Try to detect and add an alert for 'TPM Measured Boot' with BitLocker

* Per https://github.com/microsoft/secureboot_objects/wiki/OEM-Certificate-Key-Rolling#update-factory-defaults-for-oems:
  "Modifying (PK/KEK/db/dbx) will break full disk encryption because they are key components of SRTM PCR measurements".
* As a result, we try to detect the present of a TPM along with BitLocker encrypted partitions, and add a notice that
  users may need to provide their recovery key for Windows to boot, once the Secure Boot variables have been altered.
* Closes #18.
* Also improve the alert boxes and prevent the NoPk creation in update mode.

Author: pbatard

MosbyPkg.inf

@@ -66,9 +66,11 @@
   gEfiSmbios3TableGuid
 
 [Protocols]
+  gEfiBlockIoProtocolGuid
   gEfiLoadedImageProtocolGuid
   gEfiSimpleFileSystemProtocolGuid
   gEfiRngProtocolGuid
+  gEfiTcg2ProtocolGuid
 
 [Pcd]
   gEfiMdePkgTokenSpaceGuid.PcdUefiVariableDefaultLang

src/console.c

@@ -332,13 +332,15 @@ INTN ConsoleOkCancel(
 	return ConsoleSelect(StrArray, (CONST CHAR16 *[]){ L"OK", L"Cancel", NULL }, 0);
 }
 
-VOID ConsoleAlertBox(
-	IN CONST CHAR16 *StrArray[]
+INTN ConsoleAlertBox(
+	IN CONST CHAR16 *StrArray[],
+	IN CONST CHAR16 *Selectors[]
 )
 {
 	BackGroundColor = EFI_BACKGROUND_RED;
-	ConsoleSelect(StrArray, (CONST CHAR16 *[]){ L"OK", 0 }, 0);
+	INTN Sel = ConsoleSelect(StrArray, Selectors, 100000);
 	BackGroundColor = DEFAULT_BACKGROUND_COLOR;
+	return Sel;
 }
 
 VOID ConsoleErrorBox(
@@ -355,7 +357,7 @@ VOID ConsoleErrorBox(
 	ErrArray[2] = Err;
 
 	BackGroundColor = EFI_BACKGROUND_RED;
-	ConsoleAlertBox(ErrArray);
+	ConsoleAlertBox(ErrArray, (CONST CHAR16 *[]){ L"OK", NULL });
 	BackGroundColor = DEFAULT_BACKGROUND_COLOR;
 }
 
@@ -377,7 +379,7 @@ VOID ConsoleError(
 	ErrArray[2] = Str;
 
 	BackGroundColor = EFI_BACKGROUND_RED;
-	ConsoleAlertBox(ErrArray);
+	ConsoleAlertBox(ErrArray, (CONST CHAR16 *[]){ L"OK", NULL });
 	BackGroundColor = DEFAULT_BACKGROUND_COLOR;
 }
 

src/console.h

@@ -65,8 +65,9 @@ INTN ConsoleOkCancel(
 	IN CONST CHAR16 *StrArray[]
 );
 
-VOID ConsoleAlertBox(
-	IN CONST CHAR16 *StrArray[]
+INTN ConsoleAlertBox(
+	IN CONST CHAR16 *StrArray[],
+	IN CONST CHAR16 *Selectors[]
 );
 
 VOID ConsoleErrorBox(

src/mosby.c

@@ -361,6 +361,32 @@ EFI_STATUS EFIAPI efi_main(
 		RecallPrintRestore();
 		if (Sel != 0)
 			goto exit;
+
+		/* Display an additional warning for TPM measured boot with BitLocker */
+		if (SystemHasTpm() && SystemHasBitLocker()) {
+			RecallPrint(L"Notice: TPM and BitLocker detected.\n");
+			STATIC CONST CHAR16 *WTF_RISC_COMPILER1[] = {
+				L"TPM MEASURED BOOT WARNING",
+				L"",
+				L"A TPM, along with BitLocker partitions, were detected on this PC.",
+				L"",
+				L"Because of a feature called 'TPM Measured Boot', if  your  system",
+				L"partition is encrypted, this could result in Windows refusing  to",
+				L"boot after the Secure Boot variables have been updated, until you",
+				L"provide it with your BitLocker recovery key...                   ",
+				L"",
+				L"If you have your recovery key available, or are  sure  that  your",
+				L"system partition is not encrypted, you can select 'Proceed' here.",
+				L"",
+				L"If you are unsure about the above, and don't have your  BitLocker",
+				L"recovery key, it is recommended that you select 'Abort'.         ",
+				NULL
+			};
+			Sel = ConsoleAlertBox(WTF_RISC_COMPILER1, (CONST CHAR16 *[]){ L"PROCEED", L"ABORT", NULL });
+			RecallPrintRestore();
+			if (Sel != 0)
+				goto exit;
+		}
 	}
 
