fs/zfs/zio_checksum.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2013, 2016 by Delphix. All rights reserved.
 * Copyright (c) 2013, Joyent, Inc. All rights reserved.
 * Copyright 2013 Saso Kiselkov. All rights reserved.
 */

#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/zio.h>
#include <sys/zio_checksum.h>
#include <sys/zil.h>
#include <zfs_fletcher.h>

/*
 * Checksum vectors.
 *
 * In the SPA, everything is checksummed.  We support checksum vectors
 * for three distinct reasons:
 *
 *   1. Different kinds of data need different levels of protection.
 *  For SPA metadata, we always want a very strong checksum.
 *  For user data, we let users make the trade-off between speed
 *  and checksum strength.
 *
 *   2. Cryptographic hash and MAC algorithms are an area of active research.
 *  It is likely that in future hash functions will be at least as strong
 *  as current best-of-breed, and may be substantially faster as well.
 *  We want the ability to take advantage of these new hashes as soon as
 *  they become available.
 *
 *   3. If someone develops hardware that can compute a strong hash quickly,
 *  we want the ability to take advantage of that hardware.
 *
 * Of course, we don't want a checksum upgrade to invalidate existing
 * data, so we store the checksum *function* in eight bits of the bp.
 * This gives us room for up to 256 different checksum functions.
 *
 * When writing a block, we always checksum it with the latest-and-greatest
 * checksum function of the appropriate strength.  When reading a block,
 * we compare the expected checksum against the actual checksum, which we
 * compute via the checksum function specified by BP_GET_CHECKSUM(bp).
 *
 * SALTED CHECKSUMS
 *
 * To enable the use of less secure hash algorithms with dedup, we
 * introduce the notion of salted checksums (MACs, really).  A salted
 * checksum is fed both a random 256-bit value (the salt) and the data
 * to be checksummed.  This salt is kept secret (stored on the pool, but
 * never shown to the user).  Thus even if an attacker knew of collision
 * weaknesses in the hash algorithm, they won't be able to mount a known
 * plaintext attack on the DDT, since the actual hash value cannot be
 * known ahead of time.  How the salt is used is algorithm-specific
 * (some might simply prefix it to the data block, others might need to
 * utilize a full-blown HMAC).  On disk the salt is stored in a ZAP
 * object in the MOS (DMU_POOL_CHECKSUM_SALT).
 *
 * CONTEXT TEMPLATES
 *
 * Some hashing algorithms need to perform a substantial amount of
 * initialization work (e.g. salted checksums above may need to pre-hash
 * the salt) before being able to process data.  Performing this
 * redundant work for each block would be wasteful, so we instead allow
 * a checksum algorithm to do the work once (the first time it's used)
 * and then keep this pre-initialized context as a template inside the
 * spa_t (spa_cksum_tmpls).  If the zio_checksum_info_t contains
 * non-NULL ci_tmpl_init and ci_tmpl_free callbacks, they are used to
 * construct and destruct the pre-initialized checksum context.  The
 * pre-initialized context is then reused during each checksum
 * invocation and passed to the checksum function.
 */

/*ARGSUSED*/
static void
zio_checksum_off(const void *buf, uint64_t size,
    const void *ctx_template, zio_cksum_t *zcp)
{
    ZIO_SET_CHECKSUM(zcp, 0, 0, 0, 0);
}

