# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010-2012 OpenStack LLC
#
# 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.

"""
TOKEN-BASED AUTH MIDDLEWARE

This WSGI component:

* Verifies that incoming client requests have valid tokens by validating
  tokens with the auth service.
* Rejects unauthenticated requests UNLESS it is in 'delay_auth_decision'
  mode, which means the final decision is delegated to the downstream WSGI
  component (usually the OpenStack service)
* Collects and forwards identity information based on a valid token
  such as user name, tenant, etc

Refer to: http://keystone.openstack.org/middlewarearchitecture.html

HEADERS
-------

* Headers starting with HTTP\_ is a standard http header
* Headers starting with HTTP_X is an extended http header

Coming in from initial call from client or customer
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

HTTP_X_AUTH_TOKEN
    The client token being passed in.

HTTP_X_STORAGE_TOKEN
    The client token being passed in (legacy Rackspace use) to support
    swift/cloud files

Used for communication between components
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

WWW-Authenticate
    HTTP header returned to a user indicating which endpoint to use
    to retrieve a new token

What we add to the request for use by the OpenStack service
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

HTTP_X_IDENTITY_STATUS
    'Confirmed' or 'Invalid'
    The underlying service will only see a value of 'Invalid' if the Middleware
    is configured to run in 'delay_auth_decision' mode

HTTP_X_TENANT_ID
    Identity service managed unique identifier, string

HTTP_X_TENANT_NAME
    Unique tenant identifier, string

HTTP_X_USER_ID
    Identity-service managed unique identifier, string

HTTP_X_USER_NAME
    Unique user identifier, string

HTTP_X_ROLES
    Comma delimited list of case-sensitive Roles

HTTP_X_SERVICE_CATALOG
    json encoded keystone service catalog (optional).

HTTP_X_TENANT
    *Deprecated* in favor of HTTP_X_TENANT_ID and HTTP_X_TENANT_NAME
    Keystone-assigned unique identifier, deprecated

HTTP_X_USER
    *Deprecated* in favor of HTTP_X_USER_ID and HTTP_X_USER_NAME
    Unique user name, string

HTTP_X_ROLE
    *Deprecated* in favor of HTTP_X_ROLES
    This is being renamed, and the new header contains the same data.

"""

import datetime
import httplib
import json
import logging
import os
import stat
import subprocess
import time
import webob
import webob.exc

from keystone.openstack.common import jsonutils
from keystone.common import cms
from keystone.common import utils
from keystone.openstack.common import timeutils

CONF = None
try:
    from openstack.common import cfg
    CONF = cfg.CONF
except ImportError:
    # cfg is not a library yet, try application copies
    for app in 'nova', 'glance', 'quantum', 'cinder':
        try:
            cfg = __import__('%s.openstack.common.cfg' % app,
                             fromlist=['%s.openstack.common' % app])
            # test which application middleware is running in
            if 'config_file' in cfg.CONF:
                CONF = cfg.CONF
                break
        except ImportError:
            pass
if not CONF:
    from keystone.openstack.common import cfg
    CONF = cfg.CONF
LOG = logging.getLogger(__name__)

# alternative middleware configuration in the main application's
# configuration file e.g. in nova.conf
# [keystone_authtoken]
# auth_host = 127.0.0.1
# auth_port = 35357
# auth_protocol = http
# admin_tenant_name = admin
# admin_user = admin
# admin_password = badpassword
opts = [
    cfg.StrOpt('auth_admin_prefix', default=''),
    cfg.StrOpt('auth_host', default='127.0.0.1'),
    cfg.IntOpt('auth_port', default=35357),
    cfg.StrOpt('auth_protocol', default='https'),
    cfg.StrOpt('auth_uri', default=None),
    cfg.BoolOpt('delay_auth_decision', default=False),
    cfg.StrOpt('admin_token'),
    cfg.StrOpt('admin_user'),
    cfg.StrOpt('admin_password'),
    cfg.StrOpt('admin_tenant_name', default='admin'),
    cfg.StrOpt('certfile'),
    cfg.StrOpt('keyfile'),
    cfg.StrOpt('signing_dir'),
    cfg.ListOpt('memcache_servers'),
    cfg.IntOpt('token_cache_time', default=300),
]
CONF.register_opts(opts, group='keystone_authtoken')


class InvalidUserToken(Exception):
    pass


class ServiceError(Exception):
    pass


class ConfigurationError(Exception):
    pass


class AuthProtocol(object):
    """Auth Middleware that handles authenticating client calls."""

