security/integrity/ima/ima_main.c

   1 /*
   2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   3  *
   4  * Authors:
   5  * Reiner Sailer <sailer@watson.ibm.com>
   6  * Serge Hallyn <serue@us.ibm.com>
   7  * Kylene Hall <kylene@us.ibm.com>
   8  * Mimi Zohar <zohar@us.ibm.com>
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License as
  12  * published by the Free Software Foundation, version 2 of the
  13  * License.
  14  *
  15  * File: ima_main.c
  16  *      implements the IMA hooks: ima_bprm_check, ima_file_mmap,
  17  *      and ima_file_check.
  18  */
  19 #include <linux/module.h>
  20 #include <linux/file.h>
  21 #include <linux/binfmts.h>
  22 #include <linux/mount.h>
  23 #include <linux/mman.h>
  24 #include <linux/slab.h>
  25 #include <linux/xattr.h>
  26 #include <linux/ima.h>
  27 #include <crypto/hash_info.h>
  28
  29 #include "ima.h"
  30
  31 int ima_initialized;
  32
  33 #ifdef CONFIG_IMA_APPRAISE
  34 int ima_appraise = IMA_APPRAISE_ENFORCE;
  35 #else
  36 int ima_appraise;
  37 #endif
  38
  39 int ima_hash_algo = HASH_ALGO_SHA1;
  40 static int hash_setup_done;
  41
  42 static int __init hash_setup(char *str)
  43 {
  44         struct ima_template_desc *template_desc = ima_template_desc_current();
  45         int i;
  46
  47         if (hash_setup_done)
  48                 return 1;
  49
  50         if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
  51                 if (strncmp(str, "sha1", 4) == 0)
  52                         ima_hash_algo = HASH_ALGO_SHA1;
  53                 else if (strncmp(str, "md5", 3) == 0)
  54                         ima_hash_algo = HASH_ALGO_MD5;
  55                 goto out;
  56         }
  57
  58         for (i = 0; i < HASH_ALGO__LAST; i++) {
  59                 if (strcmp(str, hash_algo_name[i]) == 0) {
  60                         ima_hash_algo = i;
  61                         break;
  62                 }
  63         }
  64 out:
  65         hash_setup_done = 1;
  66         return 1;
  67 }
  68 __setup("ima_hash=", hash_setup);
  69
  70 /*
  71  * ima_rdwr_violation_check
  72  *
  73  * Only invalidate the PCR for measured files:
  74  *      - Opening a file for write when already open for read,
  75  *        results in a time of measure, time of use (ToMToU) error.
  76  *      - Opening a file for read when already open for write,
  77  *        could result in a file measurement error.
  78  *
  79  */
  80 static void ima_rdwr_violation_check(struct file *file,
  81                                      struct integrity_iint_cache *iint,
  82                                      int must_measure,
  83                                      char **pathbuf,
  84                                      const char **pathname)
  85 {
  86         struct inode *inode = file_inode(file);
  87         fmode_t mode = file->f_mode;
  88         bool send_tomtou = false, send_writers = false;
  89
  90         if (mode & FMODE_WRITE) {
  91                 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
  92                         if (!iint)
  93                                 iint = integrity_iint_find(inode);
  94                         /* IMA_MEASURE is set from reader side */
  95                         if (iint && (iint->flags & IMA_MEASURE))
  96                                 send_tomtou = true;
  97                 }
  98         } else {
  99                 if ((atomic_read(&inode->i_writecount) > 0) && must_measure)
 100                         send_writers = true;
 101         }
 102
 103         if (!send_tomtou && !send_writers)
 104                 return;
 105
 106         *pathname = ima_d_path(&file->f_path, pathbuf);
 107
 108         if (send_tomtou)
 109                 ima_add_violation(file, *pathname, iint,
 110                                   "invalid_pcr", "ToMToU");
 111         if (send_writers)
 112                 ima_add_violation(file, *pathname, iint,
 113                                   "invalid_pcr", "open_writers");
 114 }
 115
 116 static void ima_check_last_writer(struct integrity_iint_cache *iint,
 117                                   struct inode *inode, struct file *file)
 118 {
 119         fmode_t mode = file->f_mode;
 120
 121         if (!(mode & FMODE_WRITE))
 122                 return;
 123
 124         mutex_lock(&inode->i_mutex);
 125         if (atomic_read(&inode->i_writecount) == 1) {
 126                 if ((iint->version != inode->i_version) ||
 127                     (iint->flags & IMA_NEW_FILE)) {
 128                         iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
 129                         if (iint->flags & IMA_APPRAISE)
 130                                 ima_update_xattr(iint, file);
 131                 }
 132         }
 133         mutex_unlock(&inode->i_mutex);
