tspi.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <console/console.h>
#include <security/tpm/tspi/crtm.h>
#include <security/tpm/tspi.h>
#include <security/tpm/tss.h>
#include <assert.h>
#include <security/vboot/misc.h>
#include <vb2_api.h>
#include <vb2_sha.h>
 
#if CONFIG(TPM1)
static uint32_t tpm1_invoke_state_machine(void)
{
        uint8_t disabled;
        uint8_t deactivated;
        uint32_t result = TPM_SUCCESS;
 
        /* Check that the TPM is enabled and activated. */
        result = tlcl_get_flags(&disabled, &deactivated, NULL);
        if (result != TPM_SUCCESS) {
                printk(BIOS_ERR, "TPM: Can't read capabilities.\n");
                return result;
        }
 
        if (disabled) {
                printk(BIOS_INFO, "TPM: is disabled. Enabling...\n");
 
                result = tlcl_set_enable();
                if (result != TPM_SUCCESS) {
                        printk(BIOS_ERR, "TPM: Can't set enabled state.\n");
                        return result;
                }
        }
 
        if (!!deactivated != CONFIG(TPM_DEACTIVATE)) {
                printk(BIOS_INFO,
                       "TPM: Unexpected TPM deactivated state. Toggling...\n");
                result = tlcl_set_deactivated(!deactivated);
                if (result != TPM_SUCCESS) {
                        printk(BIOS_ERR,
                               "TPM: Can't toggle deactivated state.\n");
                        return result;
                }
 
                deactivated = !deactivated;
                result = TPM_E_MUST_REBOOT;
        }
 
        return result;
}
#endif
 
static uint32_t tpm_setup_s3_helper(void)
{
        uint32_t result;
 
        result = tlcl_resume();
        switch (result) {
        case TPM_SUCCESS:
                break;
 
        case TPM_E_INVALID_POSTINIT:
                /*
                 * We're on a platform where the TPM maintains power
                 * in S3, so it's already initialized.
                 */
                printk(BIOS_INFO, "TPM: Already initialized.\n");
                result = TPM_SUCCESS;
                break;
 
        default:
                printk(BIOS_ERR, "TPM: Resume failed (%#x).\n", result);
                break;
        }
 
        return result;
}
 
static uint32_t tpm_setup_epilogue(uint32_t result)
{
        if (result != TPM_SUCCESS)
                post_code(POST_TPM_FAILURE);
        else
                printk(BIOS_INFO, "TPM: setup succeeded\n");
 
        return result;
}
 
static int tpm_is_setup;
static inline int tspi_tpm_is_setup(void)
{
        /*
         * vboot_logic_executed() only starts returning true at the end of
         * verstage, but the vboot logic itself already wants to extend PCRs
         * before that. So in the stage where verification actually runs, we
         * need to check tpm_is_setup. Skip that check in all other stages so
         * this whole function can be evaluated at compile time.
         */
        if (CONFIG(VBOOT)) {
                if (verification_should_run())
                        return tpm_is_setup;
                return vboot_logic_executed();
        }
 
        if (CONFIG(TPM_MEASURED_BOOT_INIT_BOOTBLOCK))
                return ENV_BOOTBLOCK ? tpm_is_setup : 1;
 
        if (ENV_RAMSTAGE)
                return tpm_is_setup;
 
        return 0;
}
 
/*
 * tpm_setup starts the TPM and establishes the root of trust for the
 * anti-rollback mechanism.  tpm_setup 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 tpm_setup
 * 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 tpm_setup(int s3flag)
{
        uint32_t result;
 
        result = tlcl_lib_init();
        if (result != TPM_SUCCESS) {
                printk(BIOS_ERR, "TPM: Can't initialize.\n");
                return tpm_setup_epilogue(result);
        }
 
        /* Handle special init for S3 resume path */
        if (s3flag) {
                printk(BIOS_INFO, "TPM: Handle S3 resume.\n");
                return tpm_setup_epilogue(tpm_setup_s3_helper());
        }
 
        result = tlcl_startup();
        if (CONFIG(TPM_STARTUP_IGNORE_POSTINIT)
            && result == TPM_E_INVALID_POSTINIT) {
                printk(BIOS_DEBUG, "TPM: ignoring invalid POSTINIT\n");
                result = TPM_SUCCESS;
        }
        if (result != TPM_SUCCESS) {
                printk(BIOS_ERR, "TPM: Can't run startup command.\n");
                return tpm_setup_epilogue(result);
        }
 
