netnode.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Network node table
  4 *
  5 * SELinux must keep a mapping of network nodes to labels/SIDs.  This
  6 * mapping is maintained as part of the normal policy but a fast cache is
  7 * needed to reduce the lookup overhead since most of these queries happen on
  8 * a per-packet basis.
  9 *
 10 * Author: Paul Moore <paul@paul-moore.com>
 11 *
 12 * This code is heavily based on the "netif" concept originally developed by
 13 * James Morris <jmorris@redhat.com>
 14 *   (see security/selinux/netif.c for more information)
 15 */
 16
 17/*
 18 * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
 19 */
 20
 21#include <linux/types.h>
 22#include <linux/rcupdate.h>
 23#include <linux/list.h>
 24#include <linux/slab.h>
 25#include <linux/spinlock.h>
 26#include <linux/in.h>
 27#include <linux/in6.h>
 28#include <linux/ip.h>
 29#include <linux/ipv6.h>
 30#include <net/ip.h>
 31#include <net/ipv6.h>
 32
 33#include "initcalls.h"
 34#include "netnode.h"
 35#include "objsec.h"
 36
 37#define SEL_NETNODE_HASH_SIZE       256
 38#define SEL_NETNODE_HASH_BKT_LIMIT   16
 39
 40struct sel_netnode_bkt {
 41	unsigned int size;
 42	struct list_head list;
 43};
 44
 45struct sel_netnode {
 46	struct netnode_security_struct nsec;
 47
 48	struct list_head list;
 49	struct rcu_head rcu;
 50};
 51
 52/* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
 53 * for this is that I suspect most users will not make heavy use of both
 54 * address families at the same time so one table will usually end up wasted,
 55 * if this becomes a problem we can always add a hash table for each address
 56 * family later */
 57
 58static DEFINE_SPINLOCK(sel_netnode_lock);
 59static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];
 60
 61/**
 62 * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
 63 * @addr: IPv4 address
 64 *
 65 * Description:
 66 * This is the IPv4 hashing function for the node interface table, it returns
 67 * the bucket number for the given IP address.
 68 *
 69 */
 70static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
 71{
 72	/* at some point we should determine if the mismatch in byte order
 73	 * affects the hash function dramatically */
 74	return (addr & (SEL_NETNODE_HASH_SIZE - 1));
 75}
 76
 77/**
 78 * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
 79 * @addr: IPv6 address
 80 *
 81 * Description:
 82 * This is the IPv6 hashing function for the node interface table, it returns
 83 * the bucket number for the given IP address.
 84 *
 85 */
 86static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
 87{
 88	/* just hash the least significant 32 bits to keep things fast (they
 89	 * are the most likely to be different anyway), we can revisit this
 90	 * later if needed */
 91	return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
 92}
 93
 94/**
 95 * sel_netnode_find - Search for a node record
 96 * @addr: IP address
 97 * @family: address family
 98 *
 99 * Description:
100 * Search the network node table and return the record matching @addr.  If an
101 * entry can not be found in the table return NULL.
102 *
103 */
104static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
105{
106	unsigned int idx;
107	struct sel_netnode *node;
108
109	switch (family) {
110	case PF_INET:
111		idx = sel_netnode_hashfn_ipv4(*(const __be32 *)addr);
112		break;
113	case PF_INET6:
114		idx = sel_netnode_hashfn_ipv6(addr);
115		break;
116	default:
117		BUG();
118		return NULL;
119	}
120
121	list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
122		if (node->nsec.family == family)
123			switch (family) {
124			case PF_INET:
125				if (node->nsec.addr.ipv4 == *(const __be32 *)addr)
126					return node;
127				break;
128			case PF_INET6:
129				if (ipv6_addr_equal(&node->nsec.addr.ipv6,
130						    addr))
131					return node;
132				break;
133			}
134
135	return NULL;
136}
137
138/**
139 * sel_netnode_insert - Insert a new node into the table
140 * @node: the new node record
141 *
142 * Description:
143 * Add a new node record to the network address hash table.
