xref: /linux/net/ipv4/ah4.c (revision 55f1b540d893da740a81200450014c45a8103f54) 
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 
128 	iph = AH_SKB_CB(skb)->tmp;
129 	icv = ah_tmp_icv(iph, ihl);
130 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
131 
132 	top_iph->tos = iph->tos;
133 	top_iph->ttl = iph->ttl;
134 	top_iph->frag_off = iph->frag_off;
135 	if (top_iph->ihl != 5) {
136 		top_iph->daddr = iph->daddr;
137 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
138 	}
139 
140 	kfree(AH_SKB_CB(skb)->tmp);
141 	xfrm_output_resume(skb->sk, skb, err);
142 }
143 
144 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
145 {
146 	int err;
147 	int nfrags;
148 	int ihl;
149 	u8 *icv;
150 	struct sk_buff *trailer;
151 	struct crypto_ahash *ahash;
152 	struct ahash_request *req;
153 	struct scatterlist *sg;
154 	struct iphdr *iph, *top_iph;
155 	struct ip_auth_hdr *ah;
156 	struct ah_data *ahp;
157 	int seqhi_len = 0;
158 	__be32 *seqhi;
159 	int sglists = 0;
160 	struct scatterlist *seqhisg;
161 
162 	ahp = x->data;
163 	ahash = ahp->ahash;
164 
165 	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
166 		goto out;
167 	nfrags = err;
168 
169 	skb_push(skb, -skb_network_offset(skb));
170 	ah = ip_auth_hdr(skb);
171 	ihl = ip_hdrlen(skb);
172 
173 	if (x->props.flags & XFRM_STATE_ESN) {
174 		sglists = 1;
175 		seqhi_len = sizeof(*seqhi);
176 	}
177 	err = -ENOMEM;
178 	iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
179 	if (!iph)
180 		goto out;
181 	seqhi = (__be32 *)((char *)iph + ihl);
182 	icv = ah_tmp_icv(seqhi, seqhi_len);
183 	req = ah_tmp_req(ahash, icv);
184 	sg = ah_req_sg(ahash, req);
185 	seqhisg = sg + nfrags;
186 
187 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
188 
189 	top_iph = ip_hdr(skb);
190 
191 	iph->tos = top_iph->tos;
192 	iph->ttl = top_iph->ttl;
193 	iph->frag_off = top_iph->frag_off;
194 
195 	if (top_iph->ihl != 5) {
196 		iph->daddr = top_iph->daddr;
197 		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
198 		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
199 		if (err)
200 			goto out_free;
201 	}
202 
203 	ah->nexthdr = *skb_mac_header(skb);
204 	*skb_mac_header(skb) = IPPROTO_AH;
205 
206 	top_iph->tos = 0;
207 	top_iph->tot_len = htons(skb->len);
208 	top_iph->frag_off = 0;
209 	top_iph->ttl = 0;
210 	top_iph->check = 0;
211 
212 	if (x->props.flags & XFRM_STATE_ALIGN4)
213 		ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
214 	else
215 		ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
216 
217 	ah->reserved = 0;
218 	ah->spi = x->id.spi;
219 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
220 
221 	sg_init_table(sg, nfrags + sglists);
222 	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
223 	if (unlikely(err < 0))
224 		goto out_free;
225 
226 	if (x->props.flags & XFRM_STATE_ESN) {
227 		/* Attach seqhi sg right after packet payload */
228 		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
229 		sg_set_buf(seqhisg, seqhi, seqhi_len);
230 	}
231 	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
232 	ahash_request_set_callback(req, 0, ah_output_done, skb);
233 
234 	AH_SKB_CB(skb)->tmp = iph;
235 
236 	err = crypto_ahash_digest(req);
237 	if (err) {
238 		if (err == -EINPROGRESS)
239 			goto out;
240 
241 		if (err == -ENOSPC)
242 			err = NET_XMIT_DROP;
243 		goto out_free;
244 	}
245 
246 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
247 
248 	top_iph->tos = iph->tos;
249 	top_iph->ttl = iph->ttl;
250 	top_iph->frag_off = iph->frag_off;
251 	if (top_iph->ihl != 5) {
252 		top_iph->daddr = iph->daddr;
253 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
254 	}
255 
256 out_free:
257 	kfree(iph);
258 out:
259 	return err;
260 }
261 
262 static void ah_input_done(void *data, int err)
263 {
264 	u8 *auth_data;
265 	u8 *icv;
266 	struct iphdr *work_iph;
267 	struct sk_buff *skb = data;
268 	struct xfrm_state *x = xfrm_input_state(skb);
269 	struct ah_data *ahp = x->data;
270 	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
271 	int ihl = ip_hdrlen(skb);
272 	int ah_hlen = (ah->hdrlen + 2) << 2;
273 
274 	if (err)
275 		goto out;
276 
277 	work_iph = AH_SKB_CB(skb)->tmp;
278 	auth_data = ah_tmp_auth(work_iph, ihl);
279 	icv = ah_tmp_icv(auth_data, ahp->icv_trunc_len);
280 
281 	err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
