xref: /freebsd/sys/geom/eli/g_eli_integrity.c (revision ae7e8a02e6e93455e026036132c4d053b2c12ad9)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2005-2011 Pawel Jakub Dawidek <pawel@dawidek.net>
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31 
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/kernel.h>
35 #include <sys/linker.h>
36 #include <sys/module.h>
37 #include <sys/lock.h>
38 #include <sys/mutex.h>
39 #include <sys/bio.h>
40 #include <sys/sysctl.h>
41 #include <sys/malloc.h>
42 #include <sys/kthread.h>
43 #include <sys/proc.h>
44 #include <sys/sched.h>
45 #include <sys/smp.h>
46 #include <sys/vnode.h>
47 
48 #include <vm/uma.h>
49 
50 #include <geom/geom.h>
51 #include <geom/geom_dbg.h>
52 #include <geom/eli/g_eli.h>
53 #include <geom/eli/pkcs5v2.h>
54 
55 /*
56  * The data layout description when integrity verification is configured.
57  *
58  * One of the most important assumption here is that authenticated data and its
59  * HMAC has to be stored in the same place (namely in the same sector) to make
60  * it work reliable.
61  * The problem is that file systems work only with sectors that are multiple of
62  * 512 bytes and a power of two number.
63  * My idea to implement it is as follows.
64  * Let's store HMAC in sector. This is a must. This leaves us 480 bytes for
65  * data. We can't use that directly (ie. we can't create provider with 480 bytes
66  * sector size). We need another sector from where we take only 32 bytes of data
67  * and we store HMAC of this data as well. This takes two sectors from the
68  * original provider at the input and leaves us one sector of authenticated data
69  * at the output. Not very efficient, but you got the idea.
70  * Now, let's assume, we want to create provider with 4096 bytes sector.
71  * To output 4096 bytes of authenticated data we need 8x480 plus 1x256, so we
72  * need nine 512-bytes sectors at the input to get one 4096-bytes sector at the
73  * output. That's better. With 4096 bytes sector we can use 89% of size of the
74  * original provider. I find it as an acceptable cost.
75  * The reliability comes from the fact, that every HMAC stored inside the sector
76  * is calculated only for the data in the same sector, so its impossible to
77  * write new data and leave old HMAC or vice versa.
78  *
79  * And here is the picture:
80  *
81  * da0: +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+-----+
82  *      |32b |480b| |32b |480b| |32b |480b| |32b |480b| |32b |480b| |32b |480b| |32b |480b| |32b |480b| |32b |256b |
83  *      |HMAC|Data| |HMAC|Data| |HMAC|Data| |HMAC|Data| |HMAC|Data| |HMAC|Data| |HMAC|Data| |HMAC|Data| |HMAC|Data |
84  *      +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+----+ +----+-----+
85  *      |512 bytes| |512 bytes| |512 bytes| |512 bytes| |512 bytes| |512 bytes| |512 bytes| |512 bytes| |288 bytes |
86  *      +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ |224 unused|
87  *                                                                                                      +----------+
88  * da0.eli: +----+----+----+----+----+----+----+----+----+
89  *          |480b|480b|480b|480b|480b|480b|480b|480b|256b|
90  *          +----+----+----+----+----+----+----+----+----+
91  *          |                 4096 bytes                 |
92  *          +--------------------------------------------+
93  *
94  * PS. You can use any sector size with geli(8). My example is using 4kB,
95  *     because it's most efficient. For 8kB sectors you need 2 extra sectors,
96  *     so the cost is the same as for 4kB sectors.
97  */
98 
99 /*
100  * Code paths:
101  * BIO_READ:
102  *	g_eli_start -> g_eli_auth_read -> g_io_request -> g_eli_read_done -> g_eli_auth_run -> g_eli_auth_read_done -> g_io_deliver
103  * BIO_WRITE:
104  *	g_eli_start -> g_eli_auth_run -> g_eli_auth_write_done -> g_io_request -> g_eli_write_done -> g_io_deliver
105  */
106 
107 MALLOC_DECLARE(M_ELI);
108 
109 /*
110  * Here we generate key for HMAC. Every sector has its own HMAC key, so it is
111  * not possible to copy sectors.
112  * We cannot depend on fact, that every sector has its own IV, because different
113  * IV doesn't change HMAC, when we use encrypt-then-authenticate method.
