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-rw-r--r--security/integrity/ima/ima_policy.c414
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diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
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1/*
2 * Copyright (C) 2008 IBM Corporation
3 * Author: Mimi Zohar <zohar@us.ibm.com>
4 *
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.
8 *
9 * ima_policy.c
10 * - initialize default measure policy rules
11 *
12 */
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
19#include "ima.h"
20
21/* flags definitions */
22#define IMA_FUNC 0x0001
23#define IMA_MASK 0x0002
24#define IMA_FSMAGIC 0x0004
25#define IMA_UID 0x0008
26
27enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
28
29#define MAX_LSM_RULES 6
30enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
31 LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
32};
33
34struct ima_measure_rule_entry {
35 struct list_head list;
36 enum ima_action action;
37 unsigned int flags;
38 enum ima_hooks func;
39 int mask;
40 unsigned long fsmagic;
41 uid_t uid;
42 struct {
43 void *rule; /* LSM file metadata specific */
44 int type; /* audit type */
45 } lsm[MAX_LSM_RULES];
46};
47
48/* Without LSM specific knowledge, the default policy can only be
49 * written in terms of .action, .func, .mask, .fsmagic, and .uid
50 */
51static struct ima_measure_rule_entry default_rules[] = {
52 {.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,
53 .flags = IMA_FSMAGIC},
54 {.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC},
55 {.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC},
56 {.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC},
57 {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,
58 .flags = IMA_FSMAGIC},
59 {.action = DONT_MEASURE,.fsmagic = 0xF97CFF8C,.flags = IMA_FSMAGIC},
60 {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC,
61 .flags = IMA_FUNC | IMA_MASK},
62 {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC,
63 .flags = IMA_FUNC | IMA_MASK},
64 {.action = MEASURE,.func = PATH_CHECK,.mask = MAY_READ,.uid = 0,
65 .flags = IMA_FUNC | IMA_MASK | IMA_UID}
66};
67
68static LIST_HEAD(measure_default_rules);
69static LIST_HEAD(measure_policy_rules);
70static struct list_head *ima_measure;
71
72static DEFINE_MUTEX(ima_measure_mutex);
73
74/**
75 * ima_match_rules - determine whether an inode matches the measure rule.
76 * @rule: a pointer to a rule
77 * @inode: a pointer to an inode
78 * @func: LIM hook identifier
79 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
80 *
81 * Returns true on rule match, false on failure.
82 */
83static bool ima_match_rules(struct ima_measure_rule_entry *rule,
84 struct inode *inode, enum ima_hooks func, int mask)
85{
86 struct task_struct *tsk = current;
87 int i;
88
89 if ((rule->flags & IMA_FUNC) && rule->func != func)
90 return false;
91 if ((rule->flags & IMA_MASK) && rule->mask != mask)
92 return false;
93 if ((rule->flags & IMA_FSMAGIC)
94 && rule->fsmagic != inode->i_sb->s_magic)
95 return false;
96 if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
97 return false;
98 for (i = 0; i < MAX_LSM_RULES; i++) {
99 int rc;
100 u32 osid, sid;
101
102 if (!rule->lsm[i].rule)
103 continue;
104
105 switch (i) {
106 case LSM_OBJ_USER:
107 case LSM_OBJ_ROLE:
108 case LSM_OBJ_TYPE:
109 security_inode_getsecid(inode, &osid);
110 rc = security_filter_rule_match(osid,
111 rule->lsm[i].type,
112 AUDIT_EQUAL,
113 rule->lsm[i].rule,
114 NULL);
115 break;
116 case LSM_SUBJ_USER:
117 case LSM_SUBJ_ROLE:
118 case LSM_SUBJ_TYPE:
119 security_task_getsecid(tsk, &sid);
120 rc = security_filter_rule_match(sid,
121 rule->lsm[i].type,
122 AUDIT_EQUAL,
123 rule->lsm[i].rule,
124 NULL);
125 default:
126 break;
127 }
128 if (!rc)
129 return false;
130 }
131 return true;
132}
133
134/**
135 * ima_match_policy - decision based on LSM and other conditions
136 * @inode: pointer to an inode for which the policy decision is being made
137 * @func: IMA hook identifier
138 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
139 *
140 * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
141 * conditions.
142 *
143 * (There is no need for locking when walking the policy list,
144 * as elements in the list are never deleted, nor does the list
145 * change.)
