ah4.c revision 14c850212ed8f8cbb5972ad6b8812e08a0bc901c 
1#include <linux/config.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 <net/icmp.h>
9#include <net/protocol.h>
10#include <asm/scatterlist.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
17static int ip_clear_mutable_options(struct iphdr *iph, u32 *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 0x86:	/* Another "Commercial Security" crap. */
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+2, 0, optlen-2);
50		}
51		l -= optlen;
52		optptr += optlen;
53	}
54	return 0;
55}
56
57static 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	top_iph = skb->nh.iph;
69	iph = &tmp_iph.iph;
70
71	iph->tos = top_iph->tos;
72	iph->ttl = top_iph->ttl;
73	iph->frag_off = top_iph->frag_off;
74
75	if (top_iph->ihl != 5) {
76		iph->daddr = top_iph->daddr;
77		memcpy(iph+1, top_iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
78		err = ip_clear_mutable_options(top_iph, &top_iph->daddr);
79		if (err)
80			goto error;
81	}
82
83	ah = (struct ip_auth_hdr *)((char *)top_iph+top_iph->ihl*4);
84	ah->nexthdr = top_iph->protocol;
85
86	top_iph->tos = 0;
87	top_iph->tot_len = htons(skb->len);
88	top_iph->frag_off = 0;
89	top_iph->ttl = 0;
90	top_iph->protocol = IPPROTO_AH;
91	top_iph->check = 0;
92
93	ahp = x->data;
94	ah->hdrlen  = (XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
95				   ahp->icv_trunc_len) >> 2) - 2;
96
97	ah->reserved = 0;
98	ah->spi = x->id.spi;
99	ah->seq_no = htonl(++x->replay.oseq);
100	ahp->icv(ahp, skb, ah->auth_data);
101
102	top_iph->tos = iph->tos;
103	top_iph->ttl = iph->ttl;
104	top_iph->frag_off = iph->frag_off;
105	if (top_iph->ihl != 5) {
106		top_iph->daddr = iph->daddr;
107		memcpy(top_iph+1, iph+1, top_iph->ihl*4 - sizeof(struct iphdr));
108	}
109
110	ip_send_check(top_iph);
111
112	err = 0;
113
114error:
115	return err;
116}
117
118static int ah_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_buff *skb)
119{
120	int ah_hlen;
121	struct iphdr *iph;
122	struct ip_auth_hdr *ah;
123	struct ah_data *ahp;
124	char work_buf[60];
125
126	if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
127		goto out;
128
129	ah = (struct ip_auth_hdr*)skb->data;
130	ahp = x->data;
131	ah_hlen = (ah->hdrlen + 2) << 2;
132
133	if (ah_hlen != XFRM_ALIGN8(sizeof(struct ip_auth_hdr) + ahp->icv_full_len) &&
134	    ah_hlen != XFRM_ALIGN8(sizeof(struct ip_auth_hdr) + ahp->icv_trunc_len))
135		goto out;
136
137	if (!pskb_may_pull(skb, ah_hlen))
138		goto out;
139
140	/* We are going to _remove_ AH header to keep sockets happy,
141	 * so... Later this can change. */
142	if (skb_cloned(skb) &&
143	    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
144		goto out;
145
146	skb->ip_summed = CHECKSUM_NONE;
147
148	ah = (struct ip_auth_hdr*)skb->data;
149	iph = skb->nh.iph;
150
151	memcpy(work_buf, iph, iph->ihl*4);
152
153	iph->ttl = 0;
154	iph->tos = 0;
155	iph->frag_off = 0;
156	iph->check = 0;
157	if (iph->ihl != 5) {
158		u32 dummy;
159		if (ip_clear_mutable_options(iph, &dummy))
160			goto out;
161	}
162        {
163		u8 auth_data[MAX_AH_AUTH_LEN];
164
165		memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
166		skb_push(skb, skb->data - skb->nh.raw);
167		ahp->icv(ahp, skb, ah->auth_data);
168		if (memcmp(ah->auth_data, auth_data, ahp->icv_trunc_len)) {
169			x->stats.integrity_failed++;
170			goto out;
171		}
172	}
173	((struct iphdr*)work_buf)->protocol = ah->nexthdr;
174	skb->nh.raw = skb_pull(skb, ah_hlen);
175	memcpy(skb->nh.raw, work_buf, iph->ihl*4);
176	skb->nh.iph->tot_len = htons(skb->len);
177	skb_pull(skb, skb->nh.iph->ihl*4);
178	skb->h.raw = skb->data;
179
180	return 0;
181
182out:
183	return -EINVAL;
184}
185
186static void ah4_err(struct sk_buff *skb, u32 info)
187{
188	struct iphdr *iph = (struct iphdr*)skb->data;
