ima: fix cred sparse warning
[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         const struct cred *cred = current_cred();
103         int i;
104
105         if ((rule->flags & IMA_FUNC) && rule->func != func)
106                 return false;
107         if ((rule->flags & IMA_MASK) && rule->mask != mask)
108                 return false;
109         if ((rule->flags & IMA_FSMAGIC)
110             && rule->fsmagic != inode->i_sb->s_magic)
111                 return false;
112         if ((rule->flags & IMA_UID) && rule->uid != cred->uid)
113                 return false;
114         for (i = 0; i < MAX_LSM_RULES; i++) {
115                 int rc = 0;
116                 u32 osid, sid;
117
118                 if (!rule->lsm[i].rule)
119                         continue;
120
121                 switch (i) {
122                 case LSM_OBJ_USER:
123                 case LSM_OBJ_ROLE:
124                 case LSM_OBJ_TYPE:
125                         security_inode_getsecid(inode, &osid);
126                         rc = security_filter_rule_match(osid,
127                                                         rule->lsm[i].type,
128                                                         Audit_equal,
129                                                         rule->lsm[i].rule,
130                                                         NULL);
131                         break;
132                 case LSM_SUBJ_USER:
133                 case LSM_SUBJ_ROLE:
134                 case LSM_SUBJ_TYPE:
135                         security_task_getsecid(tsk, &sid);
136                         rc = security_filter_rule_match(sid,
137                                                         rule->lsm[i].type,
138                                                         Audit_equal,
139                                                         rule->lsm[i].rule,
140                                                         NULL);
141                 default:
142                         break;
143                 }
144                 if (!rc)
145                         return false;
146         }
147         return true;
148 }
149
150 /**
151  * ima_match_policy - decision based on LSM and other conditions
152  * @inode: pointer to an inode for which the policy decision is being made
153  * @func: IMA hook identifier
154  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
155  *
156  * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
157  * conditions.
158  *
159  * (There is no need for locking when walking the policy list,
160  * as elements in the list are never deleted, nor does the list
161  * change.)
162  */
163 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
164 {
165         struct ima_measure_rule_entry *entry;
166
167         list_for_each_entry(entry, ima_measure, list) {
168                 bool rc;
169
170                 rc = ima_match_rules(entry, inode, func, mask);
171                 if (rc)
172                         return entry->action;
173         }
174         return 0;
175 }
176
177 /**
178  * ima_init_policy - initialize the default measure rules.
179  *
180  * ima_measure points to either the measure_default_rules or the
181  * the new measure_policy_rules.
182  */
183 void __init ima_init_policy(void)
184 {
185         int i, entries;
186
187         /* if !ima_use_tcb set entries = 0 so we load NO default rules */
188         if (ima_use_tcb)
189                 entries = ARRAY_SIZE(default_rules);
190         else
191                 entries = 0;
192
193         for (i = 0; i < entries; i++)
194                 list_add_tail(&default_rules[i].list, &measure_default_rules);
195         ima_measure = &measure_default_rules;
196 }
197
198 /**
199  * ima_update_policy - update default_rules with new measure rules
200  *
201  * Called on file .release to update the default rules with a complete new
202  * policy.  Once updated, the policy is locked, no additional rules can be
203  * added to the policy.
