esp4.c revision ac758e3c55c529714354fc268892ca4d23ca1e99 
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 <net/icmp.h>
12#include <net/protocol.h>
13#include <net/udp.h>
14
15static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
16{
17	int err;
18	struct iphdr *top_iph;
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	/* Strip IP+ESP header. */
31	__skb_pull(skb, skb_transport_offset(skb));
32	/* Now skb is pure payload to encrypt */
33
34	err = -ENOMEM;
35
36	/* Round to block size */
37	clen = skb->len;
38
39	esp = x->data;
40	alen = esp->auth.icv_trunc_len;
41	tfm = esp->conf.tfm;
42	desc.tfm = tfm;
43	desc.flags = 0;
44	blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
45	clen = ALIGN(clen + 2, blksize);
46	if (esp->conf.padlen)
47		clen = ALIGN(clen, esp->conf.padlen);
48
49	if ((nfrags = skb_cow_data(skb, clen-skb->len+alen, &trailer)) < 0)
50		goto error;
51
52	/* Fill padding... */
53	tail = skb_tail_pointer(trailer);
54	do {
55		int i;
56		for (i=0; i<clen-skb->len - 2; i++)
57			tail[i] = i + 1;
58	} while (0);
59	tail[clen - skb->len - 2] = (clen - skb->len) - 2;
60	pskb_put(skb, trailer, clen - skb->len);
61
62	__skb_push(skb, skb->data - skb_network_header(skb));
63	top_iph = ip_hdr(skb);
64	esph = (struct ip_esp_hdr *)(skb_network_header(skb) +
65				     top_iph->ihl * 4);
66	top_iph->tot_len = htons(skb->len + alen);
67	*(skb_tail_pointer(trailer) - 1) = top_iph->protocol;
68
69	/* this is non-NULL only with UDP Encapsulation */
70	if (x->encap) {
71		struct xfrm_encap_tmpl *encap = x->encap;
72		struct udphdr *uh;
73		__be32 *udpdata32;
74
75		uh = (struct udphdr *)esph;
76		uh->source = encap->encap_sport;
77		uh->dest = encap->encap_dport;
78		uh->len = htons(skb->len + alen - top_iph->ihl*4);
79		uh->check = 0;
80
81		switch (encap->encap_type) {
82		default:
83		case UDP_ENCAP_ESPINUDP:
84			esph = (struct ip_esp_hdr *)(uh + 1);
85			break;
86		case UDP_ENCAP_ESPINUDP_NON_IKE:
87			udpdata32 = (__be32 *)(uh + 1);
88			udpdata32[0] = udpdata32[1] = 0;
89			esph = (struct ip_esp_hdr *)(udpdata32 + 2);
90			break;
91		}
92
93		top_iph->protocol = IPPROTO_UDP;
94	} else
95		top_iph->protocol = IPPROTO_ESP;
96
97	esph->spi = x->id.spi;
98	esph->seq_no = htonl(++x->replay.oseq);
99	xfrm_aevent_doreplay(x);
100
101	if (esp->conf.ivlen) {
102		if (unlikely(!esp->conf.ivinitted)) {
103			get_random_bytes(esp->conf.ivec, esp->conf.ivlen);
104			esp->conf.ivinitted = 1;
105		}
106		crypto_blkcipher_set_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
107	}
108
109	do {
110		struct scatterlist *sg = &esp->sgbuf[0];
111
112		if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
113			sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
114			if (!sg)
115				goto error;
116		}
117		skb_to_sgvec(skb, sg, esph->enc_data+esp->conf.ivlen-skb->data, clen);
118		err = crypto_blkcipher_encrypt(&desc, sg, sg, clen);
119		if (unlikely(sg != &esp->sgbuf[0]))
120			kfree(sg);
121	} while (0);
122
123	if (unlikely(err))
124		goto error;
125
126	if (esp->conf.ivlen) {
127		memcpy(esph->enc_data, esp->conf.ivec, esp->conf.ivlen);
128		crypto_blkcipher_get_iv(tfm, esp->conf.ivec, esp->conf.ivlen);
129	}
130
131	if (esp->auth.icv_full_len) {
132		err = esp_mac_digest(esp, skb, (u8 *)esph - skb->data,
133				     sizeof(*esph) + esp->conf.ivlen + clen);
134		memcpy(pskb_put(skb, trailer, alen), esp->auth.work_icv, alen);
135	}
136
137	ip_send_check(top_iph);
138
139error:
140	return err;
141}
142
143/*
144 * Note: detecting truncated vs. non-truncated authentication data is very
145 * expensive, so we only support truncated data, which is the recommended
146 * and common case.
