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/algapi.h>
38 #include <crypto/hash.h>
39 #include <crypto/skcipher.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 
50 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
51 # define RPCDBG_FACILITY        RPCDBG_AUTH
52 #endif
53 
54 u32
55 krb5_encrypt(
56 	struct crypto_sync_skcipher *tfm,
57 	void * iv,
58 	void * in,
59 	void * out,
60 	int length)
61 {
62 	u32 ret = -EINVAL;
63 	struct scatterlist sg[1];
64 	u8 local_iv[GSS_KRB5_MAX_BLOCKSIZE] = {0};
65 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
66 
67 	if (length % crypto_sync_skcipher_blocksize(tfm) != 0)
68 		goto out;
69 
70 	if (crypto_sync_skcipher_ivsize(tfm) > GSS_KRB5_MAX_BLOCKSIZE) {
71 		dprintk("RPC:       gss_k5encrypt: tfm iv size too large %d\n",
72 			crypto_sync_skcipher_ivsize(tfm));
73 		goto out;
74 	}
75 
76 	if (iv)
77 		memcpy(local_iv, iv, crypto_sync_skcipher_ivsize(tfm));
78 
79 	memcpy(out, in, length);
80 	sg_init_one(sg, out, length);
81 
82 	skcipher_request_set_sync_tfm(req, tfm);
83 	skcipher_request_set_callback(req, 0, NULL, NULL);
84 	skcipher_request_set_crypt(req, sg, sg, length, local_iv);
85 
86 	ret = crypto_skcipher_encrypt(req);
87 	skcipher_request_zero(req);
88 out:
89 	dprintk("RPC:       krb5_encrypt returns %d\n", ret);
90 	return ret;
91 }
92 
93 u32
94 krb5_decrypt(
95      struct crypto_sync_skcipher *tfm,
96      void * iv,
97      void * in,
98      void * out,
99      int length)
100 {
101 	u32 ret = -EINVAL;
102 	struct scatterlist sg[1];
103 	u8 local_iv[GSS_KRB5_MAX_BLOCKSIZE] = {0};
104 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
105 
106 	if (length % crypto_sync_skcipher_blocksize(tfm) != 0)
107 		goto out;
108 
109 	if (crypto_sync_skcipher_ivsize(tfm) > GSS_KRB5_MAX_BLOCKSIZE) {
110 		dprintk("RPC:       gss_k5decrypt: tfm iv size too large %d\n",
111 			crypto_sync_skcipher_ivsize(tfm));
112 		goto out;
113 	}
114 	if (iv)
115 		memcpy(local_iv, iv, crypto_sync_skcipher_ivsize(tfm));
116 
117 	memcpy(out, in, length);
118 	sg_init_one(sg, out, length);
119 
120 	skcipher_request_set_sync_tfm(req, tfm);
121 	skcipher_request_set_callback(req, 0, NULL, NULL);
122 	skcipher_request_set_crypt(req, sg, sg, length, local_iv);
123 
124 	ret = crypto_skcipher_decrypt(req);
125 	skcipher_request_zero(req);
126 out:
127 	dprintk("RPC:       gss_k5decrypt returns %d\n",ret);
128 	return ret;
129 }
130 
131 static int
132 checksummer(struct scatterlist *sg, void *data)
133 {
134 	struct ahash_request *req = data;
135 
136 	ahash_request_set_crypt(req, sg, NULL, sg->length);
137 
138 	return crypto_ahash_update(req);
139 }
140 
141 static int
142 arcfour_hmac_md5_usage_to_salt(unsigned int usage, u8 salt[4])
143 {
144 	unsigned int ms_usage;
145 
146 	switch (usage) {
147 	case KG_USAGE_SIGN:
148 		ms_usage = 15;
149 		break;
150 	case KG_USAGE_SEAL:
151 		ms_usage = 13;
152 		break;
153 	default:
154 		return -EINVAL;
155 	}
156 	salt[0] = (ms_usage >> 0) & 0xff;
157 	salt[1] = (ms_usage >> 8) & 0xff;
158 	salt[2] = (ms_usage >> 16) & 0xff;
159 	salt[3] = (ms_usage >> 24) & 0xff;
160 
161 	return 0;
162 }
163 
164 static u32
165 make_checksum_hmac_md5(struct krb5_ctx *kctx, char *header, int hdrlen,
166 		       struct xdr_buf *body, int body_offset, u8 *cksumkey,
167 		       unsigned int usage, struct xdr_netobj *cksumout)
168 {
169 	struct scatterlist              sg[1];
170 	int err = -1;
171 	u8 *checksumdata;
172 	u8 *rc4salt;
173 	struct crypto_ahash *md5;
174 	struct crypto_ahash *hmac_md5;
175 	struct ahash_request *req;
176 
177 	if (cksumkey == NULL)
178 		return GSS_S_FAILURE;
179 
180 	if (cksumout->len < kctx->gk5e->cksumlength) {
181 		dprintk("%s: checksum buffer length, %u, too small for %s\n",
