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/*- * 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: release/9.1.0/sys/geom/bde/g_bde_crypt.c 148192 2005-07-20 18:08:16Z phk $ */ /* 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-api-fst.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 compromise 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)); }