SecureBootVariableLib.c

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#include <Uefi.h>
#include <UefiSecureBoot.h>
#include <Guid/GlobalVariable.h>
#include <Guid/AuthenticatedVariableFormat.h>
#include <Guid/ImageAuthentication.h>
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/UefiLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>
#include <Library/SecureBootVariableLib.h>
#include <Library/PlatformPKProtectionLib.h>
 
// This time can be used when deleting variables, as it should be greater than any variable time.
EFI_TIME  mMaxTimestamp = {
  0xFFFF,     // Year
  0xFF,       // Month
  0xFF,       // Day
  0xFF,       // Hour
  0xFF,       // Minute
  0xFF,       // Second
  0x00,
  0x00000000, // Nanosecond
  0,
  0,
  0x00
};
 
//
// This epoch time is the date that is used when creating SecureBoot default variables.
// NOTE: This is a placeholder date that doesn't correspond to anything else.
//
EFI_TIME  mDefaultPayloadTimestamp = {
  1970, // Year (1970)
  1,    // Month (Jan)
  1,    // Day (1)
  0,    // Hour
  0,    // Minute
  0,    // Second
  0,    // Pad1
  0,    // Nanosecond
  0,    // Timezone (Dummy value)
  0,    // Daylight (Dummy value)
  0     // Pad2
};
 
STATIC
EFI_STATUS
CreateSigList (
  IN VOID                 *Data,
  IN UINTN                Size,
  OUT EFI_SIGNATURE_LIST  **SigList
  )
{
  UINTN               SigListSize;
  EFI_SIGNATURE_LIST  *TmpSigList;
  EFI_SIGNATURE_DATA  *SigData;
 
  //
  // Allocate data for Signature Database
  //
  SigListSize = sizeof (EFI_SIGNATURE_LIST) + sizeof (EFI_SIGNATURE_DATA) - 1 + Size;
  TmpSigList  = (EFI_SIGNATURE_LIST *)AllocateZeroPool (SigListSize);
  if (TmpSigList == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  //
  // Only gEfiCertX509Guid type is supported
  //
  TmpSigList->SignatureListSize   = (UINT32)SigListSize;
  TmpSigList->SignatureSize       = (UINT32)(sizeof (EFI_SIGNATURE_DATA) - 1 + Size);
  TmpSigList->SignatureHeaderSize = 0;
  CopyGuid (&TmpSigList->SignatureType, &gEfiCertX509Guid);
 
  //
  // Copy key data
  //
  SigData = (EFI_SIGNATURE_DATA *)(TmpSigList + 1);
  CopyGuid (&SigData->SignatureOwner, &gEfiGlobalVariableGuid);
  CopyMem (&SigData->SignatureData[0], Data, Size);
 
  *SigList = TmpSigList;
 
  return EFI_SUCCESS;
}
 
STATIC
EFI_STATUS
ConcatenateSigList (
  IN  EFI_SIGNATURE_LIST  *SigLists,
  IN  EFI_SIGNATURE_LIST  *SigListAppend,
  OUT EFI_SIGNATURE_LIST  **SigListOut,
  IN OUT UINTN            *SigListsSize
  )
{
  EFI_SIGNATURE_LIST  *TmpSigList;
  UINT8               *Offset;
  UINTN               NewSigListsSize;
 
  NewSigListsSize = *SigListsSize + SigListAppend->SignatureListSize;
 
  TmpSigList = (EFI_SIGNATURE_LIST *)AllocateZeroPool (NewSigListsSize);
  if (TmpSigList == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  CopyMem (TmpSigList, SigLists, *SigListsSize);
 
  Offset  = (UINT8 *)TmpSigList;
  Offset += *SigListsSize;
  CopyMem ((VOID *)Offset, SigListAppend, SigListAppend->SignatureListSize);
 
  *SigListsSize = NewSigListsSize;
  *SigListOut   = TmpSigList;
  return EFI_SUCCESS;
}
 