zio_checksum_info_t zio_checksum_table[ZIO_CHECKSUM_FUNCTIONS] = {
    {{NULL, NULL}, NULL, NULL, 0, "inherit"},
    {{NULL, NULL}, NULL, NULL, 0, "on"},
    {{zio_checksum_off,     zio_checksum_off},
        NULL, NULL, 0, "off"},
    {{zio_checksum_SHA256,      zio_checksum_SHA256},
        NULL, NULL, ZCHECKSUM_FLAG_METADATA | ZCHECKSUM_FLAG_EMBEDDED,
        "label"},
    {{zio_checksum_SHA256,      zio_checksum_SHA256},
        NULL, NULL, ZCHECKSUM_FLAG_METADATA | ZCHECKSUM_FLAG_EMBEDDED,
        "gang_header"},
    {{fletcher_2_native,        fletcher_2_byteswap},
        NULL, NULL, ZCHECKSUM_FLAG_EMBEDDED, "zilog"},
    {{fletcher_2_native,        fletcher_2_byteswap},
        NULL, NULL, 0, "fletcher2"},
    {{fletcher_4_native,        fletcher_4_byteswap},
        NULL, NULL, ZCHECKSUM_FLAG_METADATA, "fletcher4"},
    {{zio_checksum_SHA256,      zio_checksum_SHA256},
        NULL, NULL, ZCHECKSUM_FLAG_METADATA | ZCHECKSUM_FLAG_DEDUP |
        ZCHECKSUM_FLAG_NOPWRITE, "sha256"},
    {{fletcher_4_native,        fletcher_4_byteswap},
        NULL, NULL, ZCHECKSUM_FLAG_EMBEDDED, "zilog2"},
    {{zio_checksum_off,     zio_checksum_off},
        NULL, NULL, 0, "noparity"},
    {{zio_checksum_SHA512_native,   zio_checksum_SHA512_byteswap},
        NULL, NULL, ZCHECKSUM_FLAG_METADATA | ZCHECKSUM_FLAG_DEDUP |
        ZCHECKSUM_FLAG_NOPWRITE, "sha512"},
    {{zio_checksum_skein_native,    zio_checksum_skein_byteswap},
        zio_checksum_skein_tmpl_init, zio_checksum_skein_tmpl_free,
        ZCHECKSUM_FLAG_METADATA | ZCHECKSUM_FLAG_DEDUP |
        ZCHECKSUM_FLAG_SALTED | ZCHECKSUM_FLAG_NOPWRITE, "skein"},
    {{zio_checksum_edonr_native,    zio_checksum_edonr_byteswap},
        zio_checksum_edonr_tmpl_init, zio_checksum_edonr_tmpl_free,
        ZCHECKSUM_FLAG_METADATA | ZCHECKSUM_FLAG_SALTED |
        ZCHECKSUM_FLAG_NOPWRITE, "edonr"},
};

/*
 * The flag corresponding to the "verify" in dedup=[checksum,]verify
 * must be cleared first, so callers should use ZIO_CHECKSUM_MASK.
 */
spa_feature_t
zio_checksum_to_feature(enum zio_checksum cksum)
{
    VERIFY((cksum & ~ZIO_CHECKSUM_MASK) == 0);

    switch (cksum) {
    case ZIO_CHECKSUM_SHA512:
        return (SPA_FEATURE_SHA512);
    case ZIO_CHECKSUM_SKEIN:
        return (SPA_FEATURE_SKEIN);
    case ZIO_CHECKSUM_EDONR:
        return (SPA_FEATURE_EDONR);
    }
    return (SPA_FEATURE_NONE);
}

enum zio_checksum
zio_checksum_select(enum zio_checksum child, enum zio_checksum parent)
{
    ASSERT(child < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(parent < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(parent != ZIO_CHECKSUM_INHERIT && parent != ZIO_CHECKSUM_ON);

    if (child == ZIO_CHECKSUM_INHERIT)
        return (parent);

    if (child == ZIO_CHECKSUM_ON)
        return (ZIO_CHECKSUM_ON_VALUE);

    return (child);
}

enum zio_checksum
zio_checksum_dedup_select(spa_t *spa, enum zio_checksum child,
    enum zio_checksum parent)
{
    ASSERT((child & ZIO_CHECKSUM_MASK) < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT((parent & ZIO_CHECKSUM_MASK) < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(parent != ZIO_CHECKSUM_INHERIT && parent != ZIO_CHECKSUM_ON);

    if (child == ZIO_CHECKSUM_INHERIT)
        return (parent);

    if (child == ZIO_CHECKSUM_ON)
        return (spa_dedup_checksum(spa));

    if (child == (ZIO_CHECKSUM_ON | ZIO_CHECKSUM_VERIFY))
        return (spa_dedup_checksum(spa) | ZIO_CHECKSUM_VERIFY);

    ASSERT((zio_checksum_table[child & ZIO_CHECKSUM_MASK].ci_flags &
        ZCHECKSUM_FLAG_DEDUP) ||
        (child & ZIO_CHECKSUM_VERIFY) || child == ZIO_CHECKSUM_OFF);

    return (child);
}

/*
 * Set the external verifier for a gang block based on <vdev, offset, txg>,
 * a tuple which is guaranteed to be unique for the life of the pool.
 */
static void
zio_checksum_gang_verifier(zio_cksum_t *zcp, blkptr_t *bp)
{
    dva_t *dva = BP_IDENTITY(bp);
    uint64_t txg = BP_PHYSICAL_BIRTH(bp);

