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![David Howells](/assets/img/avatar_default.png)
If the kernel is locked down, require that all modules have valid signatures that we can verify. I have adjusted the errors generated: (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY), then: (a) If signatures are enforced then EKEYREJECTED is returned. (b) If there's no signature or we can't check it, but the kernel is locked down then EPERM is returned (this is then consistent with other lockdown cases). (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return the error we got. Note that the X.509 code doesn't check for key expiry as the RTC might not be valid or might not have been transferred to the kernel's clock yet. [Modified by Matthew Garrett to remove the IMA integration. This will be replaced with integration with the IMA architecture policy patchset.] Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <matthewgarrett@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Jessica Yu <jeyu@kernel.org> Signed-off-by: James Morris <jmorris@namei.org>
170 lines
4.2 KiB
C
170 lines
4.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Lock down the kernel
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*
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* Copyright (C) 2016 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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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/security.h>
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#include <linux/export.h>
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#include <linux/lsm_hooks.h>
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static enum lockdown_reason kernel_locked_down;
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static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
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[LOCKDOWN_NONE] = "none",
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[LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
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[LOCKDOWN_INTEGRITY_MAX] = "integrity",
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[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
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};
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static enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE,
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LOCKDOWN_INTEGRITY_MAX,
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LOCKDOWN_CONFIDENTIALITY_MAX};
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/*
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* Put the kernel into lock-down mode.
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*/
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static int lock_kernel_down(const char *where, enum lockdown_reason level)
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{
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if (kernel_locked_down >= level)
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return -EPERM;
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kernel_locked_down = level;
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pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n",
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where);
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return 0;
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}
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static int __init lockdown_param(char *level)
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{
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if (!level)
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return -EINVAL;
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if (strcmp(level, "integrity") == 0)
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lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX);
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else if (strcmp(level, "confidentiality") == 0)
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lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX);
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else
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return -EINVAL;
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return 0;
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}
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early_param("lockdown", lockdown_param);
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/**
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* lockdown_is_locked_down - Find out if the kernel is locked down
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* @what: Tag to use in notice generated if lockdown is in effect
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*/
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static int lockdown_is_locked_down(enum lockdown_reason what)
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{
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if (kernel_locked_down >= what) {
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if (lockdown_reasons[what])
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pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n",
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lockdown_reasons[what]);
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return -EPERM;
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}
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return 0;
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}
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static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = {
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LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
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};
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static int __init lockdown_lsm_init(void)
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{
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#if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY)
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lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX);
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#elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY)
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lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX);
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#endif
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security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks),
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"lockdown");
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return 0;
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}
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static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count,
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loff_t *ppos)
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{
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char temp[80];
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int i, offset = 0;
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for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
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enum lockdown_reason level = lockdown_levels[i];
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if (lockdown_reasons[level]) {
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const char *label = lockdown_reasons[level];
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if (kernel_locked_down == level)
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offset += sprintf(temp+offset, "[%s] ", label);
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else
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offset += sprintf(temp+offset, "%s ", label);
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}
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}
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/* Convert the last space to a newline if needed. */
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if (offset > 0)
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temp[offset-1] = '\n';
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return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
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}
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static ssize_t lockdown_write(struct file *file, const char __user *buf,
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size_t n, loff_t *ppos)
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{
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char *state;
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int i, len, err = -EINVAL;
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state = memdup_user_nul(buf, n);
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if (IS_ERR(state))
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return PTR_ERR(state);
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len = strlen(state);
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if (len && state[len-1] == '\n') {
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state[len-1] = '\0';
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len--;
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}
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for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
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enum lockdown_reason level = lockdown_levels[i];
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const char *label = lockdown_reasons[level];
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if (label && !strcmp(state, label))
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err = lock_kernel_down("securityfs", level);
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}
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kfree(state);
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return err ? err : n;
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}
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static const struct file_operations lockdown_ops = {
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.read = lockdown_read,
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.write = lockdown_write,
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};
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static int __init lockdown_secfs_init(void)
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{
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struct dentry *dentry;
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dentry = securityfs_create_file("lockdown", 0600, NULL, NULL,
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&lockdown_ops);
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return PTR_ERR_OR_ZERO(dentry);
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}
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core_initcall(lockdown_secfs_init);
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#ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY
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DEFINE_EARLY_LSM(lockdown) = {
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#else
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DEFINE_LSM(lockdown) = {
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#endif
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.name = "lockdown",
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.init = lockdown_lsm_init,
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};
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