EFI_STATUS
EFIAPI
SecureBootCreateDataFromInput (
  OUT UINTN                               *SigListsSize,
  OUT EFI_SIGNATURE_LIST                  **SigListOut,
  IN  UINTN                               KeyInfoCount,
  IN  CONST SECURE_BOOT_CERTIFICATE_INFO  *KeyInfo
  )
{
  EFI_SIGNATURE_LIST  *EfiSig;
  EFI_SIGNATURE_LIST  *TmpEfiSig;
  EFI_SIGNATURE_LIST  *TmpEfiSig2;
  EFI_STATUS          Status;
  VOID                *Buffer;
  UINTN               Size;
  UINTN               InputIndex;
  UINTN               KeyIndex;
 
  if ((SigListOut == NULL) || (SigListsSize == NULL)) {
    return EFI_INVALID_PARAMETER;
  }
 
  if ((KeyInfoCount == 0) || (KeyInfo == NULL)) {
    return EFI_INVALID_PARAMETER;
  }
 
  InputIndex    = 0;
  KeyIndex      = 0;
  EfiSig        = NULL;
  *SigListsSize = 0;
  while (InputIndex < KeyInfoCount) {
    if (KeyInfo[InputIndex].Data != NULL) {
      Size   = KeyInfo[InputIndex].DataSize;
      Buffer = AllocateCopyPool (Size, KeyInfo[InputIndex].Data);
      if (Buffer == NULL) {
        if (EfiSig != NULL) {
          FreePool (EfiSig);
        }
 
        return EFI_OUT_OF_RESOURCES;
      }
 
      Status = CreateSigList (Buffer, Size, &TmpEfiSig);
 
      if (EFI_ERROR (Status)) {
        FreePool (Buffer);
        break;
      }
 
      //
      // Concatenate lists if more than one section found
      //
      if (KeyIndex == 0) {
        EfiSig        = TmpEfiSig;
        *SigListsSize = TmpEfiSig->SignatureListSize;
      } else {
        ConcatenateSigList (EfiSig, TmpEfiSig, &TmpEfiSig2, SigListsSize);
        FreePool (EfiSig);
        FreePool (TmpEfiSig);
        EfiSig = TmpEfiSig2;
      }
 
      KeyIndex++;
      FreePool (Buffer);
    }
 
    InputIndex++;
  }
 
  if (KeyIndex == 0) {
    return EFI_NOT_FOUND;
  }
 
  *SigListOut = EfiSig;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
EFIAPI
CreateTimeBasedPayload (
  IN OUT UINTN     *DataSize,
  IN OUT UINT8     **Data,
  IN     EFI_TIME  *Time
  )
{
  UINT8                          *NewData;
  UINT8                          *Payload;
  UINTN                          PayloadSize;
  EFI_VARIABLE_AUTHENTICATION_2  *DescriptorData;
  UINTN                          DescriptorSize;
 
  if ((Data == NULL) || (DataSize == NULL) || (Time == NULL)) {
    DEBUG ((DEBUG_ERROR, "%a(), invalid arg\n", __func__));
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // In Setup mode or Custom mode, the variable does not need to be signed but the
  // parameters to the SetVariable() call still need to be prepared as authenticated
  // variable. So we create EFI_VARIABLE_AUTHENTICATED_2 descriptor without certificate
  // data in it.
  //
  Payload     = *Data;
  PayloadSize = *DataSize;
 
  DescriptorSize = OFFSET_OF (EFI_VARIABLE_AUTHENTICATION_2, AuthInfo) + OFFSET_OF (WIN_CERTIFICATE_UEFI_GUID, CertData);
  NewData        = (UINT8 *)AllocateZeroPool (DescriptorSize + PayloadSize);
  if (NewData == NULL) {
    DEBUG ((DEBUG_ERROR, "%a() Out of resources.\n", __func__));
    return EFI_OUT_OF_RESOURCES;
  }
 
  if ((Payload != NULL) && (PayloadSize != 0)) {
    CopyMem (NewData + DescriptorSize, Payload, PayloadSize);
  }
 
