| 1 | /* auditfilter.c -- filtering of audit events |
| 2 | * |
| 3 | * Copyright 2003-2004 Red Hat, Inc. |
| 4 | * Copyright 2005 Hewlett-Packard Development Company, L.P. |
| 5 | * Copyright 2005 IBM Corporation |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License as published by |
| 9 | * the Free Software Foundation; either version 2 of the License, or |
| 10 | * (at your option) any later version. |
| 11 | * |
| 12 | * This program is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | * GNU General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License |
| 18 | * along with this program; if not, write to the Free Software |
| 19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 20 | */ |
| 21 | |
| 22 | #include <linux/kernel.h> |
| 23 | #include <linux/audit.h> |
| 24 | #include <linux/kthread.h> |
| 25 | #include <linux/netlink.h> |
| 26 | #include "audit.h" |
| 27 | |
| 28 | /* There are three lists of rules -- one to search at task creation |
| 29 | * time, one to search at syscall entry time, and another to search at |
| 30 | * syscall exit time. */ |
| 31 | struct list_head audit_filter_list[AUDIT_NR_FILTERS] = { |
| 32 | LIST_HEAD_INIT(audit_filter_list[0]), |
| 33 | LIST_HEAD_INIT(audit_filter_list[1]), |
| 34 | LIST_HEAD_INIT(audit_filter_list[2]), |
| 35 | LIST_HEAD_INIT(audit_filter_list[3]), |
| 36 | LIST_HEAD_INIT(audit_filter_list[4]), |
| 37 | LIST_HEAD_INIT(audit_filter_list[5]), |
| 38 | #if AUDIT_NR_FILTERS != 6 |
| 39 | #error Fix audit_filter_list initialiser |
| 40 | #endif |
| 41 | }; |
| 42 | |
| 43 | /* Copy rule from user-space to kernel-space. Called from |
| 44 | * audit_add_rule during AUDIT_ADD. */ |
| 45 | static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule *s) |
| 46 | { |
| 47 | int i; |
| 48 | |
| 49 | if (s->action != AUDIT_NEVER |
| 50 | && s->action != AUDIT_POSSIBLE |
| 51 | && s->action != AUDIT_ALWAYS) |
| 52 | return -1; |
| 53 | if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS) |
| 54 | return -1; |
| 55 | if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS) |
| 56 | return -1; |
| 57 | |
| 58 | d->flags = s->flags; |
| 59 | d->action = s->action; |
| 60 | d->field_count = s->field_count; |
| 61 | for (i = 0; i < d->field_count; i++) { |
| 62 | d->fields[i] = s->fields[i]; |
| 63 | d->values[i] = s->values[i]; |
| 64 | } |
| 65 | for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i]; |
| 66 | return 0; |
| 67 | } |
| 68 | |
| 69 | /* Check to see if two rules are identical. It is called from |
| 70 | * audit_add_rule during AUDIT_ADD and |
| 71 | * audit_del_rule during AUDIT_DEL. */ |
| 72 | static inline int audit_compare_rule(struct audit_rule *a, struct audit_rule *b) |
| 73 | { |
| 74 | int i; |
| 75 | |
| 76 | if (a->flags != b->flags) |
| 77 | return 1; |
| 78 | |
| 79 | if (a->action != b->action) |
| 80 | return 1; |
| 81 | |
| 82 | if (a->field_count != b->field_count) |
| 83 | return 1; |
| 84 | |
| 85 | for (i = 0; i < a->field_count; i++) { |
| 86 | if (a->fields[i] != b->fields[i] |
| 87 | || a->values[i] != b->values[i]) |
| 88 | return 1; |
| 89 | } |
