release/src-rt-6.x.4708/linux/linux-2.6.36/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
  26 #include "ima.h"
  27
  28 int ima_initialized;
  29
  30 char *ima_hash = "sha1";
  31 static int __init hash_setup(char *str)
  32 {
  33         if (strncmp(str, "md5", 3) == 0)
  34                 ima_hash = "md5";
  35         return 1;
  36 }
  37 __setup("ima_hash=", hash_setup);
  38
  39 struct ima_imbalance {
  40         struct hlist_node node;
  41         unsigned long fsmagic;
  42 };
  43
  44 /*
  45  * ima_limit_imbalance - emit one imbalance message per filesystem type
  46  *
  47  * Maintain list of filesystem types that do not measure files properly.
  48  * Return false if unknown, true if known.
  49  */
  50 static bool ima_limit_imbalance(struct file *file)
  51 {
  52         static DEFINE_SPINLOCK(ima_imbalance_lock);
  53         static HLIST_HEAD(ima_imbalance_list);
  54
  55         struct super_block *sb = file->f_dentry->d_sb;
  56         struct ima_imbalance *entry;
  57         struct hlist_node *node;
  58         bool found = false;
  59
  60         rcu_read_lock();
  61         hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) {
  62                 if (entry->fsmagic == sb->s_magic) {
  63                         found = true;
  64                         break;
  65                 }
  66         }
  67         rcu_read_unlock();
  68         if (found)
  69                 goto out;
  70
  71         entry = kmalloc(sizeof(*entry), GFP_NOFS);
  72         if (!entry)
  73                 goto out;
  74         entry->fsmagic = sb->s_magic;
  75         spin_lock(&ima_imbalance_lock);
  76         /*
  77          * we could have raced and something else might have added this fs
  78          * to the list, but we don't really care
  79          */
  80         hlist_add_head_rcu(&entry->node, &ima_imbalance_list);
  81         spin_unlock(&ima_imbalance_lock);
  82         printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n",
  83                entry->fsmagic);
  84 out:
  85         return found;
  86 }
  87
  88 /* ima_read_write_check - reflect possible reading/writing errors in the PCR.
  89  *
  90  * When opening a file for read, if the file is already open for write,
  91  * the file could change, resulting in a file measurement error.
  92  *
  93  * Opening a file for write, if the file is already open for read, results
  94  * in a time of measure, time of use (ToMToU) error.
  95  *
  96  * In either case invalidate the PCR.
  97  */
  98 enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
  99 static void ima_read_write_check(enum iint_pcr_error error,
 100                                  struct ima_iint_cache *iint,
 101                                  struct inode *inode,
 102                                  const unsigned char *filename)
 103 {
 104         switch (error) {
 105         case TOMTOU:
 106                 if (iint->readcount > 0)
 107                         ima_add_violation(inode, filename, "invalid_pcr",
 108                                           "ToMToU");
 109                 break;
 110         case OPEN_WRITERS:
 111                 if (iint->writecount > 0)
 112                         ima_add_violation(inode, filename, "invalid_pcr",
 113                                           "open_writers");
 114                 break;
 115         }
 116 }
 117
 118 /*
 119  * Update the counts given an fmode_t
 120  */
 121 static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
 122 {
 123         BUG_ON(!mutex_is_locked(&iint->mutex));
 124
 125         iint->opencount++;
 126         if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 127                 iint->readcount++;
 128         if (mode & FMODE_WRITE)
 129                 iint->writecount++;
 130 }
 131
 132 /*
 133  * ima_counts_get - increment file counts
 134  *
 135  * Maintain read/write counters for all files, but only
 136  * invalidate the PCR for measured files:
 137  *      - Opening a file for write when already open for read,
 138  *        results in a time of measure, time of use (ToMToU) error.
 139  *      - Opening a file for read when already open for write,
 140  *        could result in a file measurement error.
 141  *
 142  */
 143 void ima_counts_get(struct file *file)
 144 {
 145         struct dentry *dentry = file->f_path.dentry;
 146         struct inode *inode = dentry->d_inode;
 147         fmode_t mode = file->f_mode;
 148         struct ima_iint_cache *iint;
 149         int rc;
 150
 151         if (!iint_initialized || !S_ISREG(inode->i_mode))
 152                 return;
 153         iint = ima_iint_find_get(inode);
 154         if (!iint)
 155                 return;
 156         mutex_lock(&iint->mutex);
 157         if (!ima_initialized)
 158                 goto out;
 159         rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK);
 160         if (rc < 0)
 161                 goto out;
 162
 163         if (mode & FMODE_WRITE) {
 164                 ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
 165                 goto out;
 166         }
 167         ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);
 168 out:
 169         ima_inc_counts(iint, file->f_mode);
 170         mutex_unlock(&iint->mutex);
 171
 172         kref_put(&iint->refcount, iint_free);
 173 }
 174
 175 /*
 176  * Decrement ima counts
 177  */
 178 static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
 179                            struct file *file)
 180 {
 181         mode_t mode = file->f_mode;
 182         BUG_ON(!mutex_is_locked(&iint->mutex));
 183
 184         iint->opencount--;
 185         if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 186                 iint->readcount--;
 187         if (mode & FMODE_WRITE) {
 188                 iint->writecount--;
 189                 if (iint->writecount == 0) {
 190                         if (iint->version != inode->i_version)
 191                                 iint->flags &= ~IMA_MEASURED;
 192                 }
 193         }
 194
 195         if (((iint->opencount < 0) ||
 196              (iint->readcount < 0) ||
 197              (iint->writecount < 0)) &&
 198             !ima_limit_imbalance(file)) {
 199                 printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld o:%ld)\n",
 200                        __func__, iint->readcount, iint->writecount,
 201                        iint->opencount);
 202                 dump_stack();
 203         }
 204 }
 205
 206 /**
 207  * ima_file_free - called on __fput()
 208  * @file: pointer to file structure being freed
 209  *
 210  * Flag files that changed, based on i_version;
 211  * and decrement the iint readcount/writecount.
