// SPDX-License-Identifier: GPL-2.0-only
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/* Helper handling for netfilter. */
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/* (C) 1999-2001 Paul `Rusty' Russell
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* (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
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* (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
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* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
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*/
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#include <linux/types.h>
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#include <linux/netfilter.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/vmalloc.h>
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#include <linux/stddef.h>
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#include <linux/random.h>
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#include <linux/err.h>
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#include <linux/kernel.h>
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#include <linux/netdevice.h>
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#include <linux/rculist.h>
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#include <linux/rtnetlink.h>
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#include <net/netfilter/nf_conntrack.h>
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#include <net/netfilter/nf_conntrack_core.h>
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#include <net/netfilter/nf_conntrack_ecache.h>
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#include <net/netfilter/nf_conntrack_extend.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_conntrack_l4proto.h>
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#include <net/netfilter/nf_log.h>
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static DEFINE_MUTEX(nf_ct_helper_mutex);
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struct hlist_head *nf_ct_helper_hash __read_mostly;
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EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
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unsigned int nf_ct_helper_hsize __read_mostly;
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EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
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static unsigned int nf_ct_helper_count __read_mostly;
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static bool nf_ct_auto_assign_helper __read_mostly = false;
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module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
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MODULE_PARM_DESC(nf_conntrack_helper,
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"Enable automatic conntrack helper assignment (default 0)");
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static DEFINE_MUTEX(nf_ct_nat_helpers_mutex);
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static struct list_head nf_ct_nat_helpers __read_mostly;
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/* Stupid hash, but collision free for the default registrations of the
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* helpers currently in the kernel. */
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static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
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{
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return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
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(__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
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}
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static struct nf_conntrack_helper *
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__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
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{
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struct nf_conntrack_helper *helper;
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struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
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unsigned int h;
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if (!nf_ct_helper_count)
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return NULL;
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h = helper_hash(tuple);
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hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) {
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if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
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return helper;
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}
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return NULL;
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}
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struct nf_conntrack_helper *
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__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
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{
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struct nf_conntrack_helper *h;
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unsigned int i;
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for (i = 0; i < nf_ct_helper_hsize; i++) {
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hlist_for_each_entry_rcu(h, &nf_ct_helper_hash[i], hnode) {
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if (strcmp(h->name, name))
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continue;
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if (h->tuple.src.l3num != NFPROTO_UNSPEC &&
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h->tuple.src.l3num != l3num)
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continue;
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if (h->tuple.dst.protonum == protonum)
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return h;
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}
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}
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return NULL;
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}
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EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
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struct nf_conntrack_helper *
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nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
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{
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struct nf_conntrack_helper *h;
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rcu_read_lock();
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h = __nf_conntrack_helper_find(name, l3num, protonum);
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#ifdef CONFIG_MODULES
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if (h == NULL) {
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rcu_read_unlock();
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if (request_module("nfct-helper-%s", name) == 0) {
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rcu_read_lock();
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h = __nf_conntrack_helper_find(name, l3num, protonum);
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} else {
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return h;
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}
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}
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#endif
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if (h != NULL && !try_module_get(h->me))
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h = NULL;
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if (h != NULL && !refcount_inc_not_zero(&h->refcnt)) {
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module_put(h->me);
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h = NULL;
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}
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rcu_read_unlock();
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return h;
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}
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EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
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void nf_conntrack_helper_put(struct nf_conntrack_helper *helper)
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{
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refcount_dec(&helper->refcnt);
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module_put(helper->me);
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}
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EXPORT_SYMBOL_GPL(nf_conntrack_helper_put);
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static struct nf_conntrack_nat_helper *
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nf_conntrack_nat_helper_find(const char *mod_name)