182 			__func__, cksumout->len, kctx->gk5e->name);
183 		return GSS_S_FAILURE;
184 	}
185 
186 	rc4salt = kmalloc_array(4, sizeof(*rc4salt), GFP_NOFS);
187 	if (!rc4salt)
188 		return GSS_S_FAILURE;
189 
190 	if (arcfour_hmac_md5_usage_to_salt(usage, rc4salt)) {
191 		dprintk("%s: invalid usage value %u\n", __func__, usage);
192 		goto out_free_rc4salt;
193 	}
194 
195 	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
196 	if (!checksumdata)
197 		goto out_free_rc4salt;
198 
199 	md5 = crypto_alloc_ahash("md5", 0, CRYPTO_ALG_ASYNC);
200 	if (IS_ERR(md5))
201 		goto out_free_cksum;
202 
203 	hmac_md5 = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0,
204 				      CRYPTO_ALG_ASYNC);
205 	if (IS_ERR(hmac_md5))
206 		goto out_free_md5;
207 
208 	req = ahash_request_alloc(md5, GFP_NOFS);
209 	if (!req)
210 		goto out_free_hmac_md5;
211 
212 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
213 
214 	err = crypto_ahash_init(req);
215 	if (err)
216 		goto out;
217 	sg_init_one(sg, rc4salt, 4);
218 	ahash_request_set_crypt(req, sg, NULL, 4);
219 	err = crypto_ahash_update(req);
220 	if (err)
221 		goto out;
222 
223 	sg_init_one(sg, header, hdrlen);
224 	ahash_request_set_crypt(req, sg, NULL, hdrlen);
225 	err = crypto_ahash_update(req);
226 	if (err)
227 		goto out;
228 	err = xdr_process_buf(body, body_offset, body->len - body_offset,
229 			      checksummer, req);
230 	if (err)
231 		goto out;
232 	ahash_request_set_crypt(req, NULL, checksumdata, 0);
233 	err = crypto_ahash_final(req);
234 	if (err)
235 		goto out;
236 
237 	ahash_request_free(req);
238 	req = ahash_request_alloc(hmac_md5, GFP_NOFS);
239 	if (!req)
240 		goto out_free_hmac_md5;
241 
242 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
243 
244 	err = crypto_ahash_setkey(hmac_md5, cksumkey, kctx->gk5e->keylength);
245 	if (err)
246 		goto out;
247 
248 	sg_init_one(sg, checksumdata, crypto_ahash_digestsize(md5));
249 	ahash_request_set_crypt(req, sg, checksumdata,
250 				crypto_ahash_digestsize(md5));
251 	err = crypto_ahash_digest(req);
252 	if (err)
253 		goto out;
254 
255 	memcpy(cksumout->data, checksumdata, kctx->gk5e->cksumlength);
256 	cksumout->len = kctx->gk5e->cksumlength;
257 out:
258 	ahash_request_free(req);
259 out_free_hmac_md5:
260 	crypto_free_ahash(hmac_md5);
261 out_free_md5:
262 	crypto_free_ahash(md5);
263 out_free_cksum:
264 	kfree(checksumdata);
265 out_free_rc4salt:
266 	kfree(rc4salt);
267 	return err ? GSS_S_FAILURE : 0;
268 }
269 
270 /*
271  * checksum the plaintext data and hdrlen bytes of the token header
272  * The checksum is performed over the first 8 bytes of the
273  * gss token header and then over the data body
274  */
275 u32
276 make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
277 	      struct xdr_buf *body, int body_offset, u8 *cksumkey,
278 	      unsigned int usage, struct xdr_netobj *cksumout)
279 {
280 	struct crypto_ahash *tfm;
281 	struct ahash_request *req;
282 	struct scatterlist              sg[1];
283 	int err = -1;
284 	u8 *checksumdata;
285 	unsigned int checksumlen;
286 
287 	if (kctx->gk5e->ctype == CKSUMTYPE_HMAC_MD5_ARCFOUR)
288 		return make_checksum_hmac_md5(kctx, header, hdrlen,
289 					      body, body_offset,
290 					      cksumkey, usage, cksumout);
291 
292 	if (cksumout->len < kctx->gk5e->cksumlength) {
293 		dprintk("%s: checksum buffer length, %u, too small for %s\n",
294 			__func__, cksumout->len, kctx->gk5e->name);
295 		return GSS_S_FAILURE;
296 	}
297 
298 	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
299 	if (checksumdata == NULL)
300 		return GSS_S_FAILURE;
301 
302 	tfm = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
303 	if (IS_ERR(tfm))
304 		goto out_free_cksum;
305 
306 	req = ahash_request_alloc(tfm, GFP_NOFS);
307 	if (!req)
