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: releng/5.1/sys/geom/bde/g_bde_crypt.c 114543 2003-05-02 19:08:57Z 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 * 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 compromised 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
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
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
127 AES_init(&ci);
128 sc = wp->softc;
129 o = 0;
130 for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
131 d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
132 g_bde_kkey(sc, &ki, DIR_DECRYPT, wp->offset + o);
133 AES_decrypt(&ci, &ki, d, skey, sizeof skey);
134 d = (u_char *)wp->data + o;
135 #ifdef MD5_KEY
136 {
137 MD5_CTX ct;
138 u_char rkey[16];
139 int i;
140
141 MD5Init(&ct);
142 MD5Update(&ct, d, sc->sectorsize);
143 MD5Final(rkey, &ct);
144 if (bcmp(rkey, skey, 16) != 0) {
145 #if 0
146 printf("MD5_KEY failed at %jd (t=%d)\n",
147 (intmax_t)(wp->offset + o), time_second);
148 #endif
149 for (i = 0; i < sc->sectorsize; i++)
150 d[i] = 'A' + i % 26;
151 sprintf(d, "MD5_KEY failed at %jd (t=%d)",
152 (intmax_t)(wp->offset + o), time_second);
153 }
154 }
155 #else
156 AES_makekey(&ki, DIR_DECRYPT, G_BDE_SKEYBITS, skey);
157 AES_decrypt(&ci, &ki, d, d, sc->sectorsize);
158 #endif
159 }
160 bzero(skey, sizeof skey);
161 bzero(&ci, sizeof ci);
162 bzero(&ki, sizeof ci);
163 }
164
165 /*
166 * Encryption work for write operation.
167 *
168 * Security objective: Create random skey, encrypt sector data,
169 * encrypt skey with the kkey.
170 */
171
172 void
173 g_bde_crypt_write(struct g_bde_work *wp)
174 {
175 u_char *s, *d;
176 struct g_bde_softc *sc;
177 u_int n;
178 off_t o;
179 u_char skey[G_BDE_SKEYLEN];
180 keyInstance ki;
181 cipherInstance ci;
182
183 sc = wp->softc;
184 AES_init(&ci);
185 o = 0;
186 for (n = 0; o < wp->length; n++, o += sc->sectorsize) {
187
188 s = (u_char *)wp->data + o;
189 d = (u_char *)wp->sp->data + o;
190 #ifdef MD5_KEY
191 {
192 MD5_CTX ct;
193
194 MD5Init(&ct);
195 MD5Update(&ct, s, sc->sectorsize);
196 MD5Final(skey, &ct);
197 bcopy(s, d, sc->sectorsize);
198 }
199 #else
200 arc4rand(&skey, sizeof skey, 0);
201 AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
202 AES_encrypt(&ci, &ki, s, d, sc->sectorsize);
203 #endif
204
205 d = (u_char *)wp->ksp->data + wp->ko + n * G_BDE_SKEYLEN;
206 g_bde_kkey(sc, &ki, DIR_ENCRYPT, wp->offset + o);
207 AES_encrypt(&ci, &ki, skey, d, sizeof skey);
208 bzero(skey, sizeof skey);
209 }
210 bzero(skey, sizeof skey);
211 bzero(&ci, sizeof ci);
212 bzero(&ki, sizeof ci);
213 }
214
215 /*
216 * Encryption work for delete operation.
217 *
218 * Security objective: Write random data to the sectors.
219 *
220 * XXX: At a hit in performance we would trash the encrypted skey as well.
221 * XXX: This would add frustration to the cleaning lady attack by making
222 * XXX: deletes look like writes.
223 */
224
225 void
226 g_bde_crypt_delete(struct g_bde_work *wp)
227 {
228 struct g_bde_softc *sc;
229 u_char *d;
230 off_t o;
231 u_char skey[G_BDE_SKEYLEN];
232 keyInstance ki;
233 cipherInstance ci;
234
235 sc = wp->softc;
236 d = wp->sp->data;
237 AES_init(&ci);
238 /*
239 * Do not unroll this loop!
240 * Our zone may be significantly wider than the amount of random
241 * bytes arc4rand likes to give in one reseeding, whereas our
242 * sectorsize is far more likely to be in the same range.
243 */
244 for (o = 0; o < wp->length; o += sc->sectorsize) {
245 arc4rand(d, sc->sectorsize, 0);
246 arc4rand(&skey, sizeof skey, 0);
247 AES_makekey(&ki, DIR_ENCRYPT, G_BDE_SKEYBITS, skey);
248 AES_encrypt(&ci, &ki, d, d, sc->sectorsize);
249 d += sc->sectorsize;
250 }
251 /*
252 * Having written a long random sequence to disk here, we want to
253 * force a reseed, to avoid weakening the next time we use random
254 * data for something important.
255 */
256 arc4rand(&o, sizeof o, 1);
257 }
258
259 /*
260 * Calculate the total payload size of the encrypted device.
