diff options
| -rw-r--r-- | server/src/leap/soledad/server/__init__.py | 211 | ||||
| -rw-r--r-- | server/src/leap/soledad/server/lock_resource.py | 232 |
2 files changed, 235 insertions, 208 deletions
diff --git a/server/src/leap/soledad/server/__init__.py b/server/src/leap/soledad/server/__init__.py index 26c33222..b2d55fcd 100644 --- a/server/src/leap/soledad/server/__init__.py +++ b/server/src/leap/soledad/server/__init__.py @@ -87,10 +87,6 @@ and lock documents on the shared database is handled by """ import configparser -import time -import hashlib -import os -import tempfile from u1db.remote import http_app @@ -99,10 +95,6 @@ from u1db.remote import http_app from OpenSSL import tsafe old_tsafe = tsafe -from twisted.web.wsgi import WSGIResource -from twisted.internet import reactor -from twisted.internet.error import TimeoutError -from twisted.python.lockfile import FilesystemLock from twisted import version if version.base() == "12.0.0": # Put OpenSSL's tsafe back into place. This can probably be removed if we @@ -112,19 +104,10 @@ if version.base() == "12.0.0": from leap.soledad.server.auth import SoledadTokenAuthMiddleware from leap.soledad.server.gzip_middleware import GzipMiddleware +from leap.soledad.server.lock_resource import LockResource -from leap.soledad.common import ( - SHARED_DB_NAME, - SHARED_DB_LOCK_DOC_ID_PREFIX, -) +from leap.soledad.common import SHARED_DB_NAME from leap.soledad.common.couch import CouchServerState -from leap.soledad.common.errors import ( - InvalidTokenError, - NotLockedError, - AlreadyLockedError, - LockTimedOutError, - CouldNotObtainLockError, -) #----------------------------------------------------------------------------- @@ -159,195 +142,7 @@ class SoledadApp(http_app.HTTPApp): return http_app.HTTPApp.__call__(self, environ, start_response) -# -# LockResource: a lock based on a document in the shared database. -# - -@http_app.url_to_resource.register -class LockResource(object): - """ - Handle requests for locking documents. - - This class uses Twisted's Filesystem lock to manage a lock in the shared - database. - """ - - url_pattern = '/%s/lock/{uuid}' % SoledadApp.SHARED_DB_NAME - """ - """ - - TIMEOUT = 300 # XXX is 5 minutes reasonable? - """ - The timeout after which the lock expires. - """ - - # used for lock doc storage - TIMESTAMP_KEY = '_timestamp' - LOCK_TOKEN_KEY = '_token' - - FILESYSTEM_LOCK_TRIES = 5 - FILESYSTEM_LOCK_SLEEP_SECONDS = 1 - - def __init__(self, uuid, state, responder): - """ - Initialize the lock resource. Parameters to this constructor are - automatically passed by u1db. - - :param uuid: The user unique id. - :type uuid: str - :param state: The backend database state. - :type state: u1db.remote.ServerState - :param responder: The infrastructure to send responses to client. - :type responder: u1db.remote.HTTPResponder - """ - self._shared_db = state.open_database(SoledadApp.SHARED_DB_NAME) - self._lock_doc_id = '%s%s' % (SHARED_DB_LOCK_DOC_ID_PREFIX, uuid) - self._lock = FilesystemLock( - os.path.join( - tempfile.gettempdir(), - hashlib.sha512(self._lock_doc_id).hexdigest())) - self._state = state - self._responder = responder - - @http_app.http_method(content=str) - def put(self, content=None): - """ - Handle a PUT request to the lock document. - - A lock is a document in the shared db with doc_id equal to - 'lock-<uuid>' and the timestamp of its creation as content. This - method obtains a threaded-lock and creates a lock document if it does - not exist or if it has expired. - - It returns '201 Created' and a pair containing a token to unlock and - the lock timeout, or '403 AlreadyLockedError' and the remaining amount - of seconds the lock will still be valid. - - :param content: The content of the PUT request. It is only here - because PUT requests with empty content are considered - invalid requests by u1db. - :type content: str - """ - # obtain filesystem lock - if not self._try_obtain_filesystem_lock(): - self._responder.send_response_json( - LockTimedOutError.status, # error: request timeout - error=LockTimedOutError.wire_description) - return - - created_lock = False - now = time.time() - token = hashlib.sha256(os.urandom(10)).hexdigest() # for releasing - lock_doc = self._shared_db.get_doc(self._lock_doc_id) - remaining = self._remaining(lock_doc, now) - - # if there's no lock, create one - if lock_doc is None: - lock_doc = self._shared_db.create_doc( - { - self.TIMESTAMP_KEY: now, - self.LOCK_TOKEN_KEY: token, - }, - doc_id=self._lock_doc_id) - created_lock = True - else: - if remaining == 0: - # lock expired, create new