Create an own entry, don't replace MS boot loader

README.md

@@ -28,6 +28,8 @@ When booting on a UEFI-based computer, Windows may show a vendor-defined logo wh
 * Edit the `config.txt` and `splash.bmp` (or any other images) to your needs.
 * Run `setup.exe batch COMMANDS` as administrator, with some of the following commands:
 	* `install` – copy the files but don't enable.
+	* `enable-entry` – create a new EFI boot entry.
+	* `disable-entry` – disable the EFI boot entry.
 	* `enable-overwrite` – overwrite the MS boot loader.
 	* `disable-overwrite` – restore the MS boot loader.
 	* `allow-secure-boot` – ignore Secure Boot in subsequent commands.
@@ -45,8 +47,7 @@ If you only need HackBGRT for Windows:
 If you need it for other systems as well:
 
 * Configure HackBGRT to start your boot loader (such as systemd-boot): `boot=\EFI\systemd\systemd-bootx64.efi`.
-* Run `setup.exe`, install files.
+* Run `setup.exe`, install as a new EFI boot entry.
-* Set `\EFI\HackBGRT\loader.efi` as your default boot loader with `efibootmgr` or some other EFI boot manager tool.
 
 To install purely on Linux, you can install with `setup.exe dry-run` and then manually copy files from `dry-run/EFI` to your `[EFI System Partition]/EFI`. For further instructions, consult the documentation of your own Linux system.
 
@@ -64,10 +65,7 @@ Advanced users may edit the `config.txt` to define multiple images, in which cas
 
 ## Recovery
 
-If something breaks and you can't boot to Windows, you have the following options:
+If something breaks and you can't boot to Windows, you need to use the Windows installation disk (or recovery disk) to fix boot issues.
-
-* Windows installation (or recovery) media can fix boot issues.
-* You can copy `[EFI System Partition]\EFI\HackBGRT\bootmgfw-original.efi` into `[EFI System Partition]\EFI\Microsoft\Boot\bootmgfw.efi` by some other means such as Linux or Windows command prompt.
 
 ## Building
 

config.txt

@@ -1,8 +1,8 @@
 # vim: set fileencoding=utf-8
 # The same options may be given also as command line parameters in the EFI Shell, which is useful for debugging.
 
-# Boot loader path. Default: backup of the Windows boot loader.
+# Boot loader path. MS = either backup or original Windows boot loader.
-boot=\EFI\HackBGRT\bootmgfw-original.efi
+boot=MS
 
 # The image is specified with an image line.
 # Multiple image lines may be present, in which case one will be picked by random.

src/Efi.cs

@@ -1,4 +1,7 @@
 using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
 using System.Linq;
 using System.Runtime.InteropServices;
 using Microsoft.Win32;
@@ -42,6 +45,92 @@ public class Efi {
 		public string Name, Guid;
 		public UInt32 Attributes;
 		public byte[] Data;
+
+		/**
+		 * Convert to string.
+		 *
+		 * @return String representation of this object.
+		 */
+		public override string ToString() {
+			var hex = BitConverter.ToString(Data).Replace("-", " ");
+			var text = new string(Data.Select(c => 0x20 <= c && c <= 0x7f ? (char) c : ' ').ToArray());
+			return $"{Name} Guid={Guid} Attributes={Attributes} Text='{text}' Bytes='{hex}'";
+		}
+	}
+
+	/**
+	 * Information about an EFI boot entry.
+	 */
+	public class BootEntryData {
+		public UInt32 Attributes;
+		public string Label;
+		public class DevicePathNode {
+			public byte Type, SubType;
+			public byte[] Data;
+			public DevicePathNode(byte[] data) {
+				Type = data[0];
+				SubType = data[1];
+				Data = data.Skip(4).ToArray();
+			}
+			public byte[] ToBytes() {
+				var len = Data.Length + 4;
+				return new byte[] { Type, SubType, (byte)(len & 0xff), (byte)(len >> 8) }.Concat(Data).ToArray();
+			}
+		}
+		public List<DevicePathNode> DevicePathNodes;
+		public byte[] Arguments;
+
+		public BootEntryData(byte[] data) {
+			Attributes = BitConverter.ToUInt32(data, 0);
+			var pathNodesLength = BitConverter.ToUInt16(data, 4);
+			Label = new string(BytesToUInt16s(data).Skip(3).TakeWhile(i => i != 0).Select(i => (char)i).ToArray());
+			var pos = 6 + 2 * (Label.Length + 1);
+			var pathNodesEnd = pos + pathNodesLength;
+			DevicePathNodes = new List<DevicePathNode>();
+			while (pos + 4 <= pathNodesEnd) {
+				var len = BitConverter.ToUInt16(data, pos + 2);
+				if (len < 4 || pos + len > pathNodesEnd) {
+					return; // throw new Exception("Bad entry.");
+				}
+				DevicePathNodes.Add(new DevicePathNode(data.Skip(pos).Take(len).ToArray()));
+				pos += len;
+			}
+			Arguments = data.Skip(pathNodesEnd).ToArray();
+		}
+		public byte[] ToBytes() {
+			return new byte[0]
+				.Concat(BitConverter.GetBytes((UInt32) Attributes))
+				.Concat(BitConverter.GetBytes((UInt16) DevicePathNodes.Sum(n => n.Data.Length + 4)))
+				.Concat(Encoding.Unicode.GetBytes(Label + "\0"))
+				.Concat(DevicePathNodes.SelectMany(n => n.ToBytes()))
+				.Concat(Arguments)
+				.ToArray();
+		}
+		public DevicePathNode FileNameNode {
+			get {
+				var d = DevicePathNodes;
+				return d.Count > 1 && d[d.Count - 1].Type == 0x7F && d[d.Count - 2].Type == 0x04 ? d[d.Count - 2] : null;
+			}
+		}
+		public bool HasFileName {
+			get {
+				return FileNameNode != null;
+			}
+		}
+		public string FileName {
+			get {
+				if (!HasFileName) {
+					return "";
+				}
+				return new string(Encoding.Unicode.GetChars(FileNameNode.Data).TakeWhile(c => c != '\0').ToArray());
+			}
+			set {
+				if (!HasFileName) {
+					throw new Exception("Logic error: Setting FileName on a bad boot entry.");
+				}
+				FileNameNode.Data = Encoding.Unicode.GetBytes(value + "\0");
+			}
+		}
 	}
 
