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