d31c0d6c04488c90cf7c8972851c9f526aa1f1f0
[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/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/protocol.h>
37 #include <net/xfrm.h>
38 #include <asm/scatterlist.h>
39
40 static int zero_out_mutable_opts(struct ipv6_opt_hdr *opthdr)
41 {
42         u8 *opt = (u8 *)opthdr;
43         int len = ipv6_optlen(opthdr);
44         int off = 0;
45         int optlen = 0;
46
47         off += 2;
48         len -= 2;
49
50         while (len > 0) {
51
52                 switch (opt[off]) {
53
54                 case IPV6_TLV_PAD0:
55                         optlen = 1;
56                         break;
57                 default:
58                         if (len < 2) 
59                                 goto bad;
60                         optlen = opt[off+1]+2;
61                         if (len < optlen)
62                                 goto bad;
63                         if (opt[off] & 0x20)
64                                 memset(&opt[off+2], 0, opt[off+1]);
65                         break;
66                 }
67
68                 off += optlen;
69                 len -= optlen;
70         }
71         if (len == 0)
72                 return 1;
73
74 bad:
75         return 0;
76 }
77
78 /**
79  *      ipv6_rearrange_rthdr - rearrange IPv6 routing header
80  *      @iph: IPv6 header
81  *      @rthdr: routing header
82  *
83  *      Rearrange the destination address in @iph and the addresses in @rthdr
84  *      so that they appear in the order they will at the final destination.
85  *      See Appendix A2 of RFC 2402 for details.
86  */
87 static void ipv6_rearrange_rthdr(struct ipv6hdr *iph, struct ipv6_rt_hdr *rthdr)
88 {
89         int segments, segments_left;
90         struct in6_addr *addrs;
91         struct in6_addr final_addr;
92
93         segments_left = rthdr->segments_left;
94         if (segments_left == 0)
95                 return;
96         rthdr->segments_left = 0; 
97
98         /* The value of rthdr->hdrlen has been verified either by the system
99          * call if it is locally generated, or by ipv6_rthdr_rcv() for incoming
100          * packets.  So we can assume that it is even and that segments is
101          * greater than or equal to segments_left.
102          *
103          * For the same reason we can assume that this option is of type 0.
104          */
105         segments = rthdr->hdrlen >> 1;
106
107         addrs = ((struct rt0_hdr *)rthdr)->addr;
108         ipv6_addr_copy(&final_addr, addrs + segments - 1);
109
110         addrs += segments - segments_left;
111         memmove(addrs + 1, addrs, (segments_left - 1) * sizeof(*addrs));
112
113         ipv6_addr_copy(addrs, &iph->daddr);
114         ipv6_addr_copy(&iph->daddr, &final_addr);
115 }
116
117 static int ipv6_clear_mutable_options(struct ipv6hdr *iph, int len)
118 {
119         union {
120                 struct ipv6hdr *iph;
121                 struct ipv6_opt_hdr *opth;
122                 struct ipv6_rt_hdr *rth;
123                 char *raw;
124         } exthdr = { .iph = iph };
125         char *end = exthdr.raw + len;
126         int nexthdr = iph->nexthdr;
127
128         exthdr.iph++;
129
130         while (exthdr.raw < end) {
131                 switch (nexthdr) {
132                 case NEXTHDR_HOP:
133                 case NEXTHDR_DEST:
134                         if (!zero_out_mutable_opts(exthdr.opth)) {
135                                 LIMIT_NETDEBUG(
136                                         KERN_WARNING "overrun %sopts\n",
137                                         nexthdr == NEXTHDR_HOP ?
138                                                 "hop" : "dest");
139                                 return -EINVAL;
140                         }
141                         break;
142
143                 case NEXTHDR_ROUTING:
144                         ipv6_rearrange_rthdr(iph, exthdr.rth);
145                         break;
146
147                 default :
148                         return 0;
149                 }
150
151                 nexthdr = exthdr.opth->nexthdr;
152                 exthdr.raw += ipv6_optlen(exthdr.opth);
153         }
154
155         return 0;
156 }
157
158 static int ah6_output(struct xfrm_state *x, struct sk_buff *skb)
159 {
160         int err;
161         int extlen;
162         struct ipv6hdr *top_iph;
163         struct ip_auth_hdr *ah;
164         struct ah_data *ahp;
165         u8 nexthdr;
166         char tmp_base[8];
167         struct {
168                 struct in6_addr daddr;
169                 char hdrs[0];
170         } *tmp_ext;
171
172         top_iph = (struct ipv6hdr *)skb->data;
173         top_iph->payload_len = htons(skb->len - sizeof(*top_iph));
174
175         nexthdr = *skb->nh.raw;
176         *skb->nh.raw = IPPROTO_AH;
177
178         /* When there are no extension headers, we only need to save the first
179          * 8 bytes of the base IP header.
