5afa461402
Replace ARC4 with SHA2-512. Change lock-structure encoding to use random ordering rather for obscurity. Encrypt lock-structure with AES/256 instead of AES/128. Change kkey derivation to be MD5 hash based. Watch for malloc(M_NOWAIT) failures and ditch our cache when they happen. Remove clause 3 of the license with NAI Labs consent. Many thanks to "Lucky Green" <shamrock@cypherpunks.to> and "David Wagner" <daw@cs.berkeley.edu>, for code reading, inputs and suggestions. This code has still not been stared at for 10 years by a gang of hard-core cryptographers. Discretion advised. NB: These changes result in the on-disk format changing: dump/restore needed. Sponsored by: DARPA & NAI Labs.
302 lines
8.3 KiB
C
302 lines
8.3 KiB
C
/*-
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* Copyright (c) 2002 Poul-Henning Kamp
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* Copyright (c) 2002 Networks Associates Technology, Inc.
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* All rights reserved.
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*
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* This software was developed for the FreeBSD Project by Poul-Henning Kamp
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* and NAI Labs, the Security Research Division of Network Associates, Inc.
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* under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
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* DARPA CHATS research program.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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* This source file contains the functions responsible for the crypto, keying
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* and mapping operations on the I/O requests.
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*
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*/
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#include <sys/param.h>
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#include <sys/stdint.h>
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#include <sys/bio.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/queue.h>
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#include <sys/malloc.h>
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#include <sys/libkern.h>
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#include <sys/md5.h>
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#include <crypto/rijndael/rijndael.h>
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#include <crypto/sha2/sha2.h>
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#include <geom/geom.h>
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#include <geom/bde/g_bde.h>
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/*
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* Derive kkey from mkey + sector offset.
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*
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* Security objective: Derive a potentially very large number of distinct skeys
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* from the comparatively small key material in our mkey, in such a way that
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* if one, more or even many of the kkeys are compromised, this does not
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* significantly help an attack on other kkeys and in particular does not
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* weaken or compromised the mkey.
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*
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* First we MD5 hash the sectornumber with the salt from the lock sector.
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* The salt prevents the precalculation and statistical analysis of the MD5
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* output which would be possible if we only gave it the sectornumber.
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*
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* The MD5 hash is used to pick out 16 bytes from the masterkey, which
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* are then hashed with MD5 together with the sector number.
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*
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* The resulting MD5 hash is the kkey.
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*/
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static void
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g_bde_kkey(struct g_bde_softc *sc, keyInstance *ki, int dir, off_t sector)
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{
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u_int t;
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MD5_CTX ct;
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u_char buf[16];
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u_char buf2[8];
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/* We have to be architecture neutral */
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g_enc_le8(buf2, sector);
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MD5Init(&ct);
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MD5Update(&ct, sc->key.salt, 8);
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MD5Update(&ct, buf2, sizeof buf2);
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MD5Update(&ct, sc->key.salt + 8, 8);
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MD5Final(buf, &ct);
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MD5Init(&ct);
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for (t = 0; t < 16; t++) {
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MD5Update(&ct, &sc->key.mkey[buf[t]], 1);
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if (t == 8)
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MD5Update(&ct, buf2, sizeof buf2);
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}
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bzero(buf2, sizeof buf2);
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MD5Final(buf, &ct);
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bzero(&ct, sizeof ct);
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AES_makekey(ki, dir, G_BDE_KKEYBITS, buf);
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bzero(buf, sizeof buf);
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}
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/*
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* Encryption work for read operation.
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*
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* Security objective: Find the kkey, find the skey, decrypt the sector data.
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*/
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void
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g_bde_crypt_read(struct g_bde_work *wp)
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{
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struct g_bde_softc *sc;
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u_char *d;
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u_int n;
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off_t o;
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u_char skey[G_BDE_SKEYLEN];
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keyInstance ki;
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cipherInstance ci;
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AES_init(&ci);
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sc = wp->softc;
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o = 0;
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for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
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d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
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g_bde_kkey(sc, &ki, DIR_DECRYPT, wp->offset + o);
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AES_decrypt(&ci, &ki, d, skey, sizeof skey);
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d = (u_char *)wp->data + o;
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AES_makekey(&ki, DIR_DECRYPT, G_BDE_SKEYBITS, skey);
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AES_decrypt(&ci, &ki, d, d, sc->sectorsize);
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}
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bzero(skey, sizeof skey);
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bzero(&ci, sizeof ci);
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bzero(&ki, sizeof ci);
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}
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/*
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* Encryption work for write operation.
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*
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* Security objective: Create random skey, encrypt sector data,
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* encrypt skey with the kkey.
