gss_krb5_crypto.c

  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 */
 81void 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 */
102u32
103krb5_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);
136out:
137	dprintk("RPC:       krb5_encrypt returns %d\n", ret);
138	return ret;
139}
140
141static int
142checksummer(struct scatterlist *sg, void *data)
143{
144	struct ahash_request *req = data;
145
146	ahash_request_set_crypt(req, sg, NULL, sg->length);
147
148	return crypto_ahash_update(req);
149}
150
151/**
152 * gss_krb5_checksum - Compute the MAC for a GSS Wrap or MIC token
153 * @tfm: an initialized hash transform
154 * @header: pointer to a buffer containing the token header, or NULL
155 * @hdrlen: number of octets in @header
156 * @body: xdr_buf containing an RPC message (body.len is the message length)
157 * @body_offset: byte offset into @body to start checksumming
158 * @cksumout: OUT: a buffer to be filled in with the computed HMAC
159 *
160 * Usually expressed as H = HMAC(K, message)[1..h] .
161 *
162 * Caller provides the truncation length of the output token (h) in
163 * cksumout.len.
164 *
165 * Return values:
166 *   %GSS_S_COMPLETE: Digest computed, @cksumout filled in
167 *   %GSS_S_FAILURE: Call failed
168 */
169u32
170gss_krb5_checksum(struct crypto_ahash *tfm, char *header, int hdrlen,
171		  const struct xdr_buf *body, int body_offset,
172		  struct xdr_netobj *cksumout)
173{
174	struct ahash_request *req;
175	int err = -ENOMEM;
176	u8 *checksumdata;
177
178	checksumdata = kmalloc(crypto_ahash_digestsize(tfm), GFP_KERNEL);
179	if (!checksumdata)
180		return GSS_S_FAILURE;
181
182	req = ahash_request_alloc(tfm, GFP_KERNEL);
183	if (!req)
184		goto out_free_cksum;
185	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
186	err = crypto_ahash_init(req);
187	if (err)
188		goto out_free_ahash;
189
190	/*
191	 * Per RFC 4121 Section 4.2.4, the checksum is performed over the
192	 * data body first, then over the octets in "header".
193	 */
194	err = xdr_process_buf(body, body_offset, body->len - body_offset,
195			      checksummer, req);
196	if (err)
197		goto out_free_ahash;
198	if (header) {
199		struct scatterlist sg[1];
200
201		sg_init_one(sg, header, hdrlen);
202		ahash_request_set_crypt(req, sg, NULL, hdrlen);
203		err = crypto_ahash_update(req);
204		if (err)
205			goto out_free_ahash;
206	}
207
208	ahash_request_set_crypt(req, NULL, checksumdata, 0);
209	err = crypto_ahash_final(req);
210	if (err)
211		goto out_free_ahash;
212
213	memcpy(cksumout->data, checksumdata,
214	       min_t(int, cksumout->len, crypto_ahash_digestsize(tfm)));
215
216out_free_ahash:
217	ahash_request_free(req);
218out_free_cksum:
219	kfree_sensitive(checksumdata);
220	return err ? GSS_S_FAILURE : GSS_S_COMPLETE;
221}
222EXPORT_SYMBOL_IF_KUNIT(gss_krb5_checksum);
223
224struct encryptor_desc {
225	u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
226	struct skcipher_request *req;
227	int pos;
228	struct xdr_buf *outbuf;
229	struct page **pages;
230	struct scatterlist infrags[4];
231	struct scatterlist outfrags[4];
232	int fragno;
233	int fraglen;
234};
235
236static int
237encryptor(struct scatterlist *sg, void *data)
238{
239	struct encryptor_desc *desc = data;
240	struct xdr_buf *outbuf = desc->outbuf;
241	struct crypto_sync_skcipher *tfm =
242		crypto_sync_skcipher_reqtfm(desc->req);
243	struct page *in_page;
