]> git.openfabrics.org - ~shefty/rdma-dev.git/blob - security/integrity/ima/ima_policy.c
aef8c0a923ab8e2276f97e1fe2aa61b7748e25e4
[~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 = 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         return result;
257 }
258
259 static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
260 {
261         audit_log_format(ab, "%s=", key);
262         audit_log_untrustedstring(ab, value);
263         audit_log_format(ab, " ");
264 }
265
266 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
267 {
268         struct audit_buffer *ab;
269         char *p;
270         int result = 0;
271
272         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
273
274         entry->uid = -1;
275         entry->action = UNKNOWN;
276         while ((p = strsep(&rule, " \t")) != NULL) {
277                 substring_t args[MAX_OPT_ARGS];
278                 int token;
279                 unsigned long lnum;
280
281                 if (result < 0)
282                         break;
283                 if ((*p == '\0') || (*p == ' ') || (*p == '\t'))
284                         continue;
285                 token = match_token(p, policy_tokens, args);
286                 switch (token) {
287                 case Opt_measure:
288                         ima_log_string(ab, "action", "measure");
289
290                         if (entry->action != UNKNOWN)
291                                 result = -EINVAL;
292
293                         entry->action = MEASURE;
294                         break;
295                 case Opt_dont_measure:
296                         ima_log_string(ab, "action", "dont_measure");
297
298                         if (entry->action != UNKNOWN)
299                                 result = -EINVAL;
300
301                         entry->action = DONT_MEASURE;
302                         break;
303                 case Opt_func:
304                         ima_log_string(ab, "func", args[0].from);
305
306                         if (entry->func)
307                                 result  = -EINVAL;
308
309                         if (strcmp(args[0].from, "FILE_CHECK") == 0)
310                                 entry->func = FILE_CHECK;
311                         /* PATH_CHECK is for backwards compat */
312                         else if (strcmp(args[0].from, "PATH_CHECK") == 0)
313                                 entry->func = FILE_CHECK;
314                         else if (strcmp(args[0].from, "FILE_MMAP") == 0)
315                                 entry->func = FILE_MMAP;
316                         else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
317                                 entry->func = BPRM_CHECK;
318                         else
319                                 result = -EINVAL;
320                         if (!result)
321                                 entry->flags |= IMA_FUNC;
322                         break;
323                 case Opt_mask:
324                         ima_log_string(ab, "mask", args[0].from);
325
326                         if (entry->mask)
327                                 result = -EINVAL;
328
329                         if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
330                                 entry->mask = MAY_EXEC;
331                         else if (strcmp(args[0].from, "MAY_WRITE") == 0)
332                                 entry->mask = MAY_WRITE;
333                         else if (strcmp(args[0].from, "MAY_READ") == 0)
334                                 entry->mask = MAY_READ;
335                         else if (strcmp(args[0].from, "MAY_APPEND") == 0)
336                                 entry->mask = MAY_APPEND;
337                         else
338                                 result = -EINVAL;
339                         if (!result)
340                                 entry->flags |= IMA_MASK;
341                         break;
342                 case Opt_fsmagic:
343                         ima_log_string(ab, "fsmagic", args[0].from);
344
345                         if (entry->fsmagic) {
346                                 result = -EINVAL;
347                                 break;
348                         }
349
350                         result = strict_strtoul(args[0].from, 16,
351                                                 &entry->fsmagic);
352                         if (!result)
353                                 entry->flags |= IMA_FSMAGIC;
354                         break;
355                 case Opt_uid:
356                         ima_log_string(ab, "uid", args[0].from);
357
358                         if (entry->uid != -1) {
359                                 result = -EINVAL;
360                                 break;
361                         }
362
363                         result = strict_strtoul(args[0].from, 10, &lnum);
364                         if (!result) {
365                                 entry->uid = (uid_t) lnum;
366                                 if (entry->uid != lnum)
367                                         result = -EINVAL;
368                                 else