 212  */
 213 void ima_file_free(struct file *file)
 214 {
 215         struct inode *inode = file->f_dentry->d_inode;
 216         struct ima_iint_cache *iint;
 217
 218         if (!iint_initialized || !S_ISREG(inode->i_mode))
 219                 return;
 220         iint = ima_iint_find_get(inode);
 221         if (!iint)
 222                 return;
 223
 224         mutex_lock(&iint->mutex);
 225         ima_dec_counts(iint, inode, file);
 226         mutex_unlock(&iint->mutex);
 227         kref_put(&iint->refcount, iint_free);
 228 }
 229
 230 static int process_measurement(struct file *file, const unsigned char *filename,
 231                                int mask, int function)
 232 {
 233         struct inode *inode = file->f_dentry->d_inode;
 234         struct ima_iint_cache *iint;
 235         int rc = 0;
 236
 237         if (!ima_initialized || !S_ISREG(inode->i_mode))
 238                 return 0;
 239         iint = ima_iint_find_get(inode);
 240         if (!iint)
 241                 return -ENOMEM;
 242
 243         mutex_lock(&iint->mutex);
 244         rc = ima_must_measure(iint, inode, mask, function);
 245         if (rc != 0)
 246                 goto out;
 247
 248         rc = ima_collect_measurement(iint, file);
 249         if (!rc)
 250                 ima_store_measurement(iint, file, filename);
 251 out:
 252         mutex_unlock(&iint->mutex);
 253         kref_put(&iint->refcount, iint_free);
 254         return rc;
 255 }
 256
 257 /**
 258  * ima_file_mmap - based on policy, collect/store measurement.
 259  * @file: pointer to the file to be measured (May be NULL)
 260  * @prot: contains the protection that will be applied by the kernel.
 261  *
 262  * Measure files being mmapped executable based on the ima_must_measure()
 263  * policy decision.
 264  *
 265  * Return 0 on success, an error code on failure.
 266  * (Based on the results of appraise_measurement().)
 267  */
 268 int ima_file_mmap(struct file *file, unsigned long prot)
 269 {
 270         int rc;
 271
 272         if (!file)
 273                 return 0;
 274         if (prot & PROT_EXEC)
 275                 rc = process_measurement(file, file->f_dentry->d_name.name,
 276                                          MAY_EXEC, FILE_MMAP);
 277         return 0;
 278 }
 279
 280 /**
 281  * ima_bprm_check - based on policy, collect/store measurement.
 282  * @bprm: contains the linux_binprm structure
 283  *
 284  * The OS protects against an executable file, already open for write,
 285  * from being executed in deny_write_access() and an executable file,
 286  * already open for execute, from being modified in get_write_access().
 287  * So we can be certain that what we verify and measure here is actually
 288  * what is being executed.
 289  *
 290  * Return 0 on success, an error code on failure.
 291  * (Based on the results of appraise_measurement().)
 292  */
 293 int ima_bprm_check(struct linux_binprm *bprm)
 294 {
 295         int rc;
 296
 297         rc = process_measurement(bprm->file, bprm->filename,
 298                                  MAY_EXEC, BPRM_CHECK);
 299         return 0;
 300 }
 301
 302 /**
 303  * ima_path_check - based on policy, collect/store measurement.
 304  * @file: pointer to the file to be measured
 305  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 306  *
 307  * Measure files based on the ima_must_measure() policy decision.
 308  *
 309  * Always return 0 and audit dentry_open failures.
 310  * (Return code will be based upon measurement appraisal.)
 311  */
 312 int ima_file_check(struct file *file, int mask)
 313 {
 314         int rc;
 315
 316         rc = process_measurement(file, file->f_dentry->d_name.name,
 317                                  mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 318                                  FILE_CHECK);
 319         return 0;
 320 }
 321 EXPORT_SYMBOL_GPL(ima_file_check);
 322
 323 static int __init init_ima(void)
 324 {
 325         int error;
 326
 327         error = ima_init();
 328         ima_initialized = 1;
 329         return error;
 330 }
 331
 332 static void __exit cleanup_ima(void)
 333 {
 334         ima_cleanup();
 335 }
 336
 337 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 338
 339 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 340 MODULE_LICENSE("GPL");