xref: /linux/net/sunrpc/auth_gss/gss_krb5_crypto.c (revision f34b580514c9816a317764e6b138ec66a4adab25)
1 /*
2  *  linux/net/sunrpc/gss_krb5_crypto.c
3  *
4  *  Copyright (c) 2000-2008 The Regents of the University of Michigan.
5  *  All rights reserved.
6  *
7  *  Andy Adamson   <andros@umich.edu>
8  *  Bruce Fields   <bfields@umich.edu>
9  */
10 
11 /*
12  * Copyright (C) 1998 by the FundsXpress, INC.
13  *
14  * All rights reserved.
15  *
16  * Export of this software from the United States of America may require
17  * a specific license from the United States Government.  It is the
18  * responsibility of any person or organization contemplating export to
19  * obtain such a license before exporting.
20  *
21  * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
22  * distribute this software and its documentation for any purpose and
23  * without fee is hereby granted, provided that the above copyright
24  * notice appear in all copies and that both that copyright notice and
25  * this permission notice appear in supporting documentation, and that
26  * the name of FundsXpress. not be used in advertising or publicity pertaining
27  * to distribution of the software without specific, written prior
28  * permission.  FundsXpress makes no representations about the suitability of
29  * this software for any purpose.  It is provided "as is" without express
30  * or implied warranty.
31  *
32  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
33  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
34  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
35  */
36 
37 #include <crypto/hash.h>
38 #include <crypto/skcipher.h>
39 #include <crypto/utils.h>
40 #include <linux/err.h>
41 #include <linux/types.h>
42 #include <linux/mm.h>
43 #include <linux/scatterlist.h>
44 #include <linux/highmem.h>
45 #include <linux/pagemap.h>
46 #include <linux/random.h>
47 #include <linux/sunrpc/gss_krb5.h>
48 #include <linux/sunrpc/xdr.h>
49 #include <kunit/visibility.h>
50 
51 #include "gss_krb5_internal.h"
52 
53 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
54 # define RPCDBG_FACILITY        RPCDBG_AUTH
55 #endif
56 
57 /**
58  * krb5_make_confounder - Generate a confounder string
59  * @p: memory location into which to write the string
60  * @conflen: string length to write, in octets
61  *
62  * RFCs 1964 and 3961 mention only "a random confounder" without going
63  * into detail about its function or cryptographic requirements. The
64  * assumed purpose is to prevent repeated encryption of a plaintext with
65  * the same key from generating the same ciphertext. It is also used to
66  * pad minimum plaintext length to at least a single cipher block.
67  *
68  * However, in situations like the GSS Kerberos 5 mechanism, where the
69  * encryption IV is always all zeroes, the confounder also effectively
70  * functions like an IV. Thus, not only must it be unique from message
71  * to message, but it must also be difficult to predict. Otherwise an
72  * attacker can correlate the confounder to previous or future values,
73  * making the encryption easier to break.
74  *
75  * Given that the primary consumer of this encryption mechanism is a
76  * network storage protocol, a type of traffic that often carries
77  * predictable payloads (eg, all zeroes when reading unallocated blocks
78  * from a file), our confounder generation has to be cryptographically
79  * strong.
80  */
81 void krb5_make_confounder(u8 *p, int conflen)
82 {
83 	get_random_bytes(p, conflen);
84 }
85 
86 /**
87  * krb5_encrypt - simple encryption of an RPCSEC GSS payload
88  * @tfm: initialized cipher transform
89  * @iv: pointer to an IV
90  * @in: plaintext to encrypt
91  * @out: OUT: ciphertext
92  * @length: length of input and output buffers, in bytes
93  *
94  * @iv may be NULL to force the use of an all-zero IV.
95  * The buffer containing the IV must be as large as the
96  * cipher's ivsize.
97  *
98  * Return values:
99  *   %0: @in successfully encrypted into @out
100  *   negative errno: @in not encrypted
101  */
102 u32
103 krb5_encrypt(
104 	struct crypto_sync_skcipher *tfm,
105 	void * iv,
106 	void * in,
107 	void * out,
108 	int length)
109 {
110 	u32 ret = -EINVAL;
111 	struct scatterlist sg[1];
112 	u8 local_iv[GSS_KRB5_MAX_BLOCKSIZE] = {0};
113 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
114 
115 	if (length % crypto_sync_skcipher_blocksize(tfm) != 0)
116 		goto out;
117 
118 	if (crypto_sync_skcipher_ivsize(tfm) > GSS_KRB5_MAX_BLOCKSIZE) {
119 		dprintk("RPC:       gss_k5encrypt: tfm iv size too large %d\n",
120 			crypto_sync_skcipher_ivsize(tfm));
121 		goto out;
122 	}
123 
124 	if (iv)
125 		memcpy(local_iv, iv, crypto_sync_skcipher_ivsize(tfm));
126 
127 	memcpy(out, in, length);
128 	sg_init_one(sg, out, length);
129 
130 	skcipher_request_set_sync_tfm(req, tfm);
131 	skcipher_request_set_callback(req, 0, NULL, NULL);
132 	skcipher_request_set_crypt(req, sg, sg, length, local_iv);
133 
134 	ret = crypto_skcipher_encrypt(req);
135 	skcipher_request_zero(req);
136 out:
137 	dprintk("RPC:       krb5_encrypt returns %d\n", ret);
138 	return ret;
139 }
140 
141 /**
142  * krb5_decrypt - simple decryption of an RPCSEC GSS payload
143  * @tfm: initialized cipher transform
144  * @iv: pointer to an IV
145  * @in: ciphertext to decrypt
146  * @out: OUT: plaintext
147  * @length: length of input and output buffers, in bytes
148  *
149  * @iv may be NULL to force the use of an all-zero IV.
