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_DEBUGFS] = "debugfs access", 34 [LOCKDOWN_INTEGRITY_MAX] = "integrity", 35 [LOCKDOWN_KCORE] = "/proc/kcore access", 36 [LOCKDOWN_KPROBES] = "use of kprobes", 37 [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", 38 [LOCKDOWN_PERF] = "unsafe use of perf", 39 [LOCKDOWN_TRACEFS] = "use of tracefs", 40 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 41 }; 42 43 static enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 44 LOCKDOWN_INTEGRITY_MAX, 45 LOCKDOWN_CONFIDENTIALITY_MAX}; 46 47 /* 48 * Put the kernel into lock-down mode. 49 */ 50 static int lock_kernel_down(const char *where, enum lockdown_reason level) 51 { 52 if (kernel_locked_down >= level) 53 return -EPERM; 54 55 kernel_locked_down = level; 56 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 57 where); 58 return 0; 59 } 60 61 static int __init lockdown_param(char *level) 62 { 63 if (!level) 64 return -EINVAL; 65 66 if (strcmp(level, "integrity") == 0) 67 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 68 else if (strcmp(level, "confidentiality") == 0) 69 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 70 else 71 return -EINVAL; 72 73 return 0; 74 } 75 76 early_param("lockdown", lockdown_param); 77 78 /** 79 * lockdown_is_locked_down - Find out if the kernel is locked down 80 * @what: Tag to use in notice generated if lockdown is in effect 81 */ 82 static int lockdown_is_locked_down(enum lockdown_reason what) 83 { 84 if (kernel_locked_down >= what) { 85 if (lockdown_reasons[what]) 86 pr_notice("Lockdown: %s is restricted; see man kernel_lockdown.7\n", 87 lockdown_reasons[what]); 88 return -EPERM; 89 } 90 91 return 0; 92 } 93 94 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 95 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 96 }; 97 98 static int __init lockdown_lsm_init(void) 99 { 100 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 101 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 102 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 103 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 104 #endif 105 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 106 "lockdown"); 107 return 0; 108 } 109 110 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 111 loff_t *ppos) 112 { 113 char temp[80]; 114 int i, offset = 0; 115 116 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 117 enum lockdown_reason level = lockdown_levels[i]; 118 119 if (lockdown_reasons[level]) { 120 const char *label = lockdown_reasons[level]; 121 122 if (kernel_locked_down == level) 123 offset += sprintf(temp+offset, "[%s] ", label); 124 else 125 offset += sprintf(temp+offset, "%s ", label); 126 } 127 } 128 129 /* Convert the last space to a newline if needed. */ 130 if (offset > 0) 131 temp[offset-1] = '\n'; 132 133 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 134 } 135 136 static ssize_t lockdown_write(struct file *file, const char __user *buf, 137 size_t n, loff_t *ppos) 138 { 139 char *state; 140 int i, len, err = -EINVAL; 141 142 state = memdup_user_nul(buf, n); 143 if (IS_ERR(state)) 144 return PTR_ERR(state); 145 146 len = strlen(state); 147 if (len && state[len-1] == '\n') { 148 state[len-1] = '\0'; 149 len--; 150 } 151 152 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 153 enum lockdown_reason level = lockdown_levels[i]; 154 const char *label = lockdown_reasons[level]; 155 156 if (label && !strcmp(state, label)) 157 err = lock_kernel_down("securityfs", level); 158 } 159 160 kfree(state); 161 return err ? err : n; 162 } 163 164 static const struct file_operations lockdown_ops = { 165 .read = lockdown_read, 166 .write = lockdown_write, 167 }; 168 169 static int __init lockdown_secfs_init(void) 170 { 171 struct dentry *dentry; 172 173 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 174 &lockdown_ops); 175 return PTR_ERR_OR_ZERO(dentry); 176 } 177 178 core_initcall(lockdown_secfs_init); 179 180 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 181 DEFINE_EARLY_LSM(lockdown) = { 182 #else 183 DEFINE_LSM(lockdown) = { 184 #endif 185 .name = "lockdown", 186 .init = lockdown_lsm_init, 187 }; 188