From 33e139cae64bb78157ebca56a5d1a752da95555a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?No=C3=A9mi=20V=C3=A1nyi?= <sitbackandwait@gmail.com>
Date: Fri, 23 Oct 2020 16:22:55 +0200
Subject: [PATCH] Let admins lock user preferences

---
 searx/preferences.py                       | 45 ++++++++++++++++++++--
 searx/settings.yml                         |  9 +++++
 searx/settings_robot.yml                   |  3 ++
 searx/templates/courgette/preferences.html | 16 ++++++++
 searx/templates/legacy/preferences.html    | 16 ++++++++
 searx/templates/oscar/preferences.html     | 22 +++++++++++
 searx/templates/pix-art/preferences.html   |  8 ++++
 searx/templates/simple/preferences.html    | 20 ++++++++++
 searx/webadapter.py                        | 10 ++++-
 searx/webapp.py                            |  5 +++
 tests/unit/test_preferences.py             |  2 +-
 11 files changed, 151 insertions(+), 5 deletions(-)

diff --git a/searx/preferences.py b/searx/preferences.py
index f149dc976..e5ad6ead7 100644
--- a/searx/preferences.py
+++ b/searx/preferences.py
@@ -35,9 +35,10 @@ class ValidationException(Exception):
 class Setting:
     """Base class of user settings"""
 
-    def __init__(self, default_value, **kwargs):
+    def __init__(self, default_value, locked=False, **kwargs):
         super().__init__()
         self.value = default_value
+        self.locked = locked
         for key, value in kwargs.items():
             setattr(self, key, value)
 
@@ -115,6 +116,9 @@ class MultipleChoiceSetting(EnumStringSetting):
         self.value = elements
 
     def parse_form(self, data):  # pylint: disable=missing-function-docstring
+        if self.locked:
+            return
+
         self.value = []
         for choice in data:
             if choice in self.choices and choice not in self.value:  # pylint: disable=no-member
@@ -149,6 +153,9 @@ class SetSetting(Setting):
             self.values.add(element)
 
     def parse_form(self, data):  # pylint: disable=missing-function-docstring
+        if self.locked:
+            return
+
         elements = data.split(',')
         self.values = set(elements)  # pylint: disable=attribute-defined-outside-init
 
@@ -233,6 +240,9 @@ class SwitchableSetting(Setting):
             self.enabled = set(data[ENABLED].split(','))
 
     def parse_form(self, items):   # pylint: disable=missing-function-docstring
+        if self.locked:
+            return
+
         items = self.transform_form_items(items)
         self.disabled = set()  # pylint: disable=attribute-defined-outside-init
         self.enabled = set()   # pylint: disable=attribute-defined-outside-init
@@ -317,22 +327,28 @@ class Preferences:
 
         self.key_value_settings = {
             'categories': MultipleChoiceSetting(
-                ['general'], choices=categories + ['none']
+                ['general'],
+                is_locked('categories'),
+                choices=categories + ['none']
             ),
             'language': SearchLanguageSetting(
                 settings['search'].get('default_lang', ''),
+                is_locked('language'),
                 choices=list(LANGUAGE_CODES) + ['']
             ),
             'locale': EnumStringSetting(
                 settings['ui'].get('default_locale', ''),
+                is_locked('locale'),
                 choices=list(settings['locales'].keys()) + ['']
             ),
             'autocomplete': EnumStringSetting(
                 settings['search'].get('autocomplete', ''),
+                is_locked('autocomplete'),
                 choices=list(autocomplete.backends.keys()) + ['']
             ),
             'image_proxy': MapSetting(
                 settings['server'].get('image_proxy', False),
+                is_locked('image_proxy'),
                 map={
                     '': settings['server'].get('image_proxy', 0),
                     '0': False,
@@ -343,10 +359,12 @@ class Preferences:
             ),
             'method': EnumStringSetting(
                 settings['server'].get('method', 'POST'),
+                is_locked('method'),
                 choices=('GET', 'POST')
             ),
             'safesearch': MapSetting(
                 settings['search'].get('safe_search', 0),
+                is_locked('safesearch'),
                 map={
                     '0': 0,
                     '1': 1,
@@ -355,10 +373,12 @@ class Preferences:
             ),
             'theme': EnumStringSetting(
                 settings['ui'].get('default_theme', 'oscar'),
+                is_locked('theme'),
                 choices=themes
             ),
             'results_on_new_tab': MapSetting(
                 settings['ui'].get('results_on_new_tab', False),
+                is_locked('results_on_new_tab'),
                 map={
                     '0': False,
                     '1': True,
@@ -367,10 +387,13 @@ class Preferences:
                 }
             ),
             'doi_resolver': MultipleChoiceSetting(
-                ['oadoi.org'], choices=DOI_RESOLVERS
+                ['oadoi.org'],
+                is_locked('doi_resolver'),
+                choices=DOI_RESOLVERS
             ),
             'oscar-style': EnumStringSetting(
                 settings['ui'].get('theme_args', {}).get('oscar_style', 'logicodev'),
+                is_locked('oscar-style'),
                 choices=['', 'logicodev', 'logicodev-dark', 'pointhi']),
         }
 
