security/apparmor/crypto.c

   1 /*
   2  * AppArmor security module
   3  *
   4  * This file contains AppArmor policy loading interface function definitions.
   5  *
   6  * Copyright 2013 Canonical Ltd.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation, version 2 of the
  11  * License.
  12  *
  13  * Fns to provide a checksum of policy that has been loaded this can be
  14  * compared to userspace policy compiles to check loaded policy is what
  15  * it should be.
  16  */
  17
  18 #include <crypto/hash.h>
  19
  20 #include "include/apparmor.h"
  21 #include "include/crypto.h"
  22
  23 static unsigned int apparmor_hash_size;
  24
  25 static struct crypto_shash *apparmor_tfm;
  26
  27 unsigned int aa_hash_size(void)
  28 {
  29         return apparmor_hash_size;
  30 }
  31
  32 int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
  33                          size_t len)
  34 {
  35         struct {
  36                 struct shash_desc shash;
  37                 char ctx[crypto_shash_descsize(apparmor_tfm)];
  38         } desc;
  39         int error = -ENOMEM;
  40         u32 le32_version = cpu_to_le32(version);
  41
  42         if (!apparmor_tfm)
  43                 return 0;
  44
  45         profile->hash = kzalloc(apparmor_hash_size, GFP_KERNEL);
  46         if (!profile->hash)
  47                 goto fail;
  48
  49         desc.shash.tfm = apparmor_tfm;
  50         desc.shash.flags = 0;
  51
  52         error = crypto_shash_init(&desc.shash);
  53         if (error)
  54                 goto fail;
  55         error = crypto_shash_update(&desc.shash, (u8 *) &le32_version, 4);
  56         if (error)
  57                 goto fail;
  58         error = crypto_shash_update(&desc.shash, (u8 *) start, len);
  59         if (error)
  60                 goto fail;
  61         error = crypto_shash_final(&desc.shash, profile->hash);
  62         if (error)
  63                 goto fail;
  64
  65         return 0;
  66
  67 fail:
  68         kfree(profile->hash);
  69         profile->hash = NULL;
  70
  71         return error;
  72 }
  73
  74 static int __init init_profile_hash(void)
  75 {
  76         struct crypto_shash *tfm;
  77
  78         if (!apparmor_initialized)
  79                 return 0;
  80
  81         tfm = crypto_alloc_shash("sha1", 0, CRYPTO_ALG_ASYNC);
  82         if (IS_ERR(tfm)) {
  83                 int error = PTR_ERR(tfm);
  84                 AA_ERROR("failed to setup profile sha1 hashing: %d\n", error);
  85                 return error;
  86         }
  87         apparmor_tfm = tfm;
  88         apparmor_hash_size = crypto_shash_digestsize(apparmor_tfm);
  89
  90         aa_info_message("AppArmor sha1 policy hashing enabled");
  91
  92         return 0;
  93 }
  94
  95 late_initcall(init_profile_hash);