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_builtin_and_secondary_trusted
  38 #else
  39 #define restrict_link_to_ima restrict_link_by_builtin_trusted
  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:
  79                 return asymmetric_verify(keyring, sig, siglen, digest,
  80                                          digestlen);
  81         }
  82
  83         return -EOPNOTSUPP;
  84 }
  85
  86 int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
  87 {
  88         struct key *keyring;
  89
  90         keyring = integrity_keyring_from_id(id);
  91         if (IS_ERR(keyring))
  92                 return PTR_ERR(keyring);
  93
  94         return ima_modsig_verify(keyring, modsig);
  95 }
  96
  97 static int __init __integrity_init_keyring(const unsigned int id,
  98                                            key_perm_t perm,
  99                                            struct key_restriction *restriction)
 100 {
 101         const struct cred *cred = current_cred();
 102         int err = 0;
 103
 104         keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
 105                                     KGIDT_INIT(0), cred, perm,
 106                                     KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
 107         if (IS_ERR(keyring[id])) {
 108                 err = PTR_ERR(keyring[id]);
 109                 pr_info("Can't allocate %s keyring (%d)\n",
 110                         keyring_name[id], err);
 111                 keyring[id] = NULL;
 112         } else {
 113                 if (id == INTEGRITY_KEYRING_PLATFORM)
 114                         set_platform_trusted_keys(keyring[id]);
 115                 if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
 116                         set_machine_trusted_keys(keyring[id]);
 117                 if (id == INTEGRITY_KEYRING_IMA)
 118                         load_module_cert(keyring[id]);
 119         }
 120
 121         return err;
 122 }
 123
 124 int __init integrity_init_keyring(const unsigned int id)
 125 {
 126         struct key_restriction *restriction;
 127         key_perm_t perm;
 128
 129         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
 130                 | KEY_USR_READ | KEY_USR_SEARCH;
 131
 132         if (id == INTEGRITY_KEYRING_PLATFORM ||
 133             id == INTEGRITY_KEYRING_MACHINE) {
 134                 restriction = NULL;
 135                 goto out;
 136         }
 137
 138         if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
 139                 return 0;
 140
 141         restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
 142         if (!restriction)
 143                 return -ENOMEM;
 144
 145         restriction->check = restrict_link_to_ima;
 146
 147         /*
 148          * MOK keys can only be added through a read-only runtime services
 149          * UEFI variable during boot. No additional keys shall be allowed to
 150          * load into the machine keyring following init from userspace.
 151          */
 152         if (id != INTEGRITY_KEYRING_MACHINE)
 153                 perm |= KEY_USR_WRITE;
 154
 155 out:
 156         return __integrity_init_keyring(id, perm, restriction);
 157 }
 158
 159 static int __init integrity_add_key(const unsigned int id, const void *data,
 160                                     off_t size, key_perm_t perm)
 161 {
 162         key_ref_t key;
 163         int rc = 0;
 164
 165         if (!keyring[id])
 166                 return -EINVAL;
 167
 168         key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
 169                                    NULL, data, size, perm,
 170                                    KEY_ALLOC_NOT_IN_QUOTA);
 171         if (IS_ERR(key)) {
 172                 rc = PTR_ERR(key);
 173                 pr_err("Problem loading X.509 certificate %d\n", rc);
 174         } else {
 175                 pr_notice("Loaded X.509 cert '%s'\n",
 176                           key_ref_to_ptr(key)->description);
 177                 key_ref_put(key);
 178         }
 179
 180         return rc;
 181
 182 }
 183
 184 int __init integrity_load_x509(const unsigned int id, const char *path)
 185 {
 186         void *data = NULL;
 187         size_t size;
 188         int rc;
 189         key_perm_t perm;
 190
 191         rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
 192                                         READING_X509_CERTIFICATE);
 193         if (rc < 0) {
 194                 pr_err("Unable to open file: %s (%d)", path, rc);
 195                 return rc;
 196         }
 197         size = rc;
 198
 199         perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
 200
 201         pr_info("Loading X.509 certificate: %s\n", path);
 202         rc = integrity_add_key(id, (const void *)data, size, perm);
 203
 204         vfree(data);
 205         return rc;
 206 }
 207
 208 int __init integrity_load_cert(const unsigned int id, const char *source,
 209                                const void *data, size_t len, key_perm_t perm)
 210 {
 211         if (!data)
 212                 return -EINVAL;
 213
 214         pr_info("Loading X.509 certificate: %s\n", source);
 215         return integrity_add_key(id, data, len, perm);
 216 }