xref: /openbmc/linux/net/ipv6/ah6.c (revision 4bedea94) 
1 /*
2  * Copyright (C)2002 USAGI/WIDE Project
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
17  *
18  * Authors
19  *
20  *	Mitsuru KANDA @USAGI       : IPv6 Support
21  * 	Kazunori MIYAZAWA @USAGI   :
22  * 	Kunihiro Ishiguro <kunihiro@ipinfusion.com>
23  *
24  * 	This file is derived from net/ipv4/ah.c.
25  */
26 
27 #include <linux/config.h>
28 #include <linux/module.h>
29 #include <net/ip.h>
30 #include <net/ah.h>
31 #include <linux/crypto.h>
32 #include <linux/pfkeyv2.h>
33 #include <linux/string.h>
34 #include <net/icmp.h>
35 #include <net/ipv6.h>
36 #include <net/xfrm.h>
37 #include <asm/scatterlist.h>
38 
39 static int zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
40 {
41 	u8 *opt = (u8 *)opthdr;
42 	int len = ipv6_optlen(opthdr);
43 	int off = 0;
44 	int optlen = 0;
45 
46 	off += 2;
47 	len -= 2;
48 
49 	while (len > 0) {
50 
51 		switch (opt[off]) {
52 
53 		case IPV6_TLV_PAD0:
54 			optlen = 1;
55 			break;
56 		default:
57 			if (len < 2)
58 				goto bad;
59 			optlen = opt[off+1]+2;
60 			if (len < optlen)
61 				goto bad;
62 			if (opt[off] & 0x20)
63 				memset(&opt[off+2], 0, opt[off+1]);
64 			break;
65 		}
66 
67 		off += optlen;
68 		len -= optlen;
69 	}
70 	if (len == 0)
71 		return 1;
72 
73 bad:
74 	return 0;
75 }
76 
77 /**
78  *	ipv6_rearrange_rthdr - rearrange IPv6 routing header
79  *	@iph: IPv6 header
80  *	@rthdr: routing header
81  *
82  *	Rearrange the destination address in @iph and the addresses in @rthdr
83  *	so that they appear in the order they will at the final destination.
84  *	See Appendix A2 of RFC 2402 for details.
85  */
86 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
87 {
88 	int segments, segments_left;
89 	struct in6_addr *addrs;
90 	struct in6_addr final_addr;
91 
92 	segments_left = rthdr->segments_left;
93 	if (segments_left == 0)
94 		return;
95 	rthdr->segments_left = 0;
96 
97 	/* The value of rthdr->hdrlen has been verified either by the system
98 	 * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
99 	 * packets.  So we can assume that it is even and that segments is
100 	 * greater than or equal to segments_left.
101 	 *
102 	 * For the same reason we can assume that this option is of type 0.
103 	 */
104 	segments = rthdr->hdrlen >> 1;
105 
106 	addrs = ((struct rt0_hdr *)rthdr)->addr;
107 	ipv6_addr_copy(&final_addr, addrs + segments - 1);
108 
109 	addrs += segments - segments_left;
110 	memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
111 
112 	ipv6_addr_copy(addrs, &iph->daddr);
113 	ipv6_addr_copy(&iph->daddr, &final_addr);
114 }
115 
116 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len)
117 {
118 	union {
119 		struct ipv6hdr *iph;
120 		struct ipv6_opt_hdr *opth;
121 		struct ipv6_rt_hdr *rth;
122 		char *raw;
123 	} exthdr = { .iph = iph };
124 	char *end = exthdr.raw + len;
125 	int nexthdr = iph->nexthdr;
126 
127 	exthdr.iph++;
128 
129 	while (exthdr.raw < end) {
130 		switch (nexthdr) {
131 		case NEXTHDR_HOP:
132 		case NEXTHDR_DEST:
133 			if (!zero_out_mutable_opts(exthdr.opth)) {
134 				LIMIT_NETDEBUG(printk(
135 					KERN_WARNING "overrun %sopts\n",
136 					nexthdr == NEXTHDR_HOP ?
137 						"hop" : "dest"));
138 				return -EINVAL;
139 			}
140 			break;
141 
142 		case NEXTHDR_ROUTING:
143 			ipv6_rearrange_rthdr(iph, exthdr.rth);
144 			break;
145 
146 		default :
147 			return 0;
148 		}
149 
150 		nexthdr = exthdr.opth->nexthdr;
151 		exthdr.raw += ipv6_optlen(exthdr.opth);
152 	}
153 
154 	return 0;
155 }
156 
157 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
158 {
159 	int err;
160 	int extlen;
161 	struct ipv6hdr *top_iph;
162 	struct ip_auth_hdr *ah;
163 	struct ah_data *ahp;
164 	u8 nexthdr;
165 	char tmp_base[8];
166 	struct {
167 		struct in6_addr daddr;
168 		char hdrs[0];
169 	} *tmp_ext;
170 
171 	top_iph = (struct ipv6hdr *)skb->data;
172 	top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
173 
174 	nexthdr = *skb->nh.raw;
175 	*skb->nh.raw = IPPROTO_AH;
176 
177 	/* When there are no extension headers, we only need to save the first
178 	 * 8 bytes of the base IP header.
