common/rwsig.c - chromiumos/platform/ec - Git at Google

 /* 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.
  */

 /*
  * Implementation of the RW firmware signature verification and jump.
  */

 #include "console.h"
 #include "ec_commands.h"
 #include "flash.h"
 #include "rollback.h"
 #include "rsa.h"
 #include "rwsig.h"
 #include "sha256.h"
 #include "shared_mem.h"
 #include "system.h"
 #include "task.h"
 #include "usb_pd.h"
 #include "util.h"
 #include "vb21_struct.h"
 #include "version.h"

 /* Console output macros */
 #define CPRINTF(format, args...) cprintf(CC_SYSTEM, format, ## args)
 #define CPRINTS(format, args...) cprints(CC_SYSTEM, format, ## args)

 /* RW firmware reset vector */
 static uint32_t * const rw_rst =
 	(uint32_t *)(CONFIG_PROGRAM_MEMORY_BASE + CONFIG_RW_MEM_OFF + 4);


 void rwsig_jump_now(void)
 {
 	/* Protect all flash before jumping to RW. */

 	/*
 	 * This may do nothing if WP is not enabled, RO is not
 	 * protected, or if ALL_AT_BOOT is already set.
 	 */
 	flash_set_protect(EC_FLASH_PROTECT_ALL_AT_BOOT, -1);

 	if (!(flash_get_protect() & EC_FLASH_PROTECT_ALL_NOW) &&
 	      flash_get_protect() & EC_FLASH_PROTECT_ALL_AT_BOOT) {
 		/*
 		 * If flash protection is still not enabled (some chips may
 		 * be able to enable it immediately), reboot.
 		 */
 		cflush();
 		system_reset(SYSTEM_RESET_HARD | SYSTEM_RESET_PRESERVE_FLAGS);
 	}

 	/* When system is locked, only boot to RW is all flash is protected. */
 	if (!system_is_locked() ||
 	    flash_get_protect() & EC_FLASH_PROTECT_ALL_NOW)
 		system_run_image_copy(SYSTEM_IMAGE_RW);
 }

 /*
  * Check that memory between rwdata[start] and rwdata[len-1] is filled
  * with ones. data, start and len must be aligned on 4-byte boundary.
  */
 static int check_padding(const uint8_t *data,
 			 unsigned int start, unsigned int len)
 {
 	unsigned int i;
 	const uint32_t *data32 = (const uint32_t *)data;

 	if ((start % 4) != 0 || (len % 4) != 0)
 		return 0;

 	for (i = start/4; i < len/4; i++) {
 		if (data32[i] != 0xffffffff)
 			return 0;
 	}

 	return 1;
 }

 int rwsig_check_signature(void)
 {
 	struct sha256_ctx ctx;
 	int res;
 	const struct rsa_public_key *key;
 	const uint8_t *sig;
 	uint8_t *hash;
 	uint32_t *rsa_workbuf = NULL;
 	const uint8_t *rwdata = (uint8_t *)CONFIG_PROGRAM_MEMORY_BASE
 					+ CONFIG_RW_MEM_OFF;
 	int good = 0;

 	unsigned int rwlen;
 #ifdef CONFIG_RWSIG_TYPE_RWSIG
 	const struct vb21_packed_key *vb21_key;
 	const struct vb21_signature *vb21_sig;
 #endif
 #ifdef CONFIG_ROLLBACK
 	int32_t rw_rollback_version;
 	int32_t min_rollback_version;
 #endif

 	/* Check if we have a RW firmware flashed */
 	if (*rw_rst == 0xffffffff)
 		goto out;

 	CPRINTS("Verifying RW image...");

 #ifdef CONFIG_ROLLBACK
 	rw_rollback_version = system_get_rollback_version(SYSTEM_IMAGE_RW);
 	min_rollback_version = rollback_get_minimum_version();

 	if (rw_rollback_version < 0 || min_rollback_version < 0 ||
 	    rw_rollback_version < min_rollback_version) {
 		CPRINTS("Rollback error (%d < %d)",
 			rw_rollback_version, min_rollback_version);
 		goto out;
 	}
 #endif

 	/* Large buffer for RSA computation : could be re-use afterwards... */
 	res = shared_mem_acquire(3 * RSANUMBYTES, (char **)&rsa_workbuf);
 	if (res) {
 		CPRINTS("No memory for RW verification");
 		goto out;
 	}