114  */
115 static void
116 g_eli_auth_keygen(struct g_eli_softc *sc, off_t offset, u_char *key)
117 {
118 	SHA256_CTX ctx;
119 
120 	/* Copy precalculated SHA256 context. */
121 	bcopy(&sc->sc_akeyctx, &ctx, sizeof(ctx));
122 	SHA256_Update(&ctx, (uint8_t *)&offset, sizeof(offset));
123 	SHA256_Final(key, &ctx);
124 }
125 
126 /*
127  * The function is called after we read and decrypt data.
128  *
129  * g_eli_start -> g_eli_auth_read -> g_io_request -> g_eli_read_done -> g_eli_auth_run -> G_ELI_AUTH_READ_DONE -> g_io_deliver
130  */
131 static int
132 g_eli_auth_read_done(struct cryptop *crp)
133 {
134 	struct g_eli_softc *sc;
135 	struct bio *bp;
136 
137 	if (crp->crp_etype == EAGAIN) {
138 		if (g_eli_crypto_rerun(crp) == 0)
139 			return (0);
140 	}
141 	bp = (struct bio *)crp->crp_opaque;
142 	bp->bio_inbed++;
143 	sc = bp->bio_to->geom->softc;
144 	if (crp->crp_etype == 0) {
145 		bp->bio_completed += crp->crp_payload_length;
146 		G_ELI_DEBUG(3, "Crypto READ request done (%d/%d) (add=%d completed=%jd).",
147 		    bp->bio_inbed, bp->bio_children, crp->crp_payload_length, (intmax_t)bp->bio_completed);
148 	} else {
149 		u_int nsec, decr_secsize, encr_secsize, rel_sec;
150 		int *errorp;
151 
152 		/* Sectorsize of decrypted provider eg. 4096. */
153 		decr_secsize = bp->bio_to->sectorsize;
154 		/* The real sectorsize of encrypted provider, eg. 512. */
155 		encr_secsize =
156 		    LIST_FIRST(&sc->sc_geom->consumer)->provider->sectorsize;
157 		/* Number of sectors from decrypted provider, eg. 2. */
158 		nsec = bp->bio_length / decr_secsize;
159 		/* Number of sectors from encrypted provider, eg. 18. */
160 		nsec = (nsec * sc->sc_bytes_per_sector) / encr_secsize;
161 		/* Which relative sector this request decrypted. */
162 		rel_sec = ((crp->crp_buf.cb_buf + crp->crp_payload_start) -
163 		    (char *)bp->bio_driver2) / encr_secsize;
164 
165 		errorp = (int *)((char *)bp->bio_driver2 + encr_secsize * nsec +
166 		    sizeof(int) * rel_sec);
167 		*errorp = crp->crp_etype;
168 		G_ELI_DEBUG(1,
169 		    "Crypto READ request failed (%d/%d) error=%d.",
170 		    bp->bio_inbed, bp->bio_children, crp->crp_etype);
171 		if (bp->bio_error == 0 || bp->bio_error == EINTEGRITY)
172 			bp->bio_error = crp->crp_etype == EBADMSG ?
173 			    EINTEGRITY : crp->crp_etype;
174 	}
175 	if (crp->crp_cipher_key != NULL)
176 		g_eli_key_drop(sc, __DECONST(void *, crp->crp_cipher_key));
177 	crypto_freereq(crp);
178 	/*
179 	 * Do we have all sectors already?
