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.moore@hp.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_free - Frees a node entry 73 * @p: the entry's RCU field 74 * 75 * Description: 76 * This function is designed to be used as a callback to the call_rcu() 77 * function so that memory allocated to a hash table node entry can be 78 * released safely. 79 * 80 */ 81 static void sel_netnode_free(struct rcu_head *p) 82 { 83 struct sel_netnode *node = container_of(p, struct sel_netnode, rcu); 84 kfree(node); 85 } 86 87 /** 88 * sel_netnode_hashfn_ipv4 - IPv4 hashing function for the node table 89 * @addr: IPv4 address 90 * 91 * Description: 92 * This is the IPv4 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_ipv4(__be32 addr) 97 { 98 /* at some point we should determine if the mismatch in byte order 99 * affects the hash function dramatically */ 100 return (addr & (SEL_NETNODE_HASH_SIZE - 1)); 101 } 102 103 /** 104 * sel_netnode_hashfn_ipv6 - IPv6 hashing function for the node table 105 * @addr: IPv6 address 106 * 107 * Description: 108 * This is the IPv6 hashing function for the node interface table, it returns 109 * the bucket number for the given IP address. 110 * 111 */ 112 static unsigned int sel_netnode_hashfn_ipv6(const struct in6_addr *addr) 113 { 114 /* just hash the least significant 32 bits to keep things fast (they 115 * are the most likely to be different anyway), we can revisit this 116 * later if needed */ 117 return (addr->s6_addr32[3] & (SEL_NETNODE_HASH_SIZE - 1)); 118 } 119 120 /** 121 * sel_netnode_find - Search for a node record 122 * @addr: IP address 123 * @family: address family 124 * 125 * Description: 126 * Search the network node table and return the record matching @addr. If an 127 * entry can not be found in the table return NULL. 128 * 129 */ 130 static struct sel_netnode *sel_netnode_find(const void *addr, u16 family) 131 { 132 unsigned int idx; 133 struct sel_netnode *node; 134 135 switch (family) { 136 case PF_INET: 137 idx = sel_netnode_hashfn_ipv4(*(__be32 *)addr); 138 break; 139 case PF_INET6: 140 idx = sel_netnode_hashfn_ipv6(addr); 141 break; 142 default: 143 BUG(); 144 return NULL; 145 } 146 147 list_for_each_entry_rcu(node, &sel_netnode_hash[idx].list, list) 148 if (node->nsec.family == family) 149 switch (family) { 150 case PF_INET: 151 if (node->nsec.addr.ipv4 == *(__be32 *)addr) 152 return node; 153 break; 154 case PF_INET6: 155 if (ipv6_addr_equal(&node->nsec.addr.ipv6, 156 addr)) 157 return node; 158 break; 159 } 160 161 return NULL; 162 } 163 164 /** 165 * sel_netnode_insert - Insert a new node into the table 166 * @node: the new node record 167 * 168 * Description: 169 * Add a new node record to the network address hash table. 170 * 171 */ 172 static void sel_netnode_insert(struct sel_netnode *node) 173 { 174 unsigned int idx; 175 176 switch (node->nsec.family) { 177 case PF_INET: 178 idx = sel_netnode_hashfn_ipv4(node->nsec.addr.ipv4); 179 break; 180 case PF_INET6: 181 idx = sel_netnode_hashfn_ipv6(&node->nsec.addr.ipv6); 182 break; 183 default: 184 BUG(); 185 } 186 187 /* we need to impose a limit on the growth of the hash table so check 188 * this bucket to make sure it is within the specified bounds */ 189 list_add_rcu(&node->list, &sel_netnode_hash[idx].list); 190 if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) { 191 struct sel_netnode *tail; 192 tail = list_entry( 193 rcu_dereference(sel_netnode_hash[idx].list.prev), 194 struct sel_netnode, list); 195 list_del_rcu(&tail->list); 196 call_rcu(&tail->rcu, sel_netnode_free); 197 } else 198 sel_netnode_hash[idx].size++; 199 } 200 201 /** 202 * sel_netnode_sid_slow - Lookup the SID of a network address using the policy 203 * @addr: the IP address 204 * @family: the address family 205 * @sid: node SID 206 * 207 * Description: 208 * This function determines the SID of a network address by quering the 209 * security policy. The result is added to the network address table to 210 * speedup future queries. Returns zero on success, negative values on 211 * failure. 