.. _validators:
.. module:: registration.validators

Validation utilities
====================

To ease the process of validating user registration data,
django-registration includes some validation-related data and
utilities in ``registration.validators``.

The available error messages are:

.. data:: DUPLICATE_EMAIL

   Error message raised by
   :class:`~registration.forms.RegistrationFormUniqueEmail` when the
   supplied email address is not unique.

.. data:: FREE_EMAIL

   Error message raised by
   :class:`~registration.forms.RegistrationFormNoFreeEmail` when the
   supplied email address is rejected by its list of free-email
   domains.

.. data:: RESERVED_NAME

   Error message raised by
   :class:`~registration.validators.ReservedNameValidator` when it is
   given a value that is a reserved name.

.. data:: TOS_REQUIRED

   Error message raised by
   :class:`~registration.forms.RegistrationFormTermsOfService` when
   the terms-of-service field is not checked.


All of these error messages are marked for translation; most have
translations into multiple languages already in
django-registration.

Additionally, one custom validator is provided:

.. class:: ReservedNameValidator

   A custom validator (see `Django's validators documentation
   <https://docs.djangoproject.com/en/stable/ref/forms/validation/#using-validators>`_)
   which prohibits the use of a reserved name as the value.

   By default, this validator is applied to the username field of
   :class:`registration.forms.RegistrationForm` and all of its
   subclasses. The validator is applied in a form-level ``clean()``
   method on ``RegistrationForm``, so to remove it (not recommended),
   subclass ``RegistrationForm`` and override ``clean()``. For no
   custom form-level validation, you could implement it as:

   .. code-block:: python

      def clean(self):
          pass

   If you want to supply your own custom list of reserved names, you
   can subclass ``RegistrationForm`` and set the attribute
   ``reserved_names`` to the list of values you want to disallow.

   .. note:: **Why reserved names are reserved**

      Many Web applications enable per-user URLs (to display account
      information), and some may also create email addresses or even
      subdomains, based on a user's username. While this is often
      useful, it also represents a risk: a user might register a name
      which conflicts with an important URL, email address or
      subdomain, and this might give that user control over it.

      django-registration includes a list of reserved names, and
      rejects them as usernames by default, in order to avoid this
      issue.

   The default list of reserved names, if you don't specify one, is
   :data:`~registration.validators.DEFAULT_RESERVED_NAMES`. The
   validator will also reject any value beginning with the string
   ``".well-known"`` (see `RFC 5785
   <https://www.ietf.org/rfc/rfc5785.txt>`_).

Several constants are provided which are used by this validator:

.. data:: SPECIAL_HOSTNAMES

   A list of hostnames with reserved or special meaning (such as
   "autoconfig", used by some email clients to automatically discover
   configuration data for a domain).

.. data:: PROTOCOL_HOSTNAMES

   A list of protocol-specific hostnames sites commonly want to
   reserve, such as "www" and "mail".

.. data:: CA_ADDRESSES

   A list of email usernames commonly used by certificate authorities
   when verifying identity.

.. data:: RFC_2142

   A list of common email usernames specified by `RFC 2142
   <https://www.ietf.org/rfc/rfc2142.txt>`_.

.. data:: NOREPLY_ADDRESSES

   A list of common email usernames used for automated messages from a
   Web site (such as "noreply" and "mailer-daemon").

.. data:: SENSITIVE_FILENAMES

   A list of common filenames with important meanings, such that
   usernames should not be allowed to conflict with them (such as
   "favicon.ico" and "robots.txt").

.. data:: OTHER_SENSITIVE_NAMES

   Other names, not covered by the above lists, which have the
   potential to conflict with common URLs or subdomains, such as
   "blog" and "docs".

.. data:: DEFAULT_RESERVED_NAMES

   A list made of the concatentation of all of the above lists, used
   as the default set of reserved names for
   :class:`~registration.validators.ReservedNameValidator`.