gnome-shell/SOURCES/0003-extensionSystem-Allow-extensions-to-run-on-the-login.patch

From 7300ae2eac743fa06f40f6459ac8fbf739ab28ea Mon Sep 17 00:00:00 2001
From: Ray Strode <rstrode@redhat.com>
Date: Tue, 10 Aug 2021 15:03:50 -0400
Subject: [PATCH 3/4] extensionSystem: Allow extensions to run on the login
 screen

At the moment it's not realy possible to extend the login screen to do
things it doesn't have built-in support for. This means in order
to support niche use cases, those cases have to change the main
code base. For instance, oVirt and Vmware deployments want to be able
to automaticaly log in guest VMs when a user pre-authenticates through a
console on a management host. To support those use cases, we added
code to the login screen directly, even though most machines will never
be associated with oVirt or Vmware management hosts.

We also get requests from e.g. government users that need certain features
at the login screen that wouldn't get used much outside of government
deployments. For instance, we've gotten requests that a machine contains
prominently displays that it has "Top Secret" information.

All of these use cases seem like they would better handled via
extensions that could be installed in the specific deployments. The
problem is extensions only run in the user session, and get
disabled at the login screen automatically.

This commit changes that. Now extensions can specify in their metadata
via a new sessionModes property, which modes that want to run in. For
backward compatibility, if an extension doesn't specify which session
modes it works in, its assumed the extension only works in the user
session.
---
 js/ui/extensionSystem.js | 43 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/js/ui/extensionSystem.js b/js/ui/extensionSystem.js
index 05630ed54..dfe82821e 100644
--- a/js/ui/extensionSystem.js
+++ b/js/ui/extensionSystem.js
@@ -21,119 +21,147 @@ var ExtensionManager = class {
     constructor() {
         this._initted = false;
         this._updateNotified = false;
 
         this._extensions = new Map();
         this._enabledExtensions = [];
         this._extensionOrder = [];
 
         Main.sessionMode.connect('updated', this._sessionUpdated.bind(this));
     }
 
     init() {
         this._installExtensionUpdates();
         this._sessionUpdated();
 
         GLib.timeout_add_seconds(GLib.PRIORITY_DEFAULT, UPDATE_CHECK_TIMEOUT, () => {
             ExtensionDownloader.checkForUpdates();
             return GLib.SOURCE_CONTINUE;
         });
         ExtensionDownloader.checkForUpdates();
     }
 
     lookup(uuid) {
         return this._extensions.get(uuid);
     }
 
     getUuids() {
         return [...this._extensions.keys()];
     }
 
+    _extensionSupportsSessionMode(uuid) {
+        let extension = this.lookup(uuid);
+
+        if (!extension)
+            return false;
+
+        if (extension.sessionModes.includes(Main.sessionMode.currentMode))
+            return true;
+
+        if (extension.sessionModes.includes(Main.sessionMode.parentMode))
+            return true;
+
+        return false;
+    }
+
+    _sessionModeCanUseExtension(uuid) {
+        if (!Main.sessionMode.allowExtensions)
+            return false;
+
+        if (!this._extensionSupportsSessionMode(uuid))
+            return false;
+
+        return true;
+    }
+
     _callExtensionDisable(uuid) {
         let extension = this.lookup(uuid);
         if (!extension)
             return;
 
         if (extension.state != ExtensionState.ENABLED)
             return;
 
         // "Rebase" the extension order by disabling and then enabling extensions
         // in order to help prevent conflicts.
 
         // Example:
         //   order = [A, B, C, D, E]
         //   user disables C
         //   this should: disable E, disable D, disable C, enable D, enable E
 
         let orderIdx = this._extensionOrder.indexOf(uuid);
         let order = this._extensionOrder.slice(orderIdx + 1);
         let orderReversed = order.slice().reverse();
 
         for (let i = 0; i < orderReversed.length; i++) {
             let uuid = orderReversed[i];
             try {
                 this.lookup(uuid).stateObj.disable();
             } catch (e) {
                 this.logExtensionError(uuid, e);
             }
         }
 
         if (extension.stylesheet) {
             let theme = St.ThemeContext.get_for_stage(global.stage).get_theme();
             theme.unload_stylesheet(extension.stylesheet);
             delete extension.stylesheet;
         }
 
         try {
             extension.stateObj.disable();
         } catch(e) {
             this.logExtensionError(uuid, e);
         }
 
         for (let i = 0; i < order.length; i++) {
             let uuid = order[i];
             try {
                 this.lookup(uuid).stateObj.enable();
             } catch (e) {
                 this.logExtensionError(uuid, e);
             }
         }
 
         this._extensionOrder.splice(orderIdx, 1);
 
         if (extension.state != ExtensionState.ERROR) {
             extension.state = ExtensionState.DISABLED;
             this.emit('extension-state-changed', extension);
         }
     }
 