 	public const string EFI_GLOBAL_GUID = "{8be4df61-93ca-11d2-aa0d-00e098032b8c}";
@@ -117,17 +206,23 @@ public class Efi {
 	 * Set an EFI variable.
 	 *
 	 * @param v Information of the variable.
+	 * @param dryRun Don't actually set the variable.
 	 */
-	private static void SetVariable(Variable v) {
+	private static void SetVariable(Variable v, bool dryRun = false) {
+		Console.WriteLine($"Writing EFI variable {v}");
+		if (dryRun) {
+			return;
+		}
+
 		UInt32 r = SetFirmwareEnvironmentVariableEx(v.Name, v.Guid, v.Data, (UInt32) v.Data.Length, v.Attributes);
 		if (r == 0) {
 			switch (Marshal.GetLastWin32Error()) {
 				case 87:
-					throw new Exception("GetVariable: Invalid parameter");
+					throw new Exception("SetVariable: Invalid parameter");
 				case 1314:
-					throw new Exception("GetVariable: Privilege not held");
+					throw new Exception("SetVariable: Privilege not held");
 				default:
-					throw new Exception("GetVariable: error " + Marshal.GetLastWin32Error());
+					throw new Exception("SetVariable: error " + Marshal.GetLastWin32Error());
 			}
 		}
 	}
@@ -177,4 +272,136 @@ public class Efi {
 		tmp.Data[0] |= 1;
 		SetVariable(tmp);
 	}
+
+	/**
+	 * Convert bytes into UInt16 values.
+	 *
+	 * @param bytes The byte array.
+	 * @return An enumeration of UInt16 values.
+	 */
+	public static IEnumerable<UInt16> BytesToUInt16s(byte[] bytes) {
+		// TODO: return bytes.Chunk(2).Select(b => (UInt16) (b[0] + 0x100 * b[1])).ToArray();
+		return Enumerable.Range(0, bytes.Length / 2).Select(i => (UInt16) (bytes[2 * i] + 0x100 * bytes[2 * i + 1]));
+	}
+
+	/**
+	 * Disable the said boot entry from BootOrder.
+	 *
+	 * @param label Label of the boot entry.
+	 * @param fileName File name of the boot entry.
+	 * @param dryRun Don't actually disable the entry.
+	 * @return True, if the entry was found in BootOrder.
+	 */
+	public static bool DisableBootEntry(string label, string fileName, bool dryRun = false) {
+		Variable bootOrder;
+		try {
+			bootOrder = GetVariable("BootOrder");
+		} catch {
+			return false;
+		}
+		if (bootOrder.Data == null) {
+			return false;
+		}
+		var found = false;
+		var bootOrderInts = new List<UInt16>();
+		foreach (var num in BytesToUInt16s(bootOrder.Data)) {
+			var entry = GetVariable(String.Format("Boot{0:X04}", num));
+			if (entry.Data != null) {
+				var entryData = new BootEntryData(entry.Data);
+				if (entryData.Label == label && entryData.FileName == fileName) {
+					found = true;
+					continue;
+				}
+			}
+			bootOrderInts.Add(num);
+		}
+		if (found) {
+			bootOrder.Data = bootOrderInts.SelectMany(num => new byte[] { (byte)(num & 0xff), (byte)(num >> 8) }).ToArray();
+			SetVariable(bootOrder, dryRun);
+		}
+		return found;
+	}
+
+	/**
+	 * Create and enable the said boot entry from BootOrder.
+	 *
+	 * @param label Label of the boot entry.
+	 * @param fileName File name of the boot entry.
