blob: 654fd3438ff0bd6f03d318fd3b19e65960a595e6 [file] [log] [blame]
/* Copyright (c) 2013 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 <antirollback.h>
#include <stdlib.h>
#include <string.h>
#include <tpm_lite/tlcl.h>
#include <tpm_lite/tss_constants.h>
#include <vb2_api.h>
#ifndef offsetof
#define offsetof(A,B) __builtin_offsetof(A,B)
#endif
#ifdef FOR_TEST
#include <stdio.h>
#define VBDEBUG(format, args...) printf(format, ## args)
#else
#include <console/console.h>
#define VBDEBUG(format, args...) \
printk(BIOS_INFO, "%s():%d: " format, __func__, __LINE__, ## args)
#endif
#define RETURN_ON_FAILURE(tpm_cmd) do { \
uint32_t result_; \
if ((result_ = (tpm_cmd)) != TPM_SUCCESS) { \
VBDEBUG("Antirollback: %08x returned by " #tpm_cmd \
"\n", (int)result_); \
return result_; \
} \
} while (0)
uint32_t tpm_extend_pcr(struct vb2_context *ctx, int pcr,
enum vb2_pcr_digest which_digest)
{
uint8_t buffer[VB2_PCR_DIGEST_RECOMMENDED_SIZE];
uint32_t size = sizeof(buffer);
int rv;
rv = vb2api_get_pcr_digest(ctx, which_digest, buffer, &size);
if (rv != VB2_SUCCESS)
return rv;
if (size < TPM_PCR_DIGEST)
return VB2_ERROR_UNKNOWN;
return tlcl_extend(pcr, buffer, NULL);
}
uint32_t tpm_clear_and_reenable(void)
{
VBDEBUG("TPM: Clear and re-enable\n");
RETURN_ON_FAILURE(tlcl_force_clear());
RETURN_ON_FAILURE(tlcl_set_enable());
RETURN_ON_FAILURE(tlcl_set_deactivated(0));
return TPM_SUCCESS;
}
uint32_t safe_write(uint32_t index, const void *data, uint32_t length)
{
uint32_t result = tlcl_write(index, data, length);
if (result == TPM_E_MAXNVWRITES) {
RETURN_ON_FAILURE(tpm_clear_and_reenable());
return tlcl_write(index, data, length);
} else {
return result;
}
}
uint32_t safe_define_space(uint32_t index, uint32_t perm, uint32_t size)
{
uint32_t result = tlcl_define_space(index, perm, size);
if (result == TPM_E_MAXNVWRITES) {
RETURN_ON_FAILURE(tpm_clear_and_reenable());
return tlcl_define_space(index, perm, size);
} else {
return result;
}
}
static uint32_t read_space_firmware(struct vb2_context *ctx)
{
int attempts = 3;
while (attempts--) {
RETURN_ON_FAILURE(tlcl_read(FIRMWARE_NV_INDEX, ctx->secdata,
VB2_SECDATA_SIZE));
if (vb2api_secdata_check(ctx) == VB2_SUCCESS)
return TPM_SUCCESS;
VBDEBUG("TPM: %s() - bad CRC\n", __func__);
}
VBDEBUG("TPM: %s() - too many bad CRCs, giving up\n", __func__);
return TPM_E_CORRUPTED_STATE;
}
static uint32_t write_secdata(uint32_t index,
const uint8_t *secdata,
uint32_t len)
{
uint8_t sd[32];
uint32_t rv;
int attempts = 3;
if (len > sizeof(sd)) {
VBDEBUG("TPM: %s() - data is too large\n", __func__);
return TPM_E_WRITE_FAILURE;
}
while (attempts--) {
rv = safe_write(index, secdata, len);
/* Can't write, not gonna try again */
if (rv != TPM_SUCCESS)
return rv;
/* Read it back to be sure it got the right values. */
rv = tlcl_read(index, sd, len);
if (rv == TPM_SUCCESS && memcmp(secdata, sd, len) == 0)
return rv;
VBDEBUG("TPM: %s() failed. trying again\n", __func__);
/* Try writing it again. Maybe it was garbled on the way out. */
}
VBDEBUG("TPM: %s() - too many failures, giving up\n", __func__);
return TPM_E_CORRUPTED_STATE;
}
uint32_t factory_initialize_tpm(struct vb2_context *ctx)
{
TPM_PERMANENT_FLAGS pflags;
uint32_t result;
/* this is derived from rollback_index.h of vboot_reference. see struct
* RollbackSpaceKernel for details. */
static const uint8_t secdata_kernel[] = {
0x02,
0x4C, 0x57, 0x52, 0x47,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00,
0xE8,
};
VBDEBUG("TPM: factory initialization\n");
/*
* Do a full test. This only happens the first time the device is
* turned on in the factory, so performance is not an issue. This is
* almost certainly not necessary, but it gives us more confidence
* about some code paths below that are difficult to
* test---specifically the ones that set lifetime flags, and are only
* executed once per physical TPM.