 #ifdef CONFIG_RWSIG_TYPE_USBPD1
 	key = (const struct rsa_public_key *)CONFIG_RO_PUBKEY_ADDR;
 	sig = (const uint8_t *)CONFIG_RW_SIG_ADDR;
 	rwlen = CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE;
 #elif defined(CONFIG_RWSIG_TYPE_RWSIG)
 	vb21_key = (const struct vb21_packed_key *)CONFIG_RO_PUBKEY_ADDR;
 	vb21_sig = (const struct vb21_signature *)CONFIG_RW_SIG_ADDR;

 	if (vb21_key->c.magic != VB21_MAGIC_PACKED_KEY ||
 	    vb21_key->key_size != sizeof(struct rsa_public_key)) {
 		CPRINTS("Invalid key.");
 		goto out;
 	}

 	key = (const struct rsa_public_key *)
 		((const uint8_t *)vb21_key + vb21_key->key_offset);

 	/*
 	 * TODO(crbug.com/690773): We could verify other parameters such
 	 * as sig_alg/hash_alg actually matches what we build for.
 	 */
 	if (vb21_sig->c.magic != VB21_MAGIC_SIGNATURE ||
 	    vb21_sig->sig_size != RSANUMBYTES ||
 	    vb21_key->sig_alg != vb21_sig->sig_alg ||
 	    vb21_key->hash_alg != vb21_sig->hash_alg ||
 	    /* Sanity check signature offset and data size. */
 	    vb21_sig->sig_offset < sizeof(vb21_sig) ||
 	    (vb21_sig->sig_offset + RSANUMBYTES) > CONFIG_RW_SIG_SIZE ||
 	    vb21_sig->data_size > (CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE)) {
 		CPRINTS("Invalid signature.");
 		goto out;
 	}

 	sig = (const uint8_t *)vb21_sig + vb21_sig->sig_offset;
 	rwlen = vb21_sig->data_size;
 #endif

 	/*
 	 * Check that unverified RW region is actually filled with ones.
 	 */
 	good = check_padding(rwdata, rwlen,
 			CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE);
 	if (!good) {
 		CPRINTS("Invalid padding.");
 		goto out;
 	}

 	/* SHA-256 Hash of the RW firmware */
 	SHA256_init(&ctx);
 	SHA256_update(&ctx, rwdata, rwlen);
 	hash = SHA256_final(&ctx);

 	good = rsa_verify(key, sig, hash, rsa_workbuf);
 	if (!good)
 		goto out;

 #ifdef CONFIG_ROLLBACK
 	/*
 	 * Signature verified: we know that rw_rollback_version is valid, check
 	 * if rollback information should be updated.
 	 */
 	if (rw_rollback_version != min_rollback_version) {
 		/*
 		 * This will fail if the rollback block is protected (RW image
 		 * will unprotect that block later on).
 		 */
 		int ret = rollback_update(rw_rollback_version);

 		if (ret == 0) {
 			CPRINTS("Rollback updated to %d",
 				rw_rollback_version);
 		} else if (ret != EC_ERROR_ACCESS_DENIED) {
 			CPRINTS("Rollback update error %d", ret);
 			good = 0;
 		}
 	}

 	/*
 	 * Lock the ROLLBACK region, this will cause the board to reboot if the
 	 * region is not already protected.
 	 */
 	rollback_lock();
 #endif
 out:
 	CPRINTS("RW verify %s", good ? "OK" : "FAILED");

 	if (!good) {
 		pd_log_event(PD_EVENT_ACC_RW_FAIL, 0, 0, NULL);
 		/* RW firmware is invalid : do not jump there */
 		if (system_is_locked())
 			system_disable_jump();
 	}
 	if (rsa_workbuf)
 		shared_mem_release(rsa_workbuf);

 	return good;
 }

 #ifdef HAS_TASK_RWSIG
 #define TASK_EVENT_ABORT TASK_EVENT_CUSTOM(1)
 #define TASK_EVENT_CONTINUE TASK_EVENT_CUSTOM(2)

 static enum rwsig_status rwsig_status;

 enum rwsig_status rwsig_get_status(void)
 {
 	return rwsig_status;
 }

 void rwsig_abort(void)
 {
 	task_set_event(TASK_ID_RWSIG, TASK_EVENT_ABORT, 0);
 }

 void rwsig_continue(void)
 {
 	task_set_event(TASK_ID_RWSIG, TASK_EVENT_CONTINUE, 0);
 }

 void rwsig_task(void)
 {
 	uint32_t evt;

 	if (system_get_image_copy() != SYSTEM_IMAGE_RO)
 		goto exit;

 	rwsig_status = RWSIG_IN_PROGRESS;
 	if (!rwsig_check_signature()) {
 		rwsig_status = RWSIG_INVALID;
 		goto exit;
 	}
 	rwsig_status = RWSIG_VALID;

 	/* Jump to RW after a timeout */
 	evt = task_wait_event(CONFIG_RWSIG_JUMP_TIMEOUT);