144 *
145 */
146static void sel_netnode_insert(struct sel_netnode *node)
147{
148	unsigned int idx;
149
150	switch (node->nsec.family) {
151	case PF_INET:
152		idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
153		break;
154	case PF_INET6:
155		idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
156		break;
157	default:
158		BUG();
159		return;
160	}
161
162	/* we need to impose a limit on the growth of the hash table so check
163	 * this bucket to make sure it is within the specified bounds */
164	list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
165	if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
166		struct sel_netnode *tail;
167		tail = list_entry(
168			rcu_dereference_protected(
169				list_tail_rcu(&sel_netnode_hash[idx].list),
170				lockdep_is_held(&sel_netnode_lock)),
171			struct sel_netnode, list);
172		list_del_rcu(&tail->list);
173		kfree_rcu(tail, rcu);
174	} else
175		sel_netnode_hash[idx].size++;
176}
177
178/**
179 * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
180 * @addr: the IP address
181 * @family: the address family
182 * @sid: node SID
183 *
184 * Description:
185 * This function determines the SID of a network address by querying the
186 * security policy.  The result is added to the network address table to
187 * speedup future queries.  Returns zero on success, negative values on
188 * failure.
189 *
190 */
191static int sel_netnode_sid_slow(const void *addr, u16 family, u32 *sid)
192{
193	int ret;
194	struct sel_netnode *node;
195	struct sel_netnode *new;
196
197	spin_lock_bh(&sel_netnode_lock);
198	node = sel_netnode_find(addr, family);
199	if (node != NULL) {
200		*sid = node->nsec.sid;
201		spin_unlock_bh(&sel_netnode_lock);
202		return 0;
203	}
204
205	/* If this memory allocation fails still return 0. The SID
206	 * is valid, it just won't be added to the cache.
207	 */
208	new = kmalloc(sizeof(*new), GFP_ATOMIC);
209	switch (family) {
210	case PF_INET:
211		ret = security_node_sid(PF_INET,
212					addr, sizeof(struct in_addr), sid);
213		if (new)
214			new->nsec.addr.ipv4 = *(const __be32 *)addr;
215		break;
216	case PF_INET6:
217		ret = security_node_sid(PF_INET6,
218					addr, sizeof(struct in6_addr), sid);
219		if (new)
220			new->nsec.addr.ipv6 = *(const struct in6_addr *)addr;
221		break;
222	default:
223		BUG();
224		ret = -EINVAL;
225	}
226	if (ret == 0 && new) {
227		new->nsec.family = family;
228		new->nsec.sid = *sid;
229		sel_netnode_insert(new);
230	} else
231		kfree(new);
232
233	spin_unlock_bh(&sel_netnode_lock);
234	if (unlikely(ret))
235		pr_warn("SELinux: failure in %s(), unable to determine network node label\n",
236			__func__);
237	return ret;
238}
239
240/**
241 * sel_netnode_sid - Lookup the SID of a network address
242 * @addr: the IP address
243 * @family: the address family
244 * @sid: node SID
245 *
246 * Description:
247 * This function determines the SID of a network address using the fastest
248 * method possible.  First the address table is queried, but if an entry
249 * can't be found then the policy is queried and the result is added to the
250 * table to speedup future queries.  Returns zero on success, negative values
251 * on failure.
252 *
253 */
254int sel_netnode_sid(const void *addr, u16 family, u32 *sid)
255{
256	struct sel_netnode *node;
257
258	rcu_read_lock();
259	node = sel_netnode_find(addr, family);
260	if (likely(node != NULL)) {
261		*sid = node->nsec.sid;
262		rcu_read_unlock();
263		return 0;
264	}
265	rcu_read_unlock();
266
267	return sel_netnode_sid_slow(addr, family, sid);
268}
269
270/**
271 * sel_netnode_flush - Flush the entire network address table
272 *
273 * Description:
274 * Remove all entries from the network address table.
275 *
276 */
277void sel_netnode_flush(void)
278{
279	unsigned int idx;
280	struct sel_netnode *node, *node_tmp;
281
282	spin_lock_bh(&sel_netnode_lock);
283	for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
284		list_for_each_entry_safe(node, node_tmp,
285					 &sel_netnode_hash[idx].list, list) {
286				list_del_rcu(&node->list);
287				kfree_rcu(node, rcu);
288		}
289		sel_netnode_hash[idx].size = 0;
290	}
291	spin_unlock_bh(&sel_netnode_lock);
292}
293
294int __init sel_netnode_init(void)
295{
296	int iter;
297
298	if (!selinux_enabled_boot)
299		return 0;
300
301	for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
302		INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
303		sel_netnode_hash[iter].size = 0;
304	}
305
306	return 0;
307}