    def __init__(self, app, conf):
        LOG.info('Starting keystone auth_token middleware')
        self.conf = conf
        self.app = app

        # delay_auth_decision means we still allow unauthenticated requests
        # through and we let the downstream service make the final decision
        self.delay_auth_decision = (self._conf_get('delay_auth_decision') in
                                    (True, 'true', 't', '1', 'on', 'yes', 'y'))

        # where to find the auth service (we use this to validate tokens)
        self.auth_host = self._conf_get('auth_host')
        self.auth_port = int(self._conf_get('auth_port'))
        self.auth_protocol = self._conf_get('auth_protocol')
        if self.auth_protocol == 'http':
            self.http_client_class = httplib.HTTPConnection
        else:
            self.http_client_class = httplib.HTTPSConnection

        self.auth_admin_prefix = self._conf_get('auth_admin_prefix')
        self.auth_uri = self._conf_get('auth_uri')
        if self.auth_uri is None:
            self.auth_uri = '%s://%s:%s' % (self.auth_protocol,
                                            self.auth_host,
                                            self.auth_port)

        # SSL
        self.cert_file = self._conf_get('certfile')
        self.key_file = self._conf_get('keyfile')

        #signing
        self.signing_dirname = self._conf_get('signing_dir')
        if self.signing_dirname is None:
            self.signing_dirname = '%s/keystone-signing' % os.environ['HOME']
        LOG.info('Using %s as cache directory for signing certificate' %
                 self.signing_dirname)
        if (os.path.exists(self.signing_dirname) and
                not os.access(self.signing_dirname, os.W_OK)):
                raise ConfigurationError("unable to access signing dir %s" %
                                         self.signing_dirname)

        if not os.path.exists(self.signing_dirname):
            os.makedirs(self.signing_dirname)
        #will throw IOError  if it cannot change permissions
        os.chmod(self.signing_dirname, stat.S_IRWXU)

        val = '%s/signing_cert.pem' % self.signing_dirname
        self.signing_cert_file_name = val
        val = '%s/cacert.pem' % self.signing_dirname
        self.ca_file_name = val
        val = '%s/revoked.pem' % self.signing_dirname
        self.revoked_file_name = val

        # Credentials used to verify this component with the Auth service since
        # validating tokens is a privileged call
        self.admin_token = self._conf_get('admin_token')
        self.admin_user = self._conf_get('admin_user')
        self.admin_password = self._conf_get('admin_password')
        self.admin_tenant_name = self._conf_get('admin_tenant_name')

        # Token caching via memcache
        self._cache = None
        self._iso8601 = None
        memcache_servers = self._conf_get('memcache_servers')
        # By default the token will be cached for 5 minutes
        self.token_cache_time = int(self._conf_get('token_cache_time'))
        self._token_revocation_list = None
        self._token_revocation_list_fetched_time = None
        self.token_revocation_list_cache_timeout = \
            datetime.timedelta(seconds=0)
        if memcache_servers:
            try:
                import memcache
                import iso8601
                LOG.info('Using memcache for caching token')
                self._cache = memcache.Client(memcache_servers.split(','))
                self._iso8601 = iso8601
            except ImportError as e:
                LOG.warn('disabled caching due to missing libraries %s', e)

    def _conf_get(self, name):
        # try config from paste-deploy first
        if name in self.conf:
            return self.conf[name]
        else:
            return CONF.keystone_authtoken[name]

    def __call__(self, env, start_response):
        """Handle incoming request.

        Authenticate send downstream on success. Reject request if
        we can't authenticate.

