esp4.c revision ed0e7e0ca370519d6f79d1093ee2890d4cdee744 
1#include <linux/err.h>
2#include <linux/module.h>
3#include <net/ip.h>
4#include <net/xfrm.h>
5#include <net/esp.h>
6#include <asm/scatterlist.h>
7#include <linux/crypto.h>
8#include <linux/kernel.h>
9#include <linux/pfkeyv2.h>
10#include <linux/random.h>
11#include <linux/spinlock.h>
12#include <net/icmp.h>
13#include <net/protocol.h>
14#include <net/udp.h>
15
16static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
17{
18	int err;
19	struct ip_esp_hdr *esph;
20	struct crypto_blkcipher *tfm;
21	struct blkcipher_desc desc;
22	struct esp_data *esp;
23	struct sk_buff *trailer;
24	u8 *tail;
25	int blksize;
26	int clen;
27	int alen;
28	int nfrags;
29
30	/* skb is pure payload to encrypt */
31
32	err = -ENOMEM;
33
34	/* Round to block size */
35	clen = skb->len;
36
37	esp = x->data;
38	alen = esp->auth.icv_trunc_len;
39	tfm = esp->conf.tfm;
40	desc.tfm = tfm;
41	desc.flags = 0;
42	blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
43	clen = ALIGN(clen + 2, blksize);
44	if (esp->conf.padlen)
45		clen = ALIGN(clen, esp->conf.padlen);
46
47	if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
48		goto error;
49
50	/* Fill padding... */
51	tail = skb_tail_pointer(trailer);
52	do {
53		int i;
54		for (i=0; i<clen-skb->len - 2; i++)
55			tail[i] = i + 1;
56	} while (0);
57	tail[clen - skb->len - 2] = (clen - skb->len) - 2;
58	pskb_put(skb, trailer, clen - skb->len);
59
60	skb_push(skb, -skb_network_offset(skb));
61	esph = ip_esp_hdr(skb);
62	*(skb_tail_pointer(trailer) - 1) = *skb_mac_header(skb);
63	*skb_mac_header(skb) = IPPROTO_ESP;
64
65	spin_lock_bh(&x->lock);
66
67	/* this is non-NULL only with UDP Encapsulation */
68	if (x->encap) {
69		struct xfrm_encap_tmpl *encap = x->encap;
70		struct udphdr *uh;
71		__be32 *udpdata32;
72
73		uh = (struct udphdr *)esph;
74		uh->source = encap->encap_sport;
75		uh->dest = encap->encap_dport;
76		uh->len = htons(skb->len + alen - skb_transport_offset(skb));
77		uh->check = 0;
78
79		switch (encap->encap_type) {
80		default:
81		case UDP_ENCAP_ESPINUDP:
82			esph = (struct ip_esp_hdr *)(uh + 1);
83			break;
84		case UDP_ENCAP_ESPINUDP_NON_IKE:
85			udpdata32 = (__be32 *)(uh + 1);
86			udpdata32[0] = udpdata32[1] = 0;
87			esph = (struct ip_esp_hdr *)(udpdata32 + 2);
88			break;
89		}
90
91		*skb_mac_header(skb) = IPPROTO_UDP;
92	}
93
94	esph->spi = x->id.spi;
95	esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq);
96
97	if (esp->conf.ivlen) {
98		if (unlikely(!esp->conf.ivinitted)) {
99			get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
100			esp->conf.ivinitted = 1;
101		}
102		crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
103	}
104
105	do {
106		struct scatterlist *sg = &esp->sgbuf[0];
107
108		if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
109			sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
110			if (!sg)
111				goto unlock;
112		}
113		sg_init_table(sg, nfrags);
114		skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
115		err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
116		if (unlikely(sg != &esp->sgbuf[0]))
117			kfree(sg);
118	} while (0);
119
120	if (unlikely(err))
121		goto unlock;
122
123	if (esp->conf.ivlen) {
124		memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
125		crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
126	}
127
128	if (esp->auth.icv_full_len) {
129		err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
130				     sizeof(*esph) + esp->conf.ivlen + clen);
131		memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
132	}
133
134unlock:
135	spin_unlock_bh(&x->lock);
136
137error:
138	return err;
139}
140
141/*
142 * Note: detecting truncated vs. non-truncated authentication data is very
143 * expensive, so we only support truncated data, which is the recommended
144 * and common case.