212 * 213 */ 214 static int sel_netnode_sid_slow(void *addr, u16 family, u32 *sid) 215 { 216 int ret = -ENOMEM; 217 struct sel_netnode *node; 218 struct sel_netnode *new = NULL; 219 220 spin_lock_bh(&sel_netnode_lock); 221 node = sel_netnode_find(addr, family); 222 if (node != NULL) { 223 *sid = node->nsec.sid; 224 spin_unlock_bh(&sel_netnode_lock); 225 return 0; 226 } 227 new = kzalloc(sizeof(*new), GFP_ATOMIC); 228 if (new == NULL) 229 goto out; 230 switch (family) { 231 case PF_INET: 232 ret = security_node_sid(PF_INET, 233 addr, sizeof(struct in_addr), sid); 234 new->nsec.addr.ipv4 = *(__be32 *)addr; 235 break; 236 case PF_INET6: 237 ret = security_node_sid(PF_INET6, 238 addr, sizeof(struct in6_addr), sid); 239 ipv6_addr_copy(&new->nsec.addr.ipv6, addr); 240 break; 241 default: 242 BUG(); 243 } 244 if (ret != 0) 245 goto out; 246 247 new->nsec.family = family; 248 new->nsec.sid = *sid; 249 sel_netnode_insert(new); 250 251 out: 252 spin_unlock_bh(&sel_netnode_lock); 253 if (unlikely(ret)) { 254 printk(KERN_WARNING 255 "SELinux: failure in sel_netnode_sid_slow()," 256 " unable to determine network node label\n"); 257 kfree(new); 258 } 259 return ret; 260 } 261 262 /** 263 * sel_netnode_sid - Lookup the SID of a network address 264 * @addr: the IP address 265 * @family: the address family 266 * @sid: node SID 267 * 268 * Description: 269 * This function determines the SID of a network address using the fastest 270 * method possible. First the address table is queried, but if an entry 271 * can't be found then the policy is queried and the result is added to the 272 * table to speedup future queries. Returns zero on success, negative values 273 * on failure. 274 * 275 */ 276 int sel_netnode_sid(void *addr, u16 family, u32 *sid) 277 { 278 struct sel_netnode *node; 279 280 rcu_read_lock(); 281 node = sel_netnode_find(addr, family); 282 if (node != NULL) { 283 *sid = node->nsec.sid; 284 rcu_read_unlock(); 285 return 0; 286 } 287 rcu_read_unlock(); 288 289 return sel_netnode_sid_slow(addr, family, sid); 290 } 291 292 /** 293 * sel_netnode_flush - Flush the entire network address table 294 * 295 * Description: 296 * Remove all entries from the network address table. 297 * 298 */ 299 static void sel_netnode_flush(void) 300 { 301 unsigned int idx; 302 struct sel_netnode *node, *node_tmp; 303 304 spin_lock_bh(&sel_netnode_lock); 305 for (idx = 0; idx < SEL_NETNODE_HASH_SIZE; idx++) { 306 list_for_each_entry_safe(node, node_tmp, 307 &sel_netnode_hash[idx].list, list) { 308 list_del_rcu(&node->list); 309 call_rcu(&node->rcu, sel_netnode_free); 310 } 311 sel_netnode_hash[idx].size = 0; 312 } 313 spin_unlock_bh(&sel_netnode_lock); 314 } 315 316 static int sel_netnode_avc_callback(u32 event, u32 ssid, u32 tsid, 317 u16 class, u32 perms, u32 *retained) 318 { 319 if (event == AVC_CALLBACK_RESET) { 320 sel_netnode_flush(); 321 synchronize_net(); 322 } 323 return 0; 324 } 325 326 static __init int sel_netnode_init(void) 327 { 328 int iter; 329 int ret; 330 331 if (!selinux_enabled) 332 return 0; 333 334 for (iter = 0; iter < SEL_NETNODE_HASH_SIZE; iter++) { 335 INIT_LIST_HEAD(&sel_netnode_hash[iter].list); 336 sel_netnode_hash[iter].size = 0; 337 } 338 339 ret = avc_add_callback(sel_netnode_avc_callback, AVC_CALLBACK_RESET, 340 SECSID_NULL, SECSID_NULL, SECCLASS_NULL, 0); 341 if (ret != 0) 342 panic("avc_add_callback() failed, error %d\n", ret); 343 344 return ret; 345 } 346 347 __initcall(sel_netnode_init); 348