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, "invalid_pcr", "ToMToU");
 110         if (send_writers)
 111                 ima_add_violation(file, *pathname,
 112                                   "invalid_pcr", "open_writers");
 113 }
 114
 115 static void ima_check_last_writer(struct integrity_iint_cache *iint,
 116                                   struct inode *inode, struct file *file)
 117 {
 118         fmode_t mode = file->f_mode;
 119
 120         if (!(mode & FMODE_WRITE))
 121                 return;
 122
 123         mutex_lock(&inode->i_mutex);
 124         if (atomic_read(&inode->i_writecount) == 1) {
 125                 if ((iint->version != inode->i_version) ||
 126                     (iint->flags & IMA_NEW_FILE)) {
 127                         iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
 128                         if (iint->flags & IMA_APPRAISE)
 129                                 ima_update_xattr(iint, file);
 130                 }
 131         }
 132         mutex_unlock(&inode->i_mutex);
 133 }
 134
 135 /**
 136  * ima_file_free - called on __fput()
 137  * @file: pointer to file structure being freed
 138  *
 139  * Flag files that changed, based on i_version
 140  */
 141 void ima_file_free(struct file *file)
 142 {
 143         struct inode *inode = file_inode(file);
 144         struct integrity_iint_cache *iint;
 145
 146         if (!ima_policy_flag || !S_ISREG(inode->i_mode))
 147                 return;
 148
 149         iint = integrity_iint_find(inode);
 150         if (!iint)
 151                 return;
 152
 153         ima_check_last_writer(iint, inode, file);
 154 }
 155
 156 static int process_measurement(struct file *file, int mask, int function,
 157                                int opened)
 158 {
 159         struct inode *inode = file_inode(file);
 160         struct integrity_iint_cache *iint = NULL;
 161         struct ima_template_desc *template_desc;
 162         char *pathbuf = NULL;
 163         const char *pathname = NULL;
 164         int rc = -ENOMEM, action, must_appraise;
 165         struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
 166         int xattr_len = 0;
 167         bool violation_check;
 168
 169         if (!ima_policy_flag || !S_ISREG(inode->i_mode))
 170                 return 0;
 171
 172         /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
 173          * bitmask based on the appraise/audit/measurement policy.
 174          * Included is the appraise submask.
 175          */
 176         action = ima_get_action(inode, mask, function);
 177         violation_check = ((function == FILE_CHECK || function == MMAP_CHECK) &&
 178                            (ima_policy_flag & IMA_MEASURE));
 179         if (!action && !violation_check)
 180                 return 0;
 181
 182         must_appraise = action & IMA_APPRAISE;
 183
 184         /*  Is the appraise rule hook specific?  */
 185         if (action & IMA_FILE_APPRAISE)
 186                 function = FILE_CHECK;
 187
 188         mutex_lock(&inode->i_mutex);
 189
 190         if (action) {
 191                 iint = integrity_inode_get(inode);
 192                 if (!iint)
 193                         goto out;
 194         }
 195
 196         if (violation_check) {
 197                 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
 198                                          &pathbuf, &pathname);
 199                 if (!action) {
 200                         rc = 0;
 201                         goto out_free;
 202                 }
 203         }
 204
 205         /* Determine if already appraised/measured based on bitmask
 206          * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
 207          *  IMA_AUDIT, IMA_AUDITED)
 208          */
 209         iint->flags |= action;
 210         action &= IMA_DO_MASK;
 211         action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 212
 213         /* Nothing to do, just return existing appraised status */
 214         if (!action) {
 215                 if (must_appraise)
 216                         rc = ima_get_cache_status(iint, function);
 217                 goto out_digsig;
 218         }
 219
 220         template_desc = ima_template_desc_current();
 221         if ((action & IMA_APPRAISE_SUBMASK) ||
 222                     strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
 223                 xattr_ptr = &xattr_value;
 224
 225         rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
 226         if (rc != 0) {
 227                 if (file->f_flags & O_DIRECT)
 228                         rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
 229                 goto out_digsig;
 230         }
 231
 232         if (!pathname)  /* ima_rdwr_violation possibly pre-fetched */
 233                 pathname = ima_d_path(&file->f_path, &pathbuf);
 234
 235         if (action & IMA_MEASURE)
 236                 ima_store_measurement(iint, file, pathname,
 237                                       xattr_value, xattr_len);
 238         if (action & IMA_APPRAISE_SUBMASK)
 239                 rc = ima_appraise_measurement(function, iint, file, pathname,
 240                                               xattr_value, xattr_len, opened);
 241         if (action & IMA_AUDIT)
 242                 ima_audit_measurement(iint, pathname);
 243
 244 out_digsig:
 245         if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
 246                 rc = -EACCES;
 247         kfree(xattr_value);
 248 out_free:
 249         if (pathbuf)
 250                 __putname(pathbuf);
 251 out:
 252         mutex_unlock(&inode->i_mutex);
 253         if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
 254                 return -EACCES;
 255         return 0;
 256 }
 257
 258 /**
 259  * ima_file_mmap - based on policy, collect/store measurement.