244	int thislen = desc->fraglen + sg->length;
245	int fraglen, ret;
246	int page_pos;
247
248	/* Worst case is 4 fragments: head, end of page 1, start
249	 * of page 2, tail.  Anything more is a bug. */
250	BUG_ON(desc->fragno > 3);
251
252	page_pos = desc->pos - outbuf->head[0].iov_len;
253	if (page_pos >= 0 && page_pos < outbuf->page_len) {
254		/* pages are not in place: */
255		int i = (page_pos + outbuf->page_base) >> PAGE_SHIFT;
256		in_page = desc->pages[i];
257	} else {
258		in_page = sg_page(sg);
259	}
260	sg_set_page(&desc->infrags[desc->fragno], in_page, sg->length,
261		    sg->offset);
262	sg_set_page(&desc->outfrags[desc->fragno], sg_page(sg), sg->length,
263		    sg->offset);
264	desc->fragno++;
265	desc->fraglen += sg->length;
266	desc->pos += sg->length;
267
268	fraglen = thislen & (crypto_sync_skcipher_blocksize(tfm) - 1);
269	thislen -= fraglen;
270
271	if (thislen == 0)
272		return 0;
273
274	sg_mark_end(&desc->infrags[desc->fragno - 1]);
275	sg_mark_end(&desc->outfrags[desc->fragno - 1]);
276
277	skcipher_request_set_crypt(desc->req, desc->infrags, desc->outfrags,
278				   thislen, desc->iv);
279
280	ret = crypto_skcipher_encrypt(desc->req);
281	if (ret)
282		return ret;
283
284	sg_init_table(desc->infrags, 4);
285	sg_init_table(desc->outfrags, 4);
286
287	if (fraglen) {
288		sg_set_page(&desc->outfrags[0], sg_page(sg), fraglen,
289				sg->offset + sg->length - fraglen);
290		desc->infrags[0] = desc->outfrags[0];
291		sg_assign_page(&desc->infrags[0], in_page);
292		desc->fragno = 1;
293		desc->fraglen = fraglen;
294	} else {
295		desc->fragno = 0;
296		desc->fraglen = 0;
297	}
298	return 0;
299}
300
301struct decryptor_desc {
302	u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
303	struct skcipher_request *req;
304	struct scatterlist frags[4];
305	int fragno;
306	int fraglen;
307};
308
309static int
310decryptor(struct scatterlist *sg, void *data)
311{
312	struct decryptor_desc *desc = data;
313	int thislen = desc->fraglen + sg->length;
314	struct crypto_sync_skcipher *tfm =
315		crypto_sync_skcipher_reqtfm(desc->req);
316	int fraglen, ret;
317
318	/* Worst case is 4 fragments: head, end of page 1, start
319	 * of page 2, tail.  Anything more is a bug. */
320	BUG_ON(desc->fragno > 3);
321	sg_set_page(&desc->frags[desc->fragno], sg_page(sg), sg->length,
322		    sg->offset);
323	desc->fragno++;
324	desc->fraglen += sg->length;
325
326	fraglen = thislen & (crypto_sync_skcipher_blocksize(tfm) - 1);
327	thislen -= fraglen;
328
329	if (thislen == 0)
330		return 0;
331
332	sg_mark_end(&desc->frags[desc->fragno - 1]);
333
334	skcipher_request_set_crypt(desc->req, desc->frags, desc->frags,
335				   thislen, desc->iv);
336
337	ret = crypto_skcipher_decrypt(desc->req);
338	if (ret)
339		return ret;
340
341	sg_init_table(desc->frags, 4);
342
343	if (fraglen) {
344		sg_set_page(&desc->frags[0], sg_page(sg), fraglen,
345				sg->offset + sg->length - fraglen);
346		desc->fragno = 1;
347		desc->fraglen = fraglen;
348	} else {
349		desc->fragno = 0;
350		desc->fraglen = 0;
351	}
352	return 0;
353}
354
355/*
356 * This function makes the assumption that it was ultimately called
357 * from gss_wrap().
358 *
359 * The client auth_gss code moves any existing tail data into a
360 * separate page before calling gss_wrap.
361 * The server svcauth_gss code ensures that both the head and the
362 * tail have slack space of RPC_MAX_AUTH_SIZE before calling gss_wrap.