150  * The buffer containing the IV must be as large as the
151  * cipher's ivsize.
152  *
153  * Return values:
154  *   %0: @in successfully decrypted into @out
155  *   negative errno: @in not decrypted
156  */
157 u32
158 krb5_decrypt(
159      struct crypto_sync_skcipher *tfm,
160      void * iv,
161      void * in,
162      void * out,
163      int length)
164 {
165 	u32 ret = -EINVAL;
166 	struct scatterlist sg[1];
167 	u8 local_iv[GSS_KRB5_MAX_BLOCKSIZE] = {0};
168 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
169 
170 	if (length % crypto_sync_skcipher_blocksize(tfm) != 0)
171 		goto out;
172 
173 	if (crypto_sync_skcipher_ivsize(tfm) > GSS_KRB5_MAX_BLOCKSIZE) {
174 		dprintk("RPC:       gss_k5decrypt: tfm iv size too large %d\n",
175 			crypto_sync_skcipher_ivsize(tfm));
176 		goto out;
177 	}
178 	if (iv)
179 		memcpy(local_iv, iv, crypto_sync_skcipher_ivsize(tfm));
180 
181 	memcpy(out, in, length);
182 	sg_init_one(sg, out, length);
183 
184 	skcipher_request_set_sync_tfm(req, tfm);
185 	skcipher_request_set_callback(req, 0, NULL, NULL);
186 	skcipher_request_set_crypt(req, sg, sg, length, local_iv);
187 
188 	ret = crypto_skcipher_decrypt(req);
189 	skcipher_request_zero(req);
190 out:
191 	dprintk("RPC:       gss_k5decrypt returns %d\n",ret);
192 	return ret;
193 }
194 
195 static int
196 checksummer(struct scatterlist *sg, void *data)
197 {
198 	struct ahash_request *req = data;
199 
200 	ahash_request_set_crypt(req, sg, NULL, sg->length);
201 
202 	return crypto_ahash_update(req);
203 }
204 
205 /*
206  * checksum the plaintext data and hdrlen bytes of the token header
207  * The checksum is performed over the first 8 bytes of the
208  * gss token header and then over the data body
209  */
210 u32
211 make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
212 	      struct xdr_buf *body, int body_offset, u8 *cksumkey,
213 	      unsigned int usage, struct xdr_netobj *cksumout)
214 {
215 	struct crypto_ahash *tfm;
216 	struct ahash_request *req;
217 	struct scatterlist              sg[1];
218 	int err = -1;
219 	u8 *checksumdata;
220 	unsigned int checksumlen;
221 
222 	if (cksumout->len < kctx->gk5e->cksumlength) {
223 		dprintk("%s: checksum buffer length, %u, too small for %s\n",
224 			__func__, cksumout->len, kctx->gk5e->name);
225 		return GSS_S_FAILURE;
226 	}
227 
228 	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_KERNEL);
229 	if (checksumdata == NULL)
230 		return GSS_S_FAILURE;
231 
232 	tfm = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
233 	if (IS_ERR(tfm))
234 		goto out_free_cksum;
235 
236 	req = ahash_request_alloc(tfm, GFP_KERNEL);
237 	if (!req)
238 		goto out_free_ahash;
239 
240 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
241 
242 	checksumlen = crypto_ahash_digestsize(tfm);
243 
244 	if (cksumkey != NULL) {
245 		err = crypto_ahash_setkey(tfm, cksumkey,
246 					  kctx->gk5e->keylength);
247 		if (err)
248 			goto out;
249 	}
250 
251 	err = crypto_ahash_init(req);
252 	if (err)
253 		goto out;
254 	sg_init_one(sg, header, hdrlen);
255 	ahash_request_set_crypt(req, sg, NULL, hdrlen);
256 	err = crypto_ahash_update(req);
257 	if (err)
258 		goto out;
259 	err = xdr_process_buf(body, body_offset, body->len - body_offset,
260 			      checksummer, req);
261 	if (err)
262 		goto out;
263 	ahash_request_set_crypt(req, NULL, checksumdata, 0);
264 	err = crypto_ahash_final(req);
265 	if (err)
266 		goto out;
267 
268 	switch (kctx->gk5e->ctype) {
269 	case CKSUMTYPE_RSA_MD5:
270 		err = krb5_encrypt(kctx->seq, NULL, checksumdata,
271 				   checksumdata, checksumlen);
272 		if (err)
273 			goto out;
274 		memcpy(cksumout->data,
275 		       checksumdata + checksumlen - kctx->gk5e->cksumlength,
276 		       kctx->gk5e->cksumlength);
277 		break;
278 	case CKSUMTYPE_HMAC_SHA1_DES3:
279 		memcpy(cksumout->data, checksumdata, kctx->gk5e->cksumlength);
280 		break;
281 	default:
282 		BUG();
283 		break;
284 	}
285 	cksumout->len = kctx->gk5e->cksumlength;
286 out:
287 	ahash_request_free(req);
288 out_free_ahash:
289 	crypto_free_ahash(tfm);
290 out_free_cksum:
291 	kfree(checksumdata);
292 	return err ? GSS_S_FAILURE : 0;
293 }
294 
295 /**
296  * gss_krb5_checksum - Compute the MAC for a GSS Wrap or MIC token
297  * @tfm: an initialized hash transform
298  * @header: pointer to a buffer containing the token header, or NULL
299  * @hdrlen: number of octets in @header
300  * @body: xdr_buf containing an RPC message (body.len is the message length)
301  * @body_offset: byte offset into @body to start checksumming
302  * @cksumout: OUT: a buffer to be filled in with the computed HMAC
303  *
304  * Usually expressed as H = HMAC(K, message)[1..h] .
