feat: Add rate limiter (#1976)

* Add rate limiter

This allows regulation of the number of times a user can
request a particular API or view given a time-frame. It
protects against brute-forcing entry and denial of service.

* Lint

* sigh conflicting linters

* further linting

* Address comments

* ParamSpec is only available > 3.8

* Use latest flask-limiter

* black

* old style flake8

* Fix timeline when inserting

---------

Co-authored-by: Daniel Vaz Gaspar <danielvazgaspar@gmail.com>

docs/security.rst

@@ -389,6 +389,15 @@ Therefore, you can send tweets, post on the users Facebook, retrieve the user's
 Take a look at the `example <https://github.com/dpgaspar/Flask-AppBuilder/tree/master/examples/oauth>`_
 to get an idea of a simple use for this.
 
+Authentication: Rate limiting
+-----------------------------
+
+To prevent brute-forcing of credentials, FlaskApplicationBuilder applies rate limits to AuthViews in 4.2.0, so that
+only 2 POST requests can be made every 5 seconds. This can be disabled by setting ``AUTH_RATE_LIMITED`` to
+``False`` or can be changed by adjusting ``AUTH_RATE_LIMIT`` to, for example, ``1 per 10 seconds``. Take a look
+at the `documentation <https://flask-limiter.readthedocs.io/en/stable/>`_ of Flask-Limiter for more options and
+examples.
+
 Role based
 ----------
 

flask_appbuilder/api/__init__.py

@@ -76,6 +76,7 @@
 from ..hooks import get_before_request_hooks, wrap_route_handler_with_hooks
 from ..models.filters import Filters
 from ..security.decorators import permission_name, protect
+from ..utils.limit import Limit
 
 if TYPE_CHECKING:
     from flask_appbuilder import AppBuilder
@@ -453,6 +454,18 @@ class GreetingApi(BaseApi):
         Use this attribute to override the tag name
     """
 
+    limits: Optional[List[Limit]] = None
+    """
+        List of limits for this api.
+
+        Use it like this if you want to restrict the rate of requests to a view:
+
+            class MyView(ModelView):
+                limits = [Limit("2 per 5 second")]
+
+        or use the decorator @limit.
+    """
+
     def __init__(self) -> None:
         """
         Initialization of base permissions
@@ -490,7 +503,13 @@ def __init__(self) -> None:
         if self.base_permissions is None:
             self.base_permissions = set()
             is_add_base_permissions = True
+
+        if self.limits is None:
+            self.limits = []
+
         for attr_name in dir(self):
+            if hasattr(getattr(self, attr_name), "_limit"):
+                self.limits.append(getattr(getattr(self, attr_name), "_limit"))
             # If include_route_methods is not None white list
             if (
                 self.include_route_methods is not None

flask_appbuilder/base.py

@@ -446,6 +446,7 @@ def add_view(
             if self.app:
                 self.register_blueprint(baseview)
                 self._add_permission(baseview)
+                self.add_limits(baseview)
         self.add_link(
             name=name,
             href=href,
@@ -564,6 +565,7 @@ def add_view_no_menu(
                     baseview, endpoint=endpoint, static_folder=static_folder
                 )
                 self._add_permission(baseview)
+                self.add_limits(baseview)
         else:
             log.warning(LOGMSG_WAR_FAB_VIEW_EXISTS.format(baseview.__class__.__name__))
         return baseview
@@ -649,6 +651,10 @@ def get_url_for_locale(self, lang: str) -> str:
             locale=lang,
         )
 
+    def add_limits(self, baseview: "AbstractViewApi") -> None:
+        if hasattr(baseview, "limits"):
+            self.sm.add_limit_view(baseview)
+
     def add_permissions(self, update_perms: bool = False) -> None:
         from flask_appbuilder.baseviews import AbstractViewApi
 

flask_appbuilder/baseviews.py

@@ -181,8 +181,20 @@ class ContactModelView(ModelView):
     default_view = "list"
     """ the default view for this BaseView, to be used with url_for (method name) """
     extra_args = None
-
     """ dictionary for injecting extra arguments into template """
+
+    limits = None
+    """
+        List of limits for this view.
+
+        Use it like this if you want to restrict the rate of requests to a view:
+
+            class MyView(ModelView):
+                limits = [Limit("2 per 5 second")]
+
+        or use the decorator @limit.
+    """
+
     _apis = None
 
     def __init__(self):
@@ -212,6 +224,9 @@ def __init__(self):
             self.base_permissions = set()
             is_add_base_permissions = True
 