  DescriptorData = (EFI_VARIABLE_AUTHENTICATION_2 *)(NewData);
 
  CopyMem (&DescriptorData->TimeStamp, Time, sizeof (EFI_TIME));
 
  DescriptorData->AuthInfo.Hdr.dwLength         = OFFSET_OF (WIN_CERTIFICATE_UEFI_GUID, CertData);
  DescriptorData->AuthInfo.Hdr.wRevision        = 0x0200;
  DescriptorData->AuthInfo.Hdr.wCertificateType = WIN_CERT_TYPE_EFI_GUID;
  CopyGuid (&DescriptorData->AuthInfo.CertType, &gEfiCertPkcs7Guid);
 
  if (Payload != NULL) {
    FreePool (Payload);
    Payload = NULL;
  }
 
  *DataSize = DescriptorSize + PayloadSize;
  *Data     = NewData;
  return EFI_SUCCESS;
}
 
EFI_STATUS
EFIAPI
DeleteVariable (
  IN  CHAR16    *VariableName,
  IN  EFI_GUID  *VendorGuid
  )
{
  EFI_STATUS  Status;
  VOID        *Variable;
  UINT8       *Data;
  UINTN       DataSize;
  UINT32      Attr;
 
  GetVariable2 (VariableName, VendorGuid, &Variable, NULL);
  if (Variable == NULL) {
    return EFI_SUCCESS;
  }
 
  FreePool (Variable);
 
  Data     = NULL;
  DataSize = 0;
  Attr     = EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS
             | EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS;
 
  Status = CreateTimeBasedPayload (&DataSize, &Data, &mMaxTimestamp);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR, "Fail to create time-based data payload: %r", Status));
    return Status;
  }
 
  Status = gRT->SetVariable (
                  VariableName,
                  VendorGuid,
                  Attr,
                  DataSize,
                  Data
                  );
  if (Data != NULL) {
    FreePool (Data);
  }
 
  return Status;
}
 
EFI_STATUS
EFIAPI
SetSecureBootMode (
  IN  UINT8  SecureBootMode
  )
{
  return gRT->SetVariable (
                EFI_CUSTOM_MODE_NAME,
                &gEfiCustomModeEnableGuid,
                EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS,
                sizeof (UINT8),
                &SecureBootMode
                );
}
 
EFI_STATUS
EFIAPI
GetSetupMode (
  OUT UINT8  *SetupMode
  )
{
  UINTN       Size;
  EFI_STATUS  Status;
 
  Size   = sizeof (*SetupMode);
  Status = gRT->GetVariable (
                  EFI_SETUP_MODE_NAME,
                  &gEfiGlobalVariableGuid,
                  NULL,
                  &Size,
                  SetupMode
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  return EFI_SUCCESS;
}
 
BOOLEAN
EFIAPI
IsSecureBootEnabled (
  VOID
  )
{
  EFI_STATUS  Status;
  UINT8       *SecureBoot;
 
  SecureBoot = NULL;
 
  Status = GetEfiGlobalVariable2 (EFI_SECURE_BOOT_MODE_NAME, (VOID **)&SecureBoot, NULL);
  //
  // Skip verification if SecureBoot variable doesn't exist.
  //
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR, "Cannot check SecureBoot variable %r \n ", Status));
    return FALSE;
  }
 
  //
  // Skip verification if SecureBoot is disabled but not AuditMode
  //
  if (*SecureBoot == SECURE_BOOT_MODE_DISABLE) {
    FreePool (SecureBoot);
    return FALSE;
  } else {
    return TRUE;
  }
}
 
EFI_STATUS
EFIAPI
DeleteDb (
  VOID
  )
{
  EFI_STATUS  Status;
 
