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1// SPDX-License-Identifier: GPL-2.0-or-later2/* 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: "fmt9#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/asymmetric-type.h>19#include <keys/system_keyring.h>20#include "blacklist.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 12828 29#define BLACKLIST_KEY_PERM (KEY_POS_SEARCH | KEY_POS_VIEW | \30 KEY_USR_SEARCH | KEY_USR_VIEW)31 32static const char tbs_prefix[] = "tbs";33static const char bin_prefix[] = "bin";34 35static struct key *blacklist_keyring;36 37#ifdef CONFIG_SYSTEM_REVOCATION_LIST38extern __initconst const u8 revocation_certificate_list[];39extern __initconst const unsigned long revocation_certificate_list_size;40#endif41 42/*43 * The description must be a type prefix, a colon and then an even number of44 * hex digits. The hash is kept in the description.45 */46static int blacklist_vet_description(const char *desc)47{48 int i, prefix_len, tbs_step = 0, bin_step = 0;49 50 /* The following algorithm only works if prefix lengths match. */51 BUILD_BUG_ON(sizeof(tbs_prefix) != sizeof(bin_prefix));52 prefix_len = sizeof(tbs_prefix) - 1;53 for (i = 0; *desc; desc++, i++) {54 if (*desc == ':') {55 if (tbs_step == prefix_len)56 goto found_colon;57 if (bin_step == prefix_len)58 goto found_colon;59 return -EINVAL;60 }61 if (i >= prefix_len)62 return -EINVAL;63 if (*desc == tbs_prefix[i])64 tbs_step++;65 if (*desc == bin_prefix[i])66 bin_step++;67 }68 return -EINVAL;69 70found_colon:71 desc++;72 for (i = 0; *desc && i < MAX_HASH_LEN; desc++, i++) {73 if (!isxdigit(*desc) || isupper(*desc))74 return -EINVAL;75 }76 if (*desc)77 /* The hash is greater than MAX_HASH_LEN. */78 return -ENOPKG;79 80 /* Checks for an even number of hexadecimal characters. */81 if (i == 0 || i & 1)82 return -EINVAL;83 return 0;84}85 86static int blacklist_key_instantiate(struct key *key,87 struct key_preparsed_payload *prep)88{89#ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE90 int err;91#endif92 93 /* Sets safe default permissions for keys loaded by user space. */94 key->perm = BLACKLIST_KEY_PERM;95 96 /*97 * Skips the authentication step for builtin hashes, they are not98 * signed but still trusted.99 */100 if (key->flags & (1 << KEY_FLAG_BUILTIN))101 goto out;102 103#ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE104 /*105 * Verifies the description's PKCS#7 signature against the builtin106 * trusted keyring.107 */108 err = verify_pkcs7_signature(key->description,109 strlen(key->description), prep->data, prep->datalen,110 NULL, VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);111 if (err)112 return err;113#else114 /*115 * It should not be possible to come here because the keyring doesn't116 * have KEY_USR_WRITE and the only other way to call this function is117 * for builtin hashes.118 */119 WARN_ON_ONCE(1);120 return -EPERM;121#endif122 123out:124 return generic_key_instantiate(key, prep);125}126 127static int blacklist_key_update(struct key *key,128 struct key_preparsed_payload *prep)129{130 return -EPERM;131}132 133static void blacklist_describe(const struct key *key, struct seq_file *m)134{135 seq_puts(m, key->description);136}137 138static struct key_type key_type_blacklist = {139 .name = "blacklist",140 .vet_description = blacklist_vet_description,141 .instantiate = blacklist_key_instantiate,142 .update = blacklist_key_update,143 .describe = blacklist_describe,144};145 146static char *get_raw_hash(const u8 *hash, size_t hash_len,147 enum blacklist_hash_type hash_type)148{149 size_t type_len;150 const char *type_prefix;151 char *buffer, *p;152 153 switch (hash_type) {154 case BLACKLIST_HASH_X509_TBS:155 type_len = sizeof(tbs_prefix) - 1;156 type_prefix = tbs_prefix;157 break;158 case BLACKLIST_HASH_BINARY:159 type_len = sizeof(bin_prefix) - 1;160 type_prefix = bin_prefix;161 break;162 default:163 WARN_ON_ONCE(1);164 return ERR_PTR(-EINVAL);165 }166 buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL);167 if (!buffer)168 return ERR_PTR(-ENOMEM);169 p = memcpy(buffer, type_prefix, type_len);170 p += type_len;171 *p++ = ':';172 bin2hex(p, hash, hash_len);173 p += hash_len * 2;174 *p = '\0';175 return buffer;176}177 178/**179 * mark_raw_hash_blacklisted - Add a hash to the system blacklist180 * @hash: The hash as a hex string with a type prefix (eg. "tbs:23aa429783")181 */182static int mark_raw_hash_blacklisted(const char *hash)183{184 key_ref_t key;185 186 key = key_create(make_key_ref(blacklist_keyring, true),187 "blacklist",188 hash,189 NULL,190 0,191 BLACKLIST_KEY_PERM,192 KEY_ALLOC_NOT_IN_QUOTA |193 KEY_ALLOC_BUILT_IN);194 if (IS_ERR(key)) {195 if (PTR_ERR(key) == -EEXIST)196 pr_warn("Duplicate blacklisted hash %s\n", hash);197 else198 pr_err("Problem blacklisting hash %s: %pe\n", hash, key);199 return PTR_ERR(key);200 }201 return 0;202}203 204int mark_hash_blacklisted(const