Django Encrypted Model Fields (including JSONField)
About
This is a fork of https://gitlab.com/lansharkconsulting/django/django-encrypted-model-fields, which in turn was a fork of https://github.com/foundertherapy/django-cryptographic-fields.
It has been renamed, and updated to properly support Python3 and the latest versions of Django.
django-encrypted-json-fields
is set of fields that wrap standard
Django fields with encryption provided by the python cryptography
library. These fields are much more compatible with a 12-factor design
since they take their encryption key from the settings file instead of a
file on disk used by keyczar
.
While keyczar is an excellent tool to use for encryption, it's not compatible with Python 3, and it requires, for hosts like Heroku, that you either check your key file into your git repository for deployment, or implement manual post-deployment processing to write the key stored in an environment variable into a file that keyczar can read.
JSONField support
django-encrypted-json-fields
extends the origin project django-encrypted-model-fields
by adding a specific support for JSONFields, with the following features:
- the encrypted data remains a valid JSON, so you can inherit from django.db.models.JSONField and all validations will still work
- if the data contains dictionaries, the keys are preserved so that the overall structure remains intact
- that is: we only encrypt the values
Implementation notes
I opted to encrypt the repr() of the values, then apply eval() later only (after decrypting).
This is usefull to reconstruct both the value and the type; since JSON manages only a few simple types, this naive solution just fits the bill.
The crypter
All functions responsible for encryption/decryption (see below) require a crypter
, which
can be obtained in a few ways:
- default crypter: assign a key or a list of keys to the
EJF_ENCRYPTION_KEYS
setting, and a default crypter will be build for you - assigning a callable to the
EJF_ENCRYPTION_KEYS
setting, which in turn will return a list of keys as above - invoke
build_crypter(keys)
explicitly, and pass the resulting object around
For the latter, the use case I had in mind was the need to keep the data in play text on the server, and export encrypted data for a remote client, sharing a common key.
Deferred get_crypter()
Since EJF_ENCRYPTION_KEYS
setting now accepts a callable, which might very well
need to retrieve some data from the Django models, I had to postpone the call to
get_crypter() until all apps have been loaded.
As a side effect, now you can always and safely call the generate_encryption_key
management command (see below)
App settings
EJF_ENCRYPTION_KEYS
either a key, a list of keys, or a callable returning the list of keys to
be used for building the default crypter
EJF_DISABLE_ENCRYPTION
skip encryption when saving the model (save data unencrypted)
Helpers
All function used internally when saving and reading Django models can also be invoked explicitly to apply encryption/decryption to arbitrary strings or JSON values.
A possible use case consists in serializing encrypted data to be sent to a remote client.
Function | Purpone |
---|---|
generate_random_encryption_key() |
generate a key |
build_crypter(keys) |
given a list of keys (or a key) builds the corresponding crypter |
is_encrypted(s: Union[str, bytes]) -> bool |
Check if the given string (or bytes) is the result of an encryption |
encrypt_str(s: str, crypter=None, force=False) -> bytes |
Encrypts the given string applying either the supplied crypter or, in None, the default crypter |
decrypt_bytes(t: bytes, crypter=None, force=False) -> str |
Decrypts the given bytes and returns a string |
encrypt_values(data, crypter=None, force=False, json_skip_keys=None) |
Applyes encryption to a JSON-serializable object |
decrypt_values(data, crypter=None, force=False) |
reverses encrypt_values() |
- force means: proceed even when encryption is disabled in project's settings
Managment commands
Some management commands are supplied; run with --help
for detailed informations:
- generate_encryption_key
- encrypt_str
- decrypt_str
- encrypt_all_tables
- decrypt_all_tables
Getting Started
$ pip install django-encrypted-json-fields
Add "encrypted_json_fields" to your INSTALLED_APPS setting like this:
INSTALLED_APPS = (
...
'encrypted_json_fields',
)
django-encrypted-json-fields
expects the encryption key to be
specified using FIELD_ENCRYPTION_KEY
in your project's settings.py
file. For example, to load it from the local environment:
import os
FIELD_ENCRYPTION_KEY = os.environ.get('FIELD_ENCRYPTION_KEY', '')
To use an encrypted field in a Django model, use one of the fields from
the encrypted_json_fields
module:
from encrypted_json_fields.fields import EncryptedCharField
class EncryptedFieldModel(models.Model):
encrypted_char_field = EncryptedCharField(max_length=100)
For fields that require max_length
to be specified, the Encrypted
variants of those fields will automatically increase the size of the
database field to hold the encrypted form of the content. For example, a
3 character CharField will automatically specify a database field size
of 100 characters when EncryptedCharField(max_length=3)
is specified.
Due to the nature of the encrypted data, filtering by values contained in encrypted fields won't work properly. Sorting is also not supported.
Running Tests
Does the code actually work?
Running the unit tests from this app:
python manage.py test -v 2
or
./runtests.py
or
coverage run --source='.' runtests.py
coverage report
Sample project
A sample project using this app for demonstration purposes is available here:
https://github.com/morlandi/test_django_encrypted_json_fields
Credits
- https://gitlab.com/lansharkconsulting/django/django-encrypted-model-fields has been shared by Scott Sharkey
- https://github.com/foundertherapy/django-cryptographic-fields has been shared by Dana Spiegel