diff options
Diffstat (limited to 'certs')
| -rw-r--r-- | certs/Kconfig | 18 | ||||
| -rw-r--r-- | certs/Makefile | 6 | ||||
| -rw-r--r-- | certs/blacklist.c | 174 | ||||
| -rw-r--r-- | certs/blacklist.h | 3 | ||||
| -rw-r--r-- | certs/blacklist_hashes.c | 6 | ||||
| -rw-r--r-- | certs/blacklist_nohashes.c | 5 |
6 files changed, 212 insertions, 0 deletions
diff --git a/certs/Kconfig b/certs/Kconfig index fc5955f..6ce51ed 100644 --- a/certs/Kconfig +++ b/certs/Kconfig @@ -64,4 +64,22 @@ config SECONDARY_TRUSTED_KEYRING those keys are not blacklisted and are vouched for by a key built into the kernel or already in the secondary trusted keyring. +config SYSTEM_BLACKLIST_KEYRING + bool "Provide system-wide ring of blacklisted keys" + depends on KEYS + help + Provide a system keyring to which blacklisted keys can be added. + Keys in the keyring are considered entirely untrusted. Keys in this + keyring are used by the module signature checking to reject loading + of modules signed with a blacklisted key. + +config SYSTEM_BLACKLIST_HASH_LIST + string "Hashes to be preloaded into the system blacklist keyring" + depends on SYSTEM_BLACKLIST_KEYRING + help + If set, this option should be the filename of a list of hashes in the + form "<hash>", "<hash>", ... . This will be included into a C + wrapper to incorporate the list into the kernel. Each <hash> should + be a string of hex digits. + endmenu diff --git a/certs/Makefile b/certs/Makefile index 2773c4a..4119bb3 100644 --- a/certs/Makefile +++ b/certs/Makefile @@ -3,6 +3,12 @@ # obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o +obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist.o +ifneq ($(CONFIG_SYSTEM_BLACKLIST_HASH_LIST),"") +obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_hashes.o +else +obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_nohashes.o +endif ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y) diff --git a/certs/blacklist.c b/certs/blacklist.c new file mode 100644 index 0000000..3eddce0 --- /dev/null +++ b/certs/blacklist.c @@ -0,0 +1,174 @@ +/* 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); + +/* + * Intialise 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); diff --git a/certs/blacklist.h b/certs/blacklist.h new file mode 100644 index 0000000..150d82d --- /dev/null +++ b/certs/blacklist.h @@ -0,0 +1,3 @@ +#include <linux/kernel.h> + +extern const char __initdata *const blacklist_hashes[]; diff --git a/certs/blacklist_hashes.c b/certs/blacklist_hashes.c new file mode 100644 index 0000000..5bd449f --- /dev/null +++ b/certs/blacklist_hashes.c @@ -0,0 +1,6 @@ +#include "blacklist.h" + +const char __initdata *const blacklist_hashes[] = { +#include CONFIG_SYSTEM_BLACKLIST_HASH_LIST + , NULL +}; diff --git a/certs/blacklist_nohashes.c b/certs/blacklist_nohashes.c new file mode 100644 index 0000000..851de10 --- /dev/null +++ b/certs/blacklist_nohashes.c @@ -0,0 +1,5 @@ +#include "blacklist.h" + +const char __initdata *const blacklist_hashes[] = { + NULL +}; |
