net/bridge/netfilter/nft_reject_bridge.c

   1 /*
   2  * Copyright (c) 2014 Pablo Neira Ayuso <pablo@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/init.h>
  11 #include <linux/module.h>
  12 #include <linux/netlink.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/netfilter/nf_tables.h>
  15 #include <net/netfilter/nf_tables.h>
  16 #include <net/netfilter/nft_reject.h>
  17 #include <net/netfilter/nf_tables_bridge.h>
  18 #include <net/netfilter/ipv4/nf_reject.h>
  19 #include <net/netfilter/ipv6/nf_reject.h>
  20 #include <linux/ip.h>
  21 #include <net/ip.h>
  22 #include <net/ip6_checksum.h>
  23 #include <linux/netfilter_bridge.h>
  24 #include <linux/netfilter_ipv6.h>
  25 #include "../br_private.h"
  26
  27 static void nft_reject_br_push_etherhdr(struct sk_buff *oldskb,
  28                                         struct sk_buff *nskb)
  29 {
  30         struct ethhdr *eth;
  31
  32         eth = (struct ethhdr *)skb_push(nskb, ETH_HLEN);
  33         skb_reset_mac_header(nskb);
  34         ether_addr_copy(eth->h_source, eth_hdr(oldskb)->h_dest);
  35         ether_addr_copy(eth->h_dest, eth_hdr(oldskb)->h_source);
  36         eth->h_proto = eth_hdr(oldskb)->h_proto;
  37         skb_pull(nskb, ETH_HLEN);
  38 }
  39
  40 /* We cannot use oldskb->dev, it can be either bridge device (NF_BRIDGE INPUT)
  41  * or the bridge port (NF_BRIDGE PREROUTING).
  42  */
  43 static void nft_reject_br_send_v4_tcp_reset(struct net *net,
  44                                             struct sk_buff *oldskb,
  45                                             const struct net_device *dev,
  46                                             int hook)
  47 {
  48         struct sk_buff *nskb;
  49         struct iphdr *niph;
  50         const struct tcphdr *oth;
  51         struct tcphdr _oth;
  52
  53         if (!nft_bridge_iphdr_validate(oldskb))
  54                 return;
  55
  56         oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
  57         if (!oth)
  58                 return;
  59
  60         nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
  61                          LL_MAX_HEADER, GFP_ATOMIC);
  62         if (!nskb)
  63                 return;
  64
  65         skb_reserve(nskb, LL_MAX_HEADER);
  66         niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
  67                                    net->ipv4.sysctl_ip_default_ttl);
  68         nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
  69         niph->ttl       = net->ipv4.sysctl_ip_default_ttl;
  70         niph->tot_len   = htons(nskb->len);
  71         ip_send_check(niph);
  72
  73         nft_reject_br_push_etherhdr(oldskb, nskb);
  74
  75         br_deliver(br_port_get_rcu(dev), nskb);
  76 }
  77
  78 static void nft_reject_br_send_v4_unreach(struct net *net,
  79                                           struct sk_buff *oldskb,
  80                                           const struct net_device *dev,
  81                                           int hook, u8 code)
  82 {
  83         struct sk_buff *nskb;
  84         struct iphdr *niph;
  85         struct icmphdr *icmph;
  86         unsigned int len;
  87         void *payload;
  88         __wsum csum;
  89         u8 proto;
  90
  91         if (oldskb->csum_bad || !nft_bridge_iphdr_validate(oldskb))
  92                 return;
  93
  94         /* IP header checks: fragment. */
  95         if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
  96                 return;
  97
  98         /* RFC says return as much as we can without exceeding 576 bytes. */
  99         len = min_t(unsigned int, 536, oldskb->len);
 100
 101         if (!pskb_may_pull(oldskb, len))
 102                 return;
 103
 104         if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len)))
 105                 return;
 106
 107         if (ip_hdr(oldskb)->protocol == IPPROTO_TCP ||
 108             ip_hdr(oldskb)->protocol == IPPROTO_UDP)
 109                 proto = ip_hdr(oldskb)->protocol;
 110         else
 111                 proto = 0;
 112
 113         if (!skb_csum_unnecessary(oldskb) &&