+        if self.limits is None:
+            self.limits = []
+
         for attr_name in dir(self):
             # If include_route_methods is not None white list
             if (
@@ -239,6 +254,8 @@ def __init__(self):
                 _extra = getattr(getattr(self, attr_name), "_extra")
                 for key in _extra:
                     self._apis[key] = _extra[key]
+            if hasattr(getattr(self, attr_name), "_limit"):
+                self.limits.append(getattr(getattr(self, attr_name), "_limit"))
 
     def create_blueprint(self, appbuilder, endpoint=None, static_folder=None):
         """
@@ -385,7 +402,6 @@ def get_init_inner_views(self):
         """
         Sets initialized inner views
         """
-        pass
 
     def get_method_permission(self, method_name: str) -> str:
         """
@@ -436,7 +452,6 @@ def form_get(self, form):
         """
         Override this method to implement your form processing
         """
-        pass
 
     def form_post(self, form):
         """
@@ -447,7 +462,6 @@ def form_post(self, form):
         Return None or a flask response to render
         a custom template or redirect the user
         """
-        pass
 
     def _get_edit_widget(self, form=None, exclude_cols=None, widgets=None):
         exclude_cols = exclude_cols or []
@@ -1380,7 +1394,6 @@ def prefill_form(self, form, pk):
                 if form.email.data:
                     form.email_confirmation.data = form.email.data
         """
-        pass
 
     def process_form(self, form, is_created):
         """
@@ -1396,7 +1409,6 @@ def process_form(self, form, is_created):
                 if not form.owner:
                     form.owner.data = 'n/a'
         """
-        pass
 
     def pre_update(self, item):
         """
@@ -1407,27 +1419,23 @@ def pre_update(self, item):
         implement more complex logic around updates. For instance
         allowing only the original creator of the object to update it.
         """
-        pass
 
     def post_update(self, item):
         """
         Override this, will be called after update
         """
-        pass
 
     def pre_add(self, item):
         """
         Override this, will be called before add.
         If an exception is raised by this method,
         the message is shown to the user and the add operation is aborted.
         """
-        pass
 
     def post_add(self, item):
         """
         Override this, will be called after update
         """
-        pass
 
     def pre_delete(self, item):
         """
@@ -1438,10 +1446,8 @@ def pre_delete(self, item):
         implement more complex logic around deletes. For instance
         allowing only the original creator of the object to delete it.
         """
-        pass
 
     def post_delete(self, item):
         """
         Override this, will be called after delete
         """
-        pass

flask_appbuilder/security/decorators.py

@@ -1,5 +1,6 @@
 import functools
 import logging
+from typing import Callable, List, Optional, TypeVar, Union
 
 from flask import (
     current_app,
@@ -17,12 +18,17 @@
     LOGMSG_ERR_SEC_ACCESS_DENIED,
     PERMISSION_PREFIX,
 )
+from flask_appbuilder.utils.limit import Limit
 from flask_jwt_extended import verify_jwt_in_request
+from flask_limiter.wrappers import RequestLimit
 from flask_login import current_user
-
+from typing_extensions import ParamSpec
 
 log = logging.getLogger(__name__)
 
+R = TypeVar("R")
+P = ParamSpec("P")
+
 
 def response_unauthorized_mvc(status_code: int) -> Response:
     response = make_response(
@@ -228,3 +234,68 @@ def wraps(f):
         return f
 
     return wraps
+
+
+def limit(
+    limit_value: Union[str, Callable[[], str]],
+    key_func: Optional[Callable[[], str]] = None,
+    per_method: bool = False,
+    methods: Optional[List[str]] = None,
+    error_message: Optional[str] = None,
+    exempt_when: Optional[Callable[[], bool]] = None,
+    override_defaults: bool = True,
+    deduct_when: Optional[Callable[[Response], bool]] = None,
+    on_breach: Optional[Callable[[RequestLimit], Optional[Response]]] = None,
+    cost: Union[int, Callable[[], int]] = 1,
+):
+    """
+    Decorator to be used for rate limiting individual routes or blueprints.
+
+    :param limit_value: rate limit string or a callable that returns a
+     string. :ref:`ratelimit-string` for more details.
+    :param key_func: function/lambda to extract the unique
+     identifier for the rate limit. defaults to remote address of the
+     request.
+    :param per_method: whether the limit is sub categorized into the
+     http method of the request.
+    :param methods: if specified, only the methods in this list will
+     be rate limited (default: ``None``).
+    :param error_message: string (or callable that returns one) to override
+     the error message used in the response.
+    :param exempt_when: function/lambda used to decide if the rate
+     limit should skipped.
+    :param override_defaults:  whether the decorated limit overrides
+     the default limits (Default: ``True``).
+
+     .. note:: When used with a :class:`~BaseView` the meaning
+        of the parameter extends to any parents the blueprint instance is
+        registered under. For more details see :ref:`recipes:nested blueprints`
+
+    :param deduct_when: a function that receives the current
+     :class:`flask.Response` object and returns True/False to decide if a
+     deduction should be done from the rate limit
+    :param on_breach: a function that will be called when this limit
+     is breached. If the function returns an instance of :class:`flask.Response`
+     that will be the response embedded into the :exc:`RateLimitExceeded` exception
+     raised.
+    :param cost: The cost of a hit or a function that
+     takes no parameters and returns the cost as an integer (Default: ``1``).
+    """
+
+    def wraps(f: Callable[P, R]) -> Callable[P, R]:
+        _limit = Limit(
+            limit_value=limit_value,
+            key_func=key_func,
+            per_method=per_method,
+            methods=methods,
+            error_message=error_message,
+            exempt_when=exempt_when,
+            override_defaults=override_defaults,
+            deduct_when=deduct_when,
+            on_breach=on_breach,
+            cost=cost,
+        )
+        f._limit = _limit
+        return f
+
+    return wraps

