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/ima.h>
  26
  27 #include "ima.h"
  28
  29 int ima_initialized;
  30
  31 char *ima_hash = "sha1";
  32 static int __init hash_setup(char *str)
  33 {
  34         if (strncmp(str, "md5", 3) == 0)
  35                 ima_hash = "md5";
  36         return 1;
  37 }
  38 __setup("ima_hash=", hash_setup);
  39
  40 /*
  41  * ima_rdwr_violation_check
  42  *
  43  * Only invalidate the PCR for measured files:
  44  *      - Opening a file for write when already open for read,
  45  *        results in a time of measure, time of use (ToMToU) error.
  46  *      - Opening a file for read when already open for write,
  47  *        could result in a file measurement error.
  48  *
  49  */
  50 static void ima_rdwr_violation_check(struct file *file)
  51 {
  52         struct dentry *dentry = file->f_path.dentry;
  53         struct inode *inode = dentry->d_inode;
  54         fmode_t mode = file->f_mode;
  55         int rc;
  56         bool send_tomtou = false, send_writers = false;
  57
  58         if (!S_ISREG(inode->i_mode) || !ima_initialized)
  59                 return;
  60
  61         mutex_lock(&inode->i_mutex);    /* file metadata: permissions, xattr */
  62
  63         if (mode & FMODE_WRITE) {
  64                 if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
  65                         send_tomtou = true;
  66                 goto out;
  67         }
  68
  69         rc = ima_must_measure(inode, MAY_READ, FILE_CHECK);
  70         if (rc < 0)
  71                 goto out;
  72
  73         if (atomic_read(&inode->i_writecount) > 0)
  74                 send_writers = true;
  75 out:
  76         mutex_unlock(&inode->i_mutex);
  77
  78         if (send_tomtou)
  79                 ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
  80                                   "ToMToU");
  81         if (send_writers)
  82                 ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
  83                                   "open_writers");
  84 }
  85
  86 static void ima_check_last_writer(struct integrity_iint_cache *iint,
  87                                   struct inode *inode,
  88                                   struct file *file)
  89 {
  90         fmode_t mode = file->f_mode;
  91
  92         mutex_lock(&iint->mutex);
  93         if (mode & FMODE_WRITE &&
  94             atomic_read(&inode->i_writecount) == 1 &&
  95             iint->version != inode->i_version)
  96                 iint->flags &= ~IMA_MEASURED;
  97         mutex_unlock(&iint->mutex);
  98 }
  99
 100 /**
 101  * ima_file_free - called on __fput()
 102  * @file: pointer to file structure being freed
 103  *
 104  * Flag files that changed, based on i_version
 105  */
 106 void ima_file_free(struct file *file)
 107 {
 108         struct inode *inode = file->f_dentry->d_inode;
 109         struct integrity_iint_cache *iint;
 110
 111         if (!iint_initialized || !S_ISREG(inode->i_mode))
 112                 return;
 113
 114         iint = integrity_iint_find(inode);
 115         if (!iint)
 116                 return;
 117
 118         ima_check_last_writer(iint, inode, file);
 119 }
 120
 121 static int process_measurement(struct file *file, const unsigned char *filename,
 122                                int mask, int function)
 123 {
 124         struct inode *inode = file->f_dentry->d_inode;
 125         struct integrity_iint_cache *iint;
 126         int rc = 0;
 127
 128         if (!ima_initialized || !S_ISREG(inode->i_mode))
 129                 return 0;
 130
 131         rc = ima_must_measure(inode, mask, function);
 132         if (rc != 0)
 133                 return rc;
 134 retry:
 135         iint = integrity_iint_find(inode);
 136         if (!iint) {
 137                 rc = integrity_inode_alloc(inode);
 138                 if (!rc || rc == -EEXIST)
 139                         goto retry;
 140                 return rc;
 141         }
 142
 143         mutex_lock(&iint->mutex);
 144
 145         rc = iint->flags & IMA_MEASURED ? 1 : 0;
 146         if (rc != 0)
 147                 goto out;
 148
 149         rc = ima_collect_measurement(iint, file);
 150         if (!rc)
 151                 ima_store_measurement(iint, file, filename);
 152 out:
 153         mutex_unlock(&iint->mutex);
 154         return rc;
 155 }
 156
 157 /**
 158  * ima_file_mmap - based on policy, collect/store measurement.
 159  * @file: pointer to the file to be measured (May be NULL)
 160  * @prot: contains the protection that will be applied by the kernel.
 161  *
 162  * Measure files being mmapped executable based on the ima_must_measure()
 163  * policy decision.
 164  *
 165  * Return 0 on success, an error code on failure.
 166  * (Based on the results of appraise_measurement().)
 167  */
 168 int ima_file_mmap(struct file *file, unsigned long prot)
 169 {
 170         int rc;
 171
 172         if (!file)
 173                 return 0;
 174         if (prot & PROT_EXEC)
 175                 rc = process_measurement(file, file->f_dentry->d_name.name,
 176                                          MAY_EXEC, FILE_MMAP);
 177         return 0;
 178 }
 179
 180 /**
 181  * ima_bprm_check - based on policy, collect/store measurement.
 182  * @bprm: contains the linux_binprm structure
 183  *
 184  * The OS protects against an executable file, already open for write,
 185  * from being executed in deny_write_access() and an executable file,
 186  * already open for execute, from being modified in get_write_access().
 187  * So we can be certain that what we verify and measure here is actually
 188  * what is being executed.
 189  *
 190  * Return 0 on success, an error code on failure.
 191  * (Based on the results of appraise_measurement().)
 192  */
 193 int ima_bprm_check(struct linux_binprm *bprm)
 194 {
 195         int rc;
 196
 197         rc = process_measurement(bprm->file, bprm->filename,
 198                                  MAY_EXEC, BPRM_CHECK);
 199         return 0;
 200 }
 201
 202 /**
 203  * ima_path_check - based on policy, collect/store measurement.
 204  * @file: pointer to the file to be measured
 205  * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
 206  *
 207  * Measure files based on the ima_must_measure() policy decision.
 208  *
 209  * Always return 0 and audit dentry_open failures.
 210  * (Return code will be based upon measurement appraisal.)
 211  */
 212 int ima_file_check(struct file *file, int mask)
 213 {
 214         int rc;
 215
 216         ima_rdwr_violation_check(file);
 217         rc = process_measurement(file, file->f_dentry->d_name.name,
 218                                  mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
 219                                  FILE_CHECK);
 220         return 0;
 221 }
 222 EXPORT_SYMBOL_GPL(ima_file_check);
 223
 224 static int __init init_ima(void)
 225 {
 226         int error;
 227
 228         error = ima_init();
 229         ima_initialized = 1;
 230         return error;
 231 }
 232
 233 static void __exit cleanup_ima(void)
 234 {
 235         ima_cleanup();
 236 }
 237
 238 late_initcall(init_ima);        /* Start IMA after the TPM is available */
 239
 240 MODULE_DESCRIPTION("Integrity Measurement Architecture");
 241 MODULE_LICENSE("GPL");