SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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
  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
  27 enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE };
  28
  29 #define MAX_LSM_RULES 6
  30 enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
  31         LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE
  32 };
  33
  34 struct 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  */
  51 static 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 };
  65
  66 static LIST_HEAD(measure_default_rules);
  67 static LIST_HEAD(measure_policy_rules);
  68 static struct list_head *ima_measure;
  69
  70 static DEFINE_MUTEX(ima_measure_mutex);
  71
  72 /**
  73  * ima_match_rules - determine whether an inode matches the measure rule.
  74  * @rule: a pointer to a rule
  75  * @inode: a pointer to an inode
  76  * @func: LIM hook identifier
  77  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
  78  *
  79  * Returns true on rule match, false on failure.
  80  */
  81 static bool ima_match_rules(struct ima_measure_rule_entry *rule,
  82                             struct inode *inode, enum ima_hooks func, int mask)
  83 {
  84         struct task_struct *tsk = current;
  85         int i;
  86
  87         if ((rule->flags & IMA_FUNC) && rule->func != func)
  88                 return false;
  89         if ((rule->flags & IMA_MASK) && rule->mask != mask)
  90                 return false;
  91         if ((rule->flags & IMA_FSMAGIC)
  92             && rule->fsmagic != inode->i_sb->s_magic)
  93                 return false;
  94         if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid)
  95                 return false;
  96         for (i = 0; i < MAX_LSM_RULES; i++) {
  97                 int rc = 0;
  98                 u32 osid, sid;
  99
 100                 if (!rule->lsm[i].rule)
 101                         continue;
 102
 103                 switch (i) {
 104                 case LSM_OBJ_USER:
 105                 case LSM_OBJ_ROLE:
 106                 case LSM_OBJ_TYPE:
 107                         security_inode_getsecid(inode, &osid);
 108                         rc = security_filter_rule_match(osid,
 109                                                         rule->lsm[i].type,
 110                                                         Audit_equal,
 111                                                         rule->lsm[i].rule,
 112                                                         NULL);
 113                         break;
 114                 case LSM_SUBJ_USER:
 115                 case LSM_SUBJ_ROLE:
 116                 case LSM_SUBJ_TYPE:
 117                         security_task_getsecid(tsk, &sid);
 118                         rc = security_filter_rule_match(sid,
 119                                                         rule->lsm[i].type,
 120                                                         Audit_equal,
 121                                                         rule->lsm[i].rule,
 122                                                         NULL);
 123                 default:
 124                         break;
 125                 }
 126                 if (!rc)
 127                         return false;
 128         }
 129         return true;
 130 }
 131
 132 /**
 133  * ima_match_policy - decision based on LSM and other conditions
 134  * @inode: pointer to an inode for which the policy decision is being made
 135  * @func: IMA hook identifier
 136  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
 137  *
 138  * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
 139  * conditions.
 140  *
 141  * (There is no need for locking when walking the policy list,
 142  * as elements in the list are never deleted, nor does the list
 143  * change.)
 144  */
 145 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask)
 146 {
 147         struct ima_measure_rule_entry *entry;
 148
 149         list_for_each_entry(entry, ima_measure, list) {
 150                 bool rc;
 151
 152                 rc = ima_match_rules(entry, inode, func, mask);
 153                 if (rc)
 154                         return entry->action;
 155         }
 156         return 0;
 157 }
 158
 159 /**
 160  * ima_init_policy - initialize the default measure rules.
 161  *
 162  * ima_measure points to either the measure_default_rules or the
 163  * the new measure_policy_rules.
 164  */
 165 void ima_init_policy(void)
 166 {
 167         int i;
 168
 169         for (i = 0; i < ARRAY_SIZE(default_rules); i++)
 170                 list_add_tail(&default_rules[i].list, &measure_default_rules);
 171         ima_measure = &measure_default_rules;
 172 }
 173
 174 /**
 175  * ima_update_policy - update default_rules with new measure rules
 176  *
 177  * Called on file .release to update the default rules with a complete new
 178  * policy.  Once updated, the policy is locked, no additional rules can be
 179  * added to the policy.
