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_EFI_TEST] = "/dev/efi_test access", 24 [LOCKDOWN_KEXEC] = "kexec of unsigned images", 25 [LOCKDOWN_HIBERNATION] = "hibernation", 26 [LOCKDOWN_PCI_ACCESS] = "direct PCI access", 27 [LOCKDOWN_IOPORT] = "raw io port access", 28 [LOCKDOWN_MSR] = "raw MSR access", 29 [LOCKDOWN_ACPI_TABLES] = "modifying ACPI tables", 30 [LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage", 31 [LOCKDOWN_TIOCSSERIAL] = "reconfiguration of serial port IO", 32 [LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters", 33 [LOCKDOWN_MMIOTRACE] = "unsafe mmio", 34 [LOCKDOWN_DEBUGFS] = "debugfs access", 35 [LOCKDOWN_INTEGRITY_MAX] = "integrity", 36 [LOCKDOWN_KCORE] = "/proc/kcore access", 37 [LOCKDOWN_KPROBES] = "use of kprobes", 38 [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", 39 [LOCKDOWN_PERF] = "unsafe use of perf", 40 [LOCKDOWN_TRACEFS] = "use of tracefs", 41 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 42 }; 43 44 static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 45 LOCKDOWN_INTEGRITY_MAX, 46 LOCKDOWN_CONFIDENTIALITY_MAX}; 47 48 /* 49 * Put the kernel into lock-down mode. 50 */ 51 static int lock_kernel_down(const char *where, enum lockdown_reason level) 52 { 53 if (kernel_locked_down >= level) 54 return -EPERM; 55 56 kernel_locked_down = level; 57 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 58 where); 59 return 0; 60 } 61 62 static int __init lockdown_param(char *level) 63 { 64 if (!level) 65 return -EINVAL; 66 67 if (strcmp(level, "integrity") == 0) 68 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 69 else if (strcmp(level, "confidentiality") == 0) 70 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 71 else 72 return -EINVAL; 73 74 return 0; 75 } 76 77 early_param("lockdown", lockdown_param); 78 79 /** 80 * lockdown_is_locked_down - Find out if the kernel is locked down 81 * @what: Tag to use in notice generated if lockdown is in effect 82 */ 83 static int lockdown_is_locked_down(enum lockdown_reason what) 84 { 85 if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, 86 "Invalid lockdown reason")) 87 return -EPERM; 88 89 if (kernel_locked_down >= what) { 90 if (lockdown_reasons[what]) 91 pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", 92 current->comm, lockdown_reasons[what]); 93 return -EPERM; 94 } 95 96 return 0; 97 } 98 99 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 100 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 101 }; 102 103 static int __init lockdown_lsm_init(void) 104 { 105 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 106 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 107 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 108 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 109 #endif 110 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 111 "lockdown"); 112 return 0; 113 } 114 115 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 116 loff_t *ppos) 117 { 118 char temp[80]; 119 int i, offset = 0; 120 121 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 122 enum lockdown_reason level = lockdown_levels[i]; 123 124 if (lockdown_reasons[level]) { 125 const char *label = lockdown_reasons[level]; 126 127 if (kernel_locked_down == level) 128 offset += sprintf(temp+offset, "[%s] ", label); 129 else 130 offset += sprintf(temp+offset, "%s ", label); 131 } 132 } 133 134 /* Convert the last space to a newline if needed. */ 135 if (offset > 0) 136 temp[offset-1] = '\n'; 137 138 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 139 } 140 141 static ssize_t lockdown_write(struct file *file, const char __user *buf, 142 size_t n, loff_t *ppos) 143 { 144 char *state; 145 int i, len, err = -EINVAL; 146 147 state = memdup_user_nul(buf, n); 148 if (IS_ERR(state)) 149 return PTR_ERR(state); 150 151 len = strlen(state); 152 if (len && state[len-1] == '\n') { 153 state[len-1] = '\0'; 154 len--; 155 } 156 157 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 158 enum lockdown_reason level = lockdown_levels[i]; 159 const char *label = lockdown_reasons[level]; 160 161 if (label && !strcmp(state, label)) 162 err = lock_kernel_down("securityfs", level); 163 } 164 165 kfree(state); 166 return err ? err : n; 167 } 168 169 static const struct file_operations lockdown_ops = { 170 .read = lockdown_read, 171 .write = lockdown_write, 172 }; 173 174 static int __init lockdown_secfs_init(void) 175 { 176 struct dentry *dentry; 177 178 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 179 &lockdown_ops); 180 return PTR_ERR_OR_ZERO(dentry); 181 } 182 183 core_initcall(lockdown_secfs_init); 184 185 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 186 DEFINE_EARLY_LSM(lockdown) = { 187 #else 188 DEFINE_LSM(lockdown) = { 189 #endif 190 .name = "lockdown", 191 .init = lockdown_lsm_init, 192 }; 193