// SPDX-License-Identifier: GPL-2.0-or-later /* * SR-IPv6 implementation -- HMAC functions * * Author: * David Lebrun <david.lebrun@uclouvain.be> */ #include <linux/errno.h> #include <linux/kernel.h> #include <linux/types.h> #include <linux/socket.h> #include <linux/sockios.h> #include <linux/net.h> #include <linux/netdevice.h> #include <linux/in6.h> #include <linux/icmpv6.h> #include <linux/mroute6.h> #include <linux/slab.h> #include <linux/rhashtable.h> #include <linux/netfilter.h> #include <linux/netfilter_ipv6.h> #include <net/sock.h> #include <net/snmp.h> #include <net/ipv6.h> #include <net/protocol.h> #include <net/transp_v6.h> #include <net/rawv6.h> #include <net/ndisc.h> #include <net/ip6_route.h> #include <net/addrconf.h> #include <net/xfrm.h> #include <linux/cryptohash.h> #include <crypto/hash.h> #include <crypto/sha.h> #include <net/seg6.h> #include <net/genetlink.h> #include <net/seg6_hmac.h> #include <linux/random.h> static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring); static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj) { const struct seg6_hmac_info *hinfo = obj; return (hinfo->hmackeyid != *(__u32 *)arg->key); } static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo) { kfree_rcu(hinfo, rcu); } static void seg6_free_hi(void *ptr, void *arg) { struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr; if (hinfo) seg6_hinfo_release(hinfo); } static const struct rhashtable_params rht_params = { .head_offset = offsetof(struct seg6_hmac_info, node), .key_offset = offsetof(struct seg6_hmac_info, hmackeyid), .key_len = sizeof(u32), .automatic_shrinking = true, .obj_cmpfn = seg6_hmac_cmpfn, }; static struct seg6_hmac_algo hmac_algos[] = { { .alg_id = SEG6_HMAC_ALGO_SHA1, .name = "hmac(sha1)", }, { .alg_id = SEG6_HMAC_ALGO_SHA256, .name = "hmac(sha256)", }, }; static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh) { struct sr6_tlv_hmac *tlv; if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5) return NULL; if (!sr_has_hmac(srh)) return NULL; tlv = (struct sr6_tlv_hmac *) ((char *)srh + ((srh->hdrlen + 1) << 3) - 40); if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38) return NULL; return tlv; } static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id) { struct seg6_hmac_algo *algo; int i, alg_count; alg_count = ARRAY_SIZE(hmac_algos); for (i = 0; i < alg_count; i++) { algo = &hmac_algos[i]; if (algo->alg_id == alg_id) return algo; } return NULL; } static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize, u8 *output, int outlen) { struct seg6_hmac_algo *algo; struct crypto_shash *tfm; struct shash_desc *shash; int ret, dgsize; algo = __hmac_get_algo(hinfo->alg_id); if (!algo) return -ENOENT; tfm = *this_cpu_ptr(algo->tfms); dgsize = crypto_shash_digestsize(tfm); if (dgsize > outlen) { pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n", dgsize, outlen); return -ENOMEM; } ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen); if (ret < 0) { pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret); goto failed; } shash = *this_cpu_ptr(algo->shashs); shash->tfm = tfm; ret = crypto_shash_digest(shash, text, psize, output); if (ret < 0) { pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret); goto failed; } return dgsize; failed: return ret; } int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr, struct in6_addr *saddr, u8 *output) { __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid); u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE]; int plen, i, dgsize, wrsize; char *ring, *off; /* a 160-byte buffer for digest output allows to store highest known * hash function (RadioGatun) with up to 1216 bits */ /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */ plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16; /* this limit allows for 14 segments */ if (plen >= SEG6_HMAC_RING_SIZE) return -EMSGSIZE; /* Let's build the HMAC text on the ring buffer. The text is composed * as follows, in order: * * 1. Source IPv6 address (128 bits) * 2. first_segment value (8 bits) * 3. Flags (8 bits) * 4. HMAC Key ID (32 bits) * 5. All segments in the segments list (n * 128 bits) */ local_bh_disable(); ring = this_cpu_ptr(hmac_ring); off = ring; /* source address */ memcpy(off, saddr, 16); off += 16; /* first_segment value */ *off++ = hdr->first_segment; /* flags */ *off++ = hdr->flags; /* HMAC Key ID */ memcpy(off, &hmackeyid, 4); off += 4; /* all segments in the list */ for (i = 0; i < hdr->first_segment + 1; i++) { memcpy(off, hdr->segments + i, 16); off += 16; } dgsize = __do_hmac(hinfo, ring, plen, tmp_out, SEG6_HMAC_MAX_DIGESTSIZE); local_bh_enable(); if (dgsize < 0) return dgsize; wrsize = SEG6_HMAC_FIELD_LEN; if (wrsize > dgsize) wrsize = dgsize; memset(output, 0, SEG6_HMAC_FIELD_LEN); memcpy(output, tmp_out, wrsize); return 0; } EXPORT_SYMBOL(seg6_hmac_compute); /* checks if an incoming SR-enabled packet's HMAC status matches * the incoming policy. * * called with rcu_read_lock() */ bool seg6_hmac_validate_skb(struct sk_buff *skb) { u8 hmac_output[SEG6_HMAC_FIELD_LEN]; struct net *net = dev_net(skb->dev); struct seg6_hmac_info *hinfo; struct sr6_tlv_hmac *tlv; struct ipv6_sr_hdr *srh; struct inet6_dev *idev; idev = __in6_dev_get(skb->dev); srh = (struct ipv6_sr_hdr *)skb_transport_header(skb); tlv = seg6_get_tlv_hmac(srh); /* mandatory check but no tlv */ if (idev->cnf.seg6_require_hmac > 0 && !tlv) return false; /* no check */ if (idev->cnf.seg6_require_hmac < 0) return true; /* check only if present */ if (idev->cnf.seg6_require_hmac == 0 && !tlv) return true; /* now, seg6_require_hmac >= 0 && tlv */ hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid)); if (!hinfo) return false; if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output)) return false; if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0) return false; return true; } EXPORT_SYMBOL(seg6_hmac_validate_skb); /* called with rcu_read_lock() */ struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key) { struct seg6_pernet_data *sdata = seg6_pernet(net); struct seg6_hmac_info *hinfo; hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params); return hinfo; } EXPORT_SYMBOL(seg6_hmac_info_lookup); int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo) { struct seg6_pernet_data *sdata = seg6_pernet(net); int err; err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node, rht_params); return err; } EXPORT_SYMBOL(seg6_hmac_info_add); int seg6_hmac_info_del(struct net *net, u32 key) { struct seg6_pernet_data *sdata = seg6_pernet(net); struct seg6_hmac_info *hinfo; int err = -ENOENT; hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params); if (!hinfo) goto out; err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node, rht_params); if (err) goto out; seg6_hinfo_release(hinfo); out: return err; } EXPORT_SYMBOL(seg6_hmac_info_del); int seg6_push_hmac(struct net *net, struct in6_addr *saddr, struct ipv6_sr_hdr *srh) { struct seg6_hmac_info *hinfo; struct sr6_tlv_hmac *tlv; int err = -ENOENT; tlv = seg6_get_tlv_hmac(srh); if (!tlv) return -EINVAL; rcu_read_lock(); hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid)); if (!hinfo) goto out; memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN); err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac); out: rcu_read_unlock(); return err; } EXPORT_SYMBOL(seg6_push_hmac); static int seg6_hmac_init_algo(void) { struct seg6_hmac_algo *algo; struct crypto_shash *tfm; struct shash_desc *shash; int i, alg_count, cpu; alg_count = ARRAY_SIZE(hmac_algos); for (i = 0; i < alg_count; i++) { struct crypto_shash **p_tfm; int shsize; algo = &hmac_algos[i]; algo->tfms = alloc_percpu(struct crypto_shash *); if (!algo->tfms) return -ENOMEM; for_each_possible_cpu(cpu) { tfm = crypto_alloc_shash(algo->name, 0, 0); if (IS_ERR(tfm)) return PTR_ERR(tfm); p_tfm = per_cpu_ptr(algo->tfms, cpu); *p_tfm = tfm; } p_tfm = raw_cpu_ptr(algo->tfms); tfm = *p_tfm; shsize = sizeof(*shash) + crypto_shash_descsize(tfm); algo->shashs = alloc_percpu(struct shash_desc *); if (!algo->shashs) return -ENOMEM; for_each_possible_cpu(cpu) { shash = kzalloc_node(shsize, GFP_KERNEL, cpu_to_node(cpu)); if (!shash) return -ENOMEM; *per_cpu_ptr(algo->shashs, cpu) = shash; } } return 0; } int __init seg6_hmac_init(void) { return seg6_hmac_init_algo(); } EXPORT_SYMBOL(seg6_hmac_init); int __net_init seg6_hmac_net_init(struct net *net) { struct seg6_pernet_data *sdata = seg6_pernet(net); rhashtable_init(&sdata->hmac_infos, &rht_params); return 0; } EXPORT_SYMBOL(seg6_hmac_net_init); void seg6_hmac_exit(void) { struct seg6_hmac_algo *algo = NULL; int i, alg_count, cpu; alg_count = ARRAY_SIZE(hmac_algos); for (i = 0; i < alg_count; i++) { algo = &hmac_algos[i]; for_each_possible_cpu(cpu) { struct crypto_shash *tfm; struct shash_desc *shash; shash = *per_cpu_ptr(algo->shashs, cpu); kfree(shash); tfm = *per_cpu_ptr(algo->tfms, cpu); crypto_free_shash(tfm); } free_percpu(algo->tfms); free_percpu(algo->shashs); } } EXPORT_SYMBOL(seg6_hmac_exit); void __net_exit seg6_hmac_net_exit(struct net *net) { struct seg6_pernet_data *sdata = seg6_pernet(net); rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL); } EXPORT_SYMBOL(seg6_hmac_net_exit);