 134 }
 135
 136 /**
 137  * ima_file_free - called on __fput()
 138  * @file: pointer to file structure being freed
 139  *
 140  * Flag files that changed, based on i_version
 141  */
 142 void ima_file_free(struct file *file)
 143 {
 144         struct inode *inode = file_inode(file);
 145         struct integrity_iint_cache *iint;
 146
 147         if (!ima_policy_flag || !S_ISREG(inode->i_mode))
 148                 return;
 149
 150         iint = integrity_iint_find(inode);
 151         if (!iint)
 152                 return;
 153
 154         ima_check_last_writer(iint, inode, file);
 155 }
 156
 157 static int process_measurement(struct file *file, int mask, int function,
 158                                int opened)
 159 {
 160         struct inode *inode = file_inode(file);
 161         struct integrity_iint_cache *iint = NULL;
 162         struct ima_template_desc *template_desc;
 163         char *pathbuf = NULL;
 164         const char *pathname = NULL;
 165         int rc = -ENOMEM, action, must_appraise;
 166         struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
 167         int xattr_len = 0;
 168         bool violation_check;
 169
 170         if (!ima_policy_flag || !S_ISREG(inode->i_mode))
 171                 return 0;
 172
 173         /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
 174          * bitmask based on the appraise/audit/measurement policy.
 175          * Included is the appraise submask.
 176          */
 177         action = ima_get_action(inode, mask, function);
 178         violation_check = ((function == FILE_CHECK || function == MMAP_CHECK) &&
 179                            (ima_policy_flag & IMA_MEASURE));
 180         if (!action && !violation_check)
 181                 return 0;
 182
 183         must_appraise = action & IMA_APPRAISE;
 184
 185         /*  Is the appraise rule hook specific?  */
 186         if (action & IMA_FILE_APPRAISE)
 187                 function = FILE_CHECK;
 188
 189         mutex_lock(&inode->i_mutex);
 190
 191         if (action) {
 192                 iint = integrity_inode_get(inode);
 193                 if (!iint)
 194                         goto out;
 195         }
 196
 197         if (violation_check) {
 198                 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
 199                                          &pathbuf, &pathname);
 200                 if (!action) {
 201                         rc = 0;
 202                         goto out_free;
 203                 }
 204         }
 205
 206         /* Determine if already appraised/measured based on bitmask
 207          * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
 208          *  IMA_AUDIT, IMA_AUDITED)
 209          */
 210         iint->flags |= action;
 211         action &= IMA_DO_MASK;
 212         action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 213
 214         /* Nothing to do, just return existing appraised status */
 215         if (!action) {
 216                 if (must_appraise)
 217                         rc = ima_get_cache_status(iint, function);
 218                 goto out_digsig;
 219         }
 220
 221         template_desc = ima_template_desc_current();
 222         if ((action & IMA_APPRAISE_SUBMASK) ||
 223                     strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
 224                 xattr_ptr = &xattr_value;
 225
 226         rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
 227         if (rc != 0) {
 228                 if (file->f_flags & O_DIRECT)
 229                         rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
 230                 goto out_digsig;
 231         }
 232
 233         if (!pathname)  /* ima_rdwr_violation possibly pre-fetched */
 234                 pathname = ima_d_path(&file->f_path, &pathbuf);
 235
 236         if (action & IMA_MEASURE)
 237                 ima_store_measurement(iint, file, pathname,
 238                                       xattr_value, xattr_len);
 239         if (action & IMA_APPRAISE_SUBMASK)
 240                 rc = ima_appraise_measurement(function, iint, file, pathname,
 241                                               xattr_value, xattr_len, opened);
 242         if (action & IMA_AUDIT)
 243                 ima_audit_measurement(iint, pathname);
 244
 245 out_digsig:
 246         if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
 247                 rc = -EACCES;
 248         kfree(xattr_value);
 249 out_free:
 250         if (pathbuf)
 251                 __putname(pathbuf);
 252 out:
 253         mutex_unlock(&inode->i_mutex);
 254         if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
 255                 return -EACCES;
 256         return 0;
 257 }
 258
 259 /**
 260  * ima_file_mmap - based on policy, collect/store measurement.