180 	 */
181 	if (bp->bio_inbed < bp->bio_children)
182 		return (0);
183 
184 	if (bp->bio_error == 0) {
185 		u_int i, lsec, nsec, data_secsize, decr_secsize, encr_secsize;
186 		u_char *srcdata, *dstdata;
187 
188 		/* Sectorsize of decrypted provider eg. 4096. */
189 		decr_secsize = bp->bio_to->sectorsize;
190 		/* The real sectorsize of encrypted provider, eg. 512. */
191 		encr_secsize = LIST_FIRST(&sc->sc_geom->consumer)->provider->sectorsize;
192 		/* Number of data bytes in one encrypted sector, eg. 480. */
193 		data_secsize = sc->sc_data_per_sector;
194 		/* Number of sectors from decrypted provider, eg. 2. */
195 		nsec = bp->bio_length / decr_secsize;
196 		/* Number of sectors from encrypted provider, eg. 18. */
197 		nsec = (nsec * sc->sc_bytes_per_sector) / encr_secsize;
198 		/* Last sector number in every big sector, eg. 9. */
199 		lsec = sc->sc_bytes_per_sector / encr_secsize;
200 
201 		srcdata = bp->bio_driver2;
202 		dstdata = bp->bio_data;
203 
204 		for (i = 1; i <= nsec; i++) {
205 			data_secsize = sc->sc_data_per_sector;
206 			if ((i % lsec) == 0)
207 				data_secsize = decr_secsize % data_secsize;
208 			bcopy(srcdata + sc->sc_alen, dstdata, data_secsize);
209 			srcdata += encr_secsize;
210 			dstdata += data_secsize;
211 		}
212 	} else if (bp->bio_error == EINTEGRITY) {
213 		u_int i, lsec, nsec, data_secsize, decr_secsize, encr_secsize;
214 		int *errorp;
215 		off_t coroff, corsize, dstoff;
216 
217 		/* Sectorsize of decrypted provider eg. 4096. */
218 		decr_secsize = bp->bio_to->sectorsize;
219 		/* The real sectorsize of encrypted provider, eg. 512. */
220 		encr_secsize = LIST_FIRST(&sc->sc_geom->consumer)->provider->sectorsize;
221 		/* Number of data bytes in one encrypted sector, eg. 480. */
222 		data_secsize = sc->sc_data_per_sector;
223 		/* Number of sectors from decrypted provider, eg. 2. */
224 		nsec = bp->bio_length / decr_secsize;
225 		/* Number of sectors from encrypted provider, eg. 18. */
226 		nsec = (nsec * sc->sc_bytes_per_sector) / encr_secsize;
227 		/* Last sector number in every big sector, eg. 9. */
228 		lsec = sc->sc_bytes_per_sector / encr_secsize;
229 
230 		errorp = (int *)((char *)bp->bio_driver2 + encr_secsize * nsec);
231 		coroff = -1;
232 		corsize = 0;
233 		dstoff = bp->bio_offset;
234 
235 		for (i = 1; i <= nsec; i++) {
236 			data_secsize = sc->sc_data_per_sector;
237 			if ((i % lsec) == 0)
238 				data_secsize = decr_secsize % data_secsize;
239 			if (errorp[i - 1] == EBADMSG) {
240 				/*
241 				 * Corruption detected, remember the offset if
242 				 * this is the first corrupted sector and
243 				 * increase size.
244 				 */
245 				if (coroff == -1)
246 					coroff = dstoff;
247 				corsize += data_secsize;
248 			} else {
249 				/*
250 				 * No corruption, good.
251 				 * Report previous corruption if there was one.
252 				 */
253 				if (coroff != -1) {
254 					G_ELI_DEBUG(0, "%s: Failed to authenticate %jd "
255 					    "bytes of data at offset %jd.",
256 					    sc->sc_name, (intmax_t)corsize,
257 					    (intmax_t)coroff);
258 					coroff = -1;
259 					corsize = 0;
260 				}
261 			}
262 			dstoff += data_secsize;
263 		}
264 		/* Report previous corruption if there was one. */
265 		if (coroff != -1) {
266 			G_ELI_DEBUG(0, "%s: Failed to authenticate %jd "
267 			    "bytes of data at offset %jd.",
268 			    sc->sc_name, (intmax_t)corsize, (intmax_t)coroff);
269 		}
270 	}
271 	free(bp->bio_driver2, M_ELI);
272 	bp->bio_driver2 = NULL;
273 	if (bp->bio_error != 0) {
274 		if (bp->bio_error != EINTEGRITY) {
275 			G_ELI_LOGREQ(0, bp,
276 			    "Crypto READ request failed (error=%d).",
277 			    bp->bio_error);
278 		}
279 		bp->bio_completed = 0;
280 	}
281 	/*
282 	 * Read is finished, send it up.
283 	 */
284 	g_io_deliver(bp, bp->bio_error);
285 	atomic_subtract_int(&sc->sc_inflight, 1);
286 	return (0);
287 }
288 
289 /*
290  * The function is called after data encryption.