 260  * @file: pointer to the file to be measured (May be NULL)
 261  * @prot: contains the protection that will be applied by the kernel.
 262  *
 263  * Measure files being mmapped executable based on the ima_must_measure()
 264  * policy decision.
 265  *
 266  * On success return 0.  On integrity appraisal error, assuming the file
 267  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 268  */
 269 int ima_file_mmap(struct file *file, unsigned long prot)
 270 {
 271         if (file && (prot & PROT_EXEC))
 272                 return process_measurement(file, MAY_EXEC, MMAP_CHECK, 0);
 273         return 0;
 274 }
 275
 276 /**
 277  * ima_bprm_check - based on policy, collect/store measurement.
 278  * @bprm: contains the linux_binprm structure
 279  *
 280  * The OS protects against an executable file, already open for write,
 281  * from being executed in deny_write_access() and an executable file,
 282  * already open for execute, from being modified in get_write_access().
 283  * So we can be certain that what we verify and measure here is actually
 284  * what is being executed.
 285  *
 286  * On success return 0.  On integrity appraisal error, assuming the file
 287  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 288  */
 289 int ima_bprm_check(struct linux_binprm *bprm)
 290 {
 291         return process_measurement(bprm->file, MAY_EXEC, BPRM_CHECK, 0);
 292 }
 293
 294 /**
 295  * ima_path_check - based on policy, collect/store measurement.
 296  * @file: pointer to the file to be measured
 297  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 298  *
 299  * Measure files based on the ima_must_measure() policy decision.
 300  *
 301  * On success return 0.  On integrity appraisal error, assuming the file
 302  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 303  */
 304 int ima_file_check(struct file *file, int mask, int opened)
 305 {
 306         return process_measurement(file,
 307                                    mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 308                                    FILE_CHECK, opened);
 309 }
 310 EXPORT_SYMBOL_GPL(ima_file_check);
 311
 312 /**
 313  * ima_module_check - based on policy, collect/store/appraise measurement.
 314  * @file: pointer to the file to be measured/appraised
 315  *
 316  * Measure/appraise kernel modules based on policy.
 317  *
 318  * On success return 0.  On integrity appraisal error, assuming the file
 319  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 320  */
 321 int ima_module_check(struct file *file)
 322 {
 323         if (!file) {
 324 #ifndef CONFIG_MODULE_SIG_FORCE
 325                 if ((ima_appraise & IMA_APPRAISE_MODULES) &&
 326                     (ima_appraise & IMA_APPRAISE_ENFORCE))
 327                         return -EACCES; /* INTEGRITY_UNKNOWN */
 328 #endif
 329                 return 0;       /* We rely on module signature checking */
 330         }
 331         return process_measurement(file, MAY_EXEC, MODULE_CHECK, 0);
 332 }
 333
 334 int ima_fw_from_file(struct file *file, char *buf, size_t size)
 335 {
 336         if (!file) {
 337                 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
 338                     (ima_appraise & IMA_APPRAISE_ENFORCE))
 339                         return -EACCES; /* INTEGRITY_UNKNOWN */
 340                 return 0;
 341         }
 342         return process_measurement(file, MAY_EXEC, FIRMWARE_CHECK, 0);
 343 }
 344
 345 static int __init init_ima(void)
 346 {
 347         int error;
 348
 349         hash_setup(CONFIG_IMA_DEFAULT_HASH);
 350         error = ima_init();
 351         if (!error) {
 352                 ima_initialized = 1;
 353                 ima_update_policy_flag();
 354         }
 355         return error;
 356 }
 357
 358 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 359
 360 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 361 MODULE_LICENSE("GPL");