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_path_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
  25 #include "ima.h"
  26
  27 int ima_initialized;
  28
  29 char *ima_hash = "sha1";
  30 static int __init hash_setup(char *str)
  31 {
  32         const char *op = "hash_setup";
  33         const char *hash = "sha1";
  34         int result = 0;
  35         int audit_info = 0;
  36
  37         if (strncmp(str, "md5", 3) == 0) {
  38                 hash = "md5";
  39                 ima_hash = str;
  40         } else if (strncmp(str, "sha1", 4) != 0) {
  41                 hash = "invalid_hash_type";
  42                 result = 1;
  43         }
  44         integrity_audit_msg(AUDIT_INTEGRITY_HASH, NULL, NULL, op, hash,
  45                             result, audit_info);
  46         return 1;
  47 }
  48 __setup("ima_hash=", hash_setup);
  49
  50 /**
  51  * ima_file_free - called on __fput()
  52  * @file: pointer to file structure being freed
  53  *
  54  * Flag files that changed, based on i_version;
  55  * and decrement the iint readcount/writecount.
  56  */
  57 void ima_file_free(struct file *file)
  58 {
  59         struct inode *inode = file->f_dentry->d_inode;
  60         struct ima_iint_cache *iint;
  61
  62         if (!ima_initialized || !S_ISREG(inode->i_mode))
  63                 return;
  64         iint = ima_iint_find_get(inode);
  65         if (!iint)
  66                 return;
  67
  68         mutex_lock(&iint->mutex);
  69         if (iint->opencount <= 0) {
  70                 printk(KERN_INFO
  71                        "%s: %s open/free imbalance (r:%ld w:%ld o:%ld f:%ld)\n",
  72                        __FUNCTION__, file->f_dentry->d_name.name,
  73                        iint->readcount, iint->writecount,
  74                        iint->opencount, atomic_long_read(&file->f_count));
  75                 if (!(iint->flags & IMA_IINT_DUMP_STACK)) {
  76                         dump_stack();
  77                         iint->flags |= IMA_IINT_DUMP_STACK;
  78                 }
  79         }
  80         iint->opencount--;
  81
  82         if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
  83                 iint->readcount--;
  84
  85         if (file->f_mode & FMODE_WRITE) {
  86                 iint->writecount--;
  87                 if (iint->writecount == 0) {
  88                         if (iint->version != inode->i_version)
  89                                 iint->flags &= ~IMA_MEASURED;
  90                 }
  91         }
  92         mutex_unlock(&iint->mutex);
  93         kref_put(&iint->refcount, iint_free);
  94 }
  95
  96 /* ima_read_write_check - reflect possible reading/writing errors in the PCR.
  97  *
  98  * When opening a file for read, if the file is already open for write,
  99  * the file could change, resulting in a file measurement error.
 100  *
 101  * Opening a file for write, if the file is already open for read, results
 102  * in a time of measure, time of use (ToMToU) error.
 103  *
 104  * In either case invalidate the PCR.
 105  */
 106 enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
 107 static void ima_read_write_check(enum iint_pcr_error error,
 108                                  struct ima_iint_cache *iint,
 109                                  struct inode *inode,
 110                                  const unsigned char *filename)
 111 {
 112         switch (error) {
 113         case TOMTOU:
 114                 if (iint->readcount > 0)
 115                         ima_add_violation(inode, filename, "invalid_pcr",
 116                                           "ToMToU");
 117                 break;
 118         case OPEN_WRITERS:
 119                 if (iint->writecount > 0)
 120                         ima_add_violation(inode, filename, "invalid_pcr",
 121                                           "open_writers");
 122                 break;
 123         }
 124 }
 125
 126 static int get_path_measurement(struct ima_iint_cache *iint, struct file *file,
 127                                 const unsigned char *filename)
 128 {
 129         int rc = 0;
 130
 131         if (IS_ERR(file)) {
 132                 pr_info("%s dentry_open failed\n", filename);
 133                 return rc;
 134         }
 135         iint->opencount++;
 136         iint->readcount++;
 137
 138         rc = ima_collect_measurement(iint, file);
 139         if (!rc)
 140                 ima_store_measurement(iint, file, filename);
 141         return rc;
 142 }
 143
 144 /**
 145  * ima_path_check - based on policy, collect/store measurement.
 146  * @path: contains a pointer to the path to be measured
 147  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 148  *
 149  * Measure the file being open for readonly, based on the
 150  * ima_must_measure() policy decision.
 151  *
 152  * Keep read/write counters for all files, but only
 153  * invalidate the PCR for measured files:
 154  *      - Opening a file for write when already open for read,
 155  *        results in a time of measure, time of use (ToMToU) error.
 156  *      - Opening a file for read when already open for write,
 157  *        could result in a file measurement error.
 158  *
 159  * Return 0 on success, an error code on failure.
 160  * (Based on the results of appraise_measurement().)