363 *
364 * Even with that guarantee, this function may be called more than
365 * once in the processing of gss_wrap().  The best we can do is
366 * verify at compile-time (see GSS_KRB5_SLACK_CHECK) that the
367 * largest expected shift will fit within RPC_MAX_AUTH_SIZE.
368 * At run-time we can verify that a single invocation of this
369 * function doesn't attempt to use more the RPC_MAX_AUTH_SIZE.
370 */
371
372int
373xdr_extend_head(struct xdr_buf *buf, unsigned int base, unsigned int shiftlen)
374{
375	u8 *p;
376
377	if (shiftlen == 0)
378		return 0;
379
380	BUG_ON(shiftlen > RPC_MAX_AUTH_SIZE);
381
382	p = buf->head[0].iov_base + base;
383
384	memmove(p + shiftlen, p, buf->head[0].iov_len - base);
385
386	buf->head[0].iov_len += shiftlen;
387	buf->len += shiftlen;
388
389	return 0;
390}
391
392static u32
393gss_krb5_cts_crypt(struct crypto_sync_skcipher *cipher, struct xdr_buf *buf,
394		   u32 offset, u8 *iv, struct page **pages, int encrypt)
395{
396	u32 ret;
397	struct scatterlist sg[1];
398	SYNC_SKCIPHER_REQUEST_ON_STACK(req, cipher);
399	u8 *data;
400	struct page **save_pages;
401	u32 len = buf->len - offset;
402
403	if (len > GSS_KRB5_MAX_BLOCKSIZE * 2) {
404		WARN_ON(0);
405		return -ENOMEM;
406	}
407	data = kmalloc(GSS_KRB5_MAX_BLOCKSIZE * 2, GFP_KERNEL);
408	if (!data)
409		return -ENOMEM;
410
411	/*
412	 * For encryption, we want to read from the cleartext
413	 * page cache pages, and write the encrypted data to
414	 * the supplied xdr_buf pages.
415	 */
416	save_pages = buf->pages;
417	if (encrypt)
418		buf->pages = pages;
419
420	ret = read_bytes_from_xdr_buf(buf, offset, data, len);
421	buf->pages = save_pages;
422	if (ret)
423		goto out;
424
425	sg_init_one(sg, data, len);
426
427	skcipher_request_set_sync_tfm(req, cipher);
428	skcipher_request_set_callback(req, 0, NULL, NULL);
429	skcipher_request_set_crypt(req, sg, sg, len, iv);
430
431	if (encrypt)
432		ret = crypto_skcipher_encrypt(req);
433	else
434		ret = crypto_skcipher_decrypt(req);
435
436	skcipher_request_zero(req);
437
438	if (ret)
439		goto out;
440
441	ret = write_bytes_to_xdr_buf(buf, offset, data, len);
442
443#if IS_ENABLED(CONFIG_KUNIT)
444	/*
445	 * CBC-CTS does not define an output IV but RFC 3962 defines it as the
446	 * penultimate block of ciphertext, so copy that into the IV buffer
447	 * before returning.
448	 */
449	if (encrypt)
450		memcpy(iv, data, crypto_sync_skcipher_ivsize(cipher));
451#endif
452
453out:
454	kfree(data);
455	return ret;
456}
457
458/**
459 * krb5_cbc_cts_encrypt - encrypt in CBC mode with CTS
460 * @cts_tfm: CBC cipher with CTS
461 * @cbc_tfm: base CBC cipher
462 * @offset: starting byte offset for plaintext
463 * @buf: OUT: output buffer
464 * @pages: plaintext
465 * @iv: output CBC initialization vector, or NULL
466 * @ivsize: size of @iv, in octets
467 *
468 * To provide confidentiality, encrypt using cipher block chaining
469 * with ciphertext stealing. Message integrity is handled separately.