180          */
181         memcpy(tmp_base, top_iph, sizeof(tmp_base));
182
183         tmp_ext = NULL;
184         extlen = skb->h.raw - (unsigned char *)(top_iph + 1);
185         if (extlen) {
186                 extlen += sizeof(*tmp_ext);
187                 tmp_ext = kmalloc(extlen, GFP_ATOMIC);
188                 if (!tmp_ext) {
189                         err = -ENOMEM;
190                         goto error;
191                 }
192                 memcpy(tmp_ext, &top_iph->daddr, extlen);
193                 err = ipv6_clear_mutable_options(top_iph,
194                                                  extlen - sizeof(*tmp_ext) +
195                                                  sizeof(*top_iph));
196                 if (err)
197                         goto error_free_iph;
198         }
199
200         ah = (struct ip_auth_hdr *)skb->h.raw;
201         ah->nexthdr = nexthdr;
202
203         top_iph->priority    = 0;
204         top_iph->flow_lbl[0] = 0;
205         top_iph->flow_lbl[1] = 0;
206         top_iph->flow_lbl[2] = 0;
207         top_iph->hop_limit   = 0;
208
209         ahp = x->data;
210         ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + 
211                                    ahp->icv_trunc_len) >> 2) - 2;
212
213         ah->reserved = 0;
214         ah->spi = x->id.spi;
215         ah->seq_no = htonl(++x->replay.oseq);
216         xfrm_aevent_doreplay(x);
217         ahp->icv(ahp, skb, ah->auth_data);
218
219         err = 0;
220
221         memcpy(top_iph, tmp_base, sizeof(tmp_base));
222         if (tmp_ext) {
223                 memcpy(&top_iph->daddr, tmp_ext, extlen);
224 error_free_iph:
225                 kfree(tmp_ext);
226         }
227
228 error:
229         return err;
230 }
231
232 static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
233 {
234         /*
235          * Before process AH
236          * [IPv6][Ext1][Ext2][AH][Dest][Payload]
237          * |<-------------->| hdr_len
238          *
239          * To erase AH:
240          * Keeping copy of cleared headers. After AH processing,
241          * Moving the pointer of skb->nh.raw by using skb_pull as long as AH
242          * header length. Then copy back the copy as long as hdr_len
243          * If destination header following AH exists, copy it into after [Ext2].
244          * 
245          * |<>|[IPv6][Ext1][Ext2][Dest][Payload]
246          * There is offset of AH before IPv6 header after the process.
247          */
248
249         struct ipv6_auth_hdr *ah;
250         struct ah_data *ahp;
251         unsigned char *tmp_hdr = NULL;
252         u16 hdr_len;
253         u16 ah_hlen;
254         int nexthdr;
255
256         if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
257                 goto out;
258
259         /* We are going to _remove_ AH header to keep sockets happy,
260          * so... Later this can change. */
261         if (skb_cloned(skb) &&
262             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
263                 goto out;
264
265         hdr_len = skb->data - skb->nh.raw;
266         ah = (struct ipv6_auth_hdr*)skb->data;
267         ahp = x->data;
268         nexthdr = ah->nexthdr;
269         ah_hlen = (ah->hdrlen + 2) << 2;
270
271         if (ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_full_len) &&
272             ah_hlen != XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len))
273                 goto out;
274
275         if (!pskb_may_pull(skb, ah_hlen))
276                 goto out;
277
278         tmp_hdr = kmalloc(hdr_len, GFP_ATOMIC);
279         if (!tmp_hdr)
280                 goto out;
281         memcpy(tmp_hdr, skb->nh.raw, hdr_len);
282         if (ipv6_clear_mutable_options(skb->nh.ipv6h, hdr_len))
283                 goto free_out;
284         skb->nh.ipv6h->priority    = 0;
285         skb->nh.ipv6h->flow_lbl[0] = 0;
286         skb->nh.ipv6h->flow_lbl[1] = 0;
287         skb->nh.ipv6h->flow_lbl[2] = 0;
288         skb->nh.ipv6h->hop_limit   = 0;
289
290         {
291                 u8 auth_data[MAX_AH_AUTH_LEN];
292
293                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
294                 memset(ah->auth_data, 0, ahp->icv_trunc_len);
295                 skb_push(skb, hdr_len);
296                 ahp->icv(ahp, skb, ah->auth_data);
297                 if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
298                         LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
299                         x->stats.integrity_failed++;
300                         goto free_out;
301                 }
302         }
303
304         skb->h.raw = memcpy(skb->nh.raw += ah_hlen, tmp_hdr, hdr_len);
305         __skb_pull(skb, ah_hlen + hdr_len);
306
307         kfree(tmp_hdr);
308
309         return nexthdr;
310
311 free_out:
312         kfree(tmp_hdr);
313 out:
314         return -EINVAL;
315 }
316
317 static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, 
