firmware/2lib/2misc.c

/* Copyright (c) 2014 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.
 *
 * Misc functions which need access to vb2_context but are not public APIs
 */

#include "2sysincludes.h"
#include "2api.h"
#include "2common.h"
#include "2misc.h"
#include "2nvstorage.h"
#include "2secdata.h"
#include "2sha.h"
#include "2rsa.h"

int vb2_validate_gbb_signature(uint8_t *sig) {
	const static uint8_t sig_xor[VB2_GBB_SIGNATURE_SIZE] =
			VB2_GBB_XOR_SIGNATURE;
	int i;
	for (i = 0; i < VB2_GBB_SIGNATURE_SIZE; i++) {
		if (sig[i] != (sig_xor[i] ^ VB2_GBB_XOR_CHARS[i]))
			return VB2_ERROR_GBB_MAGIC;
	}
	return VB2_SUCCESS;
}

void vb2_workbuf_from_ctx(struct vb2_context *ctx, struct vb2_workbuf *wb)
{
	vb2_workbuf_init(wb, ctx->workbuf + ctx->workbuf_used,
			 ctx->workbuf_size - ctx->workbuf_used);
}

int vb2_read_gbb_header(struct vb2_context *ctx, struct vb2_gbb_header *gbb)
{
	int rv;

	/* Read the entire header */
	rv = vb2ex_read_resource(ctx, VB2_RES_GBB, 0, gbb, sizeof(*gbb));
	if (rv)
		return rv;

	/* Make sure it's really a GBB */
	rv = vb2_validate_gbb_signature(gbb->signature);
	if (rv)
		return rv;

	/* Check for compatible version */
	if (gbb->major_version != VB2_GBB_MAJOR_VER)
		return VB2_ERROR_GBB_VERSION;

	/* Current code is not backwards-compatible to 1.0 headers */
	if (gbb->minor_version < VB2_GBB_MINOR_VER)
		return VB2_ERROR_GBB_TOO_OLD;

	/*
	 * Header size should be at least as big as we expect.  It could be
	 * bigger, if the header has grown.
	 */
	if (gbb->header_size < sizeof(*gbb))
		return VB2_ERROR_GBB_HEADER_SIZE;

	return VB2_SUCCESS;
}

void vb2_fail(struct vb2_context *ctx, uint8_t reason, uint8_t subcode)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);

	/* If NV data hasn't been initialized, initialize it now */
	if (!(sd->status & VB2_SD_STATUS_NV_INIT))
		vb2_nv_init(ctx);

	/* See if we were far enough in the boot process to choose a slot */
	if (sd->status & VB2_SD_STATUS_CHOSE_SLOT) {

		/* Boot failed */
		vb2_nv_set(ctx, VB2_NV_FW_RESULT, VB2_FW_RESULT_FAILURE);

		/* Use up remaining tries */
		vb2_nv_set(ctx, VB2_NV_TRY_COUNT, 0);

		/*
		 * Try the other slot next time.  We'll alternate
		 * between slots, which may help if one or both slots is
		 * flaky.
		 */
		vb2_nv_set(ctx, VB2_NV_TRY_NEXT, 1 - sd->fw_slot);

		/*
		 * If we didn't try the other slot last boot, or we tried it
		 * and it didn't fail, try it next boot.
		 */
		if (sd->last_fw_slot != 1 - sd->fw_slot ||
		    sd->last_fw_result != VB2_FW_RESULT_FAILURE)
			return;
	}

	/*
	 * If we're still here, we failed before choosing a slot, or both
	 * this slot and the other slot failed in successive boots.  So we
	 * need to go to recovery.
	 *
	 * Set a recovery reason and subcode only if they're not already set.
	 * If recovery is already requested, it's a more specific error code
	 * than later code is providing and we shouldn't overwrite it.
	 */
	VB2_DEBUG("Both slots are bad. Need recovery\n");
	if (!vb2_nv_get(ctx, VB2_NV_RECOVERY_REQUEST)) {
		vb2_nv_set(ctx, VB2_NV_RECOVERY_REQUEST, reason);
		vb2_nv_set(ctx, VB2_NV_RECOVERY_SUBCODE, subcode);
	}
}

int vb2_init_context(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);