470 *
471 * Return values:
472 *   %0: encryption successful
473 *   negative errno: encryption could not be completed
474 */
475VISIBLE_IF_KUNIT
476int krb5_cbc_cts_encrypt(struct crypto_sync_skcipher *cts_tfm,
477			 struct crypto_sync_skcipher *cbc_tfm,
478			 u32 offset, struct xdr_buf *buf, struct page **pages,
479			 u8 *iv, unsigned int ivsize)
480{
481	u32 blocksize, nbytes, nblocks, cbcbytes;
482	struct encryptor_desc desc;
483	int err;
484
485	blocksize = crypto_sync_skcipher_blocksize(cts_tfm);
486	nbytes = buf->len - offset;
487	nblocks = (nbytes + blocksize - 1) / blocksize;
488	cbcbytes = 0;
489	if (nblocks > 2)
490		cbcbytes = (nblocks - 2) * blocksize;
491
492	memset(desc.iv, 0, sizeof(desc.iv));
493
494	/* Handle block-sized chunks of plaintext with CBC. */
495	if (cbcbytes) {
496		SYNC_SKCIPHER_REQUEST_ON_STACK(req, cbc_tfm);
497
498		desc.pos = offset;
499		desc.fragno = 0;
500		desc.fraglen = 0;
501		desc.pages = pages;
502		desc.outbuf = buf;
503		desc.req = req;
504
505		skcipher_request_set_sync_tfm(req, cbc_tfm);
506		skcipher_request_set_callback(req, 0, NULL, NULL);
507
508		sg_init_table(desc.infrags, 4);
509		sg_init_table(desc.outfrags, 4);
510
511		err = xdr_process_buf(buf, offset, cbcbytes, encryptor, &desc);
512		skcipher_request_zero(req);
513		if (err)
514			return err;
515	}
516
517	/* Remaining plaintext is handled with CBC-CTS. */
518	err = gss_krb5_cts_crypt(cts_tfm, buf, offset + cbcbytes,
519				 desc.iv, pages, 1);
520	if (err)
521		return err;
522
523	if (unlikely(iv))
524		memcpy(iv, desc.iv, ivsize);
525	return 0;
526}
527EXPORT_SYMBOL_IF_KUNIT(krb5_cbc_cts_encrypt);
528
529/**
530 * krb5_cbc_cts_decrypt - decrypt in CBC mode with CTS
531 * @cts_tfm: CBC cipher with CTS
532 * @cbc_tfm: base CBC cipher
533 * @offset: starting byte offset for plaintext
534 * @buf: OUT: output buffer
535 *
536 * Return values:
537 *   %0: decryption successful
538 *   negative errno: decryption could not be completed
539 */
540VISIBLE_IF_KUNIT
541int krb5_cbc_cts_decrypt(struct crypto_sync_skcipher *cts_tfm,
542			 struct crypto_sync_skcipher *cbc_tfm,
543			 u32 offset, struct xdr_buf *buf)
544{
545	u32 blocksize, nblocks, cbcbytes;
546	struct decryptor_desc desc;
547	int err;
548
549	blocksize = crypto_sync_skcipher_blocksize(cts_tfm);
550	nblocks = (buf->len + blocksize - 1) / blocksize;
551	cbcbytes = 0;
552	if (nblocks > 2)
553		cbcbytes = (nblocks - 2) * blocksize;
554
555	memset(desc.iv, 0, sizeof(desc.iv));
556
557	/* Handle block-sized chunks of plaintext with CBC. */
558	if (cbcbytes) {
559		SYNC_SKCIPHER_REQUEST_ON_STACK(req, cbc_tfm);
560
561		desc.fragno = 0;
562		desc.fraglen = 0;
563		desc.req = req;
564
565		skcipher_request_set_sync_tfm(req, cbc_tfm);
566		skcipher_request_set_callback(req, 0, NULL, NULL);
567
568		sg_init_table(desc.frags, 4);
569
570		err = xdr_process_buf(buf, 0, cbcbytes, decryptor, &desc);
571		skcipher_request_zero(req);
572		if (err)
573			return err;
574	}
575
576	/* Remaining plaintext is handled with CBC-CTS. */
577	return gss_krb5_cts_crypt(cts_tfm, buf, cbcbytes, desc.iv, NULL, 0);
578}
579EXPORT_SYMBOL_IF_KUNIT(krb5_cbc_cts_decrypt);
580
581u32
582gss_krb5_aes_encrypt(struct krb5_ctx *kctx, u32 offset,
583		     struct xdr_buf *buf, struct page **pages)
584{
585	u32 err;
586	struct xdr_netobj hmac;
587	u8 *ecptr;