@@ -383,6 +406,8 @@ class Preferences:
         """Return preferences as URL parameters"""
         settings_kv = {}
         for k, v in self.key_value_settings.items():
+            if v.locked:
+                continue
             if isinstance(v, MultipleChoiceSetting):
                 settings_kv[k] = ','.join(v.get_value())
             else:
@@ -410,6 +435,8 @@ class Preferences:
         """parse preferences from request (``flask.request.form``)"""
         for user_setting_name, user_setting in input_data.items():
             if user_setting_name in self.key_value_settings:
+                if self.key_value_settings[user_setting_name].locked:
+                    continue
                 self.key_value_settings[user_setting_name].parse(user_setting)
             elif user_setting_name == 'disabled_engines':
                 self.engines.parse_cookie((input_data.get('disabled_engines', ''),
@@ -464,6 +491,8 @@ class Preferences:
         """Save cookie in the HTTP reponse obect
         """
         for user_setting_name, user_setting in self.key_value_settings.items():
+            if self.key_value_settings[user_setting_name].locked:
+                continue
             user_setting.save(user_setting_name, resp)
         self.engines.save(resp)
         self.plugins.save(resp)
@@ -482,3 +511,13 @@ class Preferences:
                     break
 
         return valid
+
+
+def is_locked(setting_name):
+    """Checks if a given setting name is locked by settings.yml
+    """
+    if 'preferences' not in settings:
+        return False
+    if 'lock' not in settings['preferences']:
+        return False
+    return setting_name in settings['preferences']['lock']
diff --git a/searx/settings.yml b/searx/settings.yml
index a599ab285..b23f48b45 100644
--- a/searx/settings.yml
+++ b/searx/settings.yml
@@ -33,6 +33,15 @@ ui:
 #     - it
 #     - science
 
+# Lock arbitrary settings on the preferences page.
+# To find the ID of the user setting you want to lock, check
+# the ID of the form on the page "preferences".
+#preferences:
+#    lock:
+#      - language
+#      - autocomplete
+#      - method
+
 # searx supports result proxification using an external service: https://github.com/asciimoo/morty
 # uncomment below section if you have running morty proxy
 # the key is base64 encoded (keep the !!binary notation)
diff --git a/searx/settings_robot.yml b/searx/settings_robot.yml
index 941a43f83..05c8eeb8c 100644
--- a/searx/settings_robot.yml
+++ b/searx/settings_robot.yml
@@ -17,6 +17,9 @@ ui:
     templates_path : ""
     default_theme : oscar
 
+preferences:
+    lock: []
+
 outgoing:
     request_timeout : 1.0 # seconds
     useragent_suffix : ""
diff --git a/searx/templates/courgette/preferences.html b/searx/templates/courgette/preferences.html
index c67f7662b..6480694b5 100644
--- a/searx/templates/courgette/preferences.html
+++ b/searx/templates/courgette/preferences.html
@@ -5,10 +5,13 @@
     <h2>{{ _('Preferences') }}</h2>
 
