1/*-
2 * Copyright (c) 2002 Poul-Henning Kamp
3 * Copyright (c) 2002 Networks Associates Technology, Inc.
4 * All rights reserved.
5 *
6 * This software was developed for the FreeBSD Project by Poul-Henning Kamp
7 * and NAI Labs, the Security Research Division of Network Associates, Inc.
8 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
9 * DARPA CHATS research program.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
|
32 * $FreeBSD: head/sys/geom/bde/g_bde_crypt.c 113010 2003-04-03 11:33:51Z phk $
|
| 32 * $FreeBSD: head/sys/geom/bde/g_bde_crypt.c 114153 2003-04-28 06:38:31Z phk $ |
33 *
34 * This source file contains the functions responsible for the crypto, keying
35 * and mapping operations on the I/O requests.
36 *
37 */
38
39#include <sys/param.h>
40#include <sys/bio.h>
41#include <sys/lock.h>
42#include <sys/mutex.h>
43#include <sys/queue.h>
44#include <sys/malloc.h>
45#include <sys/libkern.h>
46#include <sys/endian.h>
47#include <sys/md5.h>
48
49#include <crypto/rijndael/rijndael.h>
50#include <crypto/sha2/sha2.h>
51
52#include <geom/geom.h>
53#include <geom/bde/g_bde.h>
54
55
|
56#define MD5_KEY
57 |
58/*
59 * Derive kkey from mkey + sector offset.
60 *
61 * Security objective: Derive a potentially very large number of distinct skeys
62 * from the comparatively small key material in our mkey, in such a way that
63 * if one, more or even many of the kkeys are compromised, this does not
64 * significantly help an attack on other kkeys and in particular does not
65 * weaken or compromised the mkey.
66 *
67 * First we MD5 hash the sectornumber with the salt from the lock sector.
68 * The salt prevents the precalculation and statistical analysis of the MD5
69 * output which would be possible if we only gave it the sectornumber.
70 *
71 * The MD5 hash is used to pick out 16 bytes from the masterkey, which
72 * are then hashed with MD5 together with the sector number.
73 *
74 * The resulting MD5 hash is the kkey.
75 */
76
77static void
78g_bde_kkey(struct g_bde_softc *sc, keyInstance *ki, int dir, off_t sector)
79{
80 u_int t;
81 MD5_CTX ct;
82 u_char buf[16];
83 u_char buf2[8];
84
85 /* We have to be architecture neutral */
86 le64enc(buf2, sector);
87
88 MD5Init(&ct);
89 MD5Update(&ct, sc->key.salt, 8);
90 MD5Update(&ct, buf2, sizeof buf2);
91 MD5Update(&ct, sc->key.salt + 8, 8);
92 MD5Final(buf, &ct);
93
94 MD5Init(&ct);
95 for (t = 0; t < 16; t++) {
96 MD5Update(&ct, &sc->key.mkey[buf[t]], 1);
97 if (t == 8)
98 MD5Update(&ct, buf2, sizeof buf2);
99 }
100 bzero(buf2, sizeof buf2);
101 MD5Final(buf, &ct);
102 bzero(&ct, sizeof ct);
103 AES_makekey(ki, dir, G_BDE_KKEYBITS, buf);
104 bzero(buf, sizeof buf);
105}
106
107/*
108 * Encryption work for read operation.
109 *
110 * Security objective: Find the kkey, find the skey, decrypt the sector data.