 114             nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto))
 115                 return;
 116
 117         nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmphdr) +
 118                          LL_MAX_HEADER + len, GFP_ATOMIC);
 119         if (!nskb)
 120                 return;
 121
 122         skb_reserve(nskb, LL_MAX_HEADER);
 123         niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_ICMP,
 124                                    net->ipv4.sysctl_ip_default_ttl);
 125
 126         skb_reset_transport_header(nskb);
 127         icmph = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr));
 128         memset(icmph, 0, sizeof(*icmph));
 129         icmph->type     = ICMP_DEST_UNREACH;
 130         icmph->code     = code;
 131
 132         payload = skb_put(nskb, len);
 133         memcpy(payload, skb_network_header(oldskb), len);
 134
 135         csum = csum_partial((void *)icmph, len + sizeof(struct icmphdr), 0);
 136         icmph->checksum = csum_fold(csum);
 137
 138         niph->tot_len   = htons(nskb->len);
 139         ip_send_check(niph);
 140
 141         nft_reject_br_push_etherhdr(oldskb, nskb);
 142
 143         br_deliver(br_port_get_rcu(dev), nskb);
 144 }
 145
 146 static void nft_reject_br_send_v6_tcp_reset(struct net *net,
 147                                             struct sk_buff *oldskb,
 148                                             const struct net_device *dev,
 149                                             int hook)
 150 {
 151         struct sk_buff *nskb;
 152         const struct tcphdr *oth;
 153         struct tcphdr _oth;
 154         unsigned int otcplen;
 155         struct ipv6hdr *nip6h;
 156
 157         if (!nft_bridge_ip6hdr_validate(oldskb))
 158                 return;
 159
 160         oth = nf_reject_ip6_tcphdr_get(oldskb, &_oth, &otcplen, hook);
 161         if (!oth)
 162                 return;
 163
 164         nskb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(struct tcphdr) +
 165                          LL_MAX_HEADER, GFP_ATOMIC);
 166         if (!nskb)
 167                 return;
 168
 169         skb_reserve(nskb, LL_MAX_HEADER);
 170         nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP,
 171                                      net->ipv6.devconf_all->hop_limit);
 172         nf_reject_ip6_tcphdr_put(nskb, oldskb, oth, otcplen);
 173         nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
 174
 175         nft_reject_br_push_etherhdr(oldskb, nskb);
 176
 177         br_deliver(br_port_get_rcu(dev), nskb);
 178 }
 179
 180 static bool reject6_br_csum_ok(struct sk_buff *skb, int hook)
 181 {
 182         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
 183         int thoff;
 184         __be16 fo;
 185         u8 proto = ip6h->nexthdr;
 186
 187         if (skb->csum_bad)
 188                 return false;
 189
 190         if (skb_csum_unnecessary(skb))
 191                 return true;
 192
 193         if (ip6h->payload_len &&
 194             pskb_trim_rcsum(skb, ntohs(ip6h->payload_len) + sizeof(*ip6h)))
 195                 return false;
 196
 197         thoff = ipv6_skip_exthdr(skb, ((u8*)(ip6h+1) - skb->data), &proto, &fo);
 198         if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0)
 199                 return false;
 200
 201         return nf_ip6_checksum(skb, hook, thoff, proto) == 0;
 202 }
 203
 204 static void nft_reject_br_send_v6_unreach(struct net *net,
 205                                           struct sk_buff *oldskb,
 206                                           const struct net_device *dev,
 207                                           int hook, u8 code)
 208 {
 209         struct sk_buff *nskb;
 210         struct ipv6hdr *nip6h;
 211         struct icmp6hdr *icmp6h;
 212         unsigned int len;
 213         void *payload;
 214
 215         if (!nft_bridge_ip6hdr_validate(oldskb))
 216                 return;
 217
 218         /* Include "As much of invoking packet as possible without the ICMPv6
 219          * packet exceeding the minimum IPv6 MTU" in the ICMP payload.
