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         int must_measure;
  85         bool send_tomtou = false, send_writers = false;
  86         char *pathbuf = NULL;
  87         const char *pathname;
  88
  89         if (!S_ISREG(inode->i_mode) || !ima_initialized)
  90                 return;
  91
  92         mutex_lock(&inode->i_mutex);    /* file metadata: permissions, xattr */
  93
  94         if (mode & FMODE_WRITE) {
  95                 if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
  96                         send_tomtou = true;
  97                 goto out;
  98         }
  99
 100         must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK);
 101         if (!must_measure)
 102                 goto out;
 103
 104         if (atomic_read(&inode->i_writecount) > 0)
 105                 send_writers = true;
 106 out:
 107         mutex_unlock(&inode->i_mutex);
 108
 109         if (!send_tomtou && !send_writers)
 110                 return;
 111
 112         pathname = ima_d_path(&file->f_path, &pathbuf);
 113
 114         if (send_tomtou)
 115                 ima_add_violation(file, pathname, "invalid_pcr", "ToMToU");
 116         if (send_writers)
 117                 ima_add_violation(file, pathname,
 118                                   "invalid_pcr", "open_writers");
 119         kfree(pathbuf);
 120 }
 121
 122 static void ima_check_last_writer(struct integrity_iint_cache *iint,
 123                                   struct inode *inode, struct file *file)
 124 {
 125         fmode_t mode = file->f_mode;
 126
 127         if (!(mode & FMODE_WRITE))
 128                 return;
 129
 130         mutex_lock(&inode->i_mutex);
 131         if (atomic_read(&inode->i_writecount) == 1 &&
 132             iint->version != inode->i_version) {
 133                 iint->flags &= ~IMA_DONE_MASK;
 134                 if (iint->flags & IMA_APPRAISE)
 135                         ima_update_xattr(iint, file);
 136         }
 137         mutex_unlock(&inode->i_mutex);
 138 }
 139
 140 /**
 141  * ima_file_free - called on __fput()
 142  * @file: pointer to file structure being freed
 143  *
 144  * Flag files that changed, based on i_version
 145  */
 146 void ima_file_free(struct file *file)
 147 {
 148         struct inode *inode = file_inode(file);
 149         struct integrity_iint_cache *iint;
 150
 151         if (!iint_initialized || !S_ISREG(inode->i_mode))
 152                 return;
 153
 154         iint = integrity_iint_find(inode);
 155         if (!iint)
 156                 return;
 157
 158         ima_check_last_writer(iint, inode, file);
 159 }
 160
 161 static int process_measurement(struct file *file, const char *filename,
 162                                int mask, int function)
 163 {
 164         struct inode *inode = file_inode(file);
 165         struct integrity_iint_cache *iint;
 166         struct ima_template_desc *template_desc = ima_template_desc_current();
 167         char *pathbuf = NULL;
 168         const char *pathname = NULL;
 169         int rc = -ENOMEM, action, must_appraise, _func;
 170         struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
 171         int xattr_len = 0;
 172
 173         if (!ima_initialized || !S_ISREG(inode->i_mode))
 174                 return 0;
 175
 176         /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
 177          * bitmask based on the appraise/audit/measurement policy.
 178          * Included is the appraise submask.
 179          */
 180         action = ima_get_action(inode, mask, function);
 181         if (!action)
 182                 return 0;
 183
 184         must_appraise = action & IMA_APPRAISE;
 185
 186         /*  Is the appraise rule hook specific?  */
 187         _func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function;
 188
 189         mutex_lock(&inode->i_mutex);
 190
 191         iint = integrity_inode_get(inode);
 192         if (!iint)
 193                 goto out;
 194
 195         /* Determine if already appraised/measured based on bitmask
 196          * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
 197          *  IMA_AUDIT, IMA_AUDITED)
 198          */
 199         iint->flags |= action;
 200         action &= IMA_DO_MASK;
 201         action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 202
 203         /* Nothing to do, just return existing appraised status */
 204         if (!action) {
 205                 if (must_appraise)
 206                         rc = ima_get_cache_status(iint, _func);
 207                 goto out_digsig;
 208         }
 209
 210         if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
 211                 if (action & IMA_APPRAISE_SUBMASK)
 212                         xattr_ptr = &xattr_value;
 213         } else
 214                 xattr_ptr = &xattr_value;
 215
 216         rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
 217         if (rc != 0) {
 218                 if (file->f_flags & O_DIRECT)
 219                         rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
 220                 goto out_digsig;
 221         }
 222
 223         pathname = filename ?: ima_d_path(&file->f_path, &pathbuf);
 224
 225         if (action & IMA_MEASURE)
 226                 ima_store_measurement(iint, file, pathname,
 227                                       xattr_value, xattr_len);
 228         if (action & IMA_APPRAISE_SUBMASK)
 229                 rc = ima_appraise_measurement(_func, iint, file, pathname,
 230                                               xattr_value, xattr_len);
 231         if (action & IMA_AUDIT)
 232                 ima_audit_measurement(iint, pathname);
 233         kfree(pathbuf);
 234 out_digsig:
 235         if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
 236                 rc = -EACCES;
 237 out:
 238         mutex_unlock(&inode->i_mutex);
 239         kfree(xattr_value);
 240         if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
 241                 return -EACCES;
 242         return 0;
 243 }
 244
 245 /**
 246  * ima_file_mmap - based on policy, collect/store measurement.
