net/netfilter/nfnetlink_hook.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (c) 2021 Red Hat GmbH
   4  *
   5  * Author: Florian Westphal <fw@strlen.de>
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/kallsyms.h>
  10 #include <linux/kernel.h>
  11 #include <linux/types.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/errno.h>
  14 #include <linux/netlink.h>
  15 #include <linux/slab.h>
  16
  17 #include <linux/netfilter.h>
  18
  19 #include <linux/netfilter/nfnetlink.h>
  20 #include <linux/netfilter/nfnetlink_hook.h>
  21
  22 #include <net/netfilter/nf_tables.h>
  23 #include <net/sock.h>
  24
  25 static const struct nla_policy nfnl_hook_nla_policy[NFNLA_HOOK_MAX + 1] = {
  26         [NFNLA_HOOK_HOOKNUM]    = { .type = NLA_U32 },
  27         [NFNLA_HOOK_PRIORITY]   = { .type = NLA_U32 },
  28         [NFNLA_HOOK_DEV]        = { .type = NLA_STRING,
  29                                     .len = IFNAMSIZ - 1 },
  30         [NFNLA_HOOK_FUNCTION_NAME] = { .type = NLA_NUL_STRING,
  31                                        .len = KSYM_NAME_LEN, },
  32         [NFNLA_HOOK_MODULE_NAME] = { .type = NLA_NUL_STRING,
  33                                      .len = MODULE_NAME_LEN, },
  34         [NFNLA_HOOK_CHAIN_INFO] = { .type = NLA_NESTED, },
  35 };
  36
  37 static int nf_netlink_dump_start_rcu(struct sock *nlsk, struct sk_buff *skb,
  38                                      const struct nlmsghdr *nlh,
  39                                      struct netlink_dump_control *c)
  40 {
  41         int err;
  42
  43         if (!try_module_get(THIS_MODULE))
  44                 return -EINVAL;
  45
  46         rcu_read_unlock();
  47         err = netlink_dump_start(nlsk, skb, nlh, c);
  48         rcu_read_lock();
  49         module_put(THIS_MODULE);
  50
  51         return err;
  52 }
  53
  54 struct nfnl_dump_hook_data {
  55         char devname[IFNAMSIZ];
  56         unsigned long headv;
  57         u8 hook;
  58 };
  59
  60 static int nfnl_hook_put_nft_chain_info(struct sk_buff *nlskb,
  61                                         const struct nfnl_dump_hook_data *ctx,
  62                                         unsigned int seq,
  63                                         const struct nf_hook_ops *ops)
  64 {
  65         struct net *net = sock_net(nlskb->sk);
  66         struct nlattr *nest, *nest2;
  67         struct nft_chain *chain;
  68         int ret = 0;
  69
  70         if (ops->hook_ops_type != NF_HOOK_OP_NF_TABLES)
  71                 return 0;
  72
  73         chain = ops->priv;
  74         if (WARN_ON_ONCE(!chain))
  75                 return 0;
  76
  77         if (!nft_is_active(net, chain))
  78                 return 0;
  79
  80         nest = nla_nest_start(nlskb, NFNLA_HOOK_CHAIN_INFO);
  81         if (!nest)
  82                 return -EMSGSIZE;
  83
  84         ret = nla_put_be32(nlskb, NFNLA_HOOK_INFO_TYPE,
  85                            htonl(NFNL_HOOK_TYPE_NFTABLES));
  86         if (ret)
  87                 goto cancel_nest;
  88
  89         nest2 = nla_nest_start(nlskb, NFNLA_HOOK_INFO_DESC);
  90         if (!nest2)
  91                 goto cancel_nest;
  92
  93         ret = nla_put_string(nlskb, NFNLA_CHAIN_TABLE, chain->table->name);
  94         if (ret)
  95                 goto cancel_nest;
  96
  97         ret = nla_put_string(nlskb, NFNLA_CHAIN_NAME, chain->name);
  98         if (ret)
  99                 goto cancel_nest;
 100