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{
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struct nf_conntrack_nat_helper *cur;
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bool found = false;
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list_for_each_entry_rcu(cur, &nf_ct_nat_helpers, list) {
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if (!strcmp(cur->mod_name, mod_name)) {
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found = true;
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break;
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}
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}
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return found ? cur : NULL;
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}
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int
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nf_nat_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
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{
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struct nf_conntrack_helper *h;
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struct nf_conntrack_nat_helper *nat;
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char mod_name[NF_CT_HELPER_NAME_LEN];
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int ret = 0;
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rcu_read_lock();
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h = __nf_conntrack_helper_find(name, l3num, protonum);
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if (!h) {
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rcu_read_unlock();
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return -ENOENT;
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}
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nat = nf_conntrack_nat_helper_find(h->nat_mod_name);
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if (!nat) {
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snprintf(mod_name, sizeof(mod_name), "%s", h->nat_mod_name);
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rcu_read_unlock();
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request_module(mod_name);
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rcu_read_lock();
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nat = nf_conntrack_nat_helper_find(mod_name);
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if (!nat) {
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rcu_read_unlock();
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return -ENOENT;
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}
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}
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if (!try_module_get(nat->module))
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ret = -ENOENT;
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rcu_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(nf_nat_helper_try_module_get);
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void nf_nat_helper_put(struct nf_conntrack_helper *helper)
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{
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struct nf_conntrack_nat_helper *nat;
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nat = nf_conntrack_nat_helper_find(helper->nat_mod_name);
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if (WARN_ON_ONCE(!nat))
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return;
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module_put(nat->module);
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}
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EXPORT_SYMBOL_GPL(nf_nat_helper_put);
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struct nf_conn_help *
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nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
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{
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struct nf_conn_help *help;
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help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
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if (help)
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INIT_HLIST_HEAD(&help->expectations);
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else
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pr_debug("failed to add helper extension area");
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return help;
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}
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EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
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static struct nf_conntrack_helper *
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nf_ct_lookup_helper(struct nf_conn *ct, struct net *net)
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{
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if (!net->ct.sysctl_auto_assign_helper) {
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if (net->ct.auto_assign_helper_warned)
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return NULL;
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if (!__nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple))
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return NULL;
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pr_info("nf_conntrack: default automatic helper assignment "
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"has been turned off for security reasons and CT-based "
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" firewall rule not found. Use the iptables CT target "
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"to attach helpers instead.\n");
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net->ct.auto_assign_helper_warned = 1;
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return NULL;
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}
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return __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
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}
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int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
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gfp_t flags)
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{
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struct nf_conntrack_helper *helper = NULL;
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struct nf_conn_help *help;
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struct net *net = nf_ct_net(ct);
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/* We already got a helper explicitly attached. The function
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* nf_conntrack_alter_reply - in case NAT is in use - asks for looking
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* the helper up again. Since now the user is in full control of
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* making consistent helper configurations, skip this automatic
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* re-lookup, otherwise we'll lose the helper.
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*/
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if (test_bit(IPS_HELPER_BIT, &ct->status))
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return 0;
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if (tmpl != NULL) {
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help = nfct_help(tmpl);
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if (help != NULL) {
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helper = help->helper;
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set_bit(IPS_HELPER_BIT, &ct->status);
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}
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}
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help = nfct_help(ct);
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if (helper == NULL) {
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helper = nf_ct_lookup_helper(ct, net);
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if (helper == NULL) {
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if (help)
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RCU_INIT_POINTER(help->helper, NULL);
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return 0;
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}
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}
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if (help == NULL) {
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help = nf_ct_helper_ext_add(ct, flags);
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if (help == NULL)
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return -ENOMEM;
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} else {
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/* We only allow helper re-assignment of the same sort since
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* we cannot reallocate the helper extension area.
