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 21 static struct key *blacklist_keyring; 22 23 /* 24 * The description must be a type prefix, a colon and then an even number of 25 * hex digits. The hash is kept in the description. 26 */ 27 static int blacklist_vet_description(const char *desc) 28 { 29 int n = 0; 30 31 if (*desc == ':') 32 return -EINVAL; 33 for (; *desc; desc++) 34 if (*desc == ':') 35 goto found_colon; 36 return -EINVAL; 37 38 found_colon: 39 desc++; 40 for (; *desc; desc++) { 41 if (!isxdigit(*desc) || isupper(*desc)) 42 return -EINVAL; 43 n++; 44 } 45 46 if (n == 0 || n & 1) 47 return -EINVAL; 48 return 0; 49 } 50 51 /* 52 * The hash to be blacklisted is expected to be in the description. There will 53 * be no payload. 54 */ 55 static int blacklist_preparse(struct key_preparsed_payload *prep) 56 { 57 if (prep->datalen > 0) 58 return -EINVAL; 59 return 0; 60 } 61 62 static void blacklist_free_preparse(struct key_preparsed_payload *prep) 63 { 64 } 65 66 static void blacklist_describe(const struct key *key, struct seq_file *m) 67 { 68 seq_puts(m, key->description); 69 } 70 71 static struct key_type key_type_blacklist = { 72 .name = "blacklist", 73 .vet_description = blacklist_vet_description, 74 .preparse = blacklist_preparse, 75 .free_preparse = blacklist_free_preparse, 76 .instantiate = generic_key_instantiate, 77 .describe = blacklist_describe, 78 }; 79 80 /** 81 * mark_hash_blacklisted - Add a hash to the system blacklist 82 * @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783") 83 */ 84 int mark_hash_blacklisted(const char *hash) 85 { 86 key_ref_t key; 87 88 key = key_create_or_update(make_key_ref(blacklist_keyring, true), 89 "blacklist", 90 hash, 91 NULL, 92 0, 93 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | 94 KEY_USR_VIEW), 95 KEY_ALLOC_NOT_IN_QUOTA | 96 KEY_ALLOC_BUILT_IN); 97 if (IS_ERR(key)) { 98 pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); 99 return PTR_ERR(key); 100 } 101 return 0; 102 } 103 104 /** 105 * is_hash_blacklisted - Determine if a hash is blacklisted 106 * @hash: The hash to be checked as a binary blob 107 * @hash_len: The length of the binary hash 108 * @type: Type of hash 109 */ 110 int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type) 111 { 112 key_ref_t kref; 113 size_t type_len = strlen(type); 114 char *buffer, *p; 115 int ret = 0; 116 117 buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); 118 if (!buffer) 119 return -ENOMEM; 120 p = memcpy(buffer, type, type_len); 121 p += type_len; 122 *p++ = ':'; 123 bin2hex(p, hash, hash_len); 124 p += hash_len * 2; 125 *p = 0; 126 127 kref = keyring_search(make_key_ref(blacklist_keyring, true), 128 &key_type_blacklist, buffer, false); 129 if (!IS_ERR(kref)) { 130 key_ref_put(kref); 131 ret = -EKEYREJECTED; 132 } 133 134 kfree(buffer); 135 return ret; 136 } 137 EXPORT_SYMBOL_GPL(is_hash_blacklisted); 138 139 int is_binary_blacklisted(const u8 *hash, size_t hash_len) 140 { 141 if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED) 142 return -EPERM; 143 144 return 0; 145 } 146 EXPORT_SYMBOL_GPL(is_binary_blacklisted); 147 148 /* 149 * Initialise the blacklist 150 */ 151 static int __init blacklist_init(void) 152 { 153 const char *const *bl; 154 155 if (register_key_type(&key_type_blacklist) < 0) 156 panic("Can't allocate system blacklist key type\n"); 157 158 blacklist_keyring = 159 keyring_alloc(".blacklist", 160 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), 161 (KEY_POS_ALL & ~KEY_POS_SETATTR) | 162 KEY_USR_VIEW | KEY_USR_READ | 163 KEY_USR_SEARCH, 164 KEY_ALLOC_NOT_IN_QUOTA | 165 KEY_ALLOC_SET_KEEP, 166 NULL, NULL); 167 if (IS_ERR(blacklist_keyring)) 168 panic("Can't allocate system blacklist keyring\n"); 169 170 for (bl = blacklist_hashes; *bl; bl++) 171 if (mark_hash_blacklisted(*bl) < 0) 172 pr_err("- blacklisting failed\n"); 173 return 0; 174 } 175 176 /* 177 * Must be initialised before we try and load the keys into the keyring. 178 */ 179 device_initcall(blacklist_init); 180