[SK_BUFF]: Introduce skb_network_header()
[linux-2.6.git] / net / ipv6 / ah6.c
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/module.h>
28 #include <net/ip.h>
29 #include <net/ah.h>
30 #include <linux/crypto.h>
31 #include <linux/pfkeyv2.h>
32 #include <linux/string.h>
33 #include <net/icmp.h>
34 #include <net/ipv6.h>
35 #include <net/protocol.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 #ifdef CONFIG_IPV6_MIP6
78 /**
79  *      ipv6_rearrange_destopt - rearrange IPv6 destination options header
80  *      @iph: IPv6 header
81  *      @destopt: destionation options header
82  */
83 static void ipv6_rearrange_destopt(struct ipv6hdr *iph, struct ipv6_opt_hdr *destopt)
84 {
85         u8 *opt = (u8 *)destopt;
86         int len = ipv6_optlen(destopt);
87         int off = 0;
88         int optlen = 0;
89
90         off += 2;
91         len -= 2;
92
93         while (len > 0) {
94
95                 switch (opt[off]) {
96
97                 case IPV6_TLV_PAD0:
98                         optlen = 1;
99                         break;
100                 default:
101                         if (len < 2)
102                                 goto bad;
103                         optlen = opt[off+1]+2;
104                         if (len < optlen)
105                                 goto bad;
106
107                         /* Rearrange the source address in @iph and the
108                          * addresses in home address option for final source.
109                          * See 11.3.2 of RFC 3775 for details.
110                          */
111                         if (opt[off] == IPV6_TLV_HAO) {
112                                 struct in6_addr final_addr;
113                                 struct ipv6_destopt_hao *hao;
114
115                                 hao = (struct ipv6_destopt_hao *)&opt[off];
116                                 if (hao->length != sizeof(hao->addr)) {
117                                         if (net_ratelimit())
118                                                 printk(KERN_WARNING "destopt hao: invalid header length: %u\n", hao->length);
119                                         goto bad;
120                                 }
121                                 ipv6_addr_copy(&final_addr, &hao->addr);
122                                 ipv6_addr_copy(&hao->addr, &iph->saddr);
123                                 ipv6_addr_copy(&iph->saddr, &final_addr);
124                         }
125                         break;
126                 }
127
128                 off += optlen;
129                 len -= optlen;
130         }
131         /* Note: ok if len == 0 */
132 bad:
133         return;
134 }
135 #endif
136
137 /**
138  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
139  *      @iph: IPv6 header
140  *      @rthdr: routing header
141  *
142  *      Rearrange the destination address in @iph and the addresses in @rthdr
143  *      so that they appear in the order they will at the final destination.
144  *      See Appendix A2 of RFC 2402 for details.
145  */
146 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
147 {
148         int segments, segments_left;
149         struct in6_addr *addrs;
150         struct in6_addr final_addr;
151
152         segments_left = rthdr->segments_left;
153         if (segments_left == 0)
154                 return;
155         rthdr->segments_left = 0;
156
157         /* The value of rthdr->hdrlen has been verified either by the system
158          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
159          * packets.  So we can assume that it is even and that segments is
160          * greater than or equal to segments_left.
161          *
162          * For the same reason we can assume that this option is of type 0.
163          */
164         segments = rthdr->hdrlen >> 1;
165
166         addrs = ((struct rt0_hdr *)rthdr)->addr;
167         ipv6_addr_copy(&final_addr, addrs + segments - 1);
168
169         addrs += segments - segments_left;
170         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
171
172         ipv6_addr_copy(addrs, &iph->daddr);
173         ipv6_addr_copy(&iph->daddr, &final_addr);
174 }
175
176 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len, int dir)
177 {
178         union {
179                 struct ipv6hdr *iph;
180                 struct ipv6_opt_hdr *opth;
181                 struct ipv6_rt_hdr *rth;
182                 char *raw;
183         } exthdr = { .iph = iph };
184         char *end = exthdr.raw + len;
185         int nexthdr = iph->nexthdr;
186
187         exthdr.iph++;
188
189         while (exthdr.raw < end) {
190                 switch (nexthdr) {
191                 case NEXTHDR_DEST:
192 #ifdef CONFIG_IPV6_MIP6
193                         if (dir == XFRM_POLICY_OUT)
194                                 ipv6_rearrange_destopt(iph, exthdr.opth);
195 #endif
196                 case NEXTHDR_HOP:
197                         if (!zero_out_mutable_opts(exthdr.opth)) {
198                                 LIMIT_NETDEBUG(
199                                         KERN_WARNING "overrun %sopts\n",
200                                         nexthdr == NEXTHDR_HOP ?