*/
result = tlcl_self_test_full();
if (result != TPM_SUCCESS)
return result;
result = tlcl_get_permanent_flags(&pflags);
if (result != TPM_SUCCESS)
return result;
/*
* TPM may come from the factory without physical presence finalized.
* Fix if necessary.
*/
VBDEBUG("TPM: physicalPresenceLifetimeLock=%d\n",
pflags.physicalPresenceLifetimeLock);
if (!pflags.physicalPresenceLifetimeLock) {
VBDEBUG("TPM: Finalizing physical presence\n");
RETURN_ON_FAILURE(tlcl_finalize_physical_presence());
}
/*
* The TPM will not enforce the NV authorization restrictions until the
* execution of a TPM_NV_DefineSpace with the handle of
* TPM_NV_INDEX_LOCK. Here we create that space if it doesn't already
* exist. */
VBDEBUG("TPM: nvLocked=%d\n", pflags.nvLocked);
if (!pflags.nvLocked) {
VBDEBUG("TPM: Enabling NV locking\n");
RETURN_ON_FAILURE(tlcl_set_nv_locked());
}
/* Clear TPM owner, in case the TPM is already owned for some reason. */
VBDEBUG("TPM: Clearing owner\n");
RETURN_ON_FAILURE(tpm_clear_and_reenable());
/* Define the backup space. No need to initialize it, though. */
RETURN_ON_FAILURE(safe_define_space(BACKUP_NV_INDEX,
TPM_NV_PER_PPWRITE,
VB2_NVDATA_SIZE));
/* Define and initialize the kernel space */
RETURN_ON_FAILURE(safe_define_space(KERNEL_NV_INDEX,
TPM_NV_PER_PPWRITE,
sizeof(secdata_kernel)));
RETURN_ON_FAILURE(write_secdata(KERNEL_NV_INDEX,
secdata_kernel,
sizeof(secdata_kernel)));
/* Defines and sets vb2 secdata space */
vb2api_secdata_create(ctx);
RETURN_ON_FAILURE(safe_define_space(FIRMWARE_NV_INDEX,
TPM_NV_PER_GLOBALLOCK |
TPM_NV_PER_PPWRITE,
VB2_SECDATA_SIZE));
RETURN_ON_FAILURE(write_secdata(FIRMWARE_NV_INDEX,
ctx->secdata,
VB2_SECDATA_SIZE));
VBDEBUG("TPM: factory initialization successful\n");
return TPM_SUCCESS;
}
/*
* SetupTPM starts the TPM and establishes the root of trust for the
* anti-rollback mechanism. SetupTPM can fail for three reasons. 1 A bug. 2 a
* TPM hardware failure. 3 An unexpected TPM state due to some attack. In
* general we cannot easily distinguish the kind of failure, so our strategy is
* to reboot in recovery mode in all cases. The recovery mode calls SetupTPM
* again, which executes (almost) the same sequence of operations. There is a
* good chance that, if recovery mode was entered because of a TPM failure, the
* failure will repeat itself. (In general this is impossible to guarantee
* because we have no way of creating the exact TPM initial state at the
* previous boot.) In recovery mode, we ignore the failure and continue, thus
* giving the recovery kernel a chance to fix things (that's why we don't set
* bGlobalLock). The choice is between a knowingly insecure device and a
* bricked device.
