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         }
  91
  92         return err;
  93 }
  94
  95 int __init integrity_init_keyring(const unsigned int id)
  96 {
  97         struct key_restriction *restriction;
  98         key_perm_t perm;
  99
 100         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
 101                 | KEY_USR_READ | KEY_USR_SEARCH;
 102
 103         if (id == INTEGRITY_KEYRING_PLATFORM) {
 104                 restriction = NULL;
 105                 goto out;
 106         }
 107
 108         if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
 109                 return 0;
 110
 111         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 112         if (!restriction)
 113                 return -ENOMEM;
 114
 115         restriction->check = restrict_link_to_ima;
 116         perm |= KEY_USR_WRITE;
 117
 118 out:
 119         return __integrity_init_keyring(id, perm, restriction);
 120 }
 121
 122 int __init integrity_add_key(const unsigned int id, const void *data,
 123                              off_t size, key_perm_t perm)
 124 {
 125         key_ref_t key;
 126         int rc = 0;
 127
 128         if (!keyring[id])
 129                 return -EINVAL;
 130
 131         key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
 132                                    NULL, data, size, perm,
 133                                    KEY_ALLOC_NOT_IN_QUOTA);
 134         if (IS_ERR(key)) {
 135                 rc = PTR_ERR(key);
 136                 pr_err("Problem loading X.509 certificate %d\n", rc);
 137         } else {
 138                 pr_notice("Loaded X.509 cert '%s'\n",
 139                           key_ref_to_ptr(key)->description);
 140                 key_ref_put(key);
 141         }
 142
 143         return rc;
 144
 145 }
 146
 147 int __init integrity_load_x509(const unsigned int id, const char *path)
 148 {
 149         void *data;
 150         loff_t size;
 151         int rc;
 152         key_perm_t perm;
 153
 154         rc = kernel_read_file_from_path(path, &data, &size, 0,
 155                                         READING_X509_CERTIFICATE);
 156         if (rc < 0) {
 157                 pr_err("Unable to open file: %s (%d)", path, rc);
 158                 return rc;
 159         }
 160
 161         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
 162
 163         pr_info("Loading X.509 certificate: %s\n", path);
 164         rc = integrity_add_key(id, (const void *)data, size, perm);
 165
 166         vfree(data);
 167         return rc;
 168 }
 169
 170 int __init integrity_load_cert(const unsigned int id, const char *source,
 171                                const void *data, size_t len, key_perm_t perm)
 172 {
 173         if (!data)
 174                 return -EINVAL;
 175
 176         pr_info("Loading X.509 certificate: %s\n", source);
 177         return integrity_add_key(id, data, len, perm);
 178 }