Merge branch 'next-queue' into next
[~shefty/rdma-dev.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 = RAMFS_MAGIC,.flags = IMA_FSMAGIC},
66         {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC},
67         {.action = DONT_MEASURE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC},
68         {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC,
69          .flags = IMA_FUNC | IMA_MASK},
70         {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC,
71          .flags = IMA_FUNC | IMA_MASK},
72         {.action = MEASURE,.func = FILE_CHECK,.mask = MAY_READ,.uid = 0,
73          .flags = IMA_FUNC | IMA_MASK | IMA_UID},
74 };
75
76 static LIST_HEAD(measure_default_rules);
77 static LIST_HEAD(measure_policy_rules);
78 static struct list_head *ima_measure;
79
80 static DEFINE_MUTEX(ima_measure_mutex);
81
82 static bool ima_use_tcb __initdata;
83 static int __init default_policy_setup(char *str)
84 {
85         ima_use_tcb = 1;
86         return 1;
87 }
88 __setup("ima_tcb", default_policy_setup);
89
90 /**
91  * ima_match_rules - determine whether an inode matches the measure rule.
92  * @rule: a pointer to a rule
93  * @inode: a pointer to an inode
94  * @func: LIM hook identifier
95  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
96  *
97  * Returns true on rule match, false on failure.
98  */
99 static bool ima_match_rules(struct ima_measure_rule_entry *rule,
100                             struct inode *inode, enum ima_hooks func, int mask)
101 {
102         struct task_struct *tsk = current;
103         const struct cred *cred = current_cred();
104         int i;
105
106         if ((rule->flags & IMA_FUNC) && rule->func != func)
107                 return false;
108         if ((rule->flags & IMA_MASK) && rule->mask != mask)
109                 return false;
110         if ((rule->flags & IMA_FSMAGIC)
111             && rule->fsmagic != inode->i_sb->s_magic)
112                 return false;
113         if ((rule->flags & IMA_UID) && rule->uid != cred->uid)
114                 return false;
115         for (i = 0; i < MAX_LSM_RULES; i++) {
116                 int rc = 0;
117                 u32 osid, sid;
118
119                 if (!rule->lsm[i].rule)
120                         continue;
121
122                 switch (i) {
123                 case LSM_OBJ_USER:
124                 case LSM_OBJ_ROLE:
125                 case LSM_OBJ_TYPE:
126                         security_inode_getsecid(inode, &osid);
127                         rc = security_filter_rule_match(osid,
128                                                         rule->lsm[i].type,
129                                                         Audit_equal,
130                                                         rule->lsm[i].rule,
131                                                         NULL);
132                         break;
133                 case LSM_SUBJ_USER:
134                 case LSM_SUBJ_ROLE:
135                 case LSM_SUBJ_TYPE:
136                         security_task_getsecid(tsk, &sid);
137                         rc = security_filter_rule_match(sid,
138                                                         rule->lsm[i].type,
139                                                         Audit_equal,
140                                                         rule->lsm[i].rule,
141                                                         NULL);
142                 default:
143                         break;
144                 }
145                 if (!rc)
146                         return false;
147         }
148         return true;
149 }
150
151 /**
152  * ima_match_policy - decision based on LSM and other conditions
153  * @inode: pointer to an inode for which the policy decision is being made
154  * @func: IMA hook identifier
155  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
156  *
157  * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
158  * conditions.
159  *
160  * (There is no need for locking when walking the policy list,
161  * as elements in the list are never deleted, nor does the list
162  * change.)
163  */
164 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
165 {
166         struct ima_measure_rule_entry *entry;
167
168         list_for_each_entry(entry, ima_measure, list) {
169                 bool rc;
170
171                 rc = ima_match_rules(entry, inode, func, mask);
172                 if (rc)
173                         return entry->action;
174         }
175         return 0;
176 }
177
178 /**
179  * ima_init_policy - initialize the default measure rules.
180  *
181  * ima_measure points to either the measure_default_rules or the
182  * the new measure_policy_rules.
183  */
184 void __init ima_init_policy(void)
185 {
186         int i, entries;
187
188         /* if !ima_use_tcb set entries = 0 so we load NO default rules */
189         if (ima_use_tcb)
190                 entries = ARRAY_SIZE(default_rules);
191         else
192                 entries = 0;
193
194         for (i = 0; i < entries; i++)
195                 list_add_tail(&default_rules[i].list, &measure_default_rules);
196         ima_measure = &measure_default_rules;
197 }
198
199 /**
200  * ima_update_policy - update default_rules with new measure rules
201  *
202  * Called on file .release to update the default rules with a complete new
203  * policy.  Once updated, the policy is locked, no additional rules can be
204  * added to the policy.