146 */
147int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
148{
149 struct ima_measure_rule_entry *entry;
150
151 list_for_each_entry(entry, ima_measure, list) {
152 bool rc;
153
154 rc = ima_match_rules(entry, inode, func, mask);
155 if (rc)
156 return entry->action;
157 }
158 return 0;
159}
160
161/**
162 * ima_init_policy - initialize the default measure rules.
163 *
164 * ima_measure points to either the measure_default_rules or the
165 * the new measure_policy_rules.
166 */
167void ima_init_policy(void)
168{
169 int i;
170
171 for (i = 0; i < ARRAY_SIZE(default_rules); i++)
172 list_add_tail(&default_rules[i].list, &measure_default_rules);
173 ima_measure = &measure_default_rules;
174}
175
176/**
177 * ima_update_policy - update default_rules with new measure rules
178 *
179 * Called on file .release to update the default rules with a complete new
180 * policy. Once updated, the policy is locked, no additional rules can be
181 * added to the policy.
182 */
183void ima_update_policy(void)
184{
185 const char *op = "policy_update";
186 const char *cause = "already exists";
187 int result = 1;
188 int audit_info = 0;
189
190 if (ima_measure == &measure_default_rules) {
191 ima_measure = &measure_policy_rules;
192 cause = "complete";
193 result = 0;
194 }
195 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
196 NULL, op, cause, result, audit_info);
197}
198
199enum {
200 Opt_err = -1,
201 Opt_measure = 1, Opt_dont_measure,
202 Opt_obj_user, Opt_obj_role, Opt_obj_type,
203 Opt_subj_user, Opt_subj_role, Opt_subj_type,
204 Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
205};
206
207static match_table_t policy_tokens = {
208 {Opt_measure, "measure"},
209 {Opt_dont_measure, "dont_measure"},
210 {Opt_obj_user, "obj_user=%s"},
211 {Opt_obj_role, "obj_role=%s"},
212 {Opt_obj_type, "obj_type=%s"},
213 {Opt_subj_user, "subj_user=%s"},
214 {Opt_subj_role, "subj_role=%s"},
215 {Opt_subj_type, "subj_type=%s"},
216 {Opt_func, "func=%s"},
217 {Opt_mask, "mask=%s"},
218 {Opt_fsmagic, "fsmagic=%s"},
219 {Opt_uid, "uid=%s"},
220 {Opt_err, NULL}
221};
222
223static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
224 char *args, int lsm_rule, int audit_type)
225{
226 int result;
227
228 entry->lsm[lsm_rule].type = audit_type;
229 result = security_filter_rule_init(entry->lsm[lsm_rule].type,
230 AUDIT_EQUAL, args,
231 &entry->lsm[lsm_rule].rule);
232 return result;
233}
234
235static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
236{
237 struct audit_buffer *ab;
238 char *p;
239 int result = 0;
240
241 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
242
243 entry->action = -1;
244 while ((p = strsep(&rule, " \n")) != NULL) {
245 substring_t args[MAX_OPT_ARGS];
246 int token;
247 unsigned long lnum;
248
249 if (result < 0)
250 break;
251 if (!*p)
252 continue;
253 token = match_token(p, policy_tokens, args);
254 switch (token) {
255 case Opt_measure:
256 audit_log_format(ab, "%s ", "measure");
257 entry->action = MEASURE;
258 break;
259 case Opt_dont_measure:
260 audit_log_format(ab, "%s ", "dont_measure");
261 entry->action = DONT_MEASURE;
262 break;
263 case Opt_func:
264 audit_log_format(ab, "func=%s ", args[0].from);
265 if (strcmp(args[0].from, "PATH_CHECK") == 0)
266 entry->func = PATH_CHECK;
267 else if (strcmp(args[0].from, "FILE_MMAP") == 0)
268 entry->func = FILE_MMAP;
269 else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
270 entry->func = BPRM_CHECK;
271 else
272 result = -EINVAL;
273 if (!result)
274 entry->flags |= IMA_FUNC;
275 break;
276 case Opt_mask:
277 audit_log_format(ab, "mask=%s ", args[0].from);
278 if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
279 entry->mask = MAY_EXEC;
280 else if (strcmp(args[0].from, "MAY_WRITE") == 0)
281 entry->mask = MAY_WRITE;
