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 #include "common.h" 21 22 /* 23 * According to crypto/asymmetric_keys/x509_cert_parser.c:x509_note_pkey_algo(), 24 * the size of the currently longest supported hash algorithm is 512 bits, 25 * which translates into 128 hex characters. 26 */ 27 #define MAX_HASH_LEN 128 28 29 static const char tbs_prefix[] = "tbs"; 30 static const char bin_prefix[] = "bin"; 31 32 static struct key *blacklist_keyring; 33 34 #ifdef CONFIG_SYSTEM_REVOCATION_LIST 35 extern __initconst const u8 revocation_certificate_list[]; 36 extern __initconst const unsigned long revocation_certificate_list_size; 37 #endif 38 39 /* 40 * The description must be a type prefix, a colon and then an even number of 41 * hex digits. The hash is kept in the description. 42 */ 43 static int blacklist_vet_description(const char *desc) 44 { 45 int i, prefix_len, tbs_step = 0, bin_step = 0; 46 47 /* The following algorithm only works if prefix lengths match. */ 48 BUILD_BUG_ON(sizeof(tbs_prefix) != sizeof(bin_prefix)); 49 prefix_len = sizeof(tbs_prefix) - 1; 50 for (i = 0; *desc; desc++, i++) { 51 if (*desc == ':') { 52 if (tbs_step == prefix_len) 53 goto found_colon; 54 if (bin_step == prefix_len) 55 goto found_colon; 56 return -EINVAL; 57 } 58 if (i >= prefix_len) 59 return -EINVAL; 60 if (*desc == tbs_prefix[i]) 61 tbs_step++; 62 if (*desc == bin_prefix[i]) 63 bin_step++; 64 } 65 return -EINVAL; 66 67 found_colon: 68 desc++; 69 for (i = 0; *desc && i < MAX_HASH_LEN; desc++, i++) { 70 if (!isxdigit(*desc) || isupper(*desc)) 71 return -EINVAL; 72 } 73 if (*desc) 74 /* The hash is greater than MAX_HASH_LEN. */ 75 return -ENOPKG; 76 77 /* Checks for an even number of hexadecimal characters. */ 78 if (i == 0 || i & 1) 79 return -EINVAL; 80 return 0; 81 } 82 83 /* 84 * The hash to be blacklisted is expected to be in the description. There will 85 * be no payload. 86 */ 87 static int blacklist_preparse(struct key_preparsed_payload *prep) 88 { 89 if (prep->datalen > 0) 90 return -EINVAL; 91 return 0; 92 } 93 94 static void blacklist_free_preparse(struct key_preparsed_payload *prep) 95 { 96 } 97 98 static void blacklist_describe(const struct key *key, struct seq_file *m) 99 { 100 seq_puts(m, key->description); 101 } 102 103 static struct key_type key_type_blacklist = { 104 .name = "blacklist", 105 .vet_description = blacklist_vet_description, 106 .preparse = blacklist_preparse, 107 .free_preparse = blacklist_free_preparse, 108 .instantiate = generic_key_instantiate, 109 .describe = blacklist_describe, 110 }; 111 112 static char *get_raw_hash(const u8 *hash, size_t hash_len, 113 enum blacklist_hash_type hash_type) 114 { 115 size_t type_len; 116 const char *type_prefix; 117 char *buffer, *p; 118 119 switch (hash_type) { 120 case BLACKLIST_HASH_X509_TBS: 121 type_len = sizeof(tbs_prefix) - 1; 122 type_prefix = tbs_prefix; 123 break; 124 case BLACKLIST_HASH_BINARY: 125 type_len = sizeof(bin_prefix) - 1; 126 type_prefix = bin_prefix; 127 break; 128 default: 129 WARN_ON_ONCE(1); 130 return ERR_PTR(-EINVAL); 131 } 132 buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); 133 if (!buffer) 134 return ERR_PTR(-ENOMEM); 135 p = memcpy(buffer, type_prefix, type_len); 136 p += type_len; 137 *p++ = ':'; 138 bin2hex(p, hash, hash_len); 139 p += hash_len * 2; 140 *p = '\0'; 141 return buffer; 142 } 143 144 /** 145 * mark_raw_hash_blacklisted - Add a hash to the system blacklist 146 * @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783") 147 */ 148 static int mark_raw_hash_blacklisted(const char *hash) 149 { 150 key_ref_t key; 151 152 key = key_create_or_update(make_key_ref(blacklist_keyring, true), 153 "blacklist", 154 hash, 155 NULL, 156 0, 157 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | 158 KEY_USR_VIEW), 159 KEY_ALLOC_NOT_IN_QUOTA | 160 KEY_ALLOC_BUILT_IN); 161 if (IS_ERR(key)) { 162 pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); 