2 * Copyright (C) 2008 IBM Corporation
3 * Author: Mimi Zohar <zohar@us.ibm.com>
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, version 2 of the License.
10 * - initialize default measure policy rules
13 #include <linux/module.h>
14 #include <linux/list.h>
15 #include <linux/security.h>
16 #include <linux/magic.h>
17 #include <linux/parser.h>
18 #include <linux/slab.h>
22 /* flags definitions */
23 #define IMA_FUNC 0x0001
24 #define IMA_MASK 0x0002
25 #define IMA_FSMAGIC 0x0004
26 #define IMA_UID 0x0008
28 enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
30 #define MAX_LSM_RULES 6
31 enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
32 LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
35 struct ima_measure_rule_entry {
36 struct list_head list;
37 enum ima_action action;
41 unsigned long fsmagic;
44 void *rule; /* LSM file metadata specific */
45 int type; /* audit type */
50 * Without LSM specific knowledge, the default policy can only be
51 * written in terms of .action, .func, .mask, .fsmagic, and .uid
55 * The minimum rule set to allow for full TCB coverage. Measures all files
56 * opened or mmap for exec and everything read by root. Dangerous because
57 * normal users can easily run the machine out of memory simply building
58 * and running executables.
60 static struct ima_measure_rule_entry default_rules[] = {
61 {.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC},
62 {.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
63 {.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
64 {.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC},
65 {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC},
66 {.action = DONT_MEASURE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC},
67 {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC,
68 .flags = IMA_FUNC | IMA_MASK},
69 {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC,
70 .flags = IMA_FUNC | IMA_MASK},
71 {.action = MEASURE,.func = FILE_CHECK,.mask = MAY_READ,.uid = 0,
72 .flags = IMA_FUNC | IMA_MASK | IMA_UID},
75 static LIST_HEAD(measure_default_rules);
76 static LIST_HEAD(measure_policy_rules);
77 static struct list_head *ima_measure;
79 static DEFINE_MUTEX(ima_measure_mutex);
81 static bool ima_use_tcb __initdata;
82 static int __init default_policy_setup(char *str)
87 __setup("ima_tcb", default_policy_setup);
90 * ima_match_rules - determine whether an inode matches the measure rule.
91 * @rule: a pointer to a rule
92 * @inode: a pointer to an inode
93 * @func: LIM hook identifier
94 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
96 * Returns true on rule match, false on failure.
98 static bool ima_match_rules(struct ima_measure_rule_entry *rule,
99 struct inode *inode, enum ima_hooks func, int mask)
101 struct task_struct *tsk = current;
104 if ((rule->flags & IMA_FUNC) && rule->func != func)
106 if ((rule->flags & IMA_MASK) && rule->mask != mask)
108 if ((rule->flags & IMA_FSMAGIC)
109 && rule->fsmagic != inode->i_sb->s_magic)
111 if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
113 for (i = 0; i < MAX_LSM_RULES; i++) {
117 if (!rule->lsm[i].rule)
124 security_inode_getsecid(inode, &osid);
125 rc = security_filter_rule_match(osid,
134 security_task_getsecid(tsk, &sid);
135 rc = security_filter_rule_match(sid,
150 * ima_match_policy - decision based on LSM and other conditions
151 * @inode: pointer to an inode for which the policy decision is being made
152 * @func: IMA hook identifier
153 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
155 * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
158 * (There is no need for locking when walking the policy list,
159 * as elements in the list are never deleted, nor does the list
162 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
164 struct ima_measure_rule_entry *entry;
166 list_for_each_entry(entry, ima_measure, list) {
169 rc = ima_match_rules(entry, inode, func, mask);
171 return entry->action;
177 * ima_init_policy - initialize the default measure rules.
179 * ima_measure points to either the measure_default_rules or the
180 * the new measure_policy_rules.
182 void __init ima_init_policy(void)
186 /* if !ima_use_tcb set entries = 0 so we load NO default rules */
188 entries = ARRAY_SIZE(default_rules);
192 for (i = 0; i < entries; i++)
193 list_add_tail(&default_rules[i].list, &measure_default_rules);
194 ima_measure = &measure_default_rules;
198 * ima_update_policy - update default_rules with new measure rules
200 * Called on file .release to update the default rules with a complete new
201 * policy. Once updated, the policy is locked, no additional rules can be
202 * added to the policy.