111 */
112
113void
114g_bde_crypt_read(struct g_bde_work *wp)
115{
116 struct g_bde_softc *sc;
117 u_char *d;
118 u_int n;
119 off_t o;
120 u_char skey[G_BDE_SKEYLEN];
121 keyInstance ki;
122 cipherInstance ci;
123
124
125 AES_init(&ci);
126 sc = wp->softc;
127 o = 0;
128 for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
129 d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
130 g_bde_kkey(sc, &ki, DIR_DECRYPT, wp->offset + o);
131 AES_decrypt(&ci, &ki, d, skey, sizeof skey);
132 d = (u_char *)wp->data + o;
|
133#ifdef MD5_KEY
134 {
135 MD5_CTX ct;
136 u_char rkey[16];
137 int i;
138
139 MD5Init(&ct);
140 MD5Update(&ct, d, sc->sectorsize);
141 MD5Final(rkey, &ct);
142 if (bcmp(rkey, skey, 16) != 0) {
143#if 0
144 printf("MD5_KEY failed at %jd (t=%d)\n",
145 (intmax_t)(wp->offset + o), time_second);
146#endif
147 for (i = 0; i < sc->sectorsize; i++)
148 d[i] = 'A' + i % 26;
149 sprintf(d, "MD5_KEY failed at %jd (t=%d)",
150 (intmax_t)(wp->offset + o), time_second);
151 }
152 }
153#else |
154 AES_makekey(&ki, DIR_DECRYPT, G_BDE_SKEYBITS, skey);
155 AES_decrypt(&ci, &ki, d, d, sc->sectorsize);
|
| 156#endif |
157 }
158 bzero(skey, sizeof skey);
159 bzero(&ci, sizeof ci);
160 bzero(&ki, sizeof ci);
161}
162
163/*
164 * Encryption work for write operation.
165 *
166 * Security objective: Create random skey, encrypt sector data,
167 * encrypt skey with the kkey.
168 */
169
170void
171g_bde_crypt_write(struct g_bde_work *wp)
172{
173 u_char *s, *d;
174 struct g_bde_softc *sc;
175 u_int n;
176 off_t o;
177 u_char skey[G_BDE_SKEYLEN];
178 keyInstance ki;
179 cipherInstance ci;
180
181 sc = wp->softc;
182 AES_init(&ci);
183 o = 0;
184 for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
185
186 s = (u_char *)wp->data + o;
187 d = (u_char *)wp->sp->data + o;
|
188#ifdef MD5_KEY
189 {
190 MD5_CTX ct;
191
192 MD5Init(&ct);
193 MD5Update(&ct, s, sc->sectorsize);
194 MD5Final(skey, &ct);
195 bcopy(s, d, sc->sectorsize);
196 }
197#else |
198 arc4rand(&skey, sizeof skey, 0);
199 AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
200 AES_encrypt(&ci, &ki, s, d, sc->sectorsize);
|
| 201#endif |
202
203 d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
204 g_bde_kkey(sc, &ki, DIR_ENCRYPT, wp->offset + o);
205 AES_encrypt(&ci, &ki, skey, d, sizeof skey);
206 bzero(skey, sizeof skey);
207 }
208 bzero(skey, sizeof skey);
209 bzero(&ci, sizeof ci);
210 bzero(&ki, sizeof ci);
211}
212
213/*
214 * Encryption work for delete operation.
215 *
216 * Security objective: Write random data to the sectors.
217 *
218 * XXX: At a hit in performance we would trash the encrypted skey as well.
219 * XXX: This would add frustration to the cleaning lady attack by making
220 * XXX: deletes look like writes.
221 */
222
223void
224g_bde_crypt_delete(struct g_bde_work *wp)
225{
226 struct g_bde_softc *sc;
227 u_char *d;
228 off_t o;
229 u_char skey[G_BDE_SKEYLEN];
230 keyInstance ki;
231 cipherInstance ci;
232
233 sc = wp->softc;
234 d = wp->sp->data;
235 AES_init(&ci);
236 /*
237 * Do not unroll this loop!
238 * Our zone may be significantly wider than the amount of random
239 * bytes arc4rand likes to give in one reseeding, whereas our
240 * sectorsize is far more likely to be in the same range.
241 */
242 for (o = 0; o < wp->length; o += sc->sectorsize) {
243 arc4rand(d, sc->sectorsize, 0);
244 arc4rand(&skey, sizeof skey, 0);
245 AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
246 AES_encrypt(&ci, &ki, d, d, sc->sectorsize);
247 d += sc->sectorsize;
248 }
249 /*
250 * Having written a long random sequence to disk here, we want to
251 * force a reseed, to avoid weakening the next time we use random
252 * data for something important.
