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