163 return PTR_ERR(key); 164 } 165 return 0; 166 } 167 168 int mark_hash_blacklisted(const u8 *hash, size_t hash_len, 169 enum blacklist_hash_type hash_type) 170 { 171 const char *buffer; 172 int err; 173 174 buffer = get_raw_hash(hash, hash_len, hash_type); 175 if (IS_ERR(buffer)) 176 return PTR_ERR(buffer); 177 err = mark_raw_hash_blacklisted(buffer); 178 kfree(buffer); 179 return err; 180 } 181 182 /** 183 * is_hash_blacklisted - Determine if a hash is blacklisted 184 * @hash: The hash to be checked as a binary blob 185 * @hash_len: The length of the binary hash 186 * @hash_type: Type of hash 187 */ 188 int is_hash_blacklisted(const u8 *hash, size_t hash_len, 189 enum blacklist_hash_type hash_type) 190 { 191 key_ref_t kref; 192 const char *buffer; 193 int ret = 0; 194 195 buffer = get_raw_hash(hash, hash_len, hash_type); 196 if (IS_ERR(buffer)) 197 return PTR_ERR(buffer); 198 kref = keyring_search(make_key_ref(blacklist_keyring, true), 199 &key_type_blacklist, buffer, false); 200 if (!IS_ERR(kref)) { 201 key_ref_put(kref); 202 ret = -EKEYREJECTED; 203 } 204 205 kfree(buffer); 206 return ret; 207 } 208 EXPORT_SYMBOL_GPL(is_hash_blacklisted); 209 210 int is_binary_blacklisted(const u8 *hash, size_t hash_len) 211 { 212 if (is_hash_blacklisted(hash, hash_len, BLACKLIST_HASH_BINARY) == 213 -EKEYREJECTED) 214 return -EPERM; 215 216 return 0; 217 } 218 EXPORT_SYMBOL_GPL(is_binary_blacklisted); 219 220 #ifdef CONFIG_SYSTEM_REVOCATION_LIST 221 /** 222 * add_key_to_revocation_list - Add a revocation certificate to the blacklist 223 * @data: The data blob containing the certificate 224 * @size: The size of data blob 225 */ 226 int add_key_to_revocation_list(const char *data, size_t size) 227 { 228 key_ref_t key; 229 230 key = key_create_or_update(make_key_ref(blacklist_keyring, true), 231 "asymmetric", 232 NULL, 233 data, 234 size, 235 ((KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW), 236 KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN); 237 238 if (IS_ERR(key)) { 239 pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key)); 240 return PTR_ERR(key); 241 } 242 243 return 0; 244 } 245 246 /** 247 * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked 248 * @pkcs7: The PKCS#7 message to check 249 */ 250 int is_key_on_revocation_list(struct pkcs7_message *pkcs7) 251 { 252 int ret; 253 254 ret = pkcs7_validate_trust(pkcs7, blacklist_keyring); 255 256 if (ret == 0) 257 return -EKEYREJECTED; 258 259 return -ENOKEY; 260 } 261 #endif 262 263 /* 264 * Initialise the blacklist 265 */ 266 static int __init blacklist_init(void) 267 { 268 const char *const *bl; 269 270 if (register_key_type(&key_type_blacklist) < 0) 271 panic("Can't allocate system blacklist key type\n"); 272 273 blacklist_keyring = 274 keyring_alloc(".blacklist", 275 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), 276 (KEY_POS_ALL & ~KEY_POS_SETATTR) | 277 KEY_USR_VIEW | KEY_USR_READ | 278 KEY_USR_SEARCH, 279 KEY_ALLOC_NOT_IN_QUOTA | 280 KEY_ALLOC_SET_KEEP, 281 NULL, NULL); 282 if (IS_ERR(blacklist_keyring)) 283 panic("Can't allocate system blacklist keyring\n"); 284 285 for (bl = blacklist_hashes; *bl; bl++) 286 if (mark_raw_hash_blacklisted(*bl) < 0) 287 pr_err("- blacklisting failed\n"); 288 return 0; 289 } 290 291 /* 292 * Must be initialised before we try and load the keys into the keyring. 293 */ 294 device_initcall(blacklist_init); 295 296 #ifdef CONFIG_SYSTEM_REVOCATION_LIST 297 /* 298 * Load the compiled-in list of revocation X.509 certificates. 299 */ 300 static __init int load_revocation_certificate_list(void) 301 { 302 if (revocation_certificate_list_size) 303 pr_notice("Loading compiled-in revocation X.509 certificates\n"); 304 305 return load_certificate_list(revocation_certificate_list, revocation_certificate_list_size, 306 blacklist_keyring); 307 } 308 late_initcall(load_revocation_certificate_list); 309 #endif 310