291  *
292  * g_eli_start -> g_eli_auth_run -> G_ELI_AUTH_WRITE_DONE -> g_io_request -> g_eli_write_done -> g_io_deliver
293  */
294 static int
295 g_eli_auth_write_done(struct cryptop *crp)
296 {
297 	struct g_eli_softc *sc;
298 	struct g_consumer *cp;
299 	struct bio *bp, *cbp, *cbp2;
300 	u_int nsec;
301 
302 	if (crp->crp_etype == EAGAIN) {
303 		if (g_eli_crypto_rerun(crp) == 0)
304 			return (0);
305 	}
306 	bp = (struct bio *)crp->crp_opaque;
307 	bp->bio_inbed++;
308 	if (crp->crp_etype == 0) {
309 		G_ELI_DEBUG(3, "Crypto WRITE request done (%d/%d).",
310 		    bp->bio_inbed, bp->bio_children);
311 	} else {
312 		G_ELI_DEBUG(1, "Crypto WRITE request failed (%d/%d) error=%d.",
313 		    bp->bio_inbed, bp->bio_children, crp->crp_etype);
314 		if (bp->bio_error == 0)
315 			bp->bio_error = crp->crp_etype;
316 	}
317 	sc = bp->bio_to->geom->softc;
318 	if (crp->crp_cipher_key != NULL)
319 		g_eli_key_drop(sc, __DECONST(void *, crp->crp_cipher_key));
320 	crypto_freereq(crp);
321 	/*
322 	 * All sectors are already encrypted?
323 	 */
324 	if (bp->bio_inbed < bp->bio_children)
325 		return (0);
326 	if (bp->bio_error != 0) {
327 		G_ELI_LOGREQ(0, bp, "Crypto WRITE request failed (error=%d).",
328 		    bp->bio_error);
329 		free(bp->bio_driver2, M_ELI);
330 		bp->bio_driver2 = NULL;
331 		cbp = bp->bio_driver1;
332 		bp->bio_driver1 = NULL;
333 		g_destroy_bio(cbp);
334 		g_io_deliver(bp, bp->bio_error);
335 		atomic_subtract_int(&sc->sc_inflight, 1);
336 		return (0);
337 	}
338 	cp = LIST_FIRST(&sc->sc_geom->consumer);
339 	cbp = bp->bio_driver1;
340 	bp->bio_driver1 = NULL;
341 	cbp->bio_to = cp->provider;
342 	cbp->bio_done = g_eli_write_done;
343 
344 	/* Number of sectors from decrypted provider, eg. 1. */
345 	nsec = bp->bio_length / bp->bio_to->sectorsize;
346 	/* Number of sectors from encrypted provider, eg. 9. */
347 	nsec = (nsec * sc->sc_bytes_per_sector) / cp->provider->sectorsize;
348 
349 	cbp->bio_length = cp->provider->sectorsize * nsec;
350 	cbp->bio_offset = (bp->bio_offset / bp->bio_to->sectorsize) * sc->sc_bytes_per_sector;
351 	cbp->bio_data = bp->bio_driver2;
352 
353 	/*
354 	 * We write more than what is requested, so we have to be ready to write
355 	 * more than maxphys.
356 	 */
357 	cbp2 = NULL;
358 	if (cbp->bio_length > maxphys) {
359 		cbp2 = g_duplicate_bio(bp);
360 		cbp2->bio_length = cbp->bio_length - maxphys;
361 		cbp2->bio_data = cbp->bio_data + maxphys;
362 		cbp2->bio_offset = cbp->bio_offset + maxphys;
363 		cbp2->bio_to = cp->provider;
364 		cbp2->bio_done = g_eli_write_done;
365 		cbp->bio_length = maxphys;
366 	}
367 	/*
368 	 * Send encrypted data to the provider.
