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 * Initialise 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); 175