security/integrity/iint.c

   1 /*
   2  * Copyright (C) 2008 IBM Corporation
   3  *
   4  * Authors:
   5  * Mimi Zohar <zohar@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation, version 2 of the
  10  * License.
  11  *
  12  * File: integrity_iint.c
  13  *      - implements the integrity hooks: integrity_inode_alloc,
  14  *        integrity_inode_free
  15  *      - cache integrity information associated with an inode
  16  *        using a rbtree tree.
  17  */
  18 #include <linux/slab.h>
  19 #include <linux/module.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/rbtree.h>
  22 #include <linux/file.h>
  23 #include <linux/uaccess.h>
  24 #include "integrity.h"
  25
  26 static struct rb_root integrity_iint_tree = RB_ROOT;
  27 static DEFINE_RWLOCK(integrity_iint_lock);
  28 static struct kmem_cache *iint_cache __read_mostly;
  29
  30 /*
  31  * __integrity_iint_find - return the iint associated with an inode
  32  */
  33 static struct integrity_iint_cache *__integrity_iint_find(struct inode *inode)
  34 {
  35         struct integrity_iint_cache *iint;
  36         struct rb_node *n = integrity_iint_tree.rb_node;
  37
  38         while (n) {
  39                 iint = rb_entry(n, struct integrity_iint_cache, rb_node);
  40
  41                 if (inode < iint->inode)
  42                         n = n->rb_left;
  43                 else if (inode > iint->inode)
  44                         n = n->rb_right;
  45                 else
  46                         break;
  47         }
  48         if (!n)
  49                 return NULL;
  50
  51         return iint;
  52 }
  53
  54 /*
  55  * integrity_iint_find - return the iint associated with an inode
  56  */
  57 struct integrity_iint_cache *integrity_iint_find(struct inode *inode)
  58 {
  59         struct integrity_iint_cache *iint;
  60
  61         if (!IS_IMA(inode))
  62                 return NULL;
  63
  64         read_lock(&integrity_iint_lock);
  65         iint = __integrity_iint_find(inode);
  66         read_unlock(&integrity_iint_lock);
  67
  68         return iint;
  69 }
  70
  71 static void iint_free(struct integrity_iint_cache *iint)
  72 {
  73         kfree(iint->ima_hash);
  74         iint->ima_hash = NULL;
  75         iint->version = 0;
  76         iint->flags = 0UL;
  77         iint->ima_file_status = INTEGRITY_UNKNOWN;
  78         iint->ima_mmap_status = INTEGRITY_UNKNOWN;
  79         iint->ima_bprm_status = INTEGRITY_UNKNOWN;
  80         iint->ima_read_status = INTEGRITY_UNKNOWN;
  81         iint->evm_status = INTEGRITY_UNKNOWN;
  82         kmem_cache_free(iint_cache, iint);
  83 }
  84
  85 /**
  86  * integrity_inode_get - find or allocate an iint associated with an inode
  87  * @inode: pointer to the inode
  88  * @return: allocated iint
  89  *
  90  * Caller must lock i_mutex
  91  */
  92 struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
  93 {
  94         struct rb_node **p;
  95         struct rb_node *node, *parent = NULL;
  96         struct integrity_iint_cache *iint, *test_iint;
  97
  98         iint = integrity_iint_find(inode);
  99         if (iint)
 100                 return iint;
 101
 102         iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
 103         if (!iint)
 104                 return NULL;
 105
 106         write_lock(&integrity_iint_lock);
 107
 108         p = &integrity_iint_tree.rb_node;
 109         while (*p) {
 110                 parent = *p;
 111                 test_iint = rb_entry(parent, struct integrity_iint_cache,
 112                                      rb_node);
 113                 if (inode < test_iint->inode)
 114                         p = &(*p)->rb_left;
 115                 else
 116                         p = &(*p)->rb_right;
 117         }
 118
 119         iint->inode = inode;
 120         node = &iint->rb_node;
 121         inode->i_flags |= S_IMA;
 122         rb_link_node(node, parent, p);
 123         rb_insert_color(node, &integrity_iint_tree);
 124
 125         write_unlock(&integrity_iint_lock);
 126         return iint;
 127 }
 128
 129 /**
 130  * integrity_inode_free - called on security_inode_free
 131  * @inode: pointer to the inode
 132  *
 133  * Free the integrity information(iint) associated with an inode.
