Synnefo

# Copyright 2011-2012 GRNET S.A. All rights reserved.

#

# Redistribution and use in source and binary forms, with or

# without modification, are permitted provided that the following

# conditions are met:

#

#   1. Redistributions of source code must retain the above

#      copyright notice, this list of conditions and the following

#      disclaimer.

#

#   2. Redistributions in binary form must reproduce the above

#      copyright notice, this list of conditions and the following

#      disclaimer in the documentation and/or other materials

#      provided with the distribution.

#

# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

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# The views and conclusions contained in the software and

# documentation are those of the authors and should not be

# interpreted as representing official policies, either expressed

# or implied, of GRNET S.A.

import sys

import os

import time

import uuid as uuidlib

import logging

import hashlib

import binascii

from base import DEFAULT_QUOTA, DEFAULT_VERSIONING, NotAllowedError, QuotaError, BaseBackend, \

    AccountExists, ContainerExists, AccountNotEmpty, ContainerNotEmpty, ItemNotExists, VersionNotExists

# Stripped-down version of the HashMap class found in tools.

class HashMap(list):

    def __init__(self, blocksize, blockhash):

        super(HashMap, self).__init__()

        self.blocksize = blocksize

        self.blockhash = blockhash

    def _hash_raw(self, v):

        h = hashlib.new(self.blockhash)

        h.update(v)

        return h.digest()

    def hash(self):

        if len(self) == 0:

            return self._hash_raw('')

        if len(self) == 1:

            return self.__getitem__(0)

        h = list(self)

        s = 2

        while s < len(h):

            s = s * 2

        h += [('\x00' * len(h[0]))] * (s - len(h))

        while len(h) > 1:

            h = [self._hash_raw(h[x] + h[x + 1]) for x in range(0, len(h), 2)]

        return h[0]

# Default modules and settings.

DEFAULT_DB_MODULE = 'pithos.backends.lib.sqlalchemy'

DEFAULT_DB_CONNECTION = 'sqlite:///backend.db'

DEFAULT_BLOCK_MODULE = 'pithos.backends.lib.hashfiler'

DEFAULT_BLOCK_PATH = 'data/'

DEFAULT_BLOCK_UMASK = 0o022

#DEFAULT_QUEUE_MODULE = 'pithos.backends.lib.rabbitmq'

#DEFAULT_QUEUE_HOSTS = '[amqp://guest:guest@localhost:5672]'

#DEFAULT_QUEUE_EXCHANGE = 'pithos'

QUEUE_MESSAGE_KEY_PREFIX = 'pithos.%s'

QUEUE_CLIENT_ID = 'pithos'

QUEUE_INSTANCE_ID = '1'

(CLUSTER_NORMAL, CLUSTER_HISTORY, CLUSTER_DELETED) = range(3)

inf = float('inf')

ULTIMATE_ANSWER = 42

logger = logging.getLogger(__name__)

def backend_method(func=None, autocommit=1):

    if func is None:

        def fn(func):

            return backend_method(func, autocommit)

        return fn

    if not autocommit:

        return func

    def fn(self, *args, **kw):

        self.wrapper.execute()

        try:

            self.messages = []

            ret = func(self, *args, **kw)

            for m in self.messages:

                self.queue.send(*m)

            self.wrapper.commit()

            return ret

        except:

            self.wrapper.rollback()

            raise

    return fn

class ModularBackend(BaseBackend):

    """A modular backend.

    Uses modules for SQL functions and storage.

    """

    def __init__(self, db_module=None, db_connection=None,

                 block_module=None, block_path=None, block_umask=None,

                 queue_module=None, queue_hosts=None,

                 queue_exchange=None):

        db_module = db_module or DEFAULT_DB_MODULE

        db_connection = db_connection or DEFAULT_DB_CONNECTION

        block_module = block_module or DEFAULT_BLOCK_MODULE

        block_path = block_path or DEFAULT_BLOCK_PATH

        block_umask = block_umask or DEFAULT_BLOCK_UMASK

        #queue_module = queue_module or DEFAULT_QUEUE_MODULE

        #queue_hosts = queue_hosts or DEFAULT_QUEUE_HOSTS

        #queue_exchange = queue_exchange or DEFAULT_QUEUE_EXCHANGE

        self.hash_algorithm = 'sha256'

        self.block_size = 4 * 1024 * 1024  # 4MB

        self.default_policy = {'quota': DEFAULT_QUOTA,

                               'versioning': DEFAULT_VERSIONING}

        def load_module(m):

