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167 lines
4.1 KiB
167 lines
4.1 KiB
// 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 ([email protected]) |
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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("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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