5c662703eb1e9cf917df97b41e024c52b946be38
[linux-2.6.git] / net / ipv4 / ah4.c
1 #include <linux/err.h>
2 #include <linux/module.h>
3 #include <net/ip.h>
4 #include <net/xfrm.h>
5 #include <net/ah.h>
6 #include <linux/crypto.h>
7 #include <linux/pfkeyv2.h>
8 #include <linux/spinlock.h>
9 #include <net/icmp.h>
10 #include <net/protocol.h>
11
12
13 /* Clear mutable options and find final destination to substitute
14  * into IP header for icv calculation. Options are already checked
15  * for validity, so paranoia is not required. */
16
17 static int ip_clear_mutable_options(struct iphdr *iph, __be32 *daddr)
18 {
19         unsigned char * optptr = (unsigned char*)(iph+1);
20         int  l = iph->ihl*4 - sizeof(struct iphdr);
21         int  optlen;
22
23         while (l > 0) {
24                 switch (*optptr) {
25                 case IPOPT_END:
26                         return 0;
27                 case IPOPT_NOOP:
28                         l--;
29                         optptr++;
30                         continue;
31                 }
32                 optlen = optptr[1];
33                 if (optlen<2 || optlen>l)
34                         return -EINVAL;
35                 switch (*optptr) {
36                 case IPOPT_SEC:
37                 case 0x85:      /* Some "Extended Security" crap. */
38                 case IPOPT_CIPSO:
39                 case IPOPT_RA:
40                 case 0x80|21:   /* RFC1770 */
41                         break;
42                 case IPOPT_LSRR:
43                 case IPOPT_SSRR:
44                         if (optlen < 6)
45                                 return -EINVAL;
46                         memcpy(daddr, optptr+optlen-4, 4);
47                         /* Fall through */
48                 default:
49                         memset(optptr, 0, optlen);
50                 }
51                 l -= optlen;
52                 optptr += optlen;
53         }
54         return 0;
55 }
56
57 static int ah_output(struct xfrm_state *x, struct sk_buff *skb)
58 {
59         int err;
60         struct iphdr *iph, *top_iph;
61         struct ip_auth_hdr *ah;
62         struct ah_data *ahp;
63         union {
64                 struct iphdr    iph;
65                 char            buf[60];
66         } tmp_iph;
67
68         skb_push(skb, -skb_network_offset(skb));
69         top_iph = ip_hdr(skb);
70         iph = &tmp_iph.iph;
71
72         iph->tos = top_iph->tos;
73         iph->ttl = top_iph->ttl;
74         iph->frag_off = top_iph->frag_off;
75
76         if (top_iph->ihl != 5) {
77                 iph->daddr = top_iph->daddr;
78                 memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
79                 err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
80                 if (err)
81                         goto error;
82         }
83
84         ah = ip_auth_hdr(skb);
85         ah->nexthdr = *skb_mac_header(skb);
86         *skb_mac_header(skb) = IPPROTO_AH;
87
88         top_iph->tos = 0;
89         top_iph->tot_len = htons(skb->len);
90         top_iph->frag_off = 0;
91         top_iph->ttl = 0;
92         top_iph->check = 0;
93
94         ahp = x->data;
95         ah->hdrlen  = (XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len) >> 2) - 2;
96
97         ah->reserved = 0;
98         ah->spi = x->id.spi;
99         ah->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output);
100
101         spin_lock_bh(&x->lock);
102         err = ah_mac_digest(ahp, skb, ah->auth_data);
103         memcpy(ah->auth_data, ahp->work_icv, ahp->icv_trunc_len);
104         spin_unlock_bh(&x->lock);
105
106         if (err)
107                 goto error;
108
109         top_iph->tos = iph->tos;
110         top_iph->ttl = iph->ttl;
111         top_iph->frag_off = iph->frag_off;
112         if (top_iph->ihl != 5) {
113                 top_iph->daddr = iph->daddr;
114                 memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
115         }
116
117         err = 0;
118
119 error:
120         return err;
121 }
122
123 static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
124 {
125         int ah_hlen;
126         int ihl;
127         int nexthdr;
128         int err = -EINVAL;
129         struct iphdr *iph;
130         struct ip_auth_hdr *ah;
131         struct ah_data *ahp;
132         char work_buf[60];
133
134         if (!pskb_may_pull(skb, sizeof(*ah)))
135                 goto out;
136
137         ah = (struct ip_auth_hdr *)skb->data;
138         ahp = x->data;
139         nexthdr = ah->nexthdr;
140         ah_hlen = (ah->hdrlen + 2) << 2;
141
142         if (ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_full_len) &&
143             ah_hlen != XFRM_ALIGN8(sizeof(*ah) + ahp->icv_trunc_len))
144                 goto out;
145
146         if (!pskb_may_pull(skb, ah_hlen))
147                 goto out;
148
149         /* We are going to _remove_ AH header to keep sockets happy,
150          * so... Later this can change. */
151         if (skb_cloned(skb) &&
152             pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
153                 goto out;
154
155         skb->ip_summed = CHECKSUM_NONE;
156
157         ah = (struct ip_auth_hdr *)skb->data;
158         iph = ip_hdr(skb);
159
160         ihl = skb->data - skb_network_header(skb);
161         memcpy(work_buf, iph, ihl);
162
163         iph->ttl = 0;
164         iph->tos = 0;
165         iph->frag_off = 0;
166         iph->check = 0;
167         if (ihl > sizeof(*iph)) {
168                 __be32 dummy;
169                 if (ip_clear_mutable_options(iph, &dummy))
170                         goto out;
171         }
172
173         spin_lock(&x->lock);
174         {
175                 u8 auth_data[MAX_AH_AUTH_LEN];
176
177                 memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