            __import__(m)

            return sys.modules[m]

        self.db_module = load_module(db_module)

        self.wrapper = self.db_module.DBWrapper(db_connection)

        params = {'wrapper': self.wrapper}

        self.permissions = self.db_module.Permissions(**params)

        self.config = self.db_module.Config(**params)

        self.quotaholder_serials = self.db_module.QuotaholderSerial(**params)

        for x in ['READ', 'WRITE']:

            setattr(self, x, getattr(self.db_module, x))

        self.node = self.db_module.Node(**params)

        for x in ['ROOTNODE', 'SERIAL', 'HASH', 'SIZE', 'TYPE', 'MTIME', 'MUSER', 'UUID', 'CHECKSUM', 'CLUSTER', 'MATCH_PREFIX', 'MATCH_EXACT']:

            setattr(self, x, getattr(self.db_module, x))

        self.block_module = load_module(block_module)

        params = {'path': block_path,

                  'block_size': self.block_size,

                  'hash_algorithm': self.hash_algorithm,

                  'umask': block_umask}

        self.store = self.block_module.Store(**params)

        if queue_module and queue_hosts:

            self.queue_module = load_module(queue_module)

            params = {'hosts': queue_hosts,

                              'exchange': queue_exchange,

                      'client_id': QUEUE_CLIENT_ID}

            self.queue = self.queue_module.Queue(**params)

        else:

            class NoQueue:

                def send(self, *args):

                    pass

                def close(self):

                    pass

            self.queue = NoQueue()

    def close(self):

        self.wrapper.close()

        self.queue.close()

    @backend_method

    def list_accounts(self, user, marker=None, limit=10000):

        """Return a list of accounts the user can access."""

        logger.debug("list_accounts: %s %s %s", user, marker, limit)

        allowed = self._allowed_accounts(user)

        start, limit = self._list_limits(allowed, marker, limit)

        return allowed[start:start + limit]

    @backend_method

    def get_account_meta(self, user, account, domain, until=None, include_user_defined=True):

        """Return a dictionary with the account metadata for the domain."""

        logger.debug(

            "get_account_meta: %s %s %s %s", user, account, domain, until)

        path, node = self._lookup_account(account, user == account)

        if user != account:

            if until or node is None or account not in self._allowed_accounts(user):

                raise NotAllowedError

        try:

            props = self._get_properties(node, until)

            mtime = props[self.MTIME]

        except NameError:

            props = None

            mtime = until

        count, bytes, tstamp = self._get_statistics(node, until)

        tstamp = max(tstamp, mtime)

        if until is None:

            modified = tstamp

        else:

            modified = self._get_statistics(

                node)[2]  # Overall last modification.

            modified = max(modified, mtime)

        if user != account:

            meta = {'name': account}

        else:

            meta = {}

            if props is not None and include_user_defined:

                meta.update(

                    dict(self.node.attribute_get(props[self.SERIAL], domain)))

            if until is not None:

                meta.update({'until_timestamp': tstamp})

            meta.update({'name': account, 'count': count, 'bytes': bytes})

        meta.update({'modified': modified})

        return meta

    @backend_method

    def update_account_meta(self, user, account, domain, meta, replace=False):

        """Update the metadata associated with the account for the domain."""

        logger.debug("update_account_meta: %s %s %s %s %s", user,

                     account, domain, meta, replace)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_account(account, True)

        self._put_metadata(user, node, domain, meta, replace)

    @backend_method

    def get_account_groups(self, user, account):

        """Return a dictionary with the user groups defined for this account."""

        logger.debug("get_account_groups: %s %s", user, account)

        if user != account:

            if account not in self._allowed_accounts(user):

                raise NotAllowedError

            return {}

        self._lookup_account(account, True)

        return self.permissions.group_dict(account)

    @backend_method

    def update_account_groups(self, user, account, groups, replace=False):

        """Update the groups associated with the account."""

        logger.debug("update_account_groups: %s %s %s %s", user,

                     account, groups, replace)

        if user != account:

            raise NotAllowedError

        self._lookup_account(account, True)

        self._check_groups(groups)

        if replace:

            self.permissions.group_destroy(account)

        for k, v in groups.iteritems():

            if not replace:  # If not already deleted.

                self.permissions.group_delete(account, k)

            if v:

                self.permissions.group_addmany(account, k, v)

