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