xref: /kernel/linux/linux-6.6/net/ipv4/ah4.c (revision 62306a36) 
1// SPDX-License-Identifier: GPL-2.0-only
2#define pr_fmt(fmt) "IPsec: " fmt
3
4#include <crypto/algapi.h>
5#include <crypto/hash.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
18struct 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
25static 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	      (crypto_ahash_alignmask(ahash) &
32	       ~(crypto_tfm_ctx_alignment() - 1));
33
34	len = ALIGN(len, crypto_tfm_ctx_alignment());
35
36	len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
37	len = ALIGN(len, __alignof__(struct scatterlist));
38
39	len += sizeof(struct scatterlist) * nfrags;
40
41	return kmalloc(len, GFP_ATOMIC);
42}
43
44static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
45{
46	return tmp + offset;
47}
48
49static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
50			     unsigned int offset)
51{
52	return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
53}
54
55static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
56					       u8 *icv)
57{
58	struct ahash_request *req;
59
60	req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
61				crypto_tfm_ctx_alignment());
62
63	ahash_request_set_tfm(req, ahash);
64
65	return req;
66}
67
68static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
69					     struct ahash_request *req)
70{
71	return (void *)ALIGN((unsigned long)(req + 1) +
72			     crypto_ahash_reqsize(ahash),
73			     __alignof__(struct scatterlist));
74}
75
76/* Clear mutable options and find final destination to substitute
77 * into IP header for icv calculation. Options are already checked
78 * for validity, so paranoia is not required. */
79
80static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
81{
82	unsigned char *optptr = (unsigned char *)(iph+1);
83	int  l = iph->ihl*4 - sizeof(struct iphdr);
84	int  optlen;
85
86	while (l > 0) {
87		switch (*optptr) {
88		case IPOPT_END:
89			return 0;
90		case IPOPT_NOOP:
91			l--;
92			optptr++;
93			continue;
94		}
95		optlen = optptr[1];
96		if (optlen<2 || optlen>l)
97			return -EINVAL;
98		switch (*optptr) {
99		case IPOPT_SEC:
100		case 0x85:	/* Some "Extended Security" crap. */
101		case IPOPT_CIPSO:
102		case IPOPT_RA:
103		case 0x80|21:	/* RFC1770 */
104			break;
105		case IPOPT_LSRR:
106		case IPOPT_SSRR:
107			if (optlen < 6)
108				return -EINVAL;
109			memcpy(daddr, optptr+optlen-4, 4);
110			fallthrough;
111		default:
112			memset(optptr, 0, optlen);
113		}
114		l -= optlen;
115		optptr += optlen;
116	}
117	return 0;
118}
119
120static void ah_output_done(void *data, int err)
121{
122	u8 *icv;
123	struct iphdr *iph;
124	struct sk_buff *skb = data;
125	struct xfrm_state *x = skb_dst(skb)->xfrm;
126	struct ah_data *ahp = x->data;
127	struct iphdr *top_iph = ip_hdr(skb);
128	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
129	int ihl = ip_hdrlen(skb);
130
131	iph = AH_SKB_CB(skb)->tmp;
132	icv = ah_tmp_icv(ahp->ahash, iph, ihl);
133	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
134
135	top_iph->tos = iph->tos;
136	top_iph->ttl = iph->ttl;
137	top_iph->frag_off = iph->frag_off;
138	if (top_iph->ihl != 5) {
139		top_iph->daddr = iph->daddr;
140		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
141	}
142
143	kfree(AH_SKB_CB(skb)->tmp);
144	xfrm_output_resume(skb->sk, skb, err);
145}
146
147static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
148{
149	int err;
150	int nfrags;
151	int ihl;
152	u8 *icv;
153	struct sk_buff *trailer;
154	struct crypto_ahash *ahash;
155	struct ahash_request *req;
156	struct scatterlist *sg;
157	struct iphdr *iph, *top_iph;
158	struct ip_auth_hdr *ah;
159	struct ah_data *ahp;
160	int seqhi_len = 0;
161	__be32 *seqhi;
162	int sglists = 0;
163	struct scatterlist *seqhisg;
164
165	ahp = x->data;
166	ahash = ahp->ahash;