 261  * @file: pointer to the file to be measured (May be NULL)
 262  * @prot: contains the protection that will be applied by the kernel.
 263  *
 264  * Measure files being mmapped executable based on the ima_must_measure()
 265  * policy decision.
 266  *
 267  * On success return 0.  On integrity appraisal error, assuming the file
 268  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 269  */
 270 int ima_file_mmap(struct file *file, unsigned long prot)
 271 {
 272         if (file && (prot & PROT_EXEC))
 273                 return process_measurement(file, MAY_EXEC, MMAP_CHECK, 0);
 274         return 0;
 275 }
 276
 277 /**
 278  * ima_bprm_check - based on policy, collect/store measurement.
 279  * @bprm: contains the linux_binprm structure
 280  *
 281  * The OS protects against an executable file, already open for write,
 282  * from being executed in deny_write_access() and an executable file,
 283  * already open for execute, from being modified in get_write_access().
 284  * So we can be certain that what we verify and measure here is actually
 285  * what is being executed.
 286  *
 287  * On success return 0.  On integrity appraisal error, assuming the file
 288  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 289  */
 290 int ima_bprm_check(struct linux_binprm *bprm)
 291 {
 292         return process_measurement(bprm->file, MAY_EXEC, BPRM_CHECK, 0);
 293 }
 294
 295 /**
 296  * ima_path_check - based on policy, collect/store measurement.
 297  * @file: pointer to the file to be measured
 298  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 299  *
 300  * Measure files based on the ima_must_measure() policy decision.
 301  *
 302  * On success return 0.  On integrity appraisal error, assuming the file
 303  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 304  */
 305 int ima_file_check(struct file *file, int mask, int opened)
 306 {
 307         return process_measurement(file,
 308                                    mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 309                                    FILE_CHECK, opened);
 310 }
 311 EXPORT_SYMBOL_GPL(ima_file_check);
 312
 313 /**
 314  * ima_module_check - based on policy, collect/store/appraise measurement.
 315  * @file: pointer to the file to be measured/appraised
 316  *
 317  * Measure/appraise kernel modules based on policy.
 318  *
 319  * On success return 0.  On integrity appraisal error, assuming the file
 320  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 321  */
 322 int ima_module_check(struct file *file)
 323 {
 324         if (!file) {
 325 #ifndef CONFIG_MODULE_SIG_FORCE
 326                 if ((ima_appraise & IMA_APPRAISE_MODULES) &&
 327                     (ima_appraise & IMA_APPRAISE_ENFORCE))
 328                         return -EACCES; /* INTEGRITY_UNKNOWN */
 329 #endif
 330                 return 0;       /* We rely on module signature checking */
 331         }
 332         return process_measurement(file, MAY_EXEC, MODULE_CHECK, 0);
 333 }
 334
 335 int ima_fw_from_file(struct file *file, char *buf, size_t size)
 336 {
 337         if (!file) {
 338                 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
 339                     (ima_appraise & IMA_APPRAISE_ENFORCE))
 340                         return -EACCES; /* INTEGRITY_UNKNOWN */
 341                 return 0;
 342         }
 343         return process_measurement(file, MAY_EXEC, FIRMWARE_CHECK, 0);
 344 }
 345
 346 static int __init init_ima(void)
 347 {
 348         int error;
 349
 350         hash_setup(CONFIG_IMA_DEFAULT_HASH);
 351         error = ima_init();
 352         if (!error) {
 353                 ima_initialized = 1;
 354                 ima_update_policy_flag();
 355         }
 356         return error;
 357 }
 358
 359 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 360
 361 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 362 MODULE_LICENSE("GPL");