.. _Client-Side Field Level Encryption:

Client-Side Field Level Encryption
==================================

.. warning:: Motor will be deprecated on May 14th, 2026, one year after the production release of the PyMongo Async driver. Critical bug fixes will be made until May 14th, 2027.
  We strongly recommend that Motor users migrate to the PyMongo Async driver while Motor is still supported.
  To learn more, see `the migration guide <https://www.mongodb.com/docs/languages/python/pymongo-driver/current/reference/migration/>`_.


Starting in MongoDB 4.2, client-side field level encryption allows an application
to encrypt specific data fields in addition to pre-existing MongoDB
encryption features such as `Encryption at Rest
<https://dochub.mongodb.org/core/security-encryption-at-rest>`_ and
`TLS/SSL (Transport Encryption)
<https://dochub.mongodb.org/core/security-tls-transport-encryption>`_.

With field level encryption, applications can encrypt fields in documents
*prior* to transmitting data over the wire to the server. Client-side field
level encryption supports workloads where applications must guarantee that
unauthorized parties, including server administrators, cannot read the
encrypted data.

.. mongodoc:: client-side-field-level-encryption

Dependencies
------------

To get started using client-side field level encryption in your project,
you will need to install the
`pymongocrypt <https://pypi.org/project/pymongocrypt/>`_ library
as well as the driver itself. Install both the driver and a compatible
version of pymongocrypt like this::

    $ python -m pip install 'motor[encryption]'

Note that installing on Linux requires pip 19 or later for manylinux2010 wheel
support. For more information about installing pymongocrypt see
`the installation instructions on the project's PyPI page
<https://pypi.org/project/pymongocrypt/>`_.

mongocryptd
-----------

The ``mongocryptd`` binary is required for automatic client-side encryption
and is included as a component in the `MongoDB Enterprise Server package
<https://dochub.mongodb.org/core/install-mongodb-enterprise>`_. For more
information on this binary, see the `PyMongo documentation on mongocryptd
<https://pymongo.readthedocs.io/en/stable/examples/encryption.html>`_.

Automatic Client-Side Field Level Encryption
--------------------------------------------

Automatic client-side field level encryption is enabled by creating a
:class:`~motor.motor_asyncio.AsyncIOMotorClient` with the ``auto_encryption_opts``
option set to an instance of
:class:`~pymongo.encryption_options.AutoEncryptionOpts`. The following
examples show how to setup automatic client-side field level encryption
using :class:`~motor.motor_asyncio.AsyncIOMotorClientEncryption` to create a new
encryption data key.

.. note:: Automatic client-side field level encryption requires MongoDB 4.2+
   enterprise or a MongoDB 4.2+ Atlas cluster. The community version of the
   server supports automatic decryption as well as
   :ref:`explicit-client-side-encryption`.

Providing Local Automatic Encryption Rules
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The following example shows how to specify automatic encryption rules via the
``schema_map`` option. The automatic encryption rules are expressed using a
`strict subset of the JSON Schema syntax
<https://dochub.mongodb.org/core/client-side-field-level-encryption-automatic-encryption-rules>`_.

Supplying a ``schema_map`` provides more security than relying on
JSON Schemas obtained from the server. It protects against a
malicious server advertising a false JSON Schema, which could trick
the client into sending unencrypted data that should be encrypted.

JSON Schemas supplied in the ``schema_map`` only apply to configuring
automatic client-side field level encryption. Other validation
rules in the JSON schema will not be enforced by the driver and
will result in an error.


.. literalinclude:: auto_csfle_example.py
  :language: python3

Server-Side Field Level Encryption Enforcement
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The MongoDB 4.2+ server supports using schema validation to enforce encryption
of specific fields in a collection. This schema validation will prevent an
application from inserting unencrypted values for any fields marked with the
``"encrypt"`` JSON schema keyword.

The following example shows how to setup automatic client-side field level
encryption using
:class:`~motor.motor_asyncio.AsyncIOMotorClientEncryption` to create a new encryption
data key and create a collection with the
`Automatic Encryption JSON Schema Syntax
<https://dochub.mongodb.org/core/client-side-field-level-encryption-automatic-encryption-rules>`_.

.. literalinclude:: server_fle_enforcement_example.py
  :language: python3

.. _explicit-client-side-encryption:

Explicit Encryption
~~~~~~~~~~~~~~~~~~~

Explicit encryption is a MongoDB community feature and does not use the
``mongocryptd`` process. Explicit encryption is provided by the
:class:`~motor.motor_asyncio.AsyncIOMotorClientEncryption` class, for example:

.. literalinclude:: explicit_encryption_example.py
  :language: python3

Explicit Encryption with Automatic Decryption
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Although automatic encryption requires MongoDB 4.2 enterprise or a
MongoDB 4.2 Atlas cluster, automatic *decryption* is supported for all users.
To configure automatic *decryption* without automatic *encryption* set
``bypass_auto_encryption=True`` in
:class:`~pymongo.encryption_options.AutoEncryptionOpts`:

.. literalinclude:: explicit_encryption_automatic_decryption_example.py
  :language: python3