167
168	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
169		goto out;
170	nfrags = err;
171
172	skb_push(skb, -skb_network_offset(skb));
173	ah = ip_auth_hdr(skb);
174	ihl = ip_hdrlen(skb);
175
176	if (x->props.flags & XFRM_STATE_ESN) {
177		sglists = 1;
178		seqhi_len = sizeof(*seqhi);
179	}
180	err = -ENOMEM;
181	iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
182	if (!iph)
183		goto out;
184	seqhi = (__be32 *)((char *)iph + ihl);
185	icv = ah_tmp_icv(ahash, seqhi, seqhi_len);
186	req = ah_tmp_req(ahash, icv);
187	sg = ah_req_sg(ahash, req);
188	seqhisg = sg + nfrags;
189
190	memset(ah->auth_data, 0, ahp->icv_trunc_len);
191
192	top_iph = ip_hdr(skb);
193
194	iph->tos = top_iph->tos;
195	iph->ttl = top_iph->ttl;
196	iph->frag_off = top_iph->frag_off;
197
198	if (top_iph->ihl != 5) {
199		iph->daddr = top_iph->daddr;
200		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
201		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
202		if (err)
203			goto out_free;
204	}
205
206	ah->nexthdr = *skb_mac_header(skb);
207	*skb_mac_header(skb) = IPPROTO_AH;
208
209	top_iph->tos = 0;
210	top_iph->tot_len = htons(skb->len);
211	top_iph->frag_off = 0;
212	top_iph->ttl = 0;
213	top_iph->check = 0;
214
215	if (x->props.flags & XFRM_STATE_ALIGN4)
216		ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
217	else
218		ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
219
220	ah->reserved = 0;
221	ah->spi = x->id.spi;
222	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
223
224	sg_init_table(sg, nfrags + sglists);
225	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
226	if (unlikely(err < 0))
227		goto out_free;
228
229	if (x->props.flags & XFRM_STATE_ESN) {
230		/* Attach seqhi sg right after packet payload */
231		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
232		sg_set_buf(seqhisg, seqhi, seqhi_len);
233	}
234	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
235	ahash_request_set_callback(req, 0, ah_output_done, skb);
236
237	AH_SKB_CB(skb)->tmp = iph;
238
239	err = crypto_ahash_digest(req);
240	if (err) {
241		if (err == -EINPROGRESS)
242			goto out;
243
244		if (err == -ENOSPC)
245			err = NET_XMIT_DROP;
246		goto out_free;
247	}
248
249	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
250
251	top_iph->tos = iph->tos;
252	top_iph->ttl = iph->ttl;
253	top_iph->frag_off = iph->frag_off;
254	if (top_iph->ihl != 5) {
255		top_iph->daddr = iph->daddr;
256		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
257	}
258
259out_free:
260	kfree(iph);
261out:
262	return err;
263}
264
265static void ah_input_done(void *data, int err)
266{
267	u8 *auth_data;
268	u8 *icv;
269	struct iphdr *work_iph;
270	struct sk_buff *skb = data;
271	struct xfrm_state *x = xfrm_input_state(skb);
272	struct ah_data *ahp = x->data;
273	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
274	int ihl = ip_hdrlen(skb);
275	int ah_hlen = (ah->hdrlen + 2) << 2;
276
277	if (err)
278		goto out;
279
280	work_iph = AH_SKB_CB(skb)->tmp;
281	auth_data = ah_tmp_auth(work_iph, ihl);
282	icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
283
284	err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
285	if (err)
286		goto out;
287
288	err = ah->nexthdr;
289
290	skb->network_header += ah_hlen;
291	memcpy(skb_network_header(skb), work_iph, ihl);
292	__skb_pull(skb, ah_hlen + ihl);
293
294	if (x->props.mode == XFRM_MODE_TUNNEL)
295		skb_reset_transport_header(skb);
296	else
297		skb_set_transport_header(skb, -ihl);
298out:
299	kfree(AH_SKB_CB(skb)->tmp);
300	xfrm_input_resume(skb, err);
301}
302
303static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
304{
305	int ah_hlen;
306	int ihl;
307	int nexthdr;
308	int nfrags;
309	u8 *auth_data;
310	u8 *icv;
311	struct sk_buff *trailer;
312	struct crypto_ahash *ahash;
313	struct ahash_request *req;
