# Copyright 2013 OpenStack Foundation
#
#    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 datetime
import sys

from keystone.common import utils
from keystoneclient.common import cms
from oslo_config import cfg
from oslo_log import log
from oslo_serialization import jsonutils
from oslo_utils import timeutils
import six

from keystone.common import controller
from keystone.common import dependency
from keystone.common import wsgi
from keystone import exception
from keystone.i18n import _
from keystone.models import token_model
from keystone.token import provider


CONF = cfg.CONF
LOG = log.getLogger(__name__)


class ExternalAuthNotApplicable(Exception):
    """External authentication is not applicable."""

    pass


@dependency.requires('assignment_api', 'catalog_api', 'identity_api',
                     'resource_api', 'role_api', 'token_provider_api',
                     'trust_api')
class Auth(controller.V2Controller):

    @controller.v2_deprecated
    def ca_cert(self, context, auth=None):
        with open(CONF.signing.ca_certs, 'r') as ca_file:
            data = ca_file.read()
        return data

    @controller.v2_deprecated
    def signing_cert(self, context, auth=None):
        with open(CONF.signing.certfile, 'r') as cert_file:
            data = cert_file.read()
        return data

    @controller.v2_auth_deprecated
    def authenticate(self, context, auth=None):
        """Authenticate credentials and return a token.

        Accept auth as a dict that looks like::

            {
                "auth":{
                    "passwordCredentials":{
                        "username":"test_user",
                        "password":"mypass"
                    },
                    "tenantName":"customer-x"
                }
            }

        In this case, tenant is optional, if not provided the token will be
        considered "unscoped" and can later be used to get a scoped token.

        Alternatively, this call accepts auth with only a token and tenant
        that will return a token that is scoped to that tenant.
        """
        if auth is None:
            raise exception.ValidationError(attribute='auth',
                                            target='request body')

        if "token" in auth:
            # Try to authenticate using a token
            auth_info = self._authenticate_token(
                context, auth)
        else:
            # Try external authentication
            try:
                auth_info = self._authenticate_external(
                    context, auth)
            except ExternalAuthNotApplicable:
                # Try local authentication
                auth_info = self._authenticate_local(
                    context, auth)

        user_ref, tenant_ref, metadata_ref, expiry, bind, audit_id = auth_info
        # Validate that the auth info is valid and nothing is disabled
        try:
            self.identity_api.assert_user_enabled(
                user_id=user_ref['id'], user=user_ref)
            if tenant_ref:
                self.resource_api.assert_project_enabled(
                    project_id=tenant_ref['id'], project=tenant_ref)
        except AssertionError as e:
            six.reraise(exception.Unauthorized, exception.Unauthorized(e),
                        sys.exc_info()[2])
        # NOTE(morganfainberg): Make sure the data is in correct form since it
        # might be consumed external to Keystone and this is a v2.0 controller.
        # The user_ref is encoded into the auth_token_data which is returned as
        # part of the token data. The token provider doesn't care about the
        # format.
        user_ref = self.v3_to_v2_user(user_ref)
        if tenant_ref:
            tenant_ref = self.v3_to_v2_project(tenant_ref)

        auth_token_data = self._get_auth_token_data(user_ref,
                                                    tenant_ref,
                                                    metadata_ref,
                                                    expiry,
                                                    audit_id)

        if tenant_ref:
            catalog_ref = self.catalog_api.get_catalog(
                user_ref['id'], tenant_ref['id'])
        else:
            catalog_ref = {}

        auth_token_data['id'] = 'placeholder'
        if bind:
            auth_token_data['bind'] = bind

        roles_ref = []
        for role_id in metadata_ref.get('roles', []):
            role_ref = self.role_api.get_role(role_id)
            roles_ref.append(dict(name=role_ref['name']))

        (token_id, token_data) = self.token_provider_api.issue_v2_token(
            auth_token_data, roles_ref=roles_ref, catalog_ref=catalog_ref)

        # NOTE(wanghong): We consume a trust use only when we are using trusts
        # and have successfully issued a token.
        if CONF.trust.enabled and 'trust_id' in auth:
            self.trust_api.consume_use(auth['trust_id'])

        return token_data

    def _restrict_scope(self, token_model_ref):
        # A trust token cannot be used to get another token
        if token_model_ref.trust_scoped:
            raise exception.Forbidden()
        if not CONF.token.allow_rescope_scoped_token:
            # Do not allow conversion from scoped tokens.
            if token_model_ref.project_scoped or token_model_ref.domain_scoped:
                raise exception.Forbidden(action=_("rescope a scoped token"))

    def _authenticate_token(self, context, auth):
        """Try to authenticate using an already existing token.

