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![Eric Snowberg](/assets/img/avatar_default.png)
Systems booted with shim have a Forbidden Signature Database called mokx. During boot, hashes and certs contained within the mokx are loaded into the blacklist keyring. When calling verify_pkcs7_message_sig the contents of the blacklist keyring (or revocation list) are referenced when validating keys on the platform keyring. Currently, when validating against the secondary or builtin keyrings, the revocation list is not referenced. Move up the check to allow the revocation list to be used with all keyrings, including the secondary and builtin, allowing the system owner to take corrective action should a vulnerability be found within keys contained within either keyring. Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
428 lines
13 KiB
C
428 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* System trusted keyring for trusted public keys
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/export.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/cred.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/uidgid.h>
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#include <linux/verification.h>
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#include <keys/asymmetric-type.h>
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#include <keys/system_keyring.h>
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#include <crypto/pkcs7.h>
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static struct key *builtin_trusted_keys;
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#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
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static struct key *secondary_trusted_keys;
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#endif
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#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
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static struct key *machine_trusted_keys;
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#endif
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#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
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static struct key *platform_trusted_keys;
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#endif
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extern __initconst const u8 system_certificate_list[];
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extern __initconst const unsigned long system_certificate_list_size;
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extern __initconst const unsigned long module_cert_size;
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/**
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* restrict_link_by_builtin_trusted - Restrict keyring addition by built-in CA
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* @dest_keyring: Keyring being linked to.
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* @type: The type of key being added.
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* @payload: The payload of the new key.
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* @restriction_key: A ring of keys that can be used to vouch for the new cert.
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*
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* Restrict the addition of keys into a keyring based on the key-to-be-added
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* being vouched for by a key in the built in system keyring.
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*/
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int restrict_link_by_builtin_trusted(struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *restriction_key)
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{
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return restrict_link_by_signature(dest_keyring, type, payload,
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builtin_trusted_keys);
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}
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/**
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* restrict_link_by_digsig_builtin - Restrict digitalSignature key additions by the built-in keyring
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* @dest_keyring: Keyring being linked to.
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* @type: The type of key being added.
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* @payload: The payload of the new key.
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* @restriction_key: A ring of keys that can be used to vouch for the new cert.
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*
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* Restrict the addition of keys into a keyring based on the key-to-be-added
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* being vouched for by a key in the built in system keyring. The new key
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* must have the digitalSignature usage field set.
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*/
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int restrict_link_by_digsig_builtin(struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *restriction_key)
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{
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return restrict_link_by_digsig(dest_keyring, type, payload,
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builtin_trusted_keys);
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}
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#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
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/**
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* restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
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* addition by both built-in and secondary keyrings.
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* @dest_keyring: Keyring being linked to.
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* @type: The type of key being added.
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* @payload: The payload of the new key.
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* @restrict_key: A ring of keys that can be used to vouch for the new cert.
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*
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* Restrict the addition of keys into a keyring based on the key-to-be-added
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* being vouched for by a key in either the built-in or the secondary system
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* keyrings.
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*/
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int restrict_link_by_builtin_and_secondary_trusted(
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struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *restrict_key)
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{
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/* If we have a secondary trusted keyring, then that contains a link
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* through to the builtin keyring and the search will follow that link.
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*/
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if (type == &key_type_keyring &&
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dest_keyring == secondary_trusted_keys &&
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payload == &builtin_trusted_keys->payload)
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/* Allow the builtin keyring to be added to the secondary */
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return 0;
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return restrict_link_by_signature(dest_keyring, type, payload,
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secondary_trusted_keys);
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}
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/**
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* restrict_link_by_digsig_builtin_and_secondary - Restrict by digitalSignature.
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* @dest_keyring: Keyring being linked to.
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* @type: The type of key being added.
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* @payload: The payload of the new key.
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* @restrict_key: A ring of keys that can be used to vouch for the new cert.
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*
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* Restrict the addition of keys into a keyring based on the key-to-be-added
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* being vouched for by a key in either the built-in or the secondary system
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* keyrings. The new key must have the digitalSignature usage field set.
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*/
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int restrict_link_by_digsig_builtin_and_secondary(struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *restrict_key)
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{
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/* If we have a secondary trusted keyring, then that contains a link
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* through to the builtin keyring and the search will follow that link.
