xref: /openbmc/linux/net/rxrpc/rxkad.c (revision 9b9c2cd4)
1 /* Kerberos-based RxRPC security
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/net.h>
14 #include <linux/skbuff.h>
15 #include <linux/udp.h>
16 #include <linux/crypto.h>
17 #include <linux/scatterlist.h>
18 #include <linux/ctype.h>
19 #include <linux/slab.h>
20 #include <net/sock.h>
21 #include <net/af_rxrpc.h>
22 #include <keys/rxrpc-type.h>
23 #define rxrpc_debug rxkad_debug
24 #include "ar-internal.h"
25 
26 #define RXKAD_VERSION			2
27 #define MAXKRB5TICKETLEN		1024
28 #define RXKAD_TKT_TYPE_KERBEROS_V5	256
29 #define ANAME_SZ			40	/* size of authentication name */
30 #define INST_SZ				40	/* size of principal's instance */
31 #define REALM_SZ			40	/* size of principal's auth domain */
32 #define SNAME_SZ			40	/* size of service name */
33 
34 unsigned int rxrpc_debug;
35 module_param_named(debug, rxrpc_debug, uint, S_IWUSR | S_IRUGO);
36 MODULE_PARM_DESC(debug, "rxkad debugging mask");
37 
38 struct rxkad_level1_hdr {
39 	__be32	data_size;	/* true data size (excluding padding) */
40 };
41 
42 struct rxkad_level2_hdr {
43 	__be32	data_size;	/* true data size (excluding padding) */
44 	__be32	checksum;	/* decrypted data checksum */
45 };
46 
47 MODULE_DESCRIPTION("RxRPC network protocol type-2 security (Kerberos 4)");
48 MODULE_AUTHOR("Red Hat, Inc.");
49 MODULE_LICENSE("GPL");
50 
51 /*
52  * this holds a pinned cipher so that keventd doesn't get called by the cipher
53  * alloc routine, but since we have it to hand, we use it to decrypt RESPONSE
54  * packets
55  */
56 static struct crypto_blkcipher *rxkad_ci;
57 static DEFINE_MUTEX(rxkad_ci_mutex);
58 
59 /*
60  * initialise connection security
61  */
62 static int rxkad_init_connection_security(struct rxrpc_connection *conn)
63 {
64 	struct crypto_blkcipher *ci;
65 	struct rxrpc_key_token *token;
66 	int ret;
67 
68 	_enter("{%d},{%x}", conn->debug_id, key_serial(conn->key));
69 
70 	token = conn->key->payload.data[0];
71 	conn->security_ix = token->security_index;
72 
73 	ci = crypto_alloc_blkcipher("pcbc(fcrypt)", 0, CRYPTO_ALG_ASYNC);
74 	if (IS_ERR(ci)) {
75 		_debug("no cipher");
76 		ret = PTR_ERR(ci);
77 		goto error;
78 	}
79 
80 	if (crypto_blkcipher_setkey(ci, token->kad->session_key,
81 				    sizeof(token->kad->session_key)) < 0)
82 		BUG();
83 
84 	switch (conn->security_level) {
85 	case RXRPC_SECURITY_PLAIN:
86 		break;
87 	case RXRPC_SECURITY_AUTH:
88 		conn->size_align = 8;
89 		conn->security_size = sizeof(struct rxkad_level1_hdr);
90 		conn->header_size += sizeof(struct rxkad_level1_hdr);
91 		break;
92 	case RXRPC_SECURITY_ENCRYPT:
93 		conn->size_align = 8;
94 		conn->security_size = sizeof(struct rxkad_level2_hdr);
95 		conn->header_size += sizeof(struct rxkad_level2_hdr);
96 		break;
97 	default:
98 		ret = -EKEYREJECTED;
99 		goto error;
100 	}
101 
102 	conn->cipher = ci;
103 	ret = 0;
104 error:
105 	_leave(" = %d", ret);
106 	return ret;
107 }
108 
109 /*
110  * prime the encryption state with the invariant parts of a connection's
111  * description
112  */
113 static void rxkad_prime_packet_security(struct rxrpc_connection *conn)
114 {
115 	struct rxrpc_key_token *token;
116 	struct blkcipher_desc desc;
117 	struct scatterlist sg[2];
118 	struct rxrpc_crypt iv;
119 	struct {
120 		__be32 x[4];
121 	} tmpbuf __attribute__((aligned(16))); /* must all be in same page */
122 
123 	_enter("");
124 
125 	if (!conn->key)
126 		return;
127 
128 	token = conn->key->payload.data[0];
129 	memcpy(&iv, token->kad->session_key, sizeof(iv));
130 
131 	desc.tfm = conn->cipher;
132 	desc.info = iv.x;
133 	desc.flags = 0;
134 
135 	tmpbuf.x[0] = conn->epoch;
136 	tmpbuf.x[1] = conn->cid;
137 	tmpbuf.x[2] = 0;
138 	tmpbuf.x[3] = htonl(conn->security_ix);
139 
140 	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
141 	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
142 	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));
143 
144 	memcpy(&conn->csum_iv, &tmpbuf.x[2], sizeof(conn->csum_iv));
145 	ASSERTCMP(conn->csum_iv.n[0], ==, tmpbuf.x[2]);