  Status = DeleteVariable (
             EFI_IMAGE_SECURITY_DATABASE,
             &gEfiImageSecurityDatabaseGuid
             );
 
  return Status;
}
 
EFI_STATUS
EFIAPI
DeleteDbx (
  VOID
  )
{
  EFI_STATUS  Status;
 
  Status = DeleteVariable (
             EFI_IMAGE_SECURITY_DATABASE1,
             &gEfiImageSecurityDatabaseGuid
             );
 
  return Status;
}
 
EFI_STATUS
EFIAPI
DeleteDbt (
  VOID
  )
{
  EFI_STATUS  Status;
 
  Status = DeleteVariable (
             EFI_IMAGE_SECURITY_DATABASE2,
             &gEfiImageSecurityDatabaseGuid
             );
 
  return Status;
}
 
EFI_STATUS
EFIAPI
DeleteKEK (
  VOID
  )
{
  EFI_STATUS  Status;
 
  Status = DeleteVariable (
             EFI_KEY_EXCHANGE_KEY_NAME,
             &gEfiGlobalVariableGuid
             );
 
  return Status;
}
 
EFI_STATUS
EFIAPI
DeletePlatformKey (
  VOID
  )
{
  EFI_STATUS  Status;
 
  Status = SetSecureBootMode (CUSTOM_SECURE_BOOT_MODE);
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  Status = DeleteVariable (
             EFI_PLATFORM_KEY_NAME,
             &gEfiGlobalVariableGuid
             );
  return Status;
}
 
EFI_STATUS
EFIAPI
DeleteSecureBootVariables (
  VOID
  )
{
  EFI_STATUS  Status, TempStatus;
 
  DEBUG ((DEBUG_INFO, "%a - Attempting to delete the Secure Boot variables.\n", __func__));
 
  //
  // Step 1: Notify that a PK update is coming shortly...
  Status = DisablePKProtection ();
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR, "%a - Failed to signal PK update start! %r\n", __func__, Status));
    // Classify this as a PK deletion error.
    Status = EFI_ABORTED;
  }
 
  //
  // Step 2: Attempt to delete the PK.
  // Let's try to nuke the PK, why not...
  if (!EFI_ERROR (Status)) {
    Status = DeletePlatformKey ();
    DEBUG ((DEBUG_INFO, "%a - PK Delete = %r\n", __func__, Status));
    // If the PK is not found, then our work here is done.
    if (Status == EFI_NOT_FOUND) {
      Status = EFI_SUCCESS;
    }
    // If any other error occurred, let's inform the caller that the PK delete in particular failed.
    else if (EFI_ERROR (Status)) {
      Status = EFI_ABORTED;
    }
  }
 
  //
  // Step 3: Attempt to delete remaining keys/databases...
  // Now that the PK is deleted (assuming Status == EFI_SUCCESS) the system is in SETUP_MODE.
  // Arguably we could leave these variables in place and let them be deleted by whoever wants to
  // update all the SecureBoot variables. However, for cleanliness sake, let's try to
  // get rid of them here.
  if (!EFI_ERROR (Status)) {
    //
    // If any of THESE steps have an error, report the error but attempt to delete all keys.
    // Using TempStatus will prevent an error from being trampled by an EFI_SUCCESS.
    // Overwrite Status ONLY if TempStatus is an error.
    //
    // If the error is EFI_NOT_FOUND, we can safely ignore it since we were trying to delete
    // the variables anyway.
    //
    TempStatus = DeleteKEK ();
    DEBUG ((DEBUG_INFO, "%a - KEK Delete = %r\n", __func__, TempStatus));
    if (EFI_ERROR (TempStatus) && (TempStatus != EFI_NOT_FOUND)) {
      Status = EFI_ACCESS_DENIED;
    }
 