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*/
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struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
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if (tmp && tmp->help != helper->help) {
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RCU_INIT_POINTER(help->helper, NULL);
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return 0;
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}
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}
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rcu_assign_pointer(help->helper, helper);
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return 0;
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}
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EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
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/* appropriate ct lock protecting must be taken by caller */
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static int unhelp(struct nf_conn *ct, void *me)
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{
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struct nf_conn_help *help = nfct_help(ct);
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if (help && rcu_dereference_raw(help->helper) == me) {
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nf_conntrack_event(IPCT_HELPER, ct);
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RCU_INIT_POINTER(help->helper, NULL);
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}
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/* We are not intended to delete this conntrack. */
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return 0;
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}
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void nf_ct_helper_destroy(struct nf_conn *ct)
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{
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struct nf_conn_help *help = nfct_help(ct);
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struct nf_conntrack_helper *helper;
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if (help) {
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rcu_read_lock();
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helper = rcu_dereference(help->helper);
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if (helper && helper->destroy)
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helper->destroy(ct);
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rcu_read_unlock();
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}
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}
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static LIST_HEAD(nf_ct_helper_expectfn_list);
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void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
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{
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spin_lock_bh(&nf_conntrack_expect_lock);
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list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
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spin_unlock_bh(&nf_conntrack_expect_lock);
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}
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EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
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void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
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{
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spin_lock_bh(&nf_conntrack_expect_lock);
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list_del_rcu(&n->head);
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spin_unlock_bh(&nf_conntrack_expect_lock);
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}
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EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
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/* Caller should hold the rcu lock */
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struct nf_ct_helper_expectfn *
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nf_ct_helper_expectfn_find_by_name(const char *name)
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{
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struct nf_ct_helper_expectfn *cur;
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bool found = false;
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list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
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if (!strcmp(cur->name, name)) {
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found = true;
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break;
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}
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}
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return found ? cur : NULL;
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}
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EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
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/* Caller should hold the rcu lock */
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struct nf_ct_helper_expectfn *
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nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
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{
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struct nf_ct_helper_expectfn *cur;
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bool found = false;
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list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
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if (cur->expectfn == symbol) {
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found = true;
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break;
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}
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}
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return found ? cur : NULL;
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}
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EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
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__printf(3, 4)
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void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
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const char *fmt, ...)
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{
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const struct nf_conn_help *help;
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const struct nf_conntrack_helper *helper;
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struct va_format vaf;
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va_list args;
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va_start(args, fmt);
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vaf.fmt = fmt;
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vaf.va = &args;
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/* Called from the helper function, this call never fails */
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help = nfct_help(ct);
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/* rcu_read_lock()ed by nf_hook_thresh */
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helper = rcu_dereference(help->helper);
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nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
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"nf_ct_%s: dropping packet: %pV ", helper->name, &vaf);
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va_end(args);
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}
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EXPORT_SYMBOL_GPL(nf_ct_helper_log);
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int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
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{
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struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
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unsigned int h = helper_hash(&me->tuple);
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struct nf_conntrack_helper *cur;
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int ret = 0, i;
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BUG_ON(me->expect_policy == NULL);
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BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
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BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
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if (me->expect_policy->max_expected > NF_CT_EXPECT_MAX_CNT)
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return -EINVAL;
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mutex_lock(&nf_ct_helper_mutex);
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for (i = 0; i < nf_ct_helper_hsize; i++) {
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hlist_for_each_entry(cur, &nf_ct_helper_hash[i], hnode) {
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if (!strcmp(cur->name, me->name) &&
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(cur->tuple.src.l3num == NFPROTO_UNSPEC ||
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cur->tuple.src.l3num == me->tuple.src.l3num) &&
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cur->tuple.dst.protonum == me->tuple.dst.protonum) {
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ret = -EEXIST;
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goto out;
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}
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}
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}
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/* avoid unpredictable behaviour for auto_assign_helper */
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if (!(me->flags & NF_CT_HELPER_F_USERSPACE)) {
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hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) {
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if (nf_ct_tuple_src_mask_cmp(&cur->tuple, &me->tuple,
|
&mask)) {
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ret = -EEXIST;
|
goto out;
|
}
|
}
|
}
|
refcount_set(&me->refcnt, 1);
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hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
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nf_ct_helper_count++;
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out:
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mutex_unlock(&nf_ct_helper_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
|
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static bool expect_iter_me(struct nf_conntrack_expect *exp, void *data)
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{
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struct nf_conn_help *help = nfct_help(exp->master);
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const struct nf_conntrack_helper *me = data;
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const struct nf_conntrack_helper *this;
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if (exp->helper == me)
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return true;
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this = rcu_dereference_protected(help->helper,
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lockdep_is_held(&nf_conntrack_expect_lock));
|
return this == me;
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}
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void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
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{
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mutex_lock(&nf_ct_helper_mutex);
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hlist_del_rcu(&me->hnode);
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nf_ct_helper_count--;
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mutex_unlock(&nf_ct_helper_mutex);
|
|
/* Make sure every nothing is still using the helper unless its a
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* connection in the hash.
|
*/
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synchronize_rcu();
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nf_ct_expect_iterate_destroy(expect_iter_me, NULL);
|
nf_ct_iterate_destroy(unhelp, me);
|
|
/* Maybe someone has gotten the helper already when unhelp above.
|
* So need to wait it.
