1/*
2 * Network node table
3 *
4 * SELinux must keep a mapping of network nodes to labels/SIDs.  This
5 * mapping is maintained as part of the normal policy but a fast cache is
6 * needed to reduce the lookup overhead since most of these queries happen on
7 * a per-packet basis.
8 *
9 * Author: Paul Moore <paul@paul-moore.com>
10 *
11 * This code is heavily based on the "netif" concept originally developed by
12 * James Morris <jmorris@redhat.com>
13 *   (see security/selinux/netif.c for more information)
14 *
15 */
16
17/*
18 * (c) Copyright Hewlett-Packard Development Company, L.P., 2007
19 *
20 * This program is free software: you can redistribute it and/or modify
21 * it under the terms of version 2 of the GNU General Public License as
22 * published by the Free Software Foundation.
23 *
24 * This program is distributed in the hope that it will be useful,
25 * but WITHOUT ANY WARRANTY; without even the implied warranty of
26 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
27 * GNU General Public License for more details.
28 *
29 */
30
31#include <linux/types.h>
32#include <linux/rcupdate.h>
33#include <linux/list.h>
34#include <linux/slab.h>
35#include <linux/spinlock.h>
36#include <linux/in.h>
37#include <linux/in6.h>
38#include <linux/ip.h>
39#include <linux/ipv6.h>
40#include <net/ip.h>
41#include <net/ipv6.h>
42
43#include "netnode.h"
44#include "objsec.h"
45
46#define SEL_NETNODE_HASH_SIZE       256
47#define SEL_NETNODE_HASH_BKT_LIMIT   16
48
49struct sel_netnode_bkt {
50	unsigned int size;
51	struct list_head list;
52};
53
54struct sel_netnode {
55	struct netnode_security_struct nsec;
56
57	struct list_head list;
58	struct rcu_head rcu;
59};
60
61/* NOTE: we are using a combined hash table for both IPv4 and IPv6, the reason
62 * for this is that I suspect most users will not make heavy use of both
63 * address families at the same time so one table will usually end up wasted,
64 * if this becomes a problem we can always add a hash table for each address
65 * family later */
66
67static LIST_HEAD(sel_netnode_list);
68static DEFINE_SPINLOCK(sel_netnode_lock);
69static struct sel_netnode_bkt sel_netnode_hash[SEL_NETNODE_HASH_SIZE];
70
71/**
72 * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table
73 * @addr: IPv4 address
74 *
75 * Description:
76 * This is the IPv4 hashing function for the node interface table, it returns
77 * the bucket number for the given IP address.
78 *
79 */
80static unsigned int sel_netnode_hashfn_ipv4(__be32 addr)
81{
82	/* at some point we should determine if the mismatch in byte order
83	 * affects the hash function dramatically */
84	return (addr & (SEL_NETNODE_HASH_SIZE - 1));
85}
86
87/**
88 * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table
89 * @addr: IPv6 address
90 *
91 * Description:
92 * This is the IPv6 hashing function for the node interface table, it returns
93 * the bucket number for the given IP address.
94 *
95 */
96static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr)
97{
98	/* just hash the least significant 32 bits to keep things fast (they
99	 * are the most likely to be different anyway), we can revisit this
100	 * later if needed */
101	return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1));
102}
103
104/**
105 * sel_netnode_find - Search for a node record
106 * @addr: IP address
107 * @family: address family
108 *
109 * Description:
110 * Search the network node table and return the record matching @addr.  If an
111 * entry can not be found in the table return NULL.
112 *
113 */
114static struct sel_netnode *sel_netnode_find(const void *addr, u16 family)
115{
116	unsigned int idx;
117	struct sel_netnode *node;
118
119	switch (family) {
120	case PF_INET:
121		idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr);
122		break;
123	case PF_INET6:
124		idx = sel_netnode_hashfn_ipv6(addr);
125		break;
126	default:
127		BUG();
128		return NULL;
129	}
130
131	list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list)
132		if (node->nsec.family == family)
133			switch (family) {
134			case PF_INET:
135				if (node->nsec.addr.ipv4 == *(__be32 *)addr)
136					return node;
137				break;
138			case PF_INET6:
139				if (ipv6_addr_equal(&node->nsec.addr.ipv6,
140						    addr))
141					return node;
142				break;
143			}
144
145	return NULL;
146}
147
148/**
149 * sel_netnode_insert - Insert a new node into the table
150 * @node: the new node record
151 *
152 * Description:
153 * Add a new node record to the network address hash table.
