xref: /openbmc/linux/net/ipv4/ah4.c (revision 6a108a14) 
1 #include <crypto/hash.h>
2 #include <linux/err.h>
3 #include <linux/module.h>
4 #include <linux/slab.h>
5 #include <net/ip.h>
6 #include <net/xfrm.h>
7 #include <net/ah.h>
8 #include <linux/crypto.h>
9 #include <linux/pfkeyv2.h>
10 #include <linux/scatterlist.h>
11 #include <net/icmp.h>
12 #include <net/protocol.h>
13 
14 struct ah_skb_cb {
15 	struct xfrm_skb_cb xfrm;
16 	void *tmp;
17 };
18 
19 #define AH_SKB_CB(__skb) ((struct ah_skb_cb *)&((__skb)->cb[0]))
20 
21 static void *ah_alloc_tmp(struct crypto_ahash *ahash, int nfrags,
22 			  unsigned int size)
23 {
24 	unsigned int len;
25 
26 	len = size + crypto_ahash_digestsize(ahash) +
27 	      (crypto_ahash_alignmask(ahash) &
28 	       ~(crypto_tfm_ctx_alignment() - 1));
29 
30 	len = ALIGN(len, crypto_tfm_ctx_alignment());
31 
32 	len += sizeof(struct ahash_request) + crypto_ahash_reqsize(ahash);
33 	len = ALIGN(len, __alignof__(struct scatterlist));
34 
35 	len += sizeof(struct scatterlist) * nfrags;
36 
37 	return kmalloc(len, GFP_ATOMIC);
38 }
39 
40 static inline u8 *ah_tmp_auth(void *tmp, unsigned int offset)
41 {
42 	return tmp + offset;
43 }
44 
45 static inline u8 *ah_tmp_icv(struct crypto_ahash *ahash, void *tmp,
46 			     unsigned int offset)
47 {
48 	return PTR_ALIGN((u8 *)tmp + offset, crypto_ahash_alignmask(ahash) + 1);
49 }
50 
51 static inline struct ahash_request *ah_tmp_req(struct crypto_ahash *ahash,
52 					       u8 *icv)
53 {
54 	struct ahash_request *req;
55 
56 	req = (void *)PTR_ALIGN(icv + crypto_ahash_digestsize(ahash),
57 				crypto_tfm_ctx_alignment());
58 
59 	ahash_request_set_tfm(req, ahash);
60 
61 	return req;
62 }
63 
64 static inline struct scatterlist *ah_req_sg(struct crypto_ahash *ahash,
65 					     struct ahash_request *req)
66 {
67 	return (void *)ALIGN((unsigned long)(req + 1) +
68 			     crypto_ahash_reqsize(ahash),
69 			     __alignof__(struct scatterlist));
70 }
71 
72 /* Clear mutable options and find final destination to substitute
73  * into IP header for icv calculation. Options are already checked
74  * for validity, so paranoia is not required. */
75 
76 static int ip_clear_mutable_options(struct iphdr *iph, __be32 *daddr)
77 {
78 	unsigned char * optptr = (unsigned char*)(iph+1);
79 	int  l = iph->ihl*4 - sizeof(struct iphdr);
80 	int  optlen;
81 
82 	while (l > 0) {
83 		switch (*optptr) {
84 		case IPOPT_END:
85 			return 0;
86 		case IPOPT_NOOP:
87 			l--;
88 			optptr++;
89 			continue;
90 		}
91 		optlen = optptr[1];
92 		if (optlen<2 || optlen>l)
93 			return -EINVAL;
94 		switch (*optptr) {
95 		case IPOPT_SEC:
96 		case 0x85:	/* Some "Extended Security" crap. */
97 		case IPOPT_CIPSO:
98 		case IPOPT_RA:
99 		case 0x80|21:	/* RFC1770 */
100 			break;
101 		case IPOPT_LSRR:
102 		case IPOPT_SSRR:
103 			if (optlen < 6)
104 				return -EINVAL;
105 			memcpy(daddr, optptr+optlen-4, 4);
106 			/* Fall through */
107 		default:
108 			memset(optptr, 0, optlen);
109 		}
110 		l -= optlen;
111 		optptr += optlen;
112 	}
113 	return 0;
114 }
115 
116 static void ah_output_done(struct crypto_async_request *base, int err)
117 {
118 	u8 *icv;
119 	struct iphdr *iph;
120 	struct sk_buff *skb = base->data;
121 	struct xfrm_state *x = skb_dst(skb)->xfrm;
122 	struct ah_data *ahp = x->data;
123 	struct iphdr *top_iph = ip_hdr(skb);
124 	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
125 	int ihl = ip_hdrlen(skb);
126 