147 */
148static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
149{
150	struct iphdr *iph;
151	struct ip_esp_hdr *esph;
152	struct esp_data *esp = x->data;
153	struct crypto_blkcipher *tfm = esp->conf.tfm;
154	struct blkcipher_desc desc = { .tfm = tfm };
155	struct sk_buff *trailer;
156	int blksize = ALIGN(crypto_blkcipher_blocksize(tfm), 4);
157	int alen = esp->auth.icv_trunc_len;
158	int elen = skb->len - sizeof(struct ip_esp_hdr) - esp->conf.ivlen - alen;
159	int nfrags;
160	int ihl;
161	u8 nexthdr[2];
162	struct scatterlist *sg;
163	int padlen;
164	int err;
165
166	if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr)))
167		goto out;
168
169	if (elen <= 0 || (elen & (blksize-1)))
170		goto out;
171
172	/* If integrity check is required, do this. */
173	if (esp->auth.icv_full_len) {
174		u8 sum[alen];
175
176		err = esp_mac_digest(esp, skb, 0, skb->len - alen);
177		if (err)
178			goto out;
179
180		if (skb_copy_bits(skb, skb->len - alen, sum, alen))
181			BUG();
182
183		if (unlikely(memcmp(esp->auth.work_icv, sum, alen))) {
184			x->stats.integrity_failed++;
185			goto out;
186		}
187	}
188
189	if ((nfrags = skb_cow_data(skb, 0, &trailer)) < 0)
190		goto out;
191
192	skb->ip_summed = CHECKSUM_NONE;
193
194	esph = (struct ip_esp_hdr*)skb->data;
195
196	/* Get ivec. This can be wrong, check against another impls. */
197	if (esp->conf.ivlen)
198		crypto_blkcipher_set_iv(tfm, esph->enc_data, esp->conf.ivlen);
199
200	sg = &esp->sgbuf[0];
201
202	if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
203		sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
204		if (!sg)
205			goto out;
206	}
207	skb_to_sgvec(skb, sg, sizeof(struct ip_esp_hdr) + esp->conf.ivlen, elen);
208	err = crypto_blkcipher_decrypt(&desc, sg, sg, elen);
209	if (unlikely(sg != &esp->sgbuf[0]))
210		kfree(sg);
211	if (unlikely(err))
212		return err;
213
214	if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
215		BUG();
216
217	padlen = nexthdr[0];
218	if (padlen+2 >= elen)
219		goto out;
220
221	/* ... check padding bits here. Silly. :-) */
222
223	iph = ip_hdr(skb);
224	ihl = iph->ihl * 4;
225
226	if (x->encap) {
227		struct xfrm_encap_tmpl *encap = x->encap;
228		struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
229
230		/*
231		 * 1) if the NAT-T peer's IP or port changed then
232		 *    advertize the change to the keying daemon.
233		 *    This is an inbound SA, so just compare
234		 *    SRC ports.
235		 */
236		if (iph->saddr != x->props.saddr.a4 ||
237		    uh->source != encap->encap_sport) {
238			xfrm_address_t ipaddr;
239
240			ipaddr.a4 = iph->saddr;
241			km_new_mapping(x, &ipaddr, uh->source);
242
243			/* XXX: perhaps add an extra
244			 * policy check here, to see
245			 * if we should allow or
246			 * reject a packet from a
247			 * different source
248			 * address/port.