146 
147 	_leave("");
148 }
149 
150 /*
151  * partially encrypt a packet (level 1 security)
152  */
153 static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
154 				    struct sk_buff *skb,
155 				    u32 data_size,
156 				    void *sechdr)
157 {
158 	struct rxrpc_skb_priv *sp;
159 	struct blkcipher_desc desc;
160 	struct rxrpc_crypt iv;
161 	struct scatterlist sg[2];
162 	struct {
163 		struct rxkad_level1_hdr hdr;
164 		__be32	first;	/* first four bytes of data and padding */
165 	} tmpbuf __attribute__((aligned(8))); /* must all be in same page */
166 	u16 check;
167 
168 	sp = rxrpc_skb(skb);
169 
170 	_enter("");
171 
172 	check = ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
173 	data_size |= (u32) check << 16;
174 
175 	tmpbuf.hdr.data_size = htonl(data_size);
176 	memcpy(&tmpbuf.first, sechdr + 4, sizeof(tmpbuf.first));
177 
178 	/* start the encryption afresh */
179 	memset(&iv, 0, sizeof(iv));
180 	desc.tfm = call->conn->cipher;
181 	desc.info = iv.x;
182 	desc.flags = 0;
183 
184 	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
185 	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
186 	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));
187 
188 	memcpy(sechdr, &tmpbuf, sizeof(tmpbuf));
189 
190 	_leave(" = 0");
191 	return 0;
192 }
193 
194 /*
195  * wholly encrypt a packet (level 2 security)
196  */
197 static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
198 					struct sk_buff *skb,
199 					u32 data_size,
200 					void *sechdr)
201 {
202 	const struct rxrpc_key_token *token;
203 	struct rxkad_level2_hdr rxkhdr
204 		__attribute__((aligned(8))); /* must be all on one page */
205 	struct rxrpc_skb_priv *sp;
206 	struct blkcipher_desc desc;
207 	struct rxrpc_crypt iv;
208 	struct scatterlist sg[16];
209 	struct sk_buff *trailer;
210 	unsigned int len;
211 	u16 check;
212 	int nsg;
213 
214 	sp = rxrpc_skb(skb);
215 
216 	_enter("");
217 
218 	check = ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
219 
220 	rxkhdr.data_size = htonl(data_size | (u32) check << 16);
221 	rxkhdr.checksum = 0;
222 
223 	/* encrypt from the session key */
224 	token = call->conn->key->payload.data[0];
225 	memcpy(&iv, token->kad->session_key, sizeof(iv));
226 	desc.tfm = call->conn->cipher;
227 	desc.info = iv.x;
228 	desc.flags = 0;
229 
230 	sg_init_one(&sg[0], sechdr, sizeof(rxkhdr));
231 	sg_init_one(&sg[1], &rxkhdr, sizeof(rxkhdr));
232 	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(rxkhdr));
233 
234 	/* we want to encrypt the skbuff in-place */
235 	nsg = skb_cow_data(skb, 0, &trailer);
236 	if (nsg < 0 || nsg > 16)
237 		return -ENOMEM;
238 
239 	len = data_size + call->conn->size_align - 1;
240 	len &= ~(call->conn->size_align - 1);
241 
242 	sg_init_table(sg, nsg);
243 	skb_to_sgvec(skb, sg, 0, len);
244 	crypto_blkcipher_encrypt_iv(&desc, sg, sg, len);
245 
246 	_leave(" = 0");
247 	return 0;
248 }
249 
250 /*
251  * checksum an RxRPC packet header
252  */
253 static int rxkad_secure_packet(const struct rxrpc_call *call,
254 				struct sk_buff *skb,
255 				size_t data_size,
256 				void *sechdr)
257 {
258 	struct rxrpc_skb_priv *sp;
259 	struct blkcipher_desc desc;
260 	struct rxrpc_crypt iv;
261 	struct scatterlist sg[2];
262 	struct {
263 		__be32 x[2];
264 	} tmpbuf __attribute__((aligned(8))); /* must all be in same page */
265 	__be32 x;
266 	u32 y;
267 	int ret;
268 
269 	sp = rxrpc_skb(skb);
270 
271 	_enter("{%d{%x}},{#%u},%zu,",
272 	       call->debug_id, key_serial(call->conn->key), ntohl(sp->hdr.seq),
273 	       data_size);
274 
275 	if (!call->conn->cipher)
276 		return 0;
277 
278 	ret = key_validate(call->conn->key);
279 	if (ret < 0)
280 		return ret;
281 
282 	/* continue encrypting from where we left off */
283 	memcpy(&iv, call->conn->csum_iv.x, sizeof(iv));
284 	desc.tfm = call->conn->cipher;
285 	desc.info = iv.x;
286 	desc.flags = 0;
287 
288 	/* calculate the security checksum */
289 	x = htonl(call->channel << (32 - RXRPC_CIDSHIFT));
290 	x |= sp->hdr.seq & cpu_to_be32(0x3fffffff);
