/* System hash blacklist. * * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #define pr_fmt(fmt) "blacklist: "fmt #include <linux/module.h> #include <linux/slab.h> #include <linux/key.h> #include <linux/key-type.h> #include <linux/sched.h> #include <linux/ctype.h> #include <linux/err.h> #include <linux/seq_file.h> #include <keys/system_keyring.h> #include "blacklist.h" static struct key *blacklist_keyring; /* * The description must be a type prefix, a colon and then an even number of * hex digits. The hash is kept in the description. */ static int blacklist_vet_description(const char *desc) { int n = 0; if (*desc == ':') return -EINVAL; for (; *desc; desc++) if (*desc == ':') goto found_colon; return -EINVAL; found_colon: desc++; for (; *desc; desc++) { if (!isxdigit(*desc)) return -EINVAL; n++; } if (n == 0 || n & 1) return -EINVAL; return 0; } /* * The hash to be blacklisted is expected to be in the description. There will * be no payload. */ static int blacklist_preparse(struct key_preparsed_payload *prep) { if (prep->datalen > 0) return -EINVAL; return 0; } static void blacklist_free_preparse(struct key_preparsed_payload *prep) { } static void blacklist_describe(const struct key *key, struct seq_file *m) { seq_puts(m, key->description); } static struct key_type key_type_blacklist = { .name = "blacklist", .vet_description = blacklist_vet_description, .preparse = blacklist_preparse, .free_preparse = blacklist_free_preparse, .instantiate = generic_key_instantiate, .describe = blacklist_describe, }; /** * mark_hash_blacklisted - Add a hash to the system blacklist * @hash - The hash as a hex string with a type prefix (eg. "tbs:23aa429783") */ int mark_hash_blacklisted(const char *hash) { key_ref_t key; key = key_create_or_update(make_key_ref(blacklist_keyring, true), "blacklist", hash, NULL, 0, ((KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW), KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_BUILT_IN); if (IS_ERR(key)) { pr_err("Problem blacklisting hash (%ld)\n", PTR_ERR(key)); return PTR_ERR(key); } return 0; } /** * is_hash_blacklisted - Determine if a hash is blacklisted * @hash: The hash to be checked as a binary blob * @hash_len: The length of the binary hash * @type: Type of hash */ int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type) { key_ref_t kref; size_t type_len = strlen(type); char *buffer, *p; int ret = 0; buffer = kmalloc(type_len + 1 + hash_len * 2 + 1, GFP_KERNEL); if (!buffer) return -ENOMEM; p = memcpy(buffer, type, type_len); p += type_len; *p++ = ':'; bin2hex(p, hash, hash_len); p += hash_len * 2; *p = 0; kref = keyring_search(make_key_ref(blacklist_keyring, true), &key_type_blacklist, buffer); if (!IS_ERR(kref)) { key_ref_put(kref); ret = -EKEYREJECTED; } kfree(buffer); return ret; } EXPORT_SYMBOL_GPL(is_hash_blacklisted); /* * Initialise the blacklist */ static int __init blacklist_init(void) { const char *const *bl; if (register_key_type(&key_type_blacklist) < 0) panic("Can't allocate system blacklist key type\n"); blacklist_keyring = keyring_alloc(".blacklist", KUIDT_INIT(0), KGIDT_INIT(0), current_cred(), (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH, KEY_ALLOC_NOT_IN_QUOTA | KEY_FLAG_KEEP, NULL, NULL); if (IS_ERR(blacklist_keyring)) panic("Can't allocate system blacklist keyring\n"); for (bl = blacklist_hashes; *bl; bl++) if (mark_hash_blacklisted(*bl) < 0) pr_err("- blacklisting failed\n"); return 0; } /* * Must be initialised before we try and load the keys into the keyring. */ device_initcall(blacklist_init);