305  *
306  * Caller provides the truncation length of the output token (h) in
307  * cksumout.len.
308  *
309  * Return values:
310  *   %GSS_S_COMPLETE: Digest computed, @cksumout filled in
311  *   %GSS_S_FAILURE: Call failed
312  */
313 u32
314 gss_krb5_checksum(struct crypto_ahash *tfm, char *header, int hdrlen,
315 		  const struct xdr_buf *body, int body_offset,
316 		  struct xdr_netobj *cksumout)
317 {
318 	struct ahash_request *req;
319 	int err = -ENOMEM;
320 	u8 *checksumdata;
321 
322 	checksumdata = kmalloc(crypto_ahash_digestsize(tfm), GFP_KERNEL);
323 	if (!checksumdata)
324 		return GSS_S_FAILURE;
325 
326 	req = ahash_request_alloc(tfm, GFP_KERNEL);
327 	if (!req)
328 		goto out_free_cksum;
329 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
330 	err = crypto_ahash_init(req);
331 	if (err)
332 		goto out_free_ahash;
333 
334 	/*
335 	 * Per RFC 4121 Section 4.2.4, the checksum is performed over the
336 	 * data body first, then over the octets in "header".
337 	 */
338 	err = xdr_process_buf(body, body_offset, body->len - body_offset,
339 			      checksummer, req);
340 	if (err)
341 		goto out_free_ahash;
342 	if (header) {
343 		struct scatterlist sg[1];
344 
345 		sg_init_one(sg, header, hdrlen);
346 		ahash_request_set_crypt(req, sg, NULL, hdrlen);
347 		err = crypto_ahash_update(req);
348 		if (err)
349 			goto out_free_ahash;
350 	}
351 
352 	ahash_request_set_crypt(req, NULL, checksumdata, 0);
353 	err = crypto_ahash_final(req);
354 	if (err)
355 		goto out_free_ahash;
356 
357 	memcpy(cksumout->data, checksumdata,
358 	       min_t(int, cksumout->len, crypto_ahash_digestsize(tfm)));
359 
360 out_free_ahash:
361 	ahash_request_free(req);
362 out_free_cksum:
363 	kfree_sensitive(checksumdata);
364 	return err ? GSS_S_FAILURE : GSS_S_COMPLETE;
365 }
366 EXPORT_SYMBOL_IF_KUNIT(gss_krb5_checksum);
367 
368 struct encryptor_desc {
369 	u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
370 	struct skcipher_request *req;
371 	int pos;
372 	struct xdr_buf *outbuf;
373 	struct page **pages;
374 	struct scatterlist infrags[4];
375 	struct scatterlist outfrags[4];
376 	int fragno;
377 	int fraglen;
378 };
379 
380 static int
381 encryptor(struct scatterlist *sg, void *data)
382 {
383 	struct encryptor_desc *desc = data;
384 	struct xdr_buf *outbuf = desc->outbuf;
385 	struct crypto_sync_skcipher *tfm =
386 		crypto_sync_skcipher_reqtfm(desc->req);
387 	struct page *in_page;
388 	int thislen = desc->fraglen + sg->length;
389 	int fraglen, ret;
390 	int page_pos;
391 
392 	/* Worst case is 4 fragments: head, end of page 1, start
393 	 * of page 2, tail.  Anything more is a bug. */
394 	BUG_ON(desc->fragno > 3);
395 
396 	page_pos = desc->pos - outbuf->head[0].iov_len;
397 	if (page_pos >= 0 && page_pos < outbuf->page_len) {
398 		/* pages are not in place: */
399 		int i = (page_pos + outbuf->page_base) >> PAGE_SHIFT;
400 		in_page = desc->pages[i];
401 	} else {
402 		in_page = sg_page(sg);
403 	}
404 	sg_set_page(&desc->infrags[desc->fragno], in_page, sg->length,
405 		    sg->offset);
406 	sg_set_page(&desc->outfrags[desc->fragno], sg_page(sg), sg->length,
407 		    sg->offset);
408 	desc->fragno++;
409 	desc->fraglen += sg->length;
410 	desc->pos += sg->length;
411 
412 	fraglen = thislen & (crypto_sync_skcipher_blocksize(tfm) - 1);
413 	thislen -= fraglen;
414 
415 	if (thislen == 0)
416 		return 0;
417 
418 	sg_mark_end(&desc->infrags[desc->fragno - 1]);
419 	sg_mark_end(&desc->outfrags[desc->fragno - 1]);
420 
421 	skcipher_request_set_crypt(desc->req, desc->infrags, desc->outfrags,
422 				   thislen, desc->iv);
423 
424 	ret = crypto_skcipher_encrypt(desc->req);
425 	if (ret)
426 		return ret;
427 
428 	sg_init_table(desc->infrags, 4);
429 	sg_init_table(desc->outfrags, 4);
430 
431 	if (fraglen) {
432 		sg_set_page(&desc->outfrags[0], sg_page(sg), fraglen,
433 				sg->offset + sg->length - fraglen);
434 		desc->infrags[0] = desc->outfrags[0];
435 		sg_assign_page(&desc->infrags[0], in_page);
436 		desc->fragno = 1;
437 		desc->fraglen = fraglen;
438 	} else {
439 		desc->fragno = 0;
440 		desc->fraglen = 0;
441 	}
442 	return 0;
443 }
444 
445 struct decryptor_desc {
446 	u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
