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