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 const char *const 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 const 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 (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, 85 "Invalid lockdown reason")) 86 return -EPERM; 87 88 if (kernel_locked_down >= what) { 89 if (lockdown_reasons[what]) 90 pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", 91 current->comm, lockdown_reasons[what]); 92 return -EPERM; 93 } 94 95 return 0; 96 } 97 98 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 99 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 100 }; 101 102 static int __init lockdown_lsm_init(void) 103 { 104 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 105 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 106 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 107 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 108 #endif 109 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 110 "lockdown"); 111 return 0; 112 } 113 114 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 115 loff_t *ppos) 116 { 117 char temp[80]; 118 int i, offset = 0; 119 120 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 121 enum lockdown_reason level = lockdown_levels[i]; 122 123 if (lockdown_reasons[level]) { 124 const char *label = lockdown_reasons[level]; 125 126 if (kernel_locked_down == level) 127 offset += sprintf(temp+offset, "[%s] ", label); 128 else 129 offset += sprintf(temp+offset, "%s ", label); 130 } 131 } 132 133 /* Convert the last space to a newline if needed. */ 134 if (offset > 0) 135 temp[offset-1] = '\n'; 136 137 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 138 } 139 140 static ssize_t lockdown_write(struct file *file, const char __user *buf, 141 size_t n, loff_t *ppos) 142 { 143 char *state; 144 int i, len, err = -EINVAL; 145 146 state = memdup_user_nul(buf, n); 147 if (IS_ERR(state)) 148 return PTR_ERR(state); 149 150 len = strlen(state); 151 if (len && state[len-1] == '\n') { 152 state[len-1] = '\0'; 153 len--; 154 } 155 156 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 157 enum lockdown_reason level = lockdown_levels[i]; 158 const char *label = lockdown_reasons[level]; 159 160 if (label && !strcmp(state, label)) 161 err = lock_kernel_down("securityfs", level); 162 } 163 164 kfree(state); 165 return err ? err : n; 166 } 167 168 static const struct file_operations lockdown_ops = { 169 .read = lockdown_read, 170 .write = lockdown_write, 171 }; 172 173 static int __init lockdown_secfs_init(void) 174 { 175 struct dentry *dentry; 176 177 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 178 &lockdown_ops); 179 return PTR_ERR_OR_ZERO(dentry); 180 } 181 182 core_initcall(lockdown_secfs_init); 183 184 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 185 DEFINE_EARLY_LSM(lockdown) = { 186 #else 187 DEFINE_LSM(lockdown) = { 188 #endif 189 .name = "lockdown", 190 .init = lockdown_lsm_init, 191 }; 192