     <form method="post" action="{{ url_for('preferences') }}" id="search_form">
+    {% if 'categories' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Default categories') }}</legend>
         {% include 'courgette/categories.html' %}
     </fieldset>
+    {% endif %}
+    {% if 'language' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Search language') }}</legend>
         <p>
@@ -20,6 +23,8 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'locale' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Interface language') }}</legend>
         <p>
@@ -30,6 +35,8 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'autocomplete' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Autocomplete') }}</legend>
         <p>
@@ -41,6 +48,8 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'image_proxy' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Image proxy') }}</legend>
         <p>
@@ -50,6 +59,8 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'method' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Method') }}</legend>
         <p>
@@ -59,6 +70,8 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'safesearch' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('SafeSearch') }}</legend>
         <p>
@@ -69,6 +82,8 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'theme' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Themes') }}</legend>
         <p>
@@ -92,6 +107,7 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
     <fieldset>
         <legend>{{ _('Currently used search engines') }}</legend>
 
diff --git a/searx/templates/legacy/preferences.html b/searx/templates/legacy/preferences.html
index 414b3f6c0..23b3875d2 100644
--- a/searx/templates/legacy/preferences.html
+++ b/searx/templates/legacy/preferences.html
@@ -10,6 +10,7 @@
         {% set display_tooltip = false %}
         {% include 'legacy/categories.html' %}
     </fieldset>
+    {% if 'language' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Search language') }}</legend>
         <p>
@@ -21,6 +22,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'locale' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Interface language') }}</legend>
         <p>
@@ -31,6 +34,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'autocomplete' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Autocomplete') }}</legend>
         <p>
@@ -42,6 +47,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'image_proxy' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Image proxy') }}</legend>
         <p>
@@ -51,6 +58,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'method' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Method') }}</legend>
         <p>
@@ -60,6 +69,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'safesearch' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('SafeSearch') }}</legend>
         <p>
@@ -70,6 +81,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'theme' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Themes') }}</legend>
         <p>
@@ -80,6 +93,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'results_on_new_tab' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Results on new tabs') }}</legend>
         <p>
@@ -89,6 +104,7 @@
             </select>
         </p>
     </fieldset>
+    {% endif %}
     <fieldset>
     <legend>{{ _('Currently used search engines') }}</legend>
 
