Add the parameter custom_settings_prefixes to the server config.

programs/server/Server.cpp

@@ -614,6 +614,9 @@ int Server::main(const std::vector<std::string> & /*args*/)
     }
     global_context->setUncompressedCache(uncompressed_cache_size);
 
+    if (config().has("custom_settings_prefixes"))
+        global_context->getAccessControlManager().setCustomSettingsPrefixes(config().getString("custom_settings_prefixes"));
+
     /// Load global settings from default_profile and system_profile.
     global_context->setDefaultProfiles(config());
     const Settings & settings = global_context->getSettingsRef();

programs/server/config.xml

@@ -262,6 +262,9 @@
     <!-- Default profile of settings. -->
     <default_profile>default</default_profile>
 
+    <!-- Comma-separated list of prefixes for user-defined settings. -->
+    <custom_settings_prefixes></custom_settings_prefixes>
+
     <!-- System profile of settings. This settings are used by internal processes (Buffer storage, Distibuted DDL worker and so on). -->
     <!-- <system_profile>default</system_profile> -->
 

src/Access/AccessControlManager.cpp

@@ -11,12 +11,19 @@
 #include <Access/SettingsProfilesCache.h>
 #include <Access/ExternalAuthenticators.h>
 #include <Core/Settings.h>
+#include <common/find_symbols.h>
 #include <Poco/ExpireCache.h>
+#include <boost/algorithm/string/join.hpp>
 #include <mutex>
 
 
 namespace DB
 {
+namespace ErrorCodes
+{
+    extern const int UNKNOWN_SETTING;
+}
+
 namespace
 {
     std::vector<std::unique_ptr<IAccessStorage>> createStorages()
@@ -59,6 +66,53 @@ private:
 };
 
 
+class AccessControlManager::CustomSettingsPrefixes
+{
+public:
+    void registerPrefixes(const Strings & prefixes_)
+    {
+        std::lock_guard lock{mutex};
+        registered_prefixes = prefixes_;
+    }
+
+    bool isSettingNameAllowed(const std::string_view & setting_name) const
+    {
+        if (Settings::hasBuiltin(setting_name))
+            return true;
+
+        std::lock_guard lock{mutex};
+        for (const auto & prefix : registered_prefixes)
+        {
+            if (setting_name.starts_with(prefix))
+                return true;
+        }
+
+        return false;
+    }
+
+    void checkSettingNameIsAllowed(const std::string_view & setting_name) const
+    {
+        if (isSettingNameAllowed(setting_name))
+            return;
+
+        std::lock_guard lock{mutex};
+        if (!registered_prefixes.empty())
+        {
+            throw Exception(
+                "Setting " + String{setting_name} + " is neither a builtin setting nor started with the prefix '"
+                    + boost::algorithm::join(registered_prefixes, "' or '") + "' registered for user-defined settings",
+                ErrorCodes::UNKNOWN_SETTING);
+        }
+        else
+            BaseSettingsHelpers::throwSettingNotFound(setting_name);
+    }
+
+private:
+    Strings registered_prefixes;
+    mutable std::mutex mutex;
+};
+
+
 AccessControlManager::AccessControlManager()
     : MultipleAccessStorage(createStorages()),
       context_access_cache(std::make_unique<ContextAccessCache>(*this)),
@@ -66,7 +120,8 @@ AccessControlManager::AccessControlManager()
       row_policy_cache(std::make_unique<RowPolicyCache>(*this)),
       quota_cache(std::make_unique<QuotaCache>(*this)),
       settings_profiles_cache(std::make_unique<SettingsProfilesCache>(*this)),
-      external_authenticators(std::make_unique<ExternalAuthenticators>())
+      external_authenticators(std::make_unique<ExternalAuthenticators>()),
+      custom_settings_prefixes(std::make_unique<CustomSettingsPrefixes>())
 {
 }
 
@@ -100,6 +155,29 @@ void AccessControlManager::setDefaultProfileName(const String & default_profile_
 }
 
 
+void AccessControlManager::setCustomSettingsPrefixes(const Strings & prefixes)
+{
+    custom_settings_prefixes->registerPrefixes(prefixes);
+}
+
+void AccessControlManager::setCustomSettingsPrefixes(const String & comma_separated_prefixes)
+{
+    Strings prefixes;
+    splitInto<','>(prefixes, comma_separated_prefixes);
+    setCustomSettingsPrefixes(prefixes);
+}
+
+bool AccessControlManager::isSettingNameAllowed(const std::string_view & setting_name) const
+{
+    return custom_settings_prefixes->isSettingNameAllowed(setting_name);
+}
+
+void AccessControlManager::checkSettingNameIsAllowed(const std::string_view & setting_name) const
+{
+    custom_settings_prefixes->checkSettingNameIsAllowed(setting_name);
+}
+
+
 std::shared_ptr<const ContextAccess> AccessControlManager::getContextAccess(
     const UUID & user_id,
     const boost::container::flat_set<UUID> & current_roles,

src/Access/AccessControlManager.h

@@ -53,6 +53,13 @@ public:
     void setUsersConfig(const Poco::Util::AbstractConfiguration & users_config);
     void setDefaultProfileName(const String & default_profile_name);
 
+    /// Sets prefixes which should be used for custom settings.
+    /// This function also enables custom prefixes to be used.
+    void setCustomSettingsPrefixes(const Strings & prefixes);
+    void setCustomSettingsPrefixes(const String & comma_separated_prefixes);
+    bool isSettingNameAllowed(const std::string_view & name) const;
+    void checkSettingNameIsAllowed(const std::string_view & name) const;
+
     std::shared_ptr<const ContextAccess> getContextAccess(
         const UUID & user_id,
         const boost::container::flat_set<UUID> & current_roles,
@@ -89,14 +96,15 @@ public:
 
     const ExternalAuthenticators & getExternalAuthenticators() const;
 
