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>
21 /* flags definitions */
22 #define IMA_FUNC 0x0001
23 #define IMA_MASK 0x0002
24 #define IMA_FSMAGIC 0x0004
25 #define IMA_UID 0x0008
27 enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
29 #define MAX_LSM_RULES 6
30 enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
31 LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
34 struct ima_measure_rule_entry {
35 struct list_head list;
36 enum ima_action action;
40 unsigned long fsmagic;
43 void *rule; /* LSM file metadata specific */
44 int type; /* audit type */
49 * Without LSM specific knowledge, the default policy can only be
50 * written in terms of .action, .func, .mask, .fsmagic, and .uid
54 * The minimum rule set to allow for full TCB coverage. Measures all files
55 * opened or mmap for exec and everything read by root. Dangerous because
56 * normal users can easily run the machine out of memory simply building
57 * and running executables.
59 static struct ima_measure_rule_entry default_rules[] = {
60 {.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC},
61 {.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
62 {.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
63 {.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC},
64 {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC},
65 {.action = DONT_MEASURE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC},
66 {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC,
67 .flags = IMA_FUNC | IMA_MASK},
68 {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC,
69 .flags = IMA_FUNC | IMA_MASK},
70 {.action = MEASURE,.func = PATH_CHECK,.mask = MAY_READ,.uid = 0,
71 .flags = IMA_FUNC | IMA_MASK | IMA_UID},
74 static LIST_HEAD(measure_default_rules);
75 static LIST_HEAD(measure_policy_rules);
76 static struct list_head *ima_measure;
78 static DEFINE_MUTEX(ima_measure_mutex);
80 static bool ima_use_tcb __initdata;
81 static int __init default_policy_setup(char *str)
86 __setup("ima_tcb", default_policy_setup);
89 * ima_match_rules - determine whether an inode matches the measure rule.
90 * @rule: a pointer to a rule
91 * @inode: a pointer to an inode
92 * @func: LIM hook identifier
93 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
95 * Returns true on rule match, false on failure.
97 static bool ima_match_rules(struct ima_measure_rule_entry *rule,
98 struct inode *inode, enum ima_hooks func, int mask)
100 struct task_struct *tsk = current;
103 if ((rule->flags & IMA_FUNC) && rule->func != func)
105 if ((rule->flags & IMA_MASK) && rule->mask != mask)
107 if ((rule->flags & IMA_FSMAGIC)
108 && rule->fsmagic != inode->i_sb->s_magic)
110 if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
112 for (i = 0; i < MAX_LSM_RULES; i++) {
116 if (!rule->lsm[i].rule)
123 security_inode_getsecid(inode, &osid);
124 rc = security_filter_rule_match(osid,
133 security_task_getsecid(tsk, &sid);
134 rc = security_filter_rule_match(sid,
149 * ima_match_policy - decision based on LSM and other conditions
150 * @inode: pointer to an inode for which the policy decision is being made
151 * @func: IMA hook identifier
152 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
154 * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
157 * (There is no need for locking when walking the policy list,
158 * as elements in the list are never deleted, nor does the list
161 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
163 struct ima_measure_rule_entry *entry;
165 list_for_each_entry(entry, ima_measure, list) {
168 rc = ima_match_rules(entry, inode, func, mask);
170 return entry->action;
176 * ima_init_policy - initialize the default measure rules.
178 * ima_measure points to either the measure_default_rules or the
179 * the new measure_policy_rules.
181 void __init ima_init_policy(void)
185 /* if !ima_use_tcb set entries = 0 so we load NO default rules */
187 entries = ARRAY_SIZE(default_rules);
191 for (i = 0; i < entries; i++)
192 list_add_tail(&default_rules[i].list, &measure_default_rules);
193 ima_measure = &measure_default_rules;
197 * ima_update_policy - update default_rules with new measure rules
199 * Called on file .release to update the default rules with a complete new
200 * policy. Once updated, the policy is locked, no additional rules can be
201 * added to the policy.
