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_MMIOTRACE] = "unsafe mmio", 33 [LOCKDOWN_INTEGRITY_MAX] = "integrity", 34 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 35 }; 36 37 static enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 38 LOCKDOWN_INTEGRITY_MAX, 39 LOCKDOWN_CONFIDENTIALITY_MAX}; 40 41 /* 42 * Put the kernel into lock-down mode. 43 */ 44 static int lock_kernel_down(const char *where, enum lockdown_reason level) 45 { 46 if (kernel_locked_down >= level) 47 return -EPERM; 48 49 kernel_locked_down = level; 50 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 51 where); 52 return 0; 53 } 54 55 static int __init lockdown_param(char *level) 56 { 57 if (!level) 58 return -EINVAL; 59 60 if (strcmp(level, "integrity") == 0) 61 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 62 else if (strcmp(level, "confidentiality") == 0) 63 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 64 else 65 return -EINVAL; 66 67 return 0; 68 } 69 70 early_param("lockdown", lockdown_param); 71 72 /** 73 * lockdown_is_locked_down - Find out if the kernel is locked down 74 * @what: Tag to use in notice generated if lockdown is in effect 75 */ 76 static int lockdown_is_locked_down(enum lockdown_reason what) 77 { 78 if (kernel_locked_down >= what) { 79 if (lockdown_reasons[what]) 80 pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n", 81 lockdown_reasons[what]); 82 return -EPERM; 83 } 84 85 return 0; 86 } 87 88 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 89 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 90 }; 91 92 static int __init lockdown_lsm_init(void) 93 { 94 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 95 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 96 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 97 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 98 #endif 99 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 100 "lockdown"); 101 return 0; 102 } 103 104 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 105 loff_t *ppos) 106 { 107 char temp[80]; 108 int i, offset = 0; 109 110 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 111 enum lockdown_reason level = lockdown_levels[i]; 112 113 if (lockdown_reasons[level]) { 114 const char *label = lockdown_reasons[level]; 115 116 if (kernel_locked_down == level) 117 offset += sprintf(temp+offset, "[%s] ", label); 118 else 119 offset += sprintf(temp+offset, "%s ", label); 120 } 121 } 122 123 /* Convert the last space to a newline if needed. */ 124 if (offset > 0) 125 temp[offset-1] = '\n'; 126 127 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 128 } 129 130 static ssize_t lockdown_write(struct file *file, const char __user *buf, 131 size_t n, loff_t *ppos) 132 { 133 char *state; 134 int i, len, err = -EINVAL; 135 136 state = memdup_user_nul(buf, n); 137 if (IS_ERR(state)) 138 return PTR_ERR(state); 139 140 len = strlen(state); 141 if (len && state[len-1] == '\n') { 142 state[len-1] = '\0'; 143 len--; 144 } 145 146 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 147 enum lockdown_reason level = lockdown_levels[i]; 148 const char *label = lockdown_reasons[level]; 149 150 if (label && !strcmp(state, label)) 151 err = lock_kernel_down("securityfs", level); 152 } 153 154 kfree(state); 155 return err ? err : n; 156 } 157 158 static const struct file_operations lockdown_ops = { 159 .read = lockdown_read, 160 .write = lockdown_write, 161 }; 162 163 static int __init lockdown_secfs_init(void) 164 { 165 struct dentry *dentry; 166 167 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 168 &lockdown_ops); 169 return PTR_ERR_OR_ZERO(dentry); 170 } 171 172 core_initcall(lockdown_secfs_init); 173 174 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 175 DEFINE_EARLY_LSM(lockdown) = { 176 #else 177 DEFINE_LSM(lockdown) = { 178 #endif 179 .name = "lockdown", 180 .init = lockdown_lsm_init, 181 }; 182