seg6_hmac.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 *  SR-IPv6 implementation -- HMAC functions
  4 *
  5 *  Author:
  6 *  David Lebrun <david.lebrun@uclouvain.be>
  7 */
  8
  9#include <linux/errno.h>
 10#include <linux/kernel.h>
 11#include <linux/types.h>
 12#include <linux/socket.h>
 13#include <linux/sockios.h>
 14#include <linux/net.h>
 15#include <linux/netdevice.h>
 16#include <linux/in6.h>
 17#include <linux/icmpv6.h>
 18#include <linux/mroute6.h>
 19#include <linux/rhashtable.h>
 20
 21#include <linux/netfilter.h>
 22#include <linux/netfilter_ipv6.h>
 23
 24#include <net/sock.h>
 25#include <net/snmp.h>
 26
 27#include <net/ipv6.h>
 28#include <net/protocol.h>
 29#include <net/transp_v6.h>
 30#include <net/rawv6.h>
 31#include <net/ndisc.h>
 32#include <net/ip6_route.h>
 33#include <net/addrconf.h>
 34#include <net/xfrm.h>
 35
 36#include <crypto/sha1.h>
 37#include <crypto/sha2.h>
 38#include <crypto/utils.h>
 39#include <net/seg6.h>
 40#include <net/genetlink.h>
 41#include <net/seg6_hmac.h>
 42#include <linux/random.h>
 43
 44struct hmac_storage {
 45	local_lock_t bh_lock;
 46	char hmac_ring[SEG6_HMAC_RING_SIZE];
 47};
 48
 49static DEFINE_PER_CPU(struct hmac_storage, hmac_storage) = {
 50	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
 51};
 52
 53static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
 54{
 55	const struct seg6_hmac_info *hinfo = obj;
 56
 57	return (hinfo->hmackeyid != *(__u32 *)arg->key);
 58}
 59
 60static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
 61{
 62	kfree_rcu(hinfo, rcu);
 63}
 64
 65static void seg6_free_hi(void *ptr, void *arg)
 66{
 67	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
 68
 69	if (hinfo)
 70		seg6_hinfo_release(hinfo);
 71}
 72
 73static const struct rhashtable_params rht_params = {
 74	.head_offset		= offsetof(struct seg6_hmac_info, node),
 75	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
 76	.key_len		= sizeof(u32),
 77	.automatic_shrinking	= true,
 78	.obj_cmpfn		= seg6_hmac_cmpfn,
 79};
 80
 81static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
 82{
 83	struct sr6_tlv_hmac *tlv;
 84
 85	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
 86		return NULL;
 87
 88	if (!sr_has_hmac(srh))
 89		return NULL;
 90
 91	tlv = (struct sr6_tlv_hmac *)
 92	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
 93
 94	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
 95		return NULL;
 96
 97	return tlv;
 98}
 99
100int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
101		      struct in6_addr *saddr, u8 *output)
102{
103	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
104	int plen, i, ret = 0;
105	char *ring, *off;
106
107	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
108	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
109
110	/* this limit allows for 14 segments */
111	if (plen >= SEG6_HMAC_RING_SIZE)
112		return -EMSGSIZE;
113
114	/* Let's build the HMAC text on the ring buffer. The text is composed
115	 * as follows, in order:
116	 *
117	 * 1. Source IPv6 address (128 bits)
118	 * 2. first_segment value (8 bits)
119	 * 3. Flags (8 bits)
120	 * 4. HMAC Key ID (32 bits)
121	 * 5. All segments in the segments list (n * 128 bits)
122	 */
123
124	local_bh_disable();
125	local_lock_nested_bh(&hmac_storage.bh_lock);
126	ring = this_cpu_ptr(hmac_storage.hmac_ring);
127	off = ring;
128
129	/* source address */
130	memcpy(off, saddr, 16);
131	off += 16;
132
133	/* first_segment value */
134	*off++ = hdr->first_segment;
135
136	/* flags */
137	*off++ = hdr->flags;
138
139	/* HMAC Key ID */
140	memcpy(off, &hmackeyid, 4);
141	off += 4;
142
143	/* all segments in the list */
144	for (i = 0; i < hdr->first_segment + 1; i++) {
145		memcpy(off, hdr->segments + i, 16);
146		off += 16;
147	}
148
149	switch (hinfo->alg_id) {
150	case SEG6_HMAC_ALGO_SHA1:
151		hmac_sha1(&hinfo->key.sha1, ring, plen, output);
152		static_assert(SEG6_HMAC_FIELD_LEN > SHA1_DIGEST_SIZE);
153		memset(&output[SHA1_DIGEST_SIZE], 0,
154		       SEG6_HMAC_FIELD_LEN - SHA1_DIGEST_SIZE);
155		break;
156	case SEG6_HMAC_ALGO_SHA256:
157		hmac_sha256(&hinfo->key.sha256, ring, plen, output);
158		static_assert(SEG6_HMAC_FIELD_LEN == SHA256_DIGEST_SIZE);
159		break;
160	default:
161		WARN_ON_ONCE(1);
162		ret = -EINVAL;
163		break;
164	}
165	local_unlock_nested_bh(&hmac_storage.bh_lock);
166	local_bh_enable();
167	return ret;
168}
169EXPORT_SYMBOL(seg6_hmac_compute);
170
171/* checks if an incoming SR-enabled packet's HMAC status matches
172 * the incoming policy.
