security/integrity/platform_certs/keyring_handler.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/err.h>
#include <linux/efi.h>
#include <linux/slab.h>
#include <keys/asymmetric-type.h>
#include <keys/system_keyring.h>
#include "../integrity.h"

static efi_guid_t efi_cert_x509_guid __initdata = EFI_CERT_X509_GUID;
static efi_guid_t efi_cert_x509_sha256_guid __initdata =
	EFI_CERT_X509_SHA256_GUID;
static efi_guid_t efi_cert_sha256_guid __initdata = EFI_CERT_SHA256_GUID;

/*
 * Blacklist a hash.
 */
static __init void uefi_blacklist_hash(const char *source, const void *data,
				       size_t len, const char *type,
				       size_t type_len)
{
	char *hash, *p;

	hash = kmalloc(type_len + len * 2 + 1, GFP_KERNEL);
	if (!hash)
		return;
	p = memcpy(hash, type, type_len);
	p += type_len;
	bin2hex(p, data, len);
	p += len * 2;
	*p = 0;

	mark_hash_blacklisted(hash);
	kfree(hash);
}

/*
 * Blacklist an X509 TBS hash.
 */
static __init void uefi_blacklist_x509_tbs(const char *source,
					   const void *data, size_t len)
{
	uefi_blacklist_hash(source, data, len, "tbs:", 4);
}

/*
 * Blacklist the hash of an executable.
 */
static __init void uefi_blacklist_binary(const char *source,
					 const void *data, size_t len)
{
	uefi_blacklist_hash(source, data, len, "bin:", 4);
}

/*
 * Return the appropriate handler for particular signature list types found in
 * the UEFI db and MokListRT tables.
 */
__init efi_element_handler_t get_handler_for_db(const efi_guid_t *sig_type)
{
	if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0)
		return add_to_platform_keyring;
	return 0;
}

/*
 * Return the appropriate handler for particular signature list types found in
 * the UEFI dbx and MokListXRT tables.
 */
__init efi_element_handler_t get_handler_for_dbx(const efi_guid_t *sig_type)
{
	if (efi_guidcmp(*sig_type, efi_cert_x509_sha256_guid) == 0)
		return uefi_blacklist_x509_tbs;
	if (efi_guidcmp(*sig_type, efi_cert_sha256_guid) == 0)
		return uefi_blacklist_binary;
	return 0;
}