 101         ret = nla_put_u8(nlskb, NFNLA_CHAIN_FAMILY, chain->table->family);
 102         if (ret)
 103                 goto cancel_nest;
 104
 105         nla_nest_end(nlskb, nest2);
 106         nla_nest_end(nlskb, nest);
 107         return ret;
 108
 109 cancel_nest:
 110         nla_nest_cancel(nlskb, nest);
 111         return -EMSGSIZE;
 112 }
 113
 114 static int nfnl_hook_dump_one(struct sk_buff *nlskb,
 115                               const struct nfnl_dump_hook_data *ctx,
 116                               const struct nf_hook_ops *ops,
 117                               int family, unsigned int seq)
 118 {
 119         u16 event = nfnl_msg_type(NFNL_SUBSYS_HOOK, NFNL_MSG_HOOK_GET);
 120         unsigned int portid = NETLINK_CB(nlskb).portid;
 121         struct nlmsghdr *nlh;
 122         int ret = -EMSGSIZE;
 123         u32 hooknum;
 124 #ifdef CONFIG_KALLSYMS
 125         char sym[KSYM_SYMBOL_LEN];
 126         char *module_name;
 127 #endif
 128         nlh = nfnl_msg_put(nlskb, portid, seq, event,
 129                            NLM_F_MULTI, family, NFNETLINK_V0, 0);
 130         if (!nlh)
 131                 goto nla_put_failure;
 132
 133 #ifdef CONFIG_KALLSYMS
 134         ret = snprintf(sym, sizeof(sym), "%ps", ops->hook);
 135         if (ret >= sizeof(sym)) {
 136                 ret = -EINVAL;
 137                 goto nla_put_failure;
 138         }
 139
 140         module_name = strstr(sym, " [");
 141         if (module_name) {
 142                 char *end;
 143
 144                 *module_name = '\0';
 145                 module_name += 2;
 146                 end = strchr(module_name, ']');
 147                 if (end) {
 148                         *end = 0;
 149
 150                         ret = nla_put_string(nlskb, NFNLA_HOOK_MODULE_NAME, module_name);
 151                         if (ret)
 152                                 goto nla_put_failure;
 153                 }
 154         }
 155
 156         ret = nla_put_string(nlskb, NFNLA_HOOK_FUNCTION_NAME, sym);
 157         if (ret)
 158                 goto nla_put_failure;
 159 #endif
 160
 161         if (ops->pf == NFPROTO_INET && ops->hooknum == NF_INET_INGRESS)
 162                 hooknum = NF_NETDEV_INGRESS;
 163         else
 164                 hooknum = ops->hooknum;
 165
 166         ret = nla_put_be32(nlskb, NFNLA_HOOK_HOOKNUM, htonl(hooknum));
 167         if (ret)
 168                 goto nla_put_failure;
 169
 170         ret = nla_put_be32(nlskb, NFNLA_HOOK_PRIORITY, htonl(ops->priority));
 171         if (ret)
 172                 goto nla_put_failure;
 173
 174         ret = nfnl_hook_put_nft_chain_info(nlskb, ctx, seq, ops);
 175         if (ret)
 176                 goto nla_put_failure;
 177
 178         nlmsg_end(nlskb, nlh);
 179         return 0;
 180 nla_put_failure:
 181         nlmsg_trim(nlskb, nlh);
 182         return ret;
 183 }
 184
 185 static const struct nf_hook_entries *
 186 nfnl_hook_entries_head(u8 pf, unsigned int hook, struct net *net, const char *dev)
 187 {
 188         const struct nf_hook_entries *hook_head = NULL;
 189 #if defined(CONFIG_NETFILTER_INGRESS) || defined(CONFIG_NETFILTER_EGRESS)
 190         struct net_device *netdev;
 191 #endif
 192
 193         switch (pf) {
 194         case NFPROTO_IPV4:
 195                 if (hook >= ARRAY_SIZE(net->nf.hooks_ipv4))
 196                         return ERR_PTR(-EINVAL);
 197                 hook_head = rcu_dereference(net->nf.hooks_ipv4[hook]);
 198                 break;
 199         case NFPROTO_IPV6:
 200                 if (hook >= ARRAY_SIZE(net->nf.hooks_ipv6))
 201                         return ERR_PTR(-EINVAL);
 202                 hook_head = rcu_dereference(net->nf.hooks_ipv6[hook]);
 203                 break;
 204         case NFPROTO_ARP:
 205 #ifdef CONFIG_NETFILTER_FAMILY_ARP
 206                 if (hook >= ARRAY_SIZE(net->nf.hooks_arp))
 207                         return ERR_PTR(-EINVAL);
 208                 hook_head = rcu_dereference(net->nf.hooks_arp[hook]);
 209 #endif
 210                 break;
 211         case NFPROTO_BRIDGE:
 212 #ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
 213                 if (hook >= ARRAY_SIZE(net->nf.hooks_bridge))
 214                         return ERR_PTR(-EINVAL);
 215                 hook_head = rcu_dereference(net->nf.hooks_bridge[hook]);
 216 #endif
 217                 break;
 218 #if defined(CONFIG_NETFILTER_INGRESS) || defined(CONFIG_NETFILTER_EGRESS)
 219         case NFPROTO_NETDEV:
 220                 if (hook >= NF_NETDEV_NUMHOOKS)
 221                         return ERR_PTR(-EOPNOTSUPP);
 222
 223                 if (!dev)
 224                         return ERR_PTR(-ENODEV);
 225
 226                 netdev = dev_get_by_name_rcu(net, dev);
 227                 if (!netdev)
 228                         return ERR_PTR(-ENODEV);
 229
 230 #ifdef CONFIG_NETFILTER_INGRESS
 231                 if (hook == NF_NETDEV_INGRESS)
 232                         return rcu_dereference(netdev->nf_hooks_ingress);
 233 #endif
 234 #ifdef CONFIG_NETFILTER_EGRESS
 235                 if (hook == NF_NETDEV_EGRESS)
 236                         return rcu_dereference(netdev->nf_hooks_egress);
 237 #endif
 238                 fallthrough;
 239 #endif
 240         default:
 241                 return ERR_PTR(-EPROTONOSUPPORT);
 242         }
 243
 244         return hook_head;
 245 }
 246
 247 static int nfnl_hook_dump(struct sk_buff *nlskb,
 248                           struct netlink_callback *cb)
 249 {
 250         struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
 251         struct nfnl_dump_hook_data *ctx = cb->data;
 252         int err, family = nfmsg->nfgen_family;
 253         struct net *net = sock_net(nlskb->sk);
 254         struct nf_hook_ops * const *ops;
 255         const struct nf_hook_entries *e;
 256         unsigned int i = cb->args[0];
 257
 258         rcu_read_lock();
 259
 260         e = nfnl_hook_entries_head(family, ctx->hook, net, ctx->devname);
 261         if (!e)
 262                 goto done;
 263
 264         if (IS_ERR(e)) {
 265                 cb->seq++;
 266                 goto done;
 267         }
 268
 269         if ((unsigned long)e != ctx->headv || i >= e->num_hook_entries)
 270                 cb->seq++;
 271
 272         ops = nf_hook_entries_get_hook_ops(e);
 273
 274         for (; i < e->num_hook_entries; i++) {
 275                 err = nfnl_hook_dump_one(nlskb, ctx, ops[i], family,
 276                                          cb->nlh->nlmsg_seq);
 277                 if (err)
 278                         break;
 279         }
 280
 281 done:
 282         nl_dump_check_consistent(cb, nlmsg_hdr(nlskb));
 283         rcu_read_unlock();
 284         cb->args[0] = i;
 285         return nlskb->len;
 286 }
 287
 288 static int nfnl_hook_dump_start(struct netlink_callback *cb)
 289 {
 290         const struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
 291         const struct nlattr * const *nla = cb->data;