369                                         entry->flags |= IMA_UID;
370                         }
371                         break;
372                 case Opt_obj_user:
373                         ima_log_string(ab, "obj_user", args[0].from);
374                         result = ima_lsm_rule_init(entry, args[0].from,
375                                                    LSM_OBJ_USER,
376                                                    AUDIT_OBJ_USER);
377                         break;
378                 case Opt_obj_role:
379                         ima_log_string(ab, "obj_role", args[0].from);
380                         result = ima_lsm_rule_init(entry, args[0].from,
381                                                    LSM_OBJ_ROLE,
382                                                    AUDIT_OBJ_ROLE);
383                         break;
384                 case Opt_obj_type:
385                         ima_log_string(ab, "obj_type", args[0].from);
386                         result = ima_lsm_rule_init(entry, args[0].from,
387                                                    LSM_OBJ_TYPE,
388                                                    AUDIT_OBJ_TYPE);
389                         break;
390                 case Opt_subj_user:
391                         ima_log_string(ab, "subj_user", args[0].from);
392                         result = ima_lsm_rule_init(entry, args[0].from,
393                                                    LSM_SUBJ_USER,
394                                                    AUDIT_SUBJ_USER);
395                         break;
396                 case Opt_subj_role:
397                         ima_log_string(ab, "subj_role", args[0].from);
398                         result = ima_lsm_rule_init(entry, args[0].from,
399                                                    LSM_SUBJ_ROLE,
400                                                    AUDIT_SUBJ_ROLE);
401                         break;
402                 case Opt_subj_type:
403                         ima_log_string(ab, "subj_type", args[0].from);
404                         result = ima_lsm_rule_init(entry, args[0].from,
405                                                    LSM_SUBJ_TYPE,
406                                                    AUDIT_SUBJ_TYPE);
407                         break;
408                 case Opt_err:
409                         ima_log_string(ab, "UNKNOWN", p);
410                         result = -EINVAL;
411                         break;
412                 }
413         }
414         if (!result && (entry->action == UNKNOWN))
415                 result = -EINVAL;
416
417         audit_log_format(ab, "res=%d", !!result);
418         audit_log_end(ab);
419         return result;
420 }
421
422 /**
423  * ima_parse_add_rule - add a rule to measure_policy_rules
424  * @rule - ima measurement policy rule
425  *
426  * Uses a mutex to protect the policy list from multiple concurrent writers.
427  * Returns the length of the rule parsed, an error code on failure
428  */
429 ssize_t ima_parse_add_rule(char *rule)
430 {
431         const char *op = "update_policy";
432         char *p;
433         struct ima_measure_rule_entry *entry;
434         ssize_t result, len;
435         int audit_info = 0;
436
437         /* Prevent installed policy from changing */
438         if (ima_measure != &measure_default_rules) {
439                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
440                                     NULL, op, "already exists",
441                                     -EACCES, audit_info);
442                 return -EACCES;
443         }
444
445         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
446         if (!entry) {
447                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
448                                     NULL, op, "-ENOMEM", -ENOMEM, audit_info);
449                 return -ENOMEM;
450         }
451
452         INIT_LIST_HEAD(&entry->list);
453
454         p = strsep(&rule, "\n");
455         len = strlen(p) + 1;
456
457         if (*p == '#') {
458                 kfree(entry);
459                 return len;
460         }
461
462         result = ima_parse_rule(p, entry);
463         if (result) {
464                 kfree(entry);
465                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
466                                     NULL, op, "invalid policy", result,
467                                     audit_info);
468                 return result;
469         }
470
471         mutex_lock(&ima_measure_mutex);
472         list_add_tail(&entry->list, &measure_policy_rules);
473         mutex_unlock(&ima_measure_mutex);
474
475         return len;
476 }
477
478 /* ima_delete_rules called to cleanup invalid policy */
479 void ima_delete_rules(void)
480 {
481         struct ima_measure_rule_entry *entry, *tmp;
482
483         mutex_lock(&ima_measure_mutex);
484         list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
485                 list_del(&entry->list);
486                 kfree(entry);
487         }
488         mutex_unlock(&ima_measure_mutex);
489 }