diff --git a/searx/templates/oscar/preferences.html b/searx/templates/oscar/preferences.html
index 8f67cbf93..b1023a02b 100644
--- a/searx/templates/oscar/preferences.html
+++ b/searx/templates/oscar/preferences.html
@@ -25,6 +25,7 @@
             <div class="tab-pane active" id="tab_general">
                 <fieldset>
                 <div class="container-fluid">
+                    {% if 'categories' not in locked_preferences %}
                     <div class="row form-group">
                         {% if rtl %}
                         <div class="col-sm-11 col-md-10">
@@ -38,12 +39,16 @@
                         </div>
                         {% endif %}
                     </div>
+                    {% endif %}
+                    {% if 'language' not in locked_preferences %}
                     {% set language_label = _('Search language') %}
                     {% set language_info = _('What language do you prefer for search?') %}
                     {{ preferences_item_header(language_info, language_label, rtl, 'language') }}
                                                 {% include 'oscar/languages.html' %}
                     {{ preferences_item_footer(language_info, language_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'locale' not in locked_preferences %}
                     {% set locale_label = _('Interface language') %}
                     {% set locale_info = _('Change the language of the layout') %}
                     {{ preferences_item_header(locale_info, locale_label, rtl, 'locale') }}
@@ -53,7 +58,9 @@
                             {% endfor %}
                         </select>
                     {{ preferences_item_footer(locale_info, locale_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'autocomplete' not in locked_preferences %}
                     {% set autocomplete_label = _('Autocomplete') %}
                     {% set autocomplete_info = _('Find stuff as you type') %}
                     {{ preferences_item_header(autocomplete_info, autocomplete_label, rtl, 'autocomplete') }}
@@ -64,7 +71,9 @@
                             {% endfor %}
                         </select>
                     {{ preferences_item_footer(autocomplete_info, autocomplete_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'image_proxy' not in locked_preferences %}
                     {% set image_proxy_label = _('Image proxy') %}
                     {% set image_proxy_info = _('Proxying image results through searx') %}
                     {{ preferences_item_header(image_proxy_info, image_proxy_label, rtl, 'image_proxy') }}
@@ -73,7 +82,9 @@
                             <option value="" {% if not image_proxy %}selected="selected"{% endif %}>{{ _('Disabled')}}</option>
                         </select>
                     {{ preferences_item_footer(image_proxy_info, image_proxy_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'method' not in locked_preferences %}
                     {% set method_label = _('Method') %}
                     {% set method_info = _('Change how forms are submited, <a href="http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol#Request_methods" rel="external">learn more about request methods</a>') %}
                     {{ preferences_item_header(method_info, method_label, rtl, 'method') }}
@@ -82,7 +93,9 @@
                             <option value="GET" {% if method == 'GET' %}selected="selected"{% endif %}>GET</option>
                         </select>
                     {{ preferences_item_footer(method_info, method_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'safesearch' not in locked_preferences %}
                     {% set safesearch_label = _('SafeSearch') %}
                     {% set safesearch_info = _('Filter content') %}
                     {{ preferences_item_header(safesearch_info, safesearch_label, rtl, 'safesearch') }}
@@ -92,7 +105,9 @@
                             <option value="0" {% if safesearch == '0' %}selected="selected"{% endif %}>{{ _('None') }}</option>
                         </select>
                     {{ preferences_item_footer(safesearch_info, safesearch_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'theme' not in locked_preferences %}
                     {% set theme_label = _('Themes') %}
                     {% set theme_info = _('Change searx layout') %}
                     {{ preferences_item_header(theme_info, theme_label, rtl, 'theme') }}
@@ -102,7 +117,9 @@
                             {% endfor %}
                         </select>
                     {{ preferences_item_footer(theme_info, theme_label, rtl) }}
+                    {% endif %}
 
+                    {% if 'oscar-style' not in locked_preferences %}
                     {{ preferences_item_header(_('Choose style for this theme'), _('Style'), rtl, 'oscar_style') }}
                         <select class="form-control {{ custom_select_class(rtl) }}" name="oscar-style" id="oscar_style">
                             <option value="logicodev" >Logicodev</option>
@@ -110,7 +127,9 @@
                             <option value="logicodev-dark" {% if preferences.get_value('oscar-style') == 'logicodev-dark' %}selected="selected"{% endif %}>Logicodev dark</option>
                         </select>
                     {{ preferences_item_footer(_('Choose style for this theme'), _('Style'), rtl) }}
+                    {% endif %}
 
+                    {% if 'results_on_new_tab' not in locked_preferences %}
                     {% set label = _('Results on new tabs') %}
                     {% set info = _('Open result links on new browser tabs') %}
                     {{ preferences_item_header(info, label, rtl, 'results_on_new_tab') }}
@@ -119,7 +138,9 @@
                             <option value="0" {% if not results_on_new_tab %}selected="selected"{% endif %}>{{ _('Off')}}</option>
                         </select>
                     {{ preferences_item_footer(info, label, rtl) }}
+                    {% endif %}
 
+                    {% if 'doi_resolver' not in locked_preferences %}
                     {% set label = _('Open Access DOI resolver') %}
                     {% set info = _('Redirect to open-access versions of publications when available (plugin required)') %}
                     {{ preferences_item_header(info, label, rtl, 'doi_resolver') }}
@@ -131,6 +152,7 @@
                              {% endfor %}
                          </select>
                     {{ preferences_item_footer(info, label, rtl) }}
+                    {% endif %}
 
