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 44 struct hmac_storage { 45 local_lock_t bh_lock; 46 char hmac_ring[SEG6_HMAC_RING_SIZE]; 47 }; 48 49 static DEFINE_PER_CPU(struct hmac_storage, hmac_storage) = { 50 .bh_lock = INIT_LOCAL_LOCK(bh_lock), 51 }; 52 53 static 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 60 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo) 61 { 62 kfree_rcu(hinfo, rcu); 63 } 64 65 static 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 73 static 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 81 static 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 } 99 100 int 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 } 169 EXPORT_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 */ 176 bool 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); 187 188 srh = (struct ipv6_sr_hdr *)skb_transport_header(skb); 189 190 tlv = seg6_get_tlv_hmac(srh); 191 192 require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac); 193 /* mandatory check but no tlv */ 194 if (require_hmac > 0 && !tlv) 195 return false; 196 197 /* no check */ 198 if (require_hmac < 0) 199 return true; 200 201 /* check only if present */ 202 if (require_hmac == 0 && !tlv) 203 return true; 204 205 /* now, seg6_require_hmac >= 0 && tlv */ 206 207 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid)); 208 if (!hinfo) 209 return false; 210 211 if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output)) 212 return false; 213 214 if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN)) 215 return false; 216 217 return true; 218 } 219 EXPORT_SYMBOL(seg6_hmac_validate_skb); 220 221 /* called with rcu_read_lock() */ 222 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key) 223 { 224 struct seg6_pernet_data *sdata = seg6_pernet(net); 225 struct seg6_hmac_info *hinfo; 226 227 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params); 228 229 return hinfo; 230 } 231 EXPORT_SYMBOL(seg6_hmac_info_lookup); 232 233 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo) 234 { 235 struct seg6_pernet_data *sdata = seg6_pernet(net); 236 int err; 237 238 switch (hinfo->alg_id) { 239 case SEG6_HMAC_ALGO_SHA1: 240 hmac_sha1_preparekey(&hinfo->key.sha1, 241 hinfo->secret, hinfo->slen); 242 break; 243 case SEG6_HMAC_ALGO_SHA256: 244 hmac_sha256_preparekey(&hinfo->key.sha256, 245 hinfo->secret, hinfo->slen); 246 break; 247 default: 248 return -EINVAL; 249 } 250 251 err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node, 252 rht_params); 253 254 return err; 255 } 256 EXPORT_SYMBOL(seg6_hmac_info_add); 257 258 int seg6_hmac_info_del(struct net *net, u32 key) 259 { 260 struct seg6_pernet_data *sdata = seg6_pernet(net); 261 struct seg6_hmac_info *hinfo; 262 int err = -ENOENT; 263 264 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params); 265 if (!hinfo) 266 goto out; 267 268 err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node, 269 rht_params); 270 if (err) 271 goto out; 272 273 seg6_hinfo_release(hinfo); 274 275 out: 276 return err; 277 } 278 EXPORT_SYMBOL(seg6_hmac_info_del); 279 280 int seg6_push_hmac(struct net *net, struct in6_addr *saddr, 281 struct ipv6_sr_hdr *srh) 282 { 283 struct seg6_hmac_info *hinfo; 284 struct sr6_tlv_hmac *tlv; 285 int err = -ENOENT; 286 287 tlv = seg6_get_tlv_hmac(srh); 288 if (!tlv) 289 return -EINVAL; 290 291 rcu_read_lock(); 292 293 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid)); 294 if (!hinfo) 295 goto out; 296 297 memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN); 298 err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac); 299 300 out: 301 rcu_read_unlock(); 302 return err; 303 } 304 EXPORT_SYMBOL(seg6_push_hmac); 305 306 int __net_init seg6_hmac_net_init(struct net *net) 307 { 308 struct seg6_pernet_data *sdata = seg6_pernet(net); 309 310 return rhashtable_init(&sdata->hmac_infos, &rht_params); 311 } 312 313 void __net_exit seg6_hmac_net_exit(struct net *net) 314 { 315 struct seg6_pernet_data *sdata = seg6_pernet(net); 316 317 rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL); 318 } 319 EXPORT_SYMBOL(seg6_hmac_net_exit); 320