201                                                 "hop" : "dest");
202                                 return -EINVAL;
203                         }
204                         break;
205
206                 case NEXTHDR_ROUTING:
207                         ipv6_rearrange_rthdr(iph, exthdr.rth);
208                         break;
209
210                 default :
211                         return 0;
212                 }
213
214                 nexthdr = exthdr.opth->nexthdr;
215                 exthdr.raw += ipv6_optlen(exthdr.opth);
216         }
217
218         return 0;
219 }
220
221 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
222 {
223         int err;
224         int extlen;
225         struct ipv6hdr *top_iph;
226         struct ip_auth_hdr *ah;
227         struct ah_data *ahp;
228         u8 nexthdr;
229         char tmp_base[8];
230         struct {
231 #ifdef CONFIG_IPV6_MIP6
232                 struct in6_addr saddr;
233 #endif
234                 struct in6_addr daddr;
235                 char hdrs[0];
236         } *tmp_ext;
237
238         top_iph = (struct ipv6hdr *)skb->data;
239         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
240
241         nexthdr = *skb_network_header(skb);
242         *skb_network_header(skb) = IPPROTO_AH;
243
244         /* When there are no extension headers, we only need to save the first
245          * 8 bytes of the base IP header.
246          */
247         memcpy(tmp_base, top_iph, sizeof(tmp_base));
248
249         tmp_ext = NULL;
250         extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
251         if (extlen) {
252                 extlen += sizeof(*tmp_ext);
253                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
254                 if (!tmp_ext) {
255                         err = -ENOMEM;
256                         goto error;
257                 }
258 #ifdef CONFIG_IPV6_MIP6
259                 memcpy(tmp_ext, &top_iph->saddr, extlen);
260 #else
261                 memcpy(tmp_ext, &top_iph->daddr, extlen);
262 #endif
263                 err = ipv6_clear_mutable_options(top_iph,
264                                                  extlen - sizeof(*tmp_ext) +
265                                                  sizeof(*top_iph),
266                                                  XFRM_POLICY_OUT);
267                 if (err)
268                         goto error_free_iph;
269         }
270
271         ah = (struct ip_auth_hdr *)skb->h.raw;
272         ah->nexthdr = nexthdr;
273
274         top_iph->priority    = 0;
275         top_iph->flow_lbl[0] = 0;
276         top_iph->flow_lbl[1] = 0;
277         top_iph->flow_lbl[2] = 0;
278         top_iph->hop_limit   = 0;
279
280         ahp = x->data;
281         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) +
282                                    ahp->icv_trunc_len) >> 2) - 2;
283
284         ah->reserved = 0;
285         ah->spi = x->id.spi;
286         ah->seq_no = htonl(++x->replay.oseq);
287         xfrm_aevent_doreplay(x);
288         err = ah_mac_digest(ahp, skb, ah->auth_data);
289         if (err)
290                 goto error_free_iph;
291         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
292
293         err = 0;
294
295         memcpy(top_iph, tmp_base, sizeof(tmp_base));
296         if (tmp_ext) {
297 #ifdef CONFIG_IPV6_MIP6
298                 memcpy(&top_iph->saddr, tmp_ext, extlen);
299 #else
300                 memcpy(&top_iph->daddr, tmp_ext, extlen);
301 #endif
302 error_free_iph:
303                 kfree(tmp_ext);
304         }
305
306 error:
307         return err;
308 }
309
310 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
311 {
312         /*
313          * Before process AH
314          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
315          * |<-------------->| hdr_len
316          *
317          * To erase AH:
318          * Keeping copy of cleared headers. After AH processing,
319          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
320          * header length. Then copy back the copy as long as hdr_len
321          * If destination header following AH exists, copy it into after [Ext2].
322          *
323          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
324          * There is offset of AH before IPv6 header after the process.