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*/
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if (type == &key_type_keyring &&
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dest_keyring == secondary_trusted_keys &&
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payload == &builtin_trusted_keys->payload)
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/* Allow the builtin keyring to be added to the secondary */
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return 0;
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return restrict_link_by_digsig(dest_keyring, type, payload,
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secondary_trusted_keys);
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}
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/*
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* Allocate a struct key_restriction for the "builtin and secondary trust"
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* keyring. Only for use in system_trusted_keyring_init().
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*/
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static __init struct key_restriction *get_builtin_and_secondary_restriction(void)
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{
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struct key_restriction *restriction;
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restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
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if (!restriction)
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panic("Can't allocate secondary trusted keyring restriction\n");
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if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
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restriction->check = restrict_link_by_builtin_secondary_and_machine;
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else
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restriction->check = restrict_link_by_builtin_and_secondary_trusted;
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return restriction;
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}
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/**
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* add_to_secondary_keyring - Add to secondary keyring.
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* @source: Source of key
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* @data: The blob holding the key
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* @len: The length of the data blob
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*
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* Add a key to the secondary keyring. The key must be vouched for by a key in the builtin,
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* machine or secondary keyring itself.
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*/
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void __init add_to_secondary_keyring(const char *source, const void *data, size_t len)
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{
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key_ref_t key;
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key_perm_t perm;
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perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW;
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key = key_create_or_update(make_key_ref(secondary_trusted_keys, 1),
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"asymmetric",
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NULL, data, len, perm,
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KEY_ALLOC_NOT_IN_QUOTA);
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if (IS_ERR(key)) {
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pr_err("Problem loading X.509 certificate from %s to secondary keyring %ld\n",
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source, PTR_ERR(key));
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return;
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}
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pr_notice("Loaded X.509 cert '%s'\n", key_ref_to_ptr(key)->description);
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key_ref_put(key);
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}
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#endif
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#ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
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void __init set_machine_trusted_keys(struct key *keyring)
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{
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machine_trusted_keys = keyring;
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if (key_link(secondary_trusted_keys, machine_trusted_keys) < 0)
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panic("Can't link (machine) trusted keyrings\n");
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}
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/**
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* restrict_link_by_builtin_secondary_and_machine - Restrict keyring addition.
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* @dest_keyring: Keyring being linked to.
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* @type: The type of key being added.
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* @payload: The payload of the new key.
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* @restrict_key: A ring of keys that can be used to vouch for the new cert.
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*
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* Restrict the addition of keys into a keyring based on the key-to-be-added
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* being vouched for by a key in either the built-in, the secondary, or
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* the machine keyrings.
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*/
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int restrict_link_by_builtin_secondary_and_machine(
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struct key *dest_keyring,
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const struct key_type *type,
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const union key_payload *payload,
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struct key *restrict_key)
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{
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if (machine_trusted_keys && type == &key_type_keyring &&
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dest_keyring == secondary_trusted_keys &&
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payload == &machine_trusted_keys->payload)
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/* Allow the machine keyring to be added to the secondary */
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return 0;
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return restrict_link_by_builtin_and_secondary_trusted(dest_keyring, type,
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payload, restrict_key);
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}
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#endif
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/*
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* Create the trusted keyrings
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*/
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static __init int system_trusted_keyring_init(void)
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{
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pr_notice("Initialise system trusted keyrings\n");
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builtin_trusted_keys =
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keyring_alloc(".builtin_trusted_keys",
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GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH),
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KEY_ALLOC_NOT_IN_QUOTA,
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NULL, NULL);
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if (IS_ERR(builtin_trusted_keys))
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panic("Can't allocate builtin trusted keyring\n");
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#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
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secondary_trusted_keys =
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keyring_alloc(".secondary_trusted_keys",
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GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH |
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KEY_USR_WRITE),
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KEY_ALLOC_NOT_IN_QUOTA,
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get_builtin_and_secondary_restriction(),
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NULL);
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if (IS_ERR(secondary_trusted_keys))
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panic("Can't allocate secondary trusted keyring\n");
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if (key_link(secondary_trusted_keys, builtin_trusted_keys) < 0)
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panic("Can't link trusted keyrings\n");
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#endif
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return 0;
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}
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/*
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* Must be initialised before we try and load the keys into the keyring.
