FreeBSD-5.3/sys/geom/bde/g_bde_crypt.c
/*-
* Copyright (c) 2002 Poul-Henning Kamp
* Copyright (c) 2002 Networks Associates Technology, Inc.
* All rights reserved.
*
* This software was developed for the FreeBSD Project by Poul-Henning Kamp
* and NAI Labs, the Security Research Division of Network Associates, Inc.
* under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
* DARPA CHATS research program.
*
* 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 AUTHOR 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 AUTHOR 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.
*
* $FreeBSD: src/sys/geom/bde/g_bde_crypt.c,v 1.19.2.1 2004/09/14 05:59:12 phk Exp $
*
* This source file contains the functions responsible for the crypto, keying
* and mapping operations on the I/O requests.
*
*/
#include <sys/param.h>
#include <sys/bio.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/queue.h>
#include <sys/malloc.h>
#include <sys/libkern.h>
#include <sys/endian.h>
#include <sys/md5.h>
#include <crypto/rijndael/rijndael.h>
#include <crypto/sha2/sha2.h>
#include <geom/geom.h>
#include <geom/bde/g_bde.h>
/*
* XXX: Debugging DO NOT ENABLE
*/
#undef MD5_KEY
/*
* Derive kkey from mkey + sector offset.
*
* Security objective: Derive a potentially very large number of distinct skeys
* from the comparatively small key material in our mkey, in such a way that
* if one, more or even many of the kkeys are compromised, this does not
* significantly help an attack on other kkeys and in particular does not
* weaken or compromised the mkey.
*
* First we MD5 hash the sectornumber with the salt from the lock sector.
* The salt prevents the precalculation and statistical analysis of the MD5
* output which would be possible if we only gave it the sectornumber.
*
* The MD5 hash is used to pick out 16 bytes from the masterkey, which
* are then hashed with MD5 together with the sector number.
*
* The resulting MD5 hash is the kkey.
*/
static void
g_bde_kkey(struct g_bde_softc *sc, keyInstance *ki, int dir, off_t sector)
{
u_int t;
MD5_CTX ct;
u_char buf[16];
u_char buf2[8];
/* We have to be architecture neutral */
le64enc(buf2, sector);
MD5Init(&ct);
MD5Update(&ct, sc->key.salt, 8);
MD5Update(&ct, buf2, sizeof buf2);
MD5Update(&ct, sc->key.salt + 8, 8);
MD5Final(buf, &ct);
MD5Init(&ct);
for (t = 0; t < 16; t++) {
MD5Update(&ct, &sc->key.mkey[buf[t]], 1);
if (t == 8)
MD5Update(&ct, buf2, sizeof buf2);
}
bzero(buf2, sizeof buf2);
MD5Final(buf, &ct);
bzero(&ct, sizeof ct);
AES_makekey(ki, dir, G_BDE_KKEYBITS, buf);
bzero(buf, sizeof buf);
}
/*
* Encryption work for read operation.
*
* Security objective: Find the kkey, find the skey, decrypt the sector data.
*/
void
g_bde_crypt_read(struct g_bde_work *wp)
{
struct g_bde_softc *sc;
u_char *d;
u_int n;
off_t o;
u_char skey[G_BDE_SKEYLEN];
keyInstance ki;
cipherInstance ci;
AES_init(&ci);
sc = wp->softc;
o = 0;
for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
g_bde_kkey(sc, &ki, DIR_DECRYPT, wp->offset + o);
AES_decrypt(&ci, &ki, d, skey, sizeof skey);
d = (u_char *)wp->data + o;
AES_makekey(&ki, DIR_DECRYPT, G_BDE_SKEYBITS, skey);
AES_decrypt(&ci, &ki, d, d, sc->sectorsize);
}
bzero(skey, sizeof skey);
bzero(&ci, sizeof ci);
bzero(&ki, sizeof ki);
}
/*
* Encryption work for write operation.
*
* Security objective: Create random skey, encrypt sector data,
* encrypt skey with the kkey.
*/
void
g_bde_crypt_write(struct g_bde_work *wp)
{
u_char *s, *d;
struct g_bde_softc *sc;
u_int n;
off_t o;
u_char skey[G_BDE_SKEYLEN];
keyInstance ki;
cipherInstance ci;
sc = wp->softc;
AES_init(&ci);
o = 0;
for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
s = (u_char *)wp->data + o;
d = (u_char *)wp->sp->data + o;
arc4rand(skey, sizeof skey, 0);
AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
AES_encrypt(&ci, &ki, s, d, sc->sectorsize);
d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
g_bde_kkey(sc, &ki, DIR_ENCRYPT, wp->offset + o);
AES_encrypt(&ci, &ki, skey, d, sizeof skey);
bzero(skey, sizeof skey);
}
bzero(skey, sizeof skey);
bzero(&ci, sizeof ci);
bzero(&ki, sizeof ki);
}
/*
* Encryption work for delete operation.
*
* Security objective: Write random data to the sectors.
*
* XXX: At a hit in performance we would trash the encrypted skey as well.
* XXX: This would add frustration to the cleaning lady attack by making
* XXX: deletes look like writes.