 220          */
 221         len = min_t(unsigned int, 1220, oldskb->len);
 222
 223         if (!pskb_may_pull(oldskb, len))
 224                 return;
 225
 226         if (!reject6_br_csum_ok(oldskb, hook))
 227                 return;
 228
 229         nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct icmp6hdr) +
 230                          LL_MAX_HEADER + len, GFP_ATOMIC);
 231         if (!nskb)
 232                 return;
 233
 234         skb_reserve(nskb, LL_MAX_HEADER);
 235         nip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_ICMPV6,
 236                                      net->ipv6.devconf_all->hop_limit);
 237
 238         skb_reset_transport_header(nskb);
 239         icmp6h = (struct icmp6hdr *)skb_put(nskb, sizeof(struct icmp6hdr));
 240         memset(icmp6h, 0, sizeof(*icmp6h));
 241         icmp6h->icmp6_type = ICMPV6_DEST_UNREACH;
 242         icmp6h->icmp6_code = code;
 243
 244         payload = skb_put(nskb, len);
 245         memcpy(payload, skb_network_header(oldskb), len);
 246         nip6h->payload_len = htons(nskb->len - sizeof(struct ipv6hdr));
 247
 248         icmp6h->icmp6_cksum =
 249                 csum_ipv6_magic(&nip6h->saddr, &nip6h->daddr,
 250                                 nskb->len - sizeof(struct ipv6hdr),
 251                                 IPPROTO_ICMPV6,
 252                                 csum_partial(icmp6h,
 253                                              nskb->len - sizeof(struct ipv6hdr),
 254                                              0));
 255
 256         nft_reject_br_push_etherhdr(oldskb, nskb);
 257
 258         br_deliver(br_port_get_rcu(dev), nskb);
 259 }
 260
 261 static void nft_reject_bridge_eval(const struct nft_expr *expr,
 262                                    struct nft_regs *regs,
 263                                    const struct nft_pktinfo *pkt)
 264 {
 265         struct nft_reject *priv = nft_expr_priv(expr);
 266         const unsigned char *dest = eth_hdr(pkt->skb)->h_dest;
 267
 268         if (is_broadcast_ether_addr(dest) ||
 269             is_multicast_ether_addr(dest))
 270                 goto out;
 271
 272         switch (eth_hdr(pkt->skb)->h_proto) {
 273         case htons(ETH_P_IP):
 274                 switch (priv->type) {
 275                 case NFT_REJECT_ICMP_UNREACH:
 276                         nft_reject_br_send_v4_unreach(pkt->net, pkt->skb,
 277                                                       pkt->in, pkt->hook,
 278                                                       priv->icmp_code);
 279                         break;
 280                 case NFT_REJECT_TCP_RST:
 281                         nft_reject_br_send_v4_tcp_reset(pkt->net, pkt->skb,
 282                                                         pkt->in, pkt->hook);
 283                         break;
 284                 case NFT_REJECT_ICMPX_UNREACH:
 285                         nft_reject_br_send_v4_unreach(pkt->net, pkt->skb,
 286                                                       pkt->in, pkt->hook,
 287                                                       nft_reject_icmp_code(priv->icmp_code));
 288                         break;
 289                 }
 290                 break;
 291         case htons(ETH_P_IPV6):
 292                 switch (priv->type) {
 293                 case NFT_REJECT_ICMP_UNREACH:
 294                         nft_reject_br_send_v6_unreach(pkt->net, pkt->skb,
 295                                                       pkt->in, pkt->hook,
 296                                                       priv->icmp_code);
 297                         break;
 298                 case NFT_REJECT_TCP_RST:
 299                         nft_reject_br_send_v6_tcp_reset(pkt->net, pkt->skb,
 300                                                         pkt->in, pkt->hook);
 301                         break;
 302                 case NFT_REJECT_ICMPX_UNREACH:
 303                         nft_reject_br_send_v6_unreach(pkt->net, pkt->skb,
 304                                                       pkt->in, pkt->hook,
 305                                                       nft_reject_icmpv6_code(priv->icmp_code));