| 90 | |
| 91 | for (i = 0; i < AUDIT_BITMASK_SIZE; i++) |
| 92 | if (a->mask[i] != b->mask[i]) |
| 93 | return 1; |
| 94 | |
| 95 | return 0; |
| 96 | } |
| 97 | |
| 98 | /* Note that audit_add_rule and audit_del_rule are called via |
| 99 | * audit_receive() in audit.c, and are protected by |
| 100 | * audit_netlink_sem. */ |
| 101 | static inline int audit_add_rule(struct audit_rule *rule, |
| 102 | struct list_head *list) |
| 103 | { |
| 104 | struct audit_entry *entry; |
| 105 | int i; |
| 106 | |
| 107 | /* Do not use the _rcu iterator here, since this is the only |
| 108 | * addition routine. */ |
| 109 | list_for_each_entry(entry, list, list) { |
| 110 | if (!audit_compare_rule(rule, &entry->rule)) { |
| 111 | return -EEXIST; |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | for (i = 0; i < rule->field_count; i++) { |
| 116 | if (rule->fields[i] & AUDIT_UNUSED_BITS) |
| 117 | return -EINVAL; |
| 118 | if ( rule->fields[i] & AUDIT_NEGATE ) |
| 119 | rule->fields[i] |= AUDIT_NOT_EQUAL; |
| 120 | else if ( (rule->fields[i] & AUDIT_OPERATORS) == 0 ) |
| 121 | rule->fields[i] |= AUDIT_EQUAL; |
| 122 | rule->fields[i] &= (~AUDIT_NEGATE); |
| 123 | } |
| 124 | |
| 125 | if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL))) |
| 126 | return -ENOMEM; |
| 127 | if (audit_copy_rule(&entry->rule, rule)) { |
| 128 | kfree(entry); |
| 129 | return -EINVAL; |
| 130 | } |
| 131 | |
| 132 | if (entry->rule.flags & AUDIT_FILTER_PREPEND) { |
| 133 | entry->rule.flags &= ~AUDIT_FILTER_PREPEND; |
| 134 | list_add_rcu(&entry->list, list); |
| 135 | } else { |
| 136 | list_add_tail_rcu(&entry->list, list); |
| 137 | } |
| 138 | |
| 139 | return 0; |
| 140 | } |
| 141 | |
| 142 | static inline void audit_free_rule(struct rcu_head *head) |
| 143 | { |
| 144 | struct audit_entry *e = container_of(head, struct audit_entry, rcu); |
| 145 | kfree(e); |
| 146 | } |
| 147 | |
| 148 | /* Note that audit_add_rule and audit_del_rule are called via |
| 149 | * audit_receive() in audit.c, and are protected by |
| 150 | * audit_netlink_sem. */ |
| 151 | static inline int audit_del_rule(struct audit_rule *rule, |
| 152 | struct list_head *list) |
| 153 | { |
| 154 | struct audit_entry *e; |
| 155 | |
| 156 | /* Do not use the _rcu iterator here, since this is the only |
| 157 | * deletion routine. */ |
| 158 | list_for_each_entry(e, list, list) { |
| 159 | if (!audit_compare_rule(rule, &e->rule)) { |
| 160 | list_del_rcu(&e->list); |
| 161 | call_rcu(&e->rcu, audit_free_rule); |
| 162 | return 0; |
| 163 | } |
| 164 | } |
| 165 | return -ENOENT; /* No matching rule */ |
| 166 | } |
| 167 | |
| 168 | static int audit_list_rules(void *_dest) |
| 169 | { |
| 170 | int pid, seq; |
| 171 | int *dest = _dest; |
| 172 | struct audit_entry *entry; |
| 173 | int i; |
| 174 | |
| 175 | pid = dest[0]; |
| 176 | seq = dest[1]; |
| 177 | kfree(dest); |
| 178 | |
| 179 | down(&audit_netlink_sem); |
| 180 | |
| 181 | /* The *_rcu iterators not needed here because we are |
| 182 | always called with audit_netlink_sem held. */ |
| 183 | for (i=0; i<AUDIT_NR_FILTERS; i++) { |