u8 *hash, size_t hash_len,205 enum blacklist_hash_type hash_type)206{207 const char *buffer;208 int err;209 210 buffer = get_raw_hash(hash, hash_len, hash_type);211 if (IS_ERR(buffer))212 return PTR_ERR(buffer);213 err = mark_raw_hash_blacklisted(buffer);214 kfree(buffer);215 return err;216}217 218/**219 * is_hash_blacklisted - Determine if a hash is blacklisted220 * @hash: The hash to be checked as a binary blob221 * @hash_len: The length of the binary hash222 * @hash_type: Type of hash223 */224int is_hash_blacklisted(const u8 *hash, size_t hash_len,225 enum blacklist_hash_type hash_type)226{227 key_ref_t kref;228 const char *buffer;229 int ret = 0;230 231 buffer = get_raw_hash(hash, hash_len, hash_type);232 if (IS_ERR(buffer))233 return PTR_ERR(buffer);234 kref = keyring_search(make_key_ref(blacklist_keyring, true),235 &key_type_blacklist, buffer, false);236 if (!IS_ERR(kref)) {237 key_ref_put(kref);238 ret = -EKEYREJECTED;239 }240 241 kfree(buffer);242 return ret;243}244EXPORT_SYMBOL_GPL(is_hash_blacklisted);245 246int is_binary_blacklisted(const u8 *hash, size_t hash_len)247{248 if (is_hash_blacklisted(hash, hash_len, BLACKLIST_HASH_BINARY) ==249 -EKEYREJECTED)250 return -EPERM;251 252 return 0;253}254EXPORT_SYMBOL_GPL(is_binary_blacklisted);255 256#ifdef CONFIG_SYSTEM_REVOCATION_LIST257/**258 * add_key_to_revocation_list - Add a revocation certificate to the blacklist259 * @data: The data blob containing the certificate260 * @size: The size of data blob261 */262int add_key_to_revocation_list(const char *data, size_t size)263{264 key_ref_t key;265 266 key = key_create_or_update(make_key_ref(blacklist_keyring, true),267 "asymmetric",268 NULL,269 data,270 size,271 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH272 | KEY_USR_VIEW,273 KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN274 | KEY_ALLOC_BYPASS_RESTRICTION);275 276 if (IS_ERR(key)) {277 pr_err("Problem with revocation key (%ld)\n", PTR_ERR(key));278 return PTR_ERR(key);279 }280 281 return 0;282}283 284/**285 * is_key_on_revocation_list - Determine if the key for a PKCS#7 message is revoked286 * @pkcs7: The PKCS#7 message to check287 */288int is_key_on_revocation_list(struct pkcs7_message *pkcs7)289{290 int ret;291 292 ret = pkcs7_validate_trust(pkcs7, blacklist_keyring);293 294 if (ret == 0)295 return -EKEYREJECTED;296 297 return -ENOKEY;298}299#endif300 301static int restrict_link_for_blacklist(struct key *dest_keyring,302 const struct key_type *type, const union key_payload *payload,303 struct key *restrict_key)304{305 if (type == &key_type_blacklist)306 return 0;307 return -EOPNOTSUPP;308}309 310/*311 * Initialise the blacklist312 *313 * The blacklist_init() function is registered as an initcall via314 * device_initcall(). As a result if the blacklist_init() function fails for315 * any reason the kernel continues to execute. While cleanly returning -ENODEV316 * could be acceptable for some non-critical kernel parts, if the blacklist317 * keyring fails to load it defeats the certificate/key based deny list for318 * signed modules. If a critical piece of security functionality that users319 * expect to be present fails to initialize, panic()ing is likely the right320 * thing to do.321 */322static int __init blacklist_init(void)323{324 const char *const *bl;325 struct key_restriction *restriction;326 327 if (register_key_type(&key_type_blacklist) < 0)328 panic("Can't allocate system blacklist key type\n");329 330 restriction = kzalloc(sizeof(*restriction), GFP_KERNEL);331 if (!restriction)332 panic("Can't allocate blacklist keyring restriction\n");333 restriction->check = restrict_link_for_blacklist;334 335 blacklist_keyring =336 keyring_alloc(".blacklist",337 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),338 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |339 KEY_POS_WRITE |340 KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH341#ifdef CONFIG_SYSTEM_BLACKLIST_AUTH_UPDATE342 | KEY_USR_WRITE343#endif344 , KEY_ALLOC_NOT_IN_QUOTA |345 KEY_ALLOC_SET_KEEP,346 restriction, NULL);347 if (IS_ERR(blacklist_keyring))348 panic("Can't allocate system blacklist keyring\n");349 350 for (bl = blacklist_hashes; *bl; bl++)351 if (mark_raw_hash_blacklisted(*bl) < 0)352 pr_err("- blacklisting failed\n");353 return 0;354}355 356/*357 * Must be initialised before we try and load the keys into the keyring.358 */359device_initcall(blacklist_init);360 361#ifdef CONFIG_SYSTEM_REVOCATION_LIST362/*363 * Load the compiled-in list of revocation X.509 certificates.364 */365static __init int load_revocation_certificate_list(void)366{367 if (revocation_certificate_list_size)368 pr_notice("Loading compiled-in revocation X.509 certificates\n");369 370 return x509_load_certificate_list(revocation_certificate_list,371 revocation_certificate_list_size,372 blacklist_keyring);373}374late_initcall(load_revocation_certificate_list);375#endif376