308 		goto out_free_ahash;
309 
310 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
311 
312 	checksumlen = crypto_ahash_digestsize(tfm);
313 
314 	if (cksumkey != NULL) {
315 		err = crypto_ahash_setkey(tfm, cksumkey,
316 					  kctx->gk5e->keylength);
317 		if (err)
318 			goto out;
319 	}
320 
321 	err = crypto_ahash_init(req);
322 	if (err)
323 		goto out;
324 	sg_init_one(sg, header, hdrlen);
325 	ahash_request_set_crypt(req, sg, NULL, hdrlen);
326 	err = crypto_ahash_update(req);
327 	if (err)
328 		goto out;
329 	err = xdr_process_buf(body, body_offset, body->len - body_offset,
330 			      checksummer, req);
331 	if (err)
332 		goto out;
333 	ahash_request_set_crypt(req, NULL, checksumdata, 0);
334 	err = crypto_ahash_final(req);
335 	if (err)
336 		goto out;
337 
338 	switch (kctx->gk5e->ctype) {
339 	case CKSUMTYPE_RSA_MD5:
340 		err = kctx->gk5e->encrypt(kctx->seq, NULL, checksumdata,
341 					  checksumdata, checksumlen);
342 		if (err)
343 			goto out;
344 		memcpy(cksumout->data,
345 		       checksumdata + checksumlen - kctx->gk5e->cksumlength,
346 		       kctx->gk5e->cksumlength);
347 		break;
348 	case CKSUMTYPE_HMAC_SHA1_DES3:
349 		memcpy(cksumout->data, checksumdata, kctx->gk5e->cksumlength);
350 		break;
351 	default:
352 		BUG();
353 		break;
354 	}
355 	cksumout->len = kctx->gk5e->cksumlength;
356 out:
357 	ahash_request_free(req);
358 out_free_ahash:
359 	crypto_free_ahash(tfm);
360 out_free_cksum:
361 	kfree(checksumdata);
362 	return err ? GSS_S_FAILURE : 0;
363 }
364 
365 /*
366  * checksum the plaintext data and hdrlen bytes of the token header
367  * Per rfc4121, sec. 4.2.4, the checksum is performed over the data
368  * body then over the first 16 octets of the MIC token
369  * Inclusion of the header data in the calculation of the
370  * checksum is optional.
371  */
372 u32
373 make_checksum_v2(struct krb5_ctx *kctx, char *header, int hdrlen,
374 		 struct xdr_buf *body, int body_offset, u8 *cksumkey,
375 		 unsigned int usage, struct xdr_netobj *cksumout)
376 {
377 	struct crypto_ahash *tfm;
378 	struct ahash_request *req;
379 	struct scatterlist sg[1];
380 	int err = -1;
381 	u8 *checksumdata;
382 
383 	if (kctx->gk5e->keyed_cksum == 0) {
384 		dprintk("%s: expected keyed hash for %s\n",
385 			__func__, kctx->gk5e->name);
386 		return GSS_S_FAILURE;
387 	}
388 	if (cksumkey == NULL) {
389 		dprintk("%s: no key supplied for %s\n",
390 			__func__, kctx->gk5e->name);
391 		return GSS_S_FAILURE;
392 	}
393 
394 	checksumdata = kmalloc(GSS_KRB5_MAX_CKSUM_LEN, GFP_NOFS);
395 	if (!checksumdata)
396 		return GSS_S_FAILURE;
397 
398 	tfm = crypto_alloc_ahash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
399 	if (IS_ERR(tfm))
400 		goto out_free_cksum;
401 
402 	req = ahash_request_alloc(tfm, GFP_NOFS);
403 	if (!req)
404 		goto out_free_ahash;
405 
406 	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
407 
408 	err = crypto_ahash_setkey(tfm, cksumkey, kctx->gk5e->keylength);
409 	if (err)
410 		goto out;
411 
412 	err = crypto_ahash_init(req);
413 	if (err)
414 		goto out;
415 	err = xdr_process_buf(body, body_offset, body->len - body_offset,
416 			      checksummer, req);
417 	if (err)
418 		goto out;
419 	if (header != NULL) {
420 		sg_init_one(sg, header, hdrlen);
421 		ahash_request_set_crypt(req, sg, NULL, hdrlen);
422 		err = crypto_ahash_update(req);
423 		if (err)
424 			goto out;
425 	}
426 	ahash_request_set_crypt(req, NULL, checksumdata, 0);
427 	err = crypto_ahash_final(req);
428 	if (err)
429 		goto out;
430 
431 	cksumout->len = kctx->gk5e->cksumlength;
432 
433 	switch (kctx->gk5e->ctype) {
434 	case CKSUMTYPE_HMAC_SHA1_96_AES128:
435 	case CKSUMTYPE_HMAC_SHA1_96_AES256:
436 		/* note that this truncates the hash */
437 		memcpy(cksumout->data, checksumdata, kctx->gk5e->cksumlength);