447 	struct skcipher_request *req;
448 	struct scatterlist frags[4];
449 	int fragno;
450 	int fraglen;
451 };
452 
453 static int
454 decryptor(struct scatterlist *sg, void *data)
455 {
456 	struct decryptor_desc *desc = data;
457 	int thislen = desc->fraglen + sg->length;
458 	struct crypto_sync_skcipher *tfm =
459 		crypto_sync_skcipher_reqtfm(desc->req);
460 	int fraglen, ret;
461 
462 	/* Worst case is 4 fragments: head, end of page 1, start
463 	 * of page 2, tail.  Anything more is a bug. */
464 	BUG_ON(desc->fragno > 3);
465 	sg_set_page(&desc->frags[desc->fragno], sg_page(sg), sg->length,
466 		    sg->offset);
467 	desc->fragno++;
468 	desc->fraglen += sg->length;
469 
470 	fraglen = thislen & (crypto_sync_skcipher_blocksize(tfm) - 1);
471 	thislen -= fraglen;
472 
473 	if (thislen == 0)
474 		return 0;
475 
476 	sg_mark_end(&desc->frags[desc->fragno - 1]);
477 
478 	skcipher_request_set_crypt(desc->req, desc->frags, desc->frags,
479 				   thislen, desc->iv);
480 
481 	ret = crypto_skcipher_decrypt(desc->req);
482 	if (ret)
483 		return ret;
484 
485 	sg_init_table(desc->frags, 4);
486 
487 	if (fraglen) {
488 		sg_set_page(&desc->frags[0], sg_page(sg), fraglen,
489 				sg->offset + sg->length - fraglen);
490 		desc->fragno = 1;
491 		desc->fraglen = fraglen;
492 	} else {
493 		desc->fragno = 0;
494 		desc->fraglen = 0;
495 	}
496 	return 0;
497 }
498 
499 /*
500  * This function makes the assumption that it was ultimately called
501  * from gss_wrap().
502  *
503  * The client auth_gss code moves any existing tail data into a
504  * separate page before calling gss_wrap.
505  * The server svcauth_gss code ensures that both the head and the
506  * tail have slack space of RPC_MAX_AUTH_SIZE before calling gss_wrap.
507  *
508  * Even with that guarantee, this function may be called more than
509  * once in the processing of gss_wrap().  The best we can do is
510  * verify at compile-time (see GSS_KRB5_SLACK_CHECK) that the
511  * largest expected shift will fit within RPC_MAX_AUTH_SIZE.
512  * At run-time we can verify that a single invocation of this
513  * function doesn't attempt to use more the RPC_MAX_AUTH_SIZE.
514  */
515 
516 int
517 xdr_extend_head(struct xdr_buf *buf, unsigned int base, unsigned int shiftlen)
518 {
519 	u8 *p;
520 
521 	if (shiftlen == 0)
522 		return 0;
523 
524 	BUG_ON(shiftlen > RPC_MAX_AUTH_SIZE);
525 
526 	p = buf->head[0].iov_base + base;
527 
528 	memmove(p + shiftlen, p, buf->head[0].iov_len - base);
529 
530 	buf->head[0].iov_len += shiftlen;
531 	buf->len += shiftlen;
532 
533 	return 0;
534 }
535 
536 static u32
537 gss_krb5_cts_crypt(struct crypto_sync_skcipher *cipher, struct xdr_buf *buf,
538 		   u32 offset, u8 *iv, struct page **pages, int encrypt)
539 {
540 	u32 ret;
541 	struct scatterlist sg[1];
542 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, cipher);
543 	u8 *data;
544 	struct page **save_pages;
545 	u32 len = buf->len - offset;
546 
547 	if (len > GSS_KRB5_MAX_BLOCKSIZE * 2) {
548 		WARN_ON(0);
549 		return -ENOMEM;
550 	}
551 	data = kmalloc(GSS_KRB5_MAX_BLOCKSIZE * 2, GFP_KERNEL);
552 	if (!data)
553 		return -ENOMEM;
554 
555 	/*
556 	 * For encryption, we want to read from the cleartext
557 	 * page cache pages, and write the encrypted data to
558 	 * the supplied xdr_buf pages.
559 	 */
560 	save_pages = buf->pages;
561 	if (encrypt)
562 		buf->pages = pages;
563 
564 	ret = read_bytes_from_xdr_buf(buf, offset, data, len);
565 	buf->pages = save_pages;
566 	if (ret)
567 		goto out;
568 
569 	sg_init_one(sg, data, len);
570 
571 	skcipher_request_set_sync_tfm(req, cipher);
572 	skcipher_request_set_callback(req, 0, NULL, NULL);
573 	skcipher_request_set_crypt(req, sg, sg, len, iv);
574 
575 	if (encrypt)
576 		ret = crypto_skcipher_encrypt(req);
577 	else
578 		ret = crypto_skcipher_decrypt(req);
579 
580 	skcipher_request_zero(req);
581 
582 	if (ret)
583 		goto out;
584 
585 	ret = write_bytes_to_xdr_buf(buf, offset, data, len);
586 
587 #if IS_ENABLED(CONFIG_KUNIT)
588 	/*
589 	 * CBC-CTS does not define an output IV but RFC 3962 defines it as the
590 	 * penultimate block of ciphertext, so copy that into the IV buffer
591 	 * before returning.
