xref: /linux/net/ipv4/ah4.c (revision 985d4a55e64e43bd86eeb896b81ceba453301989) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 #define pr_fmt(fmt) "IPsec: " fmt
3 
4 #include <crypto/hash.h>
5 #include <crypto/utils.h>
6 #include <linux/err.h>
7 #include <linux/module.h>
8 #include <linux/slab.h>
9 #include <net/ip.h>
10 #include <net/xfrm.h>
11 #include <net/ah.h>
12 #include <linux/crypto.h>
13 #include <linux/pfkeyv2.h>
14 #include <linux/scatterlist.h>
15 #include <net/icmp.h>
16 #include <net/protocol.h>
17 
18 struct ah_skb_cb {
19 	struct xfrm_skb_cb xfrm;
20 	void *tmp;
21 };
22 
23 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
24 
25 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
26 			  unsigned int size)
27 {
28 	unsigned int len;
29 
30 	len = size + crypto_ahash_digestsize(ahash);
31 
32 	len = ALIGN(len, crypto_tfm_ctx_alignment());
33 
34 	len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
35 	len = ALIGN(len, __alignof__(struct scatterlist));
36 
37 	len += sizeof(struct scatterlist) * nfrags;
38 
39 	return kmalloc(len, GFP_ATOMIC);
40 }
41 
42 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
43 {
44 	return tmp + offset;
45 }
46 
47 static inline u8 *ah_tmp_icv(void *tmp, unsigned int offset)
48 {
49 	return tmp + offset;
50 }
51 
52 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
53 					       u8 *icv)
54 {
55 	struct ahash_request *req;
56 
57 	req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
58 				crypto_tfm_ctx_alignment());
59 
60 	ahash_request_set_tfm(req, ahash);
61 
62 	return req;
63 }
64 
65 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
66 					     struct ahash_request *req)
67 {
68 	return (void *)ALIGN((unsigned long)(req + 1) +
69 			     crypto_ahash_reqsize(ahash),
70 			     __alignof__(struct scatterlist));
71 }
72 
73 /* Clear mutable options and find final destination to substitute
74  * into IP header for icv calculation. Options are already checked
75  * for validity, so paranoia is not required. */
76 
77 static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
78 {
79 	unsigned char *optptr = (unsigned char *)(iph+1);
80 	int  l = iph->ihl*4 - sizeof(struct iphdr);
81 	int  optlen;
82 
83 	while (l > 0) {
84 		switch (*optptr) {
85 		case IPOPT_END:
86 			return 0;
87 		case IPOPT_NOOP:
88 			l--;
89 			optptr++;
90 			continue;
91 		}
92 		optlen = optptr[1];
93 		if (optlen<2 || optlen>l)
94 			return -EINVAL;
95 		switch (*optptr) {
96 		case IPOPT_SEC:
97 		case 0x85:	/* Some "Extended Security" crap. */
98 		case IPOPT_CIPSO:
99 		case IPOPT_RA:
100 		case 0x80|21:	/* RFC1770 */
101 			break;
102 		case IPOPT_LSRR:
103 		case IPOPT_SSRR:
104 			if (optlen < 6)
105 				return -EINVAL;
106 			memcpy(daddr, optptr+optlen-4, 4);
107 			fallthrough;
108 		default:
109 			memset(optptr, 0, optlen);
110 		}
111 		l -= optlen;
112 		optptr += optlen;
113 	}
114 	return 0;
115 }
116 
117 static void ah_output_done(void *data, int err)
118 {
119 	u8 *icv;
120 	struct iphdr *iph;
121 	struct sk_buff *skb = data;
122 	struct xfrm_state *x = skb_dst(skb)->xfrm;
123 	struct ah_data *ahp = x->data;
124 	struct iphdr *top_iph = ip_hdr(skb);
125 	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
126 	int ihl = ip_hdrlen(skb);
127 	int seqhi_len = 0;
128 	__be32 *seqhi;
129 
130 	if (x->props.flags & XFRM_STATE_ESN)
131 		seqhi_len = sizeof(*seqhi);
132 	iph = AH_SKB_CB(skb)->tmp;
133 	seqhi = (__be32 *)((char *)iph + ihl);
134 	icv = ah_tmp_icv(seqhi, seqhi_len);
135 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
136 
137 	top_iph->tos = iph->tos;
138 	top_iph->ttl = iph->ttl;
139 	top_iph->frag_off = iph->frag_off;
140 	if (top_iph->ihl != 5) {
141 		top_iph->daddr = iph->daddr;
142 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
143 	}
144 
145 	kfree(AH_SKB_CB(skb)->tmp);
146 	xfrm_output_resume(skb->sk, skb, err);
147 }
148 
149 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
150 {
151 	int err;
152 	int nfrags;
153 	int ihl;
154 	u8 *icv;
155 	struct sk_buff *trailer;
156 	struct crypto_ahash *ahash;
157 	struct ahash_request *req;