        """
        LOG.debug('Authenticating user token')
        try:
            self._remove_auth_headers(env)
            user_token = self._get_user_token_from_header(env)
            token_info = self._validate_user_token(user_token)
            user_headers = self._build_user_headers(token_info)
            self._add_headers(env, user_headers)
            return self.app(env, start_response)

        except InvalidUserToken:
            if self.delay_auth_decision:
                LOG.info('Invalid user token - deferring reject downstream')
                self._add_headers(env, {'X-Identity-Status': 'Invalid'})
                return self.app(env, start_response)
            else:
                LOG.info('Invalid user token - rejecting request')
                return self._reject_request(env, start_response)

        except ServiceError, e:
            LOG.critical('Unable to obtain admin token: %s' % e)
            resp = webob.exc.HTTPServiceUnavailable()
            return resp(env, start_response)

    def _remove_auth_headers(self, env):
        """Remove headers so a user can't fake authentication.

        :param env: wsgi request environment

        """
        auth_headers = (
            'X-Identity-Status',
            'X-Tenant-Id',
            'X-Tenant-Name',
            'X-User-Id',
            'X-User-Name',
            'X-Roles',
            'X-Service-Catalog',
            # Deprecated
            'X-User',
            'X-Tenant',
            'X-Role',
        )
        LOG.debug('Removing headers from request environment: %s' %
                  ','.join(auth_headers))
        self._remove_headers(env, auth_headers)

    def _get_user_token_from_header(self, env):
        """Get token id from request.

        :param env: wsgi request environment
        :return token id
        :raises InvalidUserToken if no token is provided in request

        """
        token = self._get_header(env, 'X-Auth-Token',
                                 self._get_header(env, 'X-Storage-Token'))
        if token:
            return token
        else:
            LOG.warn("Unable to find authentication token in headers: %s", env)
            raise InvalidUserToken('Unable to find token in headers')

    def _reject_request(self, env, start_response):
        """Redirect client to auth server.

        :param env: wsgi request environment
        :param start_response: wsgi response callback
        :returns HTTPUnauthorized http response

        """
        headers = [('WWW-Authenticate', 'Keystone uri=\'%s\'' % self.auth_uri)]
        resp = webob.exc.HTTPUnauthorized('Authentication required', headers)
        return resp(env, start_response)

    def get_admin_token(self):
        """Return admin token, possibly fetching a new one.

        :return admin token id
        :raise ServiceError when unable to retrieve token from keystone

        """
        if not self.admin_token:
            self.admin_token = self._request_admin_token()

        return self.admin_token

    def _get_http_connection(self):
        if self.auth_protocol == 'http':
            return self.http_client_class(self.auth_host, self.auth_port)
        else:
            return self.http_client_class(self.auth_host,
                                          self.auth_port,
                                          self.key_file,
                                          self.cert_file)

    def _http_request(self, method, path):
        """HTTP request helper used to make unspecified content type requests.

        :param method: http method
        :param path: relative request url
        :return (http response object)
        :raise ServerError when unable to communicate with keystone

        """
        conn = self._get_http_connection()

        try:
            conn.request(method, path)
            response = conn.getresponse()
            body = response.read()
        except Exception, e:
            LOG.error('HTTP connection exception: %s' % e)
            raise ServiceError('Unable to communicate with keystone')
        finally:
            conn.close()

        return response, body

    def _json_request(self, method, path, body=None, additional_headers=None):
        """HTTP request helper used to make json requests.

        :param method: http method
        :param path: relative request url
        :param body: dict to encode to json as request body. Optional.
        :param additional_headers: dict of additional headers to send with
                                   http request. Optional.
        :return (http response object, response body parsed as json)
        :raise ServerError when unable to communicate with keystone

        """
        conn = self._get_http_connection()

        kwargs = {
            'headers': {
                'Content-type': 'application/json',
                'Accept': 'application/json',
            },
        }

        if additional_headers:
            kwargs['headers'].update(additional_headers)

        if body:
            kwargs['body'] = jsonutils.dumps(body)

        full_path = self.auth_admin_prefix + path
        try:
            conn.request(method, full_path, **kwargs)
            response = conn.getresponse()
            body = response.read()
        except Exception, e:
            LOG.error('HTTP connection exception: %s' % e)
            raise ServiceError('Unable to communicate with keystone')
        finally:
            conn.close()

        try:
            data = jsonutils.loads(body)
        except ValueError:
            LOG.debug('Keystone did not return json-encoded body')
            data = {}

        return response, data

    def _request_admin_token(self):
        """Retrieve new token as admin user from keystone.