592 	 */
593 	if (encrypt)
594 		memcpy(iv, data, crypto_sync_skcipher_ivsize(cipher));
595 #endif
596 
597 out:
598 	kfree(data);
599 	return ret;
600 }
601 
602 /**
603  * krb5_cbc_cts_encrypt - encrypt in CBC mode with CTS
604  * @cts_tfm: CBC cipher with CTS
605  * @cbc_tfm: base CBC cipher
606  * @offset: starting byte offset for plaintext
607  * @buf: OUT: output buffer
608  * @pages: plaintext
609  * @iv: output CBC initialization vector, or NULL
610  * @ivsize: size of @iv, in octets
611  *
612  * To provide confidentiality, encrypt using cipher block chaining
613  * with ciphertext stealing. Message integrity is handled separately.
614  *
615  * Return values:
616  *   %0: encryption successful
617  *   negative errno: encryption could not be completed
618  */
619 VISIBLE_IF_KUNIT
620 int krb5_cbc_cts_encrypt(struct crypto_sync_skcipher *cts_tfm,
621 			 struct crypto_sync_skcipher *cbc_tfm,
622 			 u32 offset, struct xdr_buf *buf, struct page **pages,
623 			 u8 *iv, unsigned int ivsize)
624 {
625 	u32 blocksize, nbytes, nblocks, cbcbytes;
626 	struct encryptor_desc desc;
627 	int err;
628 
629 	blocksize = crypto_sync_skcipher_blocksize(cts_tfm);
630 	nbytes = buf->len - offset;
631 	nblocks = (nbytes + blocksize - 1) / blocksize;
632 	cbcbytes = 0;
633 	if (nblocks > 2)
634 		cbcbytes = (nblocks - 2) * blocksize;
635 
636 	memset(desc.iv, 0, sizeof(desc.iv));
637 
638 	/* Handle block-sized chunks of plaintext with CBC. */
639 	if (cbcbytes) {
640 		SYNC_SKCIPHER_REQUEST_ON_STACK(req, cbc_tfm);
641 
642 		desc.pos = offset;
643 		desc.fragno = 0;
644 		desc.fraglen = 0;
645 		desc.pages = pages;
646 		desc.outbuf = buf;
647 		desc.req = req;
648 
649 		skcipher_request_set_sync_tfm(req, cbc_tfm);
650 		skcipher_request_set_callback(req, 0, NULL, NULL);
651 
652 		sg_init_table(desc.infrags, 4);
653 		sg_init_table(desc.outfrags, 4);
654 
655 		err = xdr_process_buf(buf, offset, cbcbytes, encryptor, &desc);
656 		skcipher_request_zero(req);
657 		if (err)
658 			return err;
659 	}
660 
661 	/* Remaining plaintext is handled with CBC-CTS. */
662 	err = gss_krb5_cts_crypt(cts_tfm, buf, offset + cbcbytes,
663 				 desc.iv, pages, 1);
664 	if (err)
665 		return err;
666 
667 	if (unlikely(iv))
668 		memcpy(iv, desc.iv, ivsize);
669 	return 0;
670 }
671 EXPORT_SYMBOL_IF_KUNIT(krb5_cbc_cts_encrypt);
672 
673 /**
674  * krb5_cbc_cts_decrypt - decrypt in CBC mode with CTS
675  * @cts_tfm: CBC cipher with CTS
676  * @cbc_tfm: base CBC cipher
677  * @offset: starting byte offset for plaintext
678  * @buf: OUT: output buffer
679  *
680  * Return values:
681  *   %0: decryption successful
682  *   negative errno: decryption could not be completed
683  */
684 VISIBLE_IF_KUNIT
685 int krb5_cbc_cts_decrypt(struct crypto_sync_skcipher *cts_tfm,
686 			 struct crypto_sync_skcipher *cbc_tfm,
687 			 u32 offset, struct xdr_buf *buf)
688 {
689 	u32 blocksize, nblocks, cbcbytes;
690 	struct decryptor_desc desc;
691 	int err;
692 
693 	blocksize = crypto_sync_skcipher_blocksize(cts_tfm);
694 	nblocks = (buf->len + blocksize - 1) / blocksize;
695 	cbcbytes = 0;
696 	if (nblocks > 2)
697 		cbcbytes = (nblocks - 2) * blocksize;
698 
699 	memset(desc.iv, 0, sizeof(desc.iv));
700 
701 	/* Handle block-sized chunks of plaintext with CBC. */
702 	if (cbcbytes) {
703 		SYNC_SKCIPHER_REQUEST_ON_STACK(req, cbc_tfm);
704 
705 		desc.fragno = 0;
706 		desc.fraglen = 0;
707 		desc.req = req;
708 
709 		skcipher_request_set_sync_tfm(req, cbc_tfm);
710 		skcipher_request_set_callback(req, 0, NULL, NULL);
711 
712 		sg_init_table(desc.frags, 4);
713 
714 		err = xdr_process_buf(buf, 0, cbcbytes, decryptor, &desc);
715 		skcipher_request_zero(req);
716 		if (err)
717 			return err;
718 	}
719 
720 	/* Remaining plaintext is handled with CBC-CTS. */
721 	return gss_krb5_cts_crypt(cts_tfm, buf, cbcbytes, desc.iv, NULL, 0);
722 }
723 EXPORT_SYMBOL_IF_KUNIT(krb5_cbc_cts_decrypt);
724 
725 u32
726 gss_krb5_aes_encrypt(struct krb5_ctx *kctx, u32 offset,
727 		     struct xdr_buf *buf, struct page **pages)
728 {
729 	u32 err;
730 	struct xdr_netobj hmac;
731 	u8 *ecptr;
732 	struct crypto_sync_skcipher *cipher, *aux_cipher;
733 	struct crypto_ahash *ahash;
734 	struct page **save_pages;
735 	unsigned int conflen;
736 
737 	if (kctx->initiate) {