253 */
254 arc4rand(&o, sizeof o, 1);
255}
256
257/*
258 * Calculate the total payload size of the encrypted device.
259 *
260 * Security objectives: none.
261 *
262 * This function needs to agree with g_bde_map_sector() about things.
263 */
264
265uint64_t
266g_bde_max_sector(struct g_bde_key *kp)
267{
268 uint64_t maxsect;
269
270 maxsect = kp->media_width;
271 maxsect /= kp->zone_width;
272 maxsect *= kp->zone_cont;
273 return (maxsect);
274}
275
276/*
277 * Convert an unencrypted side offset to offsets on the encrypted side.
278 *
279 * Security objective: Make it harder to identify what sectors contain what
280 * on a "cold" disk image.
281 *
282 * We do this by adding the "keyoffset" from the lock to the physical sector
283 * number modulus the available number of sectors. Since all physical sectors
284 * presumably look the same cold, this will do.
285 *
286 * As part of the mapping we have to skip the lock sectors which we know
287 * the physical address off. We also truncate the work packet, respecting
288 * zone boundaries and lock sectors, so that we end up with a sequence of
289 * sectors which are physically contiguous.
290 *
291 * Shuffling things further is an option, but the incremental frustration is
292 * not currently deemed worth the run-time performance hit resulting from the
293 * increased number of disk arm movements it would incur.
294 *
295 * This function offers nothing but a trivial diversion for an attacker able
296 * to do "the cleaning lady attack" in its current static mapping form.
297 */
298
299void
300g_bde_map_sector(struct g_bde_work *wp)
301{
302
303 u_int zone, zoff, u, len;
304 uint64_t ko;
305 struct g_bde_softc *sc;
306 struct g_bde_key *kp;
307
308 sc = wp->softc;
309 kp = &sc->key;
310
311 /* find which zone and the offset in it */
312 zone = wp->offset / kp->zone_cont;
313 zoff = wp->offset % kp->zone_cont;
314
315 /* Calculate the offset of the key in the key sector */
316 wp->ko = (zoff / kp->sectorsize) * G_BDE_SKEYLEN;
317
318 /* restrict length to that zone */
319 len = kp->zone_cont - zoff;
320
321 /* ... and in general */
322 if (len > DFLTPHYS)
323 len = DFLTPHYS;
324
325 if (len < wp->length)
326 wp->length = len;
327
328 /* Find physical sector address */
329 wp->so = zone * kp->zone_width + zoff;
330 wp->so += kp->keyoffset;
331 wp->so %= kp->media_width;
332 wp->so += kp->sector0;
333
334 /* The key sector is the last in this zone. */
335 wp->kso = zone * kp->zone_width + kp->zone_cont;
336 wp->kso += kp->keyoffset;
337 wp->kso %= kp->media_width;
338 wp->kso += kp->sector0;
339
340 /* Compensate for lock sectors */
341 for (u = 0; u < G_BDE_MAXKEYS; u++) {
342 /* Find the start of this lock sector */
343 ko = kp->lsector[u] & ~(kp->sectorsize - 1);
344
345 if (wp->kso >= ko)
346 wp->kso += kp->sectorsize;
347
348 if (wp->so >= ko) {
349 /* lock sector before work packet */
350 wp->so += kp->sectorsize;
351 } else if ((wp->so + wp->length) > ko) {
352 /* lock sector in work packet, truncate */
353 wp->length = ko - wp->so;
354 }
355 }
356
357#if 0
358 printf("off %jd len %jd so %jd ko %jd kso %u\n",
359 (intmax_t)wp->offset,
360 (intmax_t)wp->length,
361 (intmax_t)wp->so,
362 (intmax_t)wp->kso,
363 wp->ko);
364#endif
365}
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