 	/* Jump now if we timed out, or were told to continue. */
 	if (evt == TASK_EVENT_TIMER || evt == TASK_EVENT_CONTINUE)
 		rwsig_jump_now();
 	else
 		rwsig_status = RWSIG_ABORTED;

 exit:
 	/* We're done, yield forever. */
 	while (1)
 		task_wait_event(-1);
 }
 #endif
	/* 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.
	*/

	/*
	* Implementation of the RW firmware signature verification and jump.
	*/

	#include "console.h"
	#include "ec_commands.h"
	#include "flash.h"
	#include "rollback.h"
	#include "rsa.h"
	#include "rwsig.h"
	#include "sha256.h"
	#include "shared_mem.h"
	#include "system.h"
	#include "task.h"
	#include "usb_pd.h"
	#include "util.h"
	#include "vb21_struct.h"
	#include "version.h"

	/* Console output macros */
	#define CPRINTF(format, args...) cprintf(CC_SYSTEM, format, ## args)
	#define CPRINTS(format, args...) cprints(CC_SYSTEM, format, ## args)

	/* RW firmware reset vector */
	static uint32_t * const rw_rst =
	(uint32_t *)(CONFIG_PROGRAM_MEMORY_BASE + CONFIG_RW_MEM_OFF + 4);


	void rwsig_jump_now(void)
	{
	/* Protect all flash before jumping to RW. */

	/*
	* This may do nothing if WP is not enabled, RO is not
	* protected, or if ALL_AT_BOOT is already set.
	*/
	flash_set_protect(EC_FLASH_PROTECT_ALL_AT_BOOT, -1);

	if (!(flash_get_protect() & EC_FLASH_PROTECT_ALL_NOW) &&
	flash_get_protect() & EC_FLASH_PROTECT_ALL_AT_BOOT) {
	/*
	* If flash protection is still not enabled (some chips may
	* be able to enable it immediately), reboot.
	*/
	cflush();
	system_reset(SYSTEM_RESET_HARD \| SYSTEM_RESET_PRESERVE_FLAGS);
	}

	/* When system is locked, only boot to RW is all flash is protected. */
	if (!system_is_locked() \|\|
	flash_get_protect() & EC_FLASH_PROTECT_ALL_NOW)
	system_run_image_copy(SYSTEM_IMAGE_RW);
	}

	/*
	* Check that memory between rwdata[start] and rwdata[len-1] is filled
	* with ones. data, start and len must be aligned on 4-byte boundary.
	*/
	static int check_padding(const uint8_t *data,
	unsigned int start, unsigned int len)
	{
	unsigned int i;
	const uint32_t data32 = (const uint32_t )data;

	if ((start % 4) != 0 \|\| (len % 4) != 0)
	return 0;

	for (i = start/4; i < len/4; i++) {
	if (data32[i] != 0xffffffff)
	return 0;
	}

	return 1;
	}

	int rwsig_check_signature(void)
	{
	struct sha256_ctx ctx;
	int res;
	const struct rsa_public_key *key;
	const uint8_t *sig;
	uint8_t *hash;
	uint32_t *rsa_workbuf = NULL;
	const uint8_t rwdata = (uint8_t )CONFIG_PROGRAM_MEMORY_BASE
	+ CONFIG_RW_MEM_OFF;
	int good = 0;

	unsigned int rwlen;
	#ifdef CONFIG_RWSIG_TYPE_RWSIG
	const struct vb21_packed_key *vb21_key;
	const struct vb21_signature *vb21_sig;
	#endif
	#ifdef CONFIG_ROLLBACK
	int32_t rw_rollback_version;
	int32_t min_rollback_version;
	#endif

	/* Check if we have a RW firmware flashed */
	if (*rw_rst == 0xffffffff)
	goto out;

	CPRINTS("Verifying RW image...");

	#ifdef CONFIG_ROLLBACK
	rw_rollback_version = system_get_rollback_version(SYSTEM_IMAGE_RW);
	min_rollback_version = rollback_get_minimum_version();

	if (rw_rollback_version < 0 \|\| min_rollback_version < 0 \|\|
	rw_rollback_version < min_rollback_version) {
	CPRINTS("Rollback error (%d < %d)",
	rw_rollback_version, min_rollback_version);
	goto out;
	}
	#endif

	/* Large buffer for RSA computation : could be re-use afterwards... */
	res = shared_mem_acquire(3 * RSANUMBYTES, (char **)&rsa_workbuf);
	if (res) {
	CPRINTS("No memory for RW verification");
	goto out;
	}

