blob: 9442b7792c3004483475d9465f8ae01a4a4a264a [file] [log] [blame]
/* Copyright (c) 2010-2011 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 "tlcl.h"
#include "tpm_bootmode.h"
#include "tss_constants.h"
#include "utility.h"
static int g_rollback_recovery_mode = 0;
/* disable MSVC warning on const logical expression (as in } while(0);) */
__pragma(warning (disable: 4127))
#define RETURN_ON_FAILURE(tpm_command) do { \
uint32_t result; \
if ((result = (tpm_command)) != TPM_SUCCESS) { \
VBDEBUG(("Rollback: %08x returned by " #tpm_command "\n", (int)result)); \
return result; \
} \
} while (0)
uint32_t TPMClearAndReenable(void) {
VBDEBUG(("TPM: Clear and re-enable\n"));
RETURN_ON_FAILURE(TlclForceClear());
RETURN_ON_FAILURE(TlclSetEnable());
RETURN_ON_FAILURE(TlclSetDeactivated(0));
return TPM_SUCCESS;
}
/* Like TlclWrite(), but checks for write errors due to hitting the 64-write
* limit and clears the TPM when that happens. This can only happen when the
* TPM is unowned, so it is OK to clear it (and we really have no choice).
* This is not expected to happen frequently, but it could happen.
*/
static uint32_t SafeWrite(uint32_t index, const void* data, uint32_t length) {
uint32_t result = TlclWrite(index, data, length);
if (result == TPM_E_MAXNVWRITES) {
RETURN_ON_FAILURE(TPMClearAndReenable());
return TlclWrite(index, data, length);
} else {
return result;
}
}
/* Similarly to SafeWrite(), this ensures we don't fail a DefineSpace because
* we hit the TPM write limit. This is even less likely to happen than with
* writes because we only define spaces once at initialization, but we'd rather
* be paranoid about this.
*/
static uint32_t SafeDefineSpace(uint32_t index, uint32_t perm, uint32_t size) {
uint32_t result = TlclDefineSpace(index, perm, size);
if (result == TPM_E_MAXNVWRITES) {
RETURN_ON_FAILURE(TPMClearAndReenable());
return TlclDefineSpace(index, perm, size);
} else {
return result;
}
}
/* Functions to read and write firmware and kernel spaces. */
static uint32_t ReadSpaceFirmware(RollbackSpaceFirmware* rsf) {
return TlclRead(FIRMWARE_NV_INDEX, rsf, sizeof(RollbackSpaceFirmware));
}
static uint32_t WriteSpaceFirmware(const RollbackSpaceFirmware* rsf) {
return SafeWrite(FIRMWARE_NV_INDEX, rsf, sizeof(RollbackSpaceFirmware));
}
#ifndef DISABLE_ROLLBACK_TPM
static uint32_t ReadSpaceKernel(RollbackSpaceKernel* rsk) {
return TlclRead(KERNEL_NV_INDEX, rsk, sizeof(RollbackSpaceKernel));
}
#endif
static uint32_t WriteSpaceKernel(const RollbackSpaceKernel* rsk) {
return SafeWrite(KERNEL_NV_INDEX, rsk, sizeof(RollbackSpaceKernel));
}
/* Performs one-time initializations. Creates the NVRAM spaces, and sets their
* initial values as needed. Sets the nvLocked bit and ensures the physical
* presence command is enabled and locked.