	/* Don't do anything if the context has already been initialized */
	if (ctx->workbuf_used)
		return VB2_SUCCESS;

	/*
	 * Workbuf had better be big enough for our shared data struct and
	 * aligned.  Not much we can do if it isn't; we'll die before we can
	 * store a recovery reason.
	 */
	if (ctx->workbuf_size < sizeof(*sd))
		return VB2_ERROR_INITCTX_WORKBUF_SMALL;
	if (!vb_aligned(ctx->workbuf, VB2_WORKBUF_ALIGN))
		return VB2_ERROR_INITCTX_WORKBUF_ALIGN;

	/* Initialize the shared data at the start of the work buffer */
	memset(sd, 0, sizeof(*sd));
	ctx->workbuf_used = sizeof(*sd);
	return VB2_SUCCESS;
}

void vb2_check_recovery(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);

	/*
	 * Read the current recovery request, unless there's already been a
	 * failure earlier in the boot process.
	 */
	if (!sd->recovery_reason)
		sd->recovery_reason = vb2_nv_get(ctx, VB2_NV_RECOVERY_REQUEST);

	/* Clear the recovery request so we don't get stuck in recovery mode */
	if (sd->recovery_reason) {
		vb2_nv_set(ctx, VB2_NV_RECOVERY_REQUEST,
			   VB2_RECOVERY_NOT_REQUESTED);
		/*
		 * Note that we ignore failures clearing the request.  We only
		 * hit this code path if recovery mode has already been
		 * requested, so what more can we do?  Don't want to obscure
		 * the original reason for going into recovery mode.
		 */
	}

	/* If forcing recovery, override recovery reason */
	if (ctx->flags & VB2_CONTEXT_FORCE_RECOVERY_MODE) {
		sd->recovery_reason = VB2_RECOVERY_RO_MANUAL;
		sd->flags = VB2_SD_FLAG_MANUAL_RECOVERY;
	}

	/* If recovery reason is non-zero, tell caller we need recovery mode */
	if (sd->recovery_reason)
		ctx->flags |= VB2_CONTEXT_RECOVERY_MODE;
}

int vb2_fw_parse_gbb(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);
	struct vb2_gbb_header *gbb;
	struct vb2_workbuf wb;
	int rv;

	vb2_workbuf_from_ctx(ctx, &wb);

	/* Read GBB into next chunk of work buffer */
	gbb = vb2_workbuf_alloc(&wb, sizeof(*gbb));
	if (!gbb)
		return VB2_ERROR_GBB_WORKBUF;

	rv = vb2_read_gbb_header(ctx, gbb);
	if (rv)
		return rv;

	/* Extract the only things we care about at firmware time */
	sd->gbb_flags = gbb->flags;
	sd->gbb_rootkey_offset = gbb->rootkey_offset;
	sd->gbb_rootkey_size = gbb->rootkey_size;

	return VB2_SUCCESS;
}

int vb2_check_dev_switch(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);
	uint32_t flags;
	uint32_t old_flags;
	int is_dev = 0;
	int rv;

	/* Read secure flags */
	rv = vb2_secdata_get(ctx, VB2_SECDATA_FLAGS, &flags);
	if (rv)
		return rv;

	old_flags = flags;

	/* Handle dev disable request */
	if (vb2_nv_get(ctx, VB2_NV_DISABLE_DEV_REQUEST)) {
		flags &= ~VB2_SECDATA_FLAG_DEV_MODE;

		/* Clear the request */
		vb2_nv_set(ctx, VB2_NV_DISABLE_DEV_REQUEST, 0);
	}

	/* Check virtual dev switch */
	if (flags & VB2_SECDATA_FLAG_DEV_MODE)
		is_dev = 1;

	/* Handle forcing dev mode via physical switch */
	if (ctx->flags & VB2_CONTEXT_FORCE_DEVELOPER_MODE)
		is_dev = 1;

	/* Check if GBB is forcing dev mode */
	if (sd->gbb_flags & VB2_GBB_FLAG_FORCE_DEV_SWITCH_ON)
		is_dev = 1;