one - lock_doc.content = { - self.TIMESTAMP_KEY: now, - self.LOCK_TOKEN_KEY: token, - } - self._shared_db.put_doc(lock_doc) - created_lock = True - - self._try_release_filesystem_lock() - - # send response to client - if created_lock is True: - self._responder.send_response_json( - 201, timeout=self.TIMEOUT, token=token) # success: created - else: - wire_descr = AlreadyLockedError.wire_description - self._responder.send_response_json( - AlreadyLockedError.status, # error: forbidden - error=AlreadyLockedError.wire_description, remaining=remaining) - - @http_app.http_method(token=str) - def delete(self, token=None): - """ - Delete the lock if the C{token} is valid. - - Delete the lock document in case C{token} is equal to the token stored - in the lock document. - - :param token: The token returned when locking. - :type token: str - - :raise NotLockedError: Raised in case the lock is not locked. - :raise InvalidTokenError: Raised in case the token is invalid for - unlocking. - """ - lock_doc = self._shared_db.get_doc(self._lock_doc_id) - if lock_doc is None or self._remaining(lock_doc, time.time()) == 0: - self._responder.send_response_json( - NotLockedError.status, # error: not found - error=NotLockedError.wire_description) - elif token != lock_doc.content[self.LOCK_TOKEN_KEY]: - self._responder.send_response_json( - InvalidTokenError.status, # error: unauthorized - error=InvalidTokenError.wire_description) - else: - self._shared_db.delete_doc(lock_doc) - self._responder.send_response_json(200) # success: should use 204 - # but u1db does not - # support it. - - def _remaining(self, lock_doc, now): - """ - Return the number of seconds the lock contained in C{lock_doc} is - still valid, when compared to C{now}. - - :param lock_doc: The document containing the lock. - :type lock_doc: u1db.Document - :param now: The time to which to compare the lock timestamp. - :type now: float - - :return: The amount of seconds the lock is still valid. - :rtype: float - """ - if lock_doc is not None: - lock_timestamp = lock_doc.content[self.TIMESTAMP_KEY] - remaining = lock_timestamp + self.TIMEOUT - now - return remaining if remaining > 0 else 0.0 - return 0.0 - - def _try_obtain_filesystem_lock(self): - """ - Try to obtain the file system lock. - - @return: Whether the lock was succesfully obtained. - @rtype: bool - """ - tries = self.FILESYSTEM_LOCK_TRIES - while tries > 0: - try: - return self._lock.lock() - except OSError as e: - tries -= 1 - if tries == 0: - raise CouldNotObtainLockError(e.message) - time.sleep(self.FILESYSTEM_LOCK_SLEEP_SECONDS) - return False - - def _try_release_filesystem_lock(self): - """ - Release the filesystem lock. - """ - try: - self._lock.unlock() - return True - except Exception: - return False +http_app.url_to_resource.register(LockResource) #----------------------------------------------------------------------------- diff --git a/server/src/leap/soledad/server/lock_resource.py b/server/src/leap/soledad/server/lock_resource.py new file mode 100644 index 00000000..a7870f77 --- /dev/null +++ b/server/src/leap/soledad/server/lock_resource.py @@ -0,0 +1,232 @@ +# -*- coding: utf-8 -*- +# lock_resource.py +# Copyright (C) 2013 LEAP +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <http://www.gnu.org/licenses/>. + + +""" +LockResource: a lock based on a document in the shared database. +""" + + +import hashlib +import time +import os +import tempfile +import errno + + +from u1db.remote import http_app +from twisted.python.lockfile import FilesystemLock + + +from leap.soledad.common import ( + SHARED_DB_NAME, + SHARED_DB_LOCK_DOC_ID_PREFIX, +) +from leap.soledad.common.errors import ( + InvalidTokenError, + NotLockedError, + AlreadyLockedError, + LockTimedOutError, + CouldNotObtainLockError, +) + + +class LockResource(object): + """ + Handle requests for locking documents. + + This class uses Twisted's Filesystem lock to manage a lock in the shared + database. + """ + + url_pattern = '/%s/lock/{uuid}' % SHARED_DB_NAME + """ + """ + + TIMEOUT = 300 # XXX is 5 minutes reasonable? + """ + The timeout after which the lock expires. + """ + + # used for lock doc storage + TIMESTAMP_KEY = '_timestamp' + LOCK_TOKEN_KEY = '_token' + + FILESYSTEM_LOCK_TRIES = 5 + FILESYSTEM_LOCK_SLEEP_SECONDS = 1 + + def __init__(self, uuid, state, responder): + """ + Initialize the lock resource. Parameters to this constructor are + automatically passed by u1db. + + :param uuid: The user unique id. + :type uuid: str + :param state: The backend database state. + :type state: u1db.remote.ServerState + :param responder: The infrastructure to send responses to client. + :type responder: u1db.remote.HTTPResponder + """ + self._shared_db = state.open_database(SHARED_DB_NAME) + self._lock_doc_id = '%s%s' % (SHARED_DB_LOCK_DOC_ID_PREFIX, uuid) + self._lock = FilesystemLock( + os.path.join( + tempfile.gettempdir(), + hashlib.sha512(self._lock_doc_id).hexdigest())) + self._state = state + self._responder = responder + + @http_app.http_method(content=str) + def put(self, content=None): + """ + Handle a PUT request to the lock document. + + A lock is a document in the shared db with doc_id equal to + 'lock-<uuid>' and the timestamp of its creation as content. This + method obtains a threaded-lock and creates a lock document if it does + not exist or if it has expired. + + It returns '201 Created' and a pair containing a token to unlock and + the lock timeout, or '403 AlreadyLockedError' and the remaining amount + of seconds the lock will still be valid. + + :param content: The content of the PUT request. It is only here + because PUT requests with empty content are considered + invalid requests by u1db. + :type content: str + """ + # obtain filesystem lock + if not self._try_obtain_filesystem_lock(): + self._responder.send_response_json( + LockTimedOutError.status, # error: request timeout + error=LockTimedOutError.wire_description) + return + + created_lock = False + now = time.time() + token = hashlib.sha256(os.urandom(10)).hexdigest() # for releasing + lock_doc = self._shared_db.get_doc(self._lock_doc_id) + remaining = self._remaining(lock_doc, now) + + # if there's no lock, create one + if lock_doc is None: + lock_doc = self._shared_db.create_doc( + { + self.TIMESTAMP_KEY: now, + self.LOCK_TOKEN_KEY: token, + }, + doc_id=self._lock_doc_id) + created_lock = True + else: + if remaining == 0: + # lock expired, create new one + lock_doc.content = { + self.TIMESTAMP_KEY: now, + self.LOCK_TOKEN_KEY: token, + } + self._shared_db.put_doc(lock_doc) + created_lock = True + + self._try_release_filesystem_lock() + + # send response to client + if created_lock is True: + self._responder.send_response_json( + 201, timeout=self.TIMEOUT, token=token) # success: created + else: + self._responder.send_response_json( + AlreadyLockedError.status, # error: forbidden + error=AlreadyLockedError.wire_description, remaining=remaining) + + @http_app.http_method(token=str) + def delete(self, token=None): + """ + Delete the lock if the C{token} is valid. + + Delete the lock document in case C{token} is equal to the token stored + in the lock document. + + :param token: The token returned when locking. + :type token: str + + :raise NotLockedError: Raised in case the lock is not locked. + :raise InvalidTokenError: Raised in case the token is invalid for + unlocking. + """ + lock_doc = self._shared_db.get_doc(self._lock_doc_id) + if lock_doc is None or self._remaining(lock_doc, time.time()) == 0: + self._responder.send_response_json( + NotLockedError.status, # error: not found + error=NotLockedError.wire_description) + elif token != lock_doc.content[self.LOCK_TOKEN_KEY]: + self._responder.send_response_json( + InvalidTokenError.status, # error: unauthorized + error=InvalidTokenError.wire_description) + else: + self._shared_db.delete_doc(lock_doc) + self._responder.send_response_json(200) # success: should use 204 + # but u1db does not + # support it. + + def _remaining(self, lock_doc, now): + """ + Return the number of seconds the lock contained in C{lock_doc} is + still valid, when compared to C{now}. + + :param lock_doc: The document containing the lock. + :type lock_doc: u1db.Document + :param now: The time to which to compare the lock timestamp. + :type now: float + + :return: The amount of seconds the lock is still valid. + :rtype: float + """ + if lock_doc is not None: + lock_timestamp = lock_doc.content[self.TIMESTAMP_KEY] + remaining = lock_timestamp + self.TIMEOUT - now + return remaining if remaining > 0 else 0.0 + return 0.0 + + def _try_obtain_filesystem_lock(self): + """ + Try to obtain the file system lock. + + @return: Whether the lock was succesfully obtained. + @rtype: bool + """ + tries = self.FILESYSTEM_LOCK_TRIES + while tries > 0: + try: + return self._lock.lock() + except OSError as e: + tries -= 1 + if tries == 0: + raise CouldNotObtainLockError(e.message) + time.sleep(self.FILESYSTEM_LOCK_SLEEP_SECONDS) + return False + + def _try_release_filesystem_lock(self): + """ + Release the filesystem lock. + """ + try: + self._lock.unlock() + return True + except OSError as e: + if e.errno == errno.ENOENT: + return True + return False |