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
  28 #include "ima.h"
  29
  30 int ima_initialized;
  31
  32 #ifdef CONFIG_IMA_APPRAISE
  33 int ima_appraise = IMA_APPRAISE_ENFORCE;
  34 #else
  35 int ima_appraise;
  36 #endif
  37
  38 char *ima_hash = "sha1";
  39 static int __init hash_setup(char *str)
  40 {
  41         if (strncmp(str, "md5", 3) == 0)
  42                 ima_hash = "md5";
  43         return 1;
  44 }
  45 __setup("ima_hash=", hash_setup);
  46
  47 /*
  48  * ima_rdwr_violation_check
  49  *
  50  * Only invalidate the PCR for measured files:
  51  *      - Opening a file for write when already open for read,
  52  *        results in a time of measure, time of use (ToMToU) error.
  53  *      - Opening a file for read when already open for write,
  54  *        could result in a file measurement error.
  55  *
  56  */
  57 static void ima_rdwr_violation_check(struct file *file)
  58 {
  59         struct dentry *dentry = file->f_path.dentry;
  60         struct inode *inode = dentry->d_inode;
  61         fmode_t mode = file->f_mode;
  62         int must_measure;
  63         bool send_tomtou = false, send_writers = false;
  64         unsigned char *pathname = NULL, *pathbuf = NULL;
  65
  66         if (!S_ISREG(inode->i_mode) || !ima_initialized)
  67                 return;
  68
  69         mutex_lock(&inode->i_mutex);    /* file metadata: permissions, xattr */
  70
  71         if (mode & FMODE_WRITE) {
  72                 if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
  73                         send_tomtou = true;
  74                 goto out;
  75         }
  76
  77         must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK);
  78         if (!must_measure)
  79                 goto out;
  80
  81         if (atomic_read(&inode->i_writecount) > 0)
  82                 send_writers = true;
  83 out:
  84         mutex_unlock(&inode->i_mutex);
  85
  86         if (!send_tomtou && !send_writers)
  87                 return;
  88
  89         /* We will allow 11 spaces for ' (deleted)' to be appended */
  90         pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
  91         if (pathbuf) {
  92                 pathname = d_path(&file->f_path, pathbuf, PATH_MAX + 11);
  93                 if (IS_ERR(pathname))
  94                         pathname = NULL;
  95                 else if (strlen(pathname) > IMA_EVENT_NAME_LEN_MAX)
  96                         pathname = NULL;
  97         }
  98         if (send_tomtou)
  99                 ima_add_violation(inode,
 100                                   !pathname ? dentry->d_name.name : pathname,
 101                                   "invalid_pcr", "ToMToU");
 102         if (send_writers)
 103                 ima_add_violation(inode,
 104                                   !pathname ? dentry->d_name.name : pathname,
 105                                   "invalid_pcr", "open_writers");
 106         kfree(pathbuf);
 107 }
 108
 109 static void ima_check_last_writer(struct integrity_iint_cache *iint,
 110                                   struct inode *inode, struct file *file)
 111 {
 112         fmode_t mode = file->f_mode;
 113
 114         if (!(mode & FMODE_WRITE))
 115                 return;
 116
 117         mutex_lock(&inode->i_mutex);
 118         if (atomic_read(&inode->i_writecount) == 1 &&
 119             iint->version != inode->i_version) {
 120                 iint->flags &= ~IMA_DONE_MASK;
 121                 if (iint->flags & IMA_APPRAISE)
 122                         ima_update_xattr(iint, file);
 123         }
 124         mutex_unlock(&inode->i_mutex);
 125 }
 126
 127 /**
 128  * ima_file_free - called on __fput()
 129  * @file: pointer to file structure being freed
 130  *
 131  * Flag files that changed, based on i_version
 132  */
 133 void ima_file_free(struct file *file)
 134 {
 135         struct inode *inode = file_inode(file);
 136         struct integrity_iint_cache *iint;
 137
 138         if (!iint_initialized || !S_ISREG(inode->i_mode))
 139                 return;
 140
 141         iint = integrity_iint_find(inode);
 142         if (!iint)
 143                 return;
 144
 145         ima_check_last_writer(iint, inode, file);
 146 }
 147
 148 static int process_measurement(struct file *file, const unsigned char *filename,
 149                                int mask, int function)
 150 {
 151         struct inode *inode = file_inode(file);
 152         struct integrity_iint_cache *iint;
 153         unsigned char *pathname = NULL, *pathbuf = NULL;
 154         int rc = -ENOMEM, action, must_appraise;
 155
 156         if (!ima_initialized || !S_ISREG(inode->i_mode))
 157                 return 0;
 158
 159         /* Determine if in appraise/audit/measurement policy,
 160          * returns IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT bitmask.  */
 161         action = ima_get_action(inode, mask, function);
 162         if (!action)
 163                 return 0;
 164
 165         must_appraise = action & IMA_APPRAISE;
 166
 167         mutex_lock(&inode->i_mutex);
 168
 169         iint = integrity_inode_get(inode);
 170         if (!iint)
 171                 goto out;
 172
 173         /* Determine if already appraised/measured based on bitmask
 174          * (IMA_MEASURE, IMA_MEASURED, IMA_APPRAISE, IMA_APPRAISED,
 175          *  IMA_AUDIT, IMA_AUDITED) */
 176         iint->flags |= action;
 177         action &= ~((iint->flags & IMA_DONE_MASK) >> 1);
 178