189	struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+(iph->ihl<<2));
190	struct xfrm_state *x;
191
192	if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
193	    skb->h.icmph->code != ICMP_FRAG_NEEDED)
194		return;
195
196	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, ah->spi, IPPROTO_AH, AF_INET);
197	if (!x)
198		return;
199	printk(KERN_DEBUG "pmtu discovery on SA AH/%08x/%08x\n",
200	       ntohl(ah->spi), ntohl(iph->daddr));
201	xfrm_state_put(x);
202}
203
204static int ah_init_state(struct xfrm_state *x)
205{
206	struct ah_data *ahp = NULL;
207	struct xfrm_algo_desc *aalg_desc;
208
209	if (!x->aalg)
210		goto error;
211
212	/* null auth can use a zero length key */
213	if (x->aalg->alg_key_len > 512)
214		goto error;
215
216	if (x->encap)
217		goto error;
218
219	ahp = kmalloc(sizeof(*ahp), GFP_KERNEL);
220	if (ahp == NULL)
221		return -ENOMEM;
222
223	memset(ahp, 0, sizeof(*ahp));
224
225	ahp->key = x->aalg->alg_key;
226	ahp->key_len = (x->aalg->alg_key_len+7)/8;
227	ahp->tfm = crypto_alloc_tfm(x->aalg->alg_name, 0);
228	if (!ahp->tfm)
229		goto error;
230	ahp->icv = ah_hmac_digest;
231
232	/*
233	 * Lookup the algorithm description maintained by xfrm_algo,
234	 * verify crypto transform properties, and store information
235	 * we need for AH processing.  This lookup cannot fail here
236	 * after a successful crypto_alloc_tfm().
237	 */
238	aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
239	BUG_ON(!aalg_desc);
240
241	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
242	    crypto_tfm_alg_digestsize(ahp->tfm)) {
243		printk(KERN_INFO "AH: %s digestsize %u != %hu\n",
244		       x->aalg->alg_name, crypto_tfm_alg_digestsize(ahp->tfm),
245		       aalg_desc->uinfo.auth.icv_fullbits/8);
246		goto error;
247	}
248
249	ahp->icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
250	ahp->icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
251
252	BUG_ON(ahp->icv_trunc_len > MAX_AH_AUTH_LEN);
253
254	ahp->work_icv = kmalloc(ahp->icv_full_len, GFP_KERNEL);
255	if (!ahp->work_icv)
256		goto error;
257
258	x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) + ahp->icv_trunc_len);
259	if (x->props.mode)
260		x->props.header_len += sizeof(struct iphdr);
261	x->data = ahp;
262
263	return 0;
264
265error:
266	if (ahp) {
267		kfree(ahp->work_icv);
268		crypto_free_tfm(ahp->tfm);
269		kfree(ahp);
270	}
271	return -EINVAL;
272}
273
274static void ah_destroy(struct xfrm_state *x)
275{
276	struct ah_data *ahp = x->data;
277
278	if (!ahp)
279		return;
280
281	kfree(ahp->work_icv);
282	ahp->work_icv = NULL;
283	crypto_free_tfm(ahp->tfm);
284	ahp->tfm = NULL;
285	kfree(ahp);
286}
287
288
289static struct xfrm_type ah_type =
290{
291	.description	= "AH4",
292	.owner		= THIS_MODULE,
293	.proto	     	= IPPROTO_AH,
294	.init_state	= ah_init_state,
295	.destructor	= ah_destroy,
296	.input		= ah_input,
297	.output		= ah_output
298};
299
300static struct net_protocol ah4_protocol = {
301	.handler	=	xfrm4_rcv,
302	.err_handler	=	ah4_err,
303	.no_policy	=	1,
304};
305
306static int __init ah4_init(void)
307{
308	if (xfrm_register_type(&ah_type, AF_INET) < 0) {
309		printk(KERN_INFO "ip ah init: can't add xfrm type\n");
310		return -EAGAIN;
311	}
312	if (inet_add_protocol(&ah4_protocol, IPPROTO_AH) < 0) {
313		printk(KERN_INFO "ip ah init: can't add protocol\n");
314		xfrm_unregister_type(&ah_type, AF_INET);
315		return -EAGAIN;
316	}
317	return 0;
318}
319
320static void __exit ah4_fini(void)
321{
322	if (inet_del_protocol(&ah4_protocol, IPPROTO_AH) < 0)
323		printk(KERN_INFO "ip ah close: can't remove protocol\n");
324	if (xfrm_unregister_type(&ah_type, AF_INET) < 0)
325		printk(KERN_INFO "ip ah close: can't remove xfrm type\n");
326}
327
328module_init(ah4_init);
329module_exit(ah4_fini);
330MODULE_LICENSE("GPL");
331