/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005-2011 Pawel Jakub Dawidek <pawel@dawidek.net>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#ifdef _KERNEL
#include <sys/malloc.h>
#include <sys/systm.h>
#include <geom/geom.h>
#else
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#endif

#include <geom/eli/g_eli.h>

#ifdef _KERNEL
MALLOC_DECLARE(M_ELI);
#endif

/*
 * Verify if the given 'key' is correct.
 * Return 1 if it is correct and 0 otherwise.
 */
static int
g_eli_mkey_verify(const unsigned char *mkey, const unsigned char *key)
{
        const unsigned char *odhmac;    /* On-disk HMAC. */
        unsigned char chmac[SHA512_MDLEN];      /* Calculated HMAC. */
        unsigned char hmkey[SHA512_MDLEN];      /* Key for HMAC. */

        /*
         * The key for HMAC calculations is: hmkey = HMAC_SHA512(Derived-Key, 0)
         */
        g_eli_crypto_hmac(key, G_ELI_USERKEYLEN, "\x00", 1, hmkey, 0);

        odhmac = mkey + G_ELI_DATAIVKEYLEN;

        /* Calculate HMAC from Data-Key and IV-Key. */
        g_eli_crypto_hmac(hmkey, sizeof(hmkey), mkey, G_ELI_DATAIVKEYLEN,
            chmac, 0);

        explicit_bzero(hmkey, sizeof(hmkey));

        /*
         * Compare calculated HMAC with HMAC from metadata.
         * If two HMACs are equal, 'key' is correct.
         */
        return (!bcmp(odhmac, chmac, SHA512_MDLEN));
}

/*
 * Calculate HMAC from Data-Key and IV-Key.
 */
void
g_eli_mkey_hmac(unsigned char *mkey, const unsigned char *key)
{
        unsigned char hmkey[SHA512_MDLEN];      /* Key for HMAC. */
        unsigned char *odhmac;  /* On-disk HMAC. */

        /*
         * The key for HMAC calculations is: hmkey = HMAC_SHA512(Derived-Key, 0)
         */
        g_eli_crypto_hmac(key, G_ELI_USERKEYLEN, "\x00", 1, hmkey, 0);

        odhmac = mkey + G_ELI_DATAIVKEYLEN;
        /* Calculate HMAC from Data-Key and IV-Key. */
        g_eli_crypto_hmac(hmkey, sizeof(hmkey), mkey, G_ELI_DATAIVKEYLEN,
            odhmac, 0);

        explicit_bzero(hmkey, sizeof(hmkey));
}

/*
 * Find and decrypt Master Key encrypted with 'key' at slot 'nkey'.
 * Return 0 on success, > 0 on failure, -1 on bad key.
 */
int
g_eli_mkey_decrypt(const struct g_eli_metadata *md, const unsigned char *key,
    unsigned char *mkey, unsigned nkey)
{
        unsigned char tmpmkey[G_ELI_MKEYLEN];
        unsigned char enckey[SHA512_MDLEN];     /* Key for encryption. */
        const unsigned char *mmkey;
        int bit, error;

        if (nkey > G_ELI_MKEYLEN)
                return (-1);

        /*
         * The key for encryption is: enckey = HMAC_SHA512(Derived-Key, 1)
         */
        g_eli_crypto_hmac(key, G_ELI_USERKEYLEN, "\x01", 1, enckey, 0);

        mmkey = md->md_mkeys + G_ELI_MKEYLEN * nkey;
        bit = (1 << nkey);
        if (!(md->md_keys & bit))
                return (-1);
        bcopy(mmkey, tmpmkey, G_ELI_MKEYLEN);
        error = g_eli_crypto_decrypt(md->md_ealgo, tmpmkey,
            G_ELI_MKEYLEN, enckey, md->md_keylen);
        if (error != 0) {
                explicit_bzero(tmpmkey, sizeof(tmpmkey));
                explicit_bzero(enckey, sizeof(enckey));
                return (error);
        }
        if (g_eli_mkey_verify(tmpmkey, key)) {
                bcopy(tmpmkey, mkey, G_ELI_DATAIVKEYLEN);
                explicit_bzero(tmpmkey, sizeof(tmpmkey));
                explicit_bzero(enckey, sizeof(enckey));
                return (0);
        }
        explicit_bzero(enckey, sizeof(enckey));
        explicit_bzero(tmpmkey, sizeof(tmpmkey));