    TempStatus = DeleteDb ();
    DEBUG ((DEBUG_INFO, "%a - db Delete = %r\n", __func__, TempStatus));
    if (EFI_ERROR (TempStatus) && (TempStatus != EFI_NOT_FOUND)) {
      Status = EFI_ACCESS_DENIED;
    }
 
    TempStatus = DeleteDbx ();
    DEBUG ((DEBUG_INFO, "%a - dbx Delete = %r\n", __func__, TempStatus));
    if (EFI_ERROR (TempStatus) && (TempStatus != EFI_NOT_FOUND)) {
      Status = EFI_ACCESS_DENIED;
    }
 
    TempStatus = DeleteDbt ();
    DEBUG ((DEBUG_INFO, "%a - dbt Delete = %r\n", __func__, TempStatus));
    if (EFI_ERROR (TempStatus) && (TempStatus != EFI_NOT_FOUND)) {
      Status = EFI_ACCESS_DENIED;
    }
  }
 
  return Status;
}// DeleteSecureBootVariables()
 
EFI_STATUS
EFIAPI
EnrollFromInput (
  IN CHAR16    *VariableName,
  IN EFI_GUID  *VendorGuid,
  IN UINTN     DataSize,
  IN VOID      *Data
  )
{
  VOID        *Payload;
  UINTN       PayloadSize;
  EFI_STATUS  Status;
 
  Payload = NULL;
 
  if ((VariableName == NULL) || (VendorGuid == 0)) {
    DEBUG ((DEBUG_ERROR, "Input vendor variable invalid: %p and %p\n", VariableName, VendorGuid));
    Status = EFI_INVALID_PARAMETER;
    goto Exit;
  }
 
  if ((Data == NULL) || (DataSize == 0)) {
    // You might as well just use DeleteVariable...
    DEBUG ((DEBUG_ERROR, "Input argument invalid: %p: %x\n", Data, DataSize));
    Status = EFI_INVALID_PARAMETER;
    goto Exit;
  }
 
  // Bring in the noise...
  PayloadSize = DataSize;
  Payload     = AllocateZeroPool (DataSize);
  // Bring in the funk...
  if (Payload == NULL) {
    return EFI_OUT_OF_RESOURCES;
  } else {
    CopyMem (Payload, Data, DataSize);
  }
 
  Status = CreateTimeBasedPayload (&PayloadSize, (UINT8 **)&Payload, &mDefaultPayloadTimestamp);
  if (EFI_ERROR (Status) || (Payload == NULL)) {
    DEBUG ((DEBUG_ERROR, "Fail to create time-based data payload: %r\n", Status));
    Payload = NULL;
    Status  = EFI_OUT_OF_RESOURCES;
    goto Exit;
  }
 
  //
  // Allocate memory for auth variable
  //
  Status = gRT->SetVariable (
                  VariableName,
                  VendorGuid,
                  (EFI_VARIABLE_NON_VOLATILE |
                   EFI_VARIABLE_BOOTSERVICE_ACCESS |
                   EFI_VARIABLE_RUNTIME_ACCESS |
                   EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS),
                  PayloadSize,
                  Payload
                  );
 
  if (EFI_ERROR (Status)) {
    DEBUG ((
      DEBUG_ERROR,
      "error: %a (\"%s\", %g): %r\n",
      __func__,
      VariableName,
      VendorGuid,
      Status
      ));
  }
 
Exit:
  //
  // Always Put Away Your Toys
  // Payload will be reassigned by CreateTimeBasedPayload()...
  if (Payload != NULL) {
    FreePool (Payload);
    Payload = NULL;
  }
 
  return Status;
}
 
EFI_STATUS
EFIAPI
SetSecureBootVariablesToDefault (
  IN  CONST SECURE_BOOT_PAYLOAD_INFO  *SecureBootPayload
  )
{
  EFI_STATUS  Status;
  UINT8       *Data;
  UINTN       DataSize;
 