        :return token id upon success
        :raises ServerError when unable to communicate with keystone

        """
        params = {
            'auth': {
                'passwordCredentials': {
                    'username': self.admin_user,
                    'password': self.admin_password,
                },
                'tenantName': self.admin_tenant_name,
            }
        }

        response, data = self._json_request('POST',
                                            '/v2.0/tokens',
                                            body=params)

        try:
            token = data['access']['token']['id']
            assert token
            return token
        except (AssertionError, KeyError):
            LOG.warn("Unexpected response from keystone service: %s", data)
            raise ServiceError('invalid json response')

    def _validate_user_token(self, user_token, retry=True):
        """Authenticate user using PKI

        :param user_token: user's token id
        :param retry: Ignored, as it is not longer relevant
        :return uncrypted body of the token if the token is valid
        :raise InvalidUserToken if token is rejected
        :no longer raises ServiceError since it no longer makes RPC

        """
        try:
            cached = self._cache_get(user_token)
            if cached:
                return cached
            if (len(user_token) > cms.UUID_TOKEN_LENGTH):
                verified = self.verify_signed_token(user_token)
                data = json.loads(verified)
            else:
                data = self.verify_uuid_token(user_token, retry)
            self._cache_put(user_token, data)
            return data
        except Exception as e:
            LOG.debug('Token validation failure.', exc_info=True)
            self._cache_store_invalid(user_token)
            LOG.warn("Authorization failed for token %s", user_token)
            raise InvalidUserToken('Token authorization failed')

    def _build_user_headers(self, token_info):
        """Convert token object into headers.

        Build headers that represent authenticated user:
         * X_IDENTITY_STATUS: Confirmed or Invalid
         * X_TENANT_ID: id of tenant if tenant is present
         * X_TENANT_NAME: name of tenant if tenant is present
         * X_USER_ID: id of user
         * X_USER_NAME: name of user
         * X_ROLES: list of roles
         * X_SERVICE_CATALOG: service catalog

        Additional (deprecated) headers include:
         * X_USER: name of user
         * X_TENANT: For legacy compatibility before we had ID and Name
         * X_ROLE: list of roles

        :param token_info: token object returned by keystone on authentication
        :raise InvalidUserToken when unable to parse token object

        """
        user = token_info['access']['user']
        token = token_info['access']['token']
        roles = ','.join([role['name'] for role in user.get('roles', [])])

        def get_tenant_info():
            """Returns a (tenant_id, tenant_name) tuple from context."""
            def essex():
                """Essex puts the tenant ID and name on the token."""
                return (token['tenant']['id'], token['tenant']['name'])

            def pre_diablo():
                """Pre-diablo, Keystone only provided tenantId."""
                return (token['tenantId'], token['tenantId'])

            def default_tenant():
                """Assume the user's default tenant."""
                return (user['tenantId'], user['tenantName'])

            for method in [essex, pre_diablo, default_tenant]:
                try:
                    return method()
                except KeyError:
                    pass

            raise InvalidUserToken('Unable to determine tenancy.')

        tenant_id, tenant_name = get_tenant_info()

        user_id = user['id']
        user_name = user['name']

        rval = {
            'X-Identity-Status': 'Confirmed',
            'X-Tenant-Id': tenant_id,
            'X-Tenant-Name': tenant_name,
            'X-User-Id': user_id,
            'X-User-Name': user_name,
            'X-Roles': roles,
            # Deprecated
            'X-User': user_name,
            'X-Tenant': tenant_name,
            'X-Role': roles,
        }

        try:
            catalog = token_info['access']['serviceCatalog']
            rval['X-Service-Catalog'] = jsonutils.dumps(catalog)
        except KeyError:
            pass

        return rval

    def _header_to_env_var(self, key):
        """Convert header to wsgi env variable.

