1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2002 Poul-Henning Kamp
5 * Copyright (c) 2002 Networks Associates Technology, Inc.
6 * All rights reserved.
7 *
8 * This software was developed for the FreeBSD Project by Poul-Henning Kamp
9 * and NAI Labs, the Security Research Division of Network Associates, Inc.
10 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
11 * DARPA CHATS research program.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 * 1. Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 * 2. Redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
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-api-fst.h>
50 #include <crypto/sha2/sha512.h>
51
52 #include <geom/geom.h>
53 #include <geom/bde/g_bde.h>
54
55 /*
56 * XXX: Debugging DO NOT ENABLE
57 */
58 #undef MD5_KEY
59
60 /*
61 * Derive kkey from mkey + sector offset.
62 *
63 * Security objective: Derive a potentially very large number of distinct skeys
64 * from the comparatively small key material in our mkey, in such a way that
65 * if one, more or even many of the kkeys are compromised, this does not
66 * significantly help an attack on other kkeys and in particular does not
67 * weaken or compromise the mkey.
68 *
69 * First we MD5 hash the sectornumber with the salt from the lock sector.
70 * The salt prevents the precalculation and statistical analysis of the MD5
71 * output which would be possible if we only gave it the sectornumber.
72 *
73 * The MD5 hash is used to pick out 16 bytes from the masterkey, which
74 * are then hashed with MD5 together with the sector number.
75 *
76 * The resulting MD5 hash is the kkey.
77 */
78
79 static void
g_bde_kkey(struct g_bde_softc * sc,keyInstance * ki,int dir,off_t sector)80 g_bde_kkey(struct g_bde_softc *sc, keyInstance *ki, int dir, off_t sector)
81 {
82 u_int t;
83 MD5_CTX ct;
84 u_char buf[16];
85 u_char buf2[8];
86
87 /* We have to be architecture neutral */
88 le64enc(buf2, sector);
89
90 MD5Init(&ct);
91 MD5Update(&ct, sc->key.salt, 8);
92 MD5Update(&ct, buf2, sizeof buf2);
93 MD5Update(&ct, sc->key.salt + 8, 8);
94 MD5Final(buf, &ct);
95
96 MD5Init(&ct);
97 for (t = 0; t < 16; t++) {
98 MD5Update(&ct, &sc->key.mkey[buf[t]], 1);
99 if (t == 8)
100 MD5Update(&ct, buf2, sizeof buf2);
101 }
102 bzero(buf2, sizeof buf2);
103 MD5Final(buf, &ct);
104 bzero(&ct, sizeof ct);
105 AES_makekey(ki, dir, G_BDE_KKEYBITS, buf);
106 bzero(buf, sizeof buf);
107 }
108
109 /*
110 * Encryption work for read operation.
111 *
112 * Security objective: Find the kkey, find the skey, decrypt the sector data.
113 */
114
115 void
g_bde_crypt_read(struct g_bde_work * wp)116 g_bde_crypt_read(struct g_bde_work *wp)
117 {
118 struct g_bde_softc *sc;
119 u_char *d;
120 u_int n;
121 off_t o;
122 u_char skey[G_BDE_SKEYLEN];
123 keyInstance ki;
124 cipherInstance ci;
125
126 AES_init(&ci);
127 sc = wp->softc;
128 o = 0;
129 for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
130 d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
131 g_bde_kkey(sc, &ki, DIR_DECRYPT, wp->offset + o);
132 AES_decrypt(&ci, &ki, d, skey, sizeof skey);
133 d = (u_char *)wp->data + o;
134 AES_makekey(&ki, DIR_DECRYPT, G_BDE_SKEYBITS, skey);
135 AES_decrypt(&ci, &ki, d, d, sc->sectorsize);
136 }
137 bzero(skey, sizeof skey);
138 bzero(&ci, sizeof ci);
139 bzero(&ki, sizeof ki);
140 }
141
142 /*
143 * Encryption work for write operation.