738 		cipher = kctx->initiator_enc;
739 		aux_cipher = kctx->initiator_enc_aux;
740 		ahash = kctx->initiator_integ;
741 	} else {
742 		cipher = kctx->acceptor_enc;
743 		aux_cipher = kctx->acceptor_enc_aux;
744 		ahash = kctx->acceptor_integ;
745 	}
746 	conflen = crypto_sync_skcipher_blocksize(cipher);
747 
748 	/* hide the gss token header and insert the confounder */
749 	offset += GSS_KRB5_TOK_HDR_LEN;
750 	if (xdr_extend_head(buf, offset, conflen))
751 		return GSS_S_FAILURE;
752 	krb5_make_confounder(buf->head[0].iov_base + offset, conflen);
753 	offset -= GSS_KRB5_TOK_HDR_LEN;
754 
755 	if (buf->tail[0].iov_base != NULL) {
756 		ecptr = buf->tail[0].iov_base + buf->tail[0].iov_len;
757 	} else {
758 		buf->tail[0].iov_base = buf->head[0].iov_base
759 							+ buf->head[0].iov_len;
760 		buf->tail[0].iov_len = 0;
761 		ecptr = buf->tail[0].iov_base;
762 	}
763 
764 	/* copy plaintext gss token header after filler (if any) */
765 	memcpy(ecptr, buf->head[0].iov_base + offset, GSS_KRB5_TOK_HDR_LEN);
766 	buf->tail[0].iov_len += GSS_KRB5_TOK_HDR_LEN;
767 	buf->len += GSS_KRB5_TOK_HDR_LEN;
768 
769 	hmac.len = kctx->gk5e->cksumlength;
770 	hmac.data = buf->tail[0].iov_base + buf->tail[0].iov_len;
771 
772 	/*
773 	 * When we are called, pages points to the real page cache
774 	 * data -- which we can't go and encrypt!  buf->pages points
775 	 * to scratch pages which we are going to send off to the
776 	 * client/server.  Swap in the plaintext pages to calculate
777 	 * the hmac.
778 	 */
779 	save_pages = buf->pages;
780 	buf->pages = pages;
781 
782 	err = gss_krb5_checksum(ahash, NULL, 0, buf,
783 				offset + GSS_KRB5_TOK_HDR_LEN, &hmac);
784 	buf->pages = save_pages;
785 	if (err)
786 		return GSS_S_FAILURE;
787 
788 	err = krb5_cbc_cts_encrypt(cipher, aux_cipher,
789 				   offset + GSS_KRB5_TOK_HDR_LEN,
790 				   buf, pages, NULL, 0);
791 	if (err)
792 		return GSS_S_FAILURE;
793 
794 	/* Now update buf to account for HMAC */
795 	buf->tail[0].iov_len += kctx->gk5e->cksumlength;
796 	buf->len += kctx->gk5e->cksumlength;
797 
798 	return GSS_S_COMPLETE;
799 }
800 
801 u32
802 gss_krb5_aes_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len,
803 		     struct xdr_buf *buf, u32 *headskip, u32 *tailskip)
804 {
805 	struct crypto_sync_skcipher *cipher, *aux_cipher;
806 	struct crypto_ahash *ahash;
807 	struct xdr_netobj our_hmac_obj;
808 	u8 our_hmac[GSS_KRB5_MAX_CKSUM_LEN];
809 	u8 pkt_hmac[GSS_KRB5_MAX_CKSUM_LEN];
810 	struct xdr_buf subbuf;
811 	u32 ret = 0;
812 
813 	if (kctx->initiate) {
814 		cipher = kctx->acceptor_enc;
815 		aux_cipher = kctx->acceptor_enc_aux;
816 		ahash = kctx->acceptor_integ;
817 	} else {
818 		cipher = kctx->initiator_enc;
819 		aux_cipher = kctx->initiator_enc_aux;
820 		ahash = kctx->initiator_integ;
821 	}
822 
823 	/* create a segment skipping the header and leaving out the checksum */
824 	xdr_buf_subsegment(buf, &subbuf, offset + GSS_KRB5_TOK_HDR_LEN,
825 				    (len - offset - GSS_KRB5_TOK_HDR_LEN -
826 				     kctx->gk5e->cksumlength));
827 
828 	ret = krb5_cbc_cts_decrypt(cipher, aux_cipher, 0, &subbuf);
829 	if (ret)
830 		goto out_err;
831 
832 	our_hmac_obj.len = kctx->gk5e->cksumlength;
833 	our_hmac_obj.data = our_hmac;
834 	ret = gss_krb5_checksum(ahash, NULL, 0, &subbuf, 0, &our_hmac_obj);
835 	if (ret)
836 		goto out_err;
837 
838 	/* Get the packet's hmac value */
839 	ret = read_bytes_from_xdr_buf(buf, len - kctx->gk5e->cksumlength,
840 				      pkt_hmac, kctx->gk5e->cksumlength);
841 	if (ret)
842 		goto out_err;
843 
844 	if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
845 		ret = GSS_S_BAD_SIG;
846 		goto out_err;
847 	}
848 	*headskip = crypto_sync_skcipher_blocksize(cipher);
849 	*tailskip = kctx->gk5e->cksumlength;
850 out_err:
851 	if (ret && ret != GSS_S_BAD_SIG)
852 		ret = GSS_S_FAILURE;
853 	return ret;
854 }
855 
856 /**
857  * krb5_etm_checksum - Compute a MAC for a GSS Wrap token
858  * @cipher: an initialized cipher transform
859  * @tfm: an initialized hash transform
860  * @body: xdr_buf containing an RPC message (body.len is the message length)
861  * @body_offset: byte offset into @body to start checksumming
862  * @cksumout: OUT: a buffer to be filled in with the computed HMAC
863  *
864  * Usually expressed as H = HMAC(K, IV | ciphertext)[1..h] .