     _callExtensionEnable(uuid) {
+        if (!this._sessionModeCanUseExtension(uuid))
+            return;
+
         let extension = this.lookup(uuid);
         if (!extension)
             return;
 
         if (extension.state == ExtensionState.INITIALIZED)
             this._callExtensionInit(uuid);
 
         if (extension.state != ExtensionState.DISABLED)
             return;
 
         this._extensionOrder.push(uuid);
 
         let stylesheetNames = [global.session_mode + '.css', 'stylesheet.css'];
         let theme = St.ThemeContext.get_for_stage(global.stage).get_theme();
         for (let i = 0; i < stylesheetNames.length; i++) {
             try {
                 let stylesheetFile = extension.dir.get_child(stylesheetNames[i]);
                 theme.load_stylesheet(stylesheetFile);
                 extension.stylesheet = stylesheetFile;
                 break;
             } catch (e) {
                 if (e.matches(Gio.IOErrorEnum, Gio.IOErrorEnum.NOT_FOUND))
                     continue; // not an error
                 log(`Failed to load stylesheet for extension ${uuid}: ${e.message}`);
                 return;
             }
         }
 
         try {
             extension.stateObj.enable();
@@ -231,61 +259,62 @@ var ExtensionManager = class {
             throw new Error(`Failed to load metadata.json: ${e}`);
         }
         let meta;
         try {
             meta = JSON.parse(metadataContents);
         } catch (e) {
             throw new Error(`Failed to parse metadata.json: ${e}`);
         }
 
         let requiredProperties = ['uuid', 'name', 'description', 'shell-version'];
         for (let i = 0; i < requiredProperties.length; i++) {
             let prop = requiredProperties[i];
             if (!meta[prop]) {
                 throw new Error(`missing "${prop}" property in metadata.json`);
             }
         }
 
         if (uuid != meta.uuid) {
             throw new Error(`uuid "${meta.uuid}" from metadata.json does not match directory name "${uuid}"`);
         }
 
         let extension = {
             metadata: meta,
             uuid: meta.uuid,
             type,
             dir,
             path: dir.get_path(),
             error: '',
             hasPrefs: dir.get_child('prefs.js').query_exists(null),
             hasUpdate: false,
-            canChange: false
+            canChange: false,
+            sessionModes: meta['session-modes'] ? meta['session-modes'] : [ 'user' ],
         };
         this._extensions.set(uuid, extension);
 
         return extension;
     }
 
     loadExtension(extension) {
         // Default to error, we set success as the last step
         extension.state = ExtensionState.ERROR;
 
         let checkVersion = !global.settings.get_boolean(EXTENSION_DISABLE_VERSION_CHECK_KEY);
 
         if (checkVersion && ExtensionUtils.isOutOfDate(extension)) {
             extension.state = ExtensionState.OUT_OF_DATE;
         } else {
             let enabled = this._enabledExtensions.includes(extension.uuid);
             if (enabled) {
                 if (!this._callExtensionInit(extension.uuid))
                     return;
                 if (extension.state == ExtensionState.DISABLED)
                     this._callExtensionEnable(extension.uuid);
             } else {
                 extension.state = ExtensionState.INITIALIZED;
             }
         }
 
         this._updateCanChange(extension);
         this.emit('extension-state-changed', extension);
     }
 
@@ -296,60 +325,63 @@ var ExtensionManager = class {
         this._callExtensionDisable(extension.uuid);
 
         extension.state = ExtensionState.UNINSTALLED;
         this.emit('extension-state-changed', extension);
 
         this._extensions.delete(extension.uuid);
         return true;
     }
 
     reloadExtension(oldExtension) {
         // Grab the things we'll need to pass to createExtensionObject
         // to reload it.
         let { uuid: uuid, dir: dir, type: type } = oldExtension;
 