+	 * @param dryRun Don't actually create the entry.
+	 */
+	public static void MakeAndEnableBootEntry(string label, string fileName, bool dryRun = false) {
+		Variable msEntry = null, ownEntry = null;
+		UInt16 msNum = 0, ownNum = 0;
+
+		// Find a free entry and the MS bootloader entry.
+		Variable bootOrder = null;
+		try {
+			bootOrder = GetVariable("BootOrder");
+		} catch {
+			if (dryRun) {
+				return;
+			}
+		}
+		if (bootOrder == null || bootOrder.Data == null) {
+			throw new Exception("MakeBootEntry: Could not read BootOrder. Maybe your computer is defective.");
+		}
+		var bootCurrent = GetVariable("BootCurrent");
+		if (bootCurrent.Data == null) {
+			throw new Exception("MakeBootEntry: Could not read BootCurrent. Maybe your computer is defective.");
+		}
+		var bootOrderInts = new List<UInt16>(BytesToUInt16s(bootOrder.Data));
+		foreach (var num in BytesToUInt16s(bootCurrent.Data).Concat(bootOrderInts).Concat(Enumerable.Range(0, 0xffff).Select(i => (UInt16) i))) {
+			var entry = GetVariable(String.Format("Boot{0:X04}", num));
+			if (entry.Data == null) {
+				if (ownEntry == null) {
+					ownNum = num;
+					ownEntry = entry;
+				}
+			} else {
+				var entryData = new BootEntryData(entry.Data);
+				if (!entryData.HasFileName) {
+					continue;
+				}
+				if (entryData.Label == label && entryData.FileName == fileName) {
+					ownNum = num;
+					ownEntry = entry;
+				}
+				if (msEntry == null && entryData.FileName.StartsWith("\\EFI\\Microsoft\\Boot\\bootmgfw.efi", StringComparison.OrdinalIgnoreCase)) {
+					msNum = num;
+					msEntry = entry;
+				}
+			}
+			if (ownEntry != null && msEntry != null) {
+				break;
+			}
+		}
+		if (ownEntry == null) {
+			throw new Exception("MakeBootEntry: Boot entry list is full.");
+		} else if (msEntry == null) {
+			throw new Exception("MakeBootEntry: Windows Boot Manager not found.");
+		} else {
+			// Make a new boot entry using the MS entry as a starting point.
+			var entryData = new BootEntryData(msEntry.Data);
+			entryData.Arguments = Encoding.UTF8.GetBytes(label + "\0");
+			entryData.Attributes = 1; // LOAD_OPTION_ACTIVE
+			entryData.Label = label;
+			entryData.FileName = fileName;
+			ownEntry.Attributes = 7; // EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS
+			ownEntry.Data = entryData.ToBytes();
+			SetVariable(ownEntry, dryRun);
+		}
+
+		var msPos = bootOrderInts.IndexOf(msNum);
+		var ownPos = bootOrderInts.IndexOf(ownNum);
+		var mustAdd = ownPos == -1;
+		var mustMove = 0 <= msPos && msPos <= ownPos;
+		if (mustAdd || mustMove) {
+			if (mustMove) {
+				bootOrderInts.RemoveAt(ownPos);
+			}
+			bootOrderInts.Insert(msPos < 0 ? 0 : msPos, ownNum);
+			bootOrder.Data = bootOrderInts.SelectMany(num => new byte[] { (byte)(num & 0xff), (byte)(num >> 8) }).ToArray();
+			SetVariable(bootOrder, dryRun);
+		}
+	}
 }