204  */
205 void ima_update_policy(void)
206 {
207         const char *op = "policy_update";
208         const char *cause = "already exists";
209         int result = 1;
210         int audit_info = 0;
211
212         if (ima_measure == &measure_default_rules) {
213                 ima_measure = &measure_policy_rules;
214                 cause = "complete";
215                 result = 0;
216         }
217         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
218                             NULL, op, cause, result, audit_info);
219 }
220
221 enum {
222         Opt_err = -1,
223         Opt_measure = 1, Opt_dont_measure,
224         Opt_obj_user, Opt_obj_role, Opt_obj_type,
225         Opt_subj_user, Opt_subj_role, Opt_subj_type,
226         Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
227 };
228
229 static match_table_t policy_tokens = {
230         {Opt_measure, "measure"},
231         {Opt_dont_measure, "dont_measure"},
232         {Opt_obj_user, "obj_user=%s"},
233         {Opt_obj_role, "obj_role=%s"},
234         {Opt_obj_type, "obj_type=%s"},
235         {Opt_subj_user, "subj_user=%s"},
236         {Opt_subj_role, "subj_role=%s"},
237         {Opt_subj_type, "subj_type=%s"},
238         {Opt_func, "func=%s"},
239         {Opt_mask, "mask=%s"},
240         {Opt_fsmagic, "fsmagic=%s"},
241         {Opt_uid, "uid=%s"},
242         {Opt_err, NULL}
243 };
244
245 static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
246                              char *args, int lsm_rule, int audit_type)
247 {
248         int result;
249
250         if (entry->lsm[lsm_rule].rule)
251                 return -EINVAL;
252
253         entry->lsm[lsm_rule].type = audit_type;
254         result = security_filter_rule_init(entry->lsm[lsm_rule].type,
255                                            Audit_equal, args,
256                                            &entry->lsm[lsm_rule].rule);
257         if (!entry->lsm[lsm_rule].rule)
258                 return -EINVAL;
259         return result;
260 }
261
262 static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
263 {
264         audit_log_format(ab, "%s=", key);
265         audit_log_untrustedstring(ab, value);
266         audit_log_format(ab, " ");
267 }
268
269 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
270 {
271         struct audit_buffer *ab;
272         char *p;
273         int result = 0;
274
275         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
276
277         entry->uid = -1;
278         entry->action = UNKNOWN;
279         while ((p = strsep(&rule, " \t")) != NULL) {
280                 substring_t args[MAX_OPT_ARGS];
281                 int token;
282                 unsigned long lnum;
283
284                 if (result < 0)
285                         break;
286                 if ((*p == '\0') || (*p == ' ') || (*p == '\t'))
287                         continue;
288                 token = match_token(p, policy_tokens, args);
289                 switch (token) {
290                 case Opt_measure:
291                         ima_log_string(ab, "action", "measure");
292
293                         if (entry->action != UNKNOWN)
294                                 result = -EINVAL;
295
296                         entry->action = MEASURE;
297                         break;
298                 case Opt_dont_measure:
299                         ima_log_string(ab, "action", "dont_measure");
300
301                         if (entry->action != UNKNOWN)
302                                 result = -EINVAL;
303
304                         entry->action = DONT_MEASURE;
305                         break;
306                 case Opt_func:
307                         ima_log_string(ab, "func", args[0].from);
308
309                         if (entry->func)
310                                 result  = -EINVAL;
311
312                         if (strcmp(args[0].from, "FILE_CHECK") == 0)
313                                 entry->func = FILE_CHECK;
314                         /* PATH_CHECK is for backwards compat */
315                         else if (strcmp(args[0].from, "PATH_CHECK") == 0)
316                                 entry->func = FILE_CHECK;
317                         else if (strcmp(args[0].from, "FILE_MMAP") == 0)
318                                 entry->func = FILE_MMAP;
319                         else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
320                                 entry->func = BPRM_CHECK;
321                         else
322                                 result = -EINVAL;
323                         if (!result)
324                                 entry->flags |= IMA_FUNC;
325                         break;
326                 case Opt_mask:
327                         ima_log_string(ab, "mask", args[0].from);
328
329                         if (entry->mask)
330                                 result = -EINVAL;
331
332                         if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
333                                 entry->mask = MAY_EXEC;
334                         else if (strcmp(args[0].from, "MAY_WRITE") == 0)
335                                 entry->mask = MAY_WRITE;
336                         else if (strcmp(args[0].from, "MAY_READ") == 0)
337                                 entry->mask = MAY_READ;
338                         else if (strcmp(args[0].from, "MAY_APPEND") == 0)
339                                 entry->mask = MAY_APPEND;
340                         else
341                                 result = -EINVAL;
342                         if (!result)
343                                 entry->flags |= IMA_MASK;
344                         break;
345                 case Opt_fsmagic:
346                         ima_log_string(ab, "fsmagic", args[0].from);
347
348                         if (entry->fsmagic) {
349                                 result = -EINVAL;
350                                 break;
351                         }
352