438 		break;
439 	default:
440 		BUG();
441 		break;
442 	}
443 out:
444 	ahash_request_free(req);
445 out_free_ahash:
446 	crypto_free_ahash(tfm);
447 out_free_cksum:
448 	kfree(checksumdata);
449 	return err ? GSS_S_FAILURE : 0;
450 }
451 
452 struct encryptor_desc {
453 	u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
454 	struct skcipher_request *req;
455 	int pos;
456 	struct xdr_buf *outbuf;
457 	struct page **pages;
458 	struct scatterlist infrags[4];
459 	struct scatterlist outfrags[4];
460 	int fragno;
461 	int fraglen;
462 };
463 
464 static int
465 encryptor(struct scatterlist *sg, void *data)
466 {
467 	struct encryptor_desc *desc = data;
468 	struct xdr_buf *outbuf = desc->outbuf;
469 	struct crypto_sync_skcipher *tfm =
470 		crypto_sync_skcipher_reqtfm(desc->req);
471 	struct page *in_page;
472 	int thislen = desc->fraglen + sg->length;
473 	int fraglen, ret;
474 	int page_pos;
475 
476 	/* Worst case is 4 fragments: head, end of page 1, start
477 	 * of page 2, tail.  Anything more is a bug. */
478 	BUG_ON(desc->fragno > 3);
479 
480 	page_pos = desc->pos - outbuf->head[0].iov_len;
481 	if (page_pos >= 0 && page_pos < outbuf->page_len) {
482 		/* pages are not in place: */
483 		int i = (page_pos + outbuf->page_base) >> PAGE_SHIFT;
484 		in_page = desc->pages[i];
485 	} else {
486 		in_page = sg_page(sg);
487 	}
488 	sg_set_page(&desc->infrags[desc->fragno], in_page, sg->length,
489 		    sg->offset);
490 	sg_set_page(&desc->outfrags[desc->fragno], sg_page(sg), sg->length,
491 		    sg->offset);
492 	desc->fragno++;
493 	desc->fraglen += sg->length;
494 	desc->pos += sg->length;
495 
496 	fraglen = thislen & (crypto_sync_skcipher_blocksize(tfm) - 1);
497 	thislen -= fraglen;
498 
499 	if (thislen == 0)
500 		return 0;
501 
502 	sg_mark_end(&desc->infrags[desc->fragno - 1]);
503 	sg_mark_end(&desc->outfrags[desc->fragno - 1]);
504 
505 	skcipher_request_set_crypt(desc->req, desc->infrags, desc->outfrags,
506 				   thislen, desc->iv);
507 
508 	ret = crypto_skcipher_encrypt(desc->req);
509 	if (ret)
510 		return ret;
511 
512 	sg_init_table(desc->infrags, 4);
513 	sg_init_table(desc->outfrags, 4);
514 
515 	if (fraglen) {
516 		sg_set_page(&desc->outfrags[0], sg_page(sg), fraglen,
517 				sg->offset + sg->length - fraglen);
518 		desc->infrags[0] = desc->outfrags[0];
519 		sg_assign_page(&desc->infrags[0], in_page);
520 		desc->fragno = 1;
521 		desc->fraglen = fraglen;
522 	} else {
523 		desc->fragno = 0;
524 		desc->fraglen = 0;
525 	}
526 	return 0;
527 }
528 
529 int
530 gss_encrypt_xdr_buf(struct crypto_sync_skcipher *tfm, struct xdr_buf *buf,
531 		    int offset, struct page **pages)
532 {
533 	int ret;
534 	struct encryptor_desc desc;
535 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
536 
537 	BUG_ON((buf->len - offset) % crypto_sync_skcipher_blocksize(tfm) != 0);
538 
539 	skcipher_request_set_sync_tfm(req, tfm);
540 	skcipher_request_set_callback(req, 0, NULL, NULL);
541 
542 	memset(desc.iv, 0, sizeof(desc.iv));
543 	desc.req = req;
544 	desc.pos = offset;
545 	desc.outbuf = buf;
546 	desc.pages = pages;
547 	desc.fragno = 0;
548 	desc.fraglen = 0;
549 
550 	sg_init_table(desc.infrags, 4);
551 	sg_init_table(desc.outfrags, 4);
552 
553 	ret = xdr_process_buf(buf, offset, buf->len - offset, encryptor, &desc);
554 	skcipher_request_zero(req);
555 	return ret;
556 }
557 
558 struct decryptor_desc {
559 	u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
560 	struct skcipher_request *req;
561 	struct scatterlist frags[4];
562 	int fragno;
563 	int fraglen;
564 };
565 
566 static int
567 decryptor(struct scatterlist *sg, void *data)
568 {
569 	struct decryptor_desc *desc = data;
570 	int thislen = desc->fraglen + sg->length;
571 	struct crypto_sync_skcipher *tfm =
