[refactor] remove shared db locking from client

Shared db locking was used to avoid the case in which two different devices
try to store/modify remotelly stored secrets at the same time. We want to
avoid remote locks because of the problems they create, and prefer to crash
locally.

For the record, we are currently using the user's password to encrypt the
secrets stored in the server, and while we continue to do this we will have to
re-encrypt the secrets and update the remote storage whenever the user changes
her password.

3 files changed, 49 insertions, 164 deletions

diff --git a/client/src/leap/soledad/client/secrets.py b/client/src/leap/soledad/client/secrets.py
index e2a5a1d7..a72aac0d 100644
--- a/client/src/leap/soledad/client/secrets.py
+++ b/client/src/leap/soledad/client/secrets.py
@@ -33,7 +33,6 @@ from hashlib import sha256
 from leap.soledad.common import soledad_assert
 from leap.soledad.common import soledad_assert_type
 from leap.soledad.common import document
-from leap.soledad.common import errors
 from leap.soledad.client import events
 from leap.soledad.client.crypto import encrypt_sym, decrypt_sym
 
@@ -81,6 +80,7 @@ class BootstrapSequenceError(SecretsException):
 # Secrets handler
 #
 
+
 class SoledadSecrets(object):
 
     """
@@ -162,17 +162,12 @@ class SoledadSecrets(object):
         :param shared_db: The shared database that stores user secrets.
         :type shared_db: leap.soledad.client.shared_db.SoledadSharedDatabase
         """
-        # XXX removed since not in use
-        # We will pick the first secret available.
-        # param secret_id: The id of the storage secret to be used.
-
         self._uuid = uuid
         self._userid = userid
         self._passphrase = passphrase
         self._secrets_path = secrets_path
         self._shared_db = shared_db
         self._secrets = {}
-
         self._secret_id = None
 
     def bootstrap(self):
@@ -197,47 +192,19 @@ class SoledadSecrets(object):
         # STAGE 1 - verify if secrets exist locally
         if not self._has_secret():  # try to load from local storage.
 
-            # STAGE 2 - there are no secrets in local storage, so try to fetch
-            # encrypted secrets from server.
-            logger.info(
-                'Trying to fetch cryptographic secrets from shared recovery '
-                'database...')
-
-            # --- start of atomic operation in shared db ---
-
-            # obtain lock on shared db
-            token = timeout = None
-            try:
-                token, timeout = self._shared_db.lock()
-            except errors.AlreadyLockedError:
-                raise BootstrapSequenceError('Database is already locked.')
-            except errors.LockTimedOutError:
-                raise BootstrapSequenceError('Lock operation timed out.')
+            # STAGE 2 - there are no secrets in local storage and this is the
+            #           first time we are running soledad with the specified
+            #           secrets_path. Try to fetch encrypted secrets from
+            #           server.
+            self._download_crypto_secrets()
 
-            self._get_or_gen_crypto_secrets()
+            if not self._has_secret():
 
-            # release the lock on shared db
-            try:
-                self._shared_db.unlock(token)
-                self._shared_db.close()
-            except errors.NotLockedError:
-                # for some reason the lock expired. Despite that, secret
-                # loading or generation/storage must have been executed
-                # successfully, so we pass.
-                pass
-            except errors.InvalidTokenError:
-                # here, our lock has not only expired but also some other
-                # client application has obtained a new lock and is currently
-                # doing its thing in the shared database. Using the same
-                # reasoning as above, we assume everything went smooth and
-                # pass.
-                pass
-            except Exception as e:
-                logger.error("Unhandled exception when unlocking shared "
-                             "database.")
-                logger.exception(e)
-
-            # --- end of atomic operation in shared db ---
+                # STAGE 3 - there are no secrets in server also, so we want to
+                #           generate the secrets and store them in the remote
+                #           db.
+                self._gen_crypto_secrets()
+                self._upload_crypto_secrets()
 
     def _has_secret(self):
         """
@@ -295,13 +262,14 @@ class SoledadSecrets(object):
             self._store_secrets()
             self._put_secrets_in_shared_db()
 
-    def _get_or_gen_crypto_secrets(self):
+    def _download_crypto_secrets(self):
         """
-        Retrieves or generates the crypto secrets.
-
-        :raises BootstrapSequenceError: Raised when unable to store secrets in
-                                        shared database.
+        Downloads the crypto secrets.
         """
+        logger.info(
+            'Trying to fetch cryptographic secrets from shared recovery '
+            'database...')
+
         if self._shared_db.syncable:
             doc = self._get_secrets_from_shared_db()
         else:
@@ -314,31 +282,39 @@ class SoledadSecrets(object):
             _, active_secret = self._import_recovery_document(doc.content)
             self._maybe_set_active_secret(active_secret)
             self._store_secrets()  # save new secrets in local file
-        else:
-            # STAGE 3 - there are no secrets in server also, so
-            # generate a secret and store it in remote db.
-            logger.info(
-                'No cryptographic secrets found, creating new '
-                ' secrets...')
-            self.set_secret_id(self._gen_secret())
 