        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.
                 */
                result = tlcl_physical_presence_cmd_enable();
                if (result != TPM_SUCCESS) {
                        printk(BIOS_ERR, "TPM: Can't enable physical presence command.\n");
                        return tpm_setup_epilogue(result);
                }
 
                result = tlcl_assert_physical_presence();
                if (result != TPM_SUCCESS) {
                        printk(BIOS_ERR, "TPM: Can't assert physical presence.\n");
                        return tpm_setup_epilogue(result);
                }
        }
 
#if CONFIG(TPM1)
        result = tpm1_invoke_state_machine();
#endif
        if (CONFIG(TPM_MEASURED_BOOT))
                result = tspi_measure_cache_to_pcr();
 
        tpm_is_setup = 1;
        return tpm_setup_epilogue(result);
}
 
uint32_t tpm_clear_and_reenable(void)
{
        uint32_t result;
 
        printk(BIOS_INFO, "TPM: Clear and re-enable\n");
        result = tlcl_force_clear();
        if (result != TPM_SUCCESS) {
                printk(BIOS_ERR, "TPM: Can't initiate a force clear.\n");
                return result;
        }
 
#if CONFIG(TPM1)
        result = tlcl_set_enable();
        if (result != TPM_SUCCESS) {
                printk(BIOS_ERR, "TPM: Can't set enabled state.\n");
                return result;
        }
 
        result = tlcl_set_deactivated(0);
        if (result != TPM_SUCCESS) {
                printk(BIOS_ERR, "TPM: Can't set deactivated state.\n");
                return result;
        }
#endif
 
        return TPM_SUCCESS;
}
 
uint32_t tpm_extend_pcr(int pcr, enum vb2_hash_algorithm digest_algo,
                        const uint8_t *digest, size_t digest_len, const char *name)
{
        uint32_t result;
 
        if (!digest)
                return TPM_E_IOERROR;
 
        if (tspi_tpm_is_setup()) {
                result = tlcl_lib_init();
                if (result != TPM_SUCCESS) {
                        printk(BIOS_ERR, "TPM: Can't initialize library.\n");
                        return result;
                }
 
                printk(BIOS_DEBUG, "TPM: Extending digest for `%s` into PCR %d\n", name, pcr);
                result = tlcl_extend(pcr, digest, NULL);
                if (result != TPM_SUCCESS) {
                        printk(BIOS_ERR, "TPM: Extending hash for `%s` into PCR %d failed.\n",
                               name, pcr);
                        return result;
                }
        }
 
        if (CONFIG(TPM_MEASURED_BOOT))
                tcpa_log_add_table_entry(name, pcr, digest_algo,
                        digest, digest_len);
 
        printk(BIOS_DEBUG, "TPM: Digest of `%s` to PCR %d %s\n",
               name, pcr, tspi_tpm_is_setup() ? "measured" : "logged");
 
        return TPM_SUCCESS;
}
 
#if CONFIG(VBOOT_LIB)
uint32_t tpm_measure_region(const struct region_device *rdev, uint8_t pcr,
                            const char *rname)
{
        uint8_t digest[TPM_PCR_MAX_LEN], digest_len;
        uint8_t buf[HASH_DATA_CHUNK_SIZE];
        uint32_t offset;
        size_t len;
        struct vb2_digest_context ctx;
 
        if (!rdev || !rname)
                return TPM_E_INVALID_ARG;
 
        digest_len = vb2_digest_size(TPM_MEASURE_ALGO);
        assert(digest_len <= sizeof(digest));
        if (vb2_digest_init(&ctx, TPM_MEASURE_ALGO)) {
                printk(BIOS_ERR, "TPM: Error initializing hash.\n");
                return TPM_E_HASH_ERROR;
        }
        /*
         * Though one can mmap the full needed region on x86 this is not the
         * case for e.g. ARM. In order to make this code as universal as
         * possible across different platforms read the data to hash in chunks.
         */
        for (offset = 0; offset < region_device_sz(rdev); offset += len) {
                len = MIN(sizeof(buf), region_device_sz(rdev) - offset);
                if (rdev_readat(rdev, buf, offset, len) < 0) {
                        printk(BIOS_ERR, "TPM: Not able to read region %s.\n",
                               rname);
                        return TPM_E_READ_FAILURE;
                }
                if (vb2_digest_extend(&ctx, buf, len)) {
                        printk(BIOS_ERR, "TPM: Error extending hash.\n");
                        return TPM_E_HASH_ERROR;
                }
        }
        if (vb2_digest_finalize(&ctx, digest, digest_len)) {
                printk(BIOS_ERR, "TPM: Error finalizing hash.\n");
                return TPM_E_HASH_ERROR;
        }
        return tpm_extend_pcr(pcr, TPM_MEASURE_ALGO, digest, digest_len, rname);
}
#endif /* VBOOT_LIB */