Filtering not supported?

[mflaxman]

I was getting some strange behavior on my site and traced the problem back to this:

In [1]: from customers.models import *
In [2]: foo = KYCUser.objects.filter(ss_num__isnull=False).last()
In [3]: print foo.ss_num
Out[3]: u'123456789'
In [4]: KYCUser.objects.filter(ss_num='123456789')
Out[4]: []

ss_num looks like this in the model defintion:

ss_num = EncryptedCharField(max_length=10, blank=True, null=True, db_index=True)   

Does this library not support filtering? That'd be understandable, but if so it should make that clear in the docs and not fail silently.

Thanks for putting this out there!

[skatenerd]

I too am wondering how to query against an encrypted field. I am thinking it could make sense to query using the encrypted value (perhaps with raw sql). In other words, maybe I could figure out what is actually in the DB table, and query for that value.

There doesn't seem to be a clean way to figure out the encrypted value residing in the database.

Any ideas?

[svetlyak40wt]

You could do exact filtering against encrypted values. That is it.

[skatenerd]

I'm trying:
House.objects.filter(color__exact="green")
and coming up empty-handed, even though
House.objects.last().color == "green"

[skatenerd]

This workaround is working, but it's a litle bit ugly. Note that it basically makes a guess about the mechanics of the random-padding.

color_field = [f for f in House._meta.fields if f.name=='color'][0]
House.objects.filter(color__contains=color_field.get_db_prep_value("green")[:77])

EDIT:
This workaround totally fails

[svetlyak40wt]

I belive there should be a way to do it right. But encrypted field's code was contributed and I'm unaware in it's details and don't use encrypted fields.

But will be glad to accept a pull request with fix and a test for it (tests are in the src/django_fields/tests.py).

[svetlyak40wt]

Oh, and probably I shoudl setup a travis to run these tests automatically. Will add this in my TODO :)

[danieldai]

https://github.com/svetlyak40wt/django-fields/blob/master/src/django_fields/fields.py#L55

This is my be the reason why filtering is not supported here.

self.iv = Random.new().read(self.cipher_object.block_size)
            self.cipher = self.cipher_object.new(
                self.secret_key,
                getattr(self.cipher_object, self.block_type),
                self.iv)

self.iv is different on every instantiation of this class, which causes the encrypted value changes.