145 */
146static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
147{
148	struct iphdr *iph;
149	struct ip_esp_hdr *esph;
150	struct esp_data *esp = x->data;
151	struct crypto_blkcipher *tfm = esp->conf.tfm;
152	struct blkcipher_desc desc = { .tfm = tfm };
153	struct sk_buff *trailer;
154	int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
155	int alen = esp->auth.icv_trunc_len;
156	int elen = skb->len - sizeof(*esph) - esp->conf.ivlen - alen;
157	int nfrags;
158	int ihl;
159	u8 nexthdr[2];
160	struct scatterlist *sg;
161	int padlen;
162	int err;
163
164	if (!pskb_may_pull(skb, sizeof(*esph)))
165		goto out;
166
167	if (elen <= 0 || (elen & (blksize-1)))
168		goto out;
169
170	/* If integrity check is required, do this. */
171	if (esp->auth.icv_full_len) {
172		u8 sum[alen];
173
174		err = esp_mac_digest(esp, skb, 0, skb->len - alen);
175		if (err)
176			goto out;
177
178		if (skb_copy_bits(skb, skb->len - alen, sum, alen))
179			BUG();
180
181		if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
182			x->stats.integrity_failed++;
183			goto out;
184		}
185	}
186
187	if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
188		goto out;
189
190	skb->ip_summed = CHECKSUM_NONE;
191
192	esph = (struct ip_esp_hdr *)skb->data;
193
194	/* Get ivec. This can be wrong, check against another impls. */
195	if (esp->conf.ivlen)
196		crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
197
198	sg = &esp->sgbuf[0];
199
200	if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
201		sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
202		if (!sg)
203			goto out;
204	}
205	sg_init_table(sg, nfrags);
206	skb_to_sgvec(skb, sg, sizeof(*esph) + esp->conf.ivlen, elen);
207	err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
208	if (unlikely(sg != &esp->sgbuf[0]))
209		kfree(sg);
210	if (unlikely(err))
211		return err;
212
213	if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
214		BUG();
215
216	padlen = nexthdr[0];
217	if (padlen+2 >= elen)
218		goto out;
219
220	/* ... check padding bits here. Silly. :-) */
221
222	iph = ip_hdr(skb);
223	ihl = iph->ihl * 4;
224
225	if (x->encap) {
226		struct xfrm_encap_tmpl *encap = x->encap;
227		struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
228
229		/*
230		 * 1) if the NAT-T peer's IP or port changed then
231		 *    advertize the change to the keying daemon.
232		 *    This is an inbound SA, so just compare
233		 *    SRC ports.
234		 */
235		if (iph->saddr != x->props.saddr.a4 ||
236		    uh->source != encap->encap_sport) {
237			xfrm_address_t ipaddr;
238
239			ipaddr.a4 = iph->saddr;
240			km_new_mapping(x, &ipaddr, uh->source);
241
242			/* XXX: perhaps add an extra
243			 * policy check here, to see
244			 * if we should allow or
245			 * reject a packet from a
246			 * different source
247			 * address/port.
248			 */
249		}
250
251		/*
252		 * 2) ignore UDP/TCP checksums in case
253		 *    of NAT-T in Transport Mode, or
254		 *    perform other post-processing fixes
255		 *    as per draft-ietf-ipsec-udp-encaps-06,
256		 *    section 3.1.2
257		 */
258		if (x->props.mode == XFRM_MODE_TRANSPORT)
259			skb->ip_summed = CHECKSUM_UNNECESSARY;
260	}
261
262	pskb_trim(skb, skb->len - alen - padlen - 2);
263	__skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
264	skb_set_transport_header(skb, -ihl);
265
266	return nexthdr[1];
267
268out:
269	return -EINVAL;
270}
271
272static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
273{
274	struct esp_data *esp = x->data;
275	u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
276	u32 align = max_t(u32, blksize, esp->conf.padlen);
277	u32 rem;
278
279	mtu -= x->props.header_len + esp->auth.icv_trunc_len;
280	rem = mtu & (align - 1);
281	mtu &= ~(align - 1);
282
283	switch (x->props.mode) {
284	case XFRM_MODE_TUNNEL:
285		break;
286	default:
287	case XFRM_MODE_TRANSPORT:
288		/* The worst case */
289		mtu -= blksize - 4;
290		mtu += min_t(u32, blksize - 4, rem);
291		break;
292	case XFRM_MODE_BEET:
293		/* The worst case. */
294		mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
295		break;
296	}
297
298	return mtu - 2;
299}
300
301static void esp4_err(struct sk_buff *skb, u32 info)
302{
303	struct iphdr *iph = (struct iphdr*)skb->data;
304	struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
305	struct xfrm_state *x;
306
307	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
308	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
309		return;
310
311	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
312	if (!x)
313		return;