205  */
206 void ima_update_policy(void)
207 {
208         const char *op = "policy_update";
209         const char *cause = "already exists";
210         int result = 1;
211         int audit_info = 0;
212
213         if (ima_measure == &measure_default_rules) {
214                 ima_measure = &measure_policy_rules;
215                 cause = "complete";
216                 result = 0;
217         }
218         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
219                             NULL, op, cause, result, audit_info);
220 }
221
222 enum {
223         Opt_err = -1,
224         Opt_measure = 1, Opt_dont_measure,
225         Opt_obj_user, Opt_obj_role, Opt_obj_type,
226         Opt_subj_user, Opt_subj_role, Opt_subj_type,
227         Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
228 };
229
230 static match_table_t policy_tokens = {
231         {Opt_measure, "measure"},
232         {Opt_dont_measure, "dont_measure"},
233         {Opt_obj_user, "obj_user=%s"},
234         {Opt_obj_role, "obj_role=%s"},
235         {Opt_obj_type, "obj_type=%s"},
236         {Opt_subj_user, "subj_user=%s"},
237         {Opt_subj_role, "subj_role=%s"},
238         {Opt_subj_type, "subj_type=%s"},
239         {Opt_func, "func=%s"},
240         {Opt_mask, "mask=%s"},
241         {Opt_fsmagic, "fsmagic=%s"},
242         {Opt_uid, "uid=%s"},
243         {Opt_err, NULL}
244 };
245
246 static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
247                              char *args, int lsm_rule, int audit_type)
248 {
249         int result;
250
251         if (entry->lsm[lsm_rule].rule)
252                 return -EINVAL;
253
254         entry->lsm[lsm_rule].type = audit_type;
255         result = security_filter_rule_init(entry->lsm[lsm_rule].type,
256                                            Audit_equal, args,
257                                            &entry->lsm[lsm_rule].rule);
258         if (!entry->lsm[lsm_rule].rule)
259                 return -EINVAL;
260         return result;
261 }
262
263 static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
264 {
265         audit_log_format(ab, "%s=", key);
266         audit_log_untrustedstring(ab, value);
267         audit_log_format(ab, " ");
268 }
269
270 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
271 {
272         struct audit_buffer *ab;
273         char *p;
274         int result = 0;
275
276         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
277
278         entry->uid = -1;
279         entry->action = UNKNOWN;
280         while ((p = strsep(&rule, " \t")) != NULL) {
281                 substring_t args[MAX_OPT_ARGS];
282                 int token;
283                 unsigned long lnum;
284
285                 if (result < 0)
286                         break;
287                 if ((*p == '\0') || (*p == ' ') || (*p == '\t'))
288                         continue;
289                 token = match_token(p, policy_tokens, args);
290                 switch (token) {
291                 case Opt_measure:
292                         ima_log_string(ab, "action", "measure");
293
294                         if (entry->action != UNKNOWN)
295                                 result = -EINVAL;
296
297                         entry->action = MEASURE;
298                         break;
299                 case Opt_dont_measure:
300                         ima_log_string(ab, "action", "dont_measure");
301
302                         if (entry->action != UNKNOWN)
303                                 result = -EINVAL;
304
305                         entry->action = DONT_MEASURE;
306                         break;
307                 case Opt_func:
308                         ima_log_string(ab, "func", args[0].from);
309
310                         if (entry->func)
311                                 result  = -EINVAL;
312
313                         if (strcmp(args[0].from, "FILE_CHECK") == 0)
314                                 entry->func = FILE_CHECK;
315                         /* PATH_CHECK is for backwards compat */
316                         else if (strcmp(args[0].from, "PATH_CHECK") == 0)
317                                 entry->func = FILE_CHECK;
318                         else if (strcmp(args[0].from, "FILE_MMAP") == 0)
319                                 entry->func = FILE_MMAP;
320                         else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
321                                 entry->func = BPRM_CHECK;
322                         else
323                                 result = -EINVAL;
324                         if (!result)
325                                 entry->flags |= IMA_FUNC;
326                         break;
327                 case Opt_mask:
328                         ima_log_string(ab, "mask", args[0].from);
329
330                         if (entry->mask)
331                                 result = -EINVAL;
332
333                         if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
334                                 entry->mask = MAY_EXEC;
335                         else if (strcmp(args[0].from, "MAY_WRITE") == 0)
336                                 entry->mask = MAY_WRITE;
337                         else if (strcmp(args[0].from, "MAY_READ") == 0)
338                                 entry->mask = MAY_READ;
339                         else if (strcmp(args[0].from, "MAY_APPEND") == 0)
340                                 entry->mask = MAY_APPEND;
341                         else
342                                 result = -EINVAL;
343                         if (!result)
344                                 entry->flags |= IMA_MASK;
345                         break;
346                 case Opt_fsmagic:
347                         ima_log_string(ab, "fsmagic", args[0].from);
348
349                         if (entry->fsmagic) {
350                                 result = -EINVAL;
351                                 break;
352                         }
353