	/* Handle whichever mode we end up in */
	if (is_dev) {
		/* Developer mode */
		sd->flags |= VB2_SD_DEV_MODE_ENABLED;
		ctx->flags |= VB2_CONTEXT_DEVELOPER_MODE;

		flags |= VB2_SECDATA_FLAG_LAST_BOOT_DEVELOPER;
	} else {
		/* Normal mode */
		flags &= ~VB2_SECDATA_FLAG_LAST_BOOT_DEVELOPER;

		/*
		 * Disable dev_boot_* flags.  This ensures they will be
		 * initially disabled if the user later transitions back into
		 * developer mode.
		 */
		vb2_nv_set(ctx, VB2_NV_DEV_BOOT_USB, 0);
		vb2_nv_set(ctx, VB2_NV_DEV_BOOT_LEGACY, 0);
		vb2_nv_set(ctx, VB2_NV_DEV_BOOT_SIGNED_ONLY, 0);
	}

	if (flags != old_flags) {
		/*
		 * Just changed dev mode state.  Clear TPM owner.  This must be
		 * done here instead of simply passing a flag to
		 * vb2_check_tpm_clear(), because we don't want to update
		 * last_boot_developer and then fail to clear the TPM owner.
		 */
		rv = vb2ex_tpm_clear_owner(ctx);
		if (rv) {
			/*
			 * Note that this truncates rv to 8 bit.  Which is not
			 * as useful as the full error code, but we don't have
			 * NVRAM space to store the full 32-bit code.
			 */
			vb2_fail(ctx, VB2_RECOVERY_TPM_CLEAR_OWNER, rv);
			return rv;
		}

		/* Save new flags */
		rv = vb2_secdata_set(ctx, VB2_SECDATA_FLAGS, flags);
		if (rv)
			return rv;
	}

	return VB2_SUCCESS;
}

int vb2_check_tpm_clear(struct vb2_context *ctx)
{
	int rv;

	/* Check if we've been asked to clear the owner */
	if (!vb2_nv_get(ctx, VB2_NV_CLEAR_TPM_OWNER_REQUEST))
		return VB2_SUCCESS;  /* No need to clear */

	/* Request applies one time only */
	vb2_nv_set(ctx, VB2_NV_CLEAR_TPM_OWNER_REQUEST, 0);

	/* Try clearing */
	rv = vb2ex_tpm_clear_owner(ctx);
	if (rv) {
		/*
		 * Note that this truncates rv to 8 bit.  Which is not as
		 * useful as the full error code, but we don't have NVRAM space
		 * to store the full 32-bit code.
		 */
		vb2_fail(ctx, VB2_RECOVERY_TPM_CLEAR_OWNER, rv);
		return rv;
	}

	/* Clear successful */
	vb2_nv_set(ctx, VB2_NV_CLEAR_TPM_OWNER_DONE, 1);
	return VB2_SUCCESS;
}

int vb2_select_fw_slot(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);
	uint32_t tries;

	/* Get result of last boot */
	sd->last_fw_slot = vb2_nv_get(ctx, VB2_NV_FW_TRIED);
	sd->last_fw_result = vb2_nv_get(ctx, VB2_NV_FW_RESULT);

	/* Clear result, since we don't know what will happen this boot */
	vb2_nv_set(ctx, VB2_NV_FW_RESULT, VB2_FW_RESULT_UNKNOWN);

	/* Get slot to try */
	sd->fw_slot = vb2_nv_get(ctx, VB2_NV_TRY_NEXT);

	/* Check try count */
	tries = vb2_nv_get(ctx, VB2_NV_TRY_COUNT);

	if (sd->last_fw_result == VB2_FW_RESULT_TRYING &&
	    sd->last_fw_slot == sd->fw_slot &&
	    tries == 0) {
		/*
		 * We used up our last try on the previous boot, so fall back
		 * to the other slot this boot.
		 */
		sd->fw_slot = 1 - sd->fw_slot;
		vb2_nv_set(ctx, VB2_NV_TRY_NEXT, sd->fw_slot);
	}

	if (tries > 0) {
		/* Still trying this firmware */
		vb2_nv_set(ctx, VB2_NV_FW_RESULT, VB2_FW_RESULT_TRYING);