        :param key: http header name (ex. 'X-Auth-Token')
        :return wsgi env variable name (ex. 'HTTP_X_AUTH_TOKEN')

        """
        return 'HTTP_%s' % key.replace('-', '_').upper()

    def _add_headers(self, env, headers):
        """Add http headers to environment."""
        for (k, v) in headers.iteritems():
            env_key = self._header_to_env_var(k)
            env[env_key] = v

    def _remove_headers(self, env, keys):
        """Remove http headers from environment."""
        for k in keys:
            env_key = self._header_to_env_var(k)
            try:
                del env[env_key]
            except KeyError:
                pass

    def _get_header(self, env, key, default=None):
        """Get http header from environment."""
        env_key = self._header_to_env_var(key)
        return env.get(env_key, default)

    def _cache_get(self, token):
        """Return token information from cache.

        If token is invalid raise InvalidUserToken
        return token only if fresh (not expired).
        """
        if self._cache and token:
            key = 'tokens/%s' % token
            cached = self._cache.get(key)
            if cached == 'invalid':
                LOG.debug('Cached Token %s is marked unauthorized', token)
                raise InvalidUserToken('Token authorization failed')
            if cached:
                data, expires = cached
                if time.time() < float(expires):
                    LOG.debug('Returning cached token %s', token)
                    return data
                else:
                    LOG.debug('Cached Token %s seems expired', token)

    def _cache_put(self, token, data):
        """Put token data into the cache.

        Stores the parsed expire date in cache allowing
        quick check of token freshness on retrieval.
        """
        if self._cache and data:
            key = 'tokens/%s' % token
            if 'token' in data.get('access', {}):
                timestamp = data['access']['token']['expires']
                expires = self._iso8601.parse_date(timestamp).strftime('%s')
            else:
                LOG.error('invalid token format')
                return
            LOG.debug('Storing %s token in memcache', token)
            self._cache.set(key,
                            (data, expires),
                            time=self.token_cache_time)

    def _cache_store_invalid(self, token):
        """Store invalid token in cache."""
        if self._cache:
            key = 'tokens/%s' % token
            LOG.debug('Marking token %s as unauthorized in memcache', token)
            self._cache.set(key,
                            'invalid',
                            time=self.token_cache_time)

    def cert_file_missing(self, called_proc_err, file_name):
        return (called_proc_err.output.find(file_name)
                and not os.path.exists(file_name))

    def verify_uuid_token(self, user_token, retry=True):
        """Authenticate user token with keystone.

        :param user_token: user's token id
        :param retry: flag that forces the middleware to retry
                      user authentication when an indeterminate
                      response is received. Optional.
        :return token object received from keystone on success
        :raise InvalidUserToken if token is rejected
        :raise ServiceError if unable to authenticate token

        """

        headers = {'X-Auth-Token': self.get_admin_token()}
        response, data = self._json_request('GET',
                                            '/v2.0/tokens/%s' % user_token,
                                            additional_headers=headers)

        if response.status == 200:
            self._cache_put(user_token, data)
            return data
        if response.status == 404:
            # FIXME(ja): I'm assuming the 404 status means that user_token is
            #            invalid - not that the admin_token is invalid
            self._cache_store_invalid(user_token)
            LOG.warn("Authorization failed for token %s", user_token)
            raise InvalidUserToken('Token authorization failed')
        if response.status == 401:
            LOG.info('Keystone rejected admin token %s, resetting', headers)
            self.admin_token = None
        else:
            LOG.error('Bad response code while validating token: %s' %
                      response.status)
        if retry:
            LOG.info('Retrying validation')
            return self._validate_user_token(user_token, False)
        else:
            LOG.warn("Invalid user token: %s. Keystone response: %s.",
                     user_token, data)

            raise InvalidUserToken()

    def is_signed_token_revoked(self, signed_text):
        """Indicate whether the token appears in the revocation list."""
        revocation_list = self.token_revocation_list
        revoked_tokens = revocation_list.get('revoked', [])
        if not revoked_tokens:
            return
        revoked_ids = (x['id'] for x in revoked_tokens)
        token_id = utils.hash_signed_token(signed_text)
        for revoked_id in revoked_ids:
            if token_id == revoked_id:
                LOG.debug('Token %s is marked as having been revoked',
                          token_id)
                return True
        return False

    def cms_verify(self, data):
        """Verifies the signature of the provided data's IAW CMS syntax.

