MdeModulePkg/Variable/RuntimeDxe: delete and lock OS-created MOR variable

[mirror_edk2.git] / MdeModulePkg / Universal / Variable / RuntimeDxe / TcgMorLockSmm.c

diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockSmm.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockSmm.c
index faeaabb224afc6fa9214fdc34191e94fce2ee864..93a300a84677618c9bee06c381e6274db37c2802 100644 (file)
--- a/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockSmm.c
+++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/TcgMorLockSmm.c
@@ -21,6 +21,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 #include <Library/DebugLib.h>\r
 #include <Library/BaseLib.h>\r
 #include <Library/BaseMemoryLib.h>\r
+#include <Library/UefiBootServicesTableLib.h>\r
 #include "Variable.h"\r
 \r
 typedef struct {\r
@@ -33,6 +34,8 @@ VARIABLE_TYPE  mMorVariableType[] = {
   {MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,  &gEfiMemoryOverwriteRequestControlLockGuid},\r
 };\r
 \r
+BOOLEAN         mMorPassThru = FALSE;\r
+\r
 #define MOR_LOCK_DATA_UNLOCKED           0x0\r
 #define MOR_LOCK_DATA_LOCKED_WITHOUT_KEY 0x1\r
 #define MOR_LOCK_DATA_LOCKED_WITH_KEY    0x2\r
@@ -362,6 +365,13 @@ SetVariableCheckHandlerMor (
   // Mor Variable\r
   //\r
 \r
+  //\r
+  // Permit deletion for passthru request.\r
+  //\r
+  if (((Attributes == 0) || (DataSize == 0)) && mMorPassThru) {\r
+    return EFI_SUCCESS;\r
+  }\r
+\r
   //\r
   // Basic Check\r
   //\r
@@ -409,6 +419,8 @@ MorLockInitAtEndOfDxe (
 {\r
   UINTN      MorSize;\r
   EFI_STATUS MorStatus;\r
+  EFI_STATUS TcgStatus;\r
+  VOID       *TcgInterface;\r
 \r
   if (!mMorLockInitializationRequired) {\r
     //\r
@@ -437,17 +449,72 @@ MorLockInitAtEndOfDxe (
 \r
   if (MorStatus == EFI_BUFFER_TOO_SMALL) {\r
     //\r
-    // The MOR variable exists; set the MOR Control Lock variable to report the\r
-    // capability to the OS.\r
+    // The MOR variable exists.\r
     //\r
-    SetMorLockVariable (0);\r
-    return;\r
+    // Some OSes don't follow the TCG's Platform Reset Attack Mitigation spec\r
+    // in that the OS should never create the MOR variable, only read and write\r
+    // it -- these OSes (unintentionally) create MOR if the platform firmware\r
+    // does not produce it. Whether this is the case (from the last OS boot)\r
+    // can be deduced from the absence of the TCG / TCG2 protocols, as edk2's\r
+    // MOR implementation depends on (one of) those protocols.\r
+    //\r
+    TcgStatus = gBS->LocateProtocol (\r
+                       &gEfiTcgProtocolGuid,\r
+                       NULL,                 // Registration\r
+                       &TcgInterface\r
+                       );\r
+    if (EFI_ERROR (TcgStatus)) {\r
+      TcgStatus = gBS->LocateProtocol (\r
+                         &gEfiTcg2ProtocolGuid,\r
+                         NULL,                  // Registration\r
+                         &TcgInterface\r
+                         );\r
+    }\r
+\r
+    if (!EFI_ERROR (TcgStatus)) {\r
+      //\r
+      // The MOR variable originates from the platform firmware; set the MOR\r
+      // Control Lock variable to report the locking capability to the OS.\r
+      //\r
+      SetMorLockVariable (0);\r
+      return;\r
+    }\r
+\r
+    //\r
+    // The MOR variable's origin is inexplicable; delete it.\r
+    //\r
+    DEBUG ((\r
+      DEBUG_WARN,\r
+      "%a: deleting unexpected / unsupported variable %g:%s\n",\r
+      __FUNCTION__,\r
+      &gEfiMemoryOverwriteControlDataGuid,\r
+      MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME\r
+      ));\r
+\r
+    mMorPassThru = TRUE;\r
+    VariableServiceSetVariable (\r
+      MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,\r
+      &gEfiMemoryOverwriteControlDataGuid,\r
+      0,                                      // Attributes\r
+      0,                                      // DataSize\r
+      NULL                                    // Data\r
+      );\r
+    mMorPassThru = FALSE;\r
   }\r
 \r
   //\r
-  // The platform does not support the MOR variable. Delete the MOR Control\r
-  // Lock variable (should it exists for some reason) and prevent other modules\r
-  // from creating it.\r
+  // The MOR variable is absent; the platform firmware does not support it.\r
+  // Lock the variable so that no other module may create it.\r
+  //\r
+  VariableLockRequestToLock (\r
+    NULL,                                   // This\r
+    MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,\r
+    &gEfiMemoryOverwriteControlDataGuid\r
+    );\r
+\r
+  //\r
+  // Delete the MOR Control Lock variable too (should it exists for some\r
+  // reason) and prevent other modules from creating it.\r
   //\r
   mMorLockPassThru = TRUE;\r
   VariableServiceSetVariable (\r