 306                         break;
 307                 }
 308                 break;
 309         default:
 310                 /* No explicit way to reject this protocol, drop it. */
 311                 break;
 312         }
 313 out:
 314         regs->verdict.code = NF_DROP;
 315 }
 316
 317 static int nft_reject_bridge_validate(const struct nft_ctx *ctx,
 318                                       const struct nft_expr *expr,
 319                                       const struct nft_data **data)
 320 {
 321         return nft_chain_validate_hooks(ctx->chain, (1 << NF_BR_PRE_ROUTING) |
 322                                                     (1 << NF_BR_LOCAL_IN));
 323 }
 324
 325 static int nft_reject_bridge_init(const struct nft_ctx *ctx,
 326                                   const struct nft_expr *expr,
 327                                   const struct nlattr * const tb[])
 328 {
 329         struct nft_reject *priv = nft_expr_priv(expr);
 330         int icmp_code, err;
 331
 332         err = nft_reject_bridge_validate(ctx, expr, NULL);
 333         if (err < 0)
 334                 return err;
 335
 336         if (tb[NFTA_REJECT_TYPE] == NULL)
 337                 return -EINVAL;
 338
 339         priv->type = ntohl(nla_get_be32(tb[NFTA_REJECT_TYPE]));
 340         switch (priv->type) {
 341         case NFT_REJECT_ICMP_UNREACH:
 342         case NFT_REJECT_ICMPX_UNREACH:
 343                 if (tb[NFTA_REJECT_ICMP_CODE] == NULL)
 344                         return -EINVAL;
 345
 346                 icmp_code = nla_get_u8(tb[NFTA_REJECT_ICMP_CODE]);
 347                 if (priv->type == NFT_REJECT_ICMPX_UNREACH &&
 348                     icmp_code > NFT_REJECT_ICMPX_MAX)
 349                         return -EINVAL;
 350
 351                 priv->icmp_code = icmp_code;
 352                 break;
 353         case NFT_REJECT_TCP_RST:
 354                 break;
 355         default:
 356                 return -EINVAL;
 357         }
 358         return 0;
 359 }
 360
 361 static int nft_reject_bridge_dump(struct sk_buff *skb,
 362                                   const struct nft_expr *expr)
 363 {
 364         const struct nft_reject *priv = nft_expr_priv(expr);
 365
 366         if (nla_put_be32(skb, NFTA_REJECT_TYPE, htonl(priv->type)))
 367                 goto nla_put_failure;
 368
 369         switch (priv->type) {
 370         case NFT_REJECT_ICMP_UNREACH:
 371         case NFT_REJECT_ICMPX_UNREACH:
 372                 if (nla_put_u8(skb, NFTA_REJECT_ICMP_CODE, priv->icmp_code))
 373                         goto nla_put_failure;
 374                 break;
 375         default:
 376                 break;
 377         }
 378
 379         return 0;
 380
 381 nla_put_failure:
 382         return -1;
 383 }
 384
 385 static struct nft_expr_type nft_reject_bridge_type;
 386 static const struct nft_expr_ops nft_reject_bridge_ops = {
 387         .type           = &nft_reject_bridge_type,
 388         .size           = NFT_EXPR_SIZE(sizeof(struct nft_reject)),
 389         .eval           = nft_reject_bridge_eval,
 390         .init           = nft_reject_bridge_init,
 391         .dump           = nft_reject_bridge_dump,
 392         .validate       = nft_reject_bridge_validate,
 393 };
 394
 395 static struct nft_expr_type nft_reject_bridge_type __read_mostly = {
 396         .family         = NFPROTO_BRIDGE,
 397         .name           = "reject",
 398         .ops            = &nft_reject_bridge_ops,
 399         .policy         = nft_reject_policy,
 400         .maxattr        = NFTA_REJECT_MAX,
 401         .owner          = THIS_MODULE,
 402 };
 403
 404 static int __init nft_reject_bridge_module_init(void)
 405 {
 406         return nft_register_expr(&nft_reject_bridge_type);
 407 }
 408
 409 static void __exit nft_reject_bridge_module_exit(void)
 410 {
 411         nft_unregister_expr(&nft_reject_bridge_type);
 412 }
 413
 414 module_init(nft_reject_bridge_module_init);
 415 module_exit(nft_reject_bridge_module_exit);
 416
 417 MODULE_LICENSE("GPL");
 418 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
 419 MODULE_ALIAS_NFT_AF_EXPR(AF_BRIDGE, "reject");