865  *
866  * Caller provides the truncation length of the output token (h) in
867  * cksumout.len.
868  *
869  * Return values:
870  *   %GSS_S_COMPLETE: Digest computed, @cksumout filled in
871  *   %GSS_S_FAILURE: Call failed
872  */
873 VISIBLE_IF_KUNIT
874 u32 krb5_etm_checksum(struct crypto_sync_skcipher *cipher,
875 		      struct crypto_ahash *tfm, const struct xdr_buf *body,
876 		      int body_offset, struct xdr_netobj *cksumout)
877 {
878 	unsigned int ivsize = crypto_sync_skcipher_ivsize(cipher);
879 	struct ahash_request *req;
880 	struct scatterlist sg[1];
881 	u8 *iv, *checksumdata;
882 	int err = -ENOMEM;
883 
884 	checksumdata = kmalloc(crypto_ahash_digestsize(tfm), GFP_KERNEL);
885 	if (!checksumdata)
886 		return GSS_S_FAILURE;
887 	/* For RPCSEC, the "initial cipher state" is always all zeroes. */
888 	iv = kzalloc(ivsize, GFP_KERNEL);
889 	if (!iv)
890 		goto out_free_mem;
891 
892 	req = ahash_request_alloc(tfm, GFP_KERNEL);
893 	if (!req)
894 		goto out_free_mem;
895 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
896 	err = crypto_ahash_init(req);
897 	if (err)
898 		goto out_free_ahash;
899 
900 	sg_init_one(sg, iv, ivsize);
901 	ahash_request_set_crypt(req, sg, NULL, ivsize);
902 	err = crypto_ahash_update(req);
903 	if (err)
904 		goto out_free_ahash;
905 	err = xdr_process_buf(body, body_offset, body->len - body_offset,
906 			      checksummer, req);
907 	if (err)
908 		goto out_free_ahash;
909 
910 	ahash_request_set_crypt(req, NULL, checksumdata, 0);
911 	err = crypto_ahash_final(req);
912 	if (err)
913 		goto out_free_ahash;
914 	memcpy(cksumout->data, checksumdata, cksumout->len);
915 
916 out_free_ahash:
917 	ahash_request_free(req);
918 out_free_mem:
919 	kfree(iv);
920 	kfree_sensitive(checksumdata);
921 	return err ? GSS_S_FAILURE : GSS_S_COMPLETE;
922 }
923 EXPORT_SYMBOL_IF_KUNIT(krb5_etm_checksum);
924 
925 /**
926  * krb5_etm_encrypt - Encrypt using the RFC 8009 rules
927  * @kctx: Kerberos context
928  * @offset: starting offset of the payload, in bytes
929  * @buf: OUT: send buffer to contain the encrypted payload
930  * @pages: plaintext payload
931  *
932  * The main difference with aes_encrypt is that "The HMAC is
933  * calculated over the cipher state concatenated with the AES
934  * output, instead of being calculated over the confounder and
935  * plaintext.  This allows the message receiver to verify the
936  * integrity of the message before decrypting the message."
937  *
938  * RFC 8009 Section 5:
939  *
940  * encryption function: as follows, where E() is AES encryption in
941  * CBC-CS3 mode, and h is the size of truncated HMAC (128 bits or
942  * 192 bits as described above).
943  *
944  *    N = random value of length 128 bits (the AES block size)
945  *    IV = cipher state
946  *    C = E(Ke, N | plaintext, IV)
947  *    H = HMAC(Ki, IV | C)
948  *    ciphertext = C | H[1..h]
949  *
950  * This encryption formula provides AEAD EtM with key separation.