-private:
-    class ContextAccessCache;
+private: class ContextAccessCache;
+    class CustomSettingsPrefixes;
     std::unique_ptr<ContextAccessCache> context_access_cache;
     std::unique_ptr<RoleCache> role_cache;
     std::unique_ptr<RowPolicyCache> row_policy_cache;
     std::unique_ptr<QuotaCache> quota_cache;
     std::unique_ptr<SettingsProfilesCache> settings_profiles_cache;
     std::unique_ptr<ExternalAuthenticators> external_authenticators;
+    std::unique_ptr<CustomSettingsPrefixes> custom_settings_prefixes;
 };
 
 }

src/Access/SettingsConstraints.cpp

@@ -1,4 +1,5 @@
 #include <Access/SettingsConstraints.h>
+#include <Access/AccessControlManager.h>
 #include <Core/Settings.h>
 #include <Common/FieldVisitors.h>
 #include <Common/FieldVisitorsAccurateComparison.h>
@@ -16,7 +17,11 @@ namespace ErrorCodes
     extern const int SETTING_CONSTRAINT_VIOLATION;
 }
 
-SettingsConstraints::SettingsConstraints() = default;
+
+SettingsConstraints::SettingsConstraints(const AccessControlManager & manager_) : manager(&manager_)
+{
+}
+
 SettingsConstraints::SettingsConstraints(const SettingsConstraints & src) = default;
 SettingsConstraints & SettingsConstraints::operator=(const SettingsConstraints & src) = default;
 SettingsConstraints::SettingsConstraints(SettingsConstraints && src) = default;
@@ -191,6 +196,11 @@ bool SettingsConstraints::checkImpl(const Settings & current_settings, SettingCh
         }
     };
 
+    if (reaction == THROW_ON_VIOLATION)
+        manager->checkSettingNameIsAllowed(setting_name);
+    else if (!manager->isSettingNameAllowed(setting_name))
+        return false;
+
     Field current_value, new_value;
     if (current_settings.tryGet(setting_name, current_value))
     {
@@ -316,9 +326,8 @@ bool SettingsConstraints::Constraint::operator==(const Constraint & other) const
         && (*setting_name == *other.setting_name);
 }
 
-
 bool operator ==(const SettingsConstraints & left, const SettingsConstraints & right)
 {
-    return left.constraints == right.constraints;
+    return (left.constraints == right.constraints);
 }
 }

src/Access/SettingsConstraints.h

@@ -14,6 +14,7 @@ namespace DB
 struct Settings;
 struct SettingChange;
 class SettingsChanges;
+class AccessControlManager;
 
 
 /** Checks if specified changes of settings are allowed or not.
@@ -50,7 +51,7 @@ class SettingsChanges;
 class SettingsConstraints
 {
 public:
-    SettingsConstraints();
+    SettingsConstraints(const AccessControlManager & manager_);
     SettingsConstraints(const SettingsConstraints & src);
     SettingsConstraints & operator =(const SettingsConstraints & src);
     SettingsConstraints(SettingsConstraints && src);
@@ -108,6 +109,7 @@ private:
     const Constraint * tryGetConstraint(const std::string_view & setting_name) const;
 
     std::unordered_map<std::string_view, Constraint> constraints;
+    const AccessControlManager * manager = nullptr;
 };
 
 }

src/Access/SettingsProfileElement.cpp

@@ -48,6 +48,10 @@ void SettingsProfileElement::init(const ASTSettingsProfileElement & ast, const A
             min_value = Settings::castValueUtil(setting_name, min_value);
         if (!max_value.isNull())
             max_value = Settings::castValueUtil(setting_name, max_value);
+
+        /// Optionally check if a setting with that name is allowed.
+        if (manager)
+            manager->checkSettingNameIsAllowed(setting_name);
     }
 }
 
@@ -149,9 +153,9 @@ SettingsChanges SettingsProfileElements::toSettingsChanges() const
     return res;
 }
 
-SettingsConstraints SettingsProfileElements::toSettingsConstraints() const
+SettingsConstraints SettingsProfileElements::toSettingsConstraints(const AccessControlManager & manager) const
 {
-    SettingsConstraints res;
+    SettingsConstraints res{manager};
     for (const auto & elem : *this)
     {
         if (!elem.setting_name.empty())

src/Access/SettingsProfileElement.h

@@ -61,7 +61,7 @@ public:
 
     Settings toSettings() const;
     SettingsChanges toSettingsChanges() const;
-    SettingsConstraints toSettingsConstraints() const;
+    SettingsConstraints toSettingsConstraints(const AccessControlManager & manager) const;
 };
 
 }

src/Access/SettingsProfilesCache.cpp

@@ -103,6 +103,7 @@ void SettingsProfilesCache::setDefaultProfileName(const String & default_profile
     default_profile_id = it->second;
 }
 
+
 void SettingsProfilesCache::mergeSettingsAndConstraints()
 {
     /// `mutex` is already locked.
@@ -143,9 +144,10 @@ void SettingsProfilesCache::mergeSettingsAndConstraintsFor(EnabledSettings & ena
 
     substituteProfiles(merged_settings);
 
+    auto settings = merged_settings.toSettings();
+    auto constraints = merged_settings.toSettingsConstraints(manager);
     enabled.setSettingsAndConstraints(
-                std::make_shared<Settings>(merged_settings.toSettings()),
-                std::make_shared<SettingsConstraints>(merged_settings.toSettingsConstraints()));
+        std::make_shared<Settings>(std::move(settings)), std::make_shared<SettingsConstraints>(std::move(constraints)));
 }