291 	tmpbuf.x[0] = sp->hdr.callNumber;
292 	tmpbuf.x[1] = x;
293 
294 	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
295 	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
296 	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));
297 
298 	y = ntohl(tmpbuf.x[1]);
299 	y = (y >> 16) & 0xffff;
300 	if (y == 0)
301 		y = 1; /* zero checksums are not permitted */
302 	sp->hdr.cksum = htons(y);
303 
304 	switch (call->conn->security_level) {
305 	case RXRPC_SECURITY_PLAIN:
306 		ret = 0;
307 		break;
308 	case RXRPC_SECURITY_AUTH:
309 		ret = rxkad_secure_packet_auth(call, skb, data_size, sechdr);
310 		break;
311 	case RXRPC_SECURITY_ENCRYPT:
312 		ret = rxkad_secure_packet_encrypt(call, skb, data_size,
313 						  sechdr);
314 		break;
315 	default:
316 		ret = -EPERM;
317 		break;
318 	}
319 
320 	_leave(" = %d [set %hx]", ret, y);
321 	return ret;
322 }
323 
324 /*
325  * decrypt partial encryption on a packet (level 1 security)
326  */
327 static int rxkad_verify_packet_auth(const struct rxrpc_call *call,
328 				    struct sk_buff *skb,
329 				    u32 *_abort_code)
330 {
331 	struct rxkad_level1_hdr sechdr;
332 	struct rxrpc_skb_priv *sp;
333 	struct blkcipher_desc desc;
334 	struct rxrpc_crypt iv;
335 	struct scatterlist sg[16];
336 	struct sk_buff *trailer;
337 	u32 data_size, buf;
338 	u16 check;
339 	int nsg;
340 
341 	_enter("");
342 
343 	sp = rxrpc_skb(skb);
344 
345 	/* we want to decrypt the skbuff in-place */
346 	nsg = skb_cow_data(skb, 0, &trailer);
347 	if (nsg < 0 || nsg > 16)
348 		goto nomem;
349 
350 	sg_init_table(sg, nsg);
351 	skb_to_sgvec(skb, sg, 0, 8);
352 
353 	/* start the decryption afresh */
354 	memset(&iv, 0, sizeof(iv));
355 	desc.tfm = call->conn->cipher;
356 	desc.info = iv.x;
357 	desc.flags = 0;
358 
359 	crypto_blkcipher_decrypt_iv(&desc, sg, sg, 8);
360 
361 	/* remove the decrypted packet length */
362 	if (skb_copy_bits(skb, 0, &sechdr, sizeof(sechdr)) < 0)
363 		goto datalen_error;
364 	if (!skb_pull(skb, sizeof(sechdr)))
365 		BUG();
366 
367 	buf = ntohl(sechdr.data_size);
368 	data_size = buf & 0xffff;
369 
370 	check = buf >> 16;
371 	check ^= ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
372 	check &= 0xffff;
373 	if (check != 0) {
374 		*_abort_code = RXKADSEALEDINCON;
375 		goto protocol_error;
376 	}
377 
378 	/* shorten the packet to remove the padding */
379 	if (data_size > skb->len)
380 		goto datalen_error;
381 	else if (data_size < skb->len)
382 		skb->len = data_size;
383 
384 	_leave(" = 0 [dlen=%x]", data_size);
385 	return 0;
386 
387 datalen_error:
388 	*_abort_code = RXKADDATALEN;
389 protocol_error:
390 	_leave(" = -EPROTO");
391 	return -EPROTO;
392 
393 nomem:
394 	_leave(" = -ENOMEM");
395 	return -ENOMEM;
396 }
397 
398 /*
399  * wholly decrypt a packet (level 2 security)
400  */
401 static int rxkad_verify_packet_encrypt(const struct rxrpc_call *call,
402 				       struct sk_buff *skb,
403 				       u32 *_abort_code)
404 {
405 	const struct rxrpc_key_token *token;
406 	struct rxkad_level2_hdr sechdr;
407 	struct rxrpc_skb_priv *sp;
408 	struct blkcipher_desc desc;
409 	struct rxrpc_crypt iv;
410 	struct scatterlist _sg[4], *sg;
411 	struct sk_buff *trailer;
412 	u32 data_size, buf;
413 	u16 check;
414 	int nsg;
415 
416 	_enter(",{%d}", skb->len);
417 
418 	sp = rxrpc_skb(skb);
419 
420 	/* we want to decrypt the skbuff in-place */
421 	nsg = skb_cow_data(skb, 0, &trailer);
422 	if (nsg < 0)
423 		goto nomem;
424 
425 	sg = _sg;
426 	if (unlikely(nsg > 4)) {
427 		sg = kmalloc(sizeof(*sg) * nsg, GFP_NOIO);
428 		if (!sg)
429 			goto nomem;
430 	}
431 
432 	sg_init_table(sg, nsg);
433 	skb_to_sgvec(skb, sg, 0, skb->len);
434 
435 	/* decrypt from the session key */
436 	token = call->conn->key->payload.data[0];
437 	memcpy(&iv, token->kad->session_key, sizeof(iv));
438 	desc.tfm = call->conn->cipher;
439 	desc.info = iv.x;
440 	desc.flags = 0;
441 
442 	crypto_blkcipher_decrypt_iv(&desc, sg, sg, skb->len);
443 	if (sg != _sg)
444 		kfree(sg);
445 
446 	/* remove the decrypted packet length */