 134  */
 135 void integrity_inode_free(struct inode *inode)
 136 {
 137         struct integrity_iint_cache *iint;
 138
 139         if (!IS_IMA(inode))
 140                 return;
 141
 142         write_lock(&integrity_iint_lock);
 143         iint = __integrity_iint_find(inode);
 144         rb_erase(&iint->rb_node, &integrity_iint_tree);
 145         write_unlock(&integrity_iint_lock);
 146
 147         iint_free(iint);
 148 }
 149
 150 static void init_once(void *foo)
 151 {
 152         struct integrity_iint_cache *iint = foo;
 153
 154         memset(iint, 0, sizeof(*iint));
 155         iint->version = 0;
 156         iint->flags = 0UL;
 157         iint->ima_file_status = INTEGRITY_UNKNOWN;
 158         iint->ima_mmap_status = INTEGRITY_UNKNOWN;
 159         iint->ima_bprm_status = INTEGRITY_UNKNOWN;
 160         iint->ima_read_status = INTEGRITY_UNKNOWN;
 161         iint->evm_status = INTEGRITY_UNKNOWN;
 162 }
 163
 164 static int __init integrity_iintcache_init(void)
 165 {
 166         iint_cache =
 167             kmem_cache_create("iint_cache", sizeof(struct integrity_iint_cache),
 168                               0, SLAB_PANIC, init_once);
 169         return 0;
 170 }
 171 security_initcall(integrity_iintcache_init);
 172
 173
 174 /*
 175  * integrity_kernel_read - read data from the file
 176  *
 177  * This is a function for reading file content instead of kernel_read().
 178  * It does not perform locking checks to ensure it cannot be blocked.
 179  * It does not perform security checks because it is irrelevant for IMA.
 180  *
 181  */
 182 int integrity_kernel_read(struct file *file, loff_t offset,
 183                           char *addr, unsigned long count)
 184 {
 185         mm_segment_t old_fs;
 186         char __user *buf = (char __user *)addr;
 187         ssize_t ret;
 188
 189         if (!(file->f_mode & FMODE_READ))
 190                 return -EBADF;
 191
 192         old_fs = get_fs();
 193         set_fs(get_ds());
 194         ret = __vfs_read(file, buf, count, &offset);
 195         set_fs(old_fs);
 196
 197         return ret;
 198 }
 199
 200 /*
 201  * integrity_read_file - read entire file content into the buffer
 202  *
 203  * This is function opens a file, allocates the buffer of required
 204  * size, read entire file content to the buffer and closes the file
 205  *
 206  * It is used only by init code.
 207  *
 208  */
 209 int __init integrity_read_file(const char *path, char **data)
 210 {
 211         struct file *file;
 212         loff_t size;
 213         char *buf;
 214         int rc = -EINVAL;
 215
 216         if (!path || !*path)
 217                 return -EINVAL;
 218
 219         file = filp_open(path, O_RDONLY, 0);
 220         if (IS_ERR(file)) {
 221                 rc = PTR_ERR(file);
 222                 pr_err("Unable to open file: %s (%d)", path, rc);
 223                 return rc;
 224         }
 225
 226         size = i_size_read(file_inode(file));
 227         if (size <= 0)
 228                 goto out;
 229
 230         buf = kmalloc(size, GFP_KERNEL);
 231         if (!buf) {
 232                 rc = -ENOMEM;
 233                 goto out;
 234         }
 235
 236         rc = integrity_kernel_read(file, 0, buf, size);
 237         if (rc == size) {
 238                 *data = buf;
 239         } else {
 240                 kfree(buf);
 241                 if (rc >= 0)
 242                         rc = -EIO;
 243         }
 244 out:
 245         fput(file);
 246         return rc;
 247 }
 248
 249 /*
 250  * integrity_load_keys - load integrity keys hook
 251  *
 252  * Hooks is called from init/main.c:kernel_init_freeable()
 253  * when rootfs is ready
 254  */
 255 void __init integrity_load_keys(void)
 256 {
 257         ima_load_x509();
 258         evm_load_x509();
 259 }