d661afbe474c2fce8f74907869be0a644c5789c9
[linux-2.6.git] / security / integrity / ima / ima_policy.c
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 #include <linux/slab.h>
19
20 #include "ima.h"
21
22 /* flags definitions */
23 #define IMA_FUNC        0x0001
24 #define IMA_MASK        0x0002
25 #define IMA_FSMAGIC     0x0004
26 #define IMA_UID         0x0008
27
28 enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
29
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
33 };
34
35 struct ima_measure_rule_entry {
36         struct list_head list;
37         enum ima_action action;
38         unsigned int flags;
39         enum ima_hooks func;
40         int mask;
41         unsigned long fsmagic;
42         uid_t uid;
43         struct {
44                 void *rule;     /* LSM file metadata specific */
45                 int type;       /* audit type */
46         } lsm[MAX_LSM_RULES];
47 };
48
49 /*
50  * Without LSM specific knowledge, the default policy can only be
51  * written in terms of .action, .func, .mask, .fsmagic, and .uid
52  */
53
54 /*
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.
59  */
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},
73 };
74
75 static LIST_HEAD(measure_default_rules);
76 static LIST_HEAD(measure_policy_rules);
77 static struct list_head *ima_measure;
78
79 static DEFINE_MUTEX(ima_measure_mutex);
80
81 static bool ima_use_tcb __initdata;
82 static int __init default_policy_setup(char *str)
83 {
84         ima_use_tcb = 1;
85         return 1;
86 }
87 __setup("ima_tcb", default_policy_setup);
88
89 /**
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)
95  *
96  * Returns true on rule match, false on failure.
97  */
98 static bool ima_match_rules(struct ima_measure_rule_entry *rule,
99                             struct inode *inode, enum ima_hooks func, int mask)
100 {
101         struct task_struct *tsk = current;
102         int i;
103
104         if ((rule->flags & IMA_FUNC) && rule->func != func)
105                 return false;
106         if ((rule->flags & IMA_MASK) && rule->mask != mask)
107                 return false;
108         if ((rule->flags & IMA_FSMAGIC)
109             && rule->fsmagic != inode->i_sb->s_magic)
110                 return false;
111         if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
112                 return false;
113         for (i = 0; i < MAX_LSM_RULES; i++) {
114                 int rc = 0;
115                 u32 osid, sid;
116
117                 if (!rule->lsm[i].rule)
118                         continue;
119
120                 switch (i) {
121                 case LSM_OBJ_USER:
122                 case LSM_OBJ_ROLE:
123                 case LSM_OBJ_TYPE:
124                         security_inode_getsecid(inode, &osid);
125                         rc = security_filter_rule_match(osid,
126                                                         rule->lsm[i].type,
127                                                         Audit_equal,
128                                                         rule->lsm[i].rule,
129                                                         NULL);
130                         break;
131                 case LSM_SUBJ_USER:
132                 case LSM_SUBJ_ROLE:
133                 case LSM_SUBJ_TYPE:
134                         security_task_getsecid(tsk, &sid);
135                         rc = security_filter_rule_match(sid,
136                                                         rule->lsm[i].type,
137                                                         Audit_equal,
138                                                         rule->lsm[i].rule,
139                                                         NULL);
140                 default:
141                         break;
142                 }
143                 if (!rc)
144                         return false;
145         }
146         return true;
147 }
148
149 /**
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)
154  *
155  * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
156  * conditions.
157  *
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
160  * change.)
161  */
162 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
163 {
164         struct ima_measure_rule_entry *entry;
165
166         list_for_each_entry(entry, ima_measure, list) {
167                 bool rc;
168
169                 rc = ima_match_rules(entry, inode, func, mask);
170                 if (rc)
171                         return entry->action;
172         }
173         return 0;
174 }
175
176 /**
177  * ima_init_policy - initialize the default measure rules.
178  *
179  * ima_measure points to either the measure_default_rules or the
180  * the new measure_policy_rules.
181  */
182 void __init ima_init_policy(void)
183 {
184         int i, entries;
185
186         /* if !ima_use_tcb set entries = 0 so we load NO default rules */
187         if (ima_use_tcb)
188                 entries = ARRAY_SIZE(default_rules);
189         else
190                 entries = 0;
191
192         for (i = 0; i < entries; i++)
193                 list_add_tail(&default_rules[i].list, &measure_default_rules);
194         ima_measure = &measure_default_rules;
195 }
196
197 /**
198  * ima_update_policy - update default_rules with new measure rules
199  *
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.