 180  */
 181 void ima_update_policy(void)
 182 {
 183         const char *op = "policy_update";
 184         const char *cause = "already exists";
 185         int result = 1;
 186         int audit_info = 0;
 187
 188         if (ima_measure == &measure_default_rules) {
 189                 ima_measure = &measure_policy_rules;
 190                 cause = "complete";
 191                 result = 0;
 192         }
 193         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
 194                             NULL, op, cause, result, audit_info);
 195 }
 196
 197 enum {
 198         Opt_err = -1,
 199         Opt_measure = 1, Opt_dont_measure,
 200         Opt_obj_user, Opt_obj_role, Opt_obj_type,
 201         Opt_subj_user, Opt_subj_role, Opt_subj_type,
 202         Opt_func, Opt_mask, Opt_fsmagic, Opt_uid
 203 };
 204
 205 static match_table_t policy_tokens = {
 206         {Opt_measure, "measure"},
 207         {Opt_dont_measure, "dont_measure"},
 208         {Opt_obj_user, "obj_user=%s"},
 209         {Opt_obj_role, "obj_role=%s"},
 210         {Opt_obj_type, "obj_type=%s"},
 211         {Opt_subj_user, "subj_user=%s"},
 212         {Opt_subj_role, "subj_role=%s"},
 213         {Opt_subj_type, "subj_type=%s"},
 214         {Opt_func, "func=%s"},
 215         {Opt_mask, "mask=%s"},
 216         {Opt_fsmagic, "fsmagic=%s"},
 217         {Opt_uid, "uid=%s"},
 218         {Opt_err, NULL}
 219 };
 220
 221 static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry,
 222                              char *args, int lsm_rule, int audit_type)
 223 {
 224         int result;
 225
 226         entry->lsm[lsm_rule].type = audit_type;
 227         result = security_filter_rule_init(entry->lsm[lsm_rule].type,
 228                                            Audit_equal, args,
 229                                            &entry->lsm[lsm_rule].rule);
 230         return result;
 231 }
 232
 233 static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry)
 234 {
 235         struct audit_buffer *ab;
 236         char *p;
 237         int result = 0;
 238
 239         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
 240
 241         entry->action = -1;
 242         while ((p = strsep(&rule, " \n")) != NULL) {
 243                 substring_t args[MAX_OPT_ARGS];
 244                 int token;
 245                 unsigned long lnum;
 246
 247                 if (result < 0)
 248                         break;
 249                 if (!*p)
 250                         continue;
 251                 token = match_token(p, policy_tokens, args);
 252                 switch (token) {
 253                 case Opt_measure:
 254                         audit_log_format(ab, "%s ", "measure");
 255                         entry->action = MEASURE;
 256                         break;
 257                 case Opt_dont_measure:
 258                         audit_log_format(ab, "%s ", "dont_measure");
 259                         entry->action = DONT_MEASURE;
 260                         break;
 261                 case Opt_func:
 262                         audit_log_format(ab, "func=%s ", args[0].from);
 263                         if (strcmp(args[0].from, "PATH_CHECK") == 0)
 264                                 entry->func = PATH_CHECK;
 265                         else if (strcmp(args[0].from, "FILE_MMAP") == 0)
 266                                 entry->func = FILE_MMAP;
 267                         else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
 268                                 entry->func = BPRM_CHECK;
 269                         else
 270                                 result = -EINVAL;
 271                         if (!result)
 272                                 entry->flags |= IMA_FUNC;
 273                         break;
 274                 case Opt_mask:
 275                         audit_log_format(ab, "mask=%s ", args[0].from);
 276                         if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
 277                                 entry->mask = MAY_EXEC;
 278                         else if (strcmp(args[0].from, "MAY_WRITE") == 0)
 279                                 entry->mask = MAY_WRITE;
 280                         else if (strcmp(args[0].from, "MAY_READ") == 0)
 281                                 entry->mask = MAY_READ;
 282                         else if (strcmp(args[0].from, "MAY_APPEND") == 0)
 283                                 entry->mask = MAY_APPEND;
 284                         else
 285                                 result = -EINVAL;
 286                         if (!result)
 287                                 entry->flags |= IMA_MASK;
 288                         break;
 289                 case Opt_fsmagic:
 290                         audit_log_format(ab, "fsmagic=%s ", args[0].from);
 291                         result = strict_strtoul(args[0].from, 16,
 292                                                 &entry->fsmagic);
 293                         if (!result)
 294                                 entry->flags |= IMA_FSMAGIC;
 295                         break;
 296                 case Opt_uid:
 297                         audit_log_format(ab, "uid=%s ", args[0].from);
 298                         result = strict_strtoul(args[0].from, 10, &lnum);