*/
void
g_bde_crypt_delete(struct g_bde_work *wp)
{
struct g_bde_softc *sc;
u_char *d;
off_t o;
u_char skey[G_BDE_SKEYLEN];
keyInstance ki;
cipherInstance ci;
sc = wp->softc;
d = wp->sp->data;
AES_init(&ci);
/*
* Do not unroll this loop!
* Our zone may be significantly wider than the amount of random
* bytes arc4rand likes to give in one reseeding, whereas our
* sectorsize is far more likely to be in the same range.
*/
for (o = 0; o < wp->length; o += sc->sectorsize) {
arc4rand(d, sc->sectorsize, 0);
arc4rand(skey, sizeof skey, 0);
AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
AES_encrypt(&ci, &ki, d, d, sc->sectorsize);
d += sc->sectorsize;
}
/*
* Having written a long random sequence to disk here, we want to
* force a reseed, to avoid weakening the next time we use random
* data for something important.
*/
arc4rand(&o, sizeof o, 1);
}
/*
* Calculate the total payload size of the encrypted device.
*
* Security objectives: none.
*
* This function needs to agree with g_bde_map_sector() about things.
*/
uint64_t
g_bde_max_sector(struct g_bde_key *kp)
{
uint64_t maxsect;
maxsect = kp->media_width;
maxsect /= kp->zone_width;
maxsect *= kp->zone_cont;
return (maxsect);
}
/*
* Convert an unencrypted side offset to offsets on the encrypted side.
*
* Security objective: Make it harder to identify what sectors contain what
* on a "cold" disk image.
*
* We do this by adding the "keyoffset" from the lock to the physical sector
* number modulus the available number of sectors. Since all physical sectors
* presumably look the same cold, this will do.
*
* As part of the mapping we have to skip the lock sectors which we know
* the physical address off. We also truncate the work packet, respecting
* zone boundaries and lock sectors, so that we end up with a sequence of
* sectors which are physically contiguous.
*
* Shuffling things further is an option, but the incremental frustration is
* not currently deemed worth the run-time performance hit resulting from the
* increased number of disk arm movements it would incur.
*
* This function offers nothing but a trivial diversion for an attacker able
* to do "the cleaning lady attack" in its current static mapping form.
*/
void
g_bde_map_sector(struct g_bde_work *wp)
{
u_int zone, zoff, u, len;
uint64_t ko;
struct g_bde_softc *sc;
struct g_bde_key *kp;
sc = wp->softc;
kp = &sc->key;
/* find which zone and the offset in it */
zone = wp->offset / kp->zone_cont;
zoff = wp->offset % kp->zone_cont;
/* Calculate the offset of the key in the key sector */
wp->ko = (zoff / kp->sectorsize) * G_BDE_SKEYLEN;
/* restrict length to that zone */
len = kp->zone_cont - zoff;
/* ... and in general */
if (len > DFLTPHYS)
len = DFLTPHYS;
if (len < wp->length)
wp->length = len;
/* Find physical sector address */
wp->so = zone * kp->zone_width + zoff;
wp->so += kp->keyoffset;
wp->so %= kp->media_width;
if (wp->so + wp->length > kp->media_width)
wp->length = kp->media_width - wp->so;
wp->so += kp->sector0;
/* The key sector is the last in this zone. */
wp->kso = zone * kp->zone_width + kp->zone_cont;
wp->kso += kp->keyoffset;
wp->kso %= kp->media_width;
wp->kso += kp->sector0;
/* Compensate for lock sectors */
for (u = 0; u < G_BDE_MAXKEYS; u++) {
/* Find the start of this lock sector */
ko = kp->lsector[u] & ~((uint64_t)kp->sectorsize - 1);
if (wp->kso >= ko)
wp->kso += kp->sectorsize;
if (wp->so >= ko) {
/* lock sector before work packet */
wp->so += kp->sectorsize;
} else if ((wp->so + wp->length) > ko) {
/* lock sector in work packet, truncate */
wp->length = ko - wp->so;
}
}
#if 0
printf("off %jd len %jd so %jd ko %jd kso %u\n",
(intmax_t)wp->offset,
(intmax_t)wp->length,
(intmax_t)wp->so,
(intmax_t)wp->kso,
wp->ko);
#endif
KASSERT(wp->so + wp->length <= kp->sectorN,
("wp->so (%jd) + wp->length (%jd) > EOM (%jd), offset = %jd",
(intmax_t)wp->so,
(intmax_t)wp->length,
(intmax_t)kp->sectorN,
(intmax_t)wp->offset));
KASSERT(wp->kso + kp->sectorsize <= kp->sectorN,
("wp->kso (%jd) + kp->sectorsize > EOM (%jd), offset = %jd",
(intmax_t)wp->kso,
(intmax_t)kp->sectorN,
(intmax_t)wp->offset));
KASSERT(wp->so >= kp->sector0,
("wp->so (%jd) < BOM (%jd), offset = %jd",
(intmax_t)wp->so,
(intmax_t)kp->sector0,
(intmax_t)wp->offset));
KASSERT(wp->kso >= kp->sector0,
("wp->kso (%jd) <BOM (%jd), offset = %jd",
(intmax_t)wp->kso,
(intmax_t)kp->sector0,
(intmax_t)wp->offset));
}