572 		crypto_sync_skcipher_reqtfm(desc->req);
573 	int fraglen, ret;
574 
575 	/* Worst case is 4 fragments: head, end of page 1, start
576 	 * of page 2, tail.  Anything more is a bug. */
577 	BUG_ON(desc->fragno > 3);
578 	sg_set_page(&desc->frags[desc->fragno], sg_page(sg), sg->length,
579 		    sg->offset);
580 	desc->fragno++;
581 	desc->fraglen += sg->length;
582 
583 	fraglen = thislen & (crypto_sync_skcipher_blocksize(tfm) - 1);
584 	thislen -= fraglen;
585 
586 	if (thislen == 0)
587 		return 0;
588 
589 	sg_mark_end(&desc->frags[desc->fragno - 1]);
590 
591 	skcipher_request_set_crypt(desc->req, desc->frags, desc->frags,
592 				   thislen, desc->iv);
593 
594 	ret = crypto_skcipher_decrypt(desc->req);
595 	if (ret)
596 		return ret;
597 
598 	sg_init_table(desc->frags, 4);
599 
600 	if (fraglen) {
601 		sg_set_page(&desc->frags[0], sg_page(sg), fraglen,
602 				sg->offset + sg->length - fraglen);
603 		desc->fragno = 1;
604 		desc->fraglen = fraglen;
605 	} else {
606 		desc->fragno = 0;
607 		desc->fraglen = 0;
608 	}
609 	return 0;
610 }
611 
612 int
613 gss_decrypt_xdr_buf(struct crypto_sync_skcipher *tfm, struct xdr_buf *buf,
614 		    int offset)
615 {
616 	int ret;
617 	struct decryptor_desc desc;
618 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm);
619 
620 	/* XXXJBF: */
621 	BUG_ON((buf->len - offset) % crypto_sync_skcipher_blocksize(tfm) != 0);
622 
623 	skcipher_request_set_sync_tfm(req, tfm);
624 	skcipher_request_set_callback(req, 0, NULL, NULL);
625 
626 	memset(desc.iv, 0, sizeof(desc.iv));
627 	desc.req = req;
628 	desc.fragno = 0;
629 	desc.fraglen = 0;
630 
631 	sg_init_table(desc.frags, 4);
632 
633 	ret = xdr_process_buf(buf, offset, buf->len - offset, decryptor, &desc);
634 	skcipher_request_zero(req);
635 	return ret;
636 }
637 
638 /*
639  * This function makes the assumption that it was ultimately called
640  * from gss_wrap().
641  *
642  * The client auth_gss code moves any existing tail data into a
643  * separate page before calling gss_wrap.
644  * The server svcauth_gss code ensures that both the head and the
645  * tail have slack space of RPC_MAX_AUTH_SIZE before calling gss_wrap.
646  *
647  * Even with that guarantee, this function may be called more than
648  * once in the processing of gss_wrap().  The best we can do is
649  * verify at compile-time (see GSS_KRB5_SLACK_CHECK) that the
650  * largest expected shift will fit within RPC_MAX_AUTH_SIZE.
651  * At run-time we can verify that a single invocation of this
652  * function doesn't attempt to use more the RPC_MAX_AUTH_SIZE.
653  */
654 
655 int
656 xdr_extend_head(struct xdr_buf *buf, unsigned int base, unsigned int shiftlen)
657 {
658 	u8 *p;
659 
660 	if (shiftlen == 0)
661 		return 0;
662 
663 	BUILD_BUG_ON(GSS_KRB5_MAX_SLACK_NEEDED > RPC_MAX_AUTH_SIZE);
664 	BUG_ON(shiftlen > RPC_MAX_AUTH_SIZE);
665 
666 	p = buf->head[0].iov_base + base;
667 
668 	memmove(p + shiftlen, p, buf->head[0].iov_len - base);
669 
670 	buf->head[0].iov_len += shiftlen;
671 	buf->len += shiftlen;
672 
673 	return 0;
674 }
675 
676 static u32
677 gss_krb5_cts_crypt(struct crypto_sync_skcipher *cipher, struct xdr_buf *buf,
678 		   u32 offset, u8 *iv, struct page **pages, int encrypt)
679 {
680 	u32 ret;
681 	struct scatterlist sg[1];
682 	SYNC_SKCIPHER_REQUEST_ON_STACK(req, cipher);
683 	u8 *data;
684 	struct page **save_pages;
685 	u32 len = buf->len - offset;
686 
687 	if (len > GSS_KRB5_MAX_BLOCKSIZE * 2) {
688 		WARN_ON(0);
689 		return -ENOMEM;
690 	}
691 	data = kmalloc(GSS_KRB5_MAX_BLOCKSIZE * 2, GFP_NOFS);
692 	if (!data)
693 		return -ENOMEM;
694 
695 	/*
696 	 * For encryption, we want to read from the cleartext
697 	 * page cache pages, and write the encrypted data to
698 	 * the supplied xdr_buf pages.
