OpenCellular/vboot_firmware/lib/rollback_index.c

/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 *
 * Functions for querying, manipulating and locking rollback indices
 * stored in the TPM NVRAM.
 */

#include "rollback_index.h"

#include <stdint.h>

#include "utility.h"
#include "tlcl.h"
#include "tss_constants.h"

uint16_t g_firmware_key_version = 0;
uint16_t g_firmware_version = 0;
uint16_t g_kernel_key_version = 0;
uint16_t g_kernel_version = 0;

#define RETURN_ON_FAILURE(tpm_command) do {     \
    uint32_t result;                            \
    if ((result = tpm_command) != TPM_SUCCESS) {\
      return result;                            \
    }                                           \
  } while (0)

static uint32_t InitializeSpaces(void) {
  uint32_t zero = 0;
  uint32_t space_holder;
  uint32_t firmware_perm = TPM_NV_PER_GLOBALLOCK | TPM_NV_PER_PPWRITE;
  uint32_t kernel_perm = TPM_NV_PER_PPWRITE;

  debug("Initializing spaces\n");

  if (TlclRead(TPM_IS_INITIALIZED_NV_INDEX,
               (uint8_t*) &space_holder, sizeof(space_holder)) == TPM_SUCCESS) {
    /* Spaces are already initialized, so this is an error */
    return 0;
  }

  RETURN_ON_FAILURE(TlclSetNvLocked());

  RETURN_ON_FAILURE(TlclDefineSpace(FIRMWARE_VERSIONS_NV_INDEX,
                                    firmware_perm, sizeof(uint32_t)));
  RETURN_ON_FAILURE(TlclWrite(FIRMWARE_VERSIONS_NV_INDEX,
                              (uint8_t*) &zero, sizeof(uint32_t)));

  RETURN_ON_FAILURE(TlclDefineSpace(KERNEL_VERSIONS_NV_INDEX,
                                    kernel_perm, sizeof(uint32_t)));
  RETURN_ON_FAILURE(TlclWrite(KERNEL_VERSIONS_NV_INDEX, (uint8_t*) &zero,
                              sizeof(uint32_t)));

  /* The space KERNEL_VERSIONS_BACKUP_NV_INDEX is used to protect the kernel
   * versions when entering recovery mode.  The content of space
   * KERNEL_BACKUP_IS_VALID determines whether the backup value (1) or the
   * regular value (0) should be trusted.
   */
  RETURN_ON_FAILURE(TlclDefineSpace(KERNEL_VERSIONS_BACKUP_NV_INDEX,
                                    firmware_perm, sizeof(uint32_t)));
  RETURN_ON_FAILURE(TlclWrite(KERNEL_VERSIONS_BACKUP_NV_INDEX,
                              (uint8_t*) &zero, sizeof(uint32_t)));
  RETURN_ON_FAILURE(TlclDefineSpace(KERNEL_BACKUP_IS_VALID_NV_INDEX,
                                    firmware_perm, sizeof(uint32_t)));
  RETURN_ON_FAILURE(TlclWrite(KERNEL_BACKUP_IS_VALID_NV_INDEX,
                              (uint8_t*) &zero, sizeof(uint32_t)));

  /* The space TPM_IS_INITIALIZED_NV_INDEX is used to indicate that the TPM
   * initialization has completed.  Without it we cannot be sure that the last
   * space to be created was also initialized (power could have been lost right
   * after its creation).
   */
  RETURN_ON_FAILURE(TlclDefineSpace(TPM_IS_INITIALIZED_NV_INDEX,
                                    firmware_perm, sizeof(uint32_t)));
  return TPM_SUCCESS;
}