        Returns auth_token_data, (user_ref, tenant_ref, metadata_ref)
        """
        if 'token' not in auth:
            raise exception.ValidationError(
                attribute='token', target='auth')

        if "id" not in auth['token']:
            raise exception.ValidationError(
                attribute="id", target="token")

        old_token = auth['token']['id']
        if len(old_token) > CONF.max_token_size:
            raise exception.ValidationSizeError(attribute='token',
                                                size=CONF.max_token_size)

        try:
            token_model_ref = token_model.KeystoneToken(
                token_id=old_token,
                token_data=self.token_provider_api.validate_token(old_token))
        except exception.NotFound as e:
            raise exception.Unauthorized(e)

        wsgi.validate_token_bind(context, token_model_ref)

        self._restrict_scope(token_model_ref)
        user_id = token_model_ref.user_id
        tenant_id = self._get_project_id_from_auth(auth)

        if not CONF.trust.enabled and 'trust_id' in auth:
            raise exception.Forbidden('Trusts are disabled.')
        elif CONF.trust.enabled and 'trust_id' in auth:
            try:
                trust_ref = self.trust_api.get_trust(auth['trust_id'])
            except exception.TrustNotFound:
                raise exception.Forbidden()
            if user_id != trust_ref['trustee_user_id']:
                raise exception.Forbidden()
            if (trust_ref['project_id'] and
                    tenant_id != trust_ref['project_id']):
                raise exception.Forbidden()
            if ('expires' in trust_ref) and (trust_ref['expires']):
                expiry = trust_ref['expires']
                if expiry < timeutils.parse_isotime(utils.isotime()):
                    raise exception.Forbidden()
            user_id = trust_ref['trustor_user_id']
            trustor_user_ref = self.identity_api.get_user(
                trust_ref['trustor_user_id'])
            if not trustor_user_ref['enabled']:
                raise exception.Forbidden()
            trustee_user_ref = self.identity_api.get_user(
                trust_ref['trustee_user_id'])
            if not trustee_user_ref['enabled']:
                raise exception.Forbidden()

            if trust_ref['impersonation'] is True:
                current_user_ref = trustor_user_ref
            else:
                current_user_ref = trustee_user_ref

        else:
            current_user_ref = self.identity_api.get_user(user_id)

        metadata_ref = {}
        tenant_ref, metadata_ref['roles'] = self._get_project_roles_and_ref(
            user_id, tenant_id)

        expiry = token_model_ref.expires
        if CONF.trust.enabled and 'trust_id' in auth:
            trust_id = auth['trust_id']
            trust_roles = []
            for role in trust_ref['roles']:
                if 'roles' not in metadata_ref:
                    raise exception.Forbidden()
                if role['id'] in metadata_ref['roles']:
                    trust_roles.append(role['id'])
                else:
                    raise exception.Forbidden()
            if 'expiry' in trust_ref and trust_ref['expiry']:
                trust_expiry = timeutils.parse_isotime(trust_ref['expiry'])
                if trust_expiry < expiry:
                    expiry = trust_expiry
            metadata_ref['roles'] = trust_roles
            metadata_ref['trustee_user_id'] = trust_ref['trustee_user_id']
            metadata_ref['trust_id'] = trust_id

        bind = token_model_ref.bind
        audit_id = token_model_ref.audit_chain_id

        return (current_user_ref, tenant_ref, metadata_ref, expiry, bind,
                audit_id)

    def _authenticate_local(self, context, auth):
        """Try to authenticate against the identity backend.