        return (-1);
}

/*
 * Find and decrypt Master Key encrypted with 'key'.
 * Return decrypted Master Key number in 'nkeyp' if not NULL.
 * Return 0 on success, > 0 on failure, -1 on bad key.
 */
int
g_eli_mkey_decrypt_any(const struct g_eli_metadata *md,
    const unsigned char *key, unsigned char *mkey, unsigned *nkeyp)
{
        int error, nkey;

        if (nkeyp != NULL)
                *nkeyp = -1;

        error = -1;
        for (nkey = 0; nkey < G_ELI_MAXMKEYS; nkey++) {
                error = g_eli_mkey_decrypt(md, key, mkey, nkey);
                if (error == 0) {
                        if (nkeyp != NULL)
                                *nkeyp = nkey;
                        break;
                } else if (error > 0) {
                        break;
                }
        }

        return (error);
}

/*
 * Encrypt the Master-Key and calculate HMAC to be able to verify it in the
 * future.
 */
int
g_eli_mkey_encrypt(unsigned algo, const unsigned char *key, unsigned keylen,
    unsigned char *mkey)
{
        unsigned char enckey[SHA512_MDLEN];     /* Key for encryption. */
        int error;

        /*
         * To calculate HMAC, the whole key (G_ELI_USERKEYLEN bytes long) will
         * be used.
         */
        g_eli_mkey_hmac(mkey, key);
        /*
         * The key for encryption is: enckey = HMAC_SHA512(Derived-Key, 1)
         */
        g_eli_crypto_hmac(key, G_ELI_USERKEYLEN, "\x01", 1, enckey, 0);
        /*
         * Encrypt the Master-Key and HMAC() result with the given key (this
         * time only 'keylen' bits from the key are used).
         */
        error = g_eli_crypto_encrypt(algo, mkey, G_ELI_MKEYLEN, enckey, keylen);

        explicit_bzero(enckey, sizeof(enckey));

        return (error);
}

#ifdef _KERNEL
/*
 * When doing encryption only, copy IV key and encryption key.
 * When doing encryption and authentication, copy IV key, generate encryption
 * key and generate authentication key.
 */
void
g_eli_mkey_propagate(struct g_eli_softc *sc, const unsigned char *mkey)
{

        /* Remember the Master Key. */
        bcopy(mkey, sc->sc_mkey, sizeof(sc->sc_mkey));

        bcopy(mkey, sc->sc_ivkey, sizeof(sc->sc_ivkey));
        mkey += sizeof(sc->sc_ivkey);

        /*
         * The authentication key is: akey = HMAC_SHA512(Data-Key, 0x11)
         */
        if ((sc->sc_flags & G_ELI_FLAG_AUTH) != 0) {
                g_eli_crypto_hmac(mkey, G_ELI_MAXKEYLEN, "\x11", 1,
                    sc->sc_akey, 0);
        } else {
                arc4rand(sc->sc_akey, sizeof(sc->sc_akey), 0);
        }

        /* Initialize encryption keys. */
        g_eli_key_init(sc);

        if ((sc->sc_flags & G_ELI_FLAG_AUTH) != 0) {
                /*
                 * Precalculate SHA256 for HMAC key generation.
                 * This is expensive operation and we can do it only once now or
                 * for every access to sector, so now will be much better.
                 */
                SHA256_Init(&sc->sc_akeyctx);
                SHA256_Update(&sc->sc_akeyctx, sc->sc_akey,
                    sizeof(sc->sc_akey));
        }
        /*
         * Precalculate SHA256 for IV generation.
         * This is expensive operation and we can do it only once now or for
         * every access to sector, so now will be much better.
         */
        switch (sc->sc_ealgo) {
        case CRYPTO_AES_XTS:
                break;
        default:
                SHA256_Init(&sc->sc_ivctx);
                SHA256_Update(&sc->sc_ivctx, sc->sc_ivkey,
                    sizeof(sc->sc_ivkey));
                break;
        }
}
#endif