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 iphdr *iph = (struct iphdr*)skb->data;
205 struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
206 struct xfrm_state *x;
207
208 if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
209 icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
210 return;
211
212 x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
213 if (!x)
214 return;
215 printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
216 ntohl(ah->spi), ntohl(iph->daddr));
217 xfrm_state_put(x);
218 }
219
220 static int ah_init_state(struct xfrm_state *x)
221 {
222 struct ah_data *ahp = NULL;
223 struct xfrm_algo_desc *aalg_desc;
224 struct crypto_hash *tfm;
225
226 if (!x->aalg)
227 goto error;
228
229 if (x->encap)
230 goto error;
231
232 ahp = kzalloc(sizeof(*ahp), GFP_KERNEL);
233 if (ahp == NULL)
234 return -ENOMEM;
235
236 tfm = crypto_alloc_hash(x->aalg->alg_name, 0, CRYPTO_ALG_ASYNC);
237 if (IS_ERR(tfm))
238 goto error;
239
240 ahp->tfm = tfm;
241 if (crypto_hash_setkey(tfm, x->aalg->alg_key,
242 (x->aalg->alg_key_len + 7) / 8))
243 goto error;
244
245 /*
246 * Lookup the algorithm description maintained by xfrm_algo,
247 * verify crypto transform properties, and store information
248 * we need for AH processing. This lookup cannot fail here
249 * after a successful crypto_alloc_hash().
250 */
251 aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
252 BUG_ON(!aalg_desc);
253
254 if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
255 crypto_hash_digestsize(tfm)) {
256 printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
257 x->aalg->alg_name, crypto_hash_digestsize(tfm),
258 aalg_desc->uinfo.auth.icv_fullbits/8);
259 goto error;
260 }
261
262 ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
263 ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
264
265 BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
266
267 ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
268 if (!ahp->work_icv)
269 goto error;
270
271 x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
272 ahp->icv_trunc_len);
273 if (x->props.mode == XFRM_MODE_TUNNEL)
274 x->props.header_len += sizeof(struct iphdr);
275 x->data = ahp;
276
277 return 0;
278
279 error:
280 if (ahp) {
281 kfree(ahp->work_icv);
282 crypto_free_hash(ahp->tfm);
283 kfree(ahp);
284 }
285 return -EINVAL;
286 }
287
288 static void ah_destroy(struct xfrm_state *x)
289 {
290 struct ah_data *ahp = x->data;
291
292 if (!ahp)
293 return;
294
295 kfree(ahp->work_icv);
296 ahp->work_icv = NULL;
297 crypto_free_hash(ahp->tfm);
298 ahp->tfm = NULL;
299 kfree(ahp);
300 }
301
302
303 static const struct xfrm_type ah_type =
304 {
305 .description = "AH4",
306 .owner = THIS_MODULE,
307 .proto = IPPROTO_AH,
308 .flags = XFRM_TYPE_REPLAY_PROT,
309 .init_state = ah_init_state,
310 .destructor = ah_destroy,
311 .input = ah_input,
312 .output = ah_output
313 };
314
315 static struct net_protocol ah4_protocol = {
316 .handler = xfrm4_rcv,
317 .err_handler = ah4_err,
318 .no_policy = 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);
347
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