Question

Basically, I need to use the User s password hash to encrypt some data via a custom model field. Check out the snippet I used here: Django Encryption.

I tried this:

class MyClass(models.Model):
    owner = models.ForeignKey(User)
    product_id = EncryptedCharField(max_length=255, user_field=owner)

.................................................................................

    def formfield(self, **kwargs):
        defaults = { max_length : self.max_length,  user_field : self.user_field}
        defaults.update(kwargs)
        return super(EncryptedCharField, self).formfield(**defaults))

But when I try to use user_field, I get a ForeignKey instance (of course!):

user_field = kwargs.get( user_field )
cipher = user_field.password[:32]

Any help is appreciated!

Answer 1

maybe something like this - override the save() method where you can call encrypt method.

for decrypt you can use signal post_init, so every time you instantiate the model from the database the product_id field is decrypted automatically

class MyClass(models.Model):
    user_field = models.ForeignKey(User)
    product_id = EncryptedCharField()
    ...other fields...

    def save(self):
        self.product_id._encrypt(product_id, self.user_field)
        super(MyClass,self).save()

    def decrypt(self):
        if self.product_id != None:
            user = self.user_field
            self.product_id._decrypt(user=user)

def post_init_handler(sender_class, model_instance):
    if isinstance(model_instance, MyClass):
        model_instance.decrypt()

from django.core.signals import post_init
post_init_connect.connect(post_init_handler)


obj = MyClass(user_field=request.user) 
#post_init will be fired but your decrypt method will have
#nothing to decrypt, so it won t garble your input
#you ll either have to remember not to pass value of crypted fields 
#with the constructor, or enforce it with either pre_init method 
#or carefully overriding __init__() method - 
#which is not recommended officially

#decrypt will do real decryption work when you load object form the database

obj.product_id =  blah 
obj.save() #field will be encrypted

maybe there is a more elegant "pythonic" way of doing this

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