/* Enters the recovery mode.  If |unlocked| is true, there is some problem with
 * the TPM, so do not attempt to do any more TPM operations, and particularly
 * do not set bGlobalLock.
 */
static void EnterRecovery(int unlocked) {
  uint32_t combined_versions;
  uint32_t backup_versions;
  uint32_t backup_is_valid;

  if (!unlocked) {
    /* Saves the kernel versions and indicates that we should trust the saved
     * ones.
     */
    TlclRead(KERNEL_VERSIONS_NV_INDEX,
             (uint8_t*) &combined_versions, sizeof(uint32_t));
    TlclRead(KERNEL_VERSIONS_BACKUP_NV_INDEX,
             (uint8_t*) &backup_versions, sizeof(uint32_t));
    /* We could unconditional writes of both KERNEL_VERSIONS_BACKUP and
     * KERNEL_BACKUP_IS_VALID, but this is more robust.
     */
    if (combined_versions != backup_versions) {
      TlclWrite(KERNEL_VERSIONS_BACKUP_NV_INDEX,
                (uint8_t*) &combined_versions, sizeof(uint32_t));
    }

    TlclRead(KERNEL_BACKUP_IS_VALID_NV_INDEX,
             (uint8_t*) &backup_is_valid, sizeof(uint32_t));
    if (backup_is_valid != 1) {
      backup_is_valid = 1;
      TlclWrite(KERNEL_BACKUP_IS_VALID_NV_INDEX, (uint8_t*) &backup_is_valid,
                sizeof(uint32_t));
    }
    /* Protects the firmware and backup kernel versions. */
    LockFirmwareVersions();
  }
  debug("entering recovery mode");

  /* TODO(nelson): code for entering recovery mode. */
}

static uint32_t GetTPMRollbackIndices(void) {
  uint32_t backup_is_valid;
  uint32_t firmware_versions;
  uint32_t kernel_versions;

  if (TlclRead(KERNEL_BACKUP_IS_VALID_NV_INDEX, (uint8_t*) &backup_is_valid,
               sizeof(uint32_t)) != TPM_SUCCESS) {
    EnterRecovery(1);
  }
  if (backup_is_valid) {
    /* We reach this path if the previous boot went into recovery mode and we
     * made a copy of the kernel versions to protect them.
     */
    uint32_t protected_combined_versions;
    uint32_t unsafe_combined_versions;
    uint32_t result;
    uint32_t zero = 0;
    if (TlclRead(KERNEL_VERSIONS_BACKUP_NV_INDEX,
                 (uint8_t*) &protected_combined_versions,
                 sizeof(uint32_t)) != TPM_SUCCESS) {
      EnterRecovery(1);
    }
    result = TlclRead(KERNEL_VERSIONS_NV_INDEX,
                      (uint8_t*) &unsafe_combined_versions, sizeof(uint32_t));
    if (result == TPM_E_BADINDEX) {
      /* Jeez, someone removed the space.  This is either hostile or extremely
       * incompetent.  Foo to them.  Politeness and lack of an adequate
       * character set prevent me from expressing my true feelings.
       */
      RETURN_ON_FAILURE(TlclDefineSpace(KERNEL_VERSIONS_NV_INDEX,
                                        TPM_NV_PER_PPWRITE,
                                        sizeof(uint32_t)));
    } else if (result != TPM_SUCCESS) {
      EnterRecovery(1);
    }
    if (result == TPM_E_BADINDEX ||
        protected_combined_versions != unsafe_combined_versions) {
      RETURN_ON_FAILURE(TlclWrite(KERNEL_VERSIONS_NV_INDEX,
                                  (uint8_t*) &protected_combined_versions,
                                  sizeof(uint32_t)));
    }
    /* We recovered the backed-up versions and now we can reset the
     * BACKUP_IS_VALID flag.
     */
    RETURN_ON_FAILURE(TlclWrite(KERNEL_BACKUP_IS_VALID_NV_INDEX,
                                (uint8_t*) &zero, 0));

    if (!TlclIsOwned()) {
      /* Must ForceClear and reboot to prevent from running into the 64-write
       * limit.
       */
      RETURN_ON_FAILURE(TlclForceClear());
      /* Reboot!  No return */
      return 9999;
    }
  }