| 184 | list_for_each_entry(entry, &audit_filter_list[i], list) |
| 185 | audit_send_reply(pid, seq, AUDIT_LIST, 0, 1, |
| 186 | &entry->rule, sizeof(entry->rule)); |
| 187 | } |
| 188 | audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0); |
| 189 | |
| 190 | up(&audit_netlink_sem); |
| 191 | return 0; |
| 192 | } |
| 193 | |
| 194 | /** |
| 195 | * audit_receive_filter - apply all rules to the specified message type |
| 196 | * @type: audit message type |
| 197 | * @pid: target pid for netlink audit messages |
| 198 | * @uid: target uid for netlink audit messages |
| 199 | * @seq: netlink audit message sequence (serial) number |
| 200 | * @data: payload data |
| 201 | * @loginuid: loginuid of sender |
| 202 | */ |
| 203 | int audit_receive_filter(int type, int pid, int uid, int seq, void *data, |
| 204 | uid_t loginuid) |
| 205 | { |
| 206 | struct task_struct *tsk; |
| 207 | int *dest; |
| 208 | int err = 0; |
| 209 | unsigned listnr; |
| 210 | |
| 211 | switch (type) { |
| 212 | case AUDIT_LIST: |
| 213 | /* We can't just spew out the rules here because we might fill |
| 214 | * the available socket buffer space and deadlock waiting for |
| 215 | * auditctl to read from it... which isn't ever going to |
| 216 | * happen if we're actually running in the context of auditctl |
| 217 | * trying to _send_ the stuff */ |
| 218 | |
| 219 | dest = kmalloc(2 * sizeof(int), GFP_KERNEL); |
| 220 | if (!dest) |
| 221 | return -ENOMEM; |
| 222 | dest[0] = pid; |
| 223 | dest[1] = seq; |
| 224 | |
| 225 | tsk = kthread_run(audit_list_rules, dest, "audit_list_rules"); |
| 226 | if (IS_ERR(tsk)) { |
| 227 | kfree(dest); |
| 228 | err = PTR_ERR(tsk); |
| 229 | } |
| 230 | break; |
| 231 | case AUDIT_ADD: |
| 232 | listnr = ((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND; |
| 233 | switch(listnr) { |
| 234 | default: |
| 235 | return -EINVAL; |
| 236 | |
| 237 | case AUDIT_FILTER_USER: |
| 238 | case AUDIT_FILTER_TYPE: |
| 239 | #ifdef CONFIG_AUDITSYSCALL |
| 240 | case AUDIT_FILTER_ENTRY: |
| 241 | case AUDIT_FILTER_EXIT: |
| 242 | case AUDIT_FILTER_TASK: |
| 243 | #endif |
| 244 | ; |
| 245 | } |
| 246 | err = audit_add_rule(data, &audit_filter_list[listnr]); |
| 247 | if (!err) |
| 248 | audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, |
| 249 | "auid=%u added an audit rule\n", loginuid); |
| 250 | break; |
| 251 | case AUDIT_DEL: |
| 252 | listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND; |
| 253 | if (listnr >= AUDIT_NR_FILTERS) |
| 254 | return -EINVAL; |
| 255 | |
| 256 | err = audit_del_rule(data, &audit_filter_list[listnr]); |
| 257 | if (!err) |
| 258 | audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, |
| 259 | "auid=%u removed an audit rule\n", loginuid); |
| 260 | break; |
| 261 | default: |
| 262 | return -EINVAL; |
| 263 | } |
| 264 | |
| 265 | return err; |
| 266 | } |
| 267 | |
| 268 | int audit_comparator(const u32 left, const u32 op, const u32 right) |
| 269 | { |
| 270 | switch (op) { |
| 271 | case AUDIT_EQUAL: |
| 272 | return (left == right); |
| 273 | case AUDIT_NOT_EQUAL: |
| 274 | return (left != right); |
| 275 | case AUDIT_LESS_THAN: |