flask_appbuilder/security/manager.py

@@ -5,10 +5,12 @@
 import re
 from typing import Any, Dict, List, Optional, Set, Tuple, Union
 
-from flask import g, session, url_for
+from flask import Flask, g, session, url_for
 from flask_babel import lazy_gettext as _
 from flask_jwt_extended import current_user as current_user_jwt
 from flask_jwt_extended import JWTManager
+from flask_limiter import Limiter
+from flask_limiter.util import get_remote_address
 from flask_login import current_user, LoginManager
 from werkzeug.security import check_password_hash, generate_password_hash
 
@@ -255,6 +257,10 @@ def __init__(self, appbuilder):
             app.config.setdefault("AUTH_LDAP_LASTNAME_FIELD", "sn")
             app.config.setdefault("AUTH_LDAP_EMAIL_FIELD", "mail")
 
+        # Rate limiting
+        app.config.setdefault("AUTH_RATE_LIMITED", True)
+        app.config.setdefault("AUTH_RATE_LIMIT", "2 per 5 second")
+
         if self.auth_type == AUTH_OID:
             from flask_openid import OpenID
 
@@ -285,6 +291,14 @@ def __init__(self, appbuilder):
         # Setup Flask-Jwt-Extended
         self.jwt_manager = self.create_jwt_manager(app)
 
+        # Setup Flask-Limiter
+        self.limiter = self.create_limiter(app)
+
+    def create_limiter(self, app: Flask) -> Limiter:
+        limiter = Limiter(key_func=get_remote_address)
+        limiter.init_app(app)
+        return limiter
+
     def create_login_manager(self, app) -> LoginManager:
         """
         Override to implement your custom login manager instance
@@ -489,6 +503,14 @@ def openid_providers(self):
     def oauth_providers(self):
         return self.appbuilder.get_app.config["OAUTH_PROVIDERS"]
 
+    @property
+    def is_auth_limited(self) -> bool:
+        return self.appbuilder.get_app.config["AUTH_RATE_LIMITED"]
+
+    @property
+    def auth_rate_limit(self) -> str:
+        return self.appbuilder.get_app.config["AUTH_RATE_LIMIT"]
+
     @property
     def current_user(self):
         if current_user.is_authenticated:
@@ -735,6 +757,13 @@ def register_views(self):
 
         self.appbuilder.add_view_no_menu(self.auth_view)
 
+        # this needs to be done after the view is added, otherwise the blueprint
+        # is not initialized
+        if self.is_auth_limited:
+            self.limiter.limit(self.auth_rate_limit, methods=["POST"])(
+                self.auth_view.blueprint
+            )
+
         self.user_view = self.appbuilder.add_view(
             self.user_view,
             "List Users",
@@ -1548,6 +1577,24 @@ def get_user_menu_access(self, menu_names: List[str] = None) -> Set[str]:
                 None, "menu_access", view_menus_name=menu_names
             )
 
+    def add_limit_view(self, baseview):
+        if not baseview.limits:
+            return
+
+        for limit in baseview.limits:
+            self.limiter.limit(
+                limit_value=limit.limit_value,
+                key_func=limit.key_func,
+                per_method=limit.per_method,
+                methods=limit.methods,
+                error_message=limit.error_message,
+                exempt_when=limit.exempt_when,
+                override_defaults=limit.override_defaults,
+                deduct_when=limit.deduct_when,
+                on_breach=limit.on_breach,
+                cost=limit.cost,
+            )(baseview.blueprint)
+
     def add_permissions_view(self, base_permissions, view_menu):
         """
         Adds a permission on a view menu to the backend