314	struct scatterlist *sg;
315	struct iphdr *iph, *work_iph;
316	struct ip_auth_hdr *ah;
317	struct ah_data *ahp;
318	int err = -ENOMEM;
319	int seqhi_len = 0;
320	__be32 *seqhi;
321	int sglists = 0;
322	struct scatterlist *seqhisg;
323
324	if (!pskb_may_pull(skb, sizeof(*ah)))
325		goto out;
326
327	ah = (struct ip_auth_hdr *)skb->data;
328	ahp = x->data;
329	ahash = ahp->ahash;
330
331	nexthdr = ah->nexthdr;
332	ah_hlen = (ah->hdrlen + 2) << 2;
333
334	if (x->props.flags & XFRM_STATE_ALIGN4) {
335		if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
336		    ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
337			goto out;
338	} else {
339		if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
340		    ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
341			goto out;
342	}
343
344	if (!pskb_may_pull(skb, ah_hlen))
345		goto out;
346
347	/* We are going to _remove_ AH header to keep sockets happy,
348	 * so... Later this can change. */
349	if (skb_unclone(skb, GFP_ATOMIC))
350		goto out;
351
352	skb->ip_summed = CHECKSUM_NONE;
353
354
355	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
356		goto out;
357	nfrags = err;
358
359	ah = (struct ip_auth_hdr *)skb->data;
360	iph = ip_hdr(skb);
361	ihl = ip_hdrlen(skb);
362
363	if (x->props.flags & XFRM_STATE_ESN) {
364		sglists = 1;
365		seqhi_len = sizeof(*seqhi);
366	}
367
368	work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
369				ahp->icv_trunc_len + seqhi_len);
370	if (!work_iph) {
371		err = -ENOMEM;
372		goto out;
373	}
374
375	seqhi = (__be32 *)((char *)work_iph + ihl);
376	auth_data = ah_tmp_auth(seqhi, seqhi_len);
377	icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
378	req = ah_tmp_req(ahash, icv);
379	sg = ah_req_sg(ahash, req);
380	seqhisg = sg + nfrags;
381
382	memcpy(work_iph, iph, ihl);
383	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
384	memset(ah->auth_data, 0, ahp->icv_trunc_len);
385
386	iph->ttl = 0;
387	iph->tos = 0;
388	iph->frag_off = 0;
389	iph->check = 0;
390	if (ihl > sizeof(*iph)) {
391		__be32 dummy;
392		err = ip_clear_mutable_options(iph, &dummy);
393		if (err)
394			goto out_free;
395	}
396
397	skb_push(skb, ihl);
398
399	sg_init_table(sg, nfrags + sglists);
400	err = skb_to_sgvec_nomark(skb, sg, 0, skb->len);
401	if (unlikely(err < 0))
402		goto out_free;
403
404	if (x->props.flags & XFRM_STATE_ESN) {
405		/* Attach seqhi sg right after packet payload */
406		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
407		sg_set_buf(seqhisg, seqhi, seqhi_len);
408	}
409	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
410	ahash_request_set_callback(req, 0, ah_input_done, skb);
411
412	AH_SKB_CB(skb)->tmp = work_iph;
413
414	err = crypto_ahash_digest(req);
415	if (err) {
416		if (err == -EINPROGRESS)
417			goto out;
418
419		goto out_free;
420	}
421
422	err = crypto_memneq(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG : 0;
423	if (err)
424		goto out_free;
425
426	skb->network_header += ah_hlen;
427	memcpy(skb_network_header(skb), work_iph, ihl);
428	__skb_pull(skb, ah_hlen + ihl);
429	if (x->props.mode == XFRM_MODE_TUNNEL)
430		skb_reset_transport_header(skb);
431	else
432		skb_set_transport_header(skb, -ihl);
433
434	err = nexthdr;
435
436out_free:
437	kfree (work_iph);
438out:
439	return err;
440}
441
442static int ah4_err(struct sk_buff *skb, u32 info)
443{
444	struct net *net = dev_net(skb->dev);
445	const struct iphdr *iph = (const struct iphdr *)skb->data;
446	struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
447	struct xfrm_state *x;
448
449	switch (icmp_hdr(skb)->type) {
450	case ICMP_DEST_UNREACH:
451		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
452			return 0;
453		break;
454	case ICMP_REDIRECT:
455		break;
456	default:
457		return 0;
458	}
459
460	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