249			 */
250		}
251
252		/*
253		 * 2) ignore UDP/TCP checksums in case
254		 *    of NAT-T in Transport Mode, or
255		 *    perform other post-processing fixes
256		 *    as per draft-ietf-ipsec-udp-encaps-06,
257		 *    section 3.1.2
258		 */
259		if (x->props.mode == XFRM_MODE_TRANSPORT ||
260		    x->props.mode == XFRM_MODE_BEET)
261			skb->ip_summed = CHECKSUM_UNNECESSARY;
262	}
263
264	iph->protocol = nexthdr[1];
265	pskb_trim(skb, skb->len - alen - padlen - 2);
266	__skb_pull(skb, sizeof(*esph) + esp->conf.ivlen);
267	skb_set_transport_header(skb, -ihl);
268
269	return 0;
270
271out:
272	return -EINVAL;
273}
274
275static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
276{
277	struct esp_data *esp = x->data;
278	u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
279	u32 align = max_t(u32, blksize, esp->conf.padlen);
280	u32 rem;
281
282	mtu -= x->props.header_len + esp->auth.icv_trunc_len;
283	rem = mtu & (align - 1);
284	mtu &= ~(align - 1);
285
286	switch (x->props.mode) {
287	case XFRM_MODE_TUNNEL:
288		break;
289	default:
290	case XFRM_MODE_TRANSPORT:
291		/* The worst case */
292		mtu -= blksize - 4;
293		mtu += min_t(u32, blksize - 4, rem);
294		break;
295	case XFRM_MODE_BEET:
296		/* The worst case. */
297		mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
298		break;
299	}
300
301	return mtu - 2;
302}
303
304static void esp4_err(struct sk_buff *skb, u32 info)
305{
306	struct iphdr *iph = (struct iphdr*)skb->data;
307	struct ip_esp_hdr *esph = (struct ip_esp_hdr*)(skb->data+(iph->ihl<<2));
308	struct xfrm_state *x;
309
310	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
311	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
312		return;
313
314	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, esph->spi, IPPROTO_ESP, AF_INET);
315	if (!x)
316		return;
317	NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x\n",
318		 ntohl(esph->spi), ntohl(iph->daddr));
319	xfrm_state_put(x);
320}
321
322static void esp_destroy(struct xfrm_state *x)
323{
324	struct esp_data *esp = x->data;
325
326	if (!esp)
327		return;
328
329	crypto_free_blkcipher(esp->conf.tfm);
330	esp->conf.tfm = NULL;
331	kfree(esp->conf.ivec);
332	esp->conf.ivec = NULL;
333	crypto_free_hash(esp->auth.tfm);
334	esp->auth.tfm = NULL;
335	kfree(esp->auth.work_icv);
336	esp->auth.work_icv = NULL;
337	kfree(esp);
338}
339
340static int esp_init_state(struct xfrm_state *x)
341{
342	struct esp_data *esp = NULL;
343	struct crypto_blkcipher *tfm;
344	u32 align;
345
346	/* null auth and encryption can have zero length keys */
347	if (x->aalg) {
348		if (x->aalg->alg_key_len > 512)
349			goto error;
350	}
351	if (x->ealg == NULL)
352		goto error;
353
354	esp = kzalloc(sizeof(*esp), GFP_KERNEL);
355	if (esp == NULL)
356		return -ENOMEM;
357
358	if (x->aalg) {
359		struct xfrm_algo_desc *aalg_desc;
360		struct crypto_hash *hash;
361
362		esp->auth.key = x->aalg->alg_key;
363		esp->auth.key_len = (x->aalg->alg_key_len+7)/8;
364		hash = crypto_alloc_hash(x->aalg->alg_name, 0,
365					 CRYPTO_ALG_ASYNC);
366		if (IS_ERR(hash))
367			goto error;
368
369		esp->auth.tfm = hash;
370		if (crypto_hash_setkey(hash, esp->auth.key, esp->auth.key_len))
371			goto error;
372
373		aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
374		BUG_ON(!aalg_desc);
375