    ASSERT(BP_IS_GANG(bp));

    ZIO_SET_CHECKSUM(zcp, DVA_GET_VDEV(dva), DVA_GET_OFFSET(dva), txg, 0);
}

/*
 * Set the external verifier for a label block based on its offset.
 * The vdev is implicit, and the txg is unknowable at pool open time --
 * hence the logic in vdev_uberblock_load() to find the most recent copy.
 */
static void
zio_checksum_label_verifier(zio_cksum_t *zcp, uint64_t offset)
{
    ZIO_SET_CHECKSUM(zcp, offset, 0, 0, 0);
}

/*
 * Calls the template init function of a checksum which supports context
 * templates and installs the template into the spa_t.
 */
static void
zio_checksum_template_init(enum zio_checksum checksum, spa_t *spa)
{
    zio_checksum_info_t *ci = &zio_checksum_table[checksum];

    if (ci->ci_tmpl_init == NULL)
        return;
    if (spa->spa_cksum_tmpls[checksum] != NULL)
        return;

    VERIFY(ci->ci_tmpl_free != NULL);
    mutex_enter(&spa->spa_cksum_tmpls_lock);
    if (spa->spa_cksum_tmpls[checksum] == NULL) {
        spa->spa_cksum_tmpls[checksum] =
            ci->ci_tmpl_init(&spa->spa_cksum_salt);
        VERIFY(spa->spa_cksum_tmpls[checksum] != NULL);
    }
    mutex_exit(&spa->spa_cksum_tmpls_lock);
}

/*
 * Generate the checksum.
 */
void
zio_checksum_compute(zio_t *zio, enum zio_checksum checksum,
    void *data, uint64_t size)
{
    blkptr_t *bp = zio->io_bp;
    uint64_t offset = zio->io_offset;
    zio_checksum_info_t *ci = &zio_checksum_table[checksum];
    zio_cksum_t cksum;
    spa_t *spa = zio->io_spa;

    ASSERT((uint_t)checksum < ZIO_CHECKSUM_FUNCTIONS);
    ASSERT(ci->ci_func[0] != NULL);

    zio_checksum_template_init(checksum, spa);

    if (ci->ci_flags & ZCHECKSUM_FLAG_EMBEDDED) {
        zio_eck_t *eck;

        if (checksum == ZIO_CHECKSUM_ZILOG2) {
            zil_chain_t *zilc = data;

            size = P2ROUNDUP_TYPED(zilc->zc_nused, ZIL_MIN_BLKSZ,
                uint64_t);
            eck = &zilc->zc_eck;
        } else {
            eck = (zio_eck_t *)((char *)data + size) - 1;
        }
        if (checksum == ZIO_CHECKSUM_GANG_HEADER)
            zio_checksum_gang_verifier(&eck->zec_cksum, bp);
        else if (checksum == ZIO_CHECKSUM_LABEL)
            zio_checksum_label_verifier(&eck->zec_cksum, offset);
        else
            bp->blk_cksum = eck->zec_cksum;
        eck->zec_magic = ZEC_MAGIC;
        ci->ci_func[0](data, size, spa->spa_cksum_tmpls[checksum],
            &cksum);
        eck->zec_cksum = cksum;
    } else {
        ci->ci_func[0](data, size, spa->spa_cksum_tmpls[checksum],
            &bp->blk_cksum);
    }
}

int
zio_checksum_error_impl(spa_t *spa, blkptr_t *bp, enum zio_checksum checksum,
    void *data, uint64_t size, uint64_t offset, zio_bad_cksum_t *info)
{
    zio_checksum_info_t *ci = &zio_checksum_table[checksum];
    zio_cksum_t actual_cksum, expected_cksum;
    int byteswap;

    if (checksum >= ZIO_CHECKSUM_FUNCTIONS || ci->ci_func[0] == NULL)
        return (SET_ERROR(EINVAL));

    zio_checksum_template_init(checksum, spa);