 247  * @file: pointer to the file to be measured (May be NULL)
 248  * @prot: contains the protection that will be applied by the kernel.
 249  *
 250  * Measure files being mmapped executable based on the ima_must_measure()
 251  * policy decision.
 252  *
 253  * On success return 0.  On integrity appraisal error, assuming the file
 254  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 255  */
 256 int ima_file_mmap(struct file *file, unsigned long prot)
 257 {
 258         if (file && (prot & PROT_EXEC))
 259                 return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK);
 260         return 0;
 261 }
 262
 263 /**
 264  * ima_bprm_check - based on policy, collect/store measurement.
 265  * @bprm: contains the linux_binprm structure
 266  *
 267  * The OS protects against an executable file, already open for write,
 268  * from being executed in deny_write_access() and an executable file,
 269  * already open for execute, from being modified in get_write_access().
 270  * So we can be certain that what we verify and measure here is actually
 271  * what is being executed.
 272  *
 273  * On success return 0.  On integrity appraisal error, assuming the file
 274  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 275  */
 276 int ima_bprm_check(struct linux_binprm *bprm)
 277 {
 278         return process_measurement(bprm->file,
 279                                    (strcmp(bprm->filename, bprm->interp) == 0) ?
 280                                    bprm->filename : bprm->interp,
 281                                    MAY_EXEC, BPRM_CHECK);
 282 }
 283
 284 /**
 285  * ima_path_check - based on policy, collect/store measurement.
 286  * @file: pointer to the file to be measured
 287  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 288  *
 289  * Measure files based on the ima_must_measure() policy decision.
 290  *
 291  * On success return 0.  On integrity appraisal error, assuming the file
 292  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 293  */
 294 int ima_file_check(struct file *file, int mask)
 295 {
 296         ima_rdwr_violation_check(file);
 297         return process_measurement(file, NULL,
 298                                    mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 299                                    FILE_CHECK);
 300 }
 301 EXPORT_SYMBOL_GPL(ima_file_check);
 302
 303 /**
 304  * ima_module_check - based on policy, collect/store/appraise measurement.
 305  * @file: pointer to the file to be measured/appraised
 306  *
 307  * Measure/appraise kernel modules based on policy.
 308  *
 309  * On success return 0.  On integrity appraisal error, assuming the file
 310  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
 311  */
 312 int ima_module_check(struct file *file)
 313 {
 314         if (!file) {
 315 #ifndef CONFIG_MODULE_SIG_FORCE
 316                 if ((ima_appraise & IMA_APPRAISE_MODULES) &&
 317                     (ima_appraise & IMA_APPRAISE_ENFORCE))
 318                         return -EACCES; /* INTEGRITY_UNKNOWN */
 319 #endif
 320                 return 0;       /* We rely on module signature checking */
 321         }
 322         return process_measurement(file, NULL, MAY_EXEC, MODULE_CHECK);
 323 }
 324
 325 static int __init init_ima(void)
 326 {
 327         int error;
 328
 329         hash_setup(CONFIG_IMA_DEFAULT_HASH);
 330         error = ima_init();
 331         if (!error)
 332                 ima_initialized = 1;
 333         return error;
 334 }
 335
 336 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 337
 338 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 339 MODULE_LICENSE("GPL");