Customizing
***********

Flask-Security bootstraps your application with various views for
handling its configured features to get you up and running as quickly
as possible. However, you'll probably want to change the way these
views look to be more in line with your application's visual design.


Views
=====

Flask-Security is packaged with a default template for each view it
presents to a user. Templates are located within a subfolder named
"security". The following is a list of view templates:

* *security/forgot_password.html*

* *security/login_user.html*

* *security/mf_recovery.html*

* *security/mf_recovery_codes.html*

* *security/register_user.html*

* *security/reset_password.html*

* *security/change_password.html*

* *security/send_confirmation.html*

* *security/send_login.html*

* *security/verify.html*

* *security/two_factor_select.html*

* *security/two_factor_setup.html*

* *security/two_factor_verify_code.html*

* *security/us_signin.html*

* *security/us_setup.html*

* *security/us_verify.html*

* *security/wan_register.html*

* *security/wan_signin.html*

* *security/wan_verify.html*

Overriding these templates is simple:

1. Create a folder named "security" within your application's
   templates folder

2. Create a template with the same name for the template you wish to
   override

You can also specify custom template file paths in the configuration.

Each template is passed a template context object that includes the
following, including the objects/values that are passed to the
template by the main Flask application context processor:

* "<template_name>_form": A form object for the view.

* "security": The Flask-Security extension object.

* "url_for_security": A function that returns the configured URL for
  the passed Security endpoint.

* "_fsdomain": A function used to *tag* strings for extraction and
  localization.

* "_fs_is_user_authenticated": Returns True if argument (user) is
  authenticated. Usually the *current_user* proxy is the appropriate
  argument.

To add more values to the template context, you can specify a context
processor for all views or a specific view. For example:

   security = Security(app, user_datastore)

   # This processor is added to all templates
   @security.context_processor
   def security_context_processor():
       return dict(hello="world")

   # This processor is added to only the register view
   @security.register_context_processor
   def security_register_processor():
       return dict(something="else")

The following is a list of all the available context processor
decorators:

* "context_processor": All views

* "forgot_password_context_processor": Forgot password view

* "login_context_processor": Login view

* "mf_recovery_codes_context_processor": Setup recovery codes view

* "mf_recovery_context_processor": Use recovery code view

* "register_context_processor": Register view

* "reset_password_context_processor": Reset password view

* "change_password_context_processor": Change password view

* "send_confirmation_context_processor": Send confirmation view

* "send_login_context_processor": Send login view

* "mail_context_processor": Whenever an email will be sent

* "tf_select_context_processor": Two factor select view

* "tf_setup_context_processor": Two factor setup view

* "tf_token_validation_context_processor": Two factor token validation
  view

* "us_signin_context_processor": Unified sign in view

* "us_setup_context_processor": Unified sign in setup view

* "wan_register_context_processor": WebAuthn registration view

* "wan_signin_context_processor": WebAuthn sign in view

* "wan_verify_context_processor": WebAuthn verify view


Forms
=====

All forms can be overridden. For each form used, you can specify a
replacement class. This allows you to add extra fields to any form or
override validators. For example it is often desired to add additional
personal information fields to the registration form:

   from flask_security import RegisterForm
   from wtforms import StringField
   from wtforms.validators import DataRequired

   class ExtendedRegisterForm(RegisterForm):
       first_name = StringField('First Name', [DataRequired()])
       last_name = StringField('Last Name', [DataRequired()])

   security = Security(app, user_datastore,
            register_form=ExtendedRegisterForm)

For the "register_form" and "confirm_register_form", only fields that
exist in the user model are passed (as kwargs) to
"UserDatastore.create_user()". Thus, in the above case, the
"first_name" and "last_name" fields will only be passed if the model
looks like:

   class User(db.Model, UserMixin):
       id = db.Column(db.Integer, primary_key=True)
       email = db.Column(db.String(255), unique=True)
       password = db.Column(db.String(255))
       first_name = db.Column(db.String(255))
       last_name = db.Column(db.String(255))

Warning:

  Adding fields is fine - however re-defining existing fields could
  cause various views to no longer function. Many fields have complex
  (and not publicly exposed) validators that have side effects.

Warning:

  It is important to ALWAYS subclass the base Flask-Security form and
  not attempt to just redefine the class. This is due to the
  validation method of many of the forms performs critical additional
  validation AND will change or add values to the form as a side-
  effect. See below for how to do this.