        Returns auth_token_data, (user_ref, tenant_ref, metadata_ref)
        """
        if 'passwordCredentials' not in auth:
            raise exception.ValidationError(
                attribute='passwordCredentials', target='auth')

        if "password" not in auth['passwordCredentials']:
            raise exception.ValidationError(
                attribute='password', target='passwordCredentials')

        password = auth['passwordCredentials']['password']
        if password and len(password) > CONF.identity.max_password_length:
            raise exception.ValidationSizeError(
                attribute='password', size=CONF.identity.max_password_length)

        if (not auth['passwordCredentials'].get("userId") and
                not auth['passwordCredentials'].get("username")):
            raise exception.ValidationError(
                attribute='username or userId',
                target='passwordCredentials')

        user_id = auth['passwordCredentials'].get('userId')
        if user_id and len(user_id) > CONF.max_param_size:
            raise exception.ValidationSizeError(attribute='userId',
                                                size=CONF.max_param_size)

        username = auth['passwordCredentials'].get('username', '')

        if username:
            if len(username) > CONF.max_param_size:
                raise exception.ValidationSizeError(attribute='username',
                                                    size=CONF.max_param_size)
            try:
                user_ref = self.identity_api.get_user_by_name(
                    username, CONF.identity.default_domain_id)
                user_id = user_ref['id']
            except exception.UserNotFound as e:
                raise exception.Unauthorized(e)

        try:
            user_ref = self.identity_api.authenticate(
                context,
                user_id=user_id,
                password=password)
        except AssertionError as e:
            raise exception.Unauthorized(e.args[0])

        metadata_ref = {}
        tenant_id = self._get_project_id_from_auth(auth)
        tenant_ref, metadata_ref['roles'] = self._get_project_roles_and_ref(
            user_id, tenant_id)

        expiry = provider.default_expire_time()
        bind = None
        audit_id = None
        return (user_ref, tenant_ref, metadata_ref, expiry, bind, audit_id)

    def _authenticate_external(self, context, auth):
        """Try to authenticate an external user via REMOTE_USER variable.

        Returns auth_token_data, (user_ref, tenant_ref, metadata_ref)
        """
        environment = context.get('environment', {})
        if not environment.get('REMOTE_USER'):
            raise ExternalAuthNotApplicable()

        username = environment['REMOTE_USER']
        try:
            user_ref = self.identity_api.get_user_by_name(
                username, CONF.identity.default_domain_id)
            user_id = user_ref['id']
        except exception.UserNotFound as e:
            raise exception.Unauthorized(e)

        metadata_ref = {}
        tenant_id = self._get_project_id_from_auth(auth)
        tenant_ref, metadata_ref['roles'] = self._get_project_roles_and_ref(
            user_id, tenant_id)

        expiry = provider.default_expire_time()
        bind = None
        if ('kerberos' in CONF.token.bind and
                environment.get('AUTH_TYPE', '').lower() == 'negotiate'):
            bind = {'kerberos': username}
        audit_id = None

        return (user_ref, tenant_ref, metadata_ref, expiry, bind, audit_id)

    def _get_auth_token_data(self, user, tenant, metadata, expiry, audit_id):
        return dict(user=user,
                    tenant=tenant,
                    metadata=metadata,
                    expires=expiry,
                    parent_audit_id=audit_id)

    def _get_project_id_from_auth(self, auth):
        """Extract tenant information from auth dict.

        Returns a valid tenant_id if it exists, or None if not specified.
        """
        tenant_id = auth.get('tenantId')
        if tenant_id and len(tenant_id) > CONF.max_param_size:
            raise exception.ValidationSizeError(attribute='tenantId',
                                                size=CONF.max_param_size)

        tenant_name = auth.get('tenantName')
        if tenant_name and len(tenant_name) > CONF.max_param_size:
            raise exception.ValidationSizeError(attribute='tenantName',
                                                size=CONF.max_param_size)

        if tenant_name:
            if (CONF.resource.project_name_url_safe == 'strict' and
                    utils.is_not_url_safe(tenant_name)):
                msg = _('Tenant name cannot contain reserved characters.')
                raise exception.Unauthorized(message=msg)
            try:
                tenant_ref = self.resource_api.get_project_by_name(
                    tenant_name, CONF.identity.default_domain_id)
                tenant_id = tenant_ref['id']
            except exception.ProjectNotFound as e:
                raise exception.Unauthorized(e)
        return tenant_id

    def _get_project_roles_and_ref(self, user_id, tenant_id):
        """Returns the project roles for this user, and the project ref."""
        tenant_ref = None
        role_list = []
        if tenant_id:
            try:
                tenant_ref = self.resource_api.get_project(tenant_id)
                role_list = self.assignment_api.get_roles_for_user_and_project(
                    user_id, tenant_id)
            except exception.ProjectNotFound:
                msg = _('Project ID not found: %(t_id)s') % {'t_id': tenant_id}
                raise exception.Unauthorized(msg)

            if not role_list:
                msg = _('User %(u_id)s is unauthorized for tenant %(t_id)s')
                msg = msg % {'u_id': user_id, 't_id': tenant_id}
                LOG.warning(msg)
                raise exception.Unauthorized(msg)

        return (tenant_ref, role_list)

    def _get_token_ref(self, token_id, belongs_to=None):
        """Returns a token if a valid one exists.

