django-pgcrypto-fields is a Django extension which relies upon pgcrypto to
encrypt and decrypt data for fields.
django-pgcrypto-fields has 3 kinds of fields:
- hash based fields
- PGP fields
- Symmetric fields
Hash based fields are:
TextDigestFieldTextHMACField
PGP key fields are:
EmailPGPPublicKeyFieldIntegerPGPPublicKeyFieldTextPGPPublicKeyField
PGP symmetric fields are:
EmailPGPSymmetricKeyFieldIntegerPGPSymmetricKeyFieldTextPGPSymmetricKeyField
- postgres with
pgcrypto
pip install django-pgcrypto-fieldsTextDigestField is a hash based field. The value is hashed in the database when
saved with the digest pgcrypto function using the sha512 algorithm.
TextHMACField is a hash based field. The value is hashed in the database when
saved with the hmac pgcrypto function using a key and the sha512 algorithm.
key is set in settings.PGCRYPTO_KEY.
Public key encryption. It generates a token generated with a public key to encrypt the data and a private key to decrypt it.
Public and private keys can be set in settings with PUBLIC_PGP_KEY and
PRIVATE_PGP_KEY.
The public key is going to encrypt the message and the private key will be needed to decrypt the content. The following commands have been taken from the pgcrypto documentation (see Generating PGP Keys with GnuPG).
Generating a public and a private key:
$ gpg --gen-key
$ gpg --list-secret-keys
/home/bob/.gnupg/secring.gpg
---------------------------
sec 2048R/21 2014-10-23
uid Test Key <example@example.com>
ssb 2048R/42 2014-10-23
$ gpg -a --export 42 > public.key
$ gpg -a --export-secret-keys 21 > private.keySymmetric key encryption. Encrypt and decrypt the data with settings.PGCRYPTO_KEY.
In settings.py:
BASEDIR = os.path.dirname(os.path.dirname(__file__))
PUBLIC_PGP_KEY_PATH = os.path.abspath(os.path.join(BASEDIR, 'public.key'))
PRIVATE_PGP_KEY_PATH = os.path.abspath(os.path.join(BASEDIR, 'private.key'))
# Used by PGPPublicKeyField
PUBLIC_PGP_KEY = open(PUBLIC_PGP_KEY_PATH).read()
PRIVATE_PGP_KEY = open(PRIVATE_PGP_KEY_PATH).read()
# Used by TextHMACField and PGPSymmetricKeyField
PGCRYPTO_KEY='ultrasecret'
# And add 'pgcrypto' to `INSTALLED_APPS` to create the extension for
# pgcrypto (in a migration).
INSTALLED_APPS = (
...
'pgcrypto',
...
)from django.db import models
from pgcrypto import fields
class MyModel(models.Model):
digest_field = fields.TextDigestField()
hmac_field = fields.TextHMACField()
integer_pgp_pub_field = fields.IntegerPGPPublicKeyField()
pgp_pub_field = fields.TextPGPPublicKeyField()
integer_pgp_sym_field = fields.IntegerPGPSymmetricKeyField()
pgp_sym_field = fields.TextPGPSymmetricKeyField()Data is encrypted when inserted into the database.
Example:
>>> MyModel.objects.create(value='Value to be encrypted...')When accessing the field name attribute on a model instance we are getting the decrypted value.
Example:
>>> # When using a PGP public key based encryption
>>> my_model = MyModel.objects.get()
>>> my_model.value # field's proxy
'Value decrypted'To be able to filter PGP values we first need to use an aggregate method to decrypt the values.
Example when using a PGPPublicKeyField:
>>> from pgcrypto.aggregates import PGPPublicKeyAggregate
>>> my_models = MyModel.objects.annotate(PGPPublicKeyAggregate('pgp_pub_field'))
[<MyModel: MyModel object>, <MyModel: MyModel object>]
>>> my_models.filter(pgp_pub_field__decrypted='Value decrypted')
[<MyModel: MyModel object>]
>>> my_models.first().pgp_pub_field__decrypted
'Value decrypted'Example when using a PGPSymmetricKeyField:
>>> from pgcrypto.aggregates import PGPSymmetricKeyAggregate
>>> my_models = MyModel.objects.annotate(PGPSymmetricKeyAggregate('pgp_sym_field'))
[<MyModel: MyModel object>, <MyModel: MyModel object>]
>>> my_models.filter(pgp_pub_field__decrypted='Value decrypted')
[<MyModel: MyModel object>]
>>> my_models.first().pgp_sym_field__decrypted
'Value decrypted'To filter hash based values we need to compare hashes. This is achieved by using
a __hash_of lookup.
Example:
>>> my_model = MyModel.objects.filter(digest_field__hash_of='value')
[<MyModel: MyModel object>]
>>> my_model = MyModel.objects.filter(hmac_field__hash_of='value')
[<MyModel: MyModel object>]