  DEBUG ((DEBUG_INFO, "%a() Entry\n", __func__));
 
  if (SecureBootPayload == NULL) {
    DEBUG ((DEBUG_ERROR, "%a - Invalid SecureBoot payload is supplied!\n", __func__));
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Right off the bat, if SecureBoot is currently enabled, bail.
  if (IsSecureBootEnabled ()) {
    DEBUG ((DEBUG_ERROR, "%a - Cannot set default keys while SecureBoot is enabled!\n", __func__));
    return EFI_ABORTED;
  }
 
  DEBUG ((DEBUG_INFO, "%a - Setting up key %s!\n", __func__, SecureBootPayload->SecureBootKeyName));
 
  //
  // Start running down the list, creating variables in our wake.
  // dbx is a good place to start.
  Data     = (UINT8 *)SecureBootPayload->DbxPtr;
  DataSize = SecureBootPayload->DbxSize;
  Status   = EnrollFromInput (
               EFI_IMAGE_SECURITY_DATABASE1,
               &gEfiImageSecurityDatabaseGuid,
               DataSize,
               Data
               );
 
  // If that went well, try the db (make sure to pick the right one!).
  if (!EFI_ERROR (Status)) {
    Data     = (UINT8 *)SecureBootPayload->DbPtr;
    DataSize = SecureBootPayload->DbSize;
    Status   = EnrollFromInput (
                 EFI_IMAGE_SECURITY_DATABASE,
                 &gEfiImageSecurityDatabaseGuid,
                 DataSize,
                 Data
                 );
    if (EFI_ERROR (Status)) {
      DEBUG ((DEBUG_ERROR, "%a - Failed to enroll DB %r!\n", __func__, Status));
    }
  } else {
    DEBUG ((DEBUG_ERROR, "%a - Failed to enroll DBX %r!\n", __func__, Status));
  }
 
  // Keep it going. Keep it going. dbt if supplied...
  if (!EFI_ERROR (Status) && (SecureBootPayload->DbtPtr != NULL)) {
    Data     = (UINT8 *)SecureBootPayload->DbtPtr;
    DataSize = SecureBootPayload->DbtSize;
    Status   = EnrollFromInput (
                 EFI_IMAGE_SECURITY_DATABASE2,
                 &gEfiImageSecurityDatabaseGuid,
                 DataSize,
                 Data
                 );
    if (EFI_ERROR (Status)) {
      DEBUG ((DEBUG_ERROR, "%a - Failed to enroll DBT %r!\n", __func__, Status));
    }
  }
 
  // Keep it going. Keep it going. KEK...
  if (!EFI_ERROR (Status)) {
    Data     = (UINT8 *)SecureBootPayload->KekPtr;
    DataSize = SecureBootPayload->KekSize;
    Status   = EnrollFromInput (
                 EFI_KEY_EXCHANGE_KEY_NAME,
                 &gEfiGlobalVariableGuid,
                 DataSize,
                 Data
                 );
    if (EFI_ERROR (Status)) {
      DEBUG ((DEBUG_ERROR, "%a - Failed to enroll KEK %r!\n", __func__, Status));
    }
  }
 
  //
  // Finally! The Big Daddy of them all.
  // The PK!
  //
  if (!EFI_ERROR (Status)) {
    //
    // Finally, install the key.
    Data     = (UINT8 *)SecureBootPayload->PkPtr;
    DataSize = SecureBootPayload->PkSize;
    Status   = EnrollFromInput (
                 EFI_PLATFORM_KEY_NAME,
                 &gEfiGlobalVariableGuid,
                 DataSize,
                 Data
                 );
 
    //
    // Report PK creation errors.
    if (EFI_ERROR (Status)) {
      DEBUG ((DEBUG_ERROR, "%a - Failed to update the PK! - %r\n", __func__, Status));
      Status = EFI_SECURITY_VIOLATION;
    }
  }
 
  return Status;
}