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Linux/security/selinux/netnode.c

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  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                 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  */
200 static 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 
238 out:
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  */
263 int 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  */
286 void 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 
303 static __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 

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