461			      ah->spi, IPPROTO_AH, AF_INET);
462	if (!x)
463		return 0;
464
465	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
466		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_AH);
467	else
468		ipv4_redirect(skb, net, 0, IPPROTO_AH);
469	xfrm_state_put(x);
470
471	return 0;
472}
473
474static int ah_init_state(struct xfrm_state *x, struct netlink_ext_ack *extack)
475{
476	struct ah_data *ahp = NULL;
477	struct xfrm_algo_desc *aalg_desc;
478	struct crypto_ahash *ahash;
479
480	if (!x->aalg) {
481		NL_SET_ERR_MSG(extack, "AH requires a state with an AUTH algorithm");
482		goto error;
483	}
484
485	if (x->encap) {
486		NL_SET_ERR_MSG(extack, "AH is not compatible with encapsulation");
487		goto error;
488	}
489
490	ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
491	if (!ahp)
492		return -ENOMEM;
493
494	ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
495	if (IS_ERR(ahash)) {
496		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
497		goto error;
498	}
499
500	ahp->ahash = ahash;
501	if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
502				(x->aalg->alg_key_len + 7) / 8)) {
503		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
504		goto error;
505	}
506
507	/*
508	 * Lookup the algorithm description maintained by xfrm_algo,
509	 * verify crypto transform properties, and store information
510	 * we need for AH processing.  This lookup cannot fail here
511	 * after a successful crypto_alloc_ahash().
512	 */
513	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
514	BUG_ON(!aalg_desc);
515
516	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
517	    crypto_ahash_digestsize(ahash)) {
518		NL_SET_ERR_MSG(extack, "Kernel was unable to initialize cryptographic operations");
519		goto error;
520	}
521
522	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
523	ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
524
525	if (x->props.flags & XFRM_STATE_ALIGN4)
526		x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
527						  ahp->icv_trunc_len);
528	else
529		x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
530						  ahp->icv_trunc_len);
531	if (x->props.mode == XFRM_MODE_TUNNEL)
532		x->props.header_len += sizeof(struct iphdr);
533	x->data = ahp;
534
535	return 0;
536
537error:
538	if (ahp) {
539		crypto_free_ahash(ahp->ahash);
540		kfree(ahp);
541	}
542	return -EINVAL;
543}
544
545static void ah_destroy(struct xfrm_state *x)
546{
547	struct ah_data *ahp = x->data;
548
549	if (!ahp)
550		return;
551
552	crypto_free_ahash(ahp->ahash);
553	kfree(ahp);
554}
555
556static int ah4_rcv_cb(struct sk_buff *skb, int err)
557{
558	return 0;
559}
560
561static const struct xfrm_type ah_type =
562{
563	.owner		= THIS_MODULE,
564	.proto	     	= IPPROTO_AH,
565	.flags		= XFRM_TYPE_REPLAY_PROT,
566	.init_state	= ah_init_state,
567	.destructor	= ah_destroy,
568	.input		= ah_input,
569	.output		= ah_output
570};
571
572static struct xfrm4_protocol ah4_protocol = {
573	.handler	=	xfrm4_rcv,
574	.input_handler	=	xfrm_input,
575	.cb_handler	=	ah4_rcv_cb,
576	.err_handler	=	ah4_err,
577	.priority	=	0,
578};
579
580static int __init ah4_init(void)
581{
582	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
583		pr_info("%s: can't add xfrm type\n", __func__);
584		return -EAGAIN;
585	}
586	if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
587		pr_info("%s: can't add protocol\n", __func__);
588		xfrm_unregister_type(&ah_type, AF_INET);
589		return -EAGAIN;
590	}
591	return 0;
592}
593
594static void __exit ah4_fini(void)
595{
596	if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
597		pr_info("%s: can't remove protocol\n", __func__);
598	xfrm_unregister_type(&ah_type, AF_INET);
599}
600
601module_init(ah4_init);
602module_exit(ah4_fini);
603MODULE_LICENSE("GPL");
604MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
605