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/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_setup.html*

* *security/two_factor_verify_code.html*

* *security/us_signin.html*

* *security/us_setup.html*

* *security/us_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

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

* "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_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


Forms
=====

All forms can be overridden. For each form used, you can specify a
replacement class. This allows you to add extra fields to the register
form or override validators:

   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))

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

* "login_form": Login 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

* "passwordless_login_form": Passwordless login form

* "two_factor_verify_code_form": Two-factor verify code 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

Tip:

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


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

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

Finally add your translations directory to your configuration:

   app.config["SECURITY_I18N_DIRNAME"] = [pkg_resources.resource_filename("flask_security", "translations"), "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/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
for any links that are required in the email. 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_instructions     | N/A                              | SECURITY_EMAIL_SUBJECT_CONFIRM                | * user  *              | confirm_instructions_sent        |
|                               |                                  |                                               | confirmation_link      |                                  |
+-------------------------------+----------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| login_instructions            | N/A                              | SECURITY_EMAIL_SUBJECT_PASSWORDLESS           | * user  * login_link   | login_instructions_sent          |
+-------------------------------+----------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| reset_instructions            | SEND_PASSWORD_RESET_EMAIL        | SECURITY_EMAIL_SUBJECT_PASSWORD_RESET         | * user  * reset_link   | reset_password_instructions_sent |
+-------------------------------+----------------------------------+-----------------------------------------------+------------------------+----------------------------------+
| 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  * token  *     | us_security_token_sent           |
|                               |                                  |                                               | login_link  * username |                                  |
+-------------------------------+----------------------------------+-----------------------------------------------+------------------------+----------------------------------+

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-Mail 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, user, **kwargs):
           send_flask_mail.delay(
               subject=subject,
               sender=sender,
               recipients=[recipient],
               body=body,
               html=html,
           )

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

   from flask import Flask
   from flask_mail import Mail, Message
   from flask_security import Security, SQLAlchemyUserDatastore
   from celery import Celery

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


   @celery.task
   def send_flask_mail(**kwargs):
       # If you use Flask_Mail - it needs an app context
       with app.app_context():
           mail.send(Message(**kwargs))

   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
registers its own JsonEncoder on its blueprint.


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, behave 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 flask_login.LoginManager.unauthorized() is called. By
     default THAT will redirect to a 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"


Authorization with OAuth2
=========================

Flask-Security can be set up to co-operate with Flask-OAuthlib, by
implementing a custom request loader that authorizes a user based
either on a *Bearer* token in the HTTP *Authorization* header, or on
the Flask-Security standard authorization logic:

   from flask_oauthlib.provider import OAuth2Provider
   from flask_security import AnonymousUser
   from flask_security.core import (
       _user_loader as _flask_security_user_loader,
       _request_loader as _flask_security_request_loader)
   from flask_security.utils import config_value as security_config_value

   oauth = OAuth2Provider(app)

   def _request_loader(request):
       """
       Load user from OAuth2 Authentication header or using
       Flask-Security's request loader.
       """
       user = None

       if hasattr(request, 'oauth'):
           user = request.oauth.user
       else:
           # Need this try stmt in case oauthlib sometimes throws:
           # AttributeError: dict object has no attribute startswith
           try:
               is_valid, oauth_request = oauth.verify_request(scopes=[])
               if is_valid:
                   user = oauth_request.user
           except AttributeError:
               pass

       if not user:
           user = _flask_security_request_loader(request)

       return user

   def _get_login_manager(app, anonymous_user):
       """Prepare a login manager for Flask-Security to use."""
       login_manager = LoginManager()

       login_manager.anonymous_user = anonymous_user or AnonymousUser
       login_manager.login_view = '{0}.login'.format(
           security_config_value('BLUEPRINT_NAME', app=app))
       login_manager.user_loader(_flask_security_user_loader)
       login_manager.request_loader(_request_loader)

       if security_config_value('FLASH_MESSAGES', app=app):
           (login_manager.login_message,
            login_manager.login_message_category) = (
               security_config_value('MSG_LOGIN', app=app))
           (login_manager.needs_refresh_message,
            login_manager.needs_refresh_message_category) = (
               security_config_value('MSG_REFRESH', app=app))
       else:
           login_manager.login_message = None
           login_manager.needs_refresh_message = None

       login_manager.init_app(app)
       return login_manager

   security = Security(
       app, user_datastore,
       login_manager=_get_login_manager(app, anonymous_user=None))