158 	struct scatterlist *sg;
159 	struct iphdr *iph, *top_iph;
160 	struct ip_auth_hdr *ah;
161 	struct ah_data *ahp;
162 	int seqhi_len = 0;
163 	__be32 *seqhi;
164 	int sglists = 0;
165 	struct scatterlist *seqhisg;
166 
167 	ahp = x->data;
168 	ahash = ahp->ahash;
169 
170 	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
171 		goto out;
172 	nfrags = err;
173 
174 	skb_push(skb, -skb_network_offset(skb));
175 	ah = ip_auth_hdr(skb);
176 	ihl = ip_hdrlen(skb);
177 
178 	if (x->props.flags & XFRM_STATE_ESN) {
179 		sglists = 1;
180 		seqhi_len = sizeof(*seqhi);
181 	}
182 	err = -ENOMEM;
183 	iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
184 	if (!iph)
185 		goto out;
186 	seqhi = (__be32 *)((char *)iph + ihl);
187 	icv = ah_tmp_icv(seqhi, seqhi_len);
188 	req = ah_tmp_req(ahash, icv);
189 	sg = ah_req_sg(ahash, req);
190 	seqhisg = sg + nfrags;
191 
192 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
193 
194 	top_iph = ip_hdr(skb);
195 
196 	iph->tos = top_iph->tos;
197 	iph->ttl = top_iph->ttl;
198 	iph->frag_off = top_iph->frag_off;
199 
200 	if (top_iph->ihl != 5) {
201 		iph->daddr = top_iph->daddr;
202 		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
203 		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
204 		if (err)
205 			goto out_free;
206 	}
207 
208 	ah->nexthdr = *skb_mac_header(skb);
209 	*skb_mac_header(skb) = IPPROTO_AH;
210 
211 	top_iph->tos = 0;
212 	top_iph->tot_len = htons(skb->len);
213 	top_iph->frag_off = 0;
214 	top_iph->ttl = 0;
215 	top_iph->check = 0;
216 
217 	if (x->props.flags & XFRM_STATE_ALIGN4)
218 		ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
219 	else
220 		ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
221 
222 	ah->reserved = 0;
223 	ah->spi = x->id.spi;
224 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
225 
226 	sg_init_table(sg, nfrags + sglists);
227 	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
228 	if (unlikely(err < 0))
229 		goto out_free;
230 
231 	if (x->props.flags & XFRM_STATE_ESN) {
232 		/* Attach seqhi sg right after packet payload */
233 		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
234 		sg_set_buf(seqhisg, seqhi, seqhi_len);
235 	}
236 	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
237 	ahash_request_set_callback(req, 0, ah_output_done, skb);
238 
239 	AH_SKB_CB(skb)->tmp = iph;
240 
241 	err = crypto_ahash_digest(req);
242 	if (err) {
243 		if (err == -EINPROGRESS)
244 			goto out;
245 
246 		if (err == -ENOSPC)
247 			err = NET_XMIT_DROP;
248 		goto out_free;
249 	}
250 
251 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
252 
253 	top_iph->tos = iph->tos;
254 	top_iph->ttl = iph->ttl;
255 	top_iph->frag_off = iph->frag_off;
256 	if (top_iph->ihl != 5) {
257 		top_iph->daddr = iph->daddr;
258 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
259 	}
260 
261 out_free:
262 	kfree(iph);
263 out:
264 	return err;
265 }
266 
267 static void ah_input_done(void *data, int err)
268 {
269 	u8 *auth_data;
270 	u8 *icv;
271 	struct iphdr *work_iph;
272 	struct sk_buff *skb = data;
273 	struct xfrm_state *x = xfrm_input_state(skb);
274 	struct ah_data *ahp = x->data;
275 	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
276 	int ihl = ip_hdrlen(skb);
277 	int ah_hlen = (ah->hdrlen + 2) << 2;
278 	int seqhi_len = 0;
279 	__be32 *seqhi;
280 
281 	if (err)
282 		goto out;
283 
284 	if (x->props.flags & XFRM_STATE_ESN)
285 		seqhi_len = sizeof(*seqhi);
286 	work_iph = AH_SKB_CB(skb)->tmp;
287 	seqhi = (__be32 *)((char *)work_iph + ihl);
288 	auth_data = ah_tmp_auth(seqhi, seqhi_len);
289 	icv = ah_tmp_icv(auth_data, ahp->icv_trunc_len);
290 
291 	err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
292 	if (err)
293 		goto out;
294 
295 	err = ah->nexthdr;
296 
297 	skb->network_header += ah_hlen;
298 	memcpy(skb_network_header(skb), work_iph, ihl);
299 	__skb_pull(skb, ah_hlen + ihl);
300 
301 	if (x->props.mode == XFRM_MODE_TUNNEL)
302 		skb_reset_transport_header(skb);
303 	else
304 		skb_set_transport_header(skb, -ihl);
305 out:
306 	kfree(AH_SKB_CB(skb)->tmp);