*/
static uint32_t OneTimeInitializeTPM(RollbackSpaceFirmware* rsf,
RollbackSpaceKernel* rsk) {
static const RollbackSpaceFirmware rsf_init = {
ROLLBACK_SPACE_FIRMWARE_VERSION, 0, 0, 0};
static const RollbackSpaceKernel rsk_init = {
ROLLBACK_SPACE_KERNEL_VERSION, ROLLBACK_SPACE_KERNEL_UID, 0, 0};
TPM_PERMANENT_FLAGS pflags;
uint32_t result;
VBDEBUG(("TPM: One-time 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 = TlclSelfTestFull();
if (result != TPM_SUCCESS)
return result;
result = TlclGetPermanentFlags(&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(TlclFinalizePhysicalPresence());
}
/* 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(TlclSetNvLocked());
}
/* Clear TPM owner, in case the TPM is already owned for some reason. */
VBDEBUG(("TPM: Clearing owner\n"));
RETURN_ON_FAILURE(TPMClearAndReenable());
/* Initializes the firmware and kernel spaces */
Memcpy(rsf, &rsf_init, sizeof(RollbackSpaceFirmware));
Memcpy(rsk, &rsk_init, sizeof(RollbackSpaceKernel));
/* Defines and sets firmware and kernel spaces */
RETURN_ON_FAILURE(SafeDefineSpace(FIRMWARE_NV_INDEX,
TPM_NV_PER_GLOBALLOCK | TPM_NV_PER_PPWRITE,
sizeof(RollbackSpaceFirmware)));
RETURN_ON_FAILURE(WriteSpaceFirmware(rsf));
RETURN_ON_FAILURE(SafeDefineSpace(KERNEL_NV_INDEX, TPM_NV_PER_PPWRITE,
sizeof(RollbackSpaceKernel)));
RETURN_ON_FAILURE(WriteSpaceKernel(rsk));
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 SetupTPM(int recovery_mode, int developer_mode,
RollbackSpaceFirmware* rsf) {
int rsf_dirty = 0;
uint8_t new_flags = 0;
uint8_t disable;
uint8_t deactivated;
uint32_t result;
VBDEBUG(("TPM: SetupTPM(r%d, d%d)\n", recovery_mode, developer_mode));
if (recovery_mode)
g_rollback_recovery_mode = 1; /* Global variables are usable in
* recovery mode */
RETURN_ON_FAILURE(TlclLibInit());
RETURN_ON_FAILURE(TlclStartup());
/* Some TPMs start the self test automatically at power on. In that case we
* don't need to call ContinueSelfTest. On some (other) TPMs,
* ContinueSelfTest may block. In that case, we definitely don't want to
* call it here. For TPMs in the intersection of these two sets, we're
* screwed. (In other words: TPMs that require manually starting the
* self-test AND block will have poor performance until we split
* TlclSendReceive() 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(TlclContinueSelfTest());
#endif
result = TlclAssertPhysicalPresence();
if (result != 0) {
/* 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(TlclPhysicalPresenceCMDEnable());
RETURN_ON_FAILURE(TlclAssertPhysicalPresence());
}
/* Checks that the TPM is enabled and activated. */
RETURN_ON_FAILURE(TlclGetFlags(&disable, &deactivated, NULL));
if (disable || deactivated) {
VBDEBUG(("TPM: disabled (%d) or deactivated (%d). Fixing...\n",
disable, deactivated));
RETURN_ON_FAILURE(TlclSetEnable());
RETURN_ON_FAILURE(TlclSetDeactivated(0));
VBDEBUG(("TPM: Must reboot to re-enable\n"));
return TPM_E_MUST_REBOOT;
}
/* Reads the firmware space. */
result = ReadSpaceFirmware(rsf);
if (TPM_E_BADINDEX == result) {
RollbackSpaceKernel rsk;
/* This is the first time we've run, and the TPM has not been
* initialized. This initializes it. */
VBDEBUG(("TPM: Not initialized yet.\n"));
RETURN_ON_FAILURE(OneTimeInitializeTPM(rsf, &rsk));
} else if (TPM_SUCCESS != result) {
VBDEBUG(("TPM: Firmware space in a bad state; giving up.\n"));
return TPM_E_CORRUPTED_STATE;
}
VBDEBUG(("TPM: Firmware space sv%d f%x v%x\n",
rsf->struct_version, rsf->flags, rsf->fw_versions));
/* Clears ownership if developer flag has toggled */
if ((developer_mode ? FLAG_LAST_BOOT_DEVELOPER : 0) !=
(rsf->flags & FLAG_LAST_BOOT_DEVELOPER)) {
VBDEBUG(("TPM: Developer flag changed; clearing owner.\n"));
RETURN_ON_FAILURE(TPMClearAndReenable());
}
/* Updates flags */
if (developer_mode)
new_flags |= FLAG_LAST_BOOT_DEVELOPER;
if (rsf->flags != new_flags) {
rsf->flags = new_flags;
rsf_dirty = 1;
}
/* If firmware space is dirty, this flushes it back to the TPM */
if (rsf_dirty) {
VBDEBUG(("TPM: Updating firmware space.\n"));
RETURN_ON_FAILURE(WriteSpaceFirmware(rsf));
}
VBDEBUG(("TPM: SetupTPM() succeeded\n"));
return TPM_SUCCESS;
}
/* disable MSVC warnings on unused arguments */