588	struct crypto_sync_skcipher *cipher, *aux_cipher;
589	struct crypto_ahash *ahash;
590	struct page **save_pages;
591	unsigned int conflen;
592
593	if (kctx->initiate) {
594		cipher = kctx->initiator_enc;
595		aux_cipher = kctx->initiator_enc_aux;
596		ahash = kctx->initiator_integ;
597	} else {
598		cipher = kctx->acceptor_enc;
599		aux_cipher = kctx->acceptor_enc_aux;
600		ahash = kctx->acceptor_integ;
601	}
602	conflen = crypto_sync_skcipher_blocksize(cipher);
603
604	/* hide the gss token header and insert the confounder */
605	offset += GSS_KRB5_TOK_HDR_LEN;
606	if (xdr_extend_head(buf, offset, conflen))
607		return GSS_S_FAILURE;
608	krb5_make_confounder(buf->head[0].iov_base + offset, conflen);
609	offset -= GSS_KRB5_TOK_HDR_LEN;
610
611	if (buf->tail[0].iov_base != NULL) {
612		ecptr = buf->tail[0].iov_base + buf->tail[0].iov_len;
613	} else {
614		buf->tail[0].iov_base = buf->head[0].iov_base
615							+ buf->head[0].iov_len;
616		buf->tail[0].iov_len = 0;
617		ecptr = buf->tail[0].iov_base;
618	}
619
620	/* copy plaintext gss token header after filler (if any) */
621	memcpy(ecptr, buf->head[0].iov_base + offset, GSS_KRB5_TOK_HDR_LEN);
622	buf->tail[0].iov_len += GSS_KRB5_TOK_HDR_LEN;
623	buf->len += GSS_KRB5_TOK_HDR_LEN;
624
625	hmac.len = kctx->gk5e->cksumlength;
626	hmac.data = buf->tail[0].iov_base + buf->tail[0].iov_len;
627
628	/*
629	 * When we are called, pages points to the real page cache
630	 * data -- which we can't go and encrypt!  buf->pages points
631	 * to scratch pages which we are going to send off to the
632	 * client/server.  Swap in the plaintext pages to calculate
633	 * the hmac.
634	 */
635	save_pages = buf->pages;
636	buf->pages = pages;
637
638	err = gss_krb5_checksum(ahash, NULL, 0, buf,
639				offset + GSS_KRB5_TOK_HDR_LEN, &hmac);
640	buf->pages = save_pages;
641	if (err)
642		return GSS_S_FAILURE;
643
644	err = krb5_cbc_cts_encrypt(cipher, aux_cipher,
645				   offset + GSS_KRB5_TOK_HDR_LEN,
646				   buf, pages, NULL, 0);
647	if (err)
648		return GSS_S_FAILURE;
649
650	/* Now update buf to account for HMAC */
651	buf->tail[0].iov_len += kctx->gk5e->cksumlength;
652	buf->len += kctx->gk5e->cksumlength;
653
654	return GSS_S_COMPLETE;
655}
656
657u32
658gss_krb5_aes_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len,
659		     struct xdr_buf *buf, u32 *headskip, u32 *tailskip)
660{
661	struct crypto_sync_skcipher *cipher, *aux_cipher;
662	struct crypto_ahash *ahash;
663	struct xdr_netobj our_hmac_obj;
664	u8 our_hmac[GSS_KRB5_MAX_CKSUM_LEN];
665	u8 pkt_hmac[GSS_KRB5_MAX_CKSUM_LEN];
666	struct xdr_buf subbuf;
667	u32 ret = 0;
668
669	if (kctx->initiate) {
670		cipher = kctx->acceptor_enc;
671		aux_cipher = kctx->acceptor_enc_aux;
672		ahash = kctx->acceptor_integ;
673	} else {
674		cipher = kctx->initiator_enc;
675		aux_cipher = kctx->initiator_enc_aux;
676		ahash = kctx->initiator_integ;
677	}
678
679	/* create a segment skipping the header and leaving out the checksum */
680	xdr_buf_subsegment(buf, &subbuf, offset + GSS_KRB5_TOK_HDR_LEN,
681				    (len - offset - GSS_KRB5_TOK_HDR_LEN -
682				     kctx->gk5e->cksumlength));
683
684	ret = krb5_cbc_cts_decrypt(cipher, aux_cipher, 0, &subbuf);
685	if (ret)
686		goto out_err;
687
688	our_hmac_obj.len = kctx->gk5e->cksumlength;
689	our_hmac_obj.data = our_hmac;
690	ret = gss_krb5_checksum(ahash, NULL, 0, &subbuf, 0, &our_hmac_obj);
691	if (ret)