    @backend_method

    def get_account_policy(self, user, account):

        """Return a dictionary with the account policy."""

        logger.debug("get_account_policy: %s %s", user, account)

        if user != account:

            if account not in self._allowed_accounts(user):

                raise NotAllowedError

            return {}

        path, node = self._lookup_account(account, True)

        return self._get_policy(node)

    @backend_method

    def update_account_policy(self, user, account, policy, replace=False):

        """Update the policy associated with the account."""

        logger.debug("update_account_policy: %s %s %s %s", user,

                     account, policy, replace)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_account(account, True)

        self._check_policy(policy)

        self._put_policy(node, policy, replace)

    @backend_method

    def put_account(self, user, account, policy={}):

        """Create a new account with the given name."""

        logger.debug("put_account: %s %s %s", user, account, policy)

        if user != account:

            raise NotAllowedError

        node = self.node.node_lookup(account)

        if node is not None:

            raise AccountExists('Account already exists')

        if policy:

            self._check_policy(policy)

        node = self._put_path(user, self.ROOTNODE, account)

        self._put_policy(node, policy, True)

    @backend_method

    def delete_account(self, user, account):

        """Delete the account with the given name."""

        logger.debug("delete_account: %s %s", user, account)

        if user != account:

            raise NotAllowedError

        node = self.node.node_lookup(account)

        if node is None:

            return

        if not self.node.node_remove(node):

            raise AccountNotEmpty('Account is not empty')

        self.permissions.group_destroy(account)

    @backend_method

    def list_containers(self, user, account, marker=None, limit=10000, shared=False, until=None, public=False):

        """Return a list of containers existing under an account."""

        logger.debug("list_containers: %s %s %s %s %s %s %s", user,

                     account, marker, limit, shared, until, public)

        if user != account:

            if until or account not in self._allowed_accounts(user):

                raise NotAllowedError

            allowed = self._allowed_containers(user, account)

            start, limit = self._list_limits(allowed, marker, limit)

            return allowed[start:start + limit]

        if shared or public:

            allowed = set()

            if shared:

                allowed.update([x.split('/', 2)[1] for x in self.permissions.access_list_shared(account)])

            if public:

                allowed.update([x[0].split('/', 2)[1] for x in self.permissions.public_list(account)])

            allowed = sorted(allowed)

            start, limit = self._list_limits(allowed, marker, limit)

            return allowed[start:start + limit]

        node = self.node.node_lookup(account)

        containers = [x[0] for x in self._list_object_properties(

            node, account, '', '/', marker, limit, False, None, [], until)]

        start, limit = self._list_limits(

            [x[0] for x in containers], marker, limit)

        return containers[start:start + limit]

    @backend_method

    def list_container_meta(self, user, account, container, domain, until=None):

        """Return a list with all the container's object meta keys for the domain."""

        logger.debug("list_container_meta: %s %s %s %s %s", user,

                     account, container, domain, until)

        allowed = []

        if user != account:

            if until:

                raise NotAllowedError

            allowed = self.permissions.access_list_paths(

                user, '/'.join((account, container)))

            if not allowed:

                raise NotAllowedError

        path, node = self._lookup_container(account, container)

        before = until if until is not None else inf

        allowed = self._get_formatted_paths(allowed)

        return self.node.latest_attribute_keys(node, domain, before, CLUSTER_DELETED, allowed)

    @backend_method

    def get_container_meta(self, user, account, container, domain, until=None, include_user_defined=True):

        """Return a dictionary with the container metadata for the domain."""

        logger.debug("get_container_meta: %s %s %s %s %s", user,

                     account, container, domain, until)

        if user != account:

            if until or container not in self._allowed_containers(user, account):

                raise NotAllowedError

        path, node = self._lookup_container(account, container)

        props = self._get_properties(node, until)

        mtime = props[self.MTIME]

        count, bytes, tstamp = self._get_statistics(node, until)

        tstamp = max(tstamp, mtime)

        if until is None:

            modified = tstamp

        else:

            modified = self._get_statistics(

                node)[2]  # Overall last modification.

            modified = max(modified, mtime)

        if user != account:

            meta = {'name': container}

        else:

            meta = {}

            if include_user_defined:

                meta.update(

                    dict(self.node.attribute_get(props[self.SERIAL], domain)))

            if until is not None:

                meta.update({'until_timestamp': tstamp})

            meta.update({'name': container, 'count': count, 'bytes': bytes})

        meta.update({'modified': modified})

        return meta

    @backend_method

    def update_container_meta(self, user, account, container, domain, meta, replace=False):