179 	 */
180 	memcpy(tmp_base, top_iph, sizeof(tmp_base));
181 
182 	tmp_ext = NULL;
183 	extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
184 	if (extlen) {
185 		extlen += sizeof(*tmp_ext);
186 		tmp_ext = kmalloc(extlen, GFP_ATOMIC);
187 		if (!tmp_ext) {
188 			err = -ENOMEM;
189 			goto error;
190 		}
191 		memcpy(tmp_ext, &top_iph->daddr, extlen);
192 		err = ipv6_clear_mutable_options(top_iph,
193 						 extlen - sizeof(*tmp_ext) +
194 						 sizeof(*top_iph));
195 		if (err)
196 			goto error_free_iph;
197 	}
198 
199 	ah = (struct ip_auth_hdr *)skb->h.raw;
200 	ah->nexthdr = nexthdr;
201 
202 	top_iph->priority    = 0;
203 	top_iph->flow_lbl[0] = 0;
204 	top_iph->flow_lbl[1] = 0;
205 	top_iph->flow_lbl[2] = 0;
206 	top_iph->hop_limit   = 0;
207 
208 	ahp = x->data;
209 	ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) +
210 				   ahp->icv_trunc_len) >> 2) - 2;
211 
212 	ah->reserved = 0;
213 	ah->spi = x->id.spi;
214 	ah->seq_no = htonl(++x->replay.oseq);
215 	ahp->icv(ahp, skb, ah->auth_data);
216 
217 	err = 0;
218 
219 	memcpy(top_iph, tmp_base, sizeof(tmp_base));
220 	if (tmp_ext) {
221 		memcpy(&top_iph->daddr, tmp_ext, extlen);
222 error_free_iph:
223 		kfree(tmp_ext);
224 	}
225 
226 error:
227 	return err;
228 }
229 
230 static int ah6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
231 {
232 	/*
233 	 * Before process AH
234 	 * [IPv6][Ext1][Ext2][AH][Dest][Payload]
235 	 * |<-------------->| hdr_len
236 	 *
237 	 * To erase AH:
238 	 * Keeping copy of cleared headers. After AH processing,
239 	 * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
240 	 * header length. Then copy back the copy as long as hdr_len
241 	 * If destination header following AH exists, copy it into after [Ext2].
242 	 *
243 	 * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
244 	 * There is offset of AH before IPv6 header after the process.
245 	 */
246 
247 	struct ipv6_auth_hdr *ah;
248 	struct ah_data *ahp;
249 	unsigned char *tmp_hdr = NULL;
250 	u16 hdr_len;
251 	u16 ah_hlen;
252 	int nexthdr;
253 
254 	if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
255 		goto out;
256 
257 	/* We are going to _remove_ AH header to keep sockets happy,
258 	 * so... Later this can change. */
259 	if (skb_cloned(skb) &&
260 	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
261 		goto out;
262 
263 	hdr_len = skb->data - skb->nh.raw;
264 	ah = (struct ipv6_auth_hdr*)skb->data;
265 	ahp = x->data;
266 	nexthdr = ah->nexthdr;
267 	ah_hlen = (ah->hdrlen + 2) << 2;
268 
269         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
270             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
271                 goto out;
272 
273 	if (!pskb_may_pull(skb, ah_hlen))
274 		goto out;
275 
276 	tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
277 	if (!tmp_hdr)
278 		goto out;
279 	memcpy(tmp_hdr, skb->nh.raw, hdr_len);
280 	if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
281 		goto out;
282 	skb->nh.ipv6h->priority    = 0;
283 	skb->nh.ipv6h->flow_lbl[0] = 0;
284 	skb->nh.ipv6h->flow_lbl[1] = 0;
285 	skb->nh.ipv6h->flow_lbl[2] = 0;
286 	skb->nh.ipv6h->hop_limit   = 0;
287 
288         {
289 		u8 auth_data[MAX_AH_AUTH_LEN];
290 
291 		memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
292 		memset(ah->auth_data, 0, ahp->icv_trunc_len);
293 		skb_push(skb, skb->data - skb->nh.raw);
294 		ahp->icv(ahp, skb, ah->auth_data);
295 		if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
296 			LIMIT_NETDEBUG(
297 				printk(KERN_WARNING "ipsec ah authentication error\n"));
298 			x->stats.integrity_failed++;
299 			goto free_out;
300 		}
301 	}
302 
303 	skb->nh.raw = skb_pull(skb, ah_hlen);
304 	memcpy(skb->nh.raw, tmp_hdr, hdr_len);
305 	skb->nh.ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
306 	skb_pull(skb, hdr_len);
307 	skb->h.raw = skb->data;
308 
309 
310 	kfree(tmp_hdr);
311 
312 	return nexthdr;
313 
314 free_out:
315 	kfree(tmp_hdr);
316 out:
317 	return -EINVAL;
318 }
319 
320 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
321                     int type, int code, int offset, __u32 info)
322 {