353                         result = strict_strtoul(args[0].from, 16,
354                                                 &entry->fsmagic);
355                         if (!result)
356                                 entry->flags |= IMA_FSMAGIC;
357                         break;
358                 case Opt_uid:
359                         ima_log_string(ab, "uid", args[0].from);
360
361                         if (entry->uid != -1) {
362                                 result = -EINVAL;
363                                 break;
364                         }
365
366                         result = strict_strtoul(args[0].from, 10, &lnum);
367                         if (!result) {
368                                 entry->uid = (uid_t) lnum;
369                                 if (entry->uid != lnum)
370                                         result = -EINVAL;
371                                 else
372                                         entry->flags |= IMA_UID;
373                         }
374                         break;
375                 case Opt_obj_user:
376                         ima_log_string(ab, "obj_user", args[0].from);
377                         result = ima_lsm_rule_init(entry, args[0].from,
378                                                    LSM_OBJ_USER,
379                                                    AUDIT_OBJ_USER);
380                         break;
381                 case Opt_obj_role:
382                         ima_log_string(ab, "obj_role", args[0].from);
383                         result = ima_lsm_rule_init(entry, args[0].from,
384                                                    LSM_OBJ_ROLE,
385                                                    AUDIT_OBJ_ROLE);
386                         break;
387                 case Opt_obj_type:
388                         ima_log_string(ab, "obj_type", args[0].from);
389                         result = ima_lsm_rule_init(entry, args[0].from,
390                                                    LSM_OBJ_TYPE,
391                                                    AUDIT_OBJ_TYPE);
392                         break;
393                 case Opt_subj_user:
394                         ima_log_string(ab, "subj_user", args[0].from);
395                         result = ima_lsm_rule_init(entry, args[0].from,
396                                                    LSM_SUBJ_USER,
397                                                    AUDIT_SUBJ_USER);
398                         break;
399                 case Opt_subj_role:
400                         ima_log_string(ab, "subj_role", args[0].from);
401                         result = ima_lsm_rule_init(entry, args[0].from,
402                                                    LSM_SUBJ_ROLE,
403                                                    AUDIT_SUBJ_ROLE);
404                         break;
405                 case Opt_subj_type:
406                         ima_log_string(ab, "subj_type", args[0].from);
407                         result = ima_lsm_rule_init(entry, args[0].from,
408                                                    LSM_SUBJ_TYPE,
409                                                    AUDIT_SUBJ_TYPE);
410                         break;
411                 case Opt_err:
412                         ima_log_string(ab, "UNKNOWN", p);
413                         result = -EINVAL;
414                         break;
415                 }
416         }
417         if (!result && (entry->action == UNKNOWN))
418                 result = -EINVAL;
419
420         audit_log_format(ab, "res=%d", !!result);
421         audit_log_end(ab);
422         return result;
423 }
424
425 /**
426  * ima_parse_add_rule - add a rule to measure_policy_rules
427  * @rule - ima measurement policy rule
428  *
429  * Uses a mutex to protect the policy list from multiple concurrent writers.
430  * Returns the length of the rule parsed, an error code on failure
431  */
432 ssize_t ima_parse_add_rule(char *rule)
433 {
434         const char *op = "update_policy";
435         char *p;
436         struct ima_measure_rule_entry *entry;
437         ssize_t result, len;
438         int audit_info = 0;
439
440         /* Prevent installed policy from changing */
441         if (ima_measure != &measure_default_rules) {
442                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
443                                     NULL, op, "already exists",
444                                     -EACCES, audit_info);
445                 return -EACCES;
446         }
447
448         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
449         if (!entry) {
450                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
451                                     NULL, op, "-ENOMEM", -ENOMEM, audit_info);
452                 return -ENOMEM;
453         }
454
455         INIT_LIST_HEAD(&entry->list);
456
457         p = strsep(&rule, "\n");
458         len = strlen(p) + 1;
459
460         if (*p == '#') {
461                 kfree(entry);
462                 return len;
463         }
464
465         result = ima_parse_rule(p, entry);
466         if (result) {
467                 kfree(entry);
468                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
469                                     NULL, op, "invalid policy", result,
470                                     audit_info);
471                 return result;
472         }
473
474         mutex_lock(&ima_measure_mutex);
475         list_add_tail(&entry->list, &measure_policy_rules);
476         mutex_unlock(&ima_measure_mutex);
477
478         return len;
479 }
480
481 /* ima_delete_rules called to cleanup invalid policy */
482 void ima_delete_rules(void)
483 {
484         struct ima_measure_rule_entry *entry, *tmp;
485
486         mutex_lock(&ima_measure_mutex);
487         list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
488                 list_del(&entry->list);
489                 kfree(entry);
490         }
491         mutex_unlock(&ima_measure_mutex);
492 }