203 void ima_update_policy(void)
205 const char *op = "policy_update";
206 const char *cause = "already exists";
210 if (ima_measure == &measure_default_rules) {
211 ima_measure = &measure_policy_rules;
215 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
216 NULL, op, cause, result, audit_info);
221 Opt_measure = 1, Opt_dont_measure,
222 Opt_obj_user, Opt_obj_role, Opt_obj_type,
223 Opt_subj_user, Opt_subj_role, Opt_subj_type,
224 Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
227 static match_table_t policy_tokens = {
228 {Opt_measure, "measure"},
229 {Opt_dont_measure, "dont_measure"},
230 {Opt_obj_user, "obj_user=%s"},
231 {Opt_obj_role, "obj_role=%s"},
232 {Opt_obj_type, "obj_type=%s"},
233 {Opt_subj_user, "subj_user=%s"},
234 {Opt_subj_role, "subj_role=%s"},
235 {Opt_subj_type, "subj_type=%s"},
236 {Opt_func, "func=%s"},
237 {Opt_mask, "mask=%s"},
238 {Opt_fsmagic, "fsmagic=%s"},
243 static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
244 char *args, int lsm_rule, int audit_type)
248 entry->lsm[lsm_rule].type = audit_type;
249 result = security_filter_rule_init(entry->lsm[lsm_rule].type,
251 &entry->lsm[lsm_rule].rule);
255 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
257 struct audit_buffer *ab;
261 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
264 while ((p = strsep(&rule, " \n")) != NULL) {
265 substring_t args[MAX_OPT_ARGS];
273 token = match_token(p, policy_tokens, args);
276 audit_log_format(ab, "%s ", "measure");
277 entry->action = MEASURE;
279 case Opt_dont_measure:
280 audit_log_format(ab, "%s ", "dont_measure");
281 entry->action = DONT_MEASURE;
284 audit_log_format(ab, "func=%s ", args[0].from);
285 if (strcmp(args[0].from, "PATH_CHECK") == 0)
286 entry->func = PATH_CHECK;
287 else if (strcmp(args[0].from, "FILE_MMAP") == 0)
288 entry->func = FILE_MMAP;
289 else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
290 entry->func = BPRM_CHECK;
294 entry->flags |= IMA_FUNC;
297 audit_log_format(ab, "mask=%s ", args[0].from);
298 if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
299 entry->mask = MAY_EXEC;
300 else if (strcmp(args[0].from, "MAY_WRITE") == 0)
301 entry->mask = MAY_WRITE;
302 else if (strcmp(args[0].from, "MAY_READ") == 0)
303 entry->mask = MAY_READ;
304 else if (strcmp(args[0].from, "MAY_APPEND") == 0)
305 entry->mask = MAY_APPEND;
309 entry->flags |= IMA_MASK;
312 audit_log_format(ab, "fsmagic=%s ", args[0].from);
313 result = strict_strtoul(args[0].from, 16,
316 entry->flags |= IMA_FSMAGIC;
319 audit_log_format(ab, "uid=%s ", args[0].from);
320 result = strict_strtoul(args[0].from, 10, &lnum);
322 entry->uid = (uid_t) lnum;
323 if (entry->uid != lnum)
326 entry->flags |= IMA_UID;
330 audit_log_format(ab, "obj_user=%s ", args[0].from);
331 result = ima_lsm_rule_init(entry, args[0].from,
336 audit_log_format(ab, "obj_role=%s ", args[0].from);
337 result = ima_lsm_rule_init(entry, args[0].from,
342 audit_log_format(ab, "obj_type=%s ", args[0].from);
343 result = ima_lsm_rule_init(entry, args[0].from,
348 audit_log_format(ab, "subj_user=%s ", args[0].from);
349 result = ima_lsm_rule_init(entry, args[0].from,
354 audit_log_format(ab, "subj_role=%s ", args[0].from);
355 result = ima_lsm_rule_init(entry, args[0].from,
360 audit_log_format(ab, "subj_type=%s ", args[0].from);
361 result = ima_lsm_rule_init(entry, args[0].from,
366 audit_log_format(ab, "UNKNOWN=%s ", p);
370 if (entry->action == UNKNOWN)
373 audit_log_format(ab, "res=%d", !result ? 0 : 1);
379 * ima_parse_add_rule - add a rule to measure_policy_rules
380 * @rule - ima measurement policy rule
382 * Uses a mutex to protect the policy list from multiple concurrent writers.
383 * Returns 0 on success, an error code on failure.
385 int ima_parse_add_rule(char *rule)
387 const char *op = "update_policy";
388 struct ima_measure_rule_entry *entry;
392 /* Prevent installed policy from changing */
393 if (ima_measure != &measure_default_rules) {
394 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
395 NULL, op, "already exists",
396 -EACCES, audit_info);
400 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
402 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
403 NULL, op, "-ENOMEM", -ENOMEM, audit_info);
407 INIT_LIST_HEAD(&entry->list);
409 result = ima_parse_rule(rule, entry);
411 mutex_lock(&ima_measure_mutex);
412 list_add_tail(&entry->list, &measure_policy_rules);
413 mutex_unlock(&ima_measure_mutex);
416 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
417 NULL, op, "invalid policy", result,
423 /* ima_delete_rules called to cleanup invalid policy */
424 void ima_delete_rules(void)
426 struct ima_measure_rule_entry *entry, *tmp;
428 mutex_lock(&ima_measure_mutex);
429 list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
430 list_del(&entry->list);
433 mutex_unlock(&ima_measure_mutex);