|
*/
|
synchronize_rcu();
|
}
|
EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
|
|
void nf_ct_helper_init(struct nf_conntrack_helper *helper,
|
u16 l3num, u16 protonum, const char *name,
|
u16 default_port, u16 spec_port, u32 id,
|
const struct nf_conntrack_expect_policy *exp_pol,
|
u32 expect_class_max,
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int (*help)(struct sk_buff *skb, unsigned int protoff,
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struct nf_conn *ct,
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enum ip_conntrack_info ctinfo),
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int (*from_nlattr)(struct nlattr *attr,
|
struct nf_conn *ct),
|
struct module *module)
|
{
|
helper->tuple.src.l3num = l3num;
|
helper->tuple.dst.protonum = protonum;
|
helper->tuple.src.u.all = htons(spec_port);
|
helper->expect_policy = exp_pol;
|
helper->expect_class_max = expect_class_max;
|
helper->help = help;
|
helper->from_nlattr = from_nlattr;
|
helper->me = module;
|
snprintf(helper->nat_mod_name, sizeof(helper->nat_mod_name),
|
NF_NAT_HELPER_PREFIX "%s", name);
|
|
if (spec_port == default_port)
|
snprintf(helper->name, sizeof(helper->name), "%s", name);
|
else
|
snprintf(helper->name, sizeof(helper->name), "%s-%u", name, id);
|
}
|
EXPORT_SYMBOL_GPL(nf_ct_helper_init);
|
|
int nf_conntrack_helpers_register(struct nf_conntrack_helper *helper,
|
unsigned int n)
|
{
|
unsigned int i;
|
int err = 0;
|
|
for (i = 0; i < n; i++) {
|
err = nf_conntrack_helper_register(&helper[i]);
|
if (err < 0)
|
goto err;
|
}
|
|
return err;
|
err:
|
if (i > 0)
|
nf_conntrack_helpers_unregister(helper, i);
|
return err;
|
}
|
EXPORT_SYMBOL_GPL(nf_conntrack_helpers_register);
|
|
void nf_conntrack_helpers_unregister(struct nf_conntrack_helper *helper,
|
unsigned int n)
|
{
|
while (n-- > 0)
|
nf_conntrack_helper_unregister(&helper[n]);
|
}
|
EXPORT_SYMBOL_GPL(nf_conntrack_helpers_unregister);
|
|
void nf_nat_helper_register(struct nf_conntrack_nat_helper *nat)
|
{
|
mutex_lock(&nf_ct_nat_helpers_mutex);
|
list_add_rcu(&nat->list, &nf_ct_nat_helpers);
|
mutex_unlock(&nf_ct_nat_helpers_mutex);
|
}
|
EXPORT_SYMBOL_GPL(nf_nat_helper_register);
|
|
void nf_nat_helper_unregister(struct nf_conntrack_nat_helper *nat)
|
{
|
mutex_lock(&nf_ct_nat_helpers_mutex);
|
list_del_rcu(&nat->list);
|
mutex_unlock(&nf_ct_nat_helpers_mutex);
|
}
|
EXPORT_SYMBOL_GPL(nf_nat_helper_unregister);
|
|
static const struct nf_ct_ext_type helper_extend = {
|
.len = sizeof(struct nf_conn_help),
|
.align = __alignof__(struct nf_conn_help),
|
.id = NF_CT_EXT_HELPER,
|
};
|
|
void nf_conntrack_helper_pernet_init(struct net *net)
|
{
|
net->ct.auto_assign_helper_warned = false;
|
net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
|
}
|
|
int nf_conntrack_helper_init(void)
|
{
|
int ret;
|
nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
|
nf_ct_helper_hash =
|
nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
|
if (!nf_ct_helper_hash)
|
return -ENOMEM;
|
|
ret = nf_ct_extend_register(&helper_extend);
|
if (ret < 0) {
|
pr_err("nf_ct_helper: Unable to register helper extension.\n");
|
goto out_extend;
|
}
|
|
INIT_LIST_HEAD(&nf_ct_nat_helpers);
|
return 0;
|
out_extend:
|
kvfree(nf_ct_helper_hash);
|
return ret;
|
}
|
|
void nf_conntrack_helper_fini(void)
|
{
|
nf_ct_extend_unregister(&helper_extend);
|
kvfree(nf_ct_helper_hash);
|
}
|