127 	iph = AH_SKB_CB(skb)->tmp;
128 	icv = ah_tmp_icv(ahp->ahash, iph, ihl);
129 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
130 
131 	top_iph->tos = iph->tos;
132 	top_iph->ttl = iph->ttl;
133 	top_iph->frag_off = iph->frag_off;
134 	if (top_iph->ihl != 5) {
135 		top_iph->daddr = iph->daddr;
136 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
137 	}
138 
139 	err = ah->nexthdr;
140 
141 	kfree(AH_SKB_CB(skb)->tmp);
142 	xfrm_output_resume(skb, err);
143 }
144 
145 static 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 
159 	ahp = x->data;
160 	ahash = ahp->ahash;
161 
162 	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
163 		goto out;
164 	nfrags = err;
165 
166 	skb_push(skb, -skb_network_offset(skb));
167 	ah = ip_auth_hdr(skb);
168 	ihl = ip_hdrlen(skb);
169 
170 	err = -ENOMEM;
171 	iph = ah_alloc_tmp(ahash, nfrags, ihl);
172 	if (!iph)
173 		goto out;
174 
175 	icv = ah_tmp_icv(ahash, iph, ihl);
176 	req = ah_tmp_req(ahash, icv);
177 	sg = ah_req_sg(ahash, req);
178 
179 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
180 
181 	top_iph = ip_hdr(skb);
182 
183 	iph->tos = top_iph->tos;
184 	iph->ttl = top_iph->ttl;
185 	iph->frag_off = top_iph->frag_off;
186 
187 	if (top_iph->ihl != 5) {
188 		iph->daddr = top_iph->daddr;
189 		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
190 		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
191 		if (err)
192 			goto out_free;
193 	}
194 
195 	ah->nexthdr = *skb_mac_header(skb);
196 	*skb_mac_header(skb) = IPPROTO_AH;
197 
198 	top_iph->tos = 0;
199 	top_iph->tot_len = htons(skb->len);
200 	top_iph->frag_off = 0;
201 	top_iph->ttl = 0;
202 	top_iph->check = 0;
203 
204 	ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
205 
206 	ah->reserved = 0;
207 	ah->spi = x->id.spi;
208 	ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);
209 
210 	sg_init_table(sg, nfrags);
211 	skb_to_sgvec(skb, sg, 0, skb->len);
212 
213 	ahash_request_set_crypt(req, sg, icv, skb->len);
214 	ahash_request_set_callback(req, 0, ah_output_done, skb);
215 
216 	AH_SKB_CB(skb)->tmp = iph;
217 
218 	err = crypto_ahash_digest(req);
219 	if (err) {
220 		if (err == -EINPROGRESS)
221 			goto out;
222 
223 		if (err == -EBUSY)
224 			err = NET_XMIT_DROP;
225 		goto out_free;
226 	}
227 
228 	memcpy(ah->auth_data, icv, ahp->icv_trunc_len);
229 
230 	top_iph->tos = iph->tos;
231 	top_iph->ttl = iph->ttl;
232 	top_iph->frag_off = iph->frag_off;
233 	if (top_iph->ihl != 5) {
234 		top_iph->daddr = iph->daddr;
235 		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
236 	}
237 
238 out_free:
239 	kfree(iph);
240 out:
241 	return err;
242 }
243 
244 static void ah_input_done(struct crypto_async_request *base, int err)
245 {
246 	u8 *auth_data;
247 	u8 *icv;
248 	struct iphdr *work_iph;
249 	struct sk_buff *skb = base->data;
250 	struct xfrm_state *x = xfrm_input_state(skb);
251 	struct ah_data *ahp = x->data;
252 	struct ip_auth_hdr *ah = ip_auth_hdr(skb);
253 	int ihl = ip_hdrlen(skb);
254 	int ah_hlen = (ah->hdrlen + 2) << 2;
255 
256 	work_iph = AH_SKB_CB(skb)->tmp;
257 	auth_data = ah_tmp_auth(work_iph, ihl);
258 	icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);
259 
260 	err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
261 	if (err)
262 		goto out;
263 
264 	skb->network_header += ah_hlen;
265 	memcpy(skb_network_header(skb), work_iph, ihl);
266 	__skb_pull(skb, ah_hlen + ihl);
267 	skb_set_transport_header(skb, -ihl);