447 	if (skb_copy_bits(skb, 0, &sechdr, sizeof(sechdr)) < 0)
448 		goto datalen_error;
449 	if (!skb_pull(skb, sizeof(sechdr)))
450 		BUG();
451 
452 	buf = ntohl(sechdr.data_size);
453 	data_size = buf & 0xffff;
454 
455 	check = buf >> 16;
456 	check ^= ntohl(sp->hdr.seq ^ sp->hdr.callNumber);
457 	check &= 0xffff;
458 	if (check != 0) {
459 		*_abort_code = RXKADSEALEDINCON;
460 		goto protocol_error;
461 	}
462 
463 	/* shorten the packet to remove the padding */
464 	if (data_size > skb->len)
465 		goto datalen_error;
466 	else if (data_size < skb->len)
467 		skb->len = data_size;
468 
469 	_leave(" = 0 [dlen=%x]", data_size);
470 	return 0;
471 
472 datalen_error:
473 	*_abort_code = RXKADDATALEN;
474 protocol_error:
475 	_leave(" = -EPROTO");
476 	return -EPROTO;
477 
478 nomem:
479 	_leave(" = -ENOMEM");
480 	return -ENOMEM;
481 }
482 
483 /*
484  * verify the security on a received packet
485  */
486 static int rxkad_verify_packet(const struct rxrpc_call *call,
487 			       struct sk_buff *skb,
488 			       u32 *_abort_code)
489 {
490 	struct blkcipher_desc desc;
491 	struct rxrpc_skb_priv *sp;
492 	struct rxrpc_crypt iv;
493 	struct scatterlist sg[2];
494 	struct {
495 		__be32 x[2];
496 	} tmpbuf __attribute__((aligned(8))); /* must all be in same page */
497 	__be32 x;
498 	__be16 cksum;
499 	u32 y;
500 	int ret;
501 
502 	sp = rxrpc_skb(skb);
503 
504 	_enter("{%d{%x}},{#%u}",
505 	       call->debug_id, key_serial(call->conn->key),
506 	       ntohl(sp->hdr.seq));
507 
508 	if (!call->conn->cipher)
509 		return 0;
510 
511 	if (sp->hdr.securityIndex != RXRPC_SECURITY_RXKAD) {
512 		*_abort_code = RXKADINCONSISTENCY;
513 		_leave(" = -EPROTO [not rxkad]");
514 		return -EPROTO;
515 	}
516 
517 	/* continue encrypting from where we left off */
518 	memcpy(&iv, call->conn->csum_iv.x, sizeof(iv));
519 	desc.tfm = call->conn->cipher;
520 	desc.info = iv.x;
521 	desc.flags = 0;
522 
523 	/* validate the security checksum */
524 	x = htonl(call->channel << (32 - RXRPC_CIDSHIFT));
525 	x |= sp->hdr.seq & cpu_to_be32(0x3fffffff);
526 	tmpbuf.x[0] = call->call_id;
527 	tmpbuf.x[1] = x;
528 
529 	sg_init_one(&sg[0], &tmpbuf, sizeof(tmpbuf));
530 	sg_init_one(&sg[1], &tmpbuf, sizeof(tmpbuf));
531 	crypto_blkcipher_encrypt_iv(&desc, &sg[0], &sg[1], sizeof(tmpbuf));
532 
533 	y = ntohl(tmpbuf.x[1]);
534 	y = (y >> 16) & 0xffff;
535 	if (y == 0)
536 		y = 1; /* zero checksums are not permitted */
537 
538 	cksum = htons(y);
539 	if (sp->hdr.cksum != cksum) {
540 		*_abort_code = RXKADSEALEDINCON;
541 		_leave(" = -EPROTO [csum failed]");
542 		return -EPROTO;
543 	}
544 
545 	switch (call->conn->security_level) {
546 	case RXRPC_SECURITY_PLAIN:
547 		ret = 0;
548 		break;
549 	case RXRPC_SECURITY_AUTH:
550 		ret = rxkad_verify_packet_auth(call, skb, _abort_code);
551 		break;
552 	case RXRPC_SECURITY_ENCRYPT:
553 		ret = rxkad_verify_packet_encrypt(call, skb, _abort_code);
554 		break;
555 	default:
556 		ret = -ENOANO;
557 		break;
558 	}
559 
560 	_leave(" = %d", ret);
561 	return ret;
562 }
563 
564 /*
565  * issue a challenge
566  */
567 static int rxkad_issue_challenge(struct rxrpc_connection *conn)
568 {
569 	struct rxkad_challenge challenge;
570 	struct rxrpc_header hdr;
571 	struct msghdr msg;
572 	struct kvec iov[2];
573 	size_t len;
574 	int ret;
575 
576 	_enter("{%d,%x}", conn->debug_id, key_serial(conn->key));
577 
578 	ret = key_validate(conn->key);
579 	if (ret < 0)
580 		return ret;
581 
582 	get_random_bytes(&conn->security_nonce, sizeof(conn->security_nonce));
583 
584 	challenge.version	= htonl(2);
585 	challenge.nonce		= htonl(conn->security_nonce);
586 	challenge.min_level	= htonl(0);
587 	challenge.__padding	= 0;
588 
589 	msg.msg_name	= &conn->trans->peer->srx.transport.sin;
590 	msg.msg_namelen	= sizeof(conn->trans->peer->srx.transport.sin);
591 	msg.msg_control	= NULL;
592 	msg.msg_controllen = 0;
593 	msg.msg_flags	= 0;
594 
595 	hdr.epoch	= conn->epoch;
596 	hdr.cid		= conn->cid;
597 	hdr.callNumber	= 0;
598 	hdr.seq		= 0;