699 	 */
700 	save_pages = buf->pages;
701 	if (encrypt)
702 		buf->pages = pages;
703 
704 	ret = read_bytes_from_xdr_buf(buf, offset, data, len);
705 	buf->pages = save_pages;
706 	if (ret)
707 		goto out;
708 
709 	sg_init_one(sg, data, len);
710 
711 	skcipher_request_set_sync_tfm(req, cipher);
712 	skcipher_request_set_callback(req, 0, NULL, NULL);
713 	skcipher_request_set_crypt(req, sg, sg, len, iv);
714 
715 	if (encrypt)
716 		ret = crypto_skcipher_encrypt(req);
717 	else
718 		ret = crypto_skcipher_decrypt(req);
719 
720 	skcipher_request_zero(req);
721 
722 	if (ret)
723 		goto out;
724 
725 	ret = write_bytes_to_xdr_buf(buf, offset, data, len);
726 
727 out:
728 	kfree(data);
729 	return ret;
730 }
731 
732 u32
733 gss_krb5_aes_encrypt(struct krb5_ctx *kctx, u32 offset,
734 		     struct xdr_buf *buf, struct page **pages)
735 {
736 	u32 err;
737 	struct xdr_netobj hmac;
738 	u8 *cksumkey;
739 	u8 *ecptr;
740 	struct crypto_sync_skcipher *cipher, *aux_cipher;
741 	int blocksize;
742 	struct page **save_pages;
743 	int nblocks, nbytes;
744 	struct encryptor_desc desc;
745 	u32 cbcbytes;
746 	unsigned int usage;
747 
748 	if (kctx->initiate) {
749 		cipher = kctx->initiator_enc;
750 		aux_cipher = kctx->initiator_enc_aux;
751 		cksumkey = kctx->initiator_integ;
752 		usage = KG_USAGE_INITIATOR_SEAL;
753 	} else {
754 		cipher = kctx->acceptor_enc;
755 		aux_cipher = kctx->acceptor_enc_aux;
756 		cksumkey = kctx->acceptor_integ;
757 		usage = KG_USAGE_ACCEPTOR_SEAL;
758 	}
759 	blocksize = crypto_sync_skcipher_blocksize(cipher);
760 
761 	/* hide the gss token header and insert the confounder */
762 	offset += GSS_KRB5_TOK_HDR_LEN;
763 	if (xdr_extend_head(buf, offset, kctx->gk5e->conflen))
764 		return GSS_S_FAILURE;
765 	gss_krb5_make_confounder(buf->head[0].iov_base + offset, kctx->gk5e->conflen);
766 	offset -= GSS_KRB5_TOK_HDR_LEN;
767 
768 	if (buf->tail[0].iov_base != NULL) {
769 		ecptr = buf->tail[0].iov_base + buf->tail[0].iov_len;
770 	} else {
771 		buf->tail[0].iov_base = buf->head[0].iov_base
772 							+ buf->head[0].iov_len;
773 		buf->tail[0].iov_len = 0;
774 		ecptr = buf->tail[0].iov_base;
775 	}
776 
777 	/* copy plaintext gss token header after filler (if any) */
778 	memcpy(ecptr, buf->head[0].iov_base + offset, GSS_KRB5_TOK_HDR_LEN);
779 	buf->tail[0].iov_len += GSS_KRB5_TOK_HDR_LEN;
780 	buf->len += GSS_KRB5_TOK_HDR_LEN;
781 
782 	/* Do the HMAC */
783 	hmac.len = GSS_KRB5_MAX_CKSUM_LEN;
784 	hmac.data = buf->tail[0].iov_base + buf->tail[0].iov_len;
785 
786 	/*
787 	 * When we are called, pages points to the real page cache
788 	 * data -- which we can't go and encrypt!  buf->pages points
789 	 * to scratch pages which we are going to send off to the
790 	 * client/server.  Swap in the plaintext pages to calculate
791 	 * the hmac.
792 	 */
793 	save_pages = buf->pages;
794 	buf->pages = pages;
795 
796 	err = make_checksum_v2(kctx, NULL, 0, buf,
797 			       offset + GSS_KRB5_TOK_HDR_LEN,
798 			       cksumkey, usage, &hmac);
799 	buf->pages = save_pages;
800 	if (err)
801 		return GSS_S_FAILURE;
802 
803 	nbytes = buf->len - offset - GSS_KRB5_TOK_HDR_LEN;
804 	nblocks = (nbytes + blocksize - 1) / blocksize;
805 	cbcbytes = 0;
806 	if (nblocks > 2)
807 		cbcbytes = (nblocks - 2) * blocksize;
808 
809 	memset(desc.iv, 0, sizeof(desc.iv));
810 
811 	if (cbcbytes) {
812 		SYNC_SKCIPHER_REQUEST_ON_STACK(req, aux_cipher);
813 
814 		desc.pos = offset + GSS_KRB5_TOK_HDR_LEN;
815 		desc.fragno = 0;
816 		desc.fraglen = 0;
817 		desc.pages = pages;
818 		desc.outbuf = buf;
819 		desc.req = req;
820 
821 		skcipher_request_set_sync_tfm(req, aux_cipher);
822 		skcipher_request_set_callback(req, 0, NULL, NULL);
