How can I set a minimum password length when using the built-in Django auth module?

Question

I’m implementing authentication in a Django site using the built-in auth module, including the built-in UserCreationForm.

I’d like to set a minimum length for passwords. However, I can’t find any documentation on how to do this.

Can I configure the auth module’s User module to require this at the database level? Or should I sub-class the UserCreationForm (I’m actually doing this already for unrelated reasons) and add an extra validator that enforces the password length?

Answer 1

Especially if you're already using a sub-classed UserCreationForm, I'd say you should definitely just add the validation to it. You should be able to override the clean_password method on the form:

def clean_password(self):
    password = self.cleaned_data.get('password1')
    if len(password) < 8:
        raise ValidationError('Password too short')
    return super(MyUserCreationForm, self).clean_password1()

Answer 2

I think the easiest way to achieve this is using Django password validation

For minimum length would be enough adding this to settings file:

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
        'OPTIONS': {
            'min_length': 8,
        }
    },
]

There are others validators like NumericPasswordValidator and CommonPasswordValidator

Answer 3

Subclassing the user creation form sounds like a good approach. You can't enforce it at the database level, since Django only stores a hash of the password.

Answer 4

/django/contrib/auth/password_validation.py Contains class MinimumLengthValidator with default the password minimum length:

class MinimumLengthValidator(object):
    """
    Validate whether the password is of a minimum length.
    """
    def __init__(self, min_length=8):
        self.min_length = min_length

    def validate(self, password, user=None):
        if len(password) < self.min_length:
            raise ValidationError(
                ungettext(
                    "This password is too short. It must contain at least %(min_length)d character.",
                    "This password is too short. It must contain at least %(min_length)d characters.",
                    self.min_length
                ),
                code='password_too_short',
                params={'min_length': self.min_length},
            )

    def get_help_text(self):
        return ungettext(
            "Your password must contain at least %(min_length)d character.",
            "Your password must contain at least %(min_length)d characters.",
            self.min_length
        ) % {'min_length': self.min_length}