599 	hdr.type	= RXRPC_PACKET_TYPE_CHALLENGE;
600 	hdr.flags	= conn->out_clientflag;
601 	hdr.userStatus	= 0;
602 	hdr.securityIndex = conn->security_ix;
603 	hdr._rsvd	= 0;
604 	hdr.serviceId	= conn->service_id;
605 
606 	iov[0].iov_base	= &hdr;
607 	iov[0].iov_len	= sizeof(hdr);
608 	iov[1].iov_base	= &challenge;
609 	iov[1].iov_len	= sizeof(challenge);
610 
611 	len = iov[0].iov_len + iov[1].iov_len;
612 
613 	hdr.serial = htonl(atomic_inc_return(&conn->serial));
614 	_proto("Tx CHALLENGE %%%u", ntohl(hdr.serial));
615 
616 	ret = kernel_sendmsg(conn->trans->local->socket, &msg, iov, 2, len);
617 	if (ret < 0) {
618 		_debug("sendmsg failed: %d", ret);
619 		return -EAGAIN;
620 	}
621 
622 	_leave(" = 0");
623 	return 0;
624 }
625 
626 /*
627  * send a Kerberos security response
628  */
629 static int rxkad_send_response(struct rxrpc_connection *conn,
630 			       struct rxrpc_header *hdr,
631 			       struct rxkad_response *resp,
632 			       const struct rxkad_key *s2)
633 {
634 	struct msghdr msg;
635 	struct kvec iov[3];
636 	size_t len;
637 	int ret;
638 
639 	_enter("");
640 
641 	msg.msg_name	= &conn->trans->peer->srx.transport.sin;
642 	msg.msg_namelen	= sizeof(conn->trans->peer->srx.transport.sin);
643 	msg.msg_control	= NULL;
644 	msg.msg_controllen = 0;
645 	msg.msg_flags	= 0;
646 
647 	hdr->epoch	= conn->epoch;
648 	hdr->seq	= 0;
649 	hdr->type	= RXRPC_PACKET_TYPE_RESPONSE;
650 	hdr->flags	= conn->out_clientflag;
651 	hdr->userStatus	= 0;
652 	hdr->_rsvd	= 0;
653 
654 	iov[0].iov_base	= hdr;
655 	iov[0].iov_len	= sizeof(*hdr);
656 	iov[1].iov_base	= resp;
657 	iov[1].iov_len	= sizeof(*resp);
658 	iov[2].iov_base	= (void *) s2->ticket;
659 	iov[2].iov_len	= s2->ticket_len;
660 
661 	len = iov[0].iov_len + iov[1].iov_len + iov[2].iov_len;
662 
663 	hdr->serial = htonl(atomic_inc_return(&conn->serial));
664 	_proto("Tx RESPONSE %%%u", ntohl(hdr->serial));
665 
666 	ret = kernel_sendmsg(conn->trans->local->socket, &msg, iov, 3, len);
667 	if (ret < 0) {
668 		_debug("sendmsg failed: %d", ret);
669 		return -EAGAIN;
670 	}
671 
672 	_leave(" = 0");
673 	return 0;
674 }
675 
676 /*
677  * calculate the response checksum
678  */
679 static void rxkad_calc_response_checksum(struct rxkad_response *response)
680 {
681 	u32 csum = 1000003;
682 	int loop;
683 	u8 *p = (u8 *) response;
684 
685 	for (loop = sizeof(*response); loop > 0; loop--)
686 		csum = csum * 0x10204081 + *p++;
687 
688 	response->encrypted.checksum = htonl(csum);
689 }
690 
691 /*
692  * load a scatterlist with a potentially split-page buffer
693  */
694 static void rxkad_sg_set_buf2(struct scatterlist sg[2],
695 			      void *buf, size_t buflen)
696 {
697 	int nsg = 1;
698 
699 	sg_init_table(sg, 2);
700 
701 	sg_set_buf(&sg[0], buf, buflen);
702 	if (sg[0].offset + buflen > PAGE_SIZE) {
703 		/* the buffer was split over two pages */
704 		sg[0].length = PAGE_SIZE - sg[0].offset;
705 		sg_set_buf(&sg[1], buf + sg[0].length, buflen - sg[0].length);
706 		nsg++;
707 	}
708 
709 	sg_mark_end(&sg[nsg - 1]);
710 
711 	ASSERTCMP(sg[0].length + sg[1].length, ==, buflen);
712 }
713 
714 /*
715  * encrypt the response packet
716  */
717 static void rxkad_encrypt_response(struct rxrpc_connection *conn,
718 				   struct rxkad_response *resp,
719 				   const struct rxkad_key *s2)
720 {
721 	struct blkcipher_desc desc;
722 	struct rxrpc_crypt iv;
723 	struct scatterlist sg[2];
724 
725 	/* continue encrypting from where we left off */
726 	memcpy(&iv, s2->session_key, sizeof(iv));
727 	desc.tfm = conn->cipher;
728 	desc.info = iv.x;
729 	desc.flags = 0;
730 
731 	rxkad_sg_set_buf2(sg, &resp->encrypted, sizeof(resp->encrypted));
732 	crypto_blkcipher_encrypt_iv(&desc, sg, sg, sizeof(resp->encrypted));
733 }
734 
735 /*
736  * respond to a challenge packet
737  */
738 static int rxkad_respond_to_challenge(struct rxrpc_connection *conn,
739 				      struct sk_buff *skb,
740 				      u32 *_abort_code)
741 {
742 	const struct rxrpc_key_token *token;
743 	struct rxkad_challenge challenge;
744 	struct rxkad_response resp