323 	struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
324 	struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
325 	struct xfrm_state *x;
326 
327 	if (type != ICMPV6_DEST_UNREACH &&
328 	    type != ICMPV6_PKT_TOOBIG)
329 		return;
330 
331 	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
332 	if (!x)
333 		return;
334 
335 	NETDEBUG(printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/"
336 			"%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
337 	       ntohl(ah->spi), NIP6(iph->daddr)));
338 
339 	xfrm_state_put(x);
340 }
341 
342 static int ah6_init_state(struct xfrm_state *x)
343 {
344 	struct ah_data *ahp = NULL;
345 	struct xfrm_algo_desc *aalg_desc;
346 
347 	if (!x->aalg)
348 		goto error;
349 
350 	/* null auth can use a zero length key */
351 	if (x->aalg->alg_key_len > 512)
352 		goto error;
353 
354 	if (x->encap)
355 		goto error;
356 
357 	ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
358 	if (ahp == NULL)
359 		return -ENOMEM;
360 
361 	memset(ahp, 0, sizeof(*ahp));
362 
363 	ahp->key = x->aalg->alg_key;
364 	ahp->key_len = (x->aalg->alg_key_len+7)/8;
365 	ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
366 	if (!ahp->tfm)
367 		goto error;
368 	ahp->icv = ah_hmac_digest;
369 
370 	/*
371 	 * Lookup the algorithm description maintained by xfrm_algo,
372 	 * verify crypto transform properties, and store information
373 	 * we need for AH processing.  This lookup cannot fail here
374 	 * after a successful crypto_alloc_tfm().
375 	 */
376 	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
377 	BUG_ON(!aalg_desc);
378 
379 	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
380 	    crypto_tfm_alg_digestsize(ahp->tfm)) {
381 		printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
382 		       x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
383 		       aalg_desc->uinfo.auth.icv_fullbits/8);
384 		goto error;
385 	}
386 
387 	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
388 	ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
389 
390 	BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
391 
392 	ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
393 	if (!ahp->work_icv)
394 		goto error;
395 
396 	x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
397 	if (x->props.mode)
398 		x->props.header_len += sizeof(struct ipv6hdr);
399 	x->data = ahp;
400 
401 	return 0;
402 
403 error:
404 	if (ahp) {
405 		if (ahp->work_icv)
406 			kfree(ahp->work_icv);
407 		if (ahp->tfm)
408 			crypto_free_tfm(ahp->tfm);
409 		kfree(ahp);
410 	}
411 	return -EINVAL;
412 }
413 
414 static void ah6_destroy(struct xfrm_state *x)
415 {
416 	struct ah_data *ahp = x->data;
417 
418 	if (!ahp)
419 		return;
420 
421 	if (ahp->work_icv) {
422 		kfree(ahp->work_icv);
423 		ahp->work_icv = NULL;
424 	}
425 	if (ahp->tfm) {
426 		crypto_free_tfm(ahp->tfm);
427 		ahp->tfm = NULL;
428 	}
429 	kfree(ahp);
430 }
431 
432 static struct xfrm_type ah6_type =
433 {
434 	.description	= "AH6",
435 	.owner		= THIS_MODULE,
436 	.proto	     	= IPPROTO_AH,
437 	.init_state	= ah6_init_state,
438 	.destructor	= ah6_destroy,
439 	.input		= ah6_input,
440 	.output		= ah6_output
441 };
442 
443 static struct inet6_protocol ah6_protocol = {
444 	.handler	=	xfrm6_rcv,
445 	.err_handler	=	ah6_err,
446 	.flags		=	INET6_PROTO_NOPOLICY,
447 };
448 
449 static int __init ah6_init(void)
450 {
451 	if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
452 		printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
453 		return -EAGAIN;
454 	}
455 
456 	if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
457 		printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
458 		xfrm_unregister_type(&ah6_type, AF_INET6);
459 		return -EAGAIN;
460 	}
461 
462 	return 0;
463 }
464 
465 static void __exit ah6_fini(void)
466 {
467 	if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
468 		printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
469 
470 	if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
471 		printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
472 
473 }
474 
475 module_init(ah6_init);
476 module_exit(ah6_fini);
477 
478 MODULE_LICENSE("GPL");
479