[XFRM] STATE: Add a hook to find offset to be inserted header in outbound.
[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 /**
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(
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         xfrm_aevent_doreplay(x);
216         err = ah_mac_digest(ahp, skb, ah->auth_data);
217         if (err)
218                 goto error_free_iph;
219         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
220
221         err = 0;
222
223         memcpy(top_iph, tmp_base, sizeof(tmp_base));
224         if (tmp_ext) {
225                 memcpy(&top_iph->daddr, tmp_ext, extlen);
226 error_free_iph:
227                 kfree(tmp_ext);
228         }
229
230 error:
231         return err;
232 }
233
234 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
235 {
236         /*
237          * Before process AH
238          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
239          * |<-------------->| hdr_len
240          *
241          * To erase AH:
242          * Keeping copy of cleared headers. After AH processing,
243          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
244          * header length. Then copy back the copy as long as hdr_len
245          * If destination header following AH exists, copy it into after [Ext2].
246          * 
247          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
248          * There is offset of AH before IPv6 header after the process.
249          */
250
251         struct ipv6_auth_hdr *ah;
252         struct ah_data *ahp;
253         unsigned char *tmp_hdr = NULL;
254         u16 hdr_len;
255         u16 ah_hlen;
256         int nexthdr;
257         int err = -EINVAL;
258
259         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
260                 goto out;
261
262         /* We are going to _remove_ AH header to keep sockets happy,
263          * so... Later this can change. */
264         if (skb_cloned(skb) &&
265             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
266                 goto out;
267
268         hdr_len = skb->data - skb->nh.raw;
269         ah = (struct ipv6_auth_hdr*)skb->data;
270         ahp = x->data;
271         nexthdr = ah->nexthdr;
272         ah_hlen = (ah->hdrlen + 2) << 2;
273
274         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
275             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
276                 goto out;
277
278         if (!pskb_may_pull(skb, ah_hlen))
279                 goto out;
280
281         tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
282         if (!tmp_hdr)
283                 goto out;
284         memcpy(tmp_hdr, skb->nh.raw, hdr_len);
285         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
286                 goto free_out;
287         skb->nh.ipv6h->priority    = 0;
288         skb->nh.ipv6h->flow_lbl[0] = 0;
289         skb->nh.ipv6h->flow_lbl[1] = 0;
290         skb->nh.ipv6h->flow_lbl[2] = 0;
291         skb->nh.ipv6h->hop_limit   = 0;
292
293         {
294                 u8 auth_data[MAX_AH_AUTH_LEN];
295
296                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
297                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
298                 skb_push(skb, hdr_len);
299                 err = ah_mac_digest(ahp, skb, ah->auth_data);
300                 if (err)
301                         goto free_out;
302                 err = -EINVAL;
303                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
304                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
305                         x->stats.integrity_failed++;
306                         goto free_out;
307                 }
308         }
309
310         skb->h.raw = memcpy(skb->nh.raw += ah_hlen, tmp_hdr, hdr_len);
311         __skb_pull(skb, ah_hlen + hdr_len);
312
313         kfree(tmp_hdr);
314
315         return nexthdr;
316
317 free_out:
318         kfree(tmp_hdr);
319 out:
320         return err;
321 }
322
323 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, 
324                     int type, int code, int offset, __u32 info)
325 {
326         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
327         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
328         struct xfrm_state *x;
329
330         if (type != ICMPV6_DEST_UNREACH &&
331             type != ICMPV6_PKT_TOOBIG)
332                 return;
333
334         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
335         if (!x)
336                 return;
337
338         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
339                  ntohl(ah->spi), NIP6(iph->daddr));
340
341         xfrm_state_put(x);
342 }
343
344 static int ah6_init_state(struct xfrm_state *x)
345 {
346         struct ah_data *ahp = NULL;
347         struct xfrm_algo_desc *aalg_desc;
348         struct crypto_hash *tfm;
349
350         if (!x->aalg)
351                 goto error;
352
353         /* null auth can use a zero length key */
354         if (x->aalg->alg_key_len > 512)
355                 goto error;
356
357         if (x->encap)
358                 goto error;
359
360         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
361         if (ahp == NULL)
362                 return -ENOMEM;
363
364         ahp->key = x->aalg->alg_key;
365         ahp->key_len = (x->aalg->alg_key_len+7)/8;
366         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
367         if (IS_ERR(tfm))
368                 goto error;
369
370         ahp->tfm = tfm;
371         if (crypto_hash_setkey(tfm, ahp->key, ahp->key_len))
372                 goto error;
373         
374         /*
375          * Lookup the algorithm description maintained by xfrm_algo,
376          * verify crypto transform properties, and store information
377          * we need for AH processing.  This lookup cannot fail here
378          * after a successful crypto_alloc_hash().
379          */
380         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
381         BUG_ON(!aalg_desc);
382
383         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
384             crypto_hash_digestsize(tfm)) {
385                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
386                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
387                        aalg_desc->uinfo.auth.icv_fullbits/8);
388                 goto error;
389         }
390         
391         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
392         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
393         
394         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
395         
396         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
397         if (!ahp->work_icv)
398                 goto error;
399         
400         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
401         if (x->props.mode == XFRM_MODE_TUNNEL)
402                 x->props.header_len += sizeof(struct ipv6hdr);
403         x->data = ahp;
404
405         return 0;
406
407 error:
408         if (ahp) {
409                 kfree(ahp->work_icv);
410                 crypto_free_hash(ahp->tfm);
411                 kfree(ahp);
412         }
413         return -EINVAL;
414 }
415
416 static void ah6_destroy(struct xfrm_state *x)
417 {
418         struct ah_data *ahp = x->data;
419
420         if (!ahp)
421                 return;
422
423         kfree(ahp->work_icv);
424         ahp->work_icv = NULL;
425         crypto_free_hash(ahp->tfm);
426         ahp->tfm = NULL;
427         kfree(ahp);
428 }
429
430 static struct xfrm_type ah6_type =
431 {
432         .description    = "AH6",
433         .owner          = THIS_MODULE,
434         .proto          = IPPROTO_AH,
435         .init_state     = ah6_init_state,
436         .destructor     = ah6_destroy,
437         .input          = ah6_input,
438         .output         = ah6_output,
439         .hdr_offset     = xfrm6_find_1stfragopt,
440 };
441
442 static struct inet6_protocol ah6_protocol = {
443         .handler        =       xfrm6_rcv,
444         .err_handler    =       ah6_err,
445         .flags          =       INET6_PROTO_NOPOLICY,
446 };
447
448 static int __init ah6_init(void)
449 {
450         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
451                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
452                 return -EAGAIN;
453         }
454
455         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
456                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
457                 xfrm_unregister_type(&ah6_type, AF_INET6);
458                 return -EAGAIN;
459         }
460
461         return 0;
462 }
463
464 static void __exit ah6_fini(void)
465 {
466         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
467                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
468
469         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
470                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
471
472 }
473
474 module_init(ah6_init);
475 module_exit(ah6_fini);
476
477 MODULE_LICENSE("GPL");