268 
269 	err = ah->nexthdr;
270 out:
271 	kfree(AH_SKB_CB(skb)->tmp);
272 	xfrm_input_resume(skb, err);
273 }
274 
275 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
276 {
277 	int ah_hlen;
278 	int ihl;
279 	int nexthdr;
280 	int nfrags;
281 	u8 *auth_data;
282 	u8 *icv;
283 	struct sk_buff *trailer;
284 	struct crypto_ahash *ahash;
285 	struct ahash_request *req;
286 	struct scatterlist *sg;
287 	struct iphdr *iph, *work_iph;
288 	struct ip_auth_hdr *ah;
289 	struct ah_data *ahp;
290 	int err = -ENOMEM;
291 
292 	if (!pskb_may_pull(skb, sizeof(*ah)))
293 		goto out;
294 
295 	ah = (struct ip_auth_hdr *)skb->data;
296 	ahp = x->data;
297 	ahash = ahp->ahash;
298 
299 	nexthdr = ah->nexthdr;
300 	ah_hlen = (ah->hdrlen + 2) << 2;
301 
302 	if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
303 	    ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
304 		goto out;
305 
306 	if (!pskb_may_pull(skb, ah_hlen))
307 		goto out;
308 
309 	/* We are going to _remove_ AH header to keep sockets happy,
310 	 * so... Later this can change. */
311 	if (skb_cloned(skb) &&
312 	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
313 		goto out;
314 
315 	skb->ip_summed = CHECKSUM_NONE;
316 
317 
318 	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
319 		goto out;
320 	nfrags = err;
321 
322 	ah = (struct ip_auth_hdr *)skb->data;
323 	iph = ip_hdr(skb);
324 	ihl = ip_hdrlen(skb);
325 
326 	work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
327 	if (!work_iph)
328 		goto out;
329 
330 	auth_data = ah_tmp_auth(work_iph, ihl);
331 	icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
332 	req = ah_tmp_req(ahash, icv);
333 	sg = ah_req_sg(ahash, req);
334 
335 	memcpy(work_iph, iph, ihl);
336 	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
337 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
338 
339 	iph->ttl = 0;
340 	iph->tos = 0;
341 	iph->frag_off = 0;
342 	iph->check = 0;
343 	if (ihl > sizeof(*iph)) {
344 		__be32 dummy;
345 		err = ip_clear_mutable_options(iph, &dummy);
346 		if (err)
347 			goto out_free;
348 	}
349 
350 	skb_push(skb, ihl);
351 
352 	sg_init_table(sg, nfrags);
353 	skb_to_sgvec(skb, sg, 0, skb->len);
354 
355 	ahash_request_set_crypt(req, sg, icv, skb->len);
356 	ahash_request_set_callback(req, 0, ah_input_done, skb);
357 
358 	AH_SKB_CB(skb)->tmp = work_iph;
359 
360 	err = crypto_ahash_digest(req);
361 	if (err) {
362 		if (err == -EINPROGRESS)
363 			goto out;
364 
365 		if (err == -EBUSY)
366 			err = NET_XMIT_DROP;
367 		goto out_free;
368 	}
369 
370 	err = memcmp(icv, auth_data, ahp->icv_trunc_len) ? -EBADMSG: 0;
371 	if (err)
372 		goto out_free;
373 
374 	skb->network_header += ah_hlen;
375 	memcpy(skb_network_header(skb), work_iph, ihl);
376 	__skb_pull(skb, ah_hlen + ihl);
377 	skb_set_transport_header(skb, -ihl);
378 
379 	err = nexthdr;
380 
381 out_free:
382 	kfree (work_iph);
383 out:
384 	return err;
385 }
386 
387 static void ah4_err(struct sk_buff *skb, u32 info)
388 {
389 	struct net *net = dev_net(skb->dev);
390 	struct iphdr *iph = (struct iphdr *)skb->data;
391 	struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
392 	struct xfrm_state *x;
393 
394 	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
395 	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
396 		return;
397 
398 	x = xfrm_state_lookup(net, skb->mark, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
399 	if (!x)
400 		return;
