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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 LIST_HEAD(sel_netnode_list);
58 static DEFINE_SPINLOCK(sel_netnode_lock);
59 static 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  */
sel_netnode_hashfn_ipv4(__be32 addr)70 static 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  */
sel_netnode_hashfn_ipv6(const struct in6_addr * addr)86 static 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  */
sel_netnode_find(const void * addr,u16 family)104 static 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(*(__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 == *(__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  */
sel_netnode_insert(struct sel_netnode * node)146 static 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(sel_netnode_hash[idx].list.prev,
169 						  lockdep_is_held(&sel_netnode_lock)),
170 			struct sel_netnode, list);
171 		list_del_rcu(&tail->list);
172 		kfree_rcu(tail, rcu);
173 	} else
174 		sel_netnode_hash[idx].size++;
175 }
176 
177 /**
178  * sel_netnode_sid_slow - Lookup the SID of a network address using the policy
179  * @addr: the IP address
180  * @family: the address family
181  * @sid: node SID
182  *
183  * Description:
184  * This function determines the SID of a network address by querying the
185  * security policy.  The result is added to the network address table to
186  * speedup future queries.  Returns zero on success, negative values on
187  * failure.
188  *
189  */
sel_netnode_sid_slow(void * addr,u16 family,u32 * sid)190 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid)
191 {
192 	int ret;
193 	struct sel_netnode *node;
194 	struct sel_netnode *new;
195 
196 	spin_lock_bh(&sel_netnode_lock);
197 	node = sel_netnode_find(addr, family);
198 	if (node != NULL) {
199 		*sid = node->nsec.sid;
200 		spin_unlock_bh(&sel_netnode_lock);
201 		return 0;
202 	}
203 
204 	new = kzalloc(sizeof(*new), GFP_ATOMIC);
205 	switch (family) {
206 	case PF_INET:
207 		ret = security_node_sid(&selinux_state, PF_INET,
208 					addr, sizeof(struct in_addr), sid);
209 		if (new)
210 			new->nsec.addr.ipv4 = *(__be32 *)addr;
211 		break;
212 	case PF_INET6:
213 		ret = security_node_sid(&selinux_state, PF_INET6,
214 					addr, sizeof(struct in6_addr), sid);
215 		if (new)
216 			new->nsec.addr.ipv6 = *(struct in6_addr *)addr;
217 		break;
218 	default:
219 		BUG();
220 		ret = -EINVAL;
221 	}
222 	if (ret == 0 && new) {
223 		new->nsec.family = family;
224 		new->nsec.sid = *sid;
225 		sel_netnode_insert(new);
226 	} else
227 		kfree(new);
228 
229 	spin_unlock_bh(&sel_netnode_lock);
230 	if (unlikely(ret))
231 		pr_warn("SELinux: failure in %s(), unable to determine network node label\n",
232 			__func__);
233 	return ret;
234 }
235 
236 /**
237  * sel_netnode_sid - Lookup the SID of a network address
238  * @addr: the IP address
239  * @family: the address family
240  * @sid: node SID
241  *
242  * Description:
243  * This function determines the SID of a network address using the fastest
244  * method possible.  First the address table is queried, but if an entry
245  * can't be found then the policy is queried and the result is added to the
246  * table to speedup future queries.  Returns zero on success, negative values
247  * on failure.
248  *
249  */
sel_netnode_sid(void * addr,u16 family,u32 * sid)250 int sel_netnode_sid(void *addr, u16 family, u32 *sid)
251 {
252 	struct sel_netnode *node;
253 
254 	rcu_read_lock();
255 	node = sel_netnode_find(addr, family);
256 	if (node != NULL) {
257 		*sid = node->nsec.sid;
258 		rcu_read_unlock();
259 		return 0;
260 	}
261 	rcu_read_unlock();
262 
263 	return sel_netnode_sid_slow(addr, family, sid);
264 }
265 
266 /**
267  * sel_netnode_flush - Flush the entire network address table
268  *
269  * Description:
270  * Remove all entries from the network address table.
271  *
272  */
sel_netnode_flush(void)273 void sel_netnode_flush(void)
274 {
275 	unsigned int idx;
276 	struct sel_netnode *node, *node_tmp;
277 
278 	spin_lock_bh(&sel_netnode_lock);
279 	for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) {
280 		list_for_each_entry_safe(node, node_tmp,
281 					 &sel_netnode_hash[idx].list, list) {
282 				list_del_rcu(&node->list);
283 				kfree_rcu(node, rcu);
284 		}
285 		sel_netnode_hash[idx].size = 0;
286 	}
287 	spin_unlock_bh(&sel_netnode_lock);
288 }
289 
sel_netnode_init(void)290 static __init int sel_netnode_init(void)
291 {
292 	int iter;
293 
294 	if (!selinux_enabled_boot)
295 		return 0;
296 
297 	for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) {
298 		INIT_LIST_HEAD(&sel_netnode_hash[iter].list);
299 		sel_netnode_hash[iter].size = 0;
300 	}
301 
302 	return 0;
303 }
304 
305 __initcall(sel_netnode_init);
306