                     {% set label = _('Engine tokens') %}
                     {% set info = _('Access tokens for private engines') %}
diff --git a/searx/templates/pix-art/preferences.html b/searx/templates/pix-art/preferences.html
index 05876dedf..ee415435f 100644
--- a/searx/templates/pix-art/preferences.html
+++ b/searx/templates/pix-art/preferences.html
@@ -5,6 +5,7 @@
     <h2>{{ _('Preferences') }}</h2>
 
     <form method="post" action="{{ url_for('preferences') }}" id="search_form">
+    {% if 'language' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Search language') }}</legend>
         <p>
@@ -16,6 +17,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'locale' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Interface language') }}</legend>
         <p>
@@ -26,6 +29,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'method' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Method') }}</legend>
         <p>
@@ -35,6 +40,8 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
+    {% if 'theme' not in locked_preferences %}
     <fieldset>
         <legend>{{ _('Themes') }}</legend>
         <p>
@@ -45,6 +52,7 @@
         </select>
         </p>
     </fieldset>
+    {% endif %}
     <fieldset>
     <legend>{{ _('Currently used search engines') }}</legend>
 
diff --git a/searx/templates/simple/preferences.html b/searx/templates/simple/preferences.html
index 7437ed422..d68e4be5f 100644
--- a/searx/templates/simple/preferences.html
+++ b/searx/templates/simple/preferences.html
@@ -30,11 +30,14 @@
 {{ tabs_open() }}
 
 {{ tab_header('maintab', 'general', _('General')) }}
+  {% if 'categories' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Default categories') }}</legend>
     {% set display_tooltip = false %}
     {% include 'simple/categories.html' %}
   </fieldset>
+  {% endif %}
+  {% if 'language' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Search language') }}</legend>
     <p class="value">{{- '' -}}
@@ -47,6 +50,8 @@
     </p>
     <div class="description">{{ _('What language do you prefer for search?') }}</div>
   </fieldset>
+  {% endif %}
+  {% if 'autocomplete' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Autocomplete') }}</legend>
     <p class="value">
@@ -59,6 +64,8 @@
     </p>
     <div class="description">{{ _('Find stuff as you type') }}</div>
   </fieldset>
+  {% endif %}
+  {% if 'safesearch' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('SafeSearch') }}</legend>
     <p class="value">
@@ -70,7 +77,9 @@
     </p>
     <p class="description">{{ _('Filter content') }}</p>
   </fieldset>
+  {% endif %}
   {{ plugin_preferences('general') }}
+  {% if 'doi_resolver' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Open Access DOI resolver') }}</legend>
     <p class="value">
@@ -84,6 +93,7 @@
     </p>
     <div class="description"><!-- {{ _('Redirect to open-access versions of publications when available (plugin required)') }} --></div>
   </fieldset>
+  {% endif %}
   {{ tab_footer() }}
 
   {{ tab_header('maintab', 'engines', _('Engines')) }}
@@ -129,6 +139,7 @@
   {{ tab_footer() }}
 
   {{ tab_header('maintab', 'ui', _('User interface')) }}
+  {% if 'locale' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Interface language') }}</legend>
     <p class="value">
@@ -140,6 +151,8 @@
     </p>
     <div class="description">{{ _('Change the language of the layout') }}</div>
   </fieldset>
+  {% endif %}
+  {% if 'theme' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Themes') }}</legend>
     <p class="value">
@@ -151,6 +164,8 @@
     </p>
     <div class="description">{{ _('Change searx layout') }}</div>
   </fieldset>
+  {% endif %}
+  {% if 'results_on_new_tab' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Results on new tabs') }}</legend>
     <p class="value">
@@ -161,6 +176,7 @@
     </p>
     <div class="description">{{_('Open result links on new browser tabs') }}</div>
   </fieldset>
+  {% endif %}
   {{ plugin_preferences('ui') }}
   {{ tab_footer() }}
 