  /* We perform the reads, making sure they succeed. A failure means that the
   * rollback index locations are missing or somehow messed up.  We let the
   * caller deal with that.
   */
  RETURN_ON_FAILURE(TlclRead(FIRMWARE_VERSIONS_NV_INDEX,
                             (uint8_t*) &firmware_versions,
                             sizeof(firmware_versions)));
  RETURN_ON_FAILURE(TlclRead(KERNEL_VERSIONS_NV_INDEX,
                             (uint8_t*) &kernel_versions,
                             sizeof(kernel_versions)));

  g_firmware_key_version = firmware_versions >> 16;
  g_firmware_version = firmware_versions && 0xffff;
  g_kernel_key_version = kernel_versions >> 16;
  g_kernel_version = kernel_versions && 0xffff;

  return TPM_SUCCESS;
}


uint32_t SetupTPM(void) {
  uint8_t disable;
  uint8_t deactivated;
  TlclLibInit();
  RETURN_ON_FAILURE(TlclStartup());
  RETURN_ON_FAILURE(TlclContinueSelfTest());
  RETURN_ON_FAILURE(TlclAssertPhysicalPresence());
  /* Check that the TPM is enabled and activated. */
  RETURN_ON_FAILURE(TlclGetFlags(&disable, &deactivated));
  if (disable || deactivated) {
    RETURN_ON_FAILURE(TlclSetEnable());
    RETURN_ON_FAILURE(TlclSetDeactivated(0));
    /* TODO: Reboot now */
    return 9999;
  }
  /* We expect this to fail the first time we run on a device, indicating that
   * the TPM has not been initialized yet. */
  if (GetTPMRollbackIndices() != TPM_SUCCESS) {
    /* If InitializeSpaces() fails (possibly because it had been executed
     * already), something is wrong. */
    RETURN_ON_FAILURE(InitializeSpaces());
    /* Try again. */
    RETURN_ON_FAILURE(GetTPMRollbackIndices());
  }

  return TPM_SUCCESS;
}

uint32_t GetStoredVersions(int type, uint16_t* key_version, uint16_t* version) {

  /* TODO: should verify that SetupTPM() has been called.  Note that
   * SetupTPM() does hardware setup AND sets global variables.  When we
   * get down into kernel verification, the hardware setup persists, but
   * we don't have access to the global variables.  So I guess we DO need
   * to call SetupTPM() there, and have it be smart enough not to redo the
   * hardware init, but it still needs to re-read the flags... */

  switch (type) {
    case FIRMWARE_VERSIONS:
      *key_version = g_firmware_key_version;
      *version = g_firmware_version;
      break;
    case KERNEL_VERSIONS:
      *key_version = g_kernel_key_version;
      *version = g_kernel_version;
      break;
  }

  return TPM_SUCCESS;
}

uint32_t WriteStoredVersions(int type, uint16_t key_version, uint16_t version) {
  uint32_t combined_version = (key_version << 16) & version;
  switch (type) {
    case FIRMWARE_VERSIONS:
      RETURN_ON_FAILURE(TlclWrite(FIRMWARE_VERSIONS_NV_INDEX,
                                  (uint8_t*) &combined_version,
                                  sizeof(uint32_t)));
      break;

    case KERNEL_VERSIONS:
      RETURN_ON_FAILURE(TlclWrite(KERNEL_VERSIONS_NV_INDEX,
                                  (uint8_t*) &combined_version,
                                  sizeof(uint32_t)));
      break;
  }
  /* TODO(semenzato): change TlclIsOwned to return a TPM status directly and
   * the "owned" value by reference.
   */
  if (!TlclIsOwned()) {
    RETURN_ON_FAILURE(TlclForceClear());
    /* TODO: Reboot here.  No return. */
    return 9999;
  }
  return TPM_SUCCESS;
}

uint32_t LockFirmwareVersions() {
  return TlclSetGlobalLock();
}

uint32_t LockKernelVersionsByLockingPP() {
  return TlclLockPhysicalPresence();
}