325          */
326
327         struct ipv6_auth_hdr *ah;
328         struct ah_data *ahp;
329         unsigned char *tmp_hdr = NULL;
330         u16 hdr_len;
331         u16 ah_hlen;
332         int nexthdr;
333         int err = -EINVAL;
334
335         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
336                 goto out;
337
338         /* We are going to _remove_ AH header to keep sockets happy,
339          * so... Later this can change. */
340         if (skb_cloned(skb) &&
341             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
342                 goto out;
343
344         hdr_len = skb->data - skb_network_header(skb);
345         ah = (struct ipv6_auth_hdr*)skb->data;
346         ahp = x->data;
347         nexthdr = ah->nexthdr;
348         ah_hlen = (ah->hdrlen + 2) << 2;
349
350         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
351             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
352                 goto out;
353
354         if (!pskb_may_pull(skb, ah_hlen))
355                 goto out;
356
357         tmp_hdr = kmemdup(skb_network_header(skb), hdr_len, GFP_ATOMIC);
358         if (!tmp_hdr)
359                 goto out;
360         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len, XFRM_POLICY_IN))
361                 goto free_out;
362         skb->nh.ipv6h->priority    = 0;
363         skb->nh.ipv6h->flow_lbl[0] = 0;
364         skb->nh.ipv6h->flow_lbl[1] = 0;
365         skb->nh.ipv6h->flow_lbl[2] = 0;
366         skb->nh.ipv6h->hop_limit   = 0;
367
368         {
369                 u8 auth_data[MAX_AH_AUTH_LEN];
370
371                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
372                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
373                 skb_push(skb, hdr_len);
374                 err = ah_mac_digest(ahp, skb, ah->auth_data);
375                 if (err)
376                         goto free_out;
377                 err = -EINVAL;
378                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
379                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
380                         x->stats.integrity_failed++;
381                         goto free_out;
382                 }
383         }
384
385         skb->nh.raw += ah_hlen;
386         memcpy(skb_network_header(skb), tmp_hdr, hdr_len);
387         skb->h.raw = skb->nh.raw;
388         __skb_pull(skb, ah_hlen + hdr_len);
389
390         kfree(tmp_hdr);
391
392         return nexthdr;
393
394 free_out:
395         kfree(tmp_hdr);
396 out:
397         return err;
398 }
399
400 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
401                     int type, int code, int offset, __be32 info)
402 {
403         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
404         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
405         struct xfrm_state *x;
406
407         if (type != ICMPV6_DEST_UNREACH &&
408             type != ICMPV6_PKT_TOOBIG)
409                 return;
410
411         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
412         if (!x)
413                 return;
414
415         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
416                  ntohl(ah->spi), NIP6(iph->daddr));
417
418         xfrm_state_put(x);
419 }
420
421 static int ah6_init_state(struct xfrm_state *x)
422 {
423         struct ah_data *ahp = NULL;
424         struct xfrm_algo_desc *aalg_desc;
425         struct crypto_hash *tfm;
426
427         if (!x->aalg)
428                 goto error;
429
430         /* null auth can use a zero length key */
431         if (x->aalg->alg_key_len > 512)
432                 goto error;
433
434         if (x->encap)
435                 goto error;
436
437         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
438         if (ahp == NULL)
439                 return -ENOMEM;
440
441         ahp->key = x->aalg->alg_key;
442         ahp->key_len = (x->aalg->alg_key_len+7)/8;
443         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
444         if (IS_ERR(tfm))
445                 goto error;
446
447         ahp->tfm = tfm;
448         if (crypto_hash_setkey(tfm, ahp->key, ahp->key_len))
449                 goto error;
450
451         /*
452          * Lookup the algorithm description maintained by xfrm_algo,
453          * verify crypto transform properties, and store information
454          * we need for AH processing.  This lookup cannot fail here
455          * after a successful crypto_alloc_hash().
456          */
457         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
458         BUG_ON(!aalg_desc);
459
460         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
461             crypto_hash_digestsize(tfm)) {
462                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
463                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
464                        aalg_desc->uinfo.auth.icv_fullbits/8);
465                 goto error;
466         }
467
468         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
469         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
470
471         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
472
473         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
474         if (!ahp->work_icv)
475                 goto error;
476
477         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
478         if (x->props.mode == XFRM_MODE_TUNNEL)
479                 x->props.header_len += sizeof(struct ipv6hdr);
480         x->data = ahp;
481
482         return 0;
483
484 error:
485         if (ahp) {
486                 kfree(ahp->work_icv);
487                 crypto_free_hash(ahp->tfm);
488                 kfree(ahp);
489         }
490         return -EINVAL;
491 }
492
493 static void ah6_destroy(struct xfrm_state *x)
494 {
495         struct ah_data *ahp = x->data;
496
497         if (!ahp)
498                 return;
499
500         kfree(ahp->work_icv);
501         ahp->work_icv = NULL;
502         crypto_free_hash(ahp->tfm);
503         ahp->tfm = NULL;
504         kfree(ahp);
505 }
506
507 static struct xfrm_type ah6_type =
508 {
509         .description    = "AH6",
510         .owner          = THIS_MODULE,
511         .proto          = IPPROTO_AH,
512         .init_state     = ah6_init_state,
513         .destructor     = ah6_destroy,
514         .input          = ah6_input,
515         .output         = ah6_output,
516         .hdr_offset     = xfrm6_find_1stfragopt,
517 };
518
519 static struct inet6_protocol ah6_protocol = {
520         .handler        =       xfrm6_rcv,
521         .err_handler    =       ah6_err,
522         .flags          =       INET6_PROTO_NOPOLICY,
523 };
524
525 static int __init ah6_init(void)
526 {
527         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
528                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
529                 return -EAGAIN;
530         }
531
532         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
533                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
534                 xfrm_unregister_type(&ah6_type, AF_INET6);
535                 return -EAGAIN;
536         }
537
538         return 0;
539 }
540
541 static void __exit ah6_fini(void)
542 {
543         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
544                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
545
546         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
547                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
548
549 }
550
551 module_init(ah6_init);
552 module_exit(ah6_fini);
553
554 MODULE_LICENSE("GPL");