[edk2-devel] [edk2-platforms][PATCH v1 2/2] MinPlatformPkg/TpmPlatformHierarchyLib: Disable TPM platform hierarchy

[Michael Kubacki]

From: Jeremiah Cox <jerecox at microsoft.com>

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3411

Updates the current ConfigureTpmPlatformHierarchy() implementation
to instruct the TPM to disable the platform hierarchy to prevent
later boot/OS code from accessing TPM platform features. This
modifies the current behavior which instead randomizes the platform
auth and then "forgets" it to prevent future platform feature access.

Co-authored-by: Michael Kubacki <michael.kubacki at microsoft.com>
Cc: Chasel Chiu <chasel.chiu at intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone at intel.com>
Cc: Liming Gao <gaoliming at byosoft.com.cn>
Cc: Eric Dong <eric.dong at intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki at microsoft.com>
---
 Platform/Intel/MinPlatformPkg/Tcg/Library/TpmPlatformHierarchyLib/TpmPlatformHierarchyLib.c | 51 ++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/Platform/Intel/MinPlatformPkg/Tcg/Library/TpmPlatformHierarchyLib/TpmPlatformHierarchyLib.c b/Platform/Intel/MinPlatformPkg/Tcg/Library/TpmPlatformHierarchyLib/TpmPlatformHierarchyLib.c
index 41ddb26f4046..bc1dce9b1c51 100644
--- a/Platform/Intel/MinPlatformPkg/Tcg/Library/TpmPlatformHierarchyLib/TpmPlatformHierarchyLib.c
+++ b/Platform/Intel/MinPlatformPkg/Tcg/Library/TpmPlatformHierarchyLib/TpmPlatformHierarchyLib.c
@@ -18,6 +18,7 @@
 #include <Library/BaseMemoryLib.h>
 #include <Library/UefiBootServicesTableLib.h>
 #include <Library/MemoryAllocationLib.h>
+#include <Library/Tpm2DeviceLib.h>
 #include <Library/Tpm2CommandLib.h>
 #include <Library/RngLib.h>
 #include <Library/UefiLib.h>
@@ -197,6 +198,51 @@ RandomizePlatformAuth (
   ZeroMem (Rand, RandSize);
 }
 
+/**
+  Disable the TPM platform hierarchy.
+
+  @retval   EFI_SUCCESS       The TPM was disabled successfully.
+  @retval   Others            An error occurred attempting to disable the TPM platform hierarchy.
+
+**/
+EFI_STATUS
+DisableTpmPlatformHierarchy (
+  VOID
+  )
+{
+  EFI_STATUS  Status;
+
+  // Make sure that we have use of the TPM.
+  Status = Tpm2RequestUseTpm ();
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a:%a() - Tpm2RequestUseTpm Failed! %r\n", gEfiCallerBaseName, __FUNCTION__, Status));
+    ASSERT_EFI_ERROR (Status);
+    return Status;
+  }
+
+  // Let's do what we can to shut down the hierarchies.
+
+  // Disable the PH NV.
+  // IMPORTANT NOTE: We *should* be able to disable the PH NV here, but TPM parts have
+  //                 been known to store the EK cert in the PH NV. If we disable it, the
+  //                 EK cert will be unreadable.
+
+  // Disable the PH.
+  Status =  Tpm2HierarchyControl (
+              TPM_RH_PLATFORM,     // AuthHandle
+              NULL,                // AuthSession
+              TPM_RH_PLATFORM,     // Hierarchy
+              NO                   // State
+              );
+  DEBUG ((DEBUG_VERBOSE, "%a:%a() -  Disable PH = %r\n", gEfiCallerBaseName, __FUNCTION__, Status));
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "%a:%a() -  Disable PH Failed! %r\n", gEfiCallerBaseName, __FUNCTION__, Status));
+    ASSERT_EFI_ERROR (Status);
+  }
+
+  return Status;
+}
+
 /**
    This service defines the configuration of the Platform Hierarchy Authorization Value (platformAuth)
    and Platform Hierarchy Authorization Policy (platformPolicy)
@@ -211,4 +257,9 @@ ConfigureTpmPlatformHierarchy (
   // Send Tpm2HierarchyChange Auth with random value to avoid PlatformAuth being null
   //
   RandomizePlatformAuth ();
+
+  //
+  // Disable the hierarchy entirely (do not randomize it)
+  //
+  DisableTpmPlatformHierarchy ();
 }
-- 
2.28.0.windows.1



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