src/Setup.cs

@@ -41,6 +41,7 @@ public class Setup: SetupHelper {
 	protected static readonly string[] privilegedActions = new string[] {
 		"install",
 		"allow-secure-boot",
+		"enable-entry", "disable-entry",
 		"enable-overwrite", "disable-overwrite",
 		"disable",
 		"uninstall",
@@ -219,6 +220,22 @@ public class Setup: SetupHelper {
 		Console.WriteLine($"HackBGRT has been copied to {InstallPath}.");
 	}
 
+	/**
+	 * Enable HackBGRT boot entry.
+	 */
+	protected void EnableEntry() {
+		Efi.MakeAndEnableBootEntry("HackBGRT", "\\EFI\\HackBGRT\\loader.efi", DryRun);
+		Console.WriteLine("Enabled NVRAM entry for HackBGRT.");
+	}
+
+	/**
+	 * Disable HackBGRT boot entry.
+	 */
+	protected void DisableEntry() {
+		Efi.DisableBootEntry("HackBGRT", "\\EFI\\HackBGRT\\loader.efi", DryRun);
+		Console.WriteLine("Disabled NVRAM entry for HackBGRT.");
+	}
+
 	/**
 	 * Enable HackBGRT by overwriting the MS boot loader.
 	 */
@@ -248,6 +265,7 @@ public class Setup: SetupHelper {
 	protected void RestoreMsLoader() {
 		var MsLoader = new BootLoaderInfo(Esp.MsLoaderPath);
 		if (MsLoader.Type == BootLoaderType.Own) {
+			Console.WriteLine("Disabling an old version of HackBGRT.");
 			var MsLoaderBackup = new BootLoaderInfo(BackupLoaderPath);
 			if (!MsLoader.ReplaceWith(MsLoaderBackup)) {
 				throw new SetupException("Couldn't restore the old MS loader.");
@@ -281,6 +299,7 @@ public class Setup: SetupHelper {
 	 */
 	protected void Uninstall() {
 		RestoreMsLoader();
+		DisableEntry();
 		try {
 			Directory.Delete(InstallPath, true);
 			Console.WriteLine($"HackBGRT has been removed from {InstallPath}.");
@@ -359,18 +378,30 @@ public class Setup: SetupHelper {
 	protected void ShowMenu() {
 		Console.WriteLine();
 		Console.WriteLine("Choose action (press a key):");
-		Console.WriteLine(" I = install, enable, upgrade, repair, modify");
+		Console.WriteLine(" I = install");
-		Console.WriteLine(" F = install files only, don't enable");
+		Console.WriteLine("     - creates a new EFI boot entry for HackBGRT");
-		Console.WriteLine(" D = disable, restore the original boot loader");
+		Console.WriteLine("     - sometimes needs to be enabled in firmware settings");
-		Console.WriteLine(" R = remove completely; delete all HackBGRT files and images");
+		Console.WriteLine("     - should fall back to MS boot loader if HackBGRT fails");
+		Console.WriteLine(" O = install (legacy)");
+		Console.WriteLine("     - overwrites the MS boot loader");
+		Console.WriteLine("     - may require re-install after Windows updates");
+		Console.WriteLine("     - could brick your system if configured incorrectly");
+		Console.WriteLine(" F = install files only");
+		Console.WriteLine("     - needs to be enabled somehow");
+		Console.WriteLine(" D = disable");
+		Console.WriteLine("     - removes created entries, restores MS boot loader");
+		Console.WriteLine(" R = remove completely");
+		Console.WriteLine("     - disables, then deletes all files and images");
 		Console.WriteLine(" C = cancel");
 
 		var k = Console.ReadKey().Key;
 		Console.WriteLine();
-		if (k == ConsoleKey.I || k == ConsoleKey.F) {
+		if (k == ConsoleKey.I || k == ConsoleKey.O || k == ConsoleKey.F) {
 			Configure();
 		}
 		if (k == ConsoleKey.I) {
+			RunPrivilegedActions(new string[] { "install", "enable-entry" });
+		} else if (k == ConsoleKey.O) {
 			RunPrivilegedActions(new string[] { "install", "enable-overwrite" });
 		} else if (k == ConsoleKey.F) {
 			RunPrivilegedActions(new string[] { "install" });
@@ -417,6 +448,11 @@ public class Setup: SetupHelper {
 				InstallFiles();
 			} else if (arg == "allow-secure-boot") {
 				allowSecureBoot = true;
+			} else if (arg == "enable-entry") {
+				HandleSecureBoot(allowSecureBoot);
+				EnableEntry();
+			} else if (arg == "disable-entry") {
+				DisableEntry();
 			} else if (arg == "enable-overwrite") {
 				HandleSecureBoot(allowSecureBoot);
 				OverwriteMsLoader();
@@ -424,6 +460,7 @@ public class Setup: SetupHelper {
 				RestoreMsLoader();
 			} else if (arg == "disable") {
 				RestoreMsLoader();
+				DisableEntry();
 			} else if (arg == "uninstall") {
 				Uninstall();
 			} else {

