1#define pr_fmt(fmt) "IPsec: " fmt
2
3#include <crypto/hash.h>
4#include <linux/err.h>
5#include <linux/module.h>
6#include <linux/slab.h>
7#include <net/ip.h>
8#include <net/xfrm.h>
9#include <net/ah.h>
10#include <linux/crypto.h>
11#include <linux/pfkeyv2.h>
12#include <linux/scatterlist.h>
13#include <net/icmp.h>
14#include <net/protocol.h>
15
16struct ah_skb_cb {
17	struct xfrm_skb_cb xfrm;
18	void *tmp;
19};
20
21#define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
22
23static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
24			  unsigned int size)
25{
26	unsigned int len;
27
28	len = size + crypto_ahash_digestsize(ahash) +
29	      (crypto_ahash_alignmask(ahash) &
30	       ~(crypto_tfm_ctx_alignment() - 1));
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
42static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
43{
44	return tmp + offset;
45}
46
47static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
48			     unsigned int offset)
49{
50	return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
51}
52
53static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
54					       u8 *icv)
55{
56	struct ahash_request *req;
57
58	req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
59				crypto_tfm_ctx_alignment());
60
61	ahash_request_set_tfm(req, ahash);
62
63	return req;
64}
65
66static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
67					     struct ahash_request *req)
68{
69	return (void *)ALIGN((unsigned long)(req + 1) +
70			     crypto_ahash_reqsize(ahash),
71			     __alignof__(struct scatterlist));
72}
73
74/* Clear mutable options and find final destination to substitute
75 * into IP header for icv calculation. Options are already checked
76 * for validity, so paranoia is not required. */
77
78static int ip_clear_mutable_options(const struct iphdr *iph, __be32 *daddr)
79{
80	unsigned char *optptr = (unsigned char *)(iph+1);
81	int  l = iph->ihl*4 - sizeof(struct iphdr);
82	int  optlen;
83
84	while (l > 0) {
85		switch (*optptr) {
86		case IPOPT_END:
87			return 0;
88		case IPOPT_NOOP:
89			l--;
90			optptr++;
91			continue;
92		}
93		optlen = optptr[1];
94		if (optlen<2 || optlen>l)
95			return -EINVAL;
96		switch (*optptr) {
97		case IPOPT_SEC:
98		case 0x85:	/* Some "Extended Security" crap. */
99		case IPOPT_CIPSO:
100		case IPOPT_RA:
101		case 0x80|21:	/* RFC1770 */
102			break;
103		case IPOPT_LSRR:
104		case IPOPT_SSRR:
105			if (optlen < 6)
106				return -EINVAL;
107			memcpy(daddr, optptr+optlen-4, 4);
108			/* Fall through */
109		default:
110			memset(optptr, 0, optlen);
111		}
112		l -= optlen;
113		optptr += optlen;
114	}
115	return 0;
116}
117
118static void ah_output_done(struct crypto_async_request *base, int err)
119{
120	u8 *icv;
121	struct iphdr *iph;
122	struct sk_buff *skb = base->data;
123	struct xfrm_state *x = skb_dst(skb)->xfrm;
124	struct ah_data *ahp = x->data;
125	struct iphdr *top_iph = ip_hdr(skb);
126	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
127	int ihl = ip_hdrlen(skb);
128
129	iph = AH_SKB_CB(skb)->tmp;
130	icv = ah_tmp_icv(ahp->ahash, iph, ihl);
131	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
132
133	top_iph->tos = iph->tos;
134	top_iph->ttl = iph->ttl;
135	top_iph->frag_off = iph->frag_off;
136	if (top_iph->ihl != 5) {
137		top_iph->daddr = iph->daddr;
138		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
139	}
140
141	kfree(AH_SKB_CB(skb)->tmp);
142	xfrm_output_resume(skb, err);
143}
144
145static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
146{
147	int err;
148	int nfrags;
149	int ihl;
150	u8 *icv;
151	struct sk_buff *trailer;
152	struct crypto_ahash *ahash;
153	struct ahash_request *req;
154	struct scatterlist *sg;
155	struct iphdr *iph, *top_iph;
156	struct ip_auth_hdr *ah;
157	struct ah_data *ahp;
158	int seqhi_len = 0;
159	__be32 *seqhi;
160	int sglists = 0;
161	struct scatterlist *seqhisg;
162
163	ahp = x->data;
164	ahash = ahp->ahash;
165
166	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
167		goto out;
168	nfrags = err;
169
170	skb_push(skb, -skb_network_offset(skb));
171	ah = ip_auth_hdr(skb);
172	ihl = ip_hdrlen(skb);
173
174	if (x->props.flags & XFRM_STATE_ESN) {
175		sglists = 1;
