1 // SPDX-License-Identifier: GPL-2.0 2 /* Lock down the kernel 3 * 4 * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public Licence 9 * as published by the Free Software Foundation; either version 10 * 2 of the Licence, or (at your option) any later version. 11 */ 12 13 #include <linux/security.h> 14 #include <linux/export.h> 15 #include <linux/lsm_hooks.h> 16 17 static enum lockdown_reason kernel_locked_down; 18 19 static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 20 LOCKDOWN_INTEGRITY_MAX, 21 LOCKDOWN_CONFIDENTIALITY_MAX}; 22 23 /* 24 * Put the kernel into lock-down mode. 25 */ 26 static int lock_kernel_down(const char *where, enum lockdown_reason level) 27 { 28 if (kernel_locked_down >= level) 29 return -EPERM; 30 31 kernel_locked_down = level; 32 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 33 where); 34 return 0; 35 } 36 37 static int __init lockdown_param(char *level) 38 { 39 if (!level) 40 return -EINVAL; 41 42 if (strcmp(level, "integrity") == 0) 43 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 44 else if (strcmp(level, "confidentiality") == 0) 45 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 46 else 47 return -EINVAL; 48 49 return 0; 50 } 51 52 early_param("lockdown", lockdown_param); 53 54 /** 55 * lockdown_is_locked_down - Find out if the kernel is locked down 56 * @what: Tag to use in notice generated if lockdown is in effect 57 */ 58 static int lockdown_is_locked_down(enum lockdown_reason what) 59 { 60 if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, 61 "Invalid lockdown reason")) 62 return -EPERM; 63 64 if (kernel_locked_down >= what) { 65 if (lockdown_reasons[what]) 66 pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", 67 current->comm, lockdown_reasons[what]); 68 return -EPERM; 69 } 70 71 return 0; 72 } 73 74 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 75 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 76 }; 77 78 static int __init lockdown_lsm_init(void) 79 { 80 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 81 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 82 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 83 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 84 #endif 85 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 86 "lockdown"); 87 return 0; 88 } 89 90 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 91 loff_t *ppos) 92 { 93 char temp[80]; 94 int i, offset = 0; 95 96 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 97 enum lockdown_reason level = lockdown_levels[i]; 98 99 if (lockdown_reasons[level]) { 100 const char *label = lockdown_reasons[level]; 101 102 if (kernel_locked_down == level) 103 offset += sprintf(temp+offset, "[%s] ", label); 104 else 105 offset += sprintf(temp+offset, "%s ", label); 106 } 107 } 108 109 /* Convert the last space to a newline if needed. */ 110 if (offset > 0) 111 temp[offset-1] = '\n'; 112 113 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 114 } 115 116 static ssize_t lockdown_write(struct file *file, const char __user *buf, 117 size_t n, loff_t *ppos) 118 { 119 char *state; 120 int i, len, err = -EINVAL; 121 122 state = memdup_user_nul(buf, n); 123 if (IS_ERR(state)) 124 return PTR_ERR(state); 125 126 len = strlen(state); 127 if (len && state[len-1] == '\n') { 128 state[len-1] = '\0'; 129 len--; 130 } 131 132 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 133 enum lockdown_reason level = lockdown_levels[i]; 134 const char *label = lockdown_reasons[level]; 135 136 if (label && !strcmp(state, label)) 137 err = lock_kernel_down("securityfs", level); 138 } 139 140 kfree(state); 141 return err ? err : n; 142 } 143 144 static const struct file_operations lockdown_ops = { 145 .read = lockdown_read, 146 .write = lockdown_write, 147 }; 148 149 static int __init lockdown_secfs_init(void) 150 { 151 struct dentry *dentry; 152 153 dentry = securityfs_create_file("lockdown", 0644, NULL, NULL, 154 &lockdown_ops); 155 return PTR_ERR_OR_ZERO(dentry); 156 } 157 158 core_initcall(lockdown_secfs_init); 159 160 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 161 DEFINE_EARLY_LSM(lockdown) = { 162 #else 163 DEFINE_LSM(lockdown) = { 164 #endif 165 .name = "lockdown", 166 .init = lockdown_lsm_init, 167 }; 168