*
* As a side note, observe that we go through considerable hoops to avoid using
* the STCLEAR permissions for the index spaces. We do this to avoid writing
* to the TPM flashram at every reboot or wake-up, because of concerns about
* the durability of the NVRAM.
*/
uint32_t setup_tpm(struct vb2_context *ctx)
{
uint8_t disable;
uint8_t deactivated;
uint32_t result;
RETURN_ON_FAILURE(tlcl_lib_init());
#ifdef TEGRA_SOFT_REBOOT_WORKAROUND
result = tlcl_startup();
if (result == TPM_E_INVALID_POSTINIT) {
/*
* Some prototype hardware doesn't reset the TPM on a CPU
* reset. We do a hard reset to get around this.
*/
VBDEBUG("TPM: soft reset detected\n", result);
ctx->flags |= VB2_CONTEXT_SECDATA_WANTS_REBOOT;
return TPM_E_MUST_REBOOT;
} else if (result != TPM_SUCCESS) {
VBDEBUG("TPM: tlcl_startup returned %08x\n", result);
return result;
}
#else
RETURN_ON_FAILURE(tlcl_startup());
#endif
/*
* Some TPMs start the self test automatically at power on. In that case
* we don't need to call ContinueSelfTest. On some (other) TPMs,
* continue_self_test may block. In that case, we definitely don't want
* to call it here. For TPMs in the intersection of these two sets, we
* are screwed. (In other words: TPMs that require manually starting the
* self-test AND block will have poor performance until we split
* tlcl_send_receive() into send() and receive(), and have a state
* machine to control setup.)
*
* This comment is likely to become obsolete in the near future, so
* don't trust it. It may have not been updated.
*/
#ifdef TPM_MANUAL_SELFTEST
#ifdef TPM_BLOCKING_CONTINUESELFTEST
#warning "lousy TPM!"
#endif
RETURN_ON_FAILURE(tlcl_continue_self_test());
#endif
result = tlcl_assert_physical_presence();
if (result != TPM_SUCCESS) {
/*
* It is possible that the TPM was delivered with the physical
* presence command disabled. This tries enabling it, then
* tries asserting PP again.
*/
RETURN_ON_FAILURE(tlcl_physical_presence_cmd_enable());
RETURN_ON_FAILURE(tlcl_assert_physical_presence());
}
/* Check that the TPM is enabled and activated. */
RETURN_ON_FAILURE(tlcl_get_flags(&disable, &deactivated, NULL));
if (disable || deactivated) {
VBDEBUG("TPM: disabled (%d) or deactivated (%d). Fixing...\n",
disable, deactivated);
RETURN_ON_FAILURE(tlcl_set_enable());
RETURN_ON_FAILURE(tlcl_set_deactivated(0));
VBDEBUG("TPM: Must reboot to re-enable\n");
ctx->flags |= VB2_CONTEXT_SECDATA_WANTS_REBOOT;
return TPM_E_MUST_REBOOT;
}
VBDEBUG("TPM: SetupTPM() succeeded\n");
return TPM_SUCCESS;
}
uint32_t antirollback_read_space_firmware(struct vb2_context *ctx)
{
uint32_t rv;
rv = setup_tpm(ctx);
if (rv)
return rv;
/* Read the firmware space. */
rv = read_space_firmware(ctx);
if (rv == TPM_E_BADINDEX) {
/*
* This seems the first time we've run. Initialize the TPM.
*/
VBDEBUG("TPM: Not initialized yet.\n");
RETURN_ON_FAILURE(factory_initialize_tpm(ctx));
} else if (rv != TPM_SUCCESS) {
VBDEBUG("TPM: Firmware space in a bad state; giving up.\n");
//RETURN_ON_FAILURE(factory_initialize_tpm(ctx));
return TPM_E_CORRUPTED_STATE;
}
return TPM_SUCCESS;
}
uint32_t antirollback_write_space_firmware(struct vb2_context *ctx)
{
return write_secdata(FIRMWARE_NV_INDEX, ctx->secdata, VB2_SECDATA_SIZE);
}
uint32_t antirollback_lock_space_firmware()
{
return tlcl_set_global_lock();
}