	#ifdef CONFIG_RWSIG_TYPE_USBPD1
	key = (const struct rsa_public_key *)CONFIG_RO_PUBKEY_ADDR;
	sig = (const uint8_t *)CONFIG_RW_SIG_ADDR;
	rwlen = CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE;
	#elif defined(CONFIG_RWSIG_TYPE_RWSIG)
	vb21_key = (const struct vb21_packed_key *)CONFIG_RO_PUBKEY_ADDR;
	vb21_sig = (const struct vb21_signature *)CONFIG_RW_SIG_ADDR;

	if (vb21_key->c.magic != VB21_MAGIC_PACKED_KEY \|\|
	vb21_key->key_size != sizeof(struct rsa_public_key)) {
	CPRINTS("Invalid key.");
	goto out;
	}

	key = (const struct rsa_public_key *)
	((const uint8_t *)vb21_key + vb21_key->key_offset);

	/*
	* TODO(crbug.com/690773): We could verify other parameters such
	* as sig_alg/hash_alg actually matches what we build for.
	*/
	if (vb21_sig->c.magic != VB21_MAGIC_SIGNATURE \|\|
	vb21_sig->sig_size != RSANUMBYTES \|\|
	vb21_key->sig_alg != vb21_sig->sig_alg \|\|
	vb21_key->hash_alg != vb21_sig->hash_alg \|\|
	/* Sanity check signature offset and data size. */
	vb21_sig->sig_offset < sizeof(vb21_sig) \|\|
	(vb21_sig->sig_offset + RSANUMBYTES) > CONFIG_RW_SIG_SIZE \|\|
	vb21_sig->data_size > (CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE)) {
	CPRINTS("Invalid signature.");
	goto out;
	}

	sig = (const uint8_t *)vb21_sig + vb21_sig->sig_offset;
	rwlen = vb21_sig->data_size;
	#endif

	/*
	* Check that unverified RW region is actually filled with ones.
	*/
	good = check_padding(rwdata, rwlen,
	CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE);
	if (!good) {
	CPRINTS("Invalid padding.");
	goto out;
	}

	/* SHA-256 Hash of the RW firmware */
	SHA256_init(&ctx);
	SHA256_update(&ctx, rwdata, rwlen);
	hash = SHA256_final(&ctx);

	good = rsa_verify(key, sig, hash, rsa_workbuf);
	if (!good)
	goto out;

	#ifdef CONFIG_ROLLBACK
	/*
	* Signature verified: we know that rw_rollback_version is valid, check
	* if rollback information should be updated.
	*/
	if (rw_rollback_version != min_rollback_version) {
	/*
	* This will fail if the rollback block is protected (RW image
	* will unprotect that block later on).
	*/
	int ret = rollback_update(rw_rollback_version);

	if (ret == 0) {
	CPRINTS("Rollback updated to %d",
	rw_rollback_version);
	} else if (ret != EC_ERROR_ACCESS_DENIED) {
	CPRINTS("Rollback update error %d", ret);
	good = 0;
	}
	}

	/*
	* Lock the ROLLBACK region, this will cause the board to reboot if the
	* region is not already protected.
	*/
	rollback_lock();
	#endif
	out:
	CPRINTS("RW verify %s", good ? "OK" : "FAILED");

	if (!good) {
	pd_log_event(PD_EVENT_ACC_RW_FAIL, 0, 0, NULL);
	/* RW firmware is invalid : do not jump there */
	if (system_is_locked())
	system_disable_jump();
	}
	if (rsa_workbuf)
	shared_mem_release(rsa_workbuf);

	return good;
	}

	#ifdef HAS_TASK_RWSIG
	#define TASK_EVENT_ABORT TASK_EVENT_CUSTOM(1)
	#define TASK_EVENT_CONTINUE TASK_EVENT_CUSTOM(2)

	static enum rwsig_status rwsig_status;

	enum rwsig_status rwsig_get_status(void)
	{
	return rwsig_status;
	}

	void rwsig_abort(void)
	{
	task_set_event(TASK_ID_RWSIG, TASK_EVENT_ABORT, 0);
	}

	void rwsig_continue(void)
	{
	task_set_event(TASK_ID_RWSIG, TASK_EVENT_CONTINUE, 0);
	}

	void rwsig_task(void)
	{
	uint32_t evt;

	if (system_get_image_copy() != SYSTEM_IMAGE_RO)
	goto exit;

	rwsig_status = RWSIG_IN_PROGRESS;
	if (!rwsig_check_signature()) {
	rwsig_status = RWSIG_INVALID;
	goto exit;
	}
	rwsig_status = RWSIG_VALID;

	/* Jump to RW after a timeout */
	evt = task_wait_event(CONFIG_RWSIG_JUMP_TIMEOUT);

	/* Jump now if we timed out, or were told to continue. */
	if (evt == TASK_EVENT_TIMER \|\| evt == TASK_EVENT_CONTINUE)
	rwsig_jump_now();
	else
	rwsig_status = RWSIG_ABORTED;

	exit:
	/* We're done, yield forever. */
	while (1)
	task_wait_event(-1);
	}
	#endif