@@ -197,6 +213,7 @@
   {{ tab_footer() }}
 
   {{ tab_header('maintab', 'privacy', _('Privacy')) }}
+  {% if 'method' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Method') }}</legend>
     <p class="value">
@@ -207,6 +224,8 @@
     </p>
     <div class="description">{{ _('Search language') }}</div>
   </fieldset>
+  {% endif %}
+  {% if 'image_proxy' not in locked_preferences %}
   <fieldset>
     <legend>{{ _('Image proxy') }}</legend>
     <p class="value">
@@ -217,6 +236,7 @@
     </p>
     <div class="description">{{ _('Proxying image results through searx') }}</div>
   </fieldset>
+  {% endif %}
   {{ plugin_preferences('privacy') }}
 
   {{ tab_footer() }}
diff --git a/searx/webadapter.py b/searx/webadapter.py
index 7ef06b62a..e2867d99d 100644
--- a/searx/webadapter.py
+++ b/searx/webadapter.py
@@ -4,7 +4,7 @@ from searx.webutils import VALID_LANGUAGE_CODE
 from searx.query import RawTextQuery
 from searx.engines import categories, engines
 from searx.search import SearchQuery, EngineRef
-from searx.preferences import Preferences
+from searx.preferences import Preferences, is_locked
 
 
 # remove duplicate queries.
@@ -48,6 +48,8 @@ def parse_pageno(form: Dict[str, str]) -> int:
 
 
 def parse_lang(preferences: Preferences, form: Dict[str, str], raw_text_query: RawTextQuery) -> str:
+    if is_locked('language'):
+        return preferences.get_value('langueage')
     # get language
     # set specific language if set on request, query or preferences
     # TODO support search with multible languages
@@ -66,6 +68,9 @@ def parse_lang(preferences: Preferences, form: Dict[str, str], raw_text_query: R
 
 
 def parse_safesearch(preferences: Preferences, form: Dict[str, str]) -> int:
+    if is_locked('safesearch'):
+        return preferences.get_value('safesearch')
+
     if 'safesearch' in form:
         query_safesearch = form.get('safesearch')
         # first check safesearch
@@ -117,6 +122,9 @@ def parse_specific(raw_text_query: RawTextQuery) -> Tuple[List[EngineRef], List[
 
 
 def parse_category_form(query_categories: List[str], name: str, value: str) -> None:
+    if is_locked('categories'):
+        return preferences.get_value('categories')
+
     if name == 'categories':
         query_categories.extend(categ for categ in map(str.strip, value.split(',')) if categ in categories)
     elif name.startswith('category_'):
diff --git a/searx/webapp.py b/searx/webapp.py
index 5e6a05b19..cf9a09778 100755
--- a/searx/webapp.py
+++ b/searx/webapp.py
@@ -828,6 +828,10 @@ def preferences():
             stats[engine_stat.get('name')]['warn_time'] = True
     # end of stats
 
+    locked_preferences = list()
+    if 'preferences' in settings and 'lock' in settings['preferences']:
+        locked_preferences = settings['preferences']['lock']
+
     return render('preferences.html',
                   selected_categories=get_selected_categories(request.preferences, request.form),
                   all_categories=_get_ordered_categories(),
@@ -848,6 +852,7 @@ def preferences():
                   theme=get_current_theme_name(),
                   preferences_url_params=request.preferences.get_as_url_params(),
                   base_url=get_base_url(),
+                  locked_preferences=locked_preferences,
                   preferences=True)
 
 
diff --git a/tests/unit/test_preferences.py b/tests/unit/test_preferences.py
index 32f50c60b..bee436027 100644
--- a/tests/unit/test_preferences.py
+++ b/tests/unit/test_preferences.py
@@ -141,4 +141,4 @@ class TestPreferences(SearxTestCase):
         pref.parse_encoded_data(url_params)
         self.assertEqual(
             vars(pref.key_value_settings['categories']),
-            {'value': ['general'], 'choices': ['general', 'none']})
+            {'value': ['general'], 'locked': False, 'choices': ['general', 'none']})