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 {
  82         struct inode *inode = file_inode(file);
  83         fmode_t mode = file->f_mode;
  84         bool send_tomtou = false, send_writers = false;
  85         char *pathbuf = NULL;
  86         const char *pathname;
  87
  88         if (!S_ISREG(inode->i_mode) || !ima_initialized)
  89                 return;
  90
  91         if (mode & FMODE_WRITE) {
  92                 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
  93                         struct integrity_iint_cache *iint;
  94                         iint = integrity_iint_find(inode);
  95                         /* IMA_MEASURE is set from reader side */
  96                         if (iint && (iint->flags & IMA_MEASURE))
  97                                 send_tomtou = true;
  98                 }
  99         } else {
 100                 if ((atomic_read(&inode->i_writecount) > 0) &&
 101                     ima_must_measure(inode, MAY_READ, FILE_CHECK))
 102                         send_writers = true;
 103         }
 104
 105         if (!send_tomtou && !send_writers)
 106                 return;
 107
 108         pathname = ima_d_path(&file->f_path, &pathbuf);
 109
 110         if (send_tomtou)
 111                 ima_add_violation(file, pathname, "invalid_pcr", "ToMToU");
 112         if (send_writers)
 113                 ima_add_violation(file, pathname,
 114                                   "invalid_pcr", "open_writers");
 115         kfree(pathbuf);
 116 }
 117
 118 static void ima_check_last_writer(struct integrity_iint_cache *iint,
 119                                   struct inode *inode, struct file *file)
 120 {
 121         fmode_t mode = file->f_mode;
 122
 123         if (!(mode & FMODE_WRITE))
 124                 return;
 125
 126         mutex_lock(&inode->i_mutex);
 127         if (atomic_read(&inode->i_writecount) == 1 &&
 128             iint->version != inode->i_version) {
 129                 iint->flags &= ~IMA_DONE_MASK;
 130                 if (iint->flags & IMA_APPRAISE)
 131                         ima_update_xattr(iint, file);
 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 (!iint_initialized || !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, const char *filename,
 158                                int mask, int function)
 159 {
 160         struct inode *inode = file_inode(file);
 161         struct integrity_iint_cache *iint;
 162         struct ima_template_desc *template_desc;
 163         char *pathbuf = NULL;
 164         const char *pathname = NULL;
 165         int rc = -ENOMEM, action, must_appraise, _func;
 166         struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
 167         int xattr_len = 0;
 168
 169         if (!ima_initialized || !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         if (!action)
 178                 return 0;
 179
 180         must_appraise = action & IMA_APPRAISE;
 181
 182         /*  Is the appraise rule hook specific?  */
 183         _func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;
 184
 185         mutex_lock(&inode->i_mutex);
 186
 187         iint = integrity_inode_get(inode);
 188         if (!iint)
 189                 goto out;
 190
 191         /* Determine if already appraised/measured based on bitmask
 192          * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
 193          *  IMA_AUDIT, IMA_AUDITED)
 194          */
 195         iint->flags |= action;
 196         action &= IMA_DO_MASK;
 197         action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 198
 199         /* Nothing to do, just return existing appraised status */
 200         if (!action) {
 201                 if (must_appraise)
 202                         rc = ima_get_cache_status(iint, _func);
 203                 goto out_digsig;
 204         }
 205
 206         template_desc = ima_template_desc_current();
 207         if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
 208                 if (action & IMA_APPRAISE_SUBMASK)
 209                         xattr_ptr = &xattr_value;
 210         } else
 211                 xattr_ptr = &xattr_value;
 212
 213         rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
 214         if (rc != 0) {
 215                 if (file->f_flags & O_DIRECT)
 216                         rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
 217                 goto out_digsig;
 218         }
 219
 220         pathname = filename ?: ima_d_path(&file->f_path, &pathbuf);
 221
 222         if (action & IMA_MEASURE)
 223                 ima_store_measurement(iint, file, pathname,
 224                                       xattr_value, xattr_len);
 225         if (action & IMA_APPRAISE_SUBMASK)
 226                 rc = ima_appraise_measurement(_func, iint, file, pathname,
 227                                               xattr_value, xattr_len);
 228         if (action & IMA_AUDIT)
 229                 ima_audit_measurement(iint, pathname);
 230         kfree(pathbuf);
 231 out_digsig:
 232         if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
 233                 rc = -EACCES;
 234 out:
 235         mutex_unlock(&inode->i_mutex);
 236         kfree(xattr_value);
 237         if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
 238                 return -EACCES;
 239         return 0;
 240 }
 241
 242 /**
 243  * ima_file_mmap - based on policy, collect/store measurement.
