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 <keys/system_keyring.h>
  18 #include "blacklist.h"
  19 #include "common.h"
  20
  21 static struct key *blacklist_keyring;
  22
  23 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
  24 extern __initconst const u8 revocation_certificate_list[];
  25 extern __initconst const unsigned long revocation_certificate_list_size;
  26 #endif
  27
  28 /*
  29  * The description must be a type prefix, a colon and then an even number of
  30  * hex digits.  The hash is kept in the description.
  31  */
  32 static int blacklist_vet_description(const char *desc)
  33 {
  34         int n = 0;
  35
  36         if (*desc == ':')
  37                 return -EINVAL;
  38         for (; *desc; desc++)
  39                 if (*desc == ':')
  40                         goto found_colon;
  41         return -EINVAL;
  42
  43 found_colon:
  44         desc++;
  45         for (; *desc; desc++) {
  46                 if (!isxdigit(*desc))
  47                         return -EINVAL;
  48                 n++;
  49         }
  50
  51         if (n == 0 || n & 1)
  52                 return -EINVAL;
  53         return 0;
  54 }
  55
  56 /*
  57  * The hash to be blacklisted is expected to be in the description.  There will
  58  * be no payload.
  59  */
  60 static int blacklist_preparse(struct key_preparsed_payload *prep)
  61 {
  62         if (prep->datalen > 0)
  63                 return -EINVAL;
  64         return 0;
  65 }
  66
  67 static void blacklist_free_preparse(struct key_preparsed_payload *prep)
  68 {
  69 }
  70
  71 static void blacklist_describe(const struct key *key, struct seq_file *m)
  72 {
  73         seq_puts(m, key->description);
  74 }
  75
  76 static struct key_type key_type_blacklist = {
  77         .name                   = "blacklist",
  78         .vet_description        = blacklist_vet_description,
  79         .preparse               = blacklist_preparse,
  80         .free_preparse          = blacklist_free_preparse,
  81         .instantiate            = generic_key_instantiate,
  82         .describe               = blacklist_describe,
  83 };
  84
  85 /**
  86  * mark_hash_blacklisted - Add a hash to the system blacklist
  87  * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783")
  88  */
  89 int mark_hash_blacklisted(const char *hash)
  90 {
  91         key_ref_t key;
  92
  93         key = key_create_or_update(make_key_ref(blacklist_keyring, true),
  94                                    "blacklist",
  95                                    hash,
  96                                    NULL,
  97                                    0,
  98                                    ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
  99                                     KEY_USR_VIEW),
 100                                    KEY_ALLOC_NOT_IN_QUOTA |
 101                                    KEY_ALLOC_BUILT_IN);
 102         if (IS_ERR(key)) {
 103                 pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key));
 104                 return PTR_ERR(key);
 105         }
 106         return 0;
 107 }
 108
 109 /**
 110  * is_hash_blacklisted - Determine if a hash is blacklisted
 111  * @hash: The hash to be checked as a binary blob
 112  * @hash_len: The length of the binary hash
 113  * @type: Type of hash
 114  */
 115 int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
 116 {
 117         key_ref_t kref;
 118         size_t type_len = strlen(type);
 119         char *buffer, *p;
 120         int ret = 0;
 121
 122         buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);
 123         if (!buffer)
 124                 return -ENOMEM;
 125         p = memcpy(buffer, type, type_len);
 126         p += type_len;
 127         *p++ = ':';
 128         bin2hex(p, hash, hash_len);
 129         p += hash_len * 2;
 130         *p = 0;
 131
 132         kref = keyring_search(make_key_ref(blacklist_keyring, true),
 133                               &key_type_blacklist, buffer, false);
 134         if (!IS_ERR(kref)) {
 135                 key_ref_put(kref);
 136                 ret = -EKEYREJECTED;
 137         }
 138
 139         kfree(buffer);
 140         return ret;
 141 }
 142 EXPORT_SYMBOL_GPL(is_hash_blacklisted);
 143
 144 int is_binary_blacklisted(const u8 *hash, size_t hash_len)
 145 {
 146         if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
 147                 return -EPERM;
 148
 149         return 0;
 150 }
 151 EXPORT_SYMBOL_GPL(is_binary_blacklisted);
 152
 153 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
 154 /**
 155  * add_key_to_revocation_list - Add a revocation certificate to the blacklist
 156  * @data: The data blob containing the certificate
 157  * @size: The size of data blob
 158  */
 159 int add_key_to_revocation_list(const char *data, size_t size)
 160 {
 161         key_ref_t key;
 162
 163         key = key_create_or_update(make_key_ref(blacklist_keyring, true),
 164                                    "asymmetric",
 165                                    NULL,
 166                                    data,
 167                                    size,
 168                                    ((KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW),
 169                                    KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN);
 170
 171         if (IS_ERR(key)) {
 172                 pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key));
 173                 return PTR_ERR(key);
 174         } else {
 175                 pr_notice("Revoked X.509 cert '%s'\n",
 176                           key_ref_to_ptr(key)->description);
 177         }
 178
 179         return 0;
 180 }
 181
 182 /**
 183  * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked
 184  * @pkcs7: The PKCS#7 message to check
 185  */
 186 int is_key_on_revocation_list(struct pkcs7_message *pkcs7)
 187 {
 188         int ret;
 189
 190         ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);
 191
 192         if (ret == 0)
 193                 return -EKEYREJECTED;
 194
 195         return -ENOKEY;
 196 }
 197 #endif
 198
 199 /*
 200  * Initialise the blacklist
 201  */
 202 static int __init blacklist_init(void)
 203 {
 204         const char *const *bl;
 205
 206         if (register_key_type(&key_type_blacklist) < 0)
 207                 panic("Can't allocate system blacklist key type\n");
 208
 209         blacklist_keyring =
 210                 keyring_alloc(".blacklist",
 211                               KUIDT_INIT(0), KGIDT_INIT(0),
 212                               current_cred(),
 213                               (KEY_POS_ALL & ~KEY_POS_SETATTR) |
 214                               KEY_USR_VIEW | KEY_USR_READ |
 215                               KEY_USR_SEARCH,
 216                               KEY_ALLOC_NOT_IN_QUOTA |
 217                               KEY_ALLOC_SET_KEEP,
 218                               NULL, NULL);
 219         if (IS_ERR(blacklist_keyring))
 220                 panic("Can't allocate system blacklist keyring\n");
 221
 222         for (bl = blacklist_hashes; *bl; bl++)
 223                 if (mark_hash_blacklisted(*bl) < 0)
 224                         pr_err("- blacklisting failed\n");
 225         return 0;
 226 }
 227
 228 /*
 229  * Must be initialised before we try and load the keys into the keyring.
 230  */
 231 device_initcall(blacklist_init);
 232
 233 #ifdef CONFIG_SYSTEM_REVOCATION_LIST
 234 /*
 235  * Load the compiled-in list of revocation X.509 certificates.
 236  */
 237 static __init int load_revocation_certificate_list(void)
 238 {
 239         if (revocation_certificate_list_size)
 240                 pr_notice("Loading compiled-in revocation X.509 certificates\n");
 241
 242         return load_certificate_list(revocation_certificate_list, revocation_certificate_list_size,
 243                                      blacklist_keyring);
 244 }
 245 late_initcall(load_revocation_certificate_list);
 246 #endif