282 	if (err)
283 		goto out;
284 
285 	err = ah->nexthdr;
286 
287 	skb->network_header += ah_hlen;
288 	memcpy(skb_network_header(skb), work_iph, ihl);
289 	__skb_pull(skb, ah_hlen + ihl);
290 
291 	if (x->props.mode == XFRM_MODE_TUNNEL)
292 		skb_reset_transport_header(skb);
293 	else
294 		skb_set_transport_header(skb, -ihl);
295 out:
296 	kfree(AH_SKB_CB(skb)->tmp);
297 	xfrm_input_resume(skb, err);
298 }
299 
300 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
301 {
302 	int ah_hlen;
303 	int ihl;
304 	int nexthdr;
305 	int nfrags;
306 	u8 *auth_data;
307 	u8 *icv;
308 	struct sk_buff *trailer;
309 	struct crypto_ahash *ahash;
310 	struct ahash_request *req;
311 	struct scatterlist *sg;
312 	struct iphdr *iph, *work_iph;
313 	struct ip_auth_hdr *ah;
314 	struct ah_data *ahp;
315 	int err = -ENOMEM;
316 	int seqhi_len = 0;
317 	__be32 *seqhi;
318 	int sglists = 0;
319 	struct scatterlist *seqhisg;
320 
321 	if (!pskb_may_pull(skb, sizeof(*ah)))
322 		goto out;
323 
324 	ah = (struct ip_auth_hdr *)skb->data;
325 	ahp = x->data;
326 	ahash = ahp->ahash;
327 
328 	nexthdr = ah->nexthdr;
329 	ah_hlen = (ah->hdrlen + 2) << 2;
330 
331 	if (x->props.flags & XFRM_STATE_ALIGN4) {
332 		if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
333 		    ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
334 			goto out;
335 	} else {
336 		if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
337 		    ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
338 			goto out;
339 	}
340 
341 	if (!pskb_may_pull(skb, ah_hlen))
342 		goto out;
343 
344 	/* We are going to _remove_ AH header to keep sockets happy,
345 	 * so... Later this can change. */
346 	if (skb_unclone(skb, GFP_ATOMIC))
347 		goto out;
348 
349 	skb->ip_summed = CHECKSUM_NONE;
350 
351 
352 	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
353 		goto out;
354 	nfrags = err;
355 
356 	ah = (struct ip_auth_hdr *)skb->data;
357 	iph = ip_hdr(skb);
358 	ihl = ip_hdrlen(skb);
359 
360 	if (x->props.flags & XFRM_STATE_ESN) {
361 		sglists = 1;
362 		seqhi_len = sizeof(*seqhi);
363 	}
364 
365 	work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
366 				ahp->icv_trunc_len + seqhi_len);
367 	if (!work_iph) {
368 		err = -ENOMEM;
369 		goto out;
370 	}
371 
372 	seqhi = (__be32 *)((char *)work_iph + ihl);
373 	auth_data = ah_tmp_auth(seqhi, seqhi_len);
374 	icv = ah_tmp_icv(auth_data, ahp->icv_trunc_len);
375 	req = ah_tmp_req(ahash, icv);
376 	sg = ah_req_sg(ahash, req);
377 	seqhisg = sg + nfrags;
378 
379 	memcpy(work_iph, iph, ihl);
380 	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
381 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
382 
383 	iph->ttl = 0;
384 	iph->tos = 0;
385 	iph->frag_off = 0;
386 	iph->check = 0;
387 	if (ihl > sizeof(*iph)) {
388 		__be32 dummy;
389 		err = ip_clear_mutable_options(iph, &dummy);
390 		if (err)
391 			goto out_free;
392 	}
393 
394 	skb_push(skb, ihl);
395 
396 	sg_init_table(sg, nfrags + sglists);
397 	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
398 	if (unlikely(err < 0))
399 		goto out_free;
400 
401 	if (x->props.flags & XFRM_STATE_ESN) {
402 		/* Attach seqhi sg right after packet payload */
403 		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
404 		sg_set_buf(seqhisg, seqhi, seqhi_len);
405 	}
406 	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
407 	ahash_request_set_callback(req, 0, ah_input_done, skb);
408 
409 	AH_SKB_CB(skb)->tmp = work_iph;
410 
411 	err = crypto_ahash_digest(req);
412 	if (err) {
413 		if (err == -EINPROGRESS)
414 			goto out;
415 
416 		goto out_free;
417 	}
418 
419 	err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
420 	if (err)
421 		goto out_free;
422 
423 	skb->network_header += ah_hlen;
424 	memcpy(skb_network_header(skb), work_iph, ihl);
425 	__skb_pull(skb, ah_hlen + ihl);
426 	if (x->props.mode == XFRM_MODE_TUNNEL)
427 		skb_reset_transport_header(skb);
428 	else
429 		skb_set_transport_header(skb, -ihl);
430 
431 	err = nexthdr;
432 
433 out_free:
434 	kfree (work_iph);
435 out:
436 	return err;
437 }
438 
439 static int ah4_err(struct sk_buff *skb, u32 info)
440 {
441 	struct net *net = dev_net(skb->dev);
442 	const struct iphdr *iph = (const struct iphdr *)skb->data;
443 	struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
