security/integrity/digsig.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2011 Intel Corporation
   4  *
   5  * Author:
   6  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
   7  */
   8
   9 #include <linux/err.h>
  10 #include <linux/sched.h>
  11 #include <linux/slab.h>
  12 #include <linux/cred.h>
  13 #include <linux/kernel_read_file.h>
  14 #include <linux/key-type.h>
  15 #include <linux/digsig.h>
  16 #include <linux/vmalloc.h>
  17 #include <crypto/public_key.h>
  18 #include <keys/system_keyring.h>
  19
  20 #include "integrity.h"
  21
  22 static struct key *keyring[INTEGRITY_KEYRING_MAX];
  23
  24 static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
  25 #ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
  26         "_evm",
  27         "_ima",
  28 #else
  29         ".evm",
  30         ".ima",
  31 #endif
  32         ".platform",
  33 };
  34
  35 #ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
  36 #define restrict_link_to_ima restrict_link_by_builtin_and_secondary_trusted
  37 #else
  38 #define restrict_link_to_ima restrict_link_by_builtin_trusted
  39 #endif
  40
  41 static struct key *integrity_keyring_from_id(const unsigned int id)
  42 {
  43         if (id >= INTEGRITY_KEYRING_MAX)
  44                 return ERR_PTR(-EINVAL);
  45
  46         if (!keyring[id]) {
  47                 keyring[id] =
  48                         request_key(&key_type_keyring, keyring_name[id], NULL);
  49                 if (IS_ERR(keyring[id])) {
  50                         int err = PTR_ERR(keyring[id]);
  51                         pr_err("no %s keyring: %d\n", keyring_name[id], err);
  52                         keyring[id] = NULL;
  53                         return ERR_PTR(err);
  54                 }
  55         }
  56
  57         return keyring[id];
  58 }
  59
  60 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
  61                             const char *digest, int digestlen)
  62 {
  63         struct key *keyring;
  64
  65         if (siglen < 2)
  66                 return -EINVAL;
  67
  68         keyring = integrity_keyring_from_id(id);
  69         if (IS_ERR(keyring))
  70                 return PTR_ERR(keyring);
  71
  72         switch (sig[1]) {
  73         case 1:
  74                 /* v1 API expect signature without xattr type */
  75                 return digsig_verify(keyring, sig + 1, siglen - 1, digest,
  76                                      digestlen);
  77         case 2:
  78                 return asymmetric_verify(keyring, sig, siglen, digest,
  79                                          digestlen);
  80         }
  81
  82         return -EOPNOTSUPP;
  83 }
  84
  85 int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
  86 {
  87         struct key *keyring;
  88
  89         keyring = integrity_keyring_from_id(id);
  90         if (IS_ERR(keyring))
  91                 return PTR_ERR(keyring);
  92
  93         return ima_modsig_verify(keyring, modsig);
  94 }
  95
  96 static int __init __integrity_init_keyring(const unsigned int id,
  97                                            key_perm_t perm,
  98                                            struct key_restriction *restriction)
  99 {
 100         const struct cred *cred = current_cred();
 101         int err = 0;
 102
 103         keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
 104                                     KGIDT_INIT(0), cred, perm,
 105                                     KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
 106         if (IS_ERR(keyring[id])) {
 107                 err = PTR_ERR(keyring[id]);
 108                 pr_info("Can't allocate %s keyring (%d)\n",
 109                         keyring_name[id], err);
 110                 keyring[id] = NULL;
 111         } else {
 112                 if (id == INTEGRITY_KEYRING_PLATFORM)
 113                         set_platform_trusted_keys(keyring[id]);
 114         }
 115
 116         return err;
 117 }
 118
 119 int __init integrity_init_keyring(const unsigned int id)
 120 {
 121         struct key_restriction *restriction;
 122         key_perm_t perm;
 123
 124         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
 125                 | KEY_USR_READ | KEY_USR_SEARCH;
 126
 127         if (id == INTEGRITY_KEYRING_PLATFORM) {
 128                 restriction = NULL;
 129                 goto out;
 130         }
 131
 132         if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
 133                 return 0;
 134
 135         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 136         if (!restriction)
 137                 return -ENOMEM;
 138
 139         restriction->check = restrict_link_to_ima;
 140         perm |= KEY_USR_WRITE;
 141
 142 out:
 143         return __integrity_init_keyring(id, perm, restriction);
 144 }
 145
 146 static int __init integrity_add_key(const unsigned int id, const void *data,
 147                                     off_t size, key_perm_t perm)
 148 {
 149         key_ref_t key;
 150         int rc = 0;
 151
 152         if (!keyring[id])
 153                 return -EINVAL;
 154
 155         key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
 156                                    NULL, data, size, perm,
 157                                    KEY_ALLOC_NOT_IN_QUOTA);
 158         if (IS_ERR(key)) {
 159                 rc = PTR_ERR(key);
 160                 pr_err("Problem loading X.509 certificate %d\n", rc);
 161         } else {
 162                 pr_notice("Loaded X.509 cert '%s'\n",
 163                           key_ref_to_ptr(key)->description);
 164                 key_ref_put(key);
 165         }
 166
 167         return rc;
 168
 169 }
 170
 171 int __init integrity_load_x509(const unsigned int id, const char *path)
 172 {
 173         void *data = NULL;
 174         size_t size;
 175         int rc;
 176         key_perm_t perm;
 177
 178         rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
 179                                         READING_X509_CERTIFICATE);
 180         if (rc < 0) {
 181                 pr_err("Unable to open file: %s (%d)", path, rc);
 182                 return rc;
 183         }
 184         size = rc;
 185
 186         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
 187
 188         pr_info("Loading X.509 certificate: %s\n", path);
 189         rc = integrity_add_key(id, (const void *)data, size, perm);
 190
 191         vfree(data);
 192         return rc;
 193 }
 194
 195 int __init integrity_load_cert(const unsigned int id, const char *source,
 196                                const void *data, size_t len, key_perm_t perm)
 197 {
 198         if (!data)
 199                 return -EINVAL;
 200
 201         pr_info("Loading X.509 certificate: %s\n", source);
 202         return integrity_add_key(id, data, len, perm);
 203 }