		/* Decrement non-zero try count */
		vb2_nv_set(ctx, VB2_NV_TRY_COUNT, tries - 1);
	}

	/* Set context flag if we're using slot B */
	if (sd->fw_slot)
		ctx->flags |= VB2_CONTEXT_FW_SLOT_B;

	/* Set status flag */
	sd->status |= VB2_SD_STATUS_CHOSE_SLOT;

	return VB2_SUCCESS;
}

int vb2_verify_fw_keyblock(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);
	struct vb2_workbuf wb;

	uint8_t *key_data;
	uint32_t key_size;
	struct vb2_packed_key *packed_key;
	struct vb2_public_key root_key;

	struct vb2_keyblock *kb;
	uint32_t block_size;

	uint32_t sec_version;
	int rv;

	vb2_workbuf_from_ctx(ctx, &wb);

	/* Read the root key */
	key_size = sd->gbb_rootkey_size;
	key_data = vb2_workbuf_alloc(&wb, key_size);
	if (!key_data)
		return VB2_ERROR_FW_KEYBLOCK_WORKBUF_ROOT_KEY;

	rv = vb2ex_read_resource(ctx, VB2_RES_GBB, sd->gbb_rootkey_offset,
				 key_data, key_size);
	if (rv)
		return rv;

	/* Unpack the root key */
	rv = vb2_unpack_key(&root_key, key_data, key_size);
	if (rv)
		return rv;

	/* Load the firmware keyblock header after the root key */
	kb = vb2_workbuf_alloc(&wb, sizeof(*kb));
	if (!kb)
		return VB2_ERROR_FW_KEYBLOCK_WORKBUF_HEADER;

	rv = vb2ex_read_resource(ctx, VB2_RES_FW_VBLOCK, 0, kb, sizeof(*kb));
	if (rv)
		return rv;

	block_size = kb->keyblock_size;

	/*
	 * Load the entire keyblock, now that we know how big it is.  Note that
	 * we're loading the entire keyblock instead of just the piece after
	 * the header.  That means we re-read the header.  But that's a tiny
	 * amount of data, and it makes the code much more straightforward.
	 */
	kb = vb2_workbuf_realloc(&wb, sizeof(*kb), block_size);
	if (!kb)
		return VB2_ERROR_FW_KEYBLOCK_WORKBUF;

	rv = vb2ex_read_resource(ctx, VB2_RES_FW_VBLOCK, 0, kb, block_size);
	if (rv)
		return rv;

	/* Verify the keyblock */
	rv = vb2_verify_keyblock(kb, block_size, &root_key, &wb);
	if (rv)
		return rv;

	/* Read the secure key version */
	rv = vb2_secdata_get(ctx, VB2_SECDATA_VERSIONS, &sec_version);
	if (rv)
		return rv;

	/* Key version is the upper 16 bits of the composite firmware version */
	if (kb->data_key.key_version > 0xffff)
		return VB2_ERROR_FW_KEYBLOCK_VERSION_RANGE;
	if (kb->data_key.key_version < (sec_version >> 16))
		return VB2_ERROR_FW_KEYBLOCK_VERSION_ROLLBACK;

	sd->fw_version = kb->data_key.key_version << 16;

	/*
	 * Save the data key in the work buffer.  This overwrites the root key
	 * we read above.  That's ok, because now that we have the data key we
	 * no longer need the root key.
	 */
	packed_key = (struct vb2_packed_key *)key_data;

	packed_key->algorithm = kb->data_key.algorithm;
	packed_key->key_version = kb->data_key.key_version;
	packed_key->key_size = kb->data_key.key_size;

	/*
	 * Use memmove() instead of memcpy().  In theory, the destination will
	 * never overlap because with the source because the root key is likely
	 * to be at least as large as the data key, but there's no harm here in
	 * being paranoid.
	 */
	memmove(key_data + packed_key->key_offset,
		(uint8_t*)&kb->data_key + kb->data_key.key_offset,
		packed_key->key_size);