176		seqhi_len = sizeof(*seqhi);
177	}
178	err = -ENOMEM;
179	iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl + seqhi_len);
180	if (!iph)
181		goto out;
182	seqhi = (__be32 *)((char *)iph + ihl);
183	icv = ah_tmp_icv(ahash, seqhi, seqhi_len);
184	req = ah_tmp_req(ahash, icv);
185	sg = ah_req_sg(ahash, req);
186	seqhisg = sg + nfrags;
187
188	memset(ah->auth_data, 0, ahp->icv_trunc_len);
189
190	top_iph = ip_hdr(skb);
191
192	iph->tos = top_iph->tos;
193	iph->ttl = top_iph->ttl;
194	iph->frag_off = top_iph->frag_off;
195
196	if (top_iph->ihl != 5) {
197		iph->daddr = top_iph->daddr;
198		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
199		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
200		if (err)
201			goto out_free;
202	}
203
204	ah->nexthdr = *skb_mac_header(skb);
205	*skb_mac_header(skb) = IPPROTO_AH;
206
207	top_iph->tos = 0;
208	top_iph->tot_len = htons(skb->len);
209	top_iph->frag_off = 0;
210	top_iph->ttl = 0;
211	top_iph->check = 0;
212
213	if (x->props.flags & XFRM_STATE_ALIGN4)
214		ah->hdrlen  = (XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
215	else
216		ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
217
218	ah->reserved = 0;
219	ah->spi = x->id.spi;
220	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
221
222	sg_init_table(sg, nfrags + sglists);
223	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
224
225	if (x->props.flags & XFRM_STATE_ESN) {
226		/* Attach seqhi sg right after packet payload */
227		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
228		sg_set_buf(seqhisg, seqhi, seqhi_len);
229	}
230	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
231	ahash_request_set_callback(req, 0, ah_output_done, skb);
232
233	AH_SKB_CB(skb)->tmp = iph;
234
235	err = crypto_ahash_digest(req);
236	if (err) {
237		if (err == -EINPROGRESS)
238			goto out;
239
240		if (err == -EBUSY)
241			err = NET_XMIT_DROP;
242		goto out_free;
243	}
244
245	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
246
247	top_iph->tos = iph->tos;
248	top_iph->ttl = iph->ttl;
249	top_iph->frag_off = iph->frag_off;
250	if (top_iph->ihl != 5) {
251		top_iph->daddr = iph->daddr;
252		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
253	}
254
255out_free:
256	kfree(iph);
257out:
258	return err;
259}
260
261static void ah_input_done(struct crypto_async_request *base, int err)
262{
263	u8 *auth_data;
264	u8 *icv;
265	struct iphdr *work_iph;
266	struct sk_buff *skb = base->data;
267	struct xfrm_state *x = xfrm_input_state(skb);
268	struct ah_data *ahp = x->data;
269	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
270	int ihl = ip_hdrlen(skb);
271	int ah_hlen = (ah->hdrlen + 2) << 2;
272
273	work_iph = AH_SKB_CB(skb)->tmp;
274	auth_data = ah_tmp_auth(work_iph, ihl);
275	icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
276
277	err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
278	if (err)
279		goto out;
280
281	err = ah->nexthdr;
282
283	skb->network_header += ah_hlen;
284	memcpy(skb_network_header(skb), work_iph, ihl);
285	__skb_pull(skb, ah_hlen + ihl);
286
287	if (x->props.mode == XFRM_MODE_TUNNEL)
288		skb_reset_transport_header(skb);
289	else
290		skb_set_transport_header(skb, -ihl);
291out:
292	kfree(AH_SKB_CB(skb)->tmp);
293	xfrm_input_resume(skb, err);
294}
295
296static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
297{
298	int ah_hlen;
299	int ihl;
300	int nexthdr;
301	int nfrags;
302	u8 *auth_data;
303	u8 *icv;
304	struct sk_buff *trailer;
305	struct crypto_ahash *ahash;
306	struct ahash_request *req;
307	struct scatterlist *sg;
308	struct iphdr *iph, *work_iph;
309	struct ip_auth_hdr *ah;
310	struct ah_data *ahp;
311	int err = -ENOMEM;
312	int seqhi_len = 0;
313	__be32 *seqhi;
314	int sglists = 0;
315	struct scatterlist *seqhisg;
316
317	if (!pskb_may_pull(skb, sizeof(*ah)))
318		goto out;
319
320	ah = (struct ip_auth_hdr *)skb->data;
321	ahp = x->data;
322	ahash = ahp->ahash;
323
324	nexthdr = ah->nexthdr;
325	ah_hlen = (ah->hdrlen + 2) << 2;
326
327	if (x->props.flags & XFRM_STATE_ALIGN4) {
328		if (ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_full_len) &&
329		    ah_hlen != XFRM_ALIGN4(sizeof(*ah) + ahp->icv_trunc_len))
330			goto out;
331	} else {