401 	printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
402 	       ntohl(ah->spi), ntohl(iph->daddr));
403 	xfrm_state_put(x);
404 }
405 
406 static int ah_init_state(struct xfrm_state *x)
407 {
408 	struct ah_data *ahp = NULL;
409 	struct xfrm_algo_desc *aalg_desc;
410 	struct crypto_ahash *ahash;
411 
412 	if (!x->aalg)
413 		goto error;
414 
415 	if (x->encap)
416 		goto error;
417 
418 	ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
419 	if (!ahp)
420 		return -ENOMEM;
421 
422 	ahash = crypto_alloc_ahash(x->aalg->alg_name, 0, 0);
423 	if (IS_ERR(ahash))
424 		goto error;
425 
426 	ahp->ahash = ahash;
427 	if (crypto_ahash_setkey(ahash, x->aalg->alg_key,
428 				(x->aalg->alg_key_len + 7) / 8))
429 		goto error;
430 
431 	/*
432 	 * Lookup the algorithm description maintained by xfrm_algo,
433 	 * verify crypto transform properties, and store information
434 	 * we need for AH processing.  This lookup cannot fail here
435 	 * after a successful crypto_alloc_ahash().
436 	 */
437 	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
438 	BUG_ON(!aalg_desc);
439 
440 	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
441 	    crypto_ahash_digestsize(ahash)) {
442 		printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
443 		       x->aalg->alg_name, crypto_ahash_digestsize(ahash),
444 		       aalg_desc->uinfo.auth.icv_fullbits/8);
445 		goto error;
446 	}
447 
448 	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
449 	ahp->icv_trunc_len = x->aalg->alg_trunc_len/8;
450 
451 	BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
452 
453 	x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
454 					  ahp->icv_trunc_len);
455 	if (x->props.mode == XFRM_MODE_TUNNEL)
456 		x->props.header_len += sizeof(struct iphdr);
457 	x->data = ahp;
458 
459 	return 0;
460 
461 error:
462 	if (ahp) {
463 		crypto_free_ahash(ahp->ahash);
464 		kfree(ahp);
465 	}
466 	return -EINVAL;
467 }
468 
469 static void ah_destroy(struct xfrm_state *x)
470 {
471 	struct ah_data *ahp = x->data;
472 
473 	if (!ahp)
474 		return;
475 
476 	crypto_free_ahash(ahp->ahash);
477 	kfree(ahp);
478 }
479 
480 
481 static const struct xfrm_type ah_type =
482 {
483 	.description	= "AH4",
484 	.owner		= THIS_MODULE,
485 	.proto	     	= IPPROTO_AH,
486 	.flags		= XFRM_TYPE_REPLAY_PROT,
487 	.init_state	= ah_init_state,
488 	.destructor	= ah_destroy,
489 	.input		= ah_input,
490 	.output		= ah_output
491 };
492 
493 static const struct net_protocol ah4_protocol = {
494 	.handler	=	xfrm4_rcv,
495 	.err_handler	=	ah4_err,
496 	.no_policy	=	1,
497 	.netns_ok	=	1,
498 };
499 
500 static int __init ah4_init(void)
501 {
502 	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
503 		printk(KERN_INFO "ip ah init: can't add xfrm type\n");
504 		return -EAGAIN;
505 	}
506 	if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
507 		printk(KERN_INFO "ip ah init: can't add protocol\n");
508 		xfrm_unregister_type(&ah_type, AF_INET);
509 		return -EAGAIN;
510 	}
511 	return 0;
512 }
513 
514 static void __exit ah4_fini(void)
515 {
516 	if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
517 		printk(KERN_INFO "ip ah close: can't remove protocol\n");
518 	if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
519 		printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
520 }
521 
522 module_init(ah4_init);
523 module_exit(ah4_fini);
524 MODULE_LICENSE("GPL");
525 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);
526