178                 skb_push(skb, ihl);
179                 err = ah_mac_digest(ahp, skb, ah->auth_data);
180                 if (err)
181                         goto unlock;
182                 if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len))
183                         err = -EBADMSG;
184         }
185 unlock:
186         spin_unlock(&x->lock);
187
188         if (err)
189                 goto out;
190
191         skb->network_header += ah_hlen;
192         memcpy(skb_network_header(skb), work_buf, ihl);
193         skb->transport_header = skb->network_header;
194         __skb_pull(skb, ah_hlen + ihl);
195
196         return nexthdr;
197
198 out:
199         return err;
200 }
201
202 static void ah4_err(struct sk_buff *skb, u32 info)
203 {
204         struct net *net = dev_net(skb->dev);
205         struct iphdr *iph = (struct iphdr *)skb->data;
206         struct ip_auth_hdr *ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
207         struct xfrm_state *x;
208
209         if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
210             icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
211                 return;
212
213         x = xfrm_state_lookup(net, (xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
214         if (!x)
215                 return;
216         printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
217                ntohl(ah->spi), ntohl(iph->daddr));
218         xfrm_state_put(x);
219 }
220
221 static int ah_init_state(struct xfrm_state *x)
222 {
223         struct ah_data *ahp = NULL;
224         struct xfrm_algo_desc *aalg_desc;
225         struct crypto_hash *tfm;
226
227         if (!x->aalg)
228                 goto error;
229
230         if (x->encap)
231                 goto error;
232
233         ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
234         if (ahp == NULL)
235                 return -ENOMEM;
236
237         tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
238         if (IS_ERR(tfm))
239                 goto error;
240
241         ahp->tfm = tfm;
242         if (crypto_hash_setkey(tfm, x->aalg->alg_key,
243                                (x->aalg->alg_key_len + 7) / 8))
244                 goto error;
245
246         /*
247          * Lookup the algorithm description maintained by xfrm_algo,
248          * verify crypto transform properties, and store information
249          * we need for AH processing.  This lookup cannot fail here
250          * after a successful crypto_alloc_hash().
251          */
252         aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
253         BUG_ON(!aalg_desc);
254
255         if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
256             crypto_hash_digestsize(tfm)) {
257                 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
258                        x->aalg->alg_name, crypto_hash_digestsize(tfm),
259                        aalg_desc->uinfo.auth.icv_fullbits/8);
260                 goto error;
261         }
262
263         ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
264         ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
265
266         BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
267
268         ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
269         if (!ahp->work_icv)
270                 goto error;
271
272         x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
273                                           ahp->icv_trunc_len);
274         if (x->props.mode == XFRM_MODE_TUNNEL)
275                 x->props.header_len += sizeof(struct iphdr);
276         x->data = ahp;
277
278         return 0;
279
280 error:
281         if (ahp) {
282                 kfree(ahp->work_icv);
283                 crypto_free_hash(ahp->tfm);
284                 kfree(ahp);
285         }
286         return -EINVAL;
287 }
288
289 static void ah_destroy(struct xfrm_state *x)
290 {
291         struct ah_data *ahp = x->data;
292
293         if (!ahp)
294                 return;
295
296         kfree(ahp->work_icv);
297         crypto_free_hash(ahp->tfm);
298         kfree(ahp);
299 }
300
301
302 static const struct xfrm_type ah_type =
303 {
304         .description    = "AH4",
305         .owner          = THIS_MODULE,
306         .proto          = IPPROTO_AH,
307         .flags          = XFRM_TYPE_REPLAY_PROT,
308         .init_state     = ah_init_state,
309         .destructor     = ah_destroy,
310         .input          = ah_input,
311         .output         = ah_output
312 };
313
314 static const struct net_protocol ah4_protocol = {
315         .handler        =       xfrm4_rcv,
316         .err_handler    =       ah4_err,
317         .no_policy      =       1,
318         .netns_ok       =       1,
319 };
320
321 static int __init ah4_init(void)
322 {
323         if (xfrm_register_type(&ah_type, AF_INET) < 0) {
324                 printk(KERN_INFO "ip ah init: can't add xfrm type\n");
325                 return -EAGAIN;
326         }
327         if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
328                 printk(KERN_INFO "ip ah init: can't add protocol\n");
329                 xfrm_unregister_type(&ah_type, AF_INET);
330                 return -EAGAIN;
331         }
332         return 0;
333 }
334
335 static void __exit ah4_fini(void)
336 {
337         if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
338                 printk(KERN_INFO "ip ah close: can't remove protocol\n");
339         if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
340                 printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
341 }
342
343 module_init(ah4_init);
344 module_exit(ah4_fini);
345 MODULE_LICENSE("GPL");
346 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_AH);