vboot/bdb/bdb.h

/* Copyright (c) 2015 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.
 *
 * Boot descriptor block firmware functions
 */

#ifndef VBOOT_REFERENCE_BDB_H_
#define VBOOT_REFERENCE_BDB_H_

#include <stdlib.h>
#include "bdb_struct.h"

/*****************************************************************************/
/*
Expected calling sequence:

Load and check just the header
bdb_check_header(buf, size);

Load and verify the entire BDB
bdb_verify(buf, size, bdb_key_hash, dev_mode_flag);

Check RW subkey version.  If normal boot from primary BDB, roll forward

Check data version.  If normal boot from primary BDB, roll forward
*/

/*****************************************************************************/
/* Codes for functions returning numeric error codes */

enum bdb_return_code {
	/* Success */
	BDB_SUCCESS = 0,

	/* BDB key did not match hash, but other than that the BDB was
	 * fully verified. */
	BDB_GOOD_OTHER_THAN_KEY = 1,

	/* Other errors */
	BDB_ERROR_UNKNOWN = 100,

	/* Buffer size too small or wraps around */
	BDB_ERROR_BUF_SIZE,

	/* Bad fields in structures */
	BDB_ERROR_STRUCT_MAGIC,
	BDB_ERROR_STRUCT_VERSION,
	BDB_ERROR_STRUCT_SIZE,
	BDB_ERROR_SIGNED_SIZE,
	BDB_ERROR_BDB_SIZE,
	BDB_ERROR_OEM_AREA_SIZE,
	BDB_ERROR_HASH_ENTRY_SIZE,
	BDB_ERROR_HASH_ALG,
	BDB_ERROR_SIG_ALG,
	BDB_ERROR_DESCRIPTION,

	/* Bad components of BDB in bdb_verify() */
	BDB_ERROR_HEADER,
	BDB_ERROR_BDBKEY,
	BDB_ERROR_OEM_AREA_0,
	BDB_ERROR_SUBKEY,
	BDB_ERROR_BDB_SIGNED_SIZE,
	BDB_ERROR_HEADER_SIG,
	BDB_ERROR_DATA,
	BDB_ERROR_DATA_SIG,

	/* Other errors in bdb_verify() */
	BDB_ERROR_DIGEST,	/* Error calculating digest */
	BDB_ERROR_VERIFY_SIG,	/* Error verifying signature */
};

/*****************************************************************************/
/* Functions */

/**
 * Sanity-check BDB structures.
 *
 * This checks for known version numbers, magic numbers, algorithms, etc. and
 * ensures the sizes are consistent with those parameters.
 *
 * @param p		Pointer to structure to check
 * @param size		Size of structure buffer
 * @return 0 if success, non-zero error code if error.
 */
int bdb_check_header(const struct bdb_header *p, size_t size);
int bdb_check_key(const struct bdb_key *p, size_t size);
int bdb_check_sig(const struct bdb_sig *p, size_t size);
int bdb_check_data(const struct bdb_data *p, size_t size);

/**
 * Verify the entire BDB
 *
 * @param buf			Data to hash
 * @param size			Size of data in bytes
 * @param bdb_key_digest	Pointer to expected digest for BDB key.
 *				Must be BDB_SHA256_DIGEST_SIZE bytes long.
 *
 * @return 0 if success, non-zero error code if error.  Note that error code
 * BDB_GOOD_OTHER_THAN_KEY may still indicate an acceptable BDB if the Boot
 * Verified fuse has not been set, or in developer mode.
 */
int bdb_verify(const void *buf, size_t size, const uint8_t *bdb_key_digest);

/**
 * Functions to extract things from a verified BDB buffer.
 *
 * Do not call these externally until after bdb_verify()!  These methods
 * assume data structures have already been verified.
 *
 * @param buf		Pointer to BDB buffer
 * @param type		Data type, for bdb_get_hash()
 * @return A pointer to the requested data, or NULL if error / not present.
 */
const struct bdb_header *bdb_get_header(const void *buf);
const struct bdb_key *bdb_get_bdbkey(const void *buf);
const void *bdb_get_oem_area_0(const void *buf);
const struct bdb_key *bdb_get_subkey(const void *buf);
const struct bdb_sig *bdb_get_header_sig(const void *buf);
const struct bdb_data *bdb_get_data(const void *buf);
const void *bdb_get_oem_area_1(const void *buf);
const struct bdb_hash *bdb_get_hash(const void *buf, enum bdb_data_type type);
const struct bdb_sig *bdb_get_data_sig(const void *buf);

/*****************************************************************************/
/* Functions probably provided by the caller */

/**
 * Calculate a SHA-256 digest of a buffer.
 *
 * @param digest	Pointer to the digest buffer.  Must be
 *			BDB_SHA256_DIGEST_SIZE bytes long.
 * @param buf		Data to hash
 * @param size		Size of data in bytes
 * @return 0 if success, non-zero error code if error.
 */
__attribute__((weak))
int bdb_sha256(void *digest, const void *buf, size_t size);

/**
 * Verify a RSA-4096 signed digest
 *
 * @param key_data	Key data to use (BDB_RSA4096_KEY_DATA_SIZE bytes)
 * @param sig_data	Signature to verify (BDB_RSA4096_SIG_SIZE bytes)
 * @param digest	Digest of signed data (BDB_SHA256_DIGEST bytes)
 * @return 0 if success, non-zero error code if error.
 */
__attribute__((weak))
int bdb_rsa4096_verify(const uint8_t *key_data,
		       const uint8_t *sig,
		       const uint8_t *digest);

/**
 * Verify a RSA-3072B signed digest
 *
 * @param key_data	Key data to use (BDB_RSA3072B_KEY_DATA_SIZE bytes)
 * @param sig_data	Signature to verify (BDB_RSA3072B_SIG_SIZE bytes)
 * @param digest	Digest of signed data (BDB_SHA256_DIGEST bytes)
 * @return 0 if success, non-zero error code if error.
 */
__attribute__((weak))
int bdb_rsa3072b_verify(const uint8_t *key_data,
			const uint8_t *sig,
			const uint8_t *digest);

/**
 * Verify a ECDSA-521 signed digest
 *
 * @param key_data	Key data to use (BDB_ECDSA521_KEY_DATA_SIZE bytes)
 * @param sig_data	Signature to verify (BDB_ECDSA521_SIG_SIZE bytes)
 * @param digest	Digest of signed data (BDB_SHA256_DIGEST bytes)
 * @return 0 if success, non-zero error code if error.
 */
__attribute__((weak))
int bdb_ecdsa521_verify(const uint8_t *key_data,
			const uint8_t *sig,
			const uint8_t *digest);

/*****************************************************************************/

#endif /* VBOOT_REFERENCE_BDB_H_ */