 244  * @file: pointer to the file to be measured (May be NULL)
 245  * @prot: contains the protection that will be applied by the kernel.
 246  *
 247  * Measure files being mmapped executable based on the ima_must_measure()
 248  * policy decision.
 249  *
 250  * On success return 0.  On integrity appraisal error, assuming the file
 251  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 252  */
 253 int ima_file_mmap(struct file *file, unsigned long prot)
 254 {
 255         if (file && (prot & PROT_EXEC))
 256                 return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK);
 257         return 0;
 258 }
 259
 260 /**
 261  * ima_bprm_check - based on policy, collect/store measurement.
 262  * @bprm: contains the linux_binprm structure
 263  *
 264  * The OS protects against an executable file, already open for write,
 265  * from being executed in deny_write_access() and an executable file,
 266  * already open for execute, from being modified in get_write_access().
 267  * So we can be certain that what we verify and measure here is actually
 268  * what is being executed.
 269  *
 270  * On success return 0.  On integrity appraisal error, assuming the file
 271  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 272  */
 273 int ima_bprm_check(struct linux_binprm *bprm)
 274 {
 275         return process_measurement(bprm->file,
 276                                    (strcmp(bprm->filename, bprm->interp) == 0) ?
 277                                    bprm->filename : bprm->interp,
 278                                    MAY_EXEC, BPRM_CHECK);
 279 }
 280
 281 /**
 282  * ima_path_check - based on policy, collect/store measurement.
 283  * @file: pointer to the file to be measured
 284  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 285  *
 286  * Measure files based on the ima_must_measure() policy decision.
 287  *
 288  * On success return 0.  On integrity appraisal error, assuming the file
 289  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 290  */
 291 int ima_file_check(struct file *file, int mask)
 292 {
 293         ima_rdwr_violation_check(file);
 294         return process_measurement(file, NULL,
 295                                    mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 296                                    FILE_CHECK);
 297 }
 298 EXPORT_SYMBOL_GPL(ima_file_check);
 299
 300 /**
 301  * ima_module_check - based on policy, collect/store/appraise measurement.
 302  * @file: pointer to the file to be measured/appraised
 303  *
 304  * Measure/appraise kernel modules based on policy.
 305  *
 306  * On success return 0.  On integrity appraisal error, assuming the file
 307  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 308  */
 309 int ima_module_check(struct file *file)
 310 {
 311         if (!file) {
 312 #ifndef CONFIG_MODULE_SIG_FORCE
 313                 if ((ima_appraise & IMA_APPRAISE_MODULES) &&
 314                     (ima_appraise & IMA_APPRAISE_ENFORCE))
 315                         return -EACCES; /* INTEGRITY_UNKNOWN */
 316 #endif
 317                 return 0;       /* We rely on module signature checking */
 318         }
 319         return process_measurement(file, NULL, MAY_EXEC, MODULE_CHECK);
 320 }
 321
 322 static int __init init_ima(void)
 323 {
 324         int error;
 325
 326         hash_setup(CONFIG_IMA_DEFAULT_HASH);
 327         error = ima_init();
 328         if (error)
 329                 goto out;
 330
 331         error = ima_init_keyring(INTEGRITY_KEYRING_IMA);
 332         if (error)
 333                 goto out;
 334         ima_initialized = 1;
 335 out:
 336         return error;
 337 }
 338
 339 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 340
 341 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 342 MODULE_LICENSE("GPL");