369 	 */
370 	G_ELI_LOGREQ(2, cbp, "Sending request.");
371 	bp->bio_inbed = 0;
372 	bp->bio_children = (cbp2 != NULL ? 2 : 1);
373 	g_io_request(cbp, cp);
374 	if (cbp2 != NULL) {
375 		G_ELI_LOGREQ(2, cbp2, "Sending request.");
376 		g_io_request(cbp2, cp);
377 	}
378 	return (0);
379 }
380 
381 void
382 g_eli_auth_read(struct g_eli_softc *sc, struct bio *bp)
383 {
384 	struct g_consumer *cp;
385 	struct bio *cbp, *cbp2;
386 	size_t size;
387 	off_t nsec;
388 
389 	bp->bio_pflags = 0;
390 
391 	cp = LIST_FIRST(&sc->sc_geom->consumer);
392 	cbp = bp->bio_driver1;
393 	bp->bio_driver1 = NULL;
394 	cbp->bio_to = cp->provider;
395 	cbp->bio_done = g_eli_read_done;
396 
397 	/* Number of sectors from decrypted provider, eg. 1. */
398 	nsec = bp->bio_length / bp->bio_to->sectorsize;
399 	/* Number of sectors from encrypted provider, eg. 9. */
400 	nsec = (nsec * sc->sc_bytes_per_sector) / cp->provider->sectorsize;
401 
402 	cbp->bio_length = cp->provider->sectorsize * nsec;
403 	size = cbp->bio_length;
404 	size += sizeof(int) * nsec;
405 	size += G_ELI_AUTH_SECKEYLEN * nsec;
406 	cbp->bio_offset = (bp->bio_offset / bp->bio_to->sectorsize) * sc->sc_bytes_per_sector;
407 	bp->bio_driver2 = malloc(size, M_ELI, M_WAITOK);
408 	cbp->bio_data = bp->bio_driver2;
409 
410 	/* Clear the error array. */
411 	memset((char *)bp->bio_driver2 + cbp->bio_length, 0,
412 	    sizeof(int) * nsec);
413 
414 	/*
415 	 * We read more than what is requested, so we have to be ready to read
416 	 * more than maxphys.
417 	 */
418 	cbp2 = NULL;
419 	if (cbp->bio_length > maxphys) {
420 		cbp2 = g_duplicate_bio(bp);
421 		cbp2->bio_length = cbp->bio_length - maxphys;
422 		cbp2->bio_data = cbp->bio_data + maxphys;
423 		cbp2->bio_offset = cbp->bio_offset + maxphys;
424 		cbp2->bio_to = cp->provider;
425 		cbp2->bio_done = g_eli_read_done;
426 		cbp->bio_length = maxphys;
427 	}
428 	/*
429 	 * Read encrypted data from provider.
430 	 */
431 	G_ELI_LOGREQ(2, cbp, "Sending request.");
432 	g_io_request(cbp, cp);
433 	if (cbp2 != NULL) {
434 		G_ELI_LOGREQ(2, cbp2, "Sending request.");
435 		g_io_request(cbp2, cp);
436 	}
437 }
438 
439 /*
440  * This is the main function responsible for cryptography (ie. communication
441  * with crypto(9) subsystem).
442  *
443  * BIO_READ:
444  *	g_eli_start -> g_eli_auth_read -> g_io_request -> g_eli_read_done -> G_ELI_AUTH_RUN -> g_eli_auth_read_done -> g_io_deliver
445  * BIO_WRITE:
446  *	g_eli_start -> G_ELI_AUTH_RUN -> g_eli_auth_write_done -> g_io_request -> g_eli_write_done -> g_io_deliver
447  */
448 void
449 g_eli_auth_run(struct g_eli_worker *wr, struct bio *bp)
450 {
451 	struct g_eli_softc *sc;
452 	struct cryptopq crpq;
453 	struct cryptop *crp;
454 	u_int i, lsec, nsec, data_secsize, decr_secsize, encr_secsize;
455 	off_t dstoff;
456 	u_char *p, *data, *authkey, *plaindata;
457 	int error;
458 	bool batch;
459 
460 	G_ELI_LOGREQ(3, bp, "%s", __func__);
461 
462 	bp->bio_pflags = wr->w_number;
463 	sc = wr->w_softc;
464 	/* Sectorsize of decrypted provider eg. 4096. */
465 	decr_secsize = bp->bio_to->sectorsize;
466 	/* The real sectorsize of encrypted provider, eg. 512. */
467 	encr_secsize = LIST_FIRST(&sc->sc_geom->consumer)->provider->sectorsize;
468 	/* Number of data bytes in one encrypted sector, eg. 480. */
469 	data_secsize = sc->sc_data_per_sector;
470 	/* Number of sectors from decrypted provider, eg. 2. */
471 	nsec = bp->bio_length / decr_secsize;
472 	/* Number of sectors from encrypted provider, eg. 18. */