        """Update the metadata associated with the container for the domain."""

        logger.debug("update_container_meta: %s %s %s %s %s %s",

                     user, account, container, domain, meta, replace)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_container(account, container)

        src_version_id, dest_version_id = self._put_metadata(

            user, node, domain, meta, replace)

        if src_version_id is not None:

            versioning = self._get_policy(node)['versioning']

            if versioning != 'auto':

                self.node.version_remove(src_version_id)

    @backend_method

    def get_container_policy(self, user, account, container):

        """Return a dictionary with the container policy."""

        logger.debug(

            "get_container_policy: %s %s %s", user, account, container)

        if user != account:

            if container not in self._allowed_containers(user, account):

                raise NotAllowedError

            return {}

        path, node = self._lookup_container(account, container)

        return self._get_policy(node)

    @backend_method

    def update_container_policy(self, user, account, container, policy, replace=False):

        """Update the policy associated with the container."""

        logger.debug("update_container_policy: %s %s %s %s %s",

                     user, account, container, policy, replace)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_container(account, container)

        self._check_policy(policy)

        self._put_policy(node, policy, replace)

    @backend_method

    def put_container(self, user, account, container, policy={}):

        """Create a new container with the given name."""

        logger.debug(

            "put_container: %s %s %s %s", user, account, container, policy)

        if user != account:

            raise NotAllowedError

        try:

            path, node = self._lookup_container(account, container)

        except NameError:

            pass

        else:

            raise ContainerExists('Container already exists')

        if policy:

            self._check_policy(policy)

        path = '/'.join((account, container))

        node = self._put_path(

            user, self._lookup_account(account, True)[1], path)

        self._put_policy(node, policy, True)

    @backend_method

    def delete_container(self, user, account, container, until=None, prefix='', delimiter=None):

        """Delete/purge the container with the given name."""

        logger.debug("delete_container: %s %s %s %s %s %s", user,

                     account, container, until, prefix, delimiter)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_container(account, container)

        if until is not None:

            hashes, size, serials = self.node.node_purge_children(

                node, until, CLUSTER_HISTORY)

            for h in hashes:

                self.store.map_delete(h)

            self.node.node_purge_children(node, until, CLUSTER_DELETED)

            self._report_size_change(user, account, -size,

                                                             {'action':'container purge', 'path': path,

                                                              'versions': ','.join(str(i) for i in serials)})

            return

        if not delimiter:

            if self._get_statistics(node)[0] > 0:

                raise ContainerNotEmpty('Container is not empty')

            hashes, size, serials = self.node.node_purge_children(

                node, inf, CLUSTER_HISTORY)

            for h in hashes:

                self.store.map_delete(h)

            self.node.node_purge_children(node, inf, CLUSTER_DELETED)

            self.node.node_remove(node)

            self._report_size_change(user, account, -size,

                                                             {'action': 'container delete',

                                                              'path': path,

                                                              'versions': ','.join(str(i) for i in serials)})

        else:

                # remove only contents

            src_names = self._list_objects_no_limit(user, account, container, prefix='', delimiter=None, virtual=False, domain=None, keys=[], shared=False, until=None, size_range=None, all_props=True, public=False)

            paths = []

            for t in src_names:

                path = '/'.join((account, container, t[0]))

                node = t[2]

                src_version_id, dest_version_id = self._put_version_duplicate(user, node, size=0, type='', hash=None, checksum='', cluster=CLUSTER_DELETED)

                del_size = self._apply_versioning(

                    account, container, src_version_id)

                if del_size:

                    self._report_size_change(user, account, -del_size,

                                                                     {'action': 'object delete',

                                                                      'path': path,

                                                                      'versions': ','.join([str(dest_version_id)])})

                self._report_object_change(

                    user, account, path, details={'action': 'object delete'})

                paths.append(path)

            self.permissions.access_clear_bulk(paths)

    def _list_objects(self, user, account, container, prefix, delimiter, marker, limit, virtual, domain, keys, shared, until, size_range, all_props, public):

        if user != account and until:

            raise NotAllowedError

        if shared and public:

