// SPDX-License-Identifier: GPL-2.0 /* Lock down the kernel * * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #include <linux/security.h> #include <linux/export.h> #include <linux/lsm_hooks.h> static enum lockdown_reason kernel_locked_down; static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX}; /* * Put the kernel into lock-down mode. */ static int lock_kernel_down(const char *where, enum lockdown_reason level) { if (kernel_locked_down >= level) return -EPERM; kernel_locked_down = level; pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", where); return 0; } static int __init lockdown_param(char *level) { if (!level) return -EINVAL; if (strcmp(level, "integrity") == 0) lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); else if (strcmp(level, "confidentiality") == 0) lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); else return -EINVAL; return 0; } early_param("lockdown", lockdown_param); /** * lockdown_is_locked_down - Find out if the kernel is locked down * @what: Tag to use in notice generated if lockdown is in effect */ static int lockdown_is_locked_down(enum lockdown_reason what) { if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, "Invalid lockdown reason")) return -EPERM; if (kernel_locked_down >= what) { if (lockdown_reasons[what]) pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", current->comm, lockdown_reasons[what]); return -EPERM; } return 0; } static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), }; static int __init lockdown_lsm_init(void) { #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); #endif security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), "lockdown"); return 0; } static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) { char temp[80]; int i, offset = 0; for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { enum lockdown_reason level = lockdown_levels[i]; if (lockdown_reasons[level]) { const char *label = lockdown_reasons[level]; if (kernel_locked_down == level) offset += sprintf(temp+offset, "[%s] ", label); else offset += sprintf(temp+offset, "%s ", label); } } /* Convert the last space to a newline if needed. */ if (offset > 0) temp[offset-1] = '\n'; return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); } static ssize_t lockdown_write(struct file *file, const char __user *buf, size_t n, loff_t *ppos) { char *state; int i, len, err = -EINVAL; state = memdup_user_nul(buf, n); if (IS_ERR(state)) return PTR_ERR(state); len = strlen(state); if (len && state[len-1] == '\n') { state[len-1] = '\0'; len--; } for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { enum lockdown_reason level = lockdown_levels[i]; const char *label = lockdown_reasons[level]; if (label && !strcmp(state, label)) err = lock_kernel_down("securityfs", level); } kfree(state); return err ? err : n; } static const struct file_operations lockdown_ops = { .read = lockdown_read, .write = lockdown_write, }; static int __init lockdown_secfs_init(void) { struct dentry *dentry; dentry = securityfs_create_file("lockdown", 0644, NULL, NULL, &lockdown_ops); return PTR_ERR_OR_ZERO(dentry); } core_initcall(lockdown_secfs_init); #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY DEFINE_EARLY_LSM(lockdown) = { #else DEFINE_LSM(lockdown) = { #endif .name = "lockdown", .init = lockdown_lsm_init, };