If you need to override an existing field in a form (to override/add
validators), and you want to define a re-usable validator - use
multiple inheritance - be extremely careful about the order of the
inherited classes:

   from wtforms import PasswordField, ValidationError
   from wtforms.validators import DataRequired

   def password_validator(form, field):
       if field.data.startswith("PASS"):
           raise ValidationError("Really - don't start a password with PASS")

   class NewPasswordFormMixinEx:
       password = PasswordField("password",
                                validators=[DataRequired(message="PASSWORD_NOT_PROVIDED"),
                                            password_validator])

   class MyRegisterForm(NewPasswordFormMixinEx, ConfirmRegisterForm):
       pass

   app.config["SECURITY_CONFIRM_REGISTER_FORM"] = MyRegisterForm

The following is a list of all the available form overrides:

* "login_form": Login form

* "verify_form": Verify form

* "confirm_register_form": Confirmable register form

* "register_form": Register form

* "forgot_password_form": Forgot password form

* "reset_password_form": Reset password form

* "change_password_form": Change password form

* "send_confirmation_form": Send confirmation form

* "mf_recovery_codes_form": Setup recovery codes form

* "mf_recovery_form": Use recovery code form

* "passwordless_login_form": Passwordless login form

* "two_factor_verify_code_form": Two-factor verify code form

* "two_factor_select_form": Two-factor select form

* "two_factor_setup_form": Two-factor setup form

* "two_factor_rescue_form": Two-factor help user form

* "us_signin_form": Unified sign in form

* "us_setup_form": Unified sign in setup form

* "us_setup_validate_form": Unified sign in setup validation form

* "us_verify_form": Unified sign in verify form

* "wan_delete_form": WebAuthn delete a registered key form

* "wan_register_form": WebAuthn initiate registration ceremony form

* "wan_register_response_form": WebAuthn registration ceremony form

* "wan_signin_form": WebAuthn initiate sign in ceremony form

* "wan_signin_response_form": WebAuthn sign in ceremony form

* "wan_verify_form": WebAuthn verify form

Tip:

  Changing/extending the form class won't directly change how it is
  displayed. You need to ALSO provide your own template and explicitly
  add the new fields you want displayed.


Controlling Form Instantiation
------------------------------

This is an advanced concept! Please see "Security.set_form_info()" and
"FormInfo".

This is an example of providing your own form instantiator using the
'form clone' pattern. In this example we are injecting an external
*service* into the form for use in validation:

   from flask_security import FormInfo

   class MyLoginForm(LoginForm):
       def __init__(self, *args, service=None, **kwargs):
           super().__init__(*args, **kwargs)
           self.myservice = service

       def instantiator(self, form_name, form_cls, *args, **kwargs):
           return MyLoginForm(*args, service=self.myservice, **kwargs)

       def validate(self, **kwargs: t.Any) -> bool:
           if not super().validate(**kwargs):  # pragma: no cover
               return False
           if not self.myservice(self.email.data):
               self.email.errors.append("Not happening")
               return False
           return True

   # A silly service that only allows 'matt'' log in!
   def login_checker(email):
       return True if email == "matt@lp.com" else False

   with app.test_request_context():
       # Flask-WTForms require a request context.
       fi = MyLoginForm(formdata=None, service=login_checker)
   app.security.set_form_info("login_form", FormInfo(fi.instantiator))


Customizing the Login Form
--------------------------

This is an example of how to modify the registration and login form to
add support for a single input field to accept both email and username
(mimicking legacy Flask-Security behavior). Flask-Security supports
username as a configuration option so this is not strictly needed any
more, however, Flask-Security's LoginForm uses 2 different input
fields (so that appropriate input attributes can be set):

   from flask_security import (
           RegisterForm,
           LoginForm,
           Security,
           lookup_identity,
           uia_username_mapper,
           unique_identity_attribute,
       )
       from werkzeug.local import LocalProxy
       from wtforms import StringField, ValidationError, validators

       def username_validator(form, field):
           # Side-effect - field.data is updated to normalized value.
           # Use proxy to we can declare this prior to initializing Security.
           _security = LocalProxy(lambda: app.extensions["security"])
           msg, field.data = _security._username_util.validate(field.data)
           if msg:
               raise ValidationError(msg)

       class MyRegisterForm(RegisterForm):
           # Note that unique_identity_attribute uses the defined field 'mapper' to
           # normalize. We validate before that to give better error messages and
           # to set the normalized value into the form for saving.
           username = StringField(
               "Username",
               validators=[
                   validators.data_required(),
                   username_validator,
                   unique_identity_attribute,
               ],
           )

       class MyLoginForm(LoginForm):
           email = StringField("email", [validators.data_required()])

           def validate(self, **kwargs):
               self.user = lookup_identity(self.email.data)
               # Setting 'ifield' informs the default login form validation
               # handler that the identity has already been confirmed.
               self.ifield = self.email
               if not super().validate(**kwargs):
                   return False
               return True