951  *
952  * Return values:
953  *   %GSS_S_COMPLETE: Encryption successful
954  *   %GSS_S_FAILURE: Encryption failed
955  */
956 u32
957 krb5_etm_encrypt(struct krb5_ctx *kctx, u32 offset,
958 		 struct xdr_buf *buf, struct page **pages)
959 {
960 	struct crypto_sync_skcipher *cipher, *aux_cipher;
961 	struct crypto_ahash *ahash;
962 	struct xdr_netobj hmac;
963 	unsigned int conflen;
964 	u8 *ecptr;
965 	u32 err;
966 
967 	if (kctx->initiate) {
968 		cipher = kctx->initiator_enc;
969 		aux_cipher = kctx->initiator_enc_aux;
970 		ahash = kctx->initiator_integ;
971 	} else {
972 		cipher = kctx->acceptor_enc;
973 		aux_cipher = kctx->acceptor_enc_aux;
974 		ahash = kctx->acceptor_integ;
975 	}
976 	conflen = crypto_sync_skcipher_blocksize(cipher);
977 
978 	offset += GSS_KRB5_TOK_HDR_LEN;
979 	if (xdr_extend_head(buf, offset, conflen))
980 		return GSS_S_FAILURE;
981 	krb5_make_confounder(buf->head[0].iov_base + offset, conflen);
982 	offset -= GSS_KRB5_TOK_HDR_LEN;
983 
984 	if (buf->tail[0].iov_base) {
985 		ecptr = buf->tail[0].iov_base + buf->tail[0].iov_len;
986 	} else {
987 		buf->tail[0].iov_base = buf->head[0].iov_base
988 							+ buf->head[0].iov_len;
989 		buf->tail[0].iov_len = 0;
990 		ecptr = buf->tail[0].iov_base;
991 	}
992 
993 	memcpy(ecptr, buf->head[0].iov_base + offset, GSS_KRB5_TOK_HDR_LEN);
994 	buf->tail[0].iov_len += GSS_KRB5_TOK_HDR_LEN;
995 	buf->len += GSS_KRB5_TOK_HDR_LEN;
996 
997 	err = krb5_cbc_cts_encrypt(cipher, aux_cipher,
998 				   offset + GSS_KRB5_TOK_HDR_LEN,
999 				   buf, pages, NULL, 0);
1000 	if (err)
1001 		return GSS_S_FAILURE;
1002 
1003 	hmac.data = buf->tail[0].iov_base + buf->tail[0].iov_len;
1004 	hmac.len = kctx->gk5e->cksumlength;
1005 	err = krb5_etm_checksum(cipher, ahash,
1006 				buf, offset + GSS_KRB5_TOK_HDR_LEN, &hmac);
1007 	if (err)
1008 		goto out_err;
1009 	buf->tail[0].iov_len += kctx->gk5e->cksumlength;
1010 	buf->len += kctx->gk5e->cksumlength;
1011 
1012 	return GSS_S_COMPLETE;
1013 
1014 out_err:
1015 	return GSS_S_FAILURE;
1016 }
1017 
1018 /**
1019  * krb5_etm_decrypt - Decrypt using the RFC 8009 rules
1020  * @kctx: Kerberos context
1021  * @offset: starting offset of the ciphertext, in bytes
1022  * @len:
1023  * @buf:
1024  * @headskip: OUT: the enctype's confounder length, in octets
1025  * @tailskip: OUT: the enctype's HMAC length, in octets
1026  *
1027  * RFC 8009 Section 5:
1028  *
1029  * decryption function: as follows, where D() is AES decryption in
1030  * CBC-CS3 mode, and h is the size of truncated HMAC.
1031  *
1032  *    (C, H) = ciphertext
1033  *        (Note: H is the last h bits of the ciphertext.)
1034  *    IV = cipher state
1035  *    if H != HMAC(Ki, IV | C)[1..h]
1036  *        stop, report error
1037  *    (N, P) = D(Ke, C, IV)
1038  *
1039  * Return values:
1040  *   %GSS_S_COMPLETE: Decryption successful
1041  *   %GSS_S_BAD_SIG: computed HMAC != received HMAC
1042  *   %GSS_S_FAILURE: Decryption failed
1043  */
1044 u32
1045 krb5_etm_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len,
1046 		 struct xdr_buf *buf, u32 *headskip, u32 *tailskip)
1047 {
1048 	struct crypto_sync_skcipher *cipher, *aux_cipher;
1049 	u8 our_hmac[GSS_KRB5_MAX_CKSUM_LEN];
1050 	u8 pkt_hmac[GSS_KRB5_MAX_CKSUM_LEN];
1051 	struct xdr_netobj our_hmac_obj;
1052 	struct crypto_ahash *ahash;
1053 	struct xdr_buf subbuf;
1054 	u32 ret = 0;
1055 
1056 	if (kctx->initiate) {
1057 		cipher = kctx->acceptor_enc;
1058 		aux_cipher = kctx->acceptor_enc_aux;
1059 		ahash = kctx->acceptor_integ;
1060 	} else {
1061 		cipher = kctx->initiator_enc;
1062 		aux_cipher = kctx->initiator_enc_aux;
1063 		ahash = kctx->initiator_integ;
1064 	}
1065 
1066 	/* Extract the ciphertext into @subbuf. */
1067 	xdr_buf_subsegment(buf, &subbuf, offset + GSS_KRB5_TOK_HDR_LEN,
1068 			   (len - offset - GSS_KRB5_TOK_HDR_LEN -
1069 			    kctx->gk5e->cksumlength));
1070 
1071 	our_hmac_obj.data = our_hmac;
1072 	our_hmac_obj.len = kctx->gk5e->cksumlength;
1073 	ret = krb5_etm_checksum(cipher, ahash, &subbuf, 0, &our_hmac_obj);
1074 	if (ret)
1075 		goto out_err;
1076 	ret = read_bytes_from_xdr_buf(buf, len - kctx->gk5e->cksumlength,
1077 				      pkt_hmac, kctx->gk5e->cksumlength);
1078 	if (ret)
1079 		goto out_err;
1080 	if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
1081 		ret = GSS_S_BAD_SIG;
1082 		goto out_err;
1083 	}
1084 
1085 	ret = krb5_cbc_cts_decrypt(cipher, aux_cipher, 0, &subbuf);
1086 	if (ret) {
1087 		ret = GSS_S_FAILURE;
1088 		goto out_err;
1089 	}
1090 
1091 	*headskip = crypto_sync_skcipher_blocksize(cipher);
1092 	*tailskip = kctx->gk5e->cksumlength;
1093 	return GSS_S_COMPLETE;
1094 
1095 out_err:
1096 	if (ret != GSS_S_BAD_SIG)
1097 		ret = GSS_S_FAILURE;
1098 	return ret;
1099 }
1100