            # get shared first

            shared = self._list_object_permissions(

                user, account, container, prefix, shared=True, public=False)

            objects = set()

            if shared:

                path, node = self._lookup_container(account, container)

                shared = self._get_formatted_paths(shared)

                objects |= set(self._list_object_properties(node, path, prefix, delimiter, marker, limit, virtual, domain, keys, until, size_range, shared, all_props))

            # get public

            objects |= set(self._list_public_object_properties(

                user, account, container, prefix, all_props))

            objects = list(objects)

            objects.sort(key=lambda x: x[0])

            start, limit = self._list_limits(

                [x[0] for x in objects], marker, limit)

            return objects[start:start + limit]

        elif public:

            objects = self._list_public_object_properties(

                user, account, container, prefix, all_props)

            start, limit = self._list_limits(

                [x[0] for x in objects], marker, limit)

            return objects[start:start + limit]

        allowed = self._list_object_permissions(

            user, account, container, prefix, shared, public)

        if shared and not allowed:

            return []

        path, node = self._lookup_container(account, container)

        allowed = self._get_formatted_paths(allowed)

        objects = self._list_object_properties(node, path, prefix, delimiter, marker, limit, virtual, domain, keys, until, size_range, allowed, all_props)

        start, limit = self._list_limits(

            [x[0] for x in objects], marker, limit)

        return objects[start:start + limit]

    def _list_public_object_properties(self, user, account, container, prefix, all_props):

        public = self._list_object_permissions(

            user, account, container, prefix, shared=False, public=True)

        paths, nodes = self._lookup_objects(public)

        path = '/'.join((account, container))

        cont_prefix = path + '/'

        paths = [x[len(cont_prefix):] for x in paths]

        props = self.node.version_lookup_bulk(nodes, all_props=all_props)

        objects = [(path,) + props for path, props in zip(paths, props)]

        return objects

    def _list_objects_no_limit(self, user, account, container, prefix, delimiter, virtual, domain, keys, shared, until, size_range, all_props, public):

        objects = []

        while True:

            marker = objects[-1] if objects else None

            limit = 10000

            l = self._list_objects(user, account, container, prefix, delimiter, marker, limit, virtual, domain, keys, shared, until, size_range, all_props, public)

            objects.extend(l)

            if not l or len(l) < limit:

                break

        return objects

    def _list_object_permissions(self, user, account, container, prefix, shared, public):

        allowed = []

        path = '/'.join((account, container, prefix)).rstrip('/')

        if user != account:

            allowed = self.permissions.access_list_paths(user, path)

            if not allowed:

                raise NotAllowedError

        else:

            allowed = set()

            if shared:

                allowed.update(self.permissions.access_list_shared(path))

            if public:

                allowed.update(

                    [x[0] for x in self.permissions.public_list(path)])

            allowed = sorted(allowed)

            if not allowed:

                return []

        return allowed

    @backend_method

    def list_objects(self, user, account, container, prefix='', delimiter=None, marker=None, limit=10000, virtual=True, domain=None, keys=[], shared=False, until=None, size_range=None, public=False):

        """Return a list of object (name, version_id) tuples existing under a container."""

        logger.debug("list_objects: %s %s %s %s %s %s %s %s %s %s %s %s %s %s", user, account, container, prefix, delimiter, marker, limit, virtual, domain, keys, shared, until, size_range, public)

        return self._list_objects(user, account, container, prefix, delimiter, marker, limit, virtual, domain, keys, shared, until, size_range, False, public)

    @backend_method

    def list_object_meta(self, user, account, container, prefix='', delimiter=None, marker=None, limit=10000, virtual=True, domain=None, keys=[], shared=False, until=None, size_range=None, public=False):

        """Return a list of object metadata dicts existing under a container."""

        logger.debug("list_object_meta: %s %s %s %s %s %s %s %s %s %s %s %s %s %s", user, account, container, prefix, delimiter, marker, limit, virtual, domain, keys, shared, until, size_range, public)

        props = self._list_objects(user, account, container, prefix, delimiter, marker, limit, virtual, domain, keys, shared, until, size_range, True, public)

        objects = []

        for p in props:

            if len(p) == 2:

                objects.append({'subdir': p[0]})

            else:

                objects.append({'name': p[0],

                                'bytes': p[self.SIZE + 1],

                                'type': p[self.TYPE + 1],

                                'hash': p[self.HASH + 1],

                                'version': p[self.SERIAL + 1],

                                'version_timestamp': p[self.MTIME + 1],

                                'modified': p[self.MTIME + 1] if until is None else None,

                                'modified_by': p[self.MUSER + 1],

                                'uuid': p[self.UUID + 1],

                                'checksum': p[self.CHECKSUM + 1]})

        return objects

    @backend_method

    def list_object_permissions(self, user, account, container, prefix=''):