282 else if (strcmp(args[0].from, "MAY_READ") == 0)
283 entry->mask = MAY_READ;
284 else if (strcmp(args[0].from, "MAY_APPEND") == 0)
285 entry->mask = MAY_APPEND;
286 else
287 result = -EINVAL;
288 if (!result)
289 entry->flags |= IMA_MASK;
290 break;
291 case Opt_fsmagic:
292 audit_log_format(ab, "fsmagic=%s ", args[0].from);
293 result = strict_strtoul(args[0].from, 16,
294 &entry->fsmagic);
295 if (!result)
296 entry->flags |= IMA_FSMAGIC;
297 break;
298 case Opt_uid:
299 audit_log_format(ab, "uid=%s ", args[0].from);
300 result = strict_strtoul(args[0].from, 10, &lnum);
301 if (!result) {
302 entry->uid = (uid_t) lnum;
303 if (entry->uid != lnum)
304 result = -EINVAL;
305 else
306 entry->flags |= IMA_UID;
307 }
308 break;
309 case Opt_obj_user:
310 audit_log_format(ab, "obj_user=%s ", args[0].from);
311 result = ima_lsm_rule_init(entry, args[0].from,
312 LSM_OBJ_USER,
313 AUDIT_OBJ_USER);
314 break;
315 case Opt_obj_role:
316 audit_log_format(ab, "obj_role=%s ", args[0].from);
317 result = ima_lsm_rule_init(entry, args[0].from,
318 LSM_OBJ_ROLE,
319 AUDIT_OBJ_ROLE);
320 break;
321 case Opt_obj_type:
322 audit_log_format(ab, "obj_type=%s ", args[0].from);
323 result = ima_lsm_rule_init(entry, args[0].from,
324 LSM_OBJ_TYPE,
325 AUDIT_OBJ_TYPE);
326 break;
327 case Opt_subj_user:
328 audit_log_format(ab, "subj_user=%s ", args[0].from);
329 result = ima_lsm_rule_init(entry, args[0].from,
330 LSM_SUBJ_USER,
331 AUDIT_SUBJ_USER);
332 break;
333 case Opt_subj_role:
334 audit_log_format(ab, "subj_role=%s ", args[0].from);
335 result = ima_lsm_rule_init(entry, args[0].from,
336 LSM_SUBJ_ROLE,
337 AUDIT_SUBJ_ROLE);
338 break;
339 case Opt_subj_type:
340 audit_log_format(ab, "subj_type=%s ", args[0].from);
341 result = ima_lsm_rule_init(entry, args[0].from,
342 LSM_SUBJ_TYPE,
343 AUDIT_SUBJ_TYPE);
344 break;
345 case Opt_err:
346 audit_log_format(ab, "UNKNOWN=%s ", p);
347 break;
348 }
349 }
350 if (entry->action == UNKNOWN)
351 result = -EINVAL;
352
353 audit_log_format(ab, "res=%d", !result ? 0 : 1);
354 audit_log_end(ab);
355 return result;
356}
357
358/**
359 * ima_parse_add_rule - add a rule to measure_policy_rules
360 * @rule - ima measurement policy rule
361 *
362 * Uses a mutex to protect the policy list from multiple concurrent writers.
363 * Returns 0 on success, an error code on failure.
364 */
365int ima_parse_add_rule(char *rule)
366{
367 const char *op = "update_policy";
368 struct ima_measure_rule_entry *entry;
369 int result = 0;
370 int audit_info = 0;
371
372 /* Prevent installed policy from changing */
373 if (ima_measure != &measure_default_rules) {
374 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
375 NULL, op, "already exists",
376 -EACCES, audit_info);
377 return -EACCES;
378 }
379
380 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
381 if (!entry) {
382 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
383 NULL, op, "-ENOMEM", -ENOMEM, audit_info);
384 return -ENOMEM;
385 }
386
387 INIT_LIST_HEAD(&entry->list);
388
389 result = ima_parse_rule(rule, entry);
390 if (!result) {
391 mutex_lock(&ima_measure_mutex);
392 list_add_tail(&entry->list, &measure_policy_rules);
393 mutex_unlock(&ima_measure_mutex);
394 } else {
395 kfree(entry);
396 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
397 NULL, op, "invalid policy", result,
398 audit_info);
399 }
400 return result;
401}
402
403/* ima_delete_rules called to cleanup invalid policy */
404void ima_delete_rules(void)
405{
406 struct ima_measure_rule_entry *entry, *tmp;
407
408 mutex_lock(&ima_measure_mutex);
409 list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
410 list_del(&entry->list);
411 kfree(entry);
412 }
413 mutex_unlock(&ima_measure_mutex);
414}
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