       # Allow registration with email, but login only with username
       app.config["SECURITY_USER_IDENTITY_ATTRIBUTES"] = [
           {"username": {"mapper": uia_username_mapper}}
       ]
       security = Security(
           datastore=sqlalchemy_datastore,
           register_form=MyRegisterForm,
           login_form=MyLoginForm,
       )
       security.init_app(app)


Localization
============

All messages, form labels, and form strings are localizable. Flask-
Security uses Flask-Babel to manage its messages.

Tip:

  Be sure to explicitly initialize your babel extension:

     import flask_babel

     flask_babel.Babel(app)

All translations are tagged with a domain, as specified by the
configuration variable "SECURITY_I18N_DOMAIN" (default:
"flask_security"). For messages and labels all this works seamlessly.
For strings inside templates it is necessary to explicitly ask for the
"flask_security" domain, since your application itself might have its
own domain. Flask-Security places the method "_fsdomain" in jinja2's
global environment and uses that in all templates. In order to
reference a Flask-Security translation from ANY template (such as if
you copied and modified an existing security template) just use that
method:

   {{ _fsdomain("Login") }}

Be aware that Flask-Security will validate and normalize email input
using the email_validator package. The normalized form is stored in
the DB.


Overriding Messages
-------------------

It is possible to change one or more messages (either the original
default english and/or a specific translation). Adding the following
to your app:

   app.config["SECURITY_MSG_INVALID_PASSWORD"] = ("Password no-worky", "error")

will change the default message in english.

Tip:

  The string messages themselves are a 'key' into the translation
  .po/.mo files. Do not pass in gettext('string') or
  lazy_gettext('string).

If you need translations then you need to create your own
"translations" directory and add the appropriate .po files and compile
them. Finally, add your translations directory path to the
configuration. In this example, create a file "flask_security.po"
under a directory: "translations/fr_FR/LC_MESSAGES" (for french) with
the following contents:

   msgid ""
   msgstr ""

   msgid "Password no-worky"
   msgstr "Passe - no-worky"

Then compile it with:

   pybabel compile -d translations/ -i translations/fr_FR/LC_MESSAGES/flask_security.po -l fr_FR -D flask_security

Finally add your translations directory to your configuration:

   app.config["SECURITY_I18N_DIRNAME"] = ["builtin", "translations"]


Emails
======

Flask-Security is also packaged with a default template for each email
that it may send. Templates are located within the subfolder named
"security/email". The following is a list of email templates:

* *security/email/confirmation_instructions.html*

* *security/email/confirmation_instructions.txt*

* *security/email/login_instructions.html*

* *security/email/login_instructions.txt*

* *security/email/reset_instructions.html*

* *security/email/reset_instructions.txt*

* *security/email/reset_notice.html*

* *security/email/reset_notice.txt*

* *security/email/change_notice.txt*

* *security/email/change_notice.html*

* *security/email/welcome.html*

* *security/email/welcome.txt*

* *security/email/welcome_existing.html*

* *security/email/welcome_existing.txt*

* *security/email/welcome_existing_username.html*

* *security/email/welcome_existing_username.txt*

* *security/email/two_factor_instructions.html*

* *security/email/two_factor_instructions.txt*

* *security/email/two_factor_rescue.html*

* *security/email/two_factor_rescue.txt*

* *security/email/us_instructions.html*

* *security/email/us_instructions.txt*

Overriding these templates is simple:

1. Create a folder named "security" within your application's
   templates folder

2. Create a folder named "email" within the "security" folder

3. Create a template with the same name for the template you wish to
   override

Each template is passed a template context object that includes values
as described below. In addition, the "security" object is always
passed - you can for example render any security configuration
variable via "security.lower_case_variable_name" and don't include the
prefix "security_" (e.g. "{{ security.confirm_url }")}. If you require
more values in the templates, you can specify an email context
processor with the "mail_context_processor" decorator. For example:

   security = Security(app, user_datastore)

