  non-google-owned service account can not access Android Build API.
  Only local build artifact can be used.

* Google-owned service account, if used, needs to be whitelisted by
  Android Build team so that acloud can access build api.
"""

import logging
import os

import httplib2

# pylint: disable=import-error
from oauth2client import client as oauth2_client
from oauth2client import service_account as oauth2_service_account
from oauth2client.contrib import multistore_file
from oauth2client import tools as oauth2_tools

from acloud.public import errors

logger = logging.getLogger(__name__)
HOME_FOLDER = os.path.expanduser("~")


def _CreateOauthServiceAccountCreds(email, private_key_path, scopes):
    """Create credentials with a normal service account.

    Args:
        email: email address as the account.
        private_key_path: Path to the service account P12 key.
        scopes: string, multiple scopes should be saperated by space.
                        Api scopes to request for the oauth token.

    Returns:
        An oauth2client.OAuth2Credentials instance.

    Raises:
        errors.AuthentcationError: if failed to authenticate.
    """
    try:
        credentials = oauth2_service_account.ServiceAccountCredentials.from_p12_keyfile(
            email, private_key_path, scopes=scopes)
    except EnvironmentError as e:
        raise errors.AuthentcationError(
            "Could not authenticate using private key file (%s) "
            " error message: %s" % (private_key_path, str(e)))
    return credentials


class RunFlowFlags(object):
    """Flags for oauth2client.tools.run_flow."""

    def __init__(self, browser_auth):
        self.auth_host_port = [8080, 8090]
        self.auth_host_name = "localhost"
        self.logging_level = "ERROR"
        self.noauth_local_webserver = not browser_auth


def _RunAuthFlow(storage, client_id, client_secret, user_agent, scopes):
    """Get user oauth2 credentials.

    Args:
        client_id: String, client id from the cloud project.
        client_secret: String, client secret for the client_id.
        user_agent: The user agent for the credential, e.g. "acloud"
        scopes: String, scopes separated by space.

    Returns:
        An oauth2client.OAuth2Credentials instance.
    """
    flags = RunFlowFlags(browser_auth=False)
    flow = oauth2_client.OAuth2WebServerFlow(
        client_id=client_id,
        client_secret=client_secret,
        scope=scopes,
        user_agent=user_agent)
    credentials = oauth2_tools.run_flow(
        flow=flow, storage=storage, flags=flags)
    return credentials


def _CreateOauthUserCreds(creds_cache_file, client_id, client_secret,
                          user_agent, scopes):
    """Get user oauth2 credentials.

    Args:
        creds_cache_file: String, file name for the credential cache.
                                            e.g. .acloud_oauth2.dat
                                            Will be created at home folder.
        client_id: String, client id from the cloud project.
        client_secret: String, client secret for the client_id.
        user_agent: The user agent for the credential, e.g. "acloud"
        scopes: String, scopes separated by space.

    Returns:
        An oauth2client.OAuth2Credentials instance.
    """
    if not client_id or not client_secret:
        raise errors.AuthentcationError(
            "Could not authenticate using Oauth2 flow, please set client_id "
            "and client_secret in your config file. Contact the cloud project's "
            "admin if you don't have the client_id and client_secret.")
    storage = multistore_file.get_credential_storage(
        filename=os.path.abspath(creds_cache_file),
        client_id=client_id,
        user_agent=user_agent,
        scope=scopes)
    credentials = storage.get()
    if credentials is not None:
        try:
            credentials.refresh(httplib2.Http())
        except oauth2_client.AccessTokenRefreshError:
            pass
        if not credentials.invalid:
            return credentials
    return _RunAuthFlow(storage, client_id, client_secret, user_agent, scopes)


def CreateCredentials(acloud_config, scopes):
    """Create credentials.

    Args:
        acloud_config: An AcloudConfig object.
        scopes: A string representing for scopes, separted by space,
            like "SCOPE_1 SCOPE_2 SCOPE_3"

    Returns:
        An oauth2client.OAuth2Credentials instance.
    """
    if acloud_config.service_account_private_key_path:
        return _CreateOauthServiceAccountCreds(
            acloud_config.service_account_name,
            acloud_config.service_account_private_key_path,
            scopes=scopes)

    creds_cache_file = os.path.join(HOME_FOLDER,
                                    acloud_config.creds_cache_file)
    return _CreateOauthUserCreds(
        creds_cache_file=creds_cache_file,
        client_id=acloud_config.client_id,
        client_secret=acloud_config.client_secret,
        user_agent=acloud_config.user_agent,
        scopes=scopes)