security/integrity/digsig.c

   1 /*
   2  * Copyright (C) 2011 Intel Corporation
   3  *
   4  * Author:
   5  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation, version 2 of the License.
  10  *
  11  */
  12
  13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14
  15 #include <linux/err.h>
  16 #include <linux/sched.h>
  17 #include <linux/slab.h>
  18 #include <linux/cred.h>
  19 #include <linux/key-type.h>
  20 #include <linux/digsig.h>
  21 #include <linux/vmalloc.h>
  22 #include <crypto/public_key.h>
  23 #include <keys/system_keyring.h>
  24
  25 #include "integrity.h"
  26
  27 static struct key *keyring[INTEGRITY_KEYRING_MAX];
  28
  29 static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
  30 #ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
  31         "_evm",
  32         "_ima",
  33 #else
  34         ".evm",
  35         ".ima",
  36 #endif
  37         ".platform",
  38 };
  39
  40 #ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
  41 #define restrict_link_to_ima restrict_link_by_builtin_and_secondary_trusted
  42 #else
  43 #define restrict_link_to_ima restrict_link_by_builtin_trusted
  44 #endif
  45
  46 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
  47                             const char *digest, int digestlen)
  48 {
  49         if (id >= INTEGRITY_KEYRING_MAX || siglen < 2)
  50                 return -EINVAL;
  51
  52         if (!keyring[id]) {
  53                 keyring[id] =
  54                         request_key(&key_type_keyring, keyring_name[id], NULL);
  55                 if (IS_ERR(keyring[id])) {
  56                         int err = PTR_ERR(keyring[id]);
  57                         pr_err("no %s keyring: %d\n", keyring_name[id], err);
  58                         keyring[id] = NULL;
  59                         return err;
  60                 }
  61         }
  62
  63         switch (sig[1]) {
  64         case 1:
  65                 /* v1 API expect signature without xattr type */
  66                 return digsig_verify(keyring[id], sig + 1, siglen - 1,
  67                                      digest, digestlen);
  68         case 2:
  69                 return asymmetric_verify(keyring[id], sig, siglen,
  70                                          digest, digestlen);
  71         }
  72
  73         return -EOPNOTSUPP;
  74 }
  75
  76 static int __integrity_init_keyring(const unsigned int id, key_perm_t perm,
  77                                     struct key_restriction *restriction)
  78 {
  79         const struct cred *cred = current_cred();
  80         int err = 0;
  81
  82         keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
  83                                     KGIDT_INIT(0), cred, perm,
  84                                     KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
  85         if (IS_ERR(keyring[id])) {
  86                 err = PTR_ERR(keyring[id]);
  87                 pr_info("Can't allocate %s keyring (%d)\n",
  88                         keyring_name[id], err);
  89                 keyring[id] = NULL;
  90         } else {
  91                 if (id == INTEGRITY_KEYRING_PLATFORM)
  92                         set_platform_trusted_keys(keyring[id]);
  93         }
  94
  95         return err;
  96 }
  97
  98 int __init integrity_init_keyring(const unsigned int id)
  99 {
 100         struct key_restriction *restriction;
 101         key_perm_t perm;
 102
 103         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
 104                 | KEY_USR_READ | KEY_USR_SEARCH;
 105
 106         if (id == INTEGRITY_KEYRING_PLATFORM) {
 107                 restriction = NULL;
 108                 goto out;
 109         }
 110
 111         if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
 112                 return 0;
 113
 114         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 115         if (!restriction)
 116                 return -ENOMEM;
 117
 118         restriction->check = restrict_link_to_ima;
 119         perm |= KEY_USR_WRITE;
 120
 121 out:
 122         return __integrity_init_keyring(id, perm, restriction);
 123 }
 124
 125 int __init integrity_add_key(const unsigned int id, const void *data,
 126                              off_t size, key_perm_t perm)
 127 {
 128         key_ref_t key;
 129         int rc = 0;
 130
 131         if (!keyring[id])
 132                 return -EINVAL;
 133
 134         key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
 135                                    NULL, data, size, perm,
 136                                    KEY_ALLOC_NOT_IN_QUOTA);
 137         if (IS_ERR(key)) {
 138                 rc = PTR_ERR(key);
 139                 pr_err("Problem loading X.509 certificate %d\n", rc);
 140         } else {
 141                 pr_notice("Loaded X.509 cert '%s'\n",
 142                           key_ref_to_ptr(key)->description);
 143                 key_ref_put(key);
 144         }
 145
 146         return rc;
 147
 148 }
 149
 150 int __init integrity_load_x509(const unsigned int id, const char *path)
 151 {
 152         void *data;
 153         loff_t size;
 154         int rc;
 155         key_perm_t perm;
 156
 157         rc = kernel_read_file_from_path(path, &data, &size, 0,
 158                                         READING_X509_CERTIFICATE);
 159         if (rc < 0) {
 160                 pr_err("Unable to open file: %s (%d)", path, rc);
 161                 return rc;
 162         }
 163
 164         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
 165
 166         pr_info("Loading X.509 certificate: %s\n", path);
 167         rc = integrity_add_key(id, (const void *)data, size, perm);
 168
 169         vfree(data);
 170         return rc;
 171 }
 172
 173 int __init integrity_load_cert(const unsigned int id, const char *source,
 174                                const void *data, size_t len, key_perm_t perm)
 175 {
 176         if (!data)
 177                 return -EINVAL;
 178
 179         pr_info("Loading X.509 certificate: %s\n", source);
 180         return integrity_add_key(id, data, len, perm);
 181 }