692		goto out_err;
693
694	/* Get the packet's hmac value */
695	ret = read_bytes_from_xdr_buf(buf, len - kctx->gk5e->cksumlength,
696				      pkt_hmac, kctx->gk5e->cksumlength);
697	if (ret)
698		goto out_err;
699
700	if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
701		ret = GSS_S_BAD_SIG;
702		goto out_err;
703	}
704	*headskip = crypto_sync_skcipher_blocksize(cipher);
705	*tailskip = kctx->gk5e->cksumlength;
706out_err:
707	if (ret && ret != GSS_S_BAD_SIG)
708		ret = GSS_S_FAILURE;
709	return ret;
710}
711
712/**
713 * krb5_etm_checksum - Compute a MAC for a GSS Wrap token
714 * @cipher: an initialized cipher transform
715 * @tfm: an initialized hash transform
716 * @body: xdr_buf containing an RPC message (body.len is the message length)
717 * @body_offset: byte offset into @body to start checksumming
718 * @cksumout: OUT: a buffer to be filled in with the computed HMAC
719 *
720 * Usually expressed as H = HMAC(K, IV | ciphertext)[1..h] .
721 *
722 * Caller provides the truncation length of the output token (h) in
723 * cksumout.len.
724 *
725 * Return values:
726 *   %GSS_S_COMPLETE: Digest computed, @cksumout filled in
727 *   %GSS_S_FAILURE: Call failed
728 */
729VISIBLE_IF_KUNIT
730u32 krb5_etm_checksum(struct crypto_sync_skcipher *cipher,
731		      struct crypto_ahash *tfm, const struct xdr_buf *body,
732		      int body_offset, struct xdr_netobj *cksumout)
733{
734	unsigned int ivsize = crypto_sync_skcipher_ivsize(cipher);
735	struct ahash_request *req;
736	struct scatterlist sg[1];
737	u8 *iv, *checksumdata;
738	int err = -ENOMEM;
739
740	checksumdata = kmalloc(crypto_ahash_digestsize(tfm), GFP_KERNEL);
741	if (!checksumdata)
742		return GSS_S_FAILURE;
743	/* For RPCSEC, the "initial cipher state" is always all zeroes. */
744	iv = kzalloc(ivsize, GFP_KERNEL);
745	if (!iv)
746		goto out_free_mem;
747
748	req = ahash_request_alloc(tfm, GFP_KERNEL);
749	if (!req)
750		goto out_free_mem;
751	ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
752	err = crypto_ahash_init(req);
753	if (err)
754		goto out_free_ahash;
755
756	sg_init_one(sg, iv, ivsize);
757	ahash_request_set_crypt(req, sg, NULL, ivsize);
758	err = crypto_ahash_update(req);
759	if (err)
760		goto out_free_ahash;
761	err = xdr_process_buf(body, body_offset, body->len - body_offset,
762			      checksummer, req);
763	if (err)
764		goto out_free_ahash;
765
766	ahash_request_set_crypt(req, NULL, checksumdata, 0);
767	err = crypto_ahash_final(req);
768	if (err)
769		goto out_free_ahash;
770	memcpy(cksumout->data, checksumdata, cksumout->len);
771
772out_free_ahash:
773	ahash_request_free(req);
774out_free_mem:
775	kfree(iv);
776	kfree_sensitive(checksumdata);
777	return err ? GSS_S_FAILURE : GSS_S_COMPLETE;
778}
779EXPORT_SYMBOL_IF_KUNIT(krb5_etm_checksum);
780
781/**
782 * krb5_etm_encrypt - Encrypt using the RFC 8009 rules
783 * @kctx: Kerberos context
784 * @offset: starting offset of the payload, in bytes
785 * @buf: OUT: send buffer to contain the encrypted payload
786 * @pages: plaintext payload
787 *
788 * The main difference with aes_encrypt is that "The HMAC is
789 * calculated over the cipher state concatenated with the AES
790 * output, instead of being calculated over the confounder and
791 * plaintext.  This allows the message receiver to verify the
792 * integrity of the message before decrypting the message."
