net/netfilter/nft_tproxy.c

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #include <linux/module.h>
   3 #include <linux/netfilter/nf_tables.h>
   4 #include <net/netfilter/nf_tables.h>
   5 #include <net/netfilter/nf_tables_core.h>
   6 #include <net/netfilter/nf_tproxy.h>
   7 #include <net/inet_sock.h>
   8 #include <net/tcp.h>
   9 #include <linux/if_ether.h>
  10 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  11 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
  12 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
  13 #endif
  14
  15 struct nft_tproxy {
  16         enum nft_registers      sreg_addr:8;
  17         enum nft_registers      sreg_port:8;
  18         u8                      family;
  19 };
  20
  21 static void nft_tproxy_eval_v4(const struct nft_expr *expr,
  22                                struct nft_regs *regs,
  23                                const struct nft_pktinfo *pkt)
  24 {
  25         const struct nft_tproxy *priv = nft_expr_priv(expr);
  26         struct sk_buff *skb = pkt->skb;
  27         const struct iphdr *iph = ip_hdr(skb);
  28         struct udphdr _hdr, *hp;
  29         __be32 taddr = 0;
  30         __be16 tport = 0;
  31         struct sock *sk;
  32
  33         hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);
  34         if (!hp) {
  35                 regs->verdict.code = NFT_BREAK;
  36                 return;
  37         }
  38
  39         /* check if there's an ongoing connection on the packet addresses, this
  40          * happens if the redirect already happened and the current packet
  41          * belongs to an already established connection
  42          */
  43         sk = nf_tproxy_get_sock_v4(nft_net(pkt), skb, iph->protocol,
  44                                    iph->saddr, iph->daddr,
  45                                    hp->source, hp->dest,
  46                                    skb->dev, NF_TPROXY_LOOKUP_ESTABLISHED);
  47
  48         if (priv->sreg_addr)
  49                 taddr = regs->data[priv->sreg_addr];
  50         taddr = nf_tproxy_laddr4(skb, taddr, iph->daddr);
  51
  52         if (priv->sreg_port)
  53                 tport = regs->data[priv->sreg_port];
  54         if (!tport)
  55                 tport = hp->dest;
  56
  57         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
  58         if (sk && sk->sk_state == TCP_TIME_WAIT) {
  59                 /* reopening a TIME_WAIT connection needs special handling */
  60                 sk = nf_tproxy_handle_time_wait4(nft_net(pkt), skb, taddr, tport, sk);
  61         } else if (!sk) {
  62                 /* no, there's no established connection, check if
  63                  * there's a listener on the redirected addr/port
  64                  */
  65                 sk = nf_tproxy_get_sock_v4(nft_net(pkt), skb, iph->protocol,
  66                                            iph->saddr, taddr,
  67                                            hp->source, tport,
  68                                            skb->dev, NF_TPROXY_LOOKUP_LISTENER);
  69         }
  70
  71         if (sk && nf_tproxy_sk_is_transparent(sk))
  72                 nf_tproxy_assign_sock(skb, sk);
  73         else
  74                 regs->verdict.code = NFT_BREAK;
  75 }
  76
  77 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
  78 static void nft_tproxy_eval_v6(const struct nft_expr *expr,
  79                                struct nft_regs *regs,
  80                                const struct nft_pktinfo *pkt)
  81 {
  82         const struct nft_tproxy *priv = nft_expr_priv(expr);
  83         struct sk_buff *skb = pkt->skb;
  84         const struct ipv6hdr *iph = ipv6_hdr(skb);
  85         struct in6_addr taddr;
  86         int thoff = pkt->xt.thoff;
  87         struct udphdr _hdr, *hp;
  88         __be16 tport = 0;
  89         struct sock *sk;
  90         int l4proto;
  91
  92         memset(&taddr, 0, sizeof(taddr));
  93
  94         if (!pkt->tprot_set) {
  95                 regs->verdict.code = NFT_BREAK;
  96                 return;
  97         }
  98         l4proto = pkt->tprot;
  99
 100         hp = skb_header_pointer(skb, thoff, sizeof(_hdr), &_hdr);
 101         if (hp == NULL) {
