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