314	NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
315		 ntohl(esph->spi), ntohl(iph->daddr));
316	xfrm_state_put(x);
317}
318
319static void esp_destroy(struct xfrm_state *x)
320{
321	struct esp_data *esp = x->data;
322
323	if (!esp)
324		return;
325
326	crypto_free_blkcipher(esp->conf.tfm);
327	esp->conf.tfm = NULL;
328	kfree(esp->conf.ivec);
329	esp->conf.ivec = NULL;
330	crypto_free_hash(esp->auth.tfm);
331	esp->auth.tfm = NULL;
332	kfree(esp->auth.work_icv);
333	esp->auth.work_icv = NULL;
334	kfree(esp);
335}
336
337static int esp_init_state(struct xfrm_state *x)
338{
339	struct esp_data *esp = NULL;
340	struct crypto_blkcipher *tfm;
341	u32 align;
342
343	if (x->ealg == NULL)
344		goto error;
345
346	esp = kzalloc(sizeof(*esp), GFP_KERNEL);
347	if (esp == NULL)
348		return -ENOMEM;
349
350	if (x->aalg) {
351		struct xfrm_algo_desc *aalg_desc;
352		struct crypto_hash *hash;
353
354		hash = crypto_alloc_hash(x->aalg->alg_name, 0,
355					 CRYPTO_ALG_ASYNC);
356		if (IS_ERR(hash))
357			goto error;
358
359		esp->auth.tfm = hash;
360		if (crypto_hash_setkey(hash, x->aalg->alg_key,
361				       (x->aalg->alg_key_len + 7) / 8))
362			goto error;
363
364		aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
365		BUG_ON(!aalg_desc);
366
367		if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
368		    crypto_hash_digestsize(hash)) {
369			NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
370				 x->aalg->alg_name,
371				 crypto_hash_digestsize(hash),
372				 aalg_desc->uinfo.auth.icv_fullbits/8);
373			goto error;
374		}
375
376		esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
377		esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
378
379		esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
380		if (!esp->auth.work_icv)
381			goto error;
382	}
383
384	tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
385	if (IS_ERR(tfm))
386		goto error;
387	esp->conf.tfm = tfm;
388	esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
389	esp->conf.padlen = 0;
390	if (esp->conf.ivlen) {
391		esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
392		if (unlikely(esp->conf.ivec == NULL))
393			goto error;
394		esp->conf.ivinitted = 0;
395	}
396	if (crypto_blkcipher_setkey(tfm, x->ealg->alg_key,
397				    (x->ealg->alg_key_len + 7) / 8))
398		goto error;
399	x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
400	if (x->props.mode == XFRM_MODE_TUNNEL)
401		x->props.header_len += sizeof(struct iphdr);
402	else if (x->props.mode == XFRM_MODE_BEET)
403		x->props.header_len += IPV4_BEET_PHMAXLEN;
404	if (x->encap) {
405		struct xfrm_encap_tmpl *encap = x->encap;
406
407		switch (encap->encap_type) {
408		default:
409			goto error;
410		case UDP_ENCAP_ESPINUDP:
411			x->props.header_len += sizeof(struct udphdr);
412			break;
413		case UDP_ENCAP_ESPINUDP_NON_IKE:
414			x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
415			break;
416		}
417	}
418	x->data = esp;
419	align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
420	if (esp->conf.padlen)
421		align = max_t(u32, align, esp->conf.padlen);
422	x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
423	return 0;
424
425error:
426	x->data = esp;
427	esp_destroy(x);
428	x->data = NULL;
429	return -EINVAL;
430}
431
432static struct xfrm_type esp_type =
433{
434	.description	= "ESP4",
435	.owner		= THIS_MODULE,
436	.proto	     	= IPPROTO_ESP,
437	.flags		= XFRM_TYPE_REPLAY_PROT,
438	.init_state	= esp_init_state,
439	.destructor	= esp_destroy,
440	.get_mtu	= esp4_get_mtu,
441	.input		= esp_input,
442	.output		= esp_output
443};
444
445static struct net_protocol esp4_protocol = {
446	.handler	=	xfrm4_rcv,
447	.err_handler	=	esp4_err,
448	.no_policy	=	1,
449};
450
451static int __init esp4_init(void)
452{
453	if (xfrm_register_type(&esp_type, AF_INET) < 0) {
454		printk(KERN_INFO "ip esp init: can't add xfrm type\n");
455		return -EAGAIN;
456	}
457	if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
458		printk(KERN_INFO "ip esp init: can't add protocol\n");
459		xfrm_unregister_type(&esp_type, AF_INET);
460		return -EAGAIN;
461	}
462	return 0;
463}
464
465static void __exit esp4_fini(void)
466{
467	if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
468		printk(KERN_INFO "ip esp close: can't remove protocol\n");
469	if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
470		printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
471}
472
473module_init(esp4_init);
474module_exit(esp4_fini);
475MODULE_LICENSE("GPL");
476MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);
477