        Optionally, limited to a token owned by a specific tenant.

        """
        token_ref = token_model.KeystoneToken(
            token_id=token_id,
            token_data=self.token_provider_api.validate_token(token_id))
        if belongs_to:
            if not token_ref.project_scoped:
                raise exception.Unauthorized(
                    _('Token does not belong to specified tenant.'))
            if token_ref.project_id != belongs_to:
                raise exception.Unauthorized(
                    _('Token does not belong to specified tenant.'))
        return token_ref

    @controller.v2_deprecated
    @controller.protected()
    def validate_token_head(self, context, token_id):
        """Check that a token is valid.

        Optionally, also ensure that it is owned by a specific tenant.

        Identical to ``validate_token``, except does not return a response.

        The code in ``keystone.common.wsgi.render_response`` will remove
        the content body.

        """
        belongs_to = context['query_string'].get('belongsTo')
        return self.token_provider_api.validate_v2_token(token_id, belongs_to)

    @controller.v2_deprecated
    @controller.protected()
    def validate_token(self, context, token_id):
        """Check that a token is valid.

        Optionally, also ensure that it is owned by a specific tenant.

        Returns metadata about the token along any associated roles.

        """
        belongs_to = context['query_string'].get('belongsTo')
        # TODO(ayoung) validate against revocation API
        return self.token_provider_api.validate_v2_token(token_id, belongs_to)

    @controller.v2_deprecated
    def delete_token(self, context, token_id):
        """Delete a token, effectively invalidating it for authz."""
        # TODO(termie): this stuff should probably be moved to middleware
        self.assert_admin(context)
        self.token_provider_api.revoke_token(token_id)

    @controller.v2_deprecated
    @controller.protected()
    def revocation_list(self, context, auth=None):
        if not CONF.token.revoke_by_id:
            raise exception.Gone()
        tokens = self.token_provider_api.list_revoked_tokens()

        for t in tokens:
            expires = t['expires']
            if expires and isinstance(expires, datetime.datetime):
                t['expires'] = utils.isotime(expires)
        data = {'revoked': tokens}
        json_data = jsonutils.dumps(data)
        signed_text = cms.cms_sign_text(json_data,
                                        CONF.signing.certfile,
                                        CONF.signing.keyfile)

        return {'signed': signed_text}

    @controller.v2_deprecated
    def endpoints(self, context, token_id):
        """Return a list of endpoints available to the token."""
        self.assert_admin(context)

        token_ref = self._get_token_ref(token_id)

        catalog_ref = None
        if token_ref.project_id:
            catalog_ref = self.catalog_api.get_catalog(
                token_ref.user_id,
                token_ref.project_id)

        return Auth.format_endpoint_list(catalog_ref)

    @classmethod
    def format_endpoint_list(cls, catalog_ref):
        """Formats a list of endpoints according to Identity API v2.

        The v2.0 API wants an endpoint list to look like::

            {
                'endpoints': [
                    {
                        'id': $endpoint_id,
                        'name': $SERVICE[name],
                        'type': $SERVICE,
                        'tenantId': $tenant_id,
                        'region': $REGION,
                    }
                ],
                'endpoints_links': [],
            }

        """
        if not catalog_ref:
            return {}

        endpoints = []
        for region_name, region_ref in catalog_ref.items():
            for service_type, service_ref in region_ref.items():
                endpoints.append({
                    'id': service_ref.get('id'),
                    'name': service_ref.get('name'),
                    'type': service_type,
                    'region': region_name,
                    'publicURL': service_ref.get('publicURL'),
                    'internalURL': service_ref.get('internalURL'),
                    'adminURL': service_ref.get('adminURL'),
                })

        return {'endpoints': endpoints, 'endpoints_links': []}
