Add policy command source

Author: HashidaTKS

BrowserGuard/PolicyCommand.cs

@@ -0,0 +1,128 @@
+using System;
+using System.IO;
+using System.Text.Json.Nodes;
+using Microsoft.Win32;
+
+namespace BrowserGuard
+{
+    // Maintains this extension's entry in the Edge ExtensionSettings policy,
+    // invoked by the installer as a subcommand.
+    //
+    // ExtensionInstallForcelist would only supply the update URL for the first
+    // install; afterwards the browser looks at update_url inside the extension's
+    // own manifest, which a self hosted build does not have. ExtensionSettings
+    // with override_update_url keeps the URL in use for update checks too, which
+    // is why it is used on its own.
+    //
+    // The policy value is one JSON object covering every extension, so it is
+    // parsed and only this extension's member is touched; whatever another
+    // product put there is preserved.
+    internal static class PolicyCommand
+    {
+        internal const string CommandName = "policy";
+
+        // SOFTWARE\Policies is shared between the 32 and 64 bit registry views.
+        private const string PolicyKey = @"SOFTWARE\Policies\Microsoft\Edge";
+        private const string SettingsValue = "ExtensionSettings";
+
+        internal static int Run(string[] args)
+        {
+            try
+            {
+                if (args.Length < 3)
+                {
+                    return Usage();
+                }
+
+                var extensionId = args[2];
+                switch (args[1].ToLowerInvariant())
+                {
+                    case "register":
+                        if (args.Length < 4)
+                        {
+                            return Usage();
+                        }
+                        Register(extensionId, args[3]);
+                        return 0;
+
+                    case "unregister":
+                        Unregister(extensionId);
+                        return 0;
+
+                    default:
+                        return Usage();
+                }
+            }
+            catch (Exception ex)
+            {
+                Console.Error.WriteLine(ex.Message);
+                return 1;
+            }
+        }
+
+        private static int Usage()
+        {
+            Console.Error.WriteLine(
+                $"usage: BrowserGuard.exe {CommandName} register <extension-id> <update-url>\n" +
+                $"       BrowserGuard.exe {CommandName} unregister <extension-id>");
+            return 1;
+        }
+
+        // Separated from the registry access so that it can be exercised by tests.
+        internal static void SetEntry(JsonObject settings, string extensionId, string updateUrl)
+        {
+            settings[extensionId] = new JsonObject
+            {
+                ["installation_mode"] = "force_installed",
+                ["update_url"] = updateUrl,
+                ["override_update_url"] = true,
+            };
+        }
+
+        private static void Register(string extensionId, string updateUrl)
+        {
+            var settings = ReadSettings();
+            SetEntry(settings, extensionId, updateUrl);
+            WriteSettings(settings);
+        }
+
+        private static void Unregister(string extensionId)
+        {
+            var settings = ReadSettings();
+            if (settings.Remove(extensionId))
+            {
+                WriteSettings(settings);
+            }
+        }
+
+        private static JsonObject ReadSettings()
+        {
+            using var key = Registry.LocalMachine.OpenSubKey(PolicyKey);
+            if (key?.GetValue(SettingsValue) is not string raw || string.IsNullOrWhiteSpace(raw))
+            {
+                return new JsonObject();
+            }
+
+            // A value that is not a JSON object cannot be merged into safely.
+            return JsonNode.Parse(raw) as JsonObject
+                ?? throw new InvalidDataException($"{SettingsValue} is not a JSON object.");
+        }
+
+        private static void WriteSettings(JsonObject settings)
+        {
+            using var key = Registry.LocalMachine.CreateSubKey(PolicyKey, true)
+                ?? throw new InvalidOperationException($"Cannot open HKLM\\{PolicyKey} for writing.");
+
+            if (settings.Count == 0)
+            {
+                if (key.GetValue(SettingsValue) is not null)
+                {
+                    key.DeleteValue(SettingsValue);
+                }
+                return;
+            }
+
+            key.SetValue(SettingsValue, settings.ToJsonString(), RegistryValueKind.String);
+        }
+    }
+}