| 276 | return (left < right); |
| 277 | case AUDIT_LESS_THAN_OR_EQUAL: |
| 278 | return (left <= right); |
| 279 | case AUDIT_GREATER_THAN: |
| 280 | return (left > right); |
| 281 | case AUDIT_GREATER_THAN_OR_EQUAL: |
| 282 | return (left >= right); |
| 283 | default: |
| 284 | return -EINVAL; |
| 285 | } |
| 286 | } |
| 287 | |
| 288 | |
| 289 | |
| 290 | static int audit_filter_user_rules(struct netlink_skb_parms *cb, |
| 291 | struct audit_rule *rule, |
| 292 | enum audit_state *state) |
| 293 | { |
| 294 | int i; |
| 295 | |
| 296 | for (i = 0; i < rule->field_count; i++) { |
| 297 | u32 field = rule->fields[i] & ~AUDIT_OPERATORS; |
| 298 | u32 op = rule->fields[i] & AUDIT_OPERATORS; |
| 299 | u32 value = rule->values[i]; |
| 300 | int result = 0; |
| 301 | |
| 302 | switch (field) { |
| 303 | case AUDIT_PID: |
| 304 | result = audit_comparator(cb->creds.pid, op, value); |
| 305 | break; |
| 306 | case AUDIT_UID: |
| 307 | result = audit_comparator(cb->creds.uid, op, value); |
| 308 | break; |
| 309 | case AUDIT_GID: |
| 310 | result = audit_comparator(cb->creds.gid, op, value); |
| 311 | break; |
| 312 | case AUDIT_LOGINUID: |
| 313 | result = audit_comparator(cb->loginuid, op, value); |
| 314 | break; |
| 315 | } |
| 316 | |
| 317 | if (!result) |
| 318 | return 0; |
| 319 | } |
| 320 | switch (rule->action) { |
| 321 | case AUDIT_NEVER: *state = AUDIT_DISABLED; break; |
| 322 | case AUDIT_POSSIBLE: *state = AUDIT_BUILD_CONTEXT; break; |
| 323 | case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break; |
| 324 | } |
| 325 | return 1; |
| 326 | } |
| 327 | |
| 328 | int audit_filter_user(struct netlink_skb_parms *cb, int type) |
| 329 | { |
| 330 | struct audit_entry *e; |
| 331 | enum audit_state state; |
| 332 | int ret = 1; |
| 333 | |
| 334 | rcu_read_lock(); |
| 335 | list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) { |
| 336 | if (audit_filter_user_rules(cb, &e->rule, &state)) { |
| 337 | if (state == AUDIT_DISABLED) |
| 338 | ret = 0; |
| 339 | break; |
| 340 | } |
| 341 | } |
| 342 | rcu_read_unlock(); |
| 343 | |
| 344 | return ret; /* Audit by default */ |
| 345 | } |
| 346 | |
| 347 | int audit_filter_type(int type) |
| 348 | { |
| 349 | struct audit_entry *e; |
| 350 | int result = 0; |
| 351 | |
| 352 | rcu_read_lock(); |
| 353 | if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE])) |
| 354 | goto unlock_and_return; |
| 355 | |
| 356 | list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE], |
| 357 | list) { |
| 358 | struct audit_rule *rule = &e->rule; |
| 359 | int i; |
| 360 | for (i = 0; i < rule->field_count; i++) { |
| 361 | u32 field = rule->fields[i] & ~AUDIT_OPERATORS; |
| 362 | u32 op = rule->fields[i] & AUDIT_OPERATORS; |
| 363 | u32 value = rule->values[i]; |
| 364 | if ( field == AUDIT_MSGTYPE ) { |
| 365 | result = audit_comparator(type, op, value); |
| 366 | if (!result) |
| 367 | break; |
| 368 | } |
| 369 | } |
| 370 | if (result) |
| 371 | goto unlock_and_return; |
| 372 | } |
| 373 | unlock_and_return: |
| 374 | rcu_read_unlock(); |
| 375 | return result; |
| 376 | } |
| 377 | |
| 378 | |