204 void ima_update_policy(void)
206 const char *op = "policy_update";
207 const char *cause = "already exists";
211 if (ima_measure == &measure_default_rules) {
212 ima_measure = &measure_policy_rules;
216 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
217 NULL, op, cause, result, audit_info);
222 Opt_measure = 1, Opt_dont_measure,
223 Opt_obj_user, Opt_obj_role, Opt_obj_type,
224 Opt_subj_user, Opt_subj_role, Opt_subj_type,
225 Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
228 static match_table_t policy_tokens = {
229 {Opt_measure, "measure"},
230 {Opt_dont_measure, "dont_measure"},
231 {Opt_obj_user, "obj_user=%s"},
232 {Opt_obj_role, "obj_role=%s"},
233 {Opt_obj_type, "obj_type=%s"},
234 {Opt_subj_user, "subj_user=%s"},
235 {Opt_subj_role, "subj_role=%s"},
236 {Opt_subj_type, "subj_type=%s"},
237 {Opt_func, "func=%s"},
238 {Opt_mask, "mask=%s"},
239 {Opt_fsmagic, "fsmagic=%s"},
244 static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
245 char *args, int lsm_rule, int audit_type)
249 if (entry->lsm[lsm_rule].rule)
252 entry->lsm[lsm_rule].type = audit_type;
253 result = security_filter_rule_init(entry->lsm[lsm_rule].type,
255 &entry->lsm[lsm_rule].rule);
259 static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
261 audit_log_format(ab, "%s=", key);
262 audit_log_untrustedstring(ab, value);
263 audit_log_format(ab, " ");
266 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
268 struct audit_buffer *ab;
272 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
275 entry->action = UNKNOWN;
276 while ((p = strsep(&rule, " \t")) != NULL) {
277 substring_t args[MAX_OPT_ARGS];
283 if ((*p == '\0') || (*p == ' ') || (*p == '\t'))
285 token = match_token(p, policy_tokens, args);
288 ima_log_string(ab, "action", "measure");
290 if (entry->action != UNKNOWN)
293 entry->action = MEASURE;
295 case Opt_dont_measure:
296 ima_log_string(ab, "action", "dont_measure");
298 if (entry->action != UNKNOWN)
301 entry->action = DONT_MEASURE;
304 ima_log_string(ab, "func", args[0].from);
309 if (strcmp(args[0].from, "FILE_CHECK") == 0)
310 entry->func = FILE_CHECK;
311 /* PATH_CHECK is for backwards compat */
312 else if (strcmp(args[0].from, "PATH_CHECK") == 0)
313 entry->func = FILE_CHECK;
314 else if (strcmp(args[0].from, "FILE_MMAP") == 0)
315 entry->func = FILE_MMAP;
316 else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
317 entry->func = BPRM_CHECK;
321 entry->flags |= IMA_FUNC;
324 ima_log_string(ab, "mask", args[0].from);
329 if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
330 entry->mask = MAY_EXEC;
331 else if (strcmp(args[0].from, "MAY_WRITE") == 0)
332 entry->mask = MAY_WRITE;
333 else if (strcmp(args[0].from, "MAY_READ") == 0)
334 entry->mask = MAY_READ;
335 else if (strcmp(args[0].from, "MAY_APPEND") == 0)
336 entry->mask = MAY_APPEND;
340 entry->flags |= IMA_MASK;
343 ima_log_string(ab, "fsmagic", args[0].from);
345 if (entry->fsmagic) {
350 result = strict_strtoul(args[0].from, 16,
353 entry->flags |= IMA_FSMAGIC;
356 ima_log_string(ab, "uid", args[0].from);
358 if (entry->uid != -1) {
363 result = strict_strtoul(args[0].from, 10, &lnum);
365 entry->uid = (uid_t) lnum;
366 if (entry->uid != lnum)
369 entry->flags |= IMA_UID;
373 ima_log_string(ab, "obj_user", args[0].from);
374 result = ima_lsm_rule_init(entry, args[0].from,
379 ima_log_string(ab, "obj_role", args[0].from);
380 result = ima_lsm_rule_init(entry, args[0].from,
385 ima_log_string(ab, "obj_type", args[0].from);
386 result = ima_lsm_rule_init(entry, args[0].from,
391 ima_log_string(ab, "subj_user", args[0].from);
392 result = ima_lsm_rule_init(entry, args[0].from,
397 ima_log_string(ab, "subj_role", args[0].from);
398 result = ima_lsm_rule_init(entry, args[0].from,
403 ima_log_string(ab, "subj_type", args[0].from);
404 result = ima_lsm_rule_init(entry, args[0].from,
409 ima_log_string(ab, "UNKNOWN", p);
414 if (!result && (entry->action == UNKNOWN))
417 audit_log_format(ab, "res=%d", !!result);
423 * ima_parse_add_rule - add a rule to measure_policy_rules
424 * @rule - ima measurement policy rule
426 * Uses a mutex to protect the policy list from multiple concurrent writers.
427 * Returns the length of the rule parsed, an error code on failure
429 ssize_t ima_parse_add_rule(char *rule)
431 const char *op = "update_policy";
433 struct ima_measure_rule_entry *entry;
437 /* Prevent installed policy from changing */
438 if (ima_measure != &measure_default_rules) {
439 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
440 NULL, op, "already exists",
441 -EACCES, audit_info);
445 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
447 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
448 NULL, op, "-ENOMEM", -ENOMEM, audit_info);
452 INIT_LIST_HEAD(&entry->list);
454 p = strsep(&rule, "\n");
462 result = ima_parse_rule(p, entry);
465 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
466 NULL, op, "invalid policy", result,
471 mutex_lock(&ima_measure_mutex);
472 list_add_tail(&entry->list, &measure_policy_rules);
473 mutex_unlock(&ima_measure_mutex);
478 /* ima_delete_rules called to cleanup invalid policy */
479 void ima_delete_rules(void)
481 struct ima_measure_rule_entry *entry, *tmp;
483 mutex_lock(&ima_measure_mutex);
484 list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
485 list_del(&entry->list);
488 mutex_unlock(&ima_measure_mutex);