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 20 static struct key *blacklist_keyring; 21 22 /* 23 * The description must be a type prefix, a colon and then an even number of 24 * hex digits. The hash is kept in the description. 25 */ 26 static int blacklist_vet_description(const char *desc) 27 { 28 int n = 0; 29 30 if (*desc == ':') 31 return -EINVAL; 32 for (; *desc; desc++) 33 if (*desc == ':') 34 goto found_colon; 35 return -EINVAL; 36 37 found_colon: 38 desc++; 39 for (; *desc; desc++) { 40 if (!isxdigit(*desc)) 41 return -EINVAL; 42 n++; 43 } 44 45 if (n == 0 || n & 1) 46 return -EINVAL; 47 return 0; 48 } 49 50 /* 51 * The hash to be blacklisted is expected to be in the description. There will 52 * be no payload. 53 */ 54 static int blacklist_preparse(struct key_preparsed_payload *prep) 55 { 56 if (prep->datalen > 0) 57 return -EINVAL; 58 return 0; 59 } 60 61 static void blacklist_free_preparse(struct key_preparsed_payload *prep) 62 { 63 } 64 65 static void blacklist_describe(const struct key *key, struct seq_file *m) 66 { 67 seq_puts(m, key->description); 68 } 69 70 static struct key_type key_type_blacklist = { 71 .name = "blacklist", 72 .vet_description = blacklist_vet_description, 73 .preparse = blacklist_preparse, 74 .free_preparse = blacklist_free_preparse, 75 .instantiate = generic_key_instantiate, 76 .describe = blacklist_describe, 77 }; 78 79 /** 80 * mark_hash_blacklisted - Add a hash to the system blacklist 81 * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783") 82 */ 83 int mark_hash_blacklisted(const char *hash) 84 { 85 key_ref_t key; 86 87 key = key_create_or_update(make_key_ref(blacklist_keyring, true), 88 "blacklist", 89 hash, 90 NULL, 91 0, 92 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | 93 KEY_USR_VIEW), 94 KEY_ALLOC_NOT_IN_QUOTA | 95 KEY_ALLOC_BUILT_IN); 96 if (IS_ERR(key)) { 97 pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); 98 return PTR_ERR(key); 99 } 100 return 0; 101 } 102 103 /** 104 * is_hash_blacklisted - Determine if a hash is blacklisted 105 * @hash: The hash to be checked as a binary blob 106 * @hash_len: The length of the binary hash 107 * @type: Type of hash 108 */ 109 int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type) 110 { 111 key_ref_t kref; 112 size_t type_len = strlen(type); 113 char *buffer, *p; 114 int ret = 0; 115 116 buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); 117 if (!buffer) 118 return -ENOMEM; 119 p = memcpy(buffer, type, type_len); 120 p += type_len; 121 *p++ = ':'; 122 bin2hex(p, hash, hash_len); 123 p += hash_len * 2; 124 *p = 0; 125 126 kref = keyring_search(make_key_ref(blacklist_keyring, true), 127 &key_type_blacklist, buffer, false); 128 if (!IS_ERR(kref)) { 129 key_ref_put(kref); 130 ret = -EKEYREJECTED; 131 } 132 133 kfree(buffer); 134 return ret; 135 } 136 EXPORT_SYMBOL_GPL(is_hash_blacklisted); 137 138 /* 139 * Initialise the blacklist 140 */ 141 static int __init blacklist_init(void) 142 { 143 const char *const *bl; 144 145 if (register_key_type(&key_type_blacklist) < 0) 146 panic("Can't allocate system blacklist key type\n"); 147 148 blacklist_keyring = 149 keyring_alloc(".blacklist", 150 KUIDT_INIT(0), KGIDT_INIT(0), 151 current_cred(), 152 (KEY_POS_ALL & ~KEY_POS_SETATTR) | 153 KEY_USR_VIEW | KEY_USR_READ | 154 KEY_USR_SEARCH, 155 KEY_ALLOC_NOT_IN_QUOTA | 156 KEY_FLAG_KEEP, 157 NULL, NULL); 158 if (IS_ERR(blacklist_keyring)) 159 panic("Can't allocate system blacklist keyring\n"); 160 161 for (bl = blacklist_hashes; *bl; bl++) 162 if (mark_hash_blacklisted(*bl) < 0) 163 pr_err("- blacklisting failed\n"); 164 return 0; 165 } 166 167 /* 168 * Must be initialised before we try and load the keys into the keyring. 169 */ 170 device_initcall(blacklist_init); 171