   # This processor is added to all emails
   @security.mail_context_processor
   def security_mail_processor():
       return dict(hello="world")

There are many configuration variables associated with emails, and
each template will receive a slightly different context. The "Gate
Config" column are configuration variables that if set to "False" will
bypass sending of the email (they all default to "True"). In most
cases, in addition to an email being sent, a Signal is sent. The table
below summarizes all this:

+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| **Template Name**             | **Gate Config**                    | **Subject Config**                            | **Context Vars**       | **Signal Sent**                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| welcome                       | SECURITY_SEND_REGISTER_EMAIL       | SECURITY_EMAIL_SUBJECT_REGISTER               | * user  *              | user_registered                  |
|                               |                                    |                                               | confirmation_link  *   |                                  |
|                               |                                    |                                               | confirmation_token     |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| confirmation_instructions     | N/A                                | SECURITY_EMAIL_SUBJECT_CONFIRM                | * user  *              | confirm_instructions_sent        |
|                               |                                    |                                               | confirmation_link  *   |                                  |
|                               |                                    |                                               | confirmation_token     |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| login_instructions            | N/A                                | SECURITY_EMAIL_SUBJECT_PASSWORDLESS           | * user  * login_link   | login_instructions_sent          |
|                               |                                    |                                               | * login_token          |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| reset_instructions            | SEND_PASSWORD_RESET_EMAIL          | SECURITY_EMAIL_SUBJECT_PASSWORD_RESET         | * user  * reset_link   | reset_password_instructions_sent |
|                               |                                    |                                               | * reset_token          |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| reset_notice                  | SEND_PASSWORD_RESET_NOTICE_EMAIL   | SECURITY_EMAIL_SUBJECT_PASSWORD_NOTICE        | * user                 | password_reset                   |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| change_notice                 | SEND_PASSWORD_CHANGE_EMAIL         | SECURITY_EMAIL_SUBJECT_PASSWORD_CHANGE_NOTICE | * user                 | password_changed                 |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| two_factor_instructions       | N/A                                | SECURITY_EMAIL_SUBJECT_TWO_FACTOR             | * user  * token  *     | tf_security_token_sent           |
|                               |                                    |                                               | username               |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| two_factor_rescue             | N/A                                | SECURITY_EMAIL_SUBJECT_TWO_FACTOR_RESCUE      | * user                 | N/A                              |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| us_instructions               | N/A                                | SECURITY_US_EMAIL_SUBJECT                     | * user  * login_token  | us_security_token_sent           |
|                               |                                    |                                               | * login_link  *        |                                  |
|                               |                                    |                                               | username               |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| welcome_existing              | SECURITY_SEND_REGISTER_EMAIL       | SECURITY_EMAIL_SUBJECT_REGISTER               | * user  *              | user_not_registered              |
|                               | SECURITY_RETURN_GENERIC_RESPONSES  |                                               | recovery_link          |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| welcome_existing_username     | SECURITY_SEND_REGISTER_EMAIL       | SECURITY_EMAIL_SUBJECT_REGISTER               | * email  * username    | user_not_registered              |
|                               | SECURITY_RETURN_GENERIC_RESPONSES  |                                               |                        |                                  |
+-------------------------------+------------------------------------+-----------------------------------------------+------------------------+----------------------------------+

When sending an email, Flask-Security goes through the following
steps:

   1. Calls the email context processor as described above

   2. Calls "render_template" (as configured at Flask-Security
      initialization time) with the context and template to produce a
      text and/or html version of the message

   3. Calls "MailUtil.send_mail()" with all the required parameters.

The default implementation of "MailUtil.send_mail" uses flask-mailman
to create and send the message. By providing your own implementation,
you can use any available python email handling package.

Email subjects are by default localized - see above section on
Localization to learn how to customize them.