823 
824 		sg_init_table(desc.infrags, 4);
825 		sg_init_table(desc.outfrags, 4);
826 
827 		err = xdr_process_buf(buf, offset + GSS_KRB5_TOK_HDR_LEN,
828 				      cbcbytes, encryptor, &desc);
829 		skcipher_request_zero(req);
830 		if (err)
831 			goto out_err;
832 	}
833 
834 	/* Make sure IV carries forward from any CBC results. */
835 	err = gss_krb5_cts_crypt(cipher, buf,
836 				 offset + GSS_KRB5_TOK_HDR_LEN + cbcbytes,
837 				 desc.iv, pages, 1);
838 	if (err) {
839 		err = GSS_S_FAILURE;
840 		goto out_err;
841 	}
842 
843 	/* Now update buf to account for HMAC */
844 	buf->tail[0].iov_len += kctx->gk5e->cksumlength;
845 	buf->len += kctx->gk5e->cksumlength;
846 
847 out_err:
848 	if (err)
849 		err = GSS_S_FAILURE;
850 	return err;
851 }
852 
853 u32
854 gss_krb5_aes_decrypt(struct krb5_ctx *kctx, u32 offset, struct xdr_buf *buf,
855 		     u32 *headskip, u32 *tailskip)
856 {
857 	struct xdr_buf subbuf;
858 	u32 ret = 0;
859 	u8 *cksum_key;
860 	struct crypto_sync_skcipher *cipher, *aux_cipher;
861 	struct xdr_netobj our_hmac_obj;
862 	u8 our_hmac[GSS_KRB5_MAX_CKSUM_LEN];
863 	u8 pkt_hmac[GSS_KRB5_MAX_CKSUM_LEN];
864 	int nblocks, blocksize, cbcbytes;
865 	struct decryptor_desc desc;
866 	unsigned int usage;
867 
868 	if (kctx->initiate) {
869 		cipher = kctx->acceptor_enc;
870 		aux_cipher = kctx->acceptor_enc_aux;
871 		cksum_key = kctx->acceptor_integ;
872 		usage = KG_USAGE_ACCEPTOR_SEAL;
873 	} else {
874 		cipher = kctx->initiator_enc;
875 		aux_cipher = kctx->initiator_enc_aux;
876 		cksum_key = kctx->initiator_integ;
877 		usage = KG_USAGE_INITIATOR_SEAL;
878 	}
879 	blocksize = crypto_sync_skcipher_blocksize(cipher);
880 
881 
882 	/* create a segment skipping the header and leaving out the checksum */
883 	xdr_buf_subsegment(buf, &subbuf, offset + GSS_KRB5_TOK_HDR_LEN,
884 				    (buf->len - offset - GSS_KRB5_TOK_HDR_LEN -
885 				     kctx->gk5e->cksumlength));
886 
887 	nblocks = (subbuf.len + blocksize - 1) / blocksize;
888 
889 	cbcbytes = 0;
890 	if (nblocks > 2)
891 		cbcbytes = (nblocks - 2) * blocksize;
892 
893 	memset(desc.iv, 0, sizeof(desc.iv));
894 
895 	if (cbcbytes) {
896 		SYNC_SKCIPHER_REQUEST_ON_STACK(req, aux_cipher);
897 
898 		desc.fragno = 0;
899 		desc.fraglen = 0;
900 		desc.req = req;
901 
902 		skcipher_request_set_sync_tfm(req, aux_cipher);
903 		skcipher_request_set_callback(req, 0, NULL, NULL);
904 
905 		sg_init_table(desc.frags, 4);
906 
907 		ret = xdr_process_buf(&subbuf, 0, cbcbytes, decryptor, &desc);
908 		skcipher_request_zero(req);
909 		if (ret)
910 			goto out_err;
911 	}
912 
913 	/* Make sure IV carries forward from any CBC results. */
914 	ret = gss_krb5_cts_crypt(cipher, &subbuf, cbcbytes, desc.iv, NULL, 0);
915 	if (ret)
916 		goto out_err;
917 
918 
919 	/* Calculate our hmac over the plaintext data */
920 	our_hmac_obj.len = sizeof(our_hmac);
921 	our_hmac_obj.data = our_hmac;
922 
923 	ret = make_checksum_v2(kctx, NULL, 0, &subbuf, 0,
924 			       cksum_key, usage, &our_hmac_obj);
925 	if (ret)
926 		goto out_err;
927 
928 	/* Get the packet's hmac value */
929 	ret = read_bytes_from_xdr_buf(buf, buf->len - kctx->gk5e->cksumlength,
930 				      pkt_hmac, kctx->gk5e->cksumlength);
931 	if (ret)
932 		goto out_err;
933 
934 	if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
935 		ret = GSS_S_BAD_SIG;
936 		goto out_err;
937 	}
938 	*headskip = kctx->gk5e->conflen;
939 	*tailskip = kctx->gk5e->cksumlength;
940 out_err:
941 	if (ret && ret != GSS_S_BAD_SIG)
942 		ret = GSS_S_FAILURE;
943 	return ret;
944 }
945 
946 /*
947  * Compute Kseq given the initial session key and the checksum.
948  * Set the key of the given cipher.