332		if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
333		    ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
334			goto out;
335	}
336
337	if (!pskb_may_pull(skb, ah_hlen))
338		goto out;
339
340	/* We are going to _remove_ AH header to keep sockets happy,
341	 * so... Later this can change. */
342	if (skb_unclone(skb, GFP_ATOMIC))
343		goto out;
344
345	skb->ip_summed = CHECKSUM_NONE;
346
347
348	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
349		goto out;
350	nfrags = err;
351
352	ah = (struct ip_auth_hdr *)skb->data;
353	iph = ip_hdr(skb);
354	ihl = ip_hdrlen(skb);
355
356	if (x->props.flags & XFRM_STATE_ESN) {
357		sglists = 1;
358		seqhi_len = sizeof(*seqhi);
359	}
360
361	work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
362				ahp->icv_trunc_len + seqhi_len);
363	if (!work_iph)
364		goto out;
365
366	seqhi = (__be32 *)((char *)work_iph + ihl);
367	auth_data = ah_tmp_auth(seqhi, seqhi_len);
368	icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
369	req = ah_tmp_req(ahash, icv);
370	sg = ah_req_sg(ahash, req);
371	seqhisg = sg + nfrags;
372
373	memcpy(work_iph, iph, ihl);
374	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
375	memset(ah->auth_data, 0, ahp->icv_trunc_len);
376
377	iph->ttl = 0;
378	iph->tos = 0;
379	iph->frag_off = 0;
380	iph->check = 0;
381	if (ihl > sizeof(*iph)) {
382		__be32 dummy;
383		err = ip_clear_mutable_options(iph, &dummy);
384		if (err)
385			goto out_free;
386	}
387
388	skb_push(skb, ihl);
389
390	sg_init_table(sg, nfrags + sglists);
391	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
392
393	if (x->props.flags & XFRM_STATE_ESN) {
394		/* Attach seqhi sg right after packet payload */
395		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
396		sg_set_buf(seqhisg, seqhi, seqhi_len);
397	}
398	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
399	ahash_request_set_callback(req, 0, ah_input_done, skb);
400
401	AH_SKB_CB(skb)->tmp = work_iph;
402
403	err = crypto_ahash_digest(req);
404	if (err) {
405		if (err == -EINPROGRESS)
406			goto out;
407
408		goto out_free;
409	}
410
411	err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
412	if (err)
413		goto out_free;
414
415	skb->network_header += ah_hlen;
416	memcpy(skb_network_header(skb), work_iph, ihl);
417	__skb_pull(skb, ah_hlen + ihl);
418	if (x->props.mode == XFRM_MODE_TUNNEL)
419		skb_reset_transport_header(skb);
420	else
421		skb_set_transport_header(skb, -ihl);
422
423	err = nexthdr;
424
425out_free:
426	kfree (work_iph);
427out:
428	return err;
429}
430
431static int ah4_err(struct sk_buff *skb, u32 info)
432{
433	struct net *net = dev_net(skb->dev);
434	const struct iphdr *iph = (const struct iphdr *)skb->data;
435	struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
436	struct xfrm_state *x;
437
438	switch (icmp_hdr(skb)->type) {
439	case ICMP_DEST_UNREACH:
440		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
441			return 0;
442	case ICMP_REDIRECT:
443		break;
444	default:
445		return 0;
446	}
447
448	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
449			      ah->spi, IPPROTO_AH, AF_INET);
450	if (!x)
451		return 0;
452
453	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
454		ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_AH, 0);
455	else
456		ipv4_redirect(skb, net, 0, 0, IPPROTO_AH, 0);
457	xfrm_state_put(x);
458
459	return 0;
460}
461
462static int ah_init_state(struct xfrm_state *x)
463{
464	struct ah_data *ahp = NULL;
465	struct xfrm_algo_desc *aalg_desc;
466	struct crypto_ahash *ahash;
467
468	if (!x->aalg)
469		goto error;
470
471	if (x->encap)
472		goto error;
473
474	ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
475	if (!ahp)
476		return -ENOMEM;
477
478	ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
479	if (IS_ERR(ahash))
480		goto error;
481
482	ahp->ahash = ahash;
483	if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
484				(x->aalg->alg_key_len + 7) / 8))
485		goto error;
486
487	/*
488	 * Lookup the algorithm description maintained by xfrm_algo,
489	 * verify crypto transform properties, and store information
490	 * we need for AH processing.  This lookup cannot fail here
491	 * after a successful crypto_alloc_ahash().