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*/
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device_initcall(system_trusted_keyring_init);
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__init int load_module_cert(struct key *keyring)
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{
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if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
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return 0;
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pr_notice("Loading compiled-in module X.509 certificates\n");
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return x509_load_certificate_list(system_certificate_list,
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module_cert_size, keyring);
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}
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/*
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* Load the compiled-in list of X.509 certificates.
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*/
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static __init int load_system_certificate_list(void)
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{
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const u8 *p;
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unsigned long size;
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pr_notice("Loading compiled-in X.509 certificates\n");
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#ifdef CONFIG_MODULE_SIG
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p = system_certificate_list;
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size = system_certificate_list_size;
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#else
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p = system_certificate_list + module_cert_size;
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size = system_certificate_list_size - module_cert_size;
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#endif
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return x509_load_certificate_list(p, size, builtin_trusted_keys);
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}
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late_initcall(load_system_certificate_list);
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#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
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/**
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* verify_pkcs7_message_sig - Verify a PKCS#7-based signature on system data.
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* @data: The data to be verified (NULL if expecting internal data).
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* @len: Size of @data.
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* @pkcs7: The PKCS#7 message that is the signature.
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* @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
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* (void *)1UL for all trusted keys).
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* @usage: The use to which the key is being put.
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* @view_content: Callback to gain access to content.
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* @ctx: Context for callback.
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*/
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int verify_pkcs7_message_sig(const void *data, size_t len,
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struct pkcs7_message *pkcs7,
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struct key *trusted_keys,
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enum key_being_used_for usage,
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int (*view_content)(void *ctx,
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const void *data, size_t len,
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size_t asn1hdrlen),
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void *ctx)
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{
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int ret;
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/* The data should be detached - so we need to supply it. */
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if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
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pr_err("PKCS#7 signature with non-detached data\n");
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ret = -EBADMSG;
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goto error;
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}
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ret = pkcs7_verify(pkcs7, usage);
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if (ret < 0)
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goto error;
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ret = is_key_on_revocation_list(pkcs7);
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if (ret != -ENOKEY) {
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pr_devel("PKCS#7 key is on revocation list\n");
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goto error;
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}
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if (!trusted_keys) {
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trusted_keys = builtin_trusted_keys;
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} else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
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#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
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trusted_keys = secondary_trusted_keys;
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#else
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trusted_keys = builtin_trusted_keys;
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#endif
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} else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
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#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
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trusted_keys = platform_trusted_keys;
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#else
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trusted_keys = NULL;
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#endif
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if (!trusted_keys) {
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ret = -ENOKEY;
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pr_devel("PKCS#7 platform keyring is not available\n");
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goto error;
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}
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}
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ret = pkcs7_validate_trust(pkcs7, trusted_keys);
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if (ret < 0) {
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if (ret == -ENOKEY)
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pr_devel("PKCS#7 signature not signed with a trusted key\n");
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goto error;
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}
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if (view_content) {
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size_t asn1hdrlen;
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ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
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if (ret < 0) {
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if (ret == -ENODATA)
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pr_devel("PKCS#7 message does not contain data\n");
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goto error;
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}
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ret = view_content(ctx, data, len, asn1hdrlen);
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}
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error:
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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}
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/**
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* verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
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* @data: The data to be verified (NULL if expecting internal data).
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* @len: Size of @data.
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* @raw_pkcs7: The PKCS#7 message that is the signature.
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* @pkcs7_len: The size of @raw_pkcs7.
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* @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
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* (void *)1UL for all trusted keys).
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* @usage: The use to which the key is being put.
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* @view_content: Callback to gain access to content.
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* @ctx: Context for callback.
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*/
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int verify_pkcs7_signature(const void *data, size_t len,
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const void *raw_pkcs7, size_t pkcs7_len,
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struct key *trusted_keys,
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enum key_being_used_for usage,
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int (*view_content)(void *ctx,
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const void *data, size_t len,
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size_t asn1hdrlen),
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void *ctx)
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{
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struct pkcs7_message *pkcs7;
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int ret;
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pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
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if (IS_ERR(pkcs7))
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return PTR_ERR(pkcs7);
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ret = verify_pkcs7_message_sig(data, len, pkcs7, trusted_keys, usage,
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view_content, ctx);
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pkcs7_free_message(pkcs7);
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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}
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EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
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#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
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#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
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void __init set_platform_trusted_keys(struct key *keyring)
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{
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platform_trusted_keys = keyring;
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}
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#endif
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