354                         result = strict_strtoul(args[0].from, 16,
355                                                 &entry->fsmagic);
356                         if (!result)
357                                 entry->flags |= IMA_FSMAGIC;
358                         break;
359                 case Opt_uid:
360                         ima_log_string(ab, "uid", args[0].from);
361
362                         if (entry->uid != -1) {
363                                 result = -EINVAL;
364                                 break;
365                         }
366
367                         result = strict_strtoul(args[0].from, 10, &lnum);
368                         if (!result) {
369                                 entry->uid = (uid_t) lnum;
370                                 if (entry->uid != lnum)
371                                         result = -EINVAL;
372                                 else
373                                         entry->flags |= IMA_UID;
374                         }
375                         break;
376                 case Opt_obj_user:
377                         ima_log_string(ab, "obj_user", args[0].from);
378                         result = ima_lsm_rule_init(entry, args[0].from,
379                                                    LSM_OBJ_USER,
380                                                    AUDIT_OBJ_USER);
381                         break;
382                 case Opt_obj_role:
383                         ima_log_string(ab, "obj_role", args[0].from);
384                         result = ima_lsm_rule_init(entry, args[0].from,
385                                                    LSM_OBJ_ROLE,
386                                                    AUDIT_OBJ_ROLE);
387                         break;
388                 case Opt_obj_type:
389                         ima_log_string(ab, "obj_type", args[0].from);
390                         result = ima_lsm_rule_init(entry, args[0].from,
391                                                    LSM_OBJ_TYPE,
392                                                    AUDIT_OBJ_TYPE);
393                         break;
394                 case Opt_subj_user:
395                         ima_log_string(ab, "subj_user", args[0].from);
396                         result = ima_lsm_rule_init(entry, args[0].from,
397                                                    LSM_SUBJ_USER,
398                                                    AUDIT_SUBJ_USER);
399                         break;
400                 case Opt_subj_role:
401                         ima_log_string(ab, "subj_role", args[0].from);
402                         result = ima_lsm_rule_init(entry, args[0].from,
403                                                    LSM_SUBJ_ROLE,
404                                                    AUDIT_SUBJ_ROLE);
405                         break;
406                 case Opt_subj_type:
407                         ima_log_string(ab, "subj_type", args[0].from);
408                         result = ima_lsm_rule_init(entry, args[0].from,
409                                                    LSM_SUBJ_TYPE,
410                                                    AUDIT_SUBJ_TYPE);
411                         break;
412                 case Opt_err:
413                         ima_log_string(ab, "UNKNOWN", p);
414                         result = -EINVAL;
415                         break;
416                 }
417         }
418         if (!result && (entry->action == UNKNOWN))
419                 result = -EINVAL;
420
421         audit_log_format(ab, "res=%d", !!result);
422         audit_log_end(ab);
423         return result;
424 }
425
426 /**
427  * ima_parse_add_rule - add a rule to measure_policy_rules
428  * @rule - ima measurement policy rule
429  *
430  * Uses a mutex to protect the policy list from multiple concurrent writers.
431  * Returns the length of the rule parsed, an error code on failure
432  */
433 ssize_t ima_parse_add_rule(char *rule)
434 {
435         const char *op = "update_policy";
436         char *p;
437         struct ima_measure_rule_entry *entry;
438         ssize_t result, len;
439         int audit_info = 0;
440
441         /* Prevent installed policy from changing */
442         if (ima_measure != &measure_default_rules) {
443                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
444                                     NULL, op, "already exists",
445                                     -EACCES, audit_info);
446                 return -EACCES;
447         }
448
449         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
450         if (!entry) {
451                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
452                                     NULL, op, "-ENOMEM", -ENOMEM, audit_info);
453                 return -ENOMEM;
454         }
455
456         INIT_LIST_HEAD(&entry->list);
457
458         p = strsep(&rule, "\n");
459         len = strlen(p) + 1;
460
461         if (*p == '#') {
462                 kfree(entry);
463                 return len;
464         }
465
466         result = ima_parse_rule(p, entry);
467         if (result) {
468                 kfree(entry);
469                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
470                                     NULL, op, "invalid policy", result,
471                                     audit_info);
472                 return result;
473         }
474
475         mutex_lock(&ima_measure_mutex);
476         list_add_tail(&entry->list, &measure_policy_rules);
477         mutex_unlock(&ima_measure_mutex);
478
479         return len;
480 }
481
482 /* ima_delete_rules called to cleanup invalid policy */
483 void ima_delete_rules(void)
484 {
485         struct ima_measure_rule_entry *entry, *tmp;
486
487         mutex_lock(&ima_measure_mutex);
488         list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
489                 list_del(&entry->list);
490                 kfree(entry);
491         }
492         mutex_unlock(&ima_measure_mutex);
493 }