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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 | // SPDX-License-Identifier: GPL-2.0 /* Lock down the kernel * * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ #include <linux/security.h> #include <linux/export.h> #include <linux/lsm_hooks.h> static enum lockdown_reason kernel_locked_down; static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX}; /* * Put the kernel into lock-down mode. */ static int lock_kernel_down(const char *where, enum lockdown_reason level) { if (kernel_locked_down >= level) return -EPERM; kernel_locked_down = level; pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", where); return 0; } static int __init lockdown_param(char *level) { if (!level) return -EINVAL; if (strcmp(level, "integrity") == 0) lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX); else if (strcmp(level, "confidentiality") == 0) lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX); else return -EINVAL; return 0; } early_param("lockdown", lockdown_param); /** * lockdown_is_locked_down - Find out if the kernel is locked down * @what: Tag to use in notice generated if lockdown is in effect */ static int lockdown_is_locked_down(enum lockdown_reason what) { if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX, "Invalid lockdown reason")) return -EPERM; if (kernel_locked_down >= what) { if (lockdown_reasons[what]) pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", current->comm, lockdown_reasons[what]); return -EPERM; } return 0; } static struct security_hook_list lockdown_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(locked_down, lockdown_is_locked_down), }; static int __init lockdown_lsm_init(void) { #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY) lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX); #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY) lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX); #endif security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks), "lockdown"); return 0; } static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) { char temp[80]; int i, offset = 0; for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { enum lockdown_reason level = lockdown_levels[i]; if (lockdown_reasons[level]) { const char *label = lockdown_reasons[level]; if (kernel_locked_down == level) offset += sprintf(temp+offset, "[%s] ", label); else offset += sprintf(temp+offset, "%s ", label); } } /* Convert the last space to a newline if needed. */ if (offset > 0) temp[offset-1] = '\n'; return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); } static ssize_t lockdown_write(struct file *file, const char __user *buf, size_t n, loff_t *ppos) { char *state; int i, len, err = -EINVAL; state = memdup_user_nul(buf, n); if (IS_ERR(state)) return PTR_ERR(state); len = strlen(state); if (len && state[len-1] == '\n') { state[len-1] = '\0'; len--; } for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) { enum lockdown_reason level = lockdown_levels[i]; const char *label = lockdown_reasons[level]; if (label && !strcmp(state, label)) err = lock_kernel_down("securityfs", level); } kfree(state); return err ? err : n; } static const struct file_operations lockdown_ops = { .read = lockdown_read, .write = lockdown_write, }; static int __init lockdown_secfs_init(void) { struct dentry *dentry; dentry = securityfs_create_file("lockdown", 0644, NULL, NULL, &lockdown_ops); return PTR_ERR_OR_ZERO(dentry); } core_initcall(lockdown_secfs_init); #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY DEFINE_EARLY_LSM(lockdown) = { #else DEFINE_LSM(lockdown) = { #endif .name = "lockdown", .init = lockdown_lsm_init, }; |