444 	struct xfrm_state *x;
445 
446 	switch (icmp_hdr(skb)->type) {
447 	case ICMP_DEST_UNREACH:
448 		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
449 			return 0;
450 		break;
451 	case ICMP_REDIRECT:
452 		break;
453 	default:
454 		return 0;
455 	}
456 
457 	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
458 			      ah->spi, IPPROTO_AH, AF_INET);
459 	if (!x)
460 		return 0;
461 
462 	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
463 		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_AH);
464 	else
465 		ipv4_redirect(skb, net, 0, IPPROTO_AH);
466 	xfrm_state_put(x);
467 
468 	return 0;
469 }
470 
471 static int ah_init_state(struct xfrm_state *x, struct netlink_ext_ack *extack)
472 {
473 	struct ah_data *ahp = NULL;
474 	struct xfrm_algo_desc *aalg_desc;
475 	struct crypto_ahash *ahash;
476 
477 	if (!x->aalg) {
478 		NL_SET_ERR_MSG(extack, "AH requires a state with an AUTH algorithm");
479 		goto error;
480 	}
481 
482 	if (x->encap) {
483 		NL_SET_ERR_MSG(extack, "AH is not compatible with encapsulation");
484 		goto error;
485 	}
486 
487 	ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
488 	if (!ahp)
489 		return -ENOMEM;
490 
491 	ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
492 	if (IS_ERR(ahash)) {
493 		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
494 		goto error;
495 	}
496 
497 	ahp->ahash = ahash;
498 	if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
499 				(x->aalg->alg_key_len + 7) / 8)) {
500 		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
501 		goto error;
502 	}
503 
504 	/*
505 	 * Lookup the algorithm description maintained by xfrm_algo,
506 	 * verify crypto transform properties, and store information
507 	 * we need for AH processing.  This lookup cannot fail here
508 	 * after a successful crypto_alloc_ahash().
509 	 */
510 	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
511 	BUG_ON(!aalg_desc);
512 
513 	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
514 	    crypto_ahash_digestsize(ahash)) {
515 		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
516 		goto error;
517 	}
518 
519 	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
520 	ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
521 
522 	if (x->props.flags & XFRM_STATE_ALIGN4)
523 		x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
524 						  ahp->icv_trunc_len);
525 	else
526 		x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
527 						  ahp->icv_trunc_len);
528 	if (x->props.mode == XFRM_MODE_TUNNEL)
529 		x->props.header_len += sizeof(struct iphdr);
530 	x->data = ahp;
531 
532 	return 0;
533 
534 error:
535 	if (ahp) {
536 		crypto_free_ahash(ahp->ahash);
537 		kfree(ahp);
538 	}
539 	return -EINVAL;
540 }
541 
542 static void ah_destroy(struct xfrm_state *x)
543 {
544 	struct ah_data *ahp = x->data;
545 
546 	if (!ahp)
547 		return;
548 
549 	crypto_free_ahash(ahp->ahash);
550 	kfree(ahp);
551 }
552 
553 static int ah4_rcv_cb(struct sk_buff *skb, int err)
554 {
555 	return 0;
556 }
557 
558 static const struct xfrm_type ah_type =
559 {
560 	.owner		= THIS_MODULE,
561 	.proto	     	= IPPROTO_AH,
562 	.flags		= XFRM_TYPE_REPLAY_PROT,
563 	.init_state	= ah_init_state,
564 	.destructor	= ah_destroy,
565 	.input		= ah_input,
566 	.output		= ah_output
567 };
568 
569 static struct xfrm4_protocol ah4_protocol = {
570 	.handler	=	xfrm4_rcv,
571 	.input_handler	=	xfrm_input,
572 	.cb_handler	=	ah4_rcv_cb,
573 	.err_handler	=	ah4_err,
574 	.priority	=	0,
575 };
576 
577 static int __init ah4_init(void)
578 {
579 	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
580 		pr_info("%s: can't add xfrm type\n", __func__);
581 		return -EAGAIN;
582 	}
583 	if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
584 		pr_info("%s: can't add protocol\n", __func__);
585 		xfrm_unregister_type(&ah_type, AF_INET);
586 		return -EAGAIN;
587 	}
588 	return 0;
589 }
590 
591 static void __exit ah4_fini(void)
592 {
593 	if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
594 		pr_info("%s: can't remove protocol\n", __func__);
595 	xfrm_unregister_type(&ah_type, AF_INET);
596 }
597 
598 module_init(ah4_init);
599 module_exit(ah4_fini);
600 MODULE_DESCRIPTION("IPv4 AH transformation library");
601 MODULE_LICENSE("GPL");
602 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
603