    if (ci->ci_flags & ZCHECKSUM_FLAG_EMBEDDED) {
        zio_eck_t *eck;
        zio_cksum_t verifier;

        if (checksum == ZIO_CHECKSUM_ZILOG2) {
            zil_chain_t *zilc = data;
            uint64_t nused;

            eck = &zilc->zc_eck;
            if (eck->zec_magic == ZEC_MAGIC)
                nused = zilc->zc_nused;
            else if (eck->zec_magic == BSWAP_64(ZEC_MAGIC))
                nused = BSWAP_64(zilc->zc_nused);
            else
                return (SET_ERROR(ECKSUM));

            if (nused > size)
                return (SET_ERROR(ECKSUM));

            size = P2ROUNDUP_TYPED(nused, ZIL_MIN_BLKSZ, uint64_t);
        } else {
            eck = (zio_eck_t *)((char *)data + size) - 1;
        }

        if (checksum == ZIO_CHECKSUM_GANG_HEADER)
            zio_checksum_gang_verifier(&verifier, bp);
        else if (checksum == ZIO_CHECKSUM_LABEL)
            zio_checksum_label_verifier(&verifier, offset);
        else
            verifier = bp->blk_cksum;

        byteswap = (eck->zec_magic == BSWAP_64(ZEC_MAGIC));

        if (byteswap)
            byteswap_uint64_array(&verifier, sizeof (zio_cksum_t));

        expected_cksum = eck->zec_cksum;
        eck->zec_cksum = verifier;
        ci->ci_func[byteswap](data, size,
            spa->spa_cksum_tmpls[checksum], &actual_cksum);
        eck->zec_cksum = expected_cksum;

        if (byteswap) {
            byteswap_uint64_array(&expected_cksum,
                sizeof (zio_cksum_t));
        }
    } else {
        byteswap = BP_SHOULD_BYTESWAP(bp);
        expected_cksum = bp->blk_cksum;
        ci->ci_func[byteswap](data, size,
            spa->spa_cksum_tmpls[checksum], &actual_cksum);
    }

    if (info != NULL) {
        info->zbc_expected = expected_cksum;
        info->zbc_actual = actual_cksum;
        info->zbc_checksum_name = ci->ci_name;
        info->zbc_byteswapped = byteswap;
        info->zbc_injected = 0;
        info->zbc_has_cksum = 1;
    }

    if (!ZIO_CHECKSUM_EQUAL(actual_cksum, expected_cksum))
        return (SET_ERROR(ECKSUM));

    return (0);
}

int
zio_checksum_error(zio_t *zio, zio_bad_cksum_t *info)
{
    blkptr_t *bp = zio->io_bp;
    uint_t checksum = (bp == NULL ? zio->io_prop.zp_checksum :
        (BP_IS_GANG(bp) ? ZIO_CHECKSUM_GANG_HEADER : BP_GET_CHECKSUM(bp)));
    int error;
    uint64_t size = (bp == NULL ? zio->io_size :
        (BP_IS_GANG(bp) ? SPA_GANGBLOCKSIZE : BP_GET_PSIZE(bp)));
    uint64_t offset = zio->io_offset;
    void *data = zio->io_data;
    spa_t *spa = zio->io_spa;

    error = zio_checksum_error_impl(spa, bp, checksum, data, size,
        offset, info);

    if (zio_injection_enabled && error == 0 && zio->io_error == 0) {
        error = zio_handle_fault_injection(zio, ECKSUM);
        if (error != 0)
            info->zbc_injected = 1;
    }

    return (error);
}

/*
 * Called by a spa_t that's about to be deallocated. This steps through
 * all of the checksum context templates and deallocates any that were
 * initialized using the algorithm-specific template init function.
 */
void
zio_checksum_templates_free(spa_t *spa)
{
    for (enum zio_checksum checksum = 0;
        checksum < ZIO_CHECKSUM_FUNCTIONS; checksum++) {
        if (spa->spa_cksum_tmpls[checksum] != NULL) {
            zio_checksum_info_t *ci = &zio_checksum_table[checksum];

            VERIFY(ci->ci_tmpl_free != NULL);
            ci->ci_tmpl_free(spa->spa_cksum_tmpls[checksum]);
            spa->spa_cksum_tmpls[checksum] = NULL;
        }
    }
}