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_XMON_WR] = "xmon write 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_XMON_RW] = "xmon read and write access", 42 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 43 }; 44 45 static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 46 LOCKDOWN_INTEGRITY_MAX, 47 LOCKDOWN_CONFIDENTIALITY_MAX}; 48 49 /* 50 * Put the kernel into lock-down mode. 51 */ 52 static int lock_kernel_down(const char *where, enum lockdown_reason level) 53 { 54 if (kernel_locked_down >= level) 55 return -EPERM; 56 57 kernel_locked_down = level; 58 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 59 where); 60 return 0; 61 } 62 63 static int __init lockdown_param(char *level) 64 { 65 if (!level) 66 return -EINVAL; 67 68 if (strcmp(level, "integrity") == 0) 69 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 70 else if (strcmp(level, "confidentiality") == 0) 71 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 72 else 73 return -EINVAL; 74 75 return 0; 76 } 77 78 early_param("lockdown", lockdown_param); 79 80 /** 81 * lockdown_is_locked_down - Find out if the kernel is locked down 82 * @what: Tag to use in notice generated if lockdown is in effect 83 */ 84 static int lockdown_is_locked_down(enum lockdown_reason what) 85 { 86 if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, 87 "Invalid lockdown reason")) 88 return -EPERM; 89 90 if (kernel_locked_down >= what) { 91 if (lockdown_reasons[what]) 92 pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", 93 current->comm, lockdown_reasons[what]); 94 return -EPERM; 95 } 96 97 return 0; 98 } 99 100 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 101 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 102 }; 103 104 static int __init lockdown_lsm_init(void) 105 { 106 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 107 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 108 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 109 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 110 #endif 111 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 112 "lockdown"); 113 return 0; 114 } 115 116 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 117 loff_t *ppos) 118 { 119 char temp[80]; 120 int i, offset = 0; 121 122 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 123 enum lockdown_reason level = lockdown_levels[i]; 124 125 if (lockdown_reasons[level]) { 126 const char *label = lockdown_reasons[level]; 127 128 if (kernel_locked_down == level) 129 offset += sprintf(temp+offset, "[%s] ", label); 130 else 131 offset += sprintf(temp+offset, "%s ", label); 132 } 133 } 134 135 /* Convert the last space to a newline if needed. */ 136 if (offset > 0) 137 temp[offset-1] = '\n'; 138 139 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 140 } 141 142 static ssize_t lockdown_write(struct file *file, const char __user *buf, 143 size_t n, loff_t *ppos) 144 { 145 char *state; 146 int i, len, err = -EINVAL; 147 148 state = memdup_user_nul(buf, n); 149 if (IS_ERR(state)) 150 return PTR_ERR(state); 151 152 len = strlen(state); 153 if (len && state[len-1] == '\n') { 154 state[len-1] = '\0'; 155 len--; 156 } 157 158 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 159 enum lockdown_reason level = lockdown_levels[i]; 160 const char *label = lockdown_reasons[level]; 161 162 if (label && !strcmp(state, label)) 163 err = lock_kernel_down("securityfs", level); 164 } 165 166 kfree(state); 167 return err ? err : n; 168 } 169 170 static const struct file_operations lockdown_ops = { 171 .read = lockdown_read, 172 .write = lockdown_write, 173 }; 174 175 static int __init lockdown_secfs_init(void) 176 { 177 struct dentry *dentry; 178 179 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 180 &lockdown_ops); 181 return PTR_ERR_OR_ZERO(dentry); 182 } 183 184 core_initcall(lockdown_secfs_init); 185 186 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 187 DEFINE_EARLY_LSM(lockdown) = { 188 #else 189 DEFINE_LSM(lockdown) = { 190 #endif 191 .name = "lockdown", 192 .init = lockdown_lsm_init, 193 }; 194