793 *
794 * RFC 8009 Section 5:
795 *
796 * encryption function: as follows, where E() is AES encryption in
797 * CBC-CS3 mode, and h is the size of truncated HMAC (128 bits or
798 * 192 bits as described above).
799 *
800 *    N = random value of length 128 bits (the AES block size)
801 *    IV = cipher state
802 *    C = E(Ke, N | plaintext, IV)
803 *    H = HMAC(Ki, IV | C)
804 *    ciphertext = C | H[1..h]
805 *
806 * This encryption formula provides AEAD EtM with key separation.
807 *
808 * Return values:
809 *   %GSS_S_COMPLETE: Encryption successful
810 *   %GSS_S_FAILURE: Encryption failed
811 */
812u32
813krb5_etm_encrypt(struct krb5_ctx *kctx, u32 offset,
814		 struct xdr_buf *buf, struct page **pages)
815{
816	struct crypto_sync_skcipher *cipher, *aux_cipher;
817	struct crypto_ahash *ahash;
818	struct xdr_netobj hmac;
819	unsigned int conflen;
820	u8 *ecptr;
821	u32 err;
822
823	if (kctx->initiate) {
824		cipher = kctx->initiator_enc;
825		aux_cipher = kctx->initiator_enc_aux;
826		ahash = kctx->initiator_integ;
827	} else {
828		cipher = kctx->acceptor_enc;
829		aux_cipher = kctx->acceptor_enc_aux;
830		ahash = kctx->acceptor_integ;
831	}
832	conflen = crypto_sync_skcipher_blocksize(cipher);
833
834	offset += GSS_KRB5_TOK_HDR_LEN;
835	if (xdr_extend_head(buf, offset, conflen))
836		return GSS_S_FAILURE;
837	krb5_make_confounder(buf->head[0].iov_base + offset, conflen);
838	offset -= GSS_KRB5_TOK_HDR_LEN;
839
840	if (buf->tail[0].iov_base) {
841		ecptr = buf->tail[0].iov_base + buf->tail[0].iov_len;
842	} else {
843		buf->tail[0].iov_base = buf->head[0].iov_base
844							+ buf->head[0].iov_len;
845		buf->tail[0].iov_len = 0;
846		ecptr = buf->tail[0].iov_base;
847	}
848
849	memcpy(ecptr, buf->head[0].iov_base + offset, GSS_KRB5_TOK_HDR_LEN);
850	buf->tail[0].iov_len += GSS_KRB5_TOK_HDR_LEN;
851	buf->len += GSS_KRB5_TOK_HDR_LEN;
852
853	err = krb5_cbc_cts_encrypt(cipher, aux_cipher,
854				   offset + GSS_KRB5_TOK_HDR_LEN,
855				   buf, pages, NULL, 0);
856	if (err)
857		return GSS_S_FAILURE;
858
859	hmac.data = buf->tail[0].iov_base + buf->tail[0].iov_len;
860	hmac.len = kctx->gk5e->cksumlength;
861	err = krb5_etm_checksum(cipher, ahash,
862				buf, offset + GSS_KRB5_TOK_HDR_LEN, &hmac);
863	if (err)
864		goto out_err;
865	buf->tail[0].iov_len += kctx->gk5e->cksumlength;
866	buf->len += kctx->gk5e->cksumlength;
867
868	return GSS_S_COMPLETE;
869
870out_err:
871	return GSS_S_FAILURE;
872}
873
874/**
875 * krb5_etm_decrypt - Decrypt using the RFC 8009 rules
876 * @kctx: Kerberos context
877 * @offset: starting offset of the ciphertext, in bytes
878 * @len: size of ciphertext to unwrap
879 * @buf: ciphertext to unwrap
880 * @headskip: OUT: the enctype's confounder length, in octets
881 * @tailskip: OUT: the enctype's HMAC length, in octets
882 *
883 * RFC 8009 Section 5:
884 *
885 * decryption function: as follows, where D() is AES decryption in
886 * CBC-CS3 mode, and h is the size of truncated HMAC.
