David Howells | 734114f | 2017-04-03 16:07:24 +0100 | [diff] [blame] | 1 | /* System hash blacklist. |
| 2 | * |
| 3 | * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. |
| 4 | * Written by David Howells (dhowells@redhat.com) |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or |
| 7 | * modify it under the terms of the GNU General Public Licence |
| 8 | * as published by the Free Software Foundation; either version |
| 9 | * 2 of the Licence, or (at your option) any later version. |
| 10 | */ |
| 11 | |
| 12 | #define pr_fmt(fmt) "blacklist: "fmt |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/slab.h> |
| 15 | #include <linux/key.h> |
| 16 | #include <linux/key-type.h> |
| 17 | #include <linux/sched.h> |
| 18 | #include <linux/ctype.h> |
| 19 | #include <linux/err.h> |
| 20 | #include <linux/seq_file.h> |
| 21 | #include <keys/system_keyring.h> |
| 22 | #include "blacklist.h" |
| 23 | |
| 24 | static struct key *blacklist_keyring; |
| 25 | |
| 26 | /* |
| 27 | * The description must be a type prefix, a colon and then an even number of |
| 28 | * hex digits. The hash is kept in the description. |
| 29 | */ |
| 30 | static int blacklist_vet_description(const char *desc) |
| 31 | { |
| 32 | int n = 0; |
| 33 | |
| 34 | if (*desc == ':') |
| 35 | return -EINVAL; |
| 36 | for (; *desc; desc++) |
| 37 | if (*desc == ':') |
| 38 | goto found_colon; |
| 39 | return -EINVAL; |
| 40 | |
| 41 | found_colon: |
| 42 | desc++; |
| 43 | for (; *desc; desc++) { |
| 44 | if (!isxdigit(*desc)) |
| 45 | return -EINVAL; |
| 46 | n++; |
| 47 | } |
| 48 | |
| 49 | if (n == 0 || n & 1) |
| 50 | return -EINVAL; |
| 51 | return 0; |
| 52 | } |
| 53 | |
| 54 | /* |
| 55 | * The hash to be blacklisted is expected to be in the description. There will |
| 56 | * be no payload. |
| 57 | */ |
| 58 | static int blacklist_preparse(struct key_preparsed_payload *prep) |
| 59 | { |
| 60 | if (prep->datalen > 0) |
| 61 | return -EINVAL; |
| 62 | return 0; |
| 63 | } |
| 64 | |
| 65 | static void blacklist_free_preparse(struct key_preparsed_payload *prep) |
| 66 | { |
| 67 | } |
| 68 | |
| 69 | static void blacklist_describe(const struct key *key, struct seq_file *m) |
| 70 | { |
| 71 | seq_puts(m, key->description); |
| 72 | } |
| 73 | |
| 74 | static struct key_type key_type_blacklist = { |
| 75 | .name = "blacklist", |
| 76 | .vet_description = blacklist_vet_description, |
| 77 | .preparse = blacklist_preparse, |
| 78 | .free_preparse = blacklist_free_preparse, |
| 79 | .instantiate = generic_key_instantiate, |
| 80 | .describe = blacklist_describe, |
| 81 | }; |
| 82 | |
| 83 | /** |
| 84 | * mark_hash_blacklisted - Add a hash to the system blacklist |
| 85 | * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783") |
| 86 | */ |
| 87 | int mark_hash_blacklisted(const char *hash) |
| 88 | { |
| 89 | key_ref_t key; |
| 90 | |
| 91 | key = key_create_or_update(make_key_ref(blacklist_keyring, true), |
| 92 | "blacklist", |
| 93 | hash, |
| 94 | NULL, |
| 95 | 0, |
| 96 | ((KEY_POS_ALL & ~KEY_POS_SETATTR) | |
| 97 | KEY_USR_VIEW), |
| 98 | KEY_ALLOC_NOT_IN_QUOTA | |
| 99 | KEY_ALLOC_BUILT_IN); |
| 100 | if (IS_ERR(key)) { |
| 101 | pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); |
| 102 | return PTR_ERR(key); |
| 103 | } |
| 104 | return 0; |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * is_hash_blacklisted - Determine if a hash is blacklisted |
| 109 | * @hash: The hash to be checked as a binary blob |
| 110 | * @hash_len: The length of the binary hash |
| 111 | * @type: Type of hash |
| 112 | */ |
| 113 | int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type) |
| 114 | { |
| 115 | key_ref_t kref; |
| 116 | size_t type_len = strlen(type); |
| 117 | char *buffer, *p; |
| 118 | int ret = 0; |
| 119 | |
| 120 | buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); |
| 121 | if (!buffer) |
| 122 | return -ENOMEM; |
| 123 | p = memcpy(buffer, type, type_len); |
| 124 | p += type_len; |
| 125 | *p++ = ':'; |
| 126 | bin2hex(p, hash, hash_len); |
| 127 | p += hash_len * 2; |
| 128 | *p = 0; |
| 129 | |
| 130 | kref = keyring_search(make_key_ref(blacklist_keyring, true), |
| 131 | &key_type_blacklist, buffer); |
| 132 | if (!IS_ERR(kref)) { |
| 133 | key_ref_put(kref); |
| 134 | ret = -EKEYREJECTED; |
| 135 | } |
| 136 | |
| 137 | kfree(buffer); |
| 138 | return ret; |
| 139 | } |
| 140 | EXPORT_SYMBOL_GPL(is_hash_blacklisted); |
| 141 | |
| 142 | /* |
| 143 | * Intialise the blacklist |
| 144 | */ |
| 145 | static int __init blacklist_init(void) |
| 146 | { |
| 147 | const char *const *bl; |
| 148 | |
| 149 | if (register_key_type(&key_type_blacklist) < 0) |
| 150 | panic("Can't allocate system blacklist key type\n"); |
| 151 | |
| 152 | blacklist_keyring = |
| 153 | keyring_alloc(".blacklist", |
| 154 | KUIDT_INIT(0), KGIDT_INIT(0), |
| 155 | current_cred(), |
| 156 | (KEY_POS_ALL & ~KEY_POS_SETATTR) | |
| 157 | KEY_USR_VIEW | KEY_USR_READ | |
| 158 | KEY_USR_SEARCH, |
| 159 | KEY_ALLOC_NOT_IN_QUOTA | |
| 160 | KEY_FLAG_KEEP, |
| 161 | NULL, NULL); |
| 162 | if (IS_ERR(blacklist_keyring)) |
| 163 | panic("Can't allocate system blacklist keyring\n"); |
| 164 | |
| 165 | for (bl = blacklist_hashes; *bl; bl++) |
| 166 | if (mark_hash_blacklisted(*bl) < 0) |
| 167 | pr_err("- blacklisting failed\n"); |
| 168 | return 0; |
| 169 | } |
| 170 | |
| 171 | /* |
| 172 | * Must be initialised before we try and load the keys into the keyring. |
| 173 | */ |
| 174 | device_initcall(blacklist_init); |