173 *
174 * called with rcu_read_lock()
175 */
176bool seg6_hmac_validate_skb(struct sk_buff *skb)
177{
178	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
179	struct net *net = dev_net(skb->dev);
180	struct seg6_hmac_info *hinfo;
181	struct sr6_tlv_hmac *tlv;
182	struct ipv6_sr_hdr *srh;
183	struct inet6_dev *idev;
184	int require_hmac;
185
186	idev = __in6_dev_get(skb->dev);
187	if (!idev)
188		return false;
189
190	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
191
192	tlv = seg6_get_tlv_hmac(srh);
193
194	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
195	/* mandatory check but no tlv */
196	if (require_hmac > 0 && !tlv)
197		return false;
198
199	/* no check */
200	if (require_hmac < 0)
201		return true;
202
203	/* check only if present */
204	if (require_hmac == 0 && !tlv)
205		return true;
206
207	/* now, seg6_require_hmac >= 0 && tlv */
208
209	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
210	if (!hinfo)
211		return false;
212
213	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
214		return false;
215
216	if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN))
217		return false;
218
219	return true;
220}
221EXPORT_SYMBOL(seg6_hmac_validate_skb);
222
223/* called with rcu_read_lock() */
224struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
225{
226	struct seg6_pernet_data *sdata = seg6_pernet(net);
227	struct seg6_hmac_info *hinfo;
228
229	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
230
231	return hinfo;
232}
233EXPORT_SYMBOL(seg6_hmac_info_lookup);
234
235int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
236{
237	struct seg6_pernet_data *sdata = seg6_pernet(net);
238	int err;
239
240	switch (hinfo->alg_id) {
241	case SEG6_HMAC_ALGO_SHA1:
242		hmac_sha1_preparekey(&hinfo->key.sha1,
243				     hinfo->secret, hinfo->slen);
244		break;
245	case SEG6_HMAC_ALGO_SHA256:
246		hmac_sha256_preparekey(&hinfo->key.sha256,
247				       hinfo->secret, hinfo->slen);
248		break;
249	default:
250		return -EINVAL;
251	}
252
253	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
254					    rht_params);
255
256	return err;
257}
258EXPORT_SYMBOL(seg6_hmac_info_add);
259
260int seg6_hmac_info_del(struct net *net, u32 key)
261{
262	struct seg6_pernet_data *sdata = seg6_pernet(net);
263	struct seg6_hmac_info *hinfo;
264	int err = -ENOENT;
265
266	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
267	if (!hinfo)
268		goto out;
269
270	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
271				     rht_params);
272	if (err)
273		goto out;
274
275	seg6_hinfo_release(hinfo);
276
277out:
278	return err;
279}
280EXPORT_SYMBOL(seg6_hmac_info_del);
281
282int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
283		   struct ipv6_sr_hdr *srh)
284{
285	struct seg6_hmac_info *hinfo;
286	struct sr6_tlv_hmac *tlv;
287	int err = -ENOENT;
288
289	tlv = seg6_get_tlv_hmac(srh);
290	if (!tlv)
291		return -EINVAL;
292
293	rcu_read_lock();
294
295	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
296	if (!hinfo)
297		goto out;
298
299	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
300	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
301
302out:
303	rcu_read_unlock();
304	return err;
305}
306EXPORT_SYMBOL(seg6_push_hmac);
307
308int __net_init seg6_hmac_net_init(struct net *net)
309{
310	struct seg6_pernet_data *sdata = seg6_pernet(net);
311
312	return rhashtable_init(&sdata->hmac_infos, &rht_params);
313}
314
315void __net_exit seg6_hmac_net_exit(struct net *net)
316{
317	struct seg6_pernet_data *sdata = seg6_pernet(net);
318
319	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
320}
321EXPORT_SYMBOL(seg6_hmac_net_exit);