745 		__attribute__((aligned(8))); /* must be aligned for crypto */
746 	struct rxrpc_skb_priv *sp;
747 	u32 version, nonce, min_level, abort_code;
748 	int ret;
749 
750 	_enter("{%d,%x}", conn->debug_id, key_serial(conn->key));
751 
752 	if (!conn->key) {
753 		_leave(" = -EPROTO [no key]");
754 		return -EPROTO;
755 	}
756 
757 	ret = key_validate(conn->key);
758 	if (ret < 0) {
759 		*_abort_code = RXKADEXPIRED;
760 		return ret;
761 	}
762 
763 	abort_code = RXKADPACKETSHORT;
764 	sp = rxrpc_skb(skb);
765 	if (skb_copy_bits(skb, 0, &challenge, sizeof(challenge)) < 0)
766 		goto protocol_error;
767 
768 	version = ntohl(challenge.version);
769 	nonce = ntohl(challenge.nonce);
770 	min_level = ntohl(challenge.min_level);
771 
772 	_proto("Rx CHALLENGE %%%u { v=%u n=%u ml=%u }",
773 	       ntohl(sp->hdr.serial), version, nonce, min_level);
774 
775 	abort_code = RXKADINCONSISTENCY;
776 	if (version != RXKAD_VERSION)
777 		goto protocol_error;
778 
779 	abort_code = RXKADLEVELFAIL;
780 	if (conn->security_level < min_level)
781 		goto protocol_error;
782 
783 	token = conn->key->payload.data[0];
784 
785 	/* build the response packet */
786 	memset(&resp, 0, sizeof(resp));
787 
788 	resp.version = RXKAD_VERSION;
789 	resp.encrypted.epoch = conn->epoch;
790 	resp.encrypted.cid = conn->cid;
791 	resp.encrypted.securityIndex = htonl(conn->security_ix);
792 	resp.encrypted.call_id[0] =
793 		(conn->channels[0] ? conn->channels[0]->call_id : 0);
794 	resp.encrypted.call_id[1] =
795 		(conn->channels[1] ? conn->channels[1]->call_id : 0);
796 	resp.encrypted.call_id[2] =
797 		(conn->channels[2] ? conn->channels[2]->call_id : 0);
798 	resp.encrypted.call_id[3] =
799 		(conn->channels[3] ? conn->channels[3]->call_id : 0);
800 	resp.encrypted.inc_nonce = htonl(nonce + 1);
801 	resp.encrypted.level = htonl(conn->security_level);
802 	resp.kvno = htonl(token->kad->kvno);
803 	resp.ticket_len = htonl(token->kad->ticket_len);
804 
805 	/* calculate the response checksum and then do the encryption */
806 	rxkad_calc_response_checksum(&resp);
807 	rxkad_encrypt_response(conn, &resp, token->kad);
808 	return rxkad_send_response(conn, &sp->hdr, &resp, token->kad);
809 
810 protocol_error:
811 	*_abort_code = abort_code;
812 	_leave(" = -EPROTO [%d]", abort_code);
813 	return -EPROTO;
814 }
815 
816 /*
817  * decrypt the kerberos IV ticket in the response
818  */
819 static int rxkad_decrypt_ticket(struct rxrpc_connection *conn,
820 				void *ticket, size_t ticket_len,
821 				struct rxrpc_crypt *_session_key,
822 				time_t *_expiry,
823 				u32 *_abort_code)
824 {
825 	struct blkcipher_desc desc;
826 	struct rxrpc_crypt iv, key;
827 	struct scatterlist sg[1];
828 	struct in_addr addr;
829 	unsigned int life;
830 	time_t issue, now;
831 	bool little_endian;
832 	int ret;
833 	u8 *p, *q, *name, *end;
834 
835 	_enter("{%d},{%x}", conn->debug_id, key_serial(conn->server_key));
836 
837 	*_expiry = 0;
838 
839 	ret = key_validate(conn->server_key);
840 	if (ret < 0) {
841 		switch (ret) {
842 		case -EKEYEXPIRED:
843 			*_abort_code = RXKADEXPIRED;
844 			goto error;
845 		default:
846 			*_abort_code = RXKADNOAUTH;
847 			goto error;
848 		}
849 	}
850 
851 	ASSERT(conn->server_key->payload.data[0] != NULL);
852 	ASSERTCMP((unsigned long) ticket & 7UL, ==, 0);
853 
854 	memcpy(&iv, &conn->server_key->payload.data[2], sizeof(iv));
855 
856 	desc.tfm = conn->server_key->payload.data[0];
857 	desc.info = iv.x;
858 	desc.flags = 0;
859 
860 	sg_init_one(&sg[0], ticket, ticket_len);
861 	crypto_blkcipher_decrypt_iv(&desc, sg, sg, ticket_len);
862 
863 	p = ticket;
864 	end = p + ticket_len;
865 
866 #define Z(size)						\
867 	({						\
868 		u8 *__str = p;				\
869 		q = memchr(p, 0, end - p);		\
870 		if (!q || q - p > (size))		\
871 			goto bad_ticket;		\
872 		for (; p < q; p++)			\
873 			if (!isprint(*p))		\
874 				goto bad_ticket;	\
875 		p++;					\
876 		__str;					\
877 	})
878 
879 	/* extract the ticket flags */
880 	_debug("KIV FLAGS: %x", *p);
881 	little_endian = *p & 1;
882 	p++;
883 