 102                 regs->verdict.code = NFT_BREAK;
 103                 return;
 104         }
 105
 106         /* check if there's an ongoing connection on the packet addresses, this
 107          * happens if the redirect already happened and the current packet
 108          * belongs to an already established connection
 109          */
 110         sk = nf_tproxy_get_sock_v6(nft_net(pkt), skb, thoff, l4proto,
 111                                    &iph->saddr, &iph->daddr,
 112                                    hp->source, hp->dest,
 113                                    nft_in(pkt), NF_TPROXY_LOOKUP_ESTABLISHED);
 114
 115         if (priv->sreg_addr)
 116                 memcpy(&taddr, &regs->data[priv->sreg_addr], sizeof(taddr));
 117         taddr = *nf_tproxy_laddr6(skb, &taddr, &iph->daddr);
 118
 119         if (priv->sreg_port)
 120                 tport = regs->data[priv->sreg_port];
 121         if (!tport)
 122                 tport = hp->dest;
 123
 124         /* UDP has no TCP_TIME_WAIT state, so we never enter here */
 125         if (sk && sk->sk_state == TCP_TIME_WAIT) {
 126                 /* reopening a TIME_WAIT connection needs special handling */
 127                 sk = nf_tproxy_handle_time_wait6(skb, l4proto, thoff,
 128                                                  nft_net(pkt),
 129                                                  &taddr,
 130                                                  tport,
 131                                                  sk);
 132         } else if (!sk) {
 133                 /* no there's no established connection, check if
 134                  * there's a listener on the redirected addr/port
 135                  */
 136                 sk = nf_tproxy_get_sock_v6(nft_net(pkt), skb, thoff,
 137                                            l4proto, &iph->saddr, &taddr,
 138                                            hp->source, tport,
 139                                            nft_in(pkt), NF_TPROXY_LOOKUP_LISTENER);
 140         }
 141
 142         /* NOTE: assign_sock consumes our sk reference */
 143         if (sk && nf_tproxy_sk_is_transparent(sk))
 144                 nf_tproxy_assign_sock(skb, sk);
 145         else
 146                 regs->verdict.code = NFT_BREAK;
 147 }
 148 #endif
 149
 150 static void nft_tproxy_eval(const struct nft_expr *expr,
 151                             struct nft_regs *regs,
 152                             const struct nft_pktinfo *pkt)
 153 {
 154         const struct nft_tproxy *priv = nft_expr_priv(expr);
 155
 156         switch (nft_pf(pkt)) {
 157         case NFPROTO_IPV4:
 158                 switch (priv->family) {
 159                 case NFPROTO_IPV4:
 160                 case NFPROTO_UNSPEC:
 161                         nft_tproxy_eval_v4(expr, regs, pkt);
 162                         return;
 163                 }
 164                 break;
 165 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
 166         case NFPROTO_IPV6:
 167                 switch (priv->family) {
 168                 case NFPROTO_IPV6:
 169                 case NFPROTO_UNSPEC:
 170                         nft_tproxy_eval_v6(expr, regs, pkt);
 171                         return;
 172                 }
 173 #endif
 174         }
 175         regs->verdict.code = NFT_BREAK;
 176 }
 177
 178 static const struct nla_policy nft_tproxy_policy[NFTA_TPROXY_MAX + 1] = {
 179         [NFTA_TPROXY_FAMILY]   = { .type = NLA_U32 },
 180         [NFTA_TPROXY_REG_ADDR] = { .type = NLA_U32 },
 181         [NFTA_TPROXY_REG_PORT] = { .type = NLA_U32 },
 182 };
 183
 184 static int nft_tproxy_init(const struct nft_ctx *ctx,
 185                            const struct nft_expr *expr,
 186                            const struct nlattr * const tb[])
 187 {
 188         struct nft_tproxy *priv = nft_expr_priv(expr);
 189         unsigned int alen = 0;
 190         int err;
 191
 192         if (!tb[NFTA_TPROXY_FAMILY] ||
 193             (!tb[NFTA_TPROXY_REG_ADDR] && !tb[NFTA_TPROXY_REG_PORT]))
 194                 return -EINVAL;
 195
 196         priv->family = ntohl(nla_get_be32(tb[NFTA_TPROXY_FAMILY]));
 197
 198         switch (ctx->family) {
 199         case NFPROTO_IPV4:
 200                 if (priv->family != NFPROTO_IPV4)