 161  */
 162 int ima_path_check(struct path *path, int mask)
 163 {
 164         struct inode *inode = path->dentry->d_inode;
 165         struct ima_iint_cache *iint;
 166         struct file *file = NULL;
 167         int rc;
 168
 169         if (!ima_initialized || !S_ISREG(inode->i_mode))
 170                 return 0;
 171         iint = ima_iint_find_insert_get(inode);
 172         if (!iint)
 173                 return 0;
 174
 175         mutex_lock(&iint->mutex);
 176         iint->opencount++;
 177         if ((mask & MAY_WRITE) || (mask == 0))
 178                 iint->writecount++;
 179         else if (mask & (MAY_READ | MAY_EXEC))
 180                 iint->readcount++;
 181
 182         rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
 183         if (rc < 0)
 184                 goto out;
 185
 186         if ((mask & MAY_WRITE) || (mask == 0))
 187                 ima_read_write_check(TOMTOU, iint, inode,
 188                                      path->dentry->d_name.name);
 189
 190         if ((mask & (MAY_WRITE | MAY_READ | MAY_EXEC)) != MAY_READ)
 191                 goto out;
 192
 193         ima_read_write_check(OPEN_WRITERS, iint, inode,
 194                              path->dentry->d_name.name);
 195         if (!(iint->flags & IMA_MEASURED)) {
 196                 struct dentry *dentry = dget(path->dentry);
 197                 struct vfsmount *mnt = mntget(path->mnt);
 198
 199                 file = dentry_open(dentry, mnt, O_RDONLY, current->cred);
 200                 rc = get_path_measurement(iint, file, dentry->d_name.name);
 201         }
 202 out:
 203         mutex_unlock(&iint->mutex);
 204         if (file)
 205                 fput(file);
 206         kref_put(&iint->refcount, iint_free);
 207         return 0;
 208 }
 209
 210 static int process_measurement(struct file *file, const unsigned char *filename,
 211                                int mask, int function)
 212 {
 213         struct inode *inode = file->f_dentry->d_inode;
 214         struct ima_iint_cache *iint;
 215         int rc;
 216
 217         if (!ima_initialized || !S_ISREG(inode->i_mode))
 218                 return 0;
 219         iint = ima_iint_find_insert_get(inode);
 220         if (!iint)
 221                 return -ENOMEM;
 222
 223         mutex_lock(&iint->mutex);
 224         rc = ima_must_measure(iint, inode, mask, function);
 225         if (rc != 0)
 226                 goto out;
 227
 228         rc = ima_collect_measurement(iint, file);
 229         if (!rc)
 230                 ima_store_measurement(iint, file, filename);
 231 out:
 232         mutex_unlock(&iint->mutex);
 233         kref_put(&iint->refcount, iint_free);
 234         return rc;
 235 }
 236
 237 static void opencount_get(struct file *file)
 238 {
 239         struct inode *inode = file->f_dentry->d_inode;
 240         struct ima_iint_cache *iint;
 241
 242         if (!ima_initialized || !S_ISREG(inode->i_mode))
 243                 return;
 244         iint = ima_iint_find_insert_get(inode);
 245         if (!iint)
 246                 return;
 247         mutex_lock(&iint->mutex);
 248         iint->opencount++;
 249         mutex_unlock(&iint->mutex);
 250 }
 251
 252 /**
 253  * ima_file_mmap - based on policy, collect/store measurement.
 254  * @file: pointer to the file to be measured (May be NULL)
 255  * @prot: contains the protection that will be applied by the kernel.
 256  *
 257  * Measure files being mmapped executable based on the ima_must_measure()
 258  * policy decision.
 259  *
 260  * Return 0 on success, an error code on failure.
 261  * (Based on the results of appraise_measurement().)
 262  */
 263 int ima_file_mmap(struct file *file, unsigned long prot)
 264 {
 265         int rc;
 266
 267         if (!file)
 268                 return 0;
 269         if (prot & PROT_EXEC)
 270                 rc = process_measurement(file, file->f_dentry->d_name.name,
 271                                          MAY_EXEC, FILE_MMAP);
 272         return 0;
 273 }
 274
 275 /*
 276  * ima_shm_check - IPC shm and shmat create/fput a file
 277  *
 278  * Maintain the opencount for these files to prevent unnecessary
 279  * imbalance messages.
 280  */
 281 void ima_shm_check(struct file *file)
 282 {
 283         opencount_get(file);
 284         return;
 285 }
 286
 287 /**
 288  * ima_bprm_check - based on policy, collect/store measurement.
 289  * @bprm: contains the linux_binprm structure
 290  *
 291  * The OS protects against an executable file, already open for write,
 292  * from being executed in deny_write_access() and an executable file,
 293  * already open for execute, from being modified in get_write_access().
 294  * So we can be certain that what we verify and measure here is actually
 295  * what is being executed.
 296  *
 297  * Return 0 on success, an error code on failure.
 298  * (Based on the results of appraise_measurement().)
 299  */
 300 int ima_bprm_check(struct linux_binprm *bprm)
 301 {
 302         int rc;
 303
 304         rc = process_measurement(bprm->file, bprm->filename,
 305                                  MAY_EXEC, BPRM_CHECK);
 306         return 0;
 307 }
 308
 309 static int __init init_ima(void)
 310 {
 311         int error;
 312
 313         ima_iintcache_init();
 314         error = ima_init();
 315         ima_initialized = 1;
 316         return error;
 317 }
 318
 319 static void __exit cleanup_ima(void)
 320 {
 321         ima_cleanup();
 322 }
 323
 324 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 325
 326 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 327 MODULE_LICENSE("GPL");