307 	xfrm_input_resume(skb, err);
308 }
309 
310 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
311 {
312 	int ah_hlen;
313 	int ihl;
314 	int nexthdr;
315 	int nfrags;
316 	u8 *auth_data;
317 	u8 *icv;
318 	struct sk_buff *trailer;
319 	struct crypto_ahash *ahash;
320 	struct ahash_request *req;
321 	struct scatterlist *sg;
322 	struct iphdr *iph, *work_iph;
323 	struct ip_auth_hdr *ah;
324 	struct ah_data *ahp;
325 	int err = -ENOMEM;
326 	int seqhi_len = 0;
327 	__be32 *seqhi;
328 	int sglists = 0;
329 	struct scatterlist *seqhisg;
330 
331 	if (!pskb_may_pull(skb, sizeof(*ah)))
332 		goto out;
333 
334 	ah = (struct ip_auth_hdr *)skb->data;
335 	ahp = x->data;
336 	ahash = ahp->ahash;
337 
338 	nexthdr = ah->nexthdr;
339 	ah_hlen = (ah->hdrlen + 2) << 2;
340 
341 	if (x->props.flags & XFRM_STATE_ALIGN4) {
342 		if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
343 		    ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
344 			goto out;
345 	} else {
346 		if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
347 		    ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
348 			goto out;
349 	}
350 
351 	if (!pskb_may_pull(skb, ah_hlen))
352 		goto out;
353 
354 	/* We are going to _remove_ AH header to keep sockets happy,
355 	 * so... Later this can change. */
356 	if (skb_unclone(skb, GFP_ATOMIC))
357 		goto out;
358 
359 	skb->ip_summed = CHECKSUM_NONE;
360 
361 
362 	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
363 		goto out;
364 	nfrags = err;
365 
366 	ah = (struct ip_auth_hdr *)skb->data;
367 	iph = ip_hdr(skb);
368 	ihl = ip_hdrlen(skb);
369 
370 	if (x->props.flags & XFRM_STATE_ESN) {
371 		sglists = 1;
372 		seqhi_len = sizeof(*seqhi);
373 	}
374 
375 	work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
376 				ahp->icv_trunc_len + seqhi_len);
377 	if (!work_iph) {
378 		err = -ENOMEM;
379 		goto out;
380 	}
381 
382 	seqhi = (__be32 *)((char *)work_iph + ihl);
383 	auth_data = ah_tmp_auth(seqhi, seqhi_len);
384 	icv = ah_tmp_icv(auth_data, ahp->icv_trunc_len);
385 	req = ah_tmp_req(ahash, icv);
386 	sg = ah_req_sg(ahash, req);
387 	seqhisg = sg + nfrags;
388 
389 	memcpy(work_iph, iph, ihl);
390 	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
391 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
392 
393 	iph->ttl = 0;
394 	iph->tos = 0;
395 	iph->frag_off = 0;
396 	iph->check = 0;
397 	if (ihl > sizeof(*iph)) {
398 		__be32 dummy;
399 		err = ip_clear_mutable_options(iph, &dummy);
400 		if (err)
401 			goto out_free;
402 	}
403 
404 	skb_push(skb, ihl);
405 
406 	sg_init_table(sg, nfrags + sglists);
407 	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
408 	if (unlikely(err < 0))
409 		goto out_free;
410 
411 	if (x->props.flags & XFRM_STATE_ESN) {
412 		/* Attach seqhi sg right after packet payload */
413 		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
414 		sg_set_buf(seqhisg, seqhi, seqhi_len);
415 	}
416 	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
417 	ahash_request_set_callback(req, 0, ah_input_done, skb);
418 
419 	AH_SKB_CB(skb)->tmp = work_iph;
420 
421 	err = crypto_ahash_digest(req);
422 	if (err) {
423 		if (err == -EINPROGRESS)
424 			goto out;
425 
426 		goto out_free;
427 	}
428 
429 	err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
430 	if (err)
431 		goto out_free;
432 
433 	skb->network_header += ah_hlen;
434 	memcpy(skb_network_header(skb), work_iph, ihl);
435 	__skb_pull(skb, ah_hlen + ihl);
436 	if (x->props.mode == XFRM_MODE_TUNNEL)
437 		skb_reset_transport_header(skb);
438 	else
439 		skb_set_transport_header(skb, -ihl);
440 
441 	err = nexthdr;
442 
443 out_free:
444 	kfree (work_iph);
445 out:
446 	return err;
447 }
448 
449 static int ah4_err(struct sk_buff *skb, u32 info)
450 {
451 	struct net *net = dev_net(skb->dev);
452 	const struct iphdr *iph = (const struct iphdr *)skb->data;
453 	struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
454 	struct xfrm_state *x;
455 
456 	switch (icmp_hdr(skb)->type) {
457 	case ICMP_DEST_UNREACH:
458 		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
459 			return 0;
460 		break;
