168 lines
4.1 KiB
C
168 lines
4.1 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 const 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 (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX,
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"Invalid lockdown reason"))
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return -EPERM;
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if (kernel_locked_down >= what) {
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if (lockdown_reasons[what])
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pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
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current->comm, 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", 0644, 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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