949  */
950 int
951 krb5_rc4_setup_seq_key(struct krb5_ctx *kctx,
952 		       struct crypto_sync_skcipher *cipher,
953 		       unsigned char *cksum)
954 {
955 	struct crypto_shash *hmac;
956 	struct shash_desc *desc;
957 	u8 Kseq[GSS_KRB5_MAX_KEYLEN];
958 	u32 zeroconstant = 0;
959 	int err;
960 
961 	dprintk("%s: entered\n", __func__);
962 
963 	hmac = crypto_alloc_shash(kctx->gk5e->cksum_name, 0, 0);
964 	if (IS_ERR(hmac)) {
965 		dprintk("%s: error %ld, allocating hash '%s'\n",
966 			__func__, PTR_ERR(hmac), kctx->gk5e->cksum_name);
967 		return PTR_ERR(hmac);
968 	}
969 
970 	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac),
971 		       GFP_NOFS);
972 	if (!desc) {
973 		dprintk("%s: failed to allocate shash descriptor for '%s'\n",
974 			__func__, kctx->gk5e->cksum_name);
975 		crypto_free_shash(hmac);
976 		return -ENOMEM;
977 	}
978 
979 	desc->tfm = hmac;
980 	desc->flags = 0;
981 
982 	/* Compute intermediate Kseq from session key */
983 	err = crypto_shash_setkey(hmac, kctx->Ksess, kctx->gk5e->keylength);
984 	if (err)
985 		goto out_err;
986 
987 	err = crypto_shash_digest(desc, (u8 *)&zeroconstant, 4, Kseq);
988 	if (err)
989 		goto out_err;
990 
991 	/* Compute final Kseq from the checksum and intermediate Kseq */
992 	err = crypto_shash_setkey(hmac, Kseq, kctx->gk5e->keylength);
993 	if (err)
994 		goto out_err;
995 
996 	err = crypto_shash_digest(desc, cksum, 8, Kseq);
997 	if (err)
998 		goto out_err;
999 
1000 	err = crypto_sync_skcipher_setkey(cipher, Kseq, kctx->gk5e->keylength);
1001 	if (err)
1002 		goto out_err;
1003 
1004 	err = 0;
1005 
1006 out_err:
1007 	kzfree(desc);
1008 	crypto_free_shash(hmac);
1009 	dprintk("%s: returning %d\n", __func__, err);
1010 	return err;
1011 }
1012 
1013 /*
1014  * Compute Kcrypt given the initial session key and the plaintext seqnum.
1015  * Set the key of cipher kctx->enc.
1016  */
1017 int
1018 krb5_rc4_setup_enc_key(struct krb5_ctx *kctx,
1019 		       struct crypto_sync_skcipher *cipher,
1020 		       s32 seqnum)
1021 {
1022 	struct crypto_shash *hmac;
1023 	struct shash_desc *desc;
1024 	u8 Kcrypt[GSS_KRB5_MAX_KEYLEN];
1025 	u8 zeroconstant[4] = {0};
1026 	u8 seqnumarray[4];
1027 	int err, i;
1028 
1029 	dprintk("%s: entered, seqnum %u\n", __func__, seqnum);
1030 
1031 	hmac = crypto_alloc_shash(kctx->gk5e->cksum_name, 0, 0);
1032 	if (IS_ERR(hmac)) {
1033 		dprintk("%s: error %ld, allocating hash '%s'\n",
1034 			__func__, PTR_ERR(hmac), kctx->gk5e->cksum_name);
1035 		return PTR_ERR(hmac);
1036 	}
1037 
1038 	desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(hmac),
1039 		       GFP_NOFS);
1040 	if (!desc) {
1041 		dprintk("%s: failed to allocate shash descriptor for '%s'\n",
1042 			__func__, kctx->gk5e->cksum_name);
1043 		crypto_free_shash(hmac);
1044 		return -ENOMEM;
1045 	}
1046 
1047 	desc->tfm = hmac;
1048 	desc->flags = 0;
1049 
1050 	/* Compute intermediate Kcrypt from session key */
1051 	for (i = 0; i < kctx->gk5e->keylength; i++)
1052 		Kcrypt[i] = kctx->Ksess[i] ^ 0xf0;
1053 
1054 	err = crypto_shash_setkey(hmac, Kcrypt, kctx->gk5e->keylength);
1055 	if (err)
1056 		goto out_err;
1057 
1058 	err = crypto_shash_digest(desc, zeroconstant, 4, Kcrypt);
1059 	if (err)
1060 		goto out_err;
1061 
1062 	/* Compute final Kcrypt from the seqnum and intermediate Kcrypt */
1063 	err = crypto_shash_setkey(hmac, Kcrypt, kctx->gk5e->keylength);
1064 	if (err)
1065 		goto out_err;
1066 
1067 	seqnumarray[0] = (unsigned char) ((seqnum >> 24) & 0xff);
1068 	seqnumarray[1] = (unsigned char) ((seqnum >> 16) & 0xff);
1069 	seqnumarray[2] = (unsigned char) ((seqnum >> 8) & 0xff);
1070 	seqnumarray[3] = (unsigned char) ((seqnum >> 0) & 0xff);
1071 
1072 	err = crypto_shash_digest(desc, seqnumarray, 4, Kcrypt);
1073 	if (err)
1074 		goto out_err;
1075 
1076 	err = crypto_sync_skcipher_setkey(cipher, Kcrypt,
1077 					  kctx->gk5e->keylength);
1078 	if (err)
1079 		goto out_err;
1080 
1081 	err = 0;
1082 
1083 out_err:
1084 	kzfree(desc);
1085 	crypto_free_shash(hmac);
1086 	dprintk("%s: returning %d\n", __func__, err);
1087 	return err;
1088 }
1089