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*/
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void
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g_bde_crypt_write(struct g_bde_work *wp)
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{
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u_char *s, *d;
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struct g_bde_softc *sc;
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u_int n;
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off_t o;
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u_char skey[G_BDE_SKEYLEN];
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keyInstance ki;
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cipherInstance ci;
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sc = wp->softc;
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AES_init(&ci);
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o = 0;
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for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
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s = (u_char *)wp->data + o;
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d = (u_char *)wp->sp->data + o;
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arc4rand(&skey, sizeof skey, 0);
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AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
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AES_encrypt(&ci, &ki, s, d, sc->sectorsize);
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d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
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g_bde_kkey(sc, &ki, DIR_ENCRYPT, wp->offset + o);
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AES_encrypt(&ci, &ki, skey, d, sizeof skey);
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bzero(skey, sizeof skey);
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}
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bzero(skey, sizeof skey);
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bzero(&ci, sizeof ci);
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bzero(&ki, sizeof ci);
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}
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/*
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* Encryption work for delete operation.
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*
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* Security objective: Write random data to the sectors.
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*
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* XXX: At a hit in performance we would trash the encrypted skey as well.
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* XXX: This would add frustration to the cleaning lady attack by making
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* XXX: deletes look like writes.
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*/
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void
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g_bde_crypt_delete(struct g_bde_work *wp)
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{
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struct g_bde_softc *sc;
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u_char *d;
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off_t o;
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sc = wp->softc;
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d = wp->sp->data;
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/*
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* Do not unroll this loop!
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* Our zone may be significantly wider than the amount of random
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* bytes arc4rand likes to give in one reseeding, whereas our
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* sectorsize is far more likely to be in the same range.
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*/
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for (o = 0; o < wp->length; o += sc->sectorsize) {
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arc4rand(d, sc->sectorsize, 0);
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d += sc->sectorsize;
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}
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/*
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* Having written a long random sequence to disk here, we want to
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* force a reseed, to avoid weakening the next time we use random
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* data for something important.
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*/
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arc4rand(&o, sizeof o, 1);
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}
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/*
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* Calculate the total payload size of the encrypted device.
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*
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* Security objectives: none.
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*
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* This function needs to agree with g_bde_map_sector() about things.
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*/
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uint64_t
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g_bde_max_sector(struct g_bde_key *kp)
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{
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uint64_t maxsect;
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maxsect = kp->media_width;
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maxsect /= kp->zone_width;
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maxsect *= kp->zone_cont;
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return (maxsect);
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}
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/*
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* Convert an unencrypted side offset to offsets on the encrypted side.
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*
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* Security objective: Make it harder to identify what sectors contain what
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* on a "cold" disk image.
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*
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* We do this by adding the "keyoffset" from the lock to the physical sector
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* number modulus the available number of sectors, since all physical sectors
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* presumably look the same cold, this should be enough.
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*
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* Shuffling things further is an option, but the incremental frustration is
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* not currently deemed worth the run-time performance hit resulting from the
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* increased number of disk arm movements it would incur.
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*
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* This function offers nothing but a trivial diversion for an attacker able
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* to do "the cleaning lady attack" in its current static mapping form.
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*/
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void
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g_bde_map_sector(struct g_bde_key *kp,
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uint64_t isector,
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uint64_t *osector,
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uint64_t *ksector,
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u_int *koffset)
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{
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u_int zone, zoff, zidx, u;
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uint64_t os;
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/* find which zone and the offset and index in it */
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zone = isector / kp->zone_cont;
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zoff = isector % kp->zone_cont;
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zidx = zoff / kp->sectorsize;
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/* Find physical sector address */
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os = zone * kp->zone_width + zoff;
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os += kp->keyoffset;
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os %= kp->media_width - (G_BDE_MAXKEYS * kp->sectorsize);
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os += kp->sector0;
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/* Compensate for lock sectors */
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for (u = 0; u < G_BDE_MAXKEYS; u++)
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if (os >= kp->lsector[u])
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os += kp->sectorsize;
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*osector = os;
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/* The key sector is the last in this zone. */
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os = (1 + zone) * kp->zone_width - kp->sectorsize;
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os += kp->keyoffset;
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os %= kp->media_width - (G_BDE_MAXKEYS * kp->sectorsize);
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os += kp->sector0;
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for (u = 0; u < G_BDE_MAXKEYS; u++)
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if (os >= kp->lsector[u])
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os += kp->sectorsize;
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*ksector = os;
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*koffset = zidx * G_BDE_SKEYLEN;
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#if 0
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printf("off %jd %jd %jd %u\n",
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(intmax_t)isector,
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(intmax_t)*osector,
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(intmax_t)*ksector,
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*koffset);
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#endif
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}
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