        """Return a list of paths that enforce permissions under a container."""

        logger.debug("list_object_permissions: %s %s %s %s", user,

                     account, container, prefix)

        return self._list_object_permissions(user, account, container, prefix, True, False)

    @backend_method

    def list_object_public(self, user, account, container, prefix=''):

        """Return a dict mapping paths to public ids for objects that are public under a container."""

        logger.debug("list_object_public: %s %s %s %s", user,

                     account, container, prefix)

        public = {}

        for path, p in self.permissions.public_list('/'.join((account, container, prefix))):

            public[path] = p + ULTIMATE_ANSWER

        return public

    @backend_method

    def get_object_meta(self, user, account, container, name, domain, version=None, include_user_defined=True):

        """Return a dictionary with the object metadata for the domain."""

        logger.debug("get_object_meta: %s %s %s %s %s %s", user,

                     account, container, name, domain, version)

        self._can_read(user, account, container, name)

        path, node = self._lookup_object(account, container, name)

        props = self._get_version(node, version)

        if version is None:

            modified = props[self.MTIME]

        else:

            try:

                modified = self._get_version(

                    node)[self.MTIME]  # Overall last modification.

            except NameError:  # Object may be deleted.

                del_props = self.node.version_lookup(

                    node, inf, CLUSTER_DELETED)

                if del_props is None:

                    raise ItemNotExists('Object does not exist')

                modified = del_props[self.MTIME]

        meta = {}

        if include_user_defined:

            meta.update(

                dict(self.node.attribute_get(props[self.SERIAL], domain)))

        meta.update({'name': name,

                     'bytes': props[self.SIZE],

                     'type': props[self.TYPE],

                     'hash': props[self.HASH],

                     'version': props[self.SERIAL],

                     'version_timestamp': props[self.MTIME],

                     'modified': modified,

                     'modified_by': props[self.MUSER],

                     'uuid': props[self.UUID],

                     'checksum': props[self.CHECKSUM]})

        return meta

    @backend_method

    def update_object_meta(self, user, account, container, name, domain, meta, replace=False):

        """Update the metadata associated with the object for the domain and return the new version."""

        logger.debug("update_object_meta: %s %s %s %s %s %s %s",

                     user, account, container, name, domain, meta, replace)

        self._can_write(user, account, container, name)

        path, node = self._lookup_object(account, container, name)

        src_version_id, dest_version_id = self._put_metadata(

            user, node, domain, meta, replace)

        self._apply_versioning(account, container, src_version_id)

        return dest_version_id

    @backend_method

    def get_object_permissions(self, user, account, container, name):

        """Return the action allowed on the object, the path

        from which the object gets its permissions from,

        along with a dictionary containing the permissions."""

        logger.debug("get_object_permissions: %s %s %s %s", user,

                     account, container, name)

        allowed = 'write'

        permissions_path = self._get_permissions_path(account, container, name)

        if user != account:

            if self.permissions.access_check(permissions_path, self.WRITE, user):

                allowed = 'write'

            elif self.permissions.access_check(permissions_path, self.READ, user):

                allowed = 'read'

            else:

                raise NotAllowedError

        self._lookup_object(account, container, name)

        return (allowed, permissions_path, self.permissions.access_get(permissions_path))

    @backend_method

    def update_object_permissions(self, user, account, container, name, permissions):

        """Update the permissions associated with the object."""

        logger.debug("update_object_permissions: %s %s %s %s %s",

                     user, account, container, name, permissions)

        if user != account:

            raise NotAllowedError

        path = self._lookup_object(account, container, name)[0]

        self._check_permissions(path, permissions)

        self.permissions.access_set(path, permissions)

        self._report_sharing_change(user, account, path, {'members':

                                    self.permissions.access_members(path)})

    @backend_method

    def get_object_public(self, user, account, container, name):

        """Return the public id of the object if applicable."""

        logger.debug(

            "get_object_public: %s %s %s %s", user, account, container, name)

        self._can_read(user, account, container, name)

        path = self._lookup_object(account, container, name)[0]

        p = self.permissions.public_get(path)

        if p is not None:

            p += ULTIMATE_ANSWER

        return p

    @backend_method