         // Then unload the old extension.
         this.unloadExtension(oldExtension);
 
         // Now, recreate the extension and load it.
         let newExtension;
         try {
             newExtension = this.createExtensionObject(uuid, dir, type);
         } catch (e) {
             this.logExtensionError(uuid, e);
             return;
         }
 
         this.loadExtension(newExtension);
     }
 
     _callExtensionInit(uuid) {
+        if (!this._sessionModeCanUseExtension(uuid))
+            return false;
+
         let extension = this.lookup(uuid);
         let dir = extension.dir;
 
         if (!extension)
             throw new Error("Extension was not properly created. Call loadExtension first");
 
         let extensionJs = dir.get_child('extension.js');
         if (!extensionJs.query_exists(null)) {
             this.logExtensionError(uuid, new Error('Missing extension.js'));
             return false;
         }
 
         let extensionModule;
         let extensionState = null;
 
         ExtensionUtils.installImporter(extension);
         try {
             extensionModule = extension.imports.extension;
         } catch(e) {
             this.logExtensionError(uuid, e);
             return false;
         }
 
         if (extensionModule.init) {
             try {
                 extensionState = extensionModule.init(extension);
             } catch (e) {
                 this.logExtensionError(uuid, e);
                 return false;
             }
@@ -377,69 +409,72 @@ var ExtensionManager = class {
 
         let isMode = this._getModeExtensions().includes(extension.uuid);
         let modeOnly = global.settings.get_boolean(DISABLE_USER_EXTENSIONS_KEY);
 
         extension.canChange =
             !hasError &&
             global.settings.is_writable(ENABLED_EXTENSIONS_KEY) &&
             (isMode || !modeOnly);
     }
 
     _getEnabledExtensions() {
         let extensions = this._getModeExtensions();
 
         if (global.settings.get_boolean(DISABLE_USER_EXTENSIONS_KEY))
             return extensions;
 
         return extensions.concat(global.settings.get_strv(ENABLED_EXTENSIONS_KEY));
     }
 
     _onUserExtensionsEnabledChanged() {
         this._onEnabledExtensionsChanged();
         this._onSettingsWritableChanged();
     }
 
     _onEnabledExtensionsChanged() {
         let newEnabledExtensions = this._getEnabledExtensions();
 
         // Find and enable all the newly enabled extensions: UUIDs found in the
         // new setting, but not in the old one.
         newEnabledExtensions.filter(
-            uuid => !this._enabledExtensions.includes(uuid)
+            uuid => !this._enabledExtensions.includes(uuid) &&
+                    this._extensionSupportsSessionMode(uuid)
         ).forEach(uuid => {
             this._callExtensionEnable(uuid);
         });
 
         // Find and disable all the newly disabled extensions: UUIDs found in the
-        // old setting, but not in the new one.
+        // old setting, but not in the new one, and extensions that don't work with
+        // the current session mode.
         this._enabledExtensions.filter(
-            item => !newEnabledExtensions.includes(item)
+            item => !newEnabledExtensions.includes(item) ||
+                    !this._extensionSupportsSessionMode(item)
         ).forEach(uuid => {
             this._callExtensionDisable(uuid);
         });
 
         this._enabledExtensions = newEnabledExtensions;
     }
 
     _onSettingsWritableChanged() {
         for (let extension of this._extensions.values()) {
             this._updateCanChange(extension);
             this.emit('extension-state-changed', extension);
         }
     }
 
     _onVersionValidationChanged() {
         // we want to reload all extensions, but only enable
         // extensions when allowed by the sessionMode, so
         // temporarily disable them all
         this._enabledExtensions = [];
 
         // The loop modifies the extensions map, so iterate over a copy
         let extensions = [...this._extensions.values()];
         for (let extension of extensions)
             this.reloadExtension(extension);
         this._enabledExtensions = this._getEnabledExtensions();
 
         if (Main.sessionMode.allowExtensions) {
             this._enabledExtensions.forEach(uuid => {
                 this._callExtensionEnable(uuid);
             });
-- 
2.27.0