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 char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { 20 [LOCKDOWN_NONE] = "none", 21 [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", 22 [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", 23 [LOCKDOWN_KEXEC] = "kexec of unsigned images", 24 [LOCKDOWN_HIBERNATION] = "hibernation", 25 [LOCKDOWN_PCI_ACCESS] = "direct PCI access", 26 [LOCKDOWN_IOPORT] = "raw io port access", 27 [LOCKDOWN_MSR] = "raw MSR access", 28 [LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables", 29 [LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage", 30 [LOCKDOWN_INTEGRITY_MAX] = "integrity", 31 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 32 }; 33 34 static enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 35 LOCKDOWN_INTEGRITY_MAX, 36 LOCKDOWN_CONFIDENTIALITY_MAX}; 37 38 /* 39 * Put the kernel into lock-down mode. 40 */ 41 static int lock_kernel_down(const char *where, enum lockdown_reason level) 42 { 43 if (kernel_locked_down >= level) 44 return -EPERM; 45 46 kernel_locked_down = level; 47 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 48 where); 49 return 0; 50 } 51 52 static int __init lockdown_param(char *level) 53 { 54 if (!level) 55 return -EINVAL; 56 57 if (strcmp(level, "integrity") == 0) 58 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 59 else if (strcmp(level, "confidentiality") == 0) 60 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 61 else 62 return -EINVAL; 63 64 return 0; 65 } 66 67 early_param("lockdown", lockdown_param); 68 69 /** 70 * lockdown_is_locked_down - Find out if the kernel is locked down 71 * @what: Tag to use in notice generated if lockdown is in effect 72 */ 73 static int lockdown_is_locked_down(enum lockdown_reason what) 74 { 75 if (kernel_locked_down >= what) { 76 if (lockdown_reasons[what]) 77 pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n", 78 lockdown_reasons[what]); 79 return -EPERM; 80 } 81 82 return 0; 83 } 84 85 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 86 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 87 }; 88 89 static int __init lockdown_lsm_init(void) 90 { 91 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 92 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 93 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 94 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 95 #endif 96 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 97 "lockdown"); 98 return 0; 99 } 100 101 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 102 loff_t *ppos) 103 { 104 char temp[80]; 105 int i, offset = 0; 106 107 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 108 enum lockdown_reason level = lockdown_levels[i]; 109 110 if (lockdown_reasons[level]) { 111 const char *label = lockdown_reasons[level]; 112 113 if (kernel_locked_down == level) 114 offset += sprintf(temp+offset, "[%s] ", label); 115 else 116 offset += sprintf(temp+offset, "%s ", label); 117 } 118 } 119 120 /* Convert the last space to a newline if needed. */ 121 if (offset > 0) 122 temp[offset-1] = '\n'; 123 124 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 125 } 126 127 static ssize_t lockdown_write(struct file *file, const char __user *buf, 128 size_t n, loff_t *ppos) 129 { 130 char *state; 131 int i, len, err = -EINVAL; 132 133 state = memdup_user_nul(buf, n); 134 if (IS_ERR(state)) 135 return PTR_ERR(state); 136 137 len = strlen(state); 138 if (len && state[len-1] == '\n') { 139 state[len-1] = '\0'; 140 len--; 141 } 142 143 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 144 enum lockdown_reason level = lockdown_levels[i]; 145 const char *label = lockdown_reasons[level]; 146 147 if (label && !strcmp(state, label)) 148 err = lock_kernel_down("securityfs", level); 149 } 150 151 kfree(state); 152 return err ? err : n; 153 } 154 155 static const struct file_operations lockdown_ops = { 156 .read = lockdown_read, 157 .write = lockdown_write, 158 }; 159 160 static int __init lockdown_secfs_init(void) 161 { 162 struct dentry *dentry; 163 164 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 165 &lockdown_ops); 166 return PTR_ERR_OR_ZERO(dentry); 167 } 168 169 core_initcall(lockdown_secfs_init); 170 171 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 172 DEFINE_EARLY_LSM(lockdown) = { 173 #else 174 DEFINE_LSM(lockdown) = { 175 #endif 176 .name = "lockdown", 177 .init = lockdown_lsm_init, 178 }; 179