__pragma(warning (disable: 4100))
#ifdef DISABLE_ROLLBACK_TPM
/* Dummy implementations which don't support TPM rollback protection */
uint32_t RollbackS3Resume(void) {
#ifndef CHROMEOS_ENVIRONMENT
/* Initialize the TPM, but ignore return codes. In ChromeOS
* environment, don't even talk to the TPM. */
TlclLibInit();
TlclResume();
#endif
return TPM_SUCCESS;
}
uint32_t RollbackFirmwareSetup(int developer_mode, uint32_t* version) {
#ifndef CHROMEOS_ENVIRONMENT
/* Initializes the TPM, but ignores return codes. In ChromeOS
* environment, doesn't even talk to the TPM. */
TlclLibInit();
TlclStartup();
TlclContinueSelfTest();
#endif
*version = 0;
return TPM_SUCCESS;
}
uint32_t RollbackFirmwareWrite(uint32_t version) {
return TPM_SUCCESS;
}
uint32_t RollbackFirmwareLock(void) {
return TPM_SUCCESS;
}
uint32_t RollbackKernelRecovery(int developer_mode) {
#ifndef CHROMEOS_ENVIRONMENT
/* Initializes the TPM, but ignore return codes. In ChromeOS
* environment, doesn't even talk to the TPM. */
TlclLibInit();
TlclStartup();
TlclSelfTestFull();
#endif
return TPM_SUCCESS;
}
uint32_t RollbackKernelRead(uint32_t* version) {
*version = 0;
return TPM_SUCCESS;
}
uint32_t RollbackKernelWrite(uint32_t version) {
return TPM_SUCCESS;
}
uint32_t RollbackKernelLock(void) {
return TPM_SUCCESS;
}
#else
uint32_t RollbackS3Resume(void) {
uint32_t result;
RETURN_ON_FAILURE(TlclLibInit());
result = TlclResume();
if (result == TPM_E_INVALID_POSTINIT) {
/* We're on a platform where the TPM maintains power in S3, so
it's already initialized. */
return TPM_SUCCESS;
}
return result;
}
uint32_t RollbackFirmwareSetup(int developer_mode, uint32_t* version) {
RollbackSpaceFirmware rsf;
RETURN_ON_FAILURE(SetupTPM(0, developer_mode, &rsf));
*version = rsf.fw_versions;
VBDEBUG(("TPM: RollbackFirmwareSetup %x\n", (int)rsf.fw_versions));
return TPM_SUCCESS;
}
uint32_t RollbackFirmwareWrite(uint32_t version) {
RollbackSpaceFirmware rsf;
RETURN_ON_FAILURE(ReadSpaceFirmware(&rsf));
VBDEBUG(("TPM: RollbackFirmwareWrite %x --> %x\n", (int)rsf.fw_versions,
(int)version));
rsf.fw_versions = version;
return WriteSpaceFirmware(&rsf);
}
uint32_t RollbackFirmwareLock(void) {
return TlclSetGlobalLock();
}
uint32_t RollbackKernelRecovery(int developer_mode) {
uint32_t rvs, rve;
RollbackSpaceFirmware rsf;
/* In recovery mode we ignore TPM malfunctions or corruptions, and *
* leave the TPM complelely unlocked; we call neither
* TlclSetGlobalLock() nor TlclLockPhysicalPresence(). The recovery
* kernel will fix the TPM (if needed) and lock it ASAP. We leave
* Physical Presence on in either case. */
rvs = SetupTPM(1, developer_mode, &rsf);
rve = SetTPMBootModeState(developer_mode,
1, /* Recovery Mode Status. */
0); /* In recovery mode, there is no RW firmware
* keyblock flag. */
return (TPM_SUCCESS == rvs) ? rve : rvs;
}
uint32_t RollbackKernelRead(uint32_t* version) {
if (g_rollback_recovery_mode) {
*version = 0;
} else {
RollbackSpaceKernel rsk;
uint32_t perms;
/* Read the kernel space and verify its permissions. If the kernel
* space has the wrong permission, or it doesn't contain the right
* identifier, we give up. This will need to be fixed by the
* recovery kernel. We have to worry about this because at any time
* (even with PP turned off) the TPM owner can remove and redefine a
* PP-protected space (but not write to it). */
RETURN_ON_FAILURE(ReadSpaceKernel(&rsk));
RETURN_ON_FAILURE(TlclGetPermissions(KERNEL_NV_INDEX, &perms));
if (TPM_NV_PER_PPWRITE != perms || ROLLBACK_SPACE_KERNEL_UID != rsk.uid)
return TPM_E_CORRUPTED_STATE;
*version = rsk.kernel_versions;
VBDEBUG(("TPM: RollbackKernelRead %x\n", (int)rsk.kernel_versions));
}
return TPM_SUCCESS;
}
uint32_t RollbackKernelWrite(uint32_t version) {
if (g_rollback_recovery_mode) {
return TPM_SUCCESS;
} else {
RollbackSpaceKernel rsk;
RETURN_ON_FAILURE(ReadSpaceKernel(&rsk));
VBDEBUG(("TPM: RollbackKernelWrite %x --> %x\n", (int)rsk.kernel_versions,
(int)version));
rsk.kernel_versions = version;
return WriteSpaceKernel(&rsk);
}
}
uint32_t RollbackKernelLock(void) {
if (g_rollback_recovery_mode) {
return TPM_SUCCESS;
} else {
return TlclLockPhysicalPresence();
}
}
#endif // DISABLE_ROLLBACK_TPM