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/*
* Root Plug sample LSM module
*
* Originally written for a Linux Journal.
*
* Copyright