261 *
262 * Security objectives: none.
263 *
264 * This function needs to agree with g_bde_map_sector() about things.
265 */
266
267 uint64_t
268 g_bde_max_sector(struct g_bde_key *kp)
269 {
270 uint64_t maxsect;
271
272 maxsect = kp->media_width;
273 maxsect /= kp->zone_width;
274 maxsect *= kp->zone_cont;
275 return (maxsect);
276 }
277
278 /*
279 * Convert an unencrypted side offset to offsets on the encrypted side.
280 *
281 * Security objective: Make it harder to identify what sectors contain what
282 * on a "cold" disk image.
283 *
284 * We do this by adding the "keyoffset" from the lock to the physical sector
285 * number modulus the available number of sectors. Since all physical sectors
286 * presumably look the same cold, this will do.
287 *
288 * As part of the mapping we have to skip the lock sectors which we know
289 * the physical address off. We also truncate the work packet, respecting
290 * zone boundaries and lock sectors, so that we end up with a sequence of
291 * sectors which are physically contiguous.
292 *
293 * Shuffling things further is an option, but the incremental frustration is
294 * not currently deemed worth the run-time performance hit resulting from the
295 * increased number of disk arm movements it would incur.
296 *
297 * This function offers nothing but a trivial diversion for an attacker able
298 * to do "the cleaning lady attack" in its current static mapping form.
299 */
300
301 void
302 g_bde_map_sector(struct g_bde_work *wp)
303 {
304
305 u_int zone, zoff, u, len;
306 uint64_t ko;
307 struct g_bde_softc *sc;
308 struct g_bde_key *kp;
309
310 sc = wp->softc;
311 kp = &sc->key;
312
313 /* find which zone and the offset in it */
314 zone = wp->offset / kp->zone_cont;
315 zoff = wp->offset % kp->zone_cont;
316
317 /* Calculate the offset of the key in the key sector */
318 wp->ko = (zoff / kp->sectorsize) * G_BDE_SKEYLEN;
319
320 /* restrict length to that zone */
321 len = kp->zone_cont - zoff;
322
323 /* ... and in general */
324 if (len > DFLTPHYS)
325 len = DFLTPHYS;
326
327 if (len < wp->length)
328 wp->length = len;
329
330 /* Find physical sector address */
331 wp->so = zone * kp->zone_width + zoff;
332 wp->so += kp->keyoffset;
333 wp->so %= kp->media_width;
334 if (wp->so + wp->length > kp->media_width)
335 wp->length = kp->media_width - wp->so;
336 wp->so += kp->sector0;
337
338 /* The key sector is the last in this zone. */
339 wp->kso = zone * kp->zone_width + kp->zone_cont;
340 wp->kso += kp->keyoffset;
341 wp->kso %= kp->media_width;
342 wp->kso += kp->sector0;
343
344 /* Compensate for lock sectors */
345 for (u = 0; u < G_BDE_MAXKEYS; u++) {
346 /* Find the start of this lock sector */
347 ko = kp->lsector[u] & ~(kp->sectorsize - 1);
348
349 if (wp->kso >= ko)
350 wp->kso += kp->sectorsize;
351
352 if (wp->so >= ko) {
353 /* lock sector before work packet */
354 wp->so += kp->sectorsize;
355 } else if ((wp->so + wp->length) > ko) {
356 /* lock sector in work packet, truncate */
357 wp->length = ko - wp->so;
358 }
359 }
360
361 #if 0
362 printf("off %jd len %jd so %jd ko %jd kso %u\n",
363 (intmax_t)wp->offset,
364 (intmax_t)wp->length,
365 (intmax_t)wp->so,
366 (intmax_t)wp->kso,
367 wp->ko);
368 #endif
369 KASSERT(wp->so + wp->length <= kp->sectorN,
370 ("wp->so (%jd) + wp->length (%jd) > EOM (%jd), offset = %jd",
371 (intmax_t)wp->so,
372 (intmax_t)wp->length,
373 (intmax_t)kp->sectorN,
374 (intmax_t)wp->offset));
375
376 KASSERT(wp->kso + kp->sectorsize <= kp->sectorN,
377 ("wp->kso (%jd) + kp->sectorsize > EOM (%jd), offset = %jd",
378 (intmax_t)wp->kso,
379 (intmax_t)kp->sectorN,
380 (intmax_t)wp->offset));
381
382 KASSERT(wp->so >= kp->sector0,
383 ("wp->so (%jd) < BOM (%jd), offset = %jd",
384 (intmax_t)wp->so,
385 (intmax_t)kp->sector0,
386 (intmax_t)wp->offset));
387
388 KASSERT(wp->kso >= kp->sector0,
389 ("wp->kso (%jd) <BOM (%jd), offset = %jd",
390 (intmax_t)wp->kso,
391 (intmax_t)kp->sector0,
392 (intmax_t)wp->offset));
393 }
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