492	 */
493	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
494	BUG_ON(!aalg_desc);
495
496	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
497	    crypto_ahash_digestsize(ahash)) {
498		pr_info("%s: %s digestsize %u != %hu\n",
499			__func__, x->aalg->alg_name,
500			crypto_ahash_digestsize(ahash),
501			aalg_desc->uinfo.auth.icv_fullbits / 8);
502		goto error;
503	}
504
505	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
506	ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
507
508	if (x->props.flags & XFRM_STATE_ALIGN4)
509		x->props.header_len = XFRM_ALIGN4(sizeof(struct ip_auth_hdr) +
510						  ahp->icv_trunc_len);
511	else
512		x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
513						  ahp->icv_trunc_len);
514	if (x->props.mode == XFRM_MODE_TUNNEL)
515		x->props.header_len += sizeof(struct iphdr);
516	x->data = ahp;
517
518	return 0;
519
520error:
521	if (ahp) {
522		crypto_free_ahash(ahp->ahash);
523		kfree(ahp);
524	}
525	return -EINVAL;
526}
527
528static void ah_destroy(struct xfrm_state *x)
529{
530	struct ah_data *ahp = x->data;
531
532	if (!ahp)
533		return;
534
535	crypto_free_ahash(ahp->ahash);
536	kfree(ahp);
537}
538
539static int ah4_rcv_cb(struct sk_buff *skb, int err)
540{
541	return 0;
542}
543
544static const struct xfrm_type ah_type =
545{
546	.description	= "AH4",
547	.owner		= THIS_MODULE,
548	.proto	     	= IPPROTO_AH,
549	.flags		= XFRM_TYPE_REPLAY_PROT,
550	.init_state	= ah_init_state,
551	.destructor	= ah_destroy,
552	.input		= ah_input,
553	.output		= ah_output
554};
555
556static struct xfrm4_protocol ah4_protocol = {
557	.handler	=	xfrm4_rcv,
558	.input_handler	=	xfrm_input,
559	.cb_handler	=	ah4_rcv_cb,
560	.err_handler	=	ah4_err,
561	.priority	=	0,
562};
563
564static int __init ah4_init(void)
565{
566	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
567		pr_info("%s: can't add xfrm type\n", __func__);
568		return -EAGAIN;
569	}
570	if (xfrm4_protocol_register(&ah4_protocol, IPPROTO_AH) < 0) {
571		pr_info("%s: can't add protocol\n", __func__);
572		xfrm_unregister_type(&ah_type, AF_INET);
573		return -EAGAIN;
574	}
575	return 0;
576}
577
578static void __exit ah4_fini(void)
579{
580	if (xfrm4_protocol_deregister(&ah4_protocol, IPPROTO_AH) < 0)
581		pr_info("%s: can't remove protocol\n", __func__);
582	if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
583		pr_info("%s: can't remove xfrm type\n", __func__);
584}
585
586module_init(ah4_init);
587module_exit(ah4_fini);
588MODULE_LICENSE("GPL");
589MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
590