Measurement.c

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#include <PiDxe.h>
#include <Guid/ImageAuthentication.h>
#include <IndustryStandard/UefiTcgPlatform.h>
 
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/BaseLib.h>
#include <Library/TpmMeasurementLib.h>
 
#include "PrivilegePolymorphic.h"
 
typedef struct {
  CHAR16      *VariableName;
  EFI_GUID    *VendorGuid;
} VARIABLE_TYPE;
 
VARIABLE_TYPE  mVariableType[] = {
  { EFI_SECURE_BOOT_MODE_NAME,    &gEfiGlobalVariableGuid        },
  { EFI_PLATFORM_KEY_NAME,        &gEfiGlobalVariableGuid        },
  { EFI_KEY_EXCHANGE_KEY_NAME,    &gEfiGlobalVariableGuid        },
  { EFI_IMAGE_SECURITY_DATABASE,  &gEfiImageSecurityDatabaseGuid },
  { EFI_IMAGE_SECURITY_DATABASE1, &gEfiImageSecurityDatabaseGuid },
  { EFI_IMAGE_SECURITY_DATABASE2, &gEfiImageSecurityDatabaseGuid },
};
 
//
// "SecureBoot" may update following PK Del/Add
//  Cache its value to detect value update
//
UINT8  *mSecureBootVarData    = NULL;
UINTN  mSecureBootVarDataSize = 0;
 
BOOLEAN
IsSecureBootPolicyVariable (
  IN CHAR16    *VariableName,
  IN EFI_GUID  *VendorGuid
  )
{
  UINTN  Index;
 
  for (Index = 0; Index < sizeof (mVariableType)/sizeof (mVariableType[0]); Index++) {
    if ((StrCmp (VariableName, mVariableType[Index].VariableName) == 0) &&
        (CompareGuid (VendorGuid, mVariableType[Index].VendorGuid)))
    {
      return TRUE;
    }
  }
 
  return FALSE;
}
 
EFI_STATUS
EFIAPI
MeasureVariable (
  IN      CHAR16    *VarName,
  IN      EFI_GUID  *VendorGuid,
  IN      VOID      *VarData,
  IN      UINTN     VarSize
  )
{
  EFI_STATUS          Status;
  UINTN               VarNameLength;
  UEFI_VARIABLE_DATA  *VarLog;
  UINT32              VarLogSize;
 
  ASSERT ((VarSize == 0 && VarData == NULL) || (VarSize != 0 && VarData != NULL));
 
  VarNameLength = StrLen (VarName);
  VarLogSize    = (UINT32)(sizeof (*VarLog) + VarNameLength * sizeof (*VarName) + VarSize
                           - sizeof (VarLog->UnicodeName) - sizeof (VarLog->VariableData));
 
  VarLog = (UEFI_VARIABLE_DATA *)AllocateZeroPool (VarLogSize);
  if (VarLog == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  CopyMem (&VarLog->VariableName, VendorGuid, sizeof (VarLog->VariableName));
  VarLog->UnicodeNameLength  = VarNameLength;
  VarLog->VariableDataLength = VarSize;
  CopyMem (
    VarLog->UnicodeName,
    VarName,
    VarNameLength * sizeof (*VarName)
    );
  if (VarSize != 0) {
    CopyMem (
      (CHAR16 *)VarLog->UnicodeName + VarNameLength,
      VarData,
      VarSize
      );
  }
 
  DEBUG ((DEBUG_INFO, "VariableDxe: MeasureVariable (Pcr - %x, EventType - %x, ", (UINTN)7, (UINTN)EV_EFI_VARIABLE_DRIVER_CONFIG));
  DEBUG ((DEBUG_INFO, "VariableName - %s, VendorGuid - %g)\n", VarName, VendorGuid));
 
  Status = TpmMeasureAndLogData (
             7,
             EV_EFI_VARIABLE_DRIVER_CONFIG,
             VarLog,
             VarLogSize,
             VarLog,
             VarLogSize
             );
  FreePool (VarLog);
  return Status;
}
 
EFI_STATUS
InternalGetVariable (
  IN CONST CHAR16    *Name,
  IN CONST EFI_GUID  *Guid,
  OUT VOID           **Value,
  OUT UINTN          *Size
  )
{
  EFI_STATUS  Status;
  UINTN       BufferSize;
 
  //
  // Try to get the variable size.
  //
  BufferSize = 0;
  *Value     = NULL;
  if (Size != NULL) {
    *Size = 0;
  }
 
  Status = gRT->GetVariable ((CHAR16 *)Name, (EFI_GUID *)Guid, NULL, &BufferSize, *Value);
  if (Status != EFI_BUFFER_TOO_SMALL) {
    return Status;
  }
 