318                     int type, int code, int offset, __u32 info)
319 {
320         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
321         struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
322         struct xfrm_state *x;
323
324         if (type != ICMPV6_DEST_UNREACH &&
325             type != ICMPV6_PKT_TOOBIG)
326                 return;
327
328         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET6);
329         if (!x)
330                 return;
331
332         NETDEBUG(KERN_DEBUG "pmtu discovery on SA AH/%08x/" NIP6_FMT "\n",
333                  ntohl(ah->spi), NIP6(iph->daddr));
334
335         xfrm_state_put(x);
336 }
337
338 static int ah6_init_state(struct xfrm_state *x)
339 {
340         struct ah_data *ahp = NULL;
341         struct xfrm_algo_desc *aalg_desc;
342
343         if (!x->aalg)
344                 goto error;
345
346         /* null auth can use a zero length key */
347         if (x->aalg->alg_key_len > 512)
348                 goto error;
349
350         if (x->encap)
351                 goto error;
352
353         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
354         if (ahp == NULL)
355                 return -ENOMEM;
356
357         ahp->key = x->aalg->alg_key;
358         ahp->key_len = (x->aalg->alg_key_len+7)/8;
359         ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
360         if (!ahp->tfm)
361                 goto error;
362         ahp->icv = ah_hmac_digest;
363         
364         /*
365          * Lookup the algorithm description maintained by xfrm_algo,
366          * verify crypto transform properties, and store information
367          * we need for AH processing.  This lookup cannot fail here
368          * after a successful crypto_alloc_tfm().
369          */
370         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
371         BUG_ON(!aalg_desc);
372
373         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
374             crypto_tfm_alg_digestsize(ahp->tfm)) {
375                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
376                        x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
377                        aalg_desc->uinfo.auth.icv_fullbits/8);
378                 goto error;
379         }
380         
381         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
382         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
383         
384         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
385         
386         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
387         if (!ahp->work_icv)
388                 goto error;
389         
390         x->props.header_len = XFRM_ALIGN8(sizeof(struct ipv6_auth_hdr) + ahp->icv_trunc_len);
391         if (x->props.mode)
392                 x->props.header_len += sizeof(struct ipv6hdr);
393         x->data = ahp;
394
395         return 0;
396
397 error:
398         if (ahp) {
399                 kfree(ahp->work_icv);
400                 crypto_free_tfm(ahp->tfm);
401                 kfree(ahp);
402         }
403         return -EINVAL;
404 }
405
406 static void ah6_destroy(struct xfrm_state *x)
407 {
408         struct ah_data *ahp = x->data;
409
410         if (!ahp)
411                 return;
412
413         kfree(ahp->work_icv);
414         ahp->work_icv = NULL;
415         crypto_free_tfm(ahp->tfm);
416         ahp->tfm = NULL;
417         kfree(ahp);
418 }
419
420 static struct xfrm_type ah6_type =
421 {
422         .description    = "AH6",
423         .owner          = THIS_MODULE,
424         .proto          = IPPROTO_AH,
425         .init_state     = ah6_init_state,
426         .destructor     = ah6_destroy,
427         .input          = ah6_input,
428         .output         = ah6_output
429 };
430
431 static struct inet6_protocol ah6_protocol = {
432         .handler        =       xfrm6_rcv,
433         .err_handler    =       ah6_err,
434         .flags          =       INET6_PROTO_NOPOLICY,
435 };
436
437 static int __init ah6_init(void)
438 {
439         if (xfrm_register_type(&ah6_type, AF_INET6) < 0) {
440                 printk(KERN_INFO "ipv6 ah init: can't add xfrm type\n");
441                 return -EAGAIN;
442         }
443
444         if (inet6_add_protocol(&ah6_protocol, IPPROTO_AH) < 0) {
445                 printk(KERN_INFO "ipv6 ah init: can't add protocol\n");
446                 xfrm_unregister_type(&ah6_type, AF_INET6);
447                 return -EAGAIN;
448         }
449
450         return 0;
451 }
452
453 static void __exit ah6_fini(void)
454 {
455         if (inet6_del_protocol(&ah6_protocol, IPPROTO_AH) < 0)
456                 printk(KERN_INFO "ipv6 ah close: can't remove protocol\n");
457
458         if (xfrm_unregister_type(&ah6_type, AF_INET6) < 0)
459                 printk(KERN_INFO "ipv6 ah close: can't remove xfrm type\n");
460
461 }
462
463 module_init(ah6_init);
464 module_exit(ah6_fini);
465
466 MODULE_LICENSE("GPL");