-            if self._shared_db.syncable:
+    def _gen_crypto_secrets(self):
+        """
+        Generate the crypto secrets.
+        """
+        logger.info('No cryptographic secrets found, creating new secrets...')
+        secret_id = self._gen_secret()
+        self.set_secret_id(secret_id)
+
+    def _upload_crypto_secrets(self):
+        """
+        Send crypto secrets to shared db.
+
+        :raises BootstrapSequenceError: Raised when unable to store secrets in
+                                        shared database.
+        """
+        if self._shared_db.syncable:
+            try:
+                self._put_secrets_in_shared_db()
+            except Exception as ex:
+                # storing generated secret in shared db failed for
+                # some reason, so we erase the generated secret and
+                # raise.
                 try:
-                    self._put_secrets_in_shared_db()
-                except Exception as ex:
-                    # storing generated secret in shared db failed for
-                    # some reason, so we erase the generated secret and
-                    # raise.
-                    try:
-                        os.unlink(self._secrets_path)
-                    except OSError as e:
-                        if e.errno != errno.ENOENT:
-                            # no such file or directory
-                            logger.exception(e)
-                    logger.exception(ex)
-                    raise BootstrapSequenceError(
-                        'Could not store generated secret in the shared '
-                        'database, bailing out...')
+                    os.unlink(self._secrets_path)
+                except OSError as e:
+                    if e.errno != errno.ENOENT:
+                        # no such file or directory
+                        logger.exception(e)
+                logger.exception(ex)
+                raise BootstrapSequenceError(
+                    'Could not store generated secret in the shared '
+                    'database, bailing out...')
 
     #
     # Shared DB related methods
diff --git a/client/src/leap/soledad/client/shared_db.py b/client/src/leap/soledad/client/shared_db.py
index 6abf8ea3..a1d95fbe 100644
--- a/client/src/leap/soledad/client/shared_db.py
+++ b/client/src/leap/soledad/client/shared_db.py
@@ -151,33 +151,3 @@ class SoledadSharedDatabase(http_database.HTTPDatabase, TokenBasedAuth):
         http_database.HTTPDatabase.__init__(self, url, document_factory,
                                             creds)
         self._uuid = uuid
-
-    def lock(self):
-        """
-        Obtain a lock on document with id C{doc_id}.
-
-        :return: A tuple containing the token to unlock and the timeout until
-                 lock expiration.
-        :rtype: (str, float)
-
-        :raise HTTPError: Raised if any HTTP error occurs.
-        """
-        if self.syncable:
-            res, headers = self._request_json(
-                'PUT', ['lock', self._uuid], body={})
-            return res['token'], res['timeout']
-        else:
-            return None, None
-
-    def unlock(self, token):
-        """
-        Release the lock on shared database.
-
-        :param token: The token returned by a previous call to lock().
-        :type token: str
-
-        :raise HTTPError:
-        """
-        if self.syncable:
-            _, _ = self._request_json(
-                'DELETE', ['lock', self._uuid], params={'token': token})
diff --git a/common/src/leap/soledad/common/errors.py b/common/src/leap/soledad/common/errors.py
index 0b6bb4e6..76a7240d 100644
--- a/common/src/leap/soledad/common/errors.py
+++ b/common/src/leap/soledad/common/errors.py
@@ -71,67 +71,6 @@ class InvalidAuthTokenError(errors.Unauthorized):
 
 
 #
-# LockResource errors
-#
-
-@register_exception
-class InvalidTokenError(SoledadError):
-
-    """
-    Exception raised when trying to unlock shared database with invalid token.
-    """
-
-    wire_description = "unlock unauthorized"
-    status = 401
-
-
-@register_exception
-class NotLockedError(SoledadError):
-
-    """
-    Exception raised when trying to unlock shared database when it is not
-    locked.
-    """
-
-    wire_description = "lock not found"
-    status = 404
-
-
-@register_exception
-class AlreadyLockedError(SoledadError):
-
-    """
-    Exception raised when trying to lock shared database but it is already
-    locked.
-    """
-
-    wire_description = "lock is locked"
-    status = 403
-
-
-@register_exception
-class LockTimedOutError(SoledadError):
-
-    """
-    Exception raised when timing out while trying to lock the shared database.
-    """
-
-    wire_description = "lock timed out"
-    status = 408
-
-
-@register_exception
-class CouldNotObtainLockError(SoledadError):
-
-    """
-    Exception raised when timing out while trying to lock the shared database.
-    """
-
-    wire_description = "error obtaining lock"
-    status = 500
-
-
-#
 # SoledadBackend errors
 # u1db error statuses also have to be updated
 http_errors.ERROR_STATUSES = set(