Emails with Celery
------------------

Sometimes it makes sense to send emails via a task queue, such as
Celery. This is supported by providing your own implementation of the
"MailUtil" class:

   from flask_security import MailUtil
   class MyMailUtil(MailUtil):

       def send_mail(self, template, subject, recipient, sender, body, html, **kwargs):
           send_flask_mail.delay(
               subject=subject,
               from_email=sender,
               to=[recipient],
               body=body,
               html=html,
           )

Then register your class as part of Flask-Security initialization:

   from flask import Flask
   from flask_mailman import EmailMultiAlternatives, Mail
   from flask_security import Security, SQLAlchemyUserDatastore
   from celery import Celery

   mail = Mail()
   security = Security()
   celery = Celery()


   @celery.task
   def send_flask_mail(**kwargs):
       with app.app_context():
           with mail.get_connection() as connection:
               html = kwargs.pop("html", None)
               msg = EmailMultiAlternatives(**kwargs, connection=connection)
               if html:
                   msg.attach_alternative(html, "text/html")
               msg.send()

   def create_app(config):
       """Initialize Flask instance."""

       app = Flask(__name__)
       app.config.from_object(config)

       mail.init_app(app)
       datastore = SQLAlchemyUserDatastore(db, User, Role)
       security.init_app(app, datastore, mail_util_cls=MyMailUtil)

       return app


Responses
=========

Flask-Security will likely be a very small piece of your application,
so Flask-Security makes it easy to override all aspects of API
responses.


JSON Response
-------------

Applications that support a JSON based API need to be able to have a
uniform API response. Flask-Security has a default way to render its
API responses - which can be easily overridden by providing a callback
function via "Security.render_json()". Be aware that Flask-Security
subclasses Flask's JSONProvider interface and sets it on
*app.json_provider_cls*.


401, 403, Oh My
---------------

For a very long read and discussion; look at this. Out of the box,
Flask-Security in tandem with Flask-Login, behaves as follows:

   * If authentication fails as the result of a *@login_required*,
     *@auth_required("session", "token")*, or *@token_auth_required*
     then if the request 'wants' a JSON response,
     "Security.render_json()" is called with a 401 status code. If not
     then the *SECURITY_MSG_UNAUTHENTICATED* message is flashed and
     the request is redirected to the *login* view.

   * If authentication fails as the result of a *@http_auth_required*
     or *@auth_required("basic")* then a 401 is returned along with
     the http header "WWW-Authenticate" set to "Basic realm="xxxx"".
     The realm name is defined by "SECURITY_DEFAULT_HTTP_AUTH_REALM".

   * If authorization fails as the result of *@roles_required*,
     *@roles_accepted*, *@permissions_required*, or
     *@permissions_accepted*, then if the request 'wants' a JSON
     response, "Security.render_json()" is called with a 403 status
     code. If not, then if "SECURITY_UNAUTHORIZED_VIEW" is defined,
     the response will redirected. If "SECURITY_UNAUTHORIZED_VIEW" is
     not defined, then "abort(403)" is called.

All this can be easily changed by registering any or all of
"Security.render_json()", "Security.unauthn_handler()" and
"Security.unauthz_handler()".

The decision on whether to return JSON is based on:

   * Was the request content-type "application/json" (e.g.
     request.is_json()) OR

   * Is the 'best' value of the "Accept" HTTP header
     "application/json"


Redirects
=========

Flask-Security uses redirects frequently (when using forms), and most
of the redirect destinations are configurable. When Flask-Security
initiates a redirect it (almost) always flashes a message that
provides some context for the user. In addition, Flask-Security - both
in its views and default templates, attempts to propagate any *next*
query param and in fact, an existing *?next=/xx* will override most of
the configuration redirect URLs.

As a complex example consider an unauthenticated user accessing a
*@auth_required* endpoint, and the user has two-factor authentication
set up.:

   * GET("/protected") - The *default_unauthn_handler* will redirect
     to "/login?next=/protected"

   * The login form/template will pick any *?next=/xx* argument off
     the request URL and append it to form action.

   * When the form is submitted if will do a
     POST("/login?next=/protected")

   * Assuming correct authentication, the system will send out a
     2-factor code and redirect to "/tf-verify?next=/protected"

   * The two_factor_validation_form/template also pulls any
     *?next=/xx* and appends to the form action.

   * When the *tf-validate* form is submitted it will do a POST("/tf-
     validate?next=/protected").

   * Assuming a correct code, the user is authenticated and is
     redirected. That redirection first looks for a 'next' in the
     request.args then in request.form and finally will use the value
     of "SECURITY_POST_LOGIN_VIEW". In this example it will find the
     "next=/protected" in the request.args and redirect to
     "/protected".