203  */
204 void ima_update_policy(void)
205 {
206         const char *op = "policy_update";
207         const char *cause = "already exists";
208         int result = 1;
209         int audit_info = 0;
210
211         if (ima_measure == &measure_default_rules) {
212                 ima_measure = &measure_policy_rules;
213                 cause = "complete";
214                 result = 0;
215         }
216         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
217                             NULL, op, cause, result, audit_info);
218 }
219
220 enum {
221         Opt_err = -1,
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
226 };
227
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"},
240         {Opt_uid, "uid=%s"},
241         {Opt_err, NULL}
242 };
243
244 static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
245                              char *args, int lsm_rule, int audit_type)
246 {
247         int result;
248
249         if (entry->lsm[lsm_rule].rule)
250                 return -EINVAL;
251
252         entry->lsm[lsm_rule].type = audit_type;
253         result = security_filter_rule_init(entry->lsm[lsm_rule].type,
254                                            Audit_equal, args,
255                                            &entry->lsm[lsm_rule].rule);
256         if (!entry->lsm[lsm_rule].rule)
257                 return -EINVAL;
258         return result;
259 }
260
261 static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
262 {
263         audit_log_format(ab, "%s=", key);
264         audit_log_untrustedstring(ab, value);
265         audit_log_format(ab, " ");
266 }
267
268 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
269 {
270         struct audit_buffer *ab;
271         char *p;
272         int result = 0;
273
274         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
275
276         entry->uid = -1;
277         entry->action = UNKNOWN;
278         while ((p = strsep(&rule, " \t")) != NULL) {
279                 substring_t args[MAX_OPT_ARGS];
280                 int token;
281                 unsigned long lnum;
282
283                 if (result < 0)
284                         break;
285                 if ((*p == '\0') || (*p == ' ') || (*p == '\t'))
286                         continue;
287                 token = match_token(p, policy_tokens, args);
288                 switch (token) {
289                 case Opt_measure:
290                         ima_log_string(ab, "action", "measure");
291
292                         if (entry->action != UNKNOWN)
293                                 result = -EINVAL;
294
295                         entry->action = MEASURE;
296                         break;
297                 case Opt_dont_measure:
298                         ima_log_string(ab, "action", "dont_measure");
299
300                         if (entry->action != UNKNOWN)
301                                 result = -EINVAL;
302
303                         entry->action = DONT_MEASURE;
304                         break;
305                 case Opt_func:
306                         ima_log_string(ab, "func", args[0].from);
307
308                         if (entry->func)
309                                 result  = -EINVAL;
310
311                         if (strcmp(args[0].from, "FILE_CHECK") == 0)
312                                 entry->func = FILE_CHECK;
313                         /* PATH_CHECK is for backwards compat */
314                         else if (strcmp(args[0].from, "PATH_CHECK") == 0)
315                                 entry->func = FILE_CHECK;
316                         else if (strcmp(args[0].from, "FILE_MMAP") == 0)
317                                 entry->func = FILE_MMAP;
318                         else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
319                                 entry->func = BPRM_CHECK;
320                         else
321                                 result = -EINVAL;
322                         if (!result)
323                                 entry->flags |= IMA_FUNC;
324                         break;
325                 case Opt_mask:
326                         ima_log_string(ab, "mask", args[0].from);
327
328                         if (entry->mask)
329                                 result = -EINVAL;
330
331                         if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
332                                 entry->mask = MAY_EXEC;
333                         else if (strcmp(args[0].from, "MAY_WRITE") == 0)
334                                 entry->mask = MAY_WRITE;
335                         else if (strcmp(args[0].from, "MAY_READ") == 0)
336                                 entry->mask = MAY_READ;
337                         else if (strcmp(args[0].from, "MAY_APPEND") == 0)
338                                 entry->mask = MAY_APPEND;
339                         else
340                                 result = -EINVAL;
341                         if (!result)
342                                 entry->flags |= IMA_MASK;
343                         break;
344                 case Opt_fsmagic:
345                         ima_log_string(ab, "fsmagic", args[0].from);
346
347                         if (entry->fsmagic) {
348                                 result = -EINVAL;
349                                 break;
350                         }
351
352                         result = strict_strtoul(args[0].from, 16,
353                                                 &entry->fsmagic);
354                         if (!result)
355                                 entry->flags |= IMA_FSMAGIC;
356                         break;
357                 case Opt_uid:
358                         ima_log_string(ab, "uid", args[0].from);
359
360                         if (entry->uid != -1) {
361                                 result = -EINVAL;
362                                 break;
363                         }
364
365                         result = strict_strtoul(args[0].from, 10, &lnum);
366                         if (!result) {
367                                 entry->uid = (uid_t) lnum;
368                                 if (entry->uid != lnum)
369                                         result = -EINVAL;
370                                 else
371                                         entry->flags |= IMA_UID;
372                         }
373                         break;
374                 case Opt_obj_user:
375                         ima_log_string(ab, "obj_user", args[0].from);
376                         result = ima_lsm_rule_init(entry, args[0].from,
377                                                    LSM_OBJ_USER,
378                                                    AUDIT_OBJ_USER);
379                         break;
380                 case Opt_obj_role:
381                         ima_log_string(ab, "obj_role", args[0].from);
382                         result = ima_lsm_rule_init(entry, args[0].from,
383                                                    LSM_OBJ_ROLE,
384                                                    AUDIT_OBJ_ROLE);
385                         break;
386                 case Opt_obj_type:
387                         ima_log_string(ab, "obj_type", args[0].from);
388                         result = ima_lsm_rule_init(entry, args[0].from,
389                                                    LSM_OBJ_TYPE,
390                                                    AUDIT_OBJ_TYPE);
391                         break;
392                 case Opt_subj_user:
393                         ima_log_string(ab, "subj_user", args[0].from);
394                         result = ima_lsm_rule_init(entry, args[0].from,
395                                                    LSM_SUBJ_USER,
396                                                    AUDIT_SUBJ_USER);
397                         break;
398                 case Opt_subj_role:
399                         ima_log_string(ab, "subj_role", args[0].from);
400                         result = ima_lsm_rule_init(entry, args[0].from,
401                                                    LSM_SUBJ_ROLE,
402                                                    AUDIT_SUBJ_ROLE);
403                         break;
404                 case Opt_subj_type:
405                         ima_log_string(ab, "subj_type", args[0].from);
406                         result = ima_lsm_rule_init(entry, args[0].from,
407                                                    LSM_SUBJ_TYPE,
408                                                    AUDIT_SUBJ_TYPE);
409                         break;
410                 case Opt_err:
411                         ima_log_string(ab, "UNKNOWN", p);
412                         result = -EINVAL;
413                         break;
414                 }
415         }
416         if (!result && (entry->action == UNKNOWN))
417                 result = -EINVAL;
418
419         audit_log_format(ab, "res=%d", !!result);
420         audit_log_end(ab);
421         return result;
422 }
423
424 /**
425  * ima_parse_add_rule - add a rule to measure_policy_rules
426  * @rule - ima measurement policy rule
427  *
428  * Uses a mutex to protect the policy list from multiple concurrent writers.
429  * Returns the length of the rule parsed, an error code on failure
430  */
431 ssize_t ima_parse_add_rule(char *rule)
432 {
433         const char *op = "update_policy";
434         char *p;
435         struct ima_measure_rule_entry *entry;
436         ssize_t result, len;
437         int audit_info = 0;
438
439         /* Prevent installed policy from changing */
440         if (ima_measure != &measure_default_rules) {
441                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
442                                     NULL, op, "already exists",
443                                     -EACCES, audit_info);
444                 return -EACCES;
445         }
446
447         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
448         if (!entry) {
449                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
450                                     NULL, op, "-ENOMEM", -ENOMEM, audit_info);
451                 return -ENOMEM;
452         }
453
454         INIT_LIST_HEAD(&entry->list);
455
456         p = strsep(&rule, "\n");
457         len = strlen(p) + 1;
458
459         if (*p == '#') {
460                 kfree(entry);
461                 return len;
462         }
463
464         result = ima_parse_rule(p, entry);
465         if (result) {
466                 kfree(entry);
467                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
468                                     NULL, op, "invalid policy", result,
469                                     audit_info);
470                 return result;
471         }
472
473         mutex_lock(&ima_measure_mutex);
474         list_add_tail(&entry->list, &measure_policy_rules);
475         mutex_unlock(&ima_measure_mutex);
476
477         return len;
478 }
479
480 /* ima_delete_rules called to cleanup invalid policy */
481 void ima_delete_rules(void)
482 {
483         struct ima_measure_rule_entry *entry, *tmp;
484
485         mutex_lock(&ima_measure_mutex);
486         list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
487                 list_del(&entry->list);
488                 kfree(entry);
489         }
490         mutex_unlock(&ima_measure_mutex);
491 }