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_KCORE] = "/proc/kcore access", 35 [LOCKDOWN_KPROBES] = "use of kprobes", 36 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 37 }; 38 39 static enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 40 LOCKDOWN_INTEGRITY_MAX, 41 LOCKDOWN_CONFIDENTIALITY_MAX}; 42 43 /* 44 * Put the kernel into lock-down mode. 45 */ 46 static int lock_kernel_down(const char *where, enum lockdown_reason level) 47 { 48 if (kernel_locked_down >= level) 49 return -EPERM; 50 51 kernel_locked_down = level; 52 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 53 where); 54 return 0; 55 } 56 57 static int __init lockdown_param(char *level) 58 { 59 if (!level) 60 return -EINVAL; 61 62 if (strcmp(level, "integrity") == 0) 63 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 64 else if (strcmp(level, "confidentiality") == 0) 65 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 66 else 67 return -EINVAL; 68 69 return 0; 70 } 71 72 early_param("lockdown", lockdown_param); 73 74 /** 75 * lockdown_is_locked_down - Find out if the kernel is locked down 76 * @what: Tag to use in notice generated if lockdown is in effect 77 */ 78 static int lockdown_is_locked_down(enum lockdown_reason what) 79 { 80 if (kernel_locked_down >= what) { 81 if (lockdown_reasons[what]) 82 pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n", 83 lockdown_reasons[what]); 84 return -EPERM; 85 } 86 87 return 0; 88 } 89 90 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 91 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 92 }; 93 94 static int __init lockdown_lsm_init(void) 95 { 96 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 97 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 98 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 99 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 100 #endif 101 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 102 "lockdown"); 103 return 0; 104 } 105 106 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 107 loff_t *ppos) 108 { 109 char temp[80]; 110 int i, offset = 0; 111 112 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 113 enum lockdown_reason level = lockdown_levels[i]; 114 115 if (lockdown_reasons[level]) { 116 const char *label = lockdown_reasons[level]; 117 118 if (kernel_locked_down == level) 119 offset += sprintf(temp+offset, "[%s] ", label); 120 else 121 offset += sprintf(temp+offset, "%s ", label); 122 } 123 } 124 125 /* Convert the last space to a newline if needed. */ 126 if (offset > 0) 127 temp[offset-1] = '\n'; 128 129 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 130 } 131 132 static ssize_t lockdown_write(struct file *file, const char __user *buf, 133 size_t n, loff_t *ppos) 134 { 135 char *state; 136 int i, len, err = -EINVAL; 137 138 state = memdup_user_nul(buf, n); 139 if (IS_ERR(state)) 140 return PTR_ERR(state); 141 142 len = strlen(state); 143 if (len && state[len-1] == '\n') { 144 state[len-1] = '\0'; 145 len--; 146 } 147 148 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 149 enum lockdown_reason level = lockdown_levels[i]; 150 const char *label = lockdown_reasons[level]; 151 152 if (label && !strcmp(state, label)) 153 err = lock_kernel_down("securityfs", level); 154 } 155 156 kfree(state); 157 return err ? err : n; 158 } 159 160 static const struct file_operations lockdown_ops = { 161 .read = lockdown_read, 162 .write = lockdown_write, 163 }; 164 165 static int __init lockdown_secfs_init(void) 166 { 167 struct dentry *dentry; 168 169 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 170 &lockdown_ops); 171 return PTR_ERR_OR_ZERO(dentry); 172 } 173 174 core_initcall(lockdown_secfs_init); 175 176 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 177 DEFINE_EARLY_LSM(lockdown) = { 178 #else 179 DEFINE_LSM(lockdown) = { 180 #endif 181 .name = "lockdown", 182 .init = lockdown_lsm_init, 183 }; 184