884 	/* extract the authentication name */
885 	name = Z(ANAME_SZ);
886 	_debug("KIV ANAME: %s", name);
887 
888 	/* extract the principal's instance */
889 	name = Z(INST_SZ);
890 	_debug("KIV INST : %s", name);
891 
892 	/* extract the principal's authentication domain */
893 	name = Z(REALM_SZ);
894 	_debug("KIV REALM: %s", name);
895 
896 	if (end - p < 4 + 8 + 4 + 2)
897 		goto bad_ticket;
898 
899 	/* get the IPv4 address of the entity that requested the ticket */
900 	memcpy(&addr, p, sizeof(addr));
901 	p += 4;
902 	_debug("KIV ADDR : %pI4", &addr);
903 
904 	/* get the session key from the ticket */
905 	memcpy(&key, p, sizeof(key));
906 	p += 8;
907 	_debug("KIV KEY  : %08x %08x", ntohl(key.n[0]), ntohl(key.n[1]));
908 	memcpy(_session_key, &key, sizeof(key));
909 
910 	/* get the ticket's lifetime */
911 	life = *p++ * 5 * 60;
912 	_debug("KIV LIFE : %u", life);
913 
914 	/* get the issue time of the ticket */
915 	if (little_endian) {
916 		__le32 stamp;
917 		memcpy(&stamp, p, 4);
918 		issue = le32_to_cpu(stamp);
919 	} else {
920 		__be32 stamp;
921 		memcpy(&stamp, p, 4);
922 		issue = be32_to_cpu(stamp);
923 	}
924 	p += 4;
925 	now = get_seconds();
926 	_debug("KIV ISSUE: %lx [%lx]", issue, now);
927 
928 	/* check the ticket is in date */
929 	if (issue > now) {
930 		*_abort_code = RXKADNOAUTH;
931 		ret = -EKEYREJECTED;
932 		goto error;
933 	}
934 
935 	if (issue < now - life) {
936 		*_abort_code = RXKADEXPIRED;
937 		ret = -EKEYEXPIRED;
938 		goto error;
939 	}
940 
941 	*_expiry = issue + life;
942 
943 	/* get the service name */
944 	name = Z(SNAME_SZ);
945 	_debug("KIV SNAME: %s", name);
946 
947 	/* get the service instance name */
948 	name = Z(INST_SZ);
949 	_debug("KIV SINST: %s", name);
950 
951 	ret = 0;
952 error:
953 	_leave(" = %d", ret);
954 	return ret;
955 
956 bad_ticket:
957 	*_abort_code = RXKADBADTICKET;
958 	ret = -EBADMSG;
959 	goto error;
960 }
961 
962 /*
963  * decrypt the response packet
964  */
965 static void rxkad_decrypt_response(struct rxrpc_connection *conn,
966 				   struct rxkad_response *resp,
967 				   const struct rxrpc_crypt *session_key)
968 {
969 	struct blkcipher_desc desc;
970 	struct scatterlist sg[2];
971 	struct rxrpc_crypt iv;
972 
973 	_enter(",,%08x%08x",
974 	       ntohl(session_key->n[0]), ntohl(session_key->n[1]));
975 
976 	ASSERT(rxkad_ci != NULL);
977 
978 	mutex_lock(&rxkad_ci_mutex);
979 	if (crypto_blkcipher_setkey(rxkad_ci, session_key->x,
980 				    sizeof(*session_key)) < 0)
981 		BUG();
982 
983 	memcpy(&iv, session_key, sizeof(iv));
984 	desc.tfm = rxkad_ci;
985 	desc.info = iv.x;
986 	desc.flags = 0;
987 
988 	rxkad_sg_set_buf2(sg, &resp->encrypted, sizeof(resp->encrypted));
989 	crypto_blkcipher_decrypt_iv(&desc, sg, sg, sizeof(resp->encrypted));
990 	mutex_unlock(&rxkad_ci_mutex);
991 
992 	_leave("");
993 }
994 
995 /*
996  * verify a response
997  */
998 static int rxkad_verify_response(struct rxrpc_connection *conn,
999 				 struct sk_buff *skb,
1000 				 u32 *_abort_code)
1001 {
1002 	struct rxkad_response response
1003 		__attribute__((aligned(8))); /* must be aligned for crypto */
1004 	struct rxrpc_skb_priv *sp;
1005 	struct rxrpc_crypt session_key;
1006 	time_t expiry;
1007 	void *ticket;
1008 	u32 abort_code, version, kvno, ticket_len, level;
1009 	__be32 csum;
1010 	int ret;
1011 
1012 	_enter("{%d,%x}", conn->debug_id, key_serial(conn->server_key));
1013 
1014 	abort_code = RXKADPACKETSHORT;
1015 	if (skb_copy_bits(skb, 0, &response, sizeof(response)) < 0)
1016 		goto protocol_error;
1017 	if (!pskb_pull(skb, sizeof(response)))
1018 		BUG();
1019 
1020 	version = ntohl(response.version);
1021 	ticket_len = ntohl(response.ticket_len);
1022 	kvno = ntohl(response.kvno);
1023 	sp = rxrpc_skb(skb);
1024 	_proto("Rx RESPONSE %%%u { v=%u kv=%u tl=%u }",
1025 	       ntohl(sp->hdr.serial), version, kvno, ticket_len);
1026 
1027 	abort_code = RXKADINCONSISTENCY;
1028 	if (version != RXKAD_VERSION)
1029 		goto protocol_error;
1030 
1031 	abort_code = RXKADTICKETLEN;
