| 1 | |
| 2 | |
| 3 | *
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| 4 | * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
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| 5 | * Written by David Howells ([email protected])
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| 6 | *
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| 7 | * This program is free software; you can redistribute it and/or
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| 8 | * modify it under the terms of the GNU General Public Licence
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| 9 | * as published by the Free Software Foundation; either version
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| 10 | * 2 of the Licence, or (at your option) any later version.
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| 11 |
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| 12 |
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| 13 | #include <linux/security.h>
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| 14 | #include <linux/export.h>
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| 15 | #include <linux/lsm_hooks.h>
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| 16 | #include <uapi/linux/lsm.h>
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| 17 |
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| 18 | static enum lockdown_reason kernel_locked_down;
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| 19 |
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| 20 | static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE,
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| 21 | LOCKDOWN_INTEGRITY_MAX,
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| 22 | LOCKDOWN_CONFIDENTIALITY_MAX};
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| 23 |
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| 24 | |
| 25 | * Put the kernel into lock-down mode.
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| 26 |
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| 27 | static int lock_kernel_down(const char *where, enum lockdown_reason level)
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| 28 | {
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| 29 | if (kernel_locked_down >= level)
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| 30 | return -EPERM;
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| 31 |
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| 32 | kernel_locked_down = level;
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| 33 | pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n",
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| 34 | where);
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| 35 | return 0;
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| 36 | }
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| 37 |
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| 38 | static int __init lockdown_param(char *level)
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| 39 | {
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| 40 | if (!level)
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| 41 | return -EINVAL;
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| 42 |
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| 43 | if (strcmp(level, "integrity") == 0)
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| 44 | lock_kernel_down("command line", LOCKDOWN_INTEGRITY_MAX);
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| 45 | else if (strcmp(level, "confidentiality") == 0)
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| 46 | lock_kernel_down("command line", LOCKDOWN_CONFIDENTIALITY_MAX);
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| 47 | else
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| 48 | return -EINVAL;
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| 49 |
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| 50 | return 0;
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| 51 | }
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| 52 |
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| 53 | early_param("lockdown", lockdown_param);
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| 54 |
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| 55 | |
| 56 | * lockdown_is_locked_down - Find out if the kernel is locked down
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| 57 | * @what: Tag to use in notice generated if lockdown is in effect
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| 58 |
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| 59 | static int lockdown_is_locked_down(enum lockdown_reason what)
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| 60 | {
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| 61 | if (WARN(what >= LOCKDOWN_CONFIDENTIALITY_MAX,
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| 62 | "Invalid lockdown reason"))
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| 63 | return -EPERM;
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| 64 |
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| 65 | if (kernel_locked_down >= what) {
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| 66 | if (lockdown_reasons[what])
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| 67 | pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
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| 68 | current->comm, lockdown_reasons[what]);
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| 69 | return -EPERM;
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| 70 | }
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| 71 |
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| 72 | return 0;
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| 73 | }
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| 74 |
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| 75 | static struct security_hook_list lockdown_hooks[] __ro_after_init = {
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| 76 | LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
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| 77 | };
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| 78 |
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| 79 | static const struct lsm_id lockdown_lsmid = {
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| 80 | .name = "lockdown",
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| 81 | .id = LSM_ID_LOCKDOWN,
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| 82 | };
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| 83 |
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| 84 | static int __init lockdown_lsm_init(void)
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| 85 | {
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| 86 | #if defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_INTEGRITY)
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| 87 | lock_kernel_down("Kernel configuration", LOCKDOWN_INTEGRITY_MAX);
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| 88 | #elif defined(CONFIG_LOCK_DOWN_KERNEL_FORCE_CONFIDENTIALITY)
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| 89 | lock_kernel_down("Kernel configuration", LOCKDOWN_CONFIDENTIALITY_MAX);
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| 90 | #endif
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| 91 | security_add_hooks(lockdown_hooks, ARRAY_SIZE(lockdown_hooks),
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| 92 | &lockdown_lsmid);
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| 93 | return 0;
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| 94 | }
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| 95 |
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| 96 | static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count,
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| 97 | loff_t *ppos)
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| 98 | {
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| 99 | char temp[80] = "";
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| 100 | int i, offset = 0;
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| 101 |
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| 102 | for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
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| 103 | enum lockdown_reason level = lockdown_levels[i];
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| 104 |
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| 105 | if (lockdown_reasons[level]) {
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| 106 | const char *label = lockdown_reasons[level];
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| 107 |
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| 108 | if (kernel_locked_down == level)
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| 109 | offset += sprintf(temp+offset, "[%s] ", label);
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| 110 | else
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| 111 | offset += sprintf(temp+offset, "%s ", label);
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| 112 | }
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| 113 | }
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| 114 |
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| 115 |
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| 116 | if (offset > 0)
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| 117 | temp[offset-1] = '\n';
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| 118 |
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| 119 | return simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
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| 120 | }
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| 121 |
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| 122 | static ssize_t lockdown_write(struct file *file, const char __user *buf,
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| 123 | size_t n, loff_t *ppos)
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| 124 | {
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| 125 | char *state;
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| 126 | int i, len, err = -EINVAL;
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| 127 |
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| 128 | state = memdup_user_nul(buf, n);
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| 129 | if (IS_ERR(state))
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| 130 | return PTR_ERR(state);
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| 131 |
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| 132 | len = strlen(state);
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| 133 | if (len && state[len-1] == '\n') {
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| 134 | state[len-1] = '\0';
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| 135 | len--;
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| 136 | }
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| 137 |
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| 138 | for (i = 0; i < ARRAY_SIZE(lockdown_levels); i++) {
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| 139 | enum lockdown_reason level = lockdown_levels[i];
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| 140 | const char *label = lockdown_reasons[level];
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| 141 |
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| 142 | if (label && !strcmp(state, label))
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| 143 | err = lock_kernel_down("securityfs", level);
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| 144 | }
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| 145 |
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| 146 | kfree(state);
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| 147 | return err ? err : n;
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| 148 | }
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| 149 |
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| 150 | static const struct file_operations lockdown_ops = {
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| 151 | .read = lockdown_read,
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| 152 | .write = lockdown_write,
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| 153 | };
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| 154 |
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| 155 | static int __init lockdown_secfs_init(void)
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| 156 | {
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| 157 | struct dentry *dentry;
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| 158 |
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| 159 | dentry = securityfs_create_file("lockdown", 0644, NULL, NULL,
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| 160 | &lockdown_ops);
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| 161 | return PTR_ERR_OR_ZERO(dentry);
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| 162 | }
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| 163 |
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| 164 | #ifdef CONFIG_SECURITY_LOCKDOWN_LSM_EARLY
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| 165 | DEFINE_EARLY_LSM(lockdown) = {
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| 166 | #else
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| 167 | DEFINE_LSM(lockdown) = {
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| 168 | #endif
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| 169 | .id = &lockdown_lsmid,
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| 170 | .init = lockdown_lsm_init,
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| 171 | .initcall_core = lockdown_secfs_init,
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| 172 | };
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