 201                         return -EINVAL;
 202                 break;
 203 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
 204         case NFPROTO_IPV6:
 205                 if (priv->family != NFPROTO_IPV6)
 206                         return -EINVAL;
 207                 break;
 208 #endif
 209         case NFPROTO_INET:
 210                 break;
 211         default:
 212                 return -EOPNOTSUPP;
 213         }
 214
 215         /* Address is specified but the rule family is not set accordingly */
 216         if (priv->family == NFPROTO_UNSPEC && tb[NFTA_TPROXY_REG_ADDR])
 217                 return -EINVAL;
 218
 219         switch (priv->family) {
 220         case NFPROTO_IPV4:
 221                 alen = FIELD_SIZEOF(union nf_inet_addr, in);
 222                 err = nf_defrag_ipv4_enable(ctx->net);
 223                 if (err)
 224                         return err;
 225                 break;
 226 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
 227         case NFPROTO_IPV6:
 228                 alen = FIELD_SIZEOF(union nf_inet_addr, in6);
 229                 err = nf_defrag_ipv6_enable(ctx->net);
 230                 if (err)
 231                         return err;
 232                 break;
 233 #endif
 234         case NFPROTO_UNSPEC:
 235                 /* No address is specified here */
 236                 err = nf_defrag_ipv4_enable(ctx->net);
 237                 if (err)
 238                         return err;
 239 #if IS_ENABLED(CONFIG_NF_TABLES_IPV6)
 240                 err = nf_defrag_ipv6_enable(ctx->net);
 241                 if (err)
 242                         return err;
 243 #endif
 244                 break;
 245         default:
 246                 return -EOPNOTSUPP;
 247         }
 248
 249         if (tb[NFTA_TPROXY_REG_ADDR]) {
 250                 priv->sreg_addr = nft_parse_register(tb[NFTA_TPROXY_REG_ADDR]);
 251                 err = nft_validate_register_load(priv->sreg_addr, alen);
 252                 if (err < 0)
 253                         return err;
 254         }
 255
 256         if (tb[NFTA_TPROXY_REG_PORT]) {
 257                 priv->sreg_port = nft_parse_register(tb[NFTA_TPROXY_REG_PORT]);
 258                 err = nft_validate_register_load(priv->sreg_port, sizeof(u16));
 259                 if (err < 0)
 260                         return err;
 261         }
 262
 263         return 0;
 264 }
 265
 266 static int nft_tproxy_dump(struct sk_buff *skb,
 267                            const struct nft_expr *expr)
 268 {
 269         const struct nft_tproxy *priv = nft_expr_priv(expr);
 270
 271         if (nla_put_be32(skb, NFTA_TPROXY_FAMILY, htonl(priv->family)))
 272                 return -1;
 273
 274         if (priv->sreg_addr &&
 275             nft_dump_register(skb, NFTA_TPROXY_REG_ADDR, priv->sreg_addr))
 276                 return -1;
 277
 278         if (priv->sreg_port &&
 279             nft_dump_register(skb, NFTA_TPROXY_REG_PORT, priv->sreg_port))
 280                         return -1;
 281
 282         return 0;
 283 }
 284
 285 static struct nft_expr_type nft_tproxy_type;
 286 static const struct nft_expr_ops nft_tproxy_ops = {
 287         .type           = &nft_tproxy_type,
 288         .size           = NFT_EXPR_SIZE(sizeof(struct nft_tproxy)),
 289         .eval           = nft_tproxy_eval,
 290         .init           = nft_tproxy_init,
 291         .dump           = nft_tproxy_dump,
 292 };
 293
 294 static struct nft_expr_type nft_tproxy_type __read_mostly = {
 295         .name           = "tproxy",
 296         .ops            = &nft_tproxy_ops,
 297         .policy         = nft_tproxy_policy,
 298         .maxattr        = NFTA_TPROXY_MAX,
 299         .owner          = THIS_MODULE,
 300 };
 301
 302 static int __init nft_tproxy_module_init(void)
 303 {
 304         return nft_register_expr(&nft_tproxy_type);
 305 }
 306
 307 static void __exit nft_tproxy_module_exit(void)
 308 {
 309         nft_unregister_expr(&nft_tproxy_type);
 310 }
 311
 312 module_init(nft_tproxy_module_init);
 313 module_exit(nft_tproxy_module_exit);
 314
 315 MODULE_LICENSE("GPL");
 316 MODULE_AUTHOR("Máté Eckl");
 317 MODULE_DESCRIPTION("nf_tables tproxy support module");
 318 MODULE_ALIAS_NFT_EXPR("tproxy");