 292         struct nfnl_dump_hook_data *ctx = NULL;
 293         struct net *net = sock_net(cb->skb->sk);
 294         u8 family = nfmsg->nfgen_family;
 295         char name[IFNAMSIZ] = "";
 296         const void *head;
 297         u32 hooknum;
 298
 299         hooknum = ntohl(nla_get_be32(nla[NFNLA_HOOK_HOOKNUM]));
 300         if (hooknum > 255)
 301                 return -EINVAL;
 302
 303         if (family == NFPROTO_NETDEV) {
 304                 if (!nla[NFNLA_HOOK_DEV])
 305                         return -EINVAL;
 306
 307                 nla_strscpy(name, nla[NFNLA_HOOK_DEV], sizeof(name));
 308         }
 309
 310         rcu_read_lock();
 311         /* Not dereferenced; for consistency check only */
 312         head = nfnl_hook_entries_head(family, hooknum, net, name);
 313         rcu_read_unlock();
 314
 315         if (head && IS_ERR(head))
 316                 return PTR_ERR(head);
 317
 318         ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 319         if (!ctx)
 320                 return -ENOMEM;
 321
 322         strscpy(ctx->devname, name, sizeof(ctx->devname));
 323         ctx->headv = (unsigned long)head;
 324         ctx->hook = hooknum;
 325
 326         cb->seq = 1;
 327         cb->data = ctx;
 328
 329         return 0;
 330 }
 331
 332 static int nfnl_hook_dump_stop(struct netlink_callback *cb)
 333 {
 334         kfree(cb->data);
 335         return 0;
 336 }
 337
 338 static int nfnl_hook_get(struct sk_buff *skb,
 339                          const struct nfnl_info *info,
 340                          const struct nlattr * const nla[])
 341 {
 342         if (!nla[NFNLA_HOOK_HOOKNUM])
 343                 return -EINVAL;
 344
 345         if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
 346                 struct netlink_dump_control c = {
 347                         .start = nfnl_hook_dump_start,
 348                         .done = nfnl_hook_dump_stop,
 349                         .dump = nfnl_hook_dump,
 350                         .module = THIS_MODULE,
 351                         .data = (void *)nla,
 352                 };
 353
 354                 return nf_netlink_dump_start_rcu(info->sk, skb, info->nlh, &c);
 355         }
 356
 357         return -EOPNOTSUPP;
 358 }
 359
 360 static const struct nfnl_callback nfnl_hook_cb[NFNL_MSG_HOOK_MAX] = {
 361         [NFNL_MSG_HOOK_GET] = {
 362                 .call           = nfnl_hook_get,
 363                 .type           = NFNL_CB_RCU,
 364                 .attr_count     = NFNLA_HOOK_MAX,
 365                 .policy         = nfnl_hook_nla_policy
 366         },
 367 };
 368
 369 static const struct nfnetlink_subsystem nfhook_subsys = {
 370         .name                           = "nfhook",
 371         .subsys_id                      = NFNL_SUBSYS_HOOK,
 372         .cb_count                       = NFNL_MSG_HOOK_MAX,
 373         .cb                             = nfnl_hook_cb,
 374 };
 375
 376 MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_HOOK);
 377
 378 static int __init nfnetlink_hook_init(void)
 379 {
 380         return nfnetlink_subsys_register(&nfhook_subsys);
 381 }
 382
 383 static void __exit nfnetlink_hook_exit(void)
 384 {
 385         nfnetlink_subsys_unregister(&nfhook_subsys);
 386 }
 387
 388 module_init(nfnetlink_hook_init);
 389 module_exit(nfnetlink_hook_exit);
 390
 391 MODULE_LICENSE("GPL");
 392 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
 393 MODULE_DESCRIPTION("nfnetlink_hook: list registered netfilter hooks");