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_XMON_WR] = "xmon write access", 36 [LOCKDOWN_INTEGRITY_MAX] = "integrity", 37 [LOCKDOWN_KCORE] = "/proc/kcore access", 38 [LOCKDOWN_KPROBES] = "use of kprobes", 39 [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", 40 [LOCKDOWN_PERF] = "unsafe use of perf", 41 [LOCKDOWN_TRACEFS] = "use of tracefs", 42 [LOCKDOWN_XMON_RW] = "xmon read and write access", 43 [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", 44 }; 45 46 static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, 47 LOCKDOWN_INTEGRITY_MAX, 48 LOCKDOWN_CONFIDENTIALITY_MAX}; 49 50 /* 51 * Put the kernel into lock-down mode. 52 */ 53 static int lock_kernel_down(const char *where, enum lockdown_reason level) 54 { 55 if (kernel_locked_down >= level) 56 return -EPERM; 57 58 kernel_locked_down = level; 59 pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", 60 where); 61 return 0; 62 } 63 64 static int __init lockdown_param(char *level) 65 { 66 if (!level) 67 return -EINVAL; 68 69 if (strcmp(level, "integrity") == 0) 70 lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); 71 else if (strcmp(level, "confidentiality") == 0) 72 lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); 73 else 74 return -EINVAL; 75 76 return 0; 77 } 78 79 early_param("lockdown", lockdown_param); 80 81 /** 82 * lockdown_is_locked_down - Find out if the kernel is locked down 83 * @what: Tag to use in notice generated if lockdown is in effect 84 */ 85 static int lockdown_is_locked_down(enum lockdown_reason what) 86 { 87 if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, 88 "Invalid lockdown reason")) 89 return -EPERM; 90 91 if (kernel_locked_down >= what) { 92 if (lockdown_reasons[what]) 93 pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", 94 current->comm, lockdown_reasons[what]); 95 return -EPERM; 96 } 97 98 return 0; 99 } 100 101 static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { 102 LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), 103 }; 104 105 static int __init lockdown_lsm_init(void) 106 { 107 #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) 108 lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); 109 #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) 110 lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); 111 #endif 112 security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), 113 "lockdown"); 114 return 0; 115 } 116 117 static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, 118 loff_t *ppos) 119 { 120 char temp[80]; 121 int i, offset = 0; 122 123 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 124 enum lockdown_reason level = lockdown_levels[i]; 125 126 if (lockdown_reasons[level]) { 127 const char *label = lockdown_reasons[level]; 128 129 if (kernel_locked_down == level) 130 offset += sprintf(temp+offset, "[%s] ", label); 131 else 132 offset += sprintf(temp+offset, "%s ", label); 133 } 134 } 135 136 /* Convert the last space to a newline if needed. */ 137 if (offset > 0) 138 temp[offset-1] = '\n'; 139 140 return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); 141 } 142 143 static ssize_t lockdown_write(struct file *file, const char __user *buf, 144 size_t n, loff_t *ppos) 145 { 146 char *state; 147 int i, len, err = -EINVAL; 148 149 state = memdup_user_nul(buf, n); 150 if (IS_ERR(state)) 151 return PTR_ERR(state); 152 153 len = strlen(state); 154 if (len && state[len-1] == '\n') { 155 state[len-1] = '\0'; 156 len--; 157 } 158 159 for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { 160 enum lockdown_reason level = lockdown_levels[i]; 161 const char *label = lockdown_reasons[level]; 162 163 if (label && !strcmp(state, label)) 164 err = lock_kernel_down("securityfs", level); 165 } 166 167 kfree(state); 168 return err ? err : n; 169 } 170 171 static const struct file_operations lockdown_ops = { 172 .read = lockdown_read, 173 .write = lockdown_write, 174 }; 175 176 static int __init lockdown_secfs_init(void) 177 { 178 struct dentry *dentry; 179 180 dentry = securityfs_create_file("lockdown", 0600, NULL, NULL, 181 &lockdown_ops); 182 return PTR_ERR_OR_ZERO(dentry); 183 } 184 185 core_initcall(lockdown_secfs_init); 186 187 #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY 188 DEFINE_EARLY_LSM(lockdown) = { 189 #else 190 DEFINE_LSM(lockdown) = { 191 #endif 192 .name = "lockdown", 193 .init = lockdown_lsm_init, 194 }; 195