 299                         if (!result) {
 300                                 entry->uid = (uid_t) lnum;
 301                                 if (entry->uid != lnum)
 302                                         result = -EINVAL;
 303                                 else
 304                                         entry->flags |= IMA_UID;
 305                         }
 306                         break;
 307                 case Opt_obj_user:
 308                         audit_log_format(ab, "obj_user=%s ", args[0].from);
 309                         result = ima_lsm_rule_init(entry, args[0].from,
 310                                                    LSM_OBJ_USER,
 311                                                    AUDIT_OBJ_USER);
 312                         break;
 313                 case Opt_obj_role:
 314                         audit_log_format(ab, "obj_role=%s ", args[0].from);
 315                         result = ima_lsm_rule_init(entry, args[0].from,
 316                                                    LSM_OBJ_ROLE,
 317                                                    AUDIT_OBJ_ROLE);
 318                         break;
 319                 case Opt_obj_type:
 320                         audit_log_format(ab, "obj_type=%s ", args[0].from);
 321                         result = ima_lsm_rule_init(entry, args[0].from,
 322                                                    LSM_OBJ_TYPE,
 323                                                    AUDIT_OBJ_TYPE);
 324                         break;
 325                 case Opt_subj_user:
 326                         audit_log_format(ab, "subj_user=%s ", args[0].from);
 327                         result = ima_lsm_rule_init(entry, args[0].from,
 328                                                    LSM_SUBJ_USER,
 329                                                    AUDIT_SUBJ_USER);
 330                         break;
 331                 case Opt_subj_role:
 332                         audit_log_format(ab, "subj_role=%s ", args[0].from);
 333                         result = ima_lsm_rule_init(entry, args[0].from,
 334                                                    LSM_SUBJ_ROLE,
 335                                                    AUDIT_SUBJ_ROLE);
 336                         break;
 337                 case Opt_subj_type:
 338                         audit_log_format(ab, "subj_type=%s ", args[0].from);
 339                         result = ima_lsm_rule_init(entry, args[0].from,
 340                                                    LSM_SUBJ_TYPE,
 341                                                    AUDIT_SUBJ_TYPE);
 342                         break;
 343                 case Opt_err:
 344                         audit_log_format(ab, "UNKNOWN=%s ", p);
 345                         break;
 346                 }
 347         }
 348         if (entry->action == UNKNOWN)
 349                 result = -EINVAL;
 350
 351         audit_log_format(ab, "res=%d", !result ? 0 : 1);
 352         audit_log_end(ab);
 353         return result;
 354 }
 355
 356 /**
 357  * ima_parse_add_rule - add a rule to measure_policy_rules
 358  * @rule - ima measurement policy rule
 359  *
 360  * Uses a mutex to protect the policy list from multiple concurrent writers.
 361  * Returns 0 on success, an error code on failure.
 362  */
 363 int ima_parse_add_rule(char *rule)
 364 {
 365         const char *op = "update_policy";
 366         struct ima_measure_rule_entry *entry;
 367         int result = 0;
 368         int audit_info = 0;
 369
 370         /* Prevent installed policy from changing */
 371         if (ima_measure != &measure_default_rules) {
 372                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
 373                                     NULL, op, "already exists",
 374                                     -EACCES, audit_info);
 375                 return -EACCES;
 376         }
 377
 378         entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 379         if (!entry) {
 380                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
 381                                     NULL, op, "-ENOMEM", -ENOMEM, audit_info);
 382                 return -ENOMEM;
 383         }
 384
 385         INIT_LIST_HEAD(&entry->list);
 386
 387         result = ima_parse_rule(rule, entry);
 388         if (!result) {
 389                 mutex_lock(&ima_measure_mutex);
 390                 list_add_tail(&entry->list, &measure_policy_rules);
 391                 mutex_unlock(&ima_measure_mutex);
 392         } else {
 393                 kfree(entry);
 394                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL,
 395                                     NULL, op, "invalid policy", result,
 396                                     audit_info);
 397         }
 398         return result;
 399 }
 400
 401 /* ima_delete_rules called to cleanup invalid policy */
 402 void ima_delete_rules(void)
 403 {
 404         struct ima_measure_rule_entry *entry, *tmp;
 405
 406         mutex_lock(&ima_measure_mutex);
 407         list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) {
 408                 list_del(&entry->list);
 409                 kfree(entry);
 410         }
 411         mutex_unlock(&ima_measure_mutex);
 412 }