| // 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; |
| |
| /* 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 = nf_ct_pernet(net); |
| |
| 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 = nf_ct_pernet(net); |
| |
| 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); |
| } |