 	/* If we have an existing cert for a previously generated DB credential, try to reuse it */
@@ -642,7 +668,7 @@ EFI_STATUS EFIAPI efi_main(
 
 	// If requested, create a NoPK.auth package, that can be used (with KeyTool or other utilities)
 	// to delete the PK and set the platform back into Setup Mode.
-	if (CreateNoPkFile) {
+	if (CreateNoPkFile && !UpdateMode) {
 		MOSBY_VARIABLE NoPk = { 0 };
 		if (SimpleFileExistsByPath(gBaseImageHandle, L"NoPK.auth")) {
 			RecallPrint(L"WARNING: NOT creating a PK deletion package since 'NoPK.auth' already exists\n");
@@ -667,11 +693,11 @@ EFI_STATUS EFIAPI efi_main(
 		Reboot = ExitNotice(GenDBCred);
 
 exit:
-	if (EFI_ERROR(Status) && DisplayErrorNotice && !gOptionSilent) {
+	if (EFI_ERROR(Status) && DisplayErrorNotice && !gOptionSilent && !UpdateMode) {
 		// The RISC-V gcc compiler adds implicit memcpy() calls here if you declare the text
 		// blurb inline, *LIKE WE DO EVERYWHERE ELSE ABOVE WITHOUT ISSUE*, which of course
 		// breaks UEFI app compilation. So we have to declare a static variable. WTF?!?
-		STATIC CONST CHAR16 *WTF_RISC_COMPILER[] = {
+		STATIC CONST CHAR16 *WTF_RISC_COMPILER2[] = {
 			L"ERROR",
 			L"",
 			L"Mosby was NOT able to install your Secure Boot variables.        ",
@@ -686,7 +712,7 @@ EFI_STATUS EFIAPI efi_main(
 			L"",
 			NULL
 		};
-		ConsoleAlertBox(WTF_RISC_COMPILER);
+		ConsoleAlertBox(WTF_RISC_COMPILER2, (CONST CHAR16 *[]){ L"OK", NULL });
 		RecallPrintRestore();
 	}
 	for (i = 0; i < List.Size; i++)

src/mosby.h

@@ -158,3 +158,7 @@ EFI_STATUS InitializeList(
 );
 
 EFI_STATUS PrintSystemInfo(VOID);
+
+BOOLEAN SystemHasTpm(VOID);
+
+BOOLEAN SystemHasBitLocker(VOID);

src/system.c

@@ -1,6 +1,6 @@
 /*
  * MSSB (More Secure Secure Boot -- "Mosby") UEFI system info
- * Copyright © 2025 Pete Batard <pete@akeo.ie>
+ * Copyright © 2025-2026 Pete Batard <pete@akeo.ie>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -30,6 +30,9 @@
 
 #include <IndustryStandard/SmBios.h>
 
+#include <Protocol/BlockIo.h>
+#include <Protocol/Tcg2Protocol.h>
+
 #include <Uefi/UefiBaseType.h>
 
 /*
@@ -139,3 +142,44 @@ EFI_STATUS PrintSystemInfo(VOID)
 
 	return EFI_SUCCESS;
 }
+
+BOOLEAN SystemHasTpm(VOID)
+{
+	EFI_TCG2_PROTOCOL *Tcg2;
+	
+	return !EFI_ERROR(gBS->LocateProtocol(&gEfiTcg2ProtocolGuid, NULL, (VOID **)&Tcg2));
+}
+
+BOOLEAN SystemHasBitLocker(VOID)
+{
+	BOOLEAN Found = FALSE;
+	EFI_STATUS Status;
+	EFI_HANDLE *Handles = NULL;
+	EFI_BLOCK_IO_PROTOCOL *BlockIo = NULL;
+	UINTN HandleCount, i;
+	UINT8 *Sector = NULL;
+
+	Status = gBS->LocateHandleBuffer(ByProtocol, &gEfiBlockIoProtocolGuid, NULL, &HandleCount, &Handles);
+	if (EFI_ERROR(Status))
+		return FALSE;
+
+	for (i = 0; i < HandleCount && !Found; i++) {
+		Status = gBS->HandleProtocol(Handles[i], &gEfiBlockIoProtocolGuid, (VOID **)&BlockIo);
+		if (EFI_ERROR(Status) || !BlockIo->Media->LogicalPartition || !BlockIo->Media->MediaPresent)
+			continue;
+
+		// Read the first sector, and look for the BitLocker "Full Volume Encryption File System" magic
+		Sector = AllocateZeroPool(BlockIo->Media->BlockSize);
+		if (Sector == NULL)
+			continue;
+		Status = BlockIo->ReadBlocks(BlockIo, BlockIo->Media->MediaId, 0, BlockIo->Media->BlockSize, Sector);
+		if (EFI_ERROR(Status))
+			continue;
+		if (CompareMem(&Sector[3], "-FVE-FS-", 8) == 0)
+			Found = TRUE;
+		FreePool(Sector);
+	}
+
+	FreePool(Handles);
+	return Found;
+}