154 *
155 */
156static void sel_netnode_insert(struct sel_netnode *node)
157{
158	unsigned int idx;
159
160	switch (node->nsec.family) {
161	case PF_INET:
162		idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4);
163		break;
164	case PF_INET6:
165		idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6);
166		break;
167	default:
168		BUG();
169		return;
170	}
171
172	/* we need to impose a limit on the growth of the hash table so check
173	 * this bucket to make sure it is within the specified bounds */
174	list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
175	if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
176		struct sel_netnode *tail;
177		tail = list_entry(
178			rcu_dereference_protected(sel_netnode_hash[idx].list.prev,
179						  lockdep_is_held(&sel_netnode_lock)),
180			struct sel_netnode, list);
181		list_del_rcu(&tail->list);
182		kfree_rcu(tail, rcu);
183	} else
184		sel_netnode_hash[idx].size++;
185}
186
187/**
188 * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
189 * @addr: the IP address
190 * @family: the address family
191 * @sid: node SID
192 *
193 * Description:
194 * This function determines the SID of a network address by quering the
195 * security policy.  The result is added to the network address table to
196 * speedup future queries.  Returns zero on success, negative values on
197 * failure.
198 *
199 */
200static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
201{
202	int ret = -ENOMEM;
203	struct sel_netnode *node;
204	struct sel_netnode *new = NULL;
205
206	spin_lock_bh(&sel_netnode_lock);
207	node = sel_netnode_find(addr, family);
208	if (node != NULL) {
209		*sid = node->nsec.sid;
210		spin_unlock_bh(&sel_netnode_lock);
211		return 0;
212	}
213	new = kzalloc(sizeof(*new), GFP_ATOMIC);
214	if (new == NULL)
215		goto out;
216	switch (family) {
217	case PF_INET:
218		ret = security_node_sid(PF_INET,
219					addr, sizeof(struct in_addr), sid);
220		new->nsec.addr.ipv4 = *(__be32 *)addr;
221		break;
222	case PF_INET6:
223		ret = security_node_sid(PF_INET6,
224					addr, sizeof(struct in6_addr), sid);
225		new->nsec.addr.ipv6 = *(struct in6_addr *)addr;
226		break;
227	default:
228		BUG();
229		ret = -EINVAL;
230	}
231	if (ret != 0)
232		goto out;
233
234	new->nsec.family = family;
235	new->nsec.sid = *sid;
236	sel_netnode_insert(new);
237
238out:
239	spin_unlock_bh(&sel_netnode_lock);
240	if (unlikely(ret)) {
241		printk(KERN_WARNING
242		       "SELinux: failure in sel_netnode_sid_slow(),"
243		       " unable to determine network node label\n");
244		kfree(new);
245	}
246	return ret;
247}
248
249/**
250 * sel_netnode_sid - Lookup the SID of a network address
251 * @addr: the IP address
252 * @family: the address family
253 * @sid: node SID
254 *
255 * Description:
256 * This function determines the SID of a network address using the fastest
257 * method possible.  First the address table is queried, but if an entry
258 * can't be found then the policy is queried and the result is added to the
259 * table to speedup future queries.  Returns zero on success, negative values
260 * on failure.
261 *
262 */
263int sel_netnode_sid(void *addr, u16 family, u32 *sid)
264{
265	struct sel_netnode *node;
266
267	rcu_read_lock();
268	node = sel_netnode_find(addr, family);
269	if (node != NULL) {
270		*sid = node->nsec.sid;
271		rcu_read_unlock();
272		return 0;
273	}
274	rcu_read_unlock();
275
276	return sel_netnode_sid_slow(addr, family, sid);
277}
278
279/**
280 * sel_netnode_flush - Flush the entire network address table
281 *
282 * Description:
283 * Remove all entries from the network address table.
284 *
285 */
286void sel_netnode_flush(void)
287{
288	unsigned int idx;
289	struct sel_netnode *node, *node_tmp;
290
291	spin_lock_bh(&sel_netnode_lock);
292	for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
293		list_for_each_entry_safe(node, node_tmp,
294					 &sel_netnode_hash[idx].list, list) {
295				list_del_rcu(&node->list);
296				kfree_rcu(node, rcu);
297		}
298		sel_netnode_hash[idx].size = 0;
299	}
300	spin_unlock_bh(&sel_netnode_lock);
301}
302
303static __init int sel_netnode_init(void)
304{
305	int iter;
306
307	if (!selinux_enabled)
308		return 0;
309
310	for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
311		INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
312		sel_netnode_hash[iter].size = 0;
313	}
314
315	return 0;
316}
317
318__initcall(sel_netnode_init);
319