xref: /linux/security/selinux/netnode.c (revision 60e13231561b3a4c5269bfa1ef6c0569ad6f28ec)
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 
49 struct sel_netnode_bkt {
50 	unsigned int size;
51 	struct list_head list;
52 };
53 
54 struct 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 
67 static LIST_HEAD(sel_netnode_list);
68 static DEFINE_SPINLOCK(sel_netnode_lock);
69 static 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  */
80 static 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  */
96 static 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  */
114 static 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  */
156 static 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 	}
170 
171 	/* we need to impose a limit on the growth of the hash table so check
172 	 * this bucket to make sure it is within the specified bounds */
173 	list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
174 	if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
175 		struct sel_netnode *tail;
176 		tail = list_entry(
177 			rcu_dereference(sel_netnode_hash[idx].list.prev),
178 			struct sel_netnode, list);
179 		list_del_rcu(&tail->list);
180 		kfree_rcu(tail, rcu);
181 	} else
182 		sel_netnode_hash[idx].size++;
183 }
184 
185 /**
186  * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
187  * @addr: the IP address
188  * @family: the address family
189  * @sid: node SID
190  *
191  * Description:
192  * This function determines the SID of a network address by quering the
193  * security policy.  The result is added to the network address table to
194  * speedup future queries.  Returns zero on success, negative values on
195  * failure.
196  *
197  */
198 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
199 {
200 	int ret = -ENOMEM;
201 	struct sel_netnode *node;
202 	struct sel_netnode *new = NULL;
203 
204 	spin_lock_bh(&sel_netnode_lock);
205 	node = sel_netnode_find(addr, family);
206 	if (node != NULL) {
207 		*sid = node->nsec.sid;
208 		spin_unlock_bh(&sel_netnode_lock);
209 		return 0;
210 	}
211 	new = kzalloc(sizeof(*new), GFP_ATOMIC);
212 	if (new == NULL)
213 		goto out;
214 	switch (family) {
215 	case PF_INET:
216 		ret = security_node_sid(PF_INET,
217 					addr, sizeof(struct in_addr), sid);
218 		new->nsec.addr.ipv4 = *(__be32 *)addr;
219 		break;
220 	case PF_INET6:
221 		ret = security_node_sid(PF_INET6,
222 					addr, sizeof(struct in6_addr), sid);
223 		ipv6_addr_copy(&new->nsec.addr.ipv6, addr);
224 		break;
225 	default:
226 		BUG();
227 	}
228 	if (ret != 0)
229 		goto out;
230 
231 	new->nsec.family = family;
232 	new->nsec.sid = *sid;
233 	sel_netnode_insert(new);
234 
235 out:
236 	spin_unlock_bh(&sel_netnode_lock);
237 	if (unlikely(ret)) {
238 		printk(KERN_WARNING
239 		       "SELinux: failure in sel_netnode_sid_slow(),"
240 		       " unable to determine network node label\n");
241 		kfree(new);
242 	}
243 	return ret;
244 }
245 
246 /**
247  * sel_netnode_sid - Lookup the SID of a network address
248  * @addr: the IP address
249  * @family: the address family
250  * @sid: node SID
251  *
252  * Description:
253  * This function determines the SID of a network address using the fastest
254  * method possible.  First the address table is queried, but if an entry
255  * can't be found then the policy is queried and the result is added to the
256  * table to speedup future queries.  Returns zero on success, negative values
257  * on failure.
258  *
259  */
260 int sel_netnode_sid(void *addr, u16 family, u32 *sid)
261 {
262 	struct sel_netnode *node;
263 
264 	rcu_read_lock();
265 	node = sel_netnode_find(addr, family);
266 	if (node != NULL) {
267 		*sid = node->nsec.sid;
268 		rcu_read_unlock();
269 		return 0;
270 	}
271 	rcu_read_unlock();
272 
273 	return sel_netnode_sid_slow(addr, family, sid);
274 }
275 
276 /**
277  * sel_netnode_flush - Flush the entire network address table
278  *
279  * Description:
280  * Remove all entries from the network address table.
281  *
282  */
283 static void sel_netnode_flush(void)
284 {
285 	unsigned int idx;
286 	struct sel_netnode *node, *node_tmp;
287 
288 	spin_lock_bh(&sel_netnode_lock);
289 	for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
290 		list_for_each_entry_safe(node, node_tmp,
291 					 &sel_netnode_hash[idx].list, list) {
292 				list_del_rcu(&node->list);
293 				kfree_rcu(node, rcu);
294 		}
295 		sel_netnode_hash[idx].size = 0;
296 	}
297 	spin_unlock_bh(&sel_netnode_lock);
298 }
299 
300 static int sel_netnode_avc_callback(u32 event, u32 ssid, u32 tsid,
301 				    u16 class, u32 perms, u32 *retained)
302 {
303 	if (event == AVC_CALLBACK_RESET) {
304 		sel_netnode_flush();
305 		synchronize_net();
306 	}
307 	return 0;
308 }
309 
310 static __init int sel_netnode_init(void)
311 {
312 	int iter;
313 	int ret;
314 
315 	if (!selinux_enabled)
316 		return 0;
317 
318 	for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
319 		INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
320 		sel_netnode_hash[iter].size = 0;
321 	}
322 
323 	ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET,
324 			       SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0);
325 	if (ret != 0)
326 		panic("avc_add_callback() failed, error %d\n", ret);
327 
328 	return ret;
329 }
330 
331 __initcall(sel_netnode_init);
332