	/* Save the packed key offset and size */
	sd->workbuf_data_key_offset = vb2_offset_of(ctx->workbuf, key_data);
	sd->workbuf_data_key_size =
		packed_key->key_offset + packed_key->key_size;

	/* Preamble follows the keyblock in the vblock */
	sd->vblock_preamble_offset = kb->keyblock_size;

	/* Data key will persist in the workbuf after we return */
	ctx->workbuf_used = sd->workbuf_data_key_offset +
		sd->workbuf_data_key_size;

	return VB2_SUCCESS;
}

// TODO: Terrible that this and the low-level verification want to have the
// same function name.  Pick a better name...
int vb2_verify_fw_preamble2(struct vb2_context *ctx)
{
	struct vb2_shared_data *sd = vb2_get_sd(ctx);
	struct vb2_workbuf wb;

	uint8_t *key_data = ctx->workbuf + sd->workbuf_data_key_offset;
	uint32_t key_size = sd->workbuf_data_key_size;
	struct vb2_public_key data_key;

	/* Preamble goes in the next unused chunk of work buffer */
	struct vb2_fw_preamble *pre;
	uint32_t pre_size;

	uint32_t sec_version;
	int rv;

	vb2_workbuf_from_ctx(ctx, &wb);

	/* Unpack the firmware data key */
	if (!sd->workbuf_data_key_size)
		return VB2_ERROR_FW_PREAMBLE2_DATA_KEY;

	rv = vb2_unpack_key(&data_key, key_data, key_size);
	if (rv)
		return rv;

	/* Load the firmware preamble header */
	pre = vb2_workbuf_alloc(&wb, sizeof(*pre));
	if (!pre)
		return VB2_ERROR_FW_PREAMBLE2_WORKBUF_HEADER;

	rv = vb2ex_read_resource(ctx, VB2_RES_FW_VBLOCK,
				 sd->vblock_preamble_offset,
				 pre, sizeof(*pre));
	if (rv)
		return rv;

	pre_size = pre->preamble_size;

	/* Load the entire firmware preamble, now that we know how big it is */
	pre = vb2_workbuf_realloc(&wb, sizeof(*pre), pre_size);
	if (!pre)
		return VB2_ERROR_FW_PREAMBLE2_WORKBUF;

	rv = vb2ex_read_resource(ctx, VB2_RES_FW_VBLOCK,
				 sd->vblock_preamble_offset,
				 pre, pre_size);
	if (rv)
		return rv;

	/* Work buffer now contains the data subkey data and the preamble */

	/* Verify the preamble */
	rv = vb2_verify_fw_preamble(pre, pre_size, &data_key, &wb);
	if (rv)
		return rv;

	/* Read the secure key version */
	rv = vb2_secdata_get(ctx, VB2_SECDATA_VERSIONS, &sec_version);
	if (rv)
		return rv;

	/*
	 * Firmware version is the lower 16 bits of the composite firmware
	 * version.
	 */
	if (pre->firmware_version > 0xffff)
		return VB2_ERROR_FW_PREAMBLE2_VERSION_RANGE;

	/* Combine with the key version from vb2_verify_fw_keyblock() */
	sd->fw_version |= pre->firmware_version;
	if (sd->fw_version < sec_version)
		return VB2_ERROR_FW_PREAMBLE2_VERSION_ROLLBACK;

	/*
	 * If this is a newer version than in secure storage, and we
	 * successfully booted the same slot last boot, roll forward the
	 * version in secure storage.
	 */
	if (sd->fw_version > sec_version &&
	    sd->last_fw_slot == sd->fw_slot &&
	    sd->last_fw_result == VB2_FW_RESULT_SUCCESS) {

		rv = vb2_secdata_set(ctx, VB2_SECDATA_VERSIONS, sd->fw_version);
		if (rv)
			return rv;
	}

	/* Keep track of where we put the preamble */
	sd->workbuf_preamble_offset = vb2_offset_of(ctx->workbuf, pre);
	sd->workbuf_preamble_size = pre_size;

	/* Preamble will persist in work buffer after we return */
	ctx->workbuf_used = sd->workbuf_preamble_offset + pre_size;

	return VB2_SUCCESS;
}