        If either of the certificate files are missing, fetch them and
        retry.
        """
        while True:
            try:
                output = cms.cms_verify(data, self.signing_cert_file_name,
                                        self.ca_file_name)
            except subprocess.CalledProcessError as err:
                if self.cert_file_missing(err, self.signing_cert_file_name):
                    self.fetch_signing_cert()
                    continue
                if self.cert_file_missing(err, self.ca_file_name):
                    self.fetch_ca_cert()
                    continue
                raise err
            return output

    def verify_signed_token(self, signed_text):
        """Check that the token is unrevoked and has a valid signature."""
        if self.is_signed_token_revoked(signed_text):
            raise InvalidUserToken('Token has been revoked')

        formatted = cms.token_to_cms(signed_text)
        return self.cms_verify(formatted)

    @property
    def token_revocation_list_fetched_time(self):
        if not self._token_revocation_list_fetched_time:
            # If the fetched list has been written to disk, use its
            # modification time.
            if os.path.exists(self.revoked_file_name):
                mtime = os.path.getmtime(self.revoked_file_name)
                fetched_time = datetime.datetime.fromtimestamp(mtime)
            # Otherwise the list will need to be fetched.
            else:
                fetched_time = datetime.datetime.min
            self._token_revocation_list_fetched_time = fetched_time
        return self._token_revocation_list_fetched_time

    @token_revocation_list_fetched_time.setter
    def token_revocation_list_fetched_time(self, value):
        self._token_revocation_list_fetched_time = value

    @property
    def token_revocation_list(self):
        timeout = self.token_revocation_list_fetched_time +\
            self.token_revocation_list_cache_timeout
        list_is_current = timeutils.utcnow() < timeout
        if list_is_current:
            # Load the list from disk if required
            if not self._token_revocation_list:
                with open(self.revoked_file_name, 'r') as f:
                    self._token_revocation_list = jsonutils.loads(f.read())
        else:
            self.token_revocation_list = self.fetch_revocation_list()
        return self._token_revocation_list

    @token_revocation_list.setter
    def token_revocation_list(self, value):
        """Save a revocation list to memory and to disk.

        :param value: A json-encoded revocation list

        """
        self._token_revocation_list = jsonutils.loads(value)
        self.token_revocation_list_fetched_time = timeutils.utcnow()
        with open(self.revoked_file_name, 'w') as f:
            f.write(value)

    def fetch_revocation_list(self):
        response, data = self._http_request('GET', '/v2.0/tokens/revoked')
        if response.status != 200:
            raise ServiceError('Unable to fetch token revocation list.')
        return self.cms_verify(data)

    def fetch_signing_cert(self):
        response, data = self._http_request('GET',
                                            '/v2.0/certificates/signing')
        try:
            #todo check response
            certfile = open(self.signing_cert_file_name, 'w')
            certfile.write(data)
            certfile.close()
        except (AssertionError, KeyError):
            LOG.warn("Unexpected response from keystone service: %s", data)
            raise ServiceError('invalid json response')

    def fetch_ca_cert(self):
        response, data = self._http_request('GET',
                                            '/v2.0/certificates/ca')
        try:
            #todo check response
            certfile = open(self.ca_file_name, 'w')
            certfile.write(data)
            certfile.close()
        except (AssertionError, KeyError):
            LOG.warn("Unexpected response from keystone service: %s", data)
            raise ServiceError('invalid json response')


def filter_factory(global_conf, **local_conf):
    """Returns a WSGI filter app for use with paste.deploy."""
    conf = global_conf.copy()
    conf.update(local_conf)

    def auth_filter(app):
        return AuthProtocol(app, conf)
    return auth_filter


def app_factory(global_conf, **local_conf):
    conf = global_conf.copy()
    conf.update(local_conf)
    return AuthProtocol(None, conf)
