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_TIOCSSERIAL] = "reconfiguration of serial port IO", 31 [LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters", 32 [LOCKDOWN_INTEGRITY_MAX] = "integrity", 33 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 34 }; 35 36 static enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 37 LOCKDOWN_INTEGRITY_MAX, 38 LOCKDOWN_CONFIDENTIALITY_MAX}; 39 40 /* 41 * Put the kernel into lock-down mode. 42 */ 43 static int lock_kernel_down(const char *where, enum lockdown_reason level) 44 { 45 if (kernel_locked_down >= level) 46 return -EPERM; 47 48 kernel_locked_down = level; 49 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 50 where); 51 return 0; 52 } 53 54 static int __init lockdown_param(char *level) 55 { 56 if (!level) 57 return -EINVAL; 58 59 if (strcmp(level, "integrity") == 0) 60 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 61 else if (strcmp(level, "confidentiality") == 0) 62 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 63 else 64 return -EINVAL; 65 66 return 0; 67 } 68 69 early_param("lockdown", lockdown_param); 70 71 /** 72 * lockdown_is_locked_down - Find out if the kernel is locked down 73 * @what: Tag to use in notice generated if lockdown is in effect 74 */ 75 static int lockdown_is_locked_down(enum lockdown_reason what) 76 { 77 if (kernel_locked_down >= what) { 78 if (lockdown_reasons[what]) 79 pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n", 80 lockdown_reasons[what]); 81 return -EPERM; 82 } 83 84 return 0; 85 } 86 87 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 88 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 89 }; 90 91 static int __init lockdown_lsm_init(void) 92 { 93 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 94 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 95 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 96 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 97 #endif 98 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 99 "lockdown"); 100 return 0; 101 } 102 103 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 104 loff_t *ppos) 105 { 106 char temp[80]; 107 int i, offset = 0; 108 109 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 110 enum lockdown_reason level = lockdown_levels[i]; 111 112 if (lockdown_reasons[level]) { 113 const char *label = lockdown_reasons[level]; 114 115 if (kernel_locked_down == level) 116 offset += sprintf(temp+offset, "[%s] ", label); 117 else 118 offset += sprintf(temp+offset, "%s ", label); 119 } 120 } 121 122 /* Convert the last space to a newline if needed. */ 123 if (offset > 0) 124 temp[offset-1] = '\n'; 125 126 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 127 } 128 129 static ssize_t lockdown_write(struct file *file, const char __user *buf, 130 size_t n, loff_t *ppos) 131 { 132 char *state; 133 int i, len, err = -EINVAL; 134 135 state = memdup_user_nul(buf, n); 136 if (IS_ERR(state)) 137 return PTR_ERR(state); 138 139 len = strlen(state); 140 if (len && state[len-1] == '\n') { 141 state[len-1] = '\0'; 142 len--; 143 } 144 145 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 146 enum lockdown_reason level = lockdown_levels[i]; 147 const char *label = lockdown_reasons[level]; 148 149 if (label && !strcmp(state, label)) 150 err = lock_kernel_down("securityfs", level); 151 } 152 153 kfree(state); 154 return err ? err : n; 155 } 156 157 static const struct file_operations lockdown_ops = { 158 .read = lockdown_read, 159 .write = lockdown_write, 160 }; 161 162 static int __init lockdown_secfs_init(void) 163 { 164 struct dentry *dentry; 165 166 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 167 &lockdown_ops); 168 return PTR_ERR_OR_ZERO(dentry); 169 } 170 171 core_initcall(lockdown_secfs_init); 172 173 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 174 DEFINE_EARLY_LSM(lockdown) = { 175 #else 176 DEFINE_LSM(lockdown) = { 177 #endif 178 .name = "lockdown", 179 .init = lockdown_lsm_init, 180 }; 181