887 *
888 *    (C, H) = ciphertext
889 *        (Note: H is the last h bits of the ciphertext.)
890 *    IV = cipher state
891 *    if H != HMAC(Ki, IV | C)[1..h]
892 *        stop, report error
893 *    (N, P) = D(Ke, C, IV)
894 *
895 * Return values:
896 *   %GSS_S_COMPLETE: Decryption successful
897 *   %GSS_S_BAD_SIG: computed HMAC != received HMAC
898 *   %GSS_S_FAILURE: Decryption failed
899 */
900u32
901krb5_etm_decrypt(struct krb5_ctx *kctx, u32 offset, u32 len,
902		 struct xdr_buf *buf, u32 *headskip, u32 *tailskip)
903{
904	struct crypto_sync_skcipher *cipher, *aux_cipher;
905	u8 our_hmac[GSS_KRB5_MAX_CKSUM_LEN];
906	u8 pkt_hmac[GSS_KRB5_MAX_CKSUM_LEN];
907	struct xdr_netobj our_hmac_obj;
908	struct crypto_ahash *ahash;
909	struct xdr_buf subbuf;
910	u32 ret = 0;
911
912	if (kctx->initiate) {
913		cipher = kctx->acceptor_enc;
914		aux_cipher = kctx->acceptor_enc_aux;
915		ahash = kctx->acceptor_integ;
916	} else {
917		cipher = kctx->initiator_enc;
918		aux_cipher = kctx->initiator_enc_aux;
919		ahash = kctx->initiator_integ;
920	}
921
922	/* Extract the ciphertext into @subbuf. */
923	xdr_buf_subsegment(buf, &subbuf, offset + GSS_KRB5_TOK_HDR_LEN,
924			   (len - offset - GSS_KRB5_TOK_HDR_LEN -
925			    kctx->gk5e->cksumlength));
926
927	our_hmac_obj.data = our_hmac;
928	our_hmac_obj.len = kctx->gk5e->cksumlength;
929	ret = krb5_etm_checksum(cipher, ahash, &subbuf, 0, &our_hmac_obj);
930	if (ret)
931		goto out_err;
932	ret = read_bytes_from_xdr_buf(buf, len - kctx->gk5e->cksumlength,
933				      pkt_hmac, kctx->gk5e->cksumlength);
934	if (ret)
935		goto out_err;
936	if (crypto_memneq(pkt_hmac, our_hmac, kctx->gk5e->cksumlength) != 0) {
937		ret = GSS_S_BAD_SIG;
938		goto out_err;
939	}
940
941	ret = krb5_cbc_cts_decrypt(cipher, aux_cipher, 0, &subbuf);
942	if (ret) {
943		ret = GSS_S_FAILURE;
944		goto out_err;
945	}
946
947	*headskip = crypto_sync_skcipher_blocksize(cipher);
948	*tailskip = kctx->gk5e->cksumlength;
949	return GSS_S_COMPLETE;
950
951out_err:
952	if (ret != GSS_S_BAD_SIG)
953		ret = GSS_S_FAILURE;
954	return ret;
955}