1032 	if (ticket_len < 4 || ticket_len > MAXKRB5TICKETLEN)
1033 		goto protocol_error;
1034 
1035 	abort_code = RXKADUNKNOWNKEY;
1036 	if (kvno >= RXKAD_TKT_TYPE_KERBEROS_V5)
1037 		goto protocol_error;
1038 
1039 	/* extract the kerberos ticket and decrypt and decode it */
1040 	ticket = kmalloc(ticket_len, GFP_NOFS);
1041 	if (!ticket)
1042 		return -ENOMEM;
1043 
1044 	abort_code = RXKADPACKETSHORT;
1045 	if (skb_copy_bits(skb, 0, ticket, ticket_len) < 0)
1046 		goto protocol_error_free;
1047 
1048 	ret = rxkad_decrypt_ticket(conn, ticket, ticket_len, &session_key,
1049 				   &expiry, &abort_code);
1050 	if (ret < 0) {
1051 		*_abort_code = abort_code;
1052 		kfree(ticket);
1053 		return ret;
1054 	}
1055 
1056 	/* use the session key from inside the ticket to decrypt the
1057 	 * response */
1058 	rxkad_decrypt_response(conn, &response, &session_key);
1059 
1060 	abort_code = RXKADSEALEDINCON;
1061 	if (response.encrypted.epoch != conn->epoch)
1062 		goto protocol_error_free;
1063 	if (response.encrypted.cid != conn->cid)
1064 		goto protocol_error_free;
1065 	if (ntohl(response.encrypted.securityIndex) != conn->security_ix)
1066 		goto protocol_error_free;
1067 	csum = response.encrypted.checksum;
1068 	response.encrypted.checksum = 0;
1069 	rxkad_calc_response_checksum(&response);
1070 	if (response.encrypted.checksum != csum)
1071 		goto protocol_error_free;
1072 
1073 	if (ntohl(response.encrypted.call_id[0]) > INT_MAX ||
1074 	    ntohl(response.encrypted.call_id[1]) > INT_MAX ||
1075 	    ntohl(response.encrypted.call_id[2]) > INT_MAX ||
1076 	    ntohl(response.encrypted.call_id[3]) > INT_MAX)
1077 		goto protocol_error_free;
1078 
1079 	abort_code = RXKADOUTOFSEQUENCE;
1080 	if (response.encrypted.inc_nonce != htonl(conn->security_nonce + 1))
1081 		goto protocol_error_free;
1082 
1083 	abort_code = RXKADLEVELFAIL;
1084 	level = ntohl(response.encrypted.level);
1085 	if (level > RXRPC_SECURITY_ENCRYPT)
1086 		goto protocol_error_free;
1087 	conn->security_level = level;
1088 
1089 	/* create a key to hold the security data and expiration time - after
1090 	 * this the connection security can be handled in exactly the same way
1091 	 * as for a client connection */
1092 	ret = rxrpc_get_server_data_key(conn, &session_key, expiry, kvno);
1093 	if (ret < 0) {
1094 		kfree(ticket);
1095 		return ret;
1096 	}
1097 
1098 	kfree(ticket);
1099 	_leave(" = 0");
1100 	return 0;
1101 
1102 protocol_error_free:
1103 	kfree(ticket);
1104 protocol_error:
1105 	*_abort_code = abort_code;
1106 	_leave(" = -EPROTO [%d]", abort_code);
1107 	return -EPROTO;
1108 }
1109 
1110 /*
1111  * clear the connection security
1112  */
1113 static void rxkad_clear(struct rxrpc_connection *conn)
1114 {
1115 	_enter("");
1116 
1117 	if (conn->cipher)
1118 		crypto_free_blkcipher(conn->cipher);
1119 }
1120 
1121 /*
1122  * RxRPC Kerberos-based security
1123  */
1124 static struct rxrpc_security rxkad = {
1125 	.owner				= THIS_MODULE,
1126 	.name				= "rxkad",
1127 	.security_index			= RXRPC_SECURITY_RXKAD,
1128 	.init_connection_security	= rxkad_init_connection_security,
1129 	.prime_packet_security		= rxkad_prime_packet_security,
1130 	.secure_packet			= rxkad_secure_packet,
1131 	.verify_packet			= rxkad_verify_packet,
1132 	.issue_challenge		= rxkad_issue_challenge,
1133 	.respond_to_challenge		= rxkad_respond_to_challenge,
1134 	.verify_response		= rxkad_verify_response,
1135 	.clear				= rxkad_clear,
1136 };
1137 
1138 static __init int rxkad_init(void)
1139 {
1140 	_enter("");
1141 
1142 	/* pin the cipher we need so that the crypto layer doesn't invoke
1143 	 * keventd to go get it */
1144 	rxkad_ci = crypto_alloc_blkcipher("pcbc(fcrypt)", 0, CRYPTO_ALG_ASYNC);
1145 	if (IS_ERR(rxkad_ci))
1146 		return PTR_ERR(rxkad_ci);
1147 
1148 	return rxrpc_register_security(&rxkad);
1149 }
1150 
1151 module_init(rxkad_init);
1152 
1153 static __exit void rxkad_exit(void)
1154 {
1155 	_enter("");
1156 
1157 	rxrpc_unregister_security(&rxkad);
1158 	crypto_free_blkcipher(rxkad_ci);
1159 }
1160 
1161 module_exit(rxkad_exit);
1162