src/main.c

@@ -323,6 +323,19 @@ void HackBgrt(EFI_FILE_HANDLE root_dir) {
 	HandleAcpiTables(HackBGRT_REPLACE, bgrt);
 }
 
+/**
+ * Load an application.
+ */
+static EFI_HANDLE LoadApp(print_t* print_failure, EFI_HANDLE image_handle, EFI_LOADED_IMAGE* image, const CHAR16* path) {
+	EFI_DEVICE_PATH* boot_dp = FileDevicePath(image->DeviceHandle, (CHAR16*) path);
+	EFI_HANDLE result = 0;
+	Debug(L"HackBGRT: Loading application %s.\n", path);
+	if (EFI_ERROR(BS->LoadImage(0, image_handle, boot_dp, 0, 0, &result))) {
+		print_failure(L"HackBGRT: Failed to load application %s.\n", path);
+	}
+	return result;
+}
+
 /**
  * The main program.
  */
@@ -356,29 +369,34 @@ EFI_STATUS EFIAPI EfiMain(EFI_HANDLE image_handle, EFI_SYSTEM_TABLE *ST_) {
 	HackBgrt(root_dir);
 
 	EFI_HANDLE next_image_handle = 0;
-	if (!config.boot_path) {
+	static CHAR16 backup_boot_path[] = L"\\EFI\\HackBGRT\\bootmgfw-original.efi";
-		Print(L"HackBGRT: Boot path not specified.\n");
+	static CHAR16 ms_boot_path[] = L"\\EFI\\Microsoft\\Boot\\bootmgfw.efi";
+
+	if (config.boot_path && StriCmp(config.boot_path, L"MS") != 0) {
+		next_image_handle = LoadApp(Print, image_handle, image, config.boot_path);
 	} else {
-		Debug(L"HackBGRT: Loading application %s.\n", config.boot_path);
+		config.boot_path = backup_boot_path;
-		EFI_DEVICE_PATH* boot_dp = FileDevicePath(image->DeviceHandle, (CHAR16*) config.boot_path);
+		next_image_handle = LoadApp(Debug, image_handle, image, config.boot_path);
-		if (EFI_ERROR(BS->LoadImage(0, image_handle, boot_dp, 0, 0, &next_image_handle))) {
+		if (!next_image_handle) {
-			Print(L"HackBGRT: Failed to load application %s.\n", config.boot_path);
+			config.boot_path = ms_boot_path;
+			next_image_handle = LoadApp(Debug, image_handle, image, config.boot_path);
 		}
 	}
 	if (!next_image_handle) {
-		static CHAR16 default_boot_path[] = L"\\EFI\\HackBGRT\\bootmgfw-original.efi";
+		config.boot_path = backup_boot_path;
-		Debug(L"HackBGRT: Loading application %s.\n", default_boot_path);
+		next_image_handle = LoadApp(Print, image_handle, image, config.boot_path);
-		EFI_DEVICE_PATH* boot_dp = FileDevicePath(image->DeviceHandle, default_boot_path);
+		if (!next_image_handle) {
-		if (EFI_ERROR(BS->LoadImage(0, image_handle, boot_dp, 0, 0, &next_image_handle))) {
+			config.boot_path = ms_boot_path;
-			Print(L"HackBGRT: Also failed to load application %s.\n", default_boot_path);
+			next_image_handle = LoadApp(Print, image_handle, image, config.boot_path);
-			goto fail;
+			if (!next_image_handle) {
+				goto fail;
+			}
 		}
-		Print(L"HackBGRT: Reverting to %s.\n", default_boot_path);
+		Print(L"HackBGRT: Reverting to %s.\n", config.boot_path);
 		Print(L"Press escape to cancel, any other key to boot.\n");
 		if (ReadKey().ScanCode == SCAN_ESC) {
 			goto fail;
 		}
-		config.boot_path = default_boot_path;
 	}
 	if (config.debug) {
 		Print(L"HackBGRT: Ready to boot.\nPress escape to cancel, any other key to boot.\n");