376		if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
377		    crypto_hash_digestsize(hash)) {
378			NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu\n",
379				 x->aalg->alg_name,
380				 crypto_hash_digestsize(hash),
381				 aalg_desc->uinfo.auth.icv_fullbits/8);
382			goto error;
383		}
384
385		esp->auth.icv_full_len = aalg_desc->uinfo.auth.icv_fullbits/8;
386		esp->auth.icv_trunc_len = aalg_desc->uinfo.auth.icv_truncbits/8;
387
388		esp->auth.work_icv = kmalloc(esp->auth.icv_full_len, GFP_KERNEL);
389		if (!esp->auth.work_icv)
390			goto error;
391	}
392	esp->conf.key = x->ealg->alg_key;
393	esp->conf.key_len = (x->ealg->alg_key_len+7)/8;
394	tfm = crypto_alloc_blkcipher(x->ealg->alg_name, 0, CRYPTO_ALG_ASYNC);
395	if (IS_ERR(tfm))
396		goto error;
397	esp->conf.tfm = tfm;
398	esp->conf.ivlen = crypto_blkcipher_ivsize(tfm);
399	esp->conf.padlen = 0;
400	if (esp->conf.ivlen) {
401		esp->conf.ivec = kmalloc(esp->conf.ivlen, GFP_KERNEL);
402		if (unlikely(esp->conf.ivec == NULL))
403			goto error;
404		esp->conf.ivinitted = 0;
405	}
406	if (crypto_blkcipher_setkey(tfm, esp->conf.key, esp->conf.key_len))
407		goto error;
408	x->props.header_len = sizeof(struct ip_esp_hdr) + esp->conf.ivlen;
409	if (x->props.mode == XFRM_MODE_TUNNEL)
410		x->props.header_len += sizeof(struct iphdr);
411	else if (x->props.mode == XFRM_MODE_BEET)
412		x->props.header_len += IPV4_BEET_PHMAXLEN;
413	if (x->encap) {
414		struct xfrm_encap_tmpl *encap = x->encap;
415
416		switch (encap->encap_type) {
417		default:
418			goto error;
419		case UDP_ENCAP_ESPINUDP:
420			x->props.header_len += sizeof(struct udphdr);
421			break;
422		case UDP_ENCAP_ESPINUDP_NON_IKE:
423			x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
424			break;
425		}
426	}
427	x->data = esp;
428	align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
429	if (esp->conf.padlen)
430		align = max_t(u32, align, esp->conf.padlen);
431	x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
432	return 0;
433
434error:
435	x->data = esp;
436	esp_destroy(x);
437	x->data = NULL;
438	return -EINVAL;
439}
440
441static struct xfrm_type esp_type =
442{
443	.description	= "ESP4",
444	.owner		= THIS_MODULE,
445	.proto	     	= IPPROTO_ESP,
446	.init_state	= esp_init_state,
447	.destructor	= esp_destroy,
448	.get_mtu	= esp4_get_mtu,
449	.input		= esp_input,
450	.output		= esp_output
451};
452
453static struct net_protocol esp4_protocol = {
454	.handler	=	xfrm4_rcv,
455	.err_handler	=	esp4_err,
456	.no_policy	=	1,
457};
458
459static int __init esp4_init(void)
460{
461	if (xfrm_register_type(&esp_type, AF_INET) < 0) {
462		printk(KERN_INFO "ip esp init: can't add xfrm type\n");
463		return -EAGAIN;
464	}
465	if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
466		printk(KERN_INFO "ip esp init: can't add protocol\n");
467		xfrm_unregister_type(&esp_type, AF_INET);
468		return -EAGAIN;
469	}
470	return 0;
471}
472
473static void __exit esp4_fini(void)
474{
475	if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
476		printk(KERN_INFO "ip esp close: can't remove protocol\n");
477	if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
478		printk(KERN_INFO "ip esp close: can't remove xfrm type\n");
479}
480
481module_init(esp4_init);
482module_exit(esp4_fini);
483MODULE_LICENSE("GPL");
484