certs/blacklist.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* System hash blacklist.
   3  *
   4  * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #define pr_fmt(fmt) "blacklist: "fmt
   9 #include <linux/module.h>
  10 #include <linux/slab.h>
  11 #include <linux/key.h>
  12 #include <linux/key-type.h>
  13 #include <linux/sched.h>
  14 #include <linux/ctype.h>
  15 #include <linux/err.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/uidgid.h>
  18 #include <keys/system_keyring.h>
  19 #include "blacklist.h"
  20 #include "common.h"
  21
  22 static struct key *blacklist_keyring;
  23
  24 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
  25 extern __initconst const u8 revocation_certificate_list[];
  26 extern __initconst const unsigned long revocation_certificate_list_size;
  27 #endif
  28
  29 /*
  30  * The description must be a type prefix, a colon and then an even number of
  31  * hex digits.  The hash is kept in the description.
  32  */
  33 static int blacklist_vet_description(const char *desc)
  34 {
  35         int n = 0;
  36
  37         if (*desc == ':')
  38                 return -EINVAL;
  39         for (; *desc; desc++)
  40                 if (*desc == ':')
  41                         goto found_colon;
  42         return -EINVAL;
  43
  44 found_colon:
  45         desc++;
  46         for (; *desc; desc++) {
  47                 if (!isxdigit(*desc) || isupper(*desc))
  48                         return -EINVAL;
  49                 n++;
  50         }
  51
  52         if (n == 0 || n & 1)
  53                 return -EINVAL;
  54         return 0;
  55 }
  56
  57 /*
  58  * The hash to be blacklisted is expected to be in the description.  There will
  59  * be no payload.
  60  */
  61 static int blacklist_preparse(struct key_preparsed_payload *prep)
  62 {
  63         if (prep->datalen > 0)
  64                 return -EINVAL;
  65         return 0;
  66 }
  67
  68 static void blacklist_free_preparse(struct key_preparsed_payload *prep)
  69 {
  70 }
  71
  72 static void blacklist_describe(const struct key *key, struct seq_file *m)
  73 {
  74         seq_puts(m, key->description);
  75 }
  76
  77 static struct key_type key_type_blacklist = {
  78         .name                   = "blacklist",
  79         .vet_description        = blacklist_vet_description,
  80         .preparse               = blacklist_preparse,
  81         .free_preparse          = blacklist_free_preparse,
  82         .instantiate            = generic_key_instantiate,
  83         .describe               = blacklist_describe,
  84 };
  85
  86 /**
  87  * mark_hash_blacklisted - Add a hash to the system blacklist
  88  * @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
  89  */
  90 int mark_hash_blacklisted(const char *hash)
  91 {
  92         key_ref_t key;
  93
  94         key = key_create_or_update(make_key_ref(blacklist_keyring, true),
  95                                    "blacklist",
  96                                    hash,
  97                                    NULL,
  98                                    0,
  99                                    ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
 100                                     KEY_USR_VIEW),
 101                                    KEY_ALLOC_NOT_IN_QUOTA |
 102                                    KEY_ALLOC_BUILT_IN);
 103         if (IS_ERR(key)) {
 104                 pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key));
 105                 return PTR_ERR(key);
 106         }
 107         return 0;
 108 }
 109
 110 /**
 111  * is_hash_blacklisted - Determine if a hash is blacklisted
 112  * @hash: The hash to be checked as a binary blob
 113  * @hash_len: The length of the binary hash
 114  * @type: Type of hash
 115  */
 116 int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
 117 {
 118         key_ref_t kref;
 119         size_t type_len = strlen(type);
 120         char *buffer, *p;
 121         int ret = 0;
 122
 123         buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
 124         if (!buffer)
 125                 return -ENOMEM;
 126         p = memcpy(buffer, type, type_len);
 127         p += type_len;
 128         *p++ = ':';
 129         bin2hex(p, hash, hash_len);
 130         p += hash_len * 2;
 131         *p = 0;
 132
 133         kref = keyring_search(make_key_ref(blacklist_keyring, true),
 134                               &key_type_blacklist, buffer, false);
 135         if (!IS_ERR(kref)) {
 136                 key_ref_put(kref);
 137                 ret = -EKEYREJECTED;
 138         }
 139
 140         kfree(buffer);
 141         return ret;
 142 }
 143 EXPORT_SYMBOL_GPL(is_hash_blacklisted);
 144
 145 int is_binary_blacklisted(const u8 *hash, size_t hash_len)
 146 {
 147         if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
 148                 return -EPERM;
 149
 150         return 0;
 151 }
 152 EXPORT_SYMBOL_GPL(is_binary_blacklisted);
 153
 154 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
 155 /**
 156  * add_key_to_revocation_list - Add a revocation certificate to the blacklist
 157  * @data: The data blob containing the certificate
 158  * @size: The size of data blob
 159  */
 160 int add_key_to_revocation_list(const char *data, size_t size)
 161 {
 162         key_ref_t key;
 163
 164         key = key_create_or_update(make_key_ref(blacklist_keyring, true),
 165                                    "asymmetric",
 166                                    NULL,
 167                                    data,
 168                                    size,
 169                                    ((KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW),
 170                                    KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN);
 171
 172         if (IS_ERR(key)) {
 173                 pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key));
 174                 return PTR_ERR(key);
 175         }
 176
 177         return 0;
 178 }
 179
 180 /**
 181  * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked
 182  * @pkcs7: The PKCS#7 message to check
 183  */
 184 int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
 185 {
 186         int ret;
 187
 188         ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
 189
 190         if (ret == 0)
 191                 return -EKEYREJECTED;
 192
 193         return -ENOKEY;
 194 }
 195 #endif
 196
 197 /*
 198  * Initialise the blacklist
 199  */
 200 static int __init blacklist_init(void)
 201 {
 202         const char *const *bl;
 203
 204         if (register_key_type(&key_type_blacklist) < 0)
 205                 panic("Can't allocate system blacklist key type\n");
 206
 207         blacklist_keyring =
 208                 keyring_alloc(".blacklist",
 209                               GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
 210                               (KEY_POS_ALL & ~KEY_POS_SETATTR) |
 211                               KEY_USR_VIEW | KEY_USR_READ |
 212                               KEY_USR_SEARCH,
 213                               KEY_ALLOC_NOT_IN_QUOTA |
 214                               KEY_ALLOC_SET_KEEP,
 215                               NULL, NULL);
 216         if (IS_ERR(blacklist_keyring))
 217                 panic("Can't allocate system blacklist keyring\n");
 218
 219         for (bl = blacklist_hashes; *bl; bl++)
 220                 if (mark_hash_blacklisted(*bl) < 0)
 221                         pr_err("- blacklisting failed\n");
 222         return 0;
 223 }
 224
 225 /*
 226  * Must be initialised before we try and load the keys into the keyring.
 227  */
 228 device_initcall(blacklist_init);
 229
 230 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
 231 /*
 232  * Load the compiled-in list of revocation X.509 certificates.
 233  */
 234 static __init int load_revocation_certificate_list(void)
 235 {
 236         if (revocation_certificate_list_size)
 237                 pr_notice("Loading compiled-in revocation X.509 certificates\n");
 238
 239         return load_certificate_list(revocation_certificate_list, revocation_certificate_list_size,
 240                                      blacklist_keyring);
 241 }
 242 late_initcall(load_revocation_certificate_list);
 243 #endif