473 	nsec = (nsec * sc->sc_bytes_per_sector) / encr_secsize;
474 	/* Last sector number in every big sector, eg. 9. */
475 	lsec = sc->sc_bytes_per_sector / encr_secsize;
476 	/* Destination offset, used for IV generation. */
477 	dstoff = (bp->bio_offset / bp->bio_to->sectorsize) * sc->sc_bytes_per_sector;
478 
479 	plaindata = bp->bio_data;
480 	if (bp->bio_cmd == BIO_READ) {
481 		data = bp->bio_driver2;
482 		p = data + encr_secsize * nsec;
483 		p += sizeof(int) * nsec;
484 	} else {
485 		size_t size;
486 
487 		size = encr_secsize * nsec;
488 		size += G_ELI_AUTH_SECKEYLEN * nsec;
489 		size += sizeof(uintptr_t);	/* Space for alignment. */
490 		data = malloc(size, M_ELI, M_WAITOK);
491 		bp->bio_driver2 = data;
492 		p = data + encr_secsize * nsec;
493 	}
494 	bp->bio_inbed = 0;
495 	bp->bio_children = nsec;
496 
497 #if defined(__mips_n64) || defined(__mips_o64)
498 	p = (char *)roundup((uintptr_t)p, sizeof(uintptr_t));
499 #endif
500 
501 	TAILQ_INIT(&crpq);
502 	batch = atomic_load_int(&g_eli_batch) != 0;
503 
504 	for (i = 1; i <= nsec; i++, dstoff += encr_secsize) {
505 		crp = crypto_getreq(wr->w_sid, M_WAITOK);
506 		authkey = (u_char *)p;		p += G_ELI_AUTH_SECKEYLEN;
507 
508 		data_secsize = sc->sc_data_per_sector;
509 		if ((i % lsec) == 0) {
510 			data_secsize = decr_secsize % data_secsize;
511 			/*
512 			 * Last encrypted sector of each decrypted sector is
513 			 * only partially filled.
514 			 */
515 			if (bp->bio_cmd == BIO_WRITE)
516 				memset(data + sc->sc_alen + data_secsize, 0,
517 				    encr_secsize - sc->sc_alen - data_secsize);
518 		} else if (data_secsize + sc->sc_alen != encr_secsize) {
519 			/*
520 			 * If the HMAC size is not a multiple of 128 bits, the
521 			 * per-sector data size is rounded down to ensure that
522 			 * encryption can be performed without requiring any
523 			 * padding.  In this case, each sector contains unused
524 			 * bytes.
525 			 */
526 			if (bp->bio_cmd == BIO_WRITE)
527 				memset(data + sc->sc_alen + data_secsize, 0,
528 				    encr_secsize - sc->sc_alen - data_secsize);
529 		}
530 
531 		if (bp->bio_cmd == BIO_WRITE) {
532 			bcopy(plaindata, data + sc->sc_alen, data_secsize);
533 			plaindata += data_secsize;
534 		}
535 
536 		crypto_use_buf(crp, data, sc->sc_alen + data_secsize);
537 		crp->crp_opaque = (void *)bp;
538 		data += encr_secsize;
539 		crp->crp_flags = CRYPTO_F_CBIFSYNC;
540 		if (bp->bio_cmd == BIO_WRITE) {
541 			crp->crp_callback = g_eli_auth_write_done;
542 			crp->crp_op = CRYPTO_OP_ENCRYPT |
543 			    CRYPTO_OP_COMPUTE_DIGEST;
544 		} else {
545 			crp->crp_callback = g_eli_auth_read_done;
546 			crp->crp_op = CRYPTO_OP_DECRYPT |
547 			    CRYPTO_OP_VERIFY_DIGEST;
548 		}
549 
550 		crp->crp_digest_start = 0;
551 		crp->crp_payload_start = sc->sc_alen;
552 		crp->crp_payload_length = data_secsize;
553 		if ((sc->sc_flags & G_ELI_FLAG_FIRST_KEY) == 0) {
554 			crp->crp_cipher_key = g_eli_key_hold(sc, dstoff,
555 			    encr_secsize);
556 		}
557 		if (g_eli_ivlen(sc->sc_ealgo) != 0) {
558 			crp->crp_flags |= CRYPTO_F_IV_SEPARATE;
559 			g_eli_crypto_ivgen(sc, dstoff, crp->crp_iv,
560 			    sizeof(crp->crp_iv));
561 		}
562 
563 		g_eli_auth_keygen(sc, dstoff, authkey);
564 		crp->crp_auth_key = authkey;
565 
566 		if (batch) {
567 			TAILQ_INSERT_TAIL(&crpq, crp, crp_next);
568 		} else {
569 			error = crypto_dispatch(crp);
570 			KASSERT(error == 0,
571 			    ("crypto_dispatch() failed (error=%d)", error));
572 		}
573 	}
574 
575 	if (batch)
576 		crypto_dispatch_batch(&crpq, 0);
577 }
578