 179         /* Nothing to do, just return existing appraised status */
 180         if (!action) {
 181                 if (iint->flags & IMA_APPRAISED)
 182                         rc = iint->ima_status;
 183                 goto out;
 184         }
 185
 186         rc = ima_collect_measurement(iint, file);
 187         if (rc != 0)
 188                 goto out;
 189
 190         if (function != BPRM_CHECK) {
 191                 /* We will allow 11 spaces for ' (deleted)' to be appended */
 192                 pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
 193                 if (pathbuf) {
 194                         pathname =
 195                             d_path(&file->f_path, pathbuf, PATH_MAX + 11);
 196                         if (IS_ERR(pathname))
 197                                 pathname = NULL;
 198                 }
 199         }
 200         if (action & IMA_MEASURE)
 201                 ima_store_measurement(iint, file,
 202                                       !pathname ? filename : pathname);
 203         if (action & IMA_APPRAISE)
 204                 rc = ima_appraise_measurement(iint, file,
 205                                               !pathname ? filename : pathname);
 206         if (action & IMA_AUDIT)
 207                 ima_audit_measurement(iint, !pathname ? filename : pathname);
 208         kfree(pathbuf);
 209 out:
 210         mutex_unlock(&inode->i_mutex);
 211         return (rc && must_appraise) ? -EACCES : 0;
 212 }
 213
 214 /**
 215  * ima_file_mmap - based on policy, collect/store measurement.
 216  * @file: pointer to the file to be measured (May be NULL)
 217  * @prot: contains the protection that will be applied by the kernel.
 218  *
 219  * Measure files being mmapped executable based on the ima_must_measure()
 220  * policy decision.
 221  *
 222  * Return 0 on success, an error code on failure.
 223  * (Based on the results of appraise_measurement().)
 224  */
 225 int ima_file_mmap(struct file *file, unsigned long prot)
 226 {
 227         int rc = 0;
 228
 229         if (!file)
 230                 return 0;
 231         if (prot & PROT_EXEC)
 232                 rc = process_measurement(file, file->f_dentry->d_name.name,
 233                                          MAY_EXEC, FILE_MMAP);
 234         return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
 235 }
 236
 237 /**
 238  * ima_bprm_check - based on policy, collect/store measurement.
 239  * @bprm: contains the linux_binprm structure
 240  *
 241  * The OS protects against an executable file, already open for write,
 242  * from being executed in deny_write_access() and an executable file,
 243  * already open for execute, from being modified in get_write_access().
 244  * So we can be certain that what we verify and measure here is actually
 245  * what is being executed.
 246  *
 247  * Return 0 on success, an error code on failure.
 248  * (Based on the results of appraise_measurement().)
 249  */
 250 int ima_bprm_check(struct linux_binprm *bprm)
 251 {
 252         int rc;
 253
 254         rc = process_measurement(bprm->file,
 255                                  (strcmp(bprm->filename, bprm->interp) == 0) ?
 256                                  bprm->filename : bprm->interp,
 257                                  MAY_EXEC, BPRM_CHECK);
 258         return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
 259 }
 260
 261 /**
 262  * ima_path_check - based on policy, collect/store measurement.
 263  * @file: pointer to the file to be measured
 264  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 265  *
 266  * Measure files based on the ima_must_measure() policy decision.
 267  *
 268  * Always return 0 and audit dentry_open failures.
 269  * (Return code will be based upon measurement appraisal.)
 270  */
 271 int ima_file_check(struct file *file, int mask)
 272 {
 273         int rc;
 274
 275         ima_rdwr_violation_check(file);
 276         rc = process_measurement(file, file->f_dentry->d_name.name,
 277                                  mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 278                                  FILE_CHECK);
 279         return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
 280 }
 281 EXPORT_SYMBOL_GPL(ima_file_check);
 282
 283 /**
 284  * ima_module_check - based on policy, collect/store/appraise measurement.
 285  * @file: pointer to the file to be measured/appraised
 286  *
 287  * Measure/appraise kernel modules based on policy.
 288  *
 289  * Always return 0 and audit dentry_open failures.
 290  * Return code is based upon measurement appraisal.
 291  */
 292 int ima_module_check(struct file *file)
 293 {
 294         int rc = 0;
 295
 296         if (!file) {
 297                 if (ima_appraise & IMA_APPRAISE_MODULES) {
 298 #ifndef CONFIG_MODULE_SIG_FORCE
 299                         rc = -EACCES;   /* INTEGRITY_UNKNOWN */
 300 #endif
 301                 }
 302         } else
 303                 rc = process_measurement(file, file->f_dentry->d_name.name,
 304                                          MAY_EXEC, MODULE_CHECK);
 305         return (ima_appraise & IMA_APPRAISE_ENFORCE) ? rc : 0;
 306 }
 307
 308 static int __init init_ima(void)
 309 {
 310         int error;
 311
 312         error = ima_init();
 313         if (!error)
 314                 ima_initialized = 1;
 315         return error;
 316 }
 317
 318 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 319
 320 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 321 MODULE_LICENSE("GPL");