  //
  // Allocate buffer to get the variable.
  //
  *Value = AllocatePool (BufferSize);
  ASSERT (*Value != NULL);
  if (*Value == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  //
  // Get the variable data.
  //
  Status = gRT->GetVariable ((CHAR16 *)Name, (EFI_GUID *)Guid, NULL, &BufferSize, *Value);
  if (EFI_ERROR (Status)) {
    FreePool (*Value);
    *Value = NULL;
  }
 
  if (Size != NULL) {
    *Size = BufferSize;
  }
 
  return Status;
}
 
VOID
EFIAPI
SecureBootHook (
  IN CHAR16    *VariableName,
  IN EFI_GUID  *VendorGuid
  )
{
  EFI_STATUS  Status;
  UINTN       VariableDataSize;
  VOID        *VariableData;
 
  if (!IsSecureBootPolicyVariable (VariableName, VendorGuid)) {
    return;
  }
 
  //
  // We should NOT use Data and DataSize here,because it may include signature,
  // or is just partial with append attributes, or is deleted.
  // We should GetVariable again, to get full variable content.
  //
  Status = InternalGetVariable (
             VariableName,
             VendorGuid,
             &VariableData,
             &VariableDataSize
             );
  if (EFI_ERROR (Status)) {
    //
    // Measure DBT only if present and not empty
    //
    if ((StrCmp (VariableName, EFI_IMAGE_SECURITY_DATABASE2) == 0) &&
        CompareGuid (VendorGuid, &gEfiImageSecurityDatabaseGuid))
    {
      DEBUG ((DEBUG_INFO, "Skip measuring variable %s since it's deleted\n", EFI_IMAGE_SECURITY_DATABASE2));
      return;
    } else {
      VariableData     = NULL;
      VariableDataSize = 0;
    }
  }
 
  Status = MeasureVariable (
             VariableName,
             VendorGuid,
             VariableData,
             VariableDataSize
             );
  DEBUG ((DEBUG_INFO, "MeasureBootPolicyVariable - %r\n", Status));
 
  if (VariableData != NULL) {
    FreePool (VariableData);
  }
 
  //
  // "SecureBoot" is 8bit & read-only. It can only be changed according to PK update
  //
  if ((StrCmp (VariableName, EFI_PLATFORM_KEY_NAME) == 0) &&
      CompareGuid (VendorGuid, &gEfiGlobalVariableGuid))
  {
    Status = InternalGetVariable (
               EFI_SECURE_BOOT_MODE_NAME,
               &gEfiGlobalVariableGuid,
               &VariableData,
               &VariableDataSize
               );
    if (EFI_ERROR (Status)) {
      return;
    }
 
    //
    // If PK update is successful. "SecureBoot" shall always exist ever since variable write service is ready
    //
    ASSERT (mSecureBootVarData != NULL);
 
    if (CompareMem (mSecureBootVarData, VariableData, VariableDataSize) != 0) {
      FreePool (mSecureBootVarData);
      mSecureBootVarData     = VariableData;
      mSecureBootVarDataSize = VariableDataSize;
 
      DEBUG ((DEBUG_INFO, "%s variable updated according to PK change. Remeasure the value!\n", EFI_SECURE_BOOT_MODE_NAME));
      Status = MeasureVariable (
                 EFI_SECURE_BOOT_MODE_NAME,
                 &gEfiGlobalVariableGuid,
                 mSecureBootVarData,
                 mSecureBootVarDataSize
                 );
      DEBUG ((DEBUG_INFO, "MeasureBootPolicyVariable - %r\n", Status));
    } else {
      //
      // "SecureBoot" variable is not changed
      //
      FreePool (VariableData);
    }
  }
 
  return;
}
 
VOID
EFIAPI
RecordSecureBootPolicyVarData (
  VOID
  )
{
  EFI_STATUS  Status;
 
  //
  // Record initial "SecureBoot" variable value.
  // It is used to detect SecureBoot variable change in SecureBootHook.
  //
  Status = InternalGetVariable (
             EFI_SECURE_BOOT_MODE_NAME,
             &gEfiGlobalVariableGuid,
             (VOID **)&mSecureBootVarData,
             &mSecureBootVarDataSize
             );
  if (EFI_ERROR (Status)) {
    //
    // Read could fail when Auth Variable solution is not supported
    //
    DEBUG ((DEBUG_INFO, "RecordSecureBootPolicyVarData GetVariable %s Status %x\n", EFI_SECURE_BOOT_MODE_NAME, Status));
  }
}