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         ".machine",
  34 };
  35
  36 #ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
  37 #define restrict_link_to_ima restrict_link_by_digsig_builtin_and_secondary
  38 #else
  39 #define restrict_link_to_ima restrict_link_by_digsig_builtin
  40 #endif
  41
  42 static struct key *integrity_keyring_from_id(const unsigned int id)
  43 {
  44         if (id >= INTEGRITY_KEYRING_MAX)
  45                 return ERR_PTR(-EINVAL);
  46
  47         if (!keyring[id]) {
  48                 keyring[id] =
  49                         request_key(&key_type_keyring, keyring_name[id], NULL);
  50                 if (IS_ERR(keyring[id])) {
  51                         int err = PTR_ERR(keyring[id]);
  52                         pr_err("no %s keyring: %d\n", keyring_name[id], err);
  53                         keyring[id] = NULL;
  54                         return ERR_PTR(err);
  55                 }
  56         }
  57
  58         return keyring[id];
  59 }
  60
  61 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
  62                             const char *digest, int digestlen)
  63 {
  64         struct key *keyring;
  65
  66         if (siglen < 2)
  67                 return -EINVAL;
  68
  69         keyring = integrity_keyring_from_id(id);
  70         if (IS_ERR(keyring))
  71                 return PTR_ERR(keyring);
  72
  73         switch (sig[1]) {
  74         case 1:
  75                 /* v1 API expect signature without xattr type */
  76                 return digsig_verify(keyring, sig + 1, siglen - 1, digest,
  77                                      digestlen);
  78         case 2: /* regular file data hash based signature */
  79         case 3: /* struct ima_file_id data based signature */
  80                 return asymmetric_verify(keyring, sig, siglen, digest,
  81                                          digestlen);
  82         }
  83
  84         return -EOPNOTSUPP;
  85 }
  86
  87 int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
  88 {
  89         struct key *keyring;
  90
  91         keyring = integrity_keyring_from_id(id);
  92         if (IS_ERR(keyring))
  93                 return PTR_ERR(keyring);
  94
  95         return ima_modsig_verify(keyring, modsig);
  96 }
  97
  98 static int __init __integrity_init_keyring(const unsigned int id,
  99                                            key_perm_t perm,
 100                                            struct key_restriction *restriction)
 101 {
 102         const struct cred *cred = current_cred();
 103         int err = 0;
 104
 105         keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
 106                                     KGIDT_INIT(0), cred, perm,
 107                                     KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
 108         if (IS_ERR(keyring[id])) {
 109                 err = PTR_ERR(keyring[id]);
 110                 pr_info("Can't allocate %s keyring (%d)\n",
 111                         keyring_name[id], err);
 112                 keyring[id] = NULL;
 113         } else {
 114                 if (id == INTEGRITY_KEYRING_PLATFORM)
 115                         set_platform_trusted_keys(keyring[id]);
 116                 if (id == INTEGRITY_KEYRING_MACHINE && imputed_trust_enabled())
 117                         set_machine_trusted_keys(keyring[id]);
 118                 if (id == INTEGRITY_KEYRING_IMA)
 119                         load_module_cert(keyring[id]);
 120         }
 121
 122         return err;
 123 }
 124
 125 int __init integrity_init_keyring(const unsigned int id)
 126 {
 127         struct key_restriction *restriction;
 128         key_perm_t perm;
 129         int ret;
 130
 131         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
 132                 | KEY_USR_READ | KEY_USR_SEARCH;
 133
 134         if (id == INTEGRITY_KEYRING_PLATFORM ||
 135             (id == INTEGRITY_KEYRING_MACHINE &&
 136             !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
 137                 restriction = NULL;
 138                 goto out;
 139         }
 140
 141         if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
 142                 return 0;
 143
 144         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 145         if (!restriction)
 146                 return -ENOMEM;
 147
 148         if (id == INTEGRITY_KEYRING_MACHINE)
 149                 restriction->check = restrict_link_by_ca;
 150         else
 151                 restriction->check = restrict_link_to_ima;
 152
 153         /*
 154          * MOK keys can only be added through a read-only runtime services
 155          * UEFI variable during boot. No additional keys shall be allowed to
 156          * load into the machine keyring following init from userspace.
 157          */
 158         if (id != INTEGRITY_KEYRING_MACHINE)
 159                 perm |= KEY_USR_WRITE;
 160
 161 out:
 162         ret = __integrity_init_keyring(id, perm, restriction);
 163         if (ret)
 164                 kfree(restriction);
 165         return ret;
 166 }
 167
 168 static int __init integrity_add_key(const unsigned int id, const void *data,
 169                                     off_t size, key_perm_t perm)
 170 {
 171         key_ref_t key;
 172         int rc = 0;
 173
 174         if (!keyring[id])
 175                 return -EINVAL;
 176
 177         key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
 178                                    NULL, data, size, perm,
 179                                    KEY_ALLOC_NOT_IN_QUOTA);
 180         if (IS_ERR(key)) {
 181                 rc = PTR_ERR(key);
 182                 pr_err("Problem loading X.509 certificate %d\n", rc);
 183         } else {
 184                 pr_notice("Loaded X.509 cert '%s'\n",
 185                           key_ref_to_ptr(key)->description);
 186                 key_ref_put(key);
 187         }
 188
 189         return rc;
 190
 191 }
 192
 193 int __init integrity_load_x509(const unsigned int id, const char *path)
 194 {
 195         void *data = NULL;
 196         size_t size;
 197         int rc;
 198         key_perm_t perm;
 199
 200         rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
 201                                         READING_X509_CERTIFICATE);
 202         if (rc < 0) {
 203                 pr_err("Unable to open file: %s (%d)", path, rc);
 204                 return rc;
 205         }
 206         size = rc;
 207
 208         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
 209
 210         pr_info("Loading X.509 certificate: %s\n", path);
 211         rc = integrity_add_key(id, (const void *)data, size, perm);
 212
 213         vfree(data);
 214         return rc;
 215 }
 216
 217 int __init integrity_load_cert(const unsigned int id, const char *source,
 218                                const void *data, size_t len, key_perm_t perm)
 219 {
 220         if (!data)
 221                 return -EINVAL;
 222
 223         pr_info("Loading X.509 certificate: %s\n", source);
 224         return integrity_add_key(id, data, len, perm);
 225 }