461 	case ICMP_REDIRECT:
462 		break;
463 	default:
464 		return 0;
465 	}
466 
467 	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
468 			      ah->spi, IPPROTO_AH, AF_INET);
469 	if (!x)
470 		return 0;
471 
472 	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
473 		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_AH);
474 	else
475 		ipv4_redirect(skb, net, 0, IPPROTO_AH);
476 	xfrm_state_put(x);
477 
478 	return 0;
479 }
480 
481 static int ah_init_state(struct xfrm_state *x, struct netlink_ext_ack *extack)
482 {
483 	struct ah_data *ahp = NULL;
484 	struct xfrm_algo_desc *aalg_desc;
485 	struct crypto_ahash *ahash;
486 
487 	if (!x->aalg) {
488 		NL_SET_ERR_MSG(extack, "AH requires a state with an AUTH algorithm");
489 		goto error;
490 	}
491 
492 	if (x->encap) {
493 		NL_SET_ERR_MSG(extack, "AH is not compatible with encapsulation");
494 		goto error;
495 	}
496 
497 	ahp = kzalloc_obj(*ahp);
498 	if (!ahp)
499 		return -ENOMEM;
500 
501 	ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
502 	if (IS_ERR(ahash)) {
503 		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
504 		goto error;
505 	}
506 
507 	ahp->ahash = ahash;
508 	if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
509 				(x->aalg->alg_key_len + 7) / 8)) {
510 		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
511 		goto error;
512 	}
513 
514 	/*
515 	 * Lookup the algorithm description maintained by xfrm_algo,
516 	 * verify crypto transform properties, and store information
517 	 * we need for AH processing.  This lookup cannot fail here
518 	 * after a successful crypto_alloc_ahash().
519 	 */
520 	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
521 	BUG_ON(!aalg_desc);
522 
523 	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
524 	    crypto_ahash_digestsize(ahash)) {
525 		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
526 		goto error;
527 	}
528 
529 	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
530 	ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
531 
532 	if (x->props.flags & XFRM_STATE_ALIGN4)
533 		x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
534 						  ahp->icv_trunc_len);
535 	else
536 		x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
537 						  ahp->icv_trunc_len);
538 	if (x->props.mode == XFRM_MODE_TUNNEL)
539 		x->props.header_len += sizeof(struct iphdr);
540 	x->data = ahp;
541 
542 	return 0;
543 
544 error:
545 	if (ahp) {
546 		crypto_free_ahash(ahp->ahash);
547 		kfree(ahp);
548 	}
549 	return -EINVAL;
550 }
551 
552 static void ah_destroy(struct xfrm_state *x)
553 {
554 	struct ah_data *ahp = x->data;
555 
556 	if (!ahp)
557 		return;
558 
559 	crypto_free_ahash(ahp->ahash);
560 	kfree(ahp);
561 }
562 
563 static int ah4_rcv_cb(struct sk_buff *skb, int err)
564 {
565 	return 0;
566 }
567 
568 static const struct xfrm_type ah_type =
569 {
570 	.owner		= THIS_MODULE,
571 	.proto	     	= IPPROTO_AH,
572 	.flags		= XFRM_TYPE_REPLAY_PROT,
573 	.init_state	= ah_init_state,
574 	.destructor	= ah_destroy,
575 	.input		= ah_input,
576 	.output		= ah_output
577 };
578 
579 static struct xfrm4_protocol ah4_protocol = {
580 	.handler	=	xfrm4_rcv,
581 	.input_handler	=	xfrm_input,
582 	.cb_handler	=	ah4_rcv_cb,
583 	.err_handler	=	ah4_err,
584 	.priority	=	0,
585 };
586 
587 static int __init ah4_init(void)
588 {
589 	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
590 		pr_info("%s: can't add xfrm type\n", __func__);
591 		return -EAGAIN;
592 	}
593 	if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
594 		pr_info("%s: can't add protocol\n", __func__);
595 		xfrm_unregister_type(&ah_type, AF_INET);
596 		return -EAGAIN;
597 	}
598 	return 0;
599 }
600 
601 static void __exit ah4_fini(void)
602 {
603 	if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
604 		pr_info("%s: can't remove protocol\n", __func__);
605 	xfrm_unregister_type(&ah_type, AF_INET);
606 }
607 
608 module_init(ah4_init);
609 module_exit(ah4_fini);
610 MODULE_DESCRIPTION("IPv4 AH transformation library");
611 MODULE_LICENSE("GPL");
612 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
613