144 *
145 * Security objective: Create random skey, encrypt sector data,
146 * encrypt skey with the kkey.
147 */
148
149 void
g_bde_crypt_write(struct g_bde_work * wp)150 g_bde_crypt_write(struct g_bde_work *wp)
151 {
152 u_char *s, *d;
153 struct g_bde_softc *sc;
154 u_int n;
155 off_t o;
156 u_char skey[G_BDE_SKEYLEN];
157 keyInstance ki;
158 cipherInstance ci;
159
160 sc = wp->softc;
161 AES_init(&ci);
162 o = 0;
163 for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
164 s = (u_char *)wp->data + o;
165 d = (u_char *)wp->sp->data + o;
166 arc4rand(skey, sizeof skey, 0);
167 AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
168 AES_encrypt(&ci, &ki, s, d, sc->sectorsize);
169
170 d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
171 g_bde_kkey(sc, &ki, DIR_ENCRYPT, wp->offset + o);
172 AES_encrypt(&ci, &ki, skey, d, sizeof skey);
173 bzero(skey, sizeof skey);
174 }
175 bzero(skey, sizeof skey);
176 bzero(&ci, sizeof ci);
177 bzero(&ki, sizeof ki);
178 }
179
180 /*
181 * Encryption work for delete operation.
182 *
183 * Security objective: Write random data to the sectors.
184 *
185 * XXX: At a hit in performance we would trash the encrypted skey as well.
186 * XXX: This would add frustration to the cleaning lady attack by making
187 * XXX: deletes look like writes.
188 */
189
190 void
g_bde_crypt_delete(struct g_bde_work * wp)191 g_bde_crypt_delete(struct g_bde_work *wp)
192 {
193 struct g_bde_softc *sc;
194 u_char *d;
195 off_t o;
196 u_char skey[G_BDE_SKEYLEN];
197 keyInstance ki;
198 cipherInstance ci;
199
200 sc = wp->softc;
201 d = wp->sp->data;
202 AES_init(&ci);
203 /*
204 * Do not unroll this loop!
205 * Our zone may be significantly wider than the amount of random
206 * bytes arc4rand likes to give in one reseeding, whereas our
207 * sectorsize is far more likely to be in the same range.
208 */
209 for (o = 0; o < wp->length; o += sc->sectorsize) {
210 arc4rand(d, sc->sectorsize, 0);
211 arc4rand(skey, sizeof skey, 0);
212 AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
213 AES_encrypt(&ci, &ki, d, d, sc->sectorsize);
214 d += sc->sectorsize;
215 }
216 /*
217 * Having written a long random sequence to disk here, we want to
218 * force a reseed, to avoid weakening the next time we use random
219 * data for something important.
220 */
221 arc4rand(&o, sizeof o, 1);
222 }
223
224 /*
225 * Calculate the total payload size of the encrypted device.
226 *
227 * Security objectives: none.
228 *
229 * This function needs to agree with g_bde_map_sector() about things.
230 */
231
232 uint64_t
g_bde_max_sector(struct g_bde_key * kp)233 g_bde_max_sector(struct g_bde_key *kp)
234 {
235 uint64_t maxsect;
236
237 maxsect = kp->media_width;
238 maxsect /= kp->zone_width;
239 maxsect *= kp->zone_cont;
240 return (maxsect);
241 }
242
243 /*
244 * Convert an unencrypted side offset to offsets on the encrypted side.
245 *
246 * Security objective: Make it harder to identify what sectors contain what
247 * on a "cold" disk image.
248 *
249 * We do this by adding the "keyoffset" from the lock to the physical sector
250 * number modulus the available number of sectors. Since all physical sectors
251 * presumably look the same cold, this will do.
252 *
253 * As part of the mapping we have to skip the lock sectors which we know
254 * the physical address off. We also truncate the work packet, respecting
255 * zone boundaries and lock sectors, so that we end up with a sequence of
256 * sectors which are physically contiguous.
257 *
258 * Shuffling things further is an option, but the incremental frustration is
259 * not currently deemed worth the run-time performance hit resulting from the
260 * increased number of disk arm movements it would incur.
261 *
262 * This function offers nothing but a trivial diversion for an attacker able
263 * to do "the cleaning lady attack" in its current static mapping form.
264 */
265
266 void
g_bde_map_sector(struct g_bde_work * wp)267 g_bde_map_sector(struct g_bde_work *wp)
268 {
269
270 u_int zone, zoff, u, len;
271 uint64_t ko;
272 struct g_bde_softc *sc;
273 struct g_bde_key *kp;
274
275 sc = wp->softc;
276 kp = &sc->key;
277
278 /* find which zone and the offset in it */
279 zone = wp->offset / kp->zone_cont;
280 zoff = wp->offset % kp->zone_cont;
281
282 /* Calculate the offset of the key in the key sector */
283 wp->ko = (zoff / kp->sectorsize) * G_BDE_SKEYLEN;
284
285 /* restrict length to that zone */
286 len = kp->zone_cont - zoff;
287
288 /* ... and in general */
289 if (len > DFLTPHYS)
290 len = DFLTPHYS;
291
292 if (len < wp->length)
293 wp->length = len;
294
295 /* Find physical sector address */
296 wp->so = zone * kp->zone_width + zoff;
297 wp->so += kp->keyoffset;
298 wp->so %= kp->media_width;
299 if (wp->so + wp->length > kp->media_width)
300 wp->length = kp->media_width - wp->so;
301 wp->so += kp->sector0;
302
303 /* The key sector is the last in this zone. */
304 wp->kso = zone * kp->zone_width + kp->zone_cont;
305 wp->kso += kp->keyoffset;
306 wp->kso %= kp->media_width;
307 wp->kso += kp->sector0;
308
309 /* Compensate for lock sectors */
310 for (u = 0; u < G_BDE_MAXKEYS; u++) {
311 /* Find the start of this lock sector */
312 ko = rounddown2(kp->lsector[u], (uint64_t)kp->sectorsize);
313
314 if (wp->kso >= ko)
315 wp->kso += kp->sectorsize;
316
317 if (wp->so >= ko) {
318 /* lock sector before work packet */
319 wp->so += kp->sectorsize;
320 } else if ((wp->so + wp->length) > ko) {
321 /* lock sector in work packet, truncate */
322 wp->length = ko - wp->so;
323 }
324 }
325
326 #if 0
327 printf("off %jd len %jd so %jd ko %jd kso %u\n",
328 (intmax_t)wp->offset,
329 (intmax_t)wp->length,
330 (intmax_t)wp->so,
331 (intmax_t)wp->kso,
332 wp->ko);
333 #endif
334 KASSERT(wp->so + wp->length <= kp->sectorN,
335 ("wp->so (%jd) + wp->length (%jd) > EOM (%jd), offset = %jd",
336 (intmax_t)wp->so,
337 (intmax_t)wp->length,
338 (intmax_t)kp->sectorN,
339 (intmax_t)wp->offset));
340
341 KASSERT(wp->kso + kp->sectorsize <= kp->sectorN,
342 ("wp->kso (%jd) + kp->sectorsize > EOM (%jd), offset = %jd",
343 (intmax_t)wp->kso,
344 (intmax_t)kp->sectorN,
345 (intmax_t)wp->offset));
346
347 KASSERT(wp->so >= kp->sector0,
348 ("wp->so (%jd) < BOM (%jd), offset = %jd",
349 (intmax_t)wp->so,
350 (intmax_t)kp->sector0,
351 (intmax_t)wp->offset));
352
353 KASSERT(wp->kso >= kp->sector0,
354 ("wp->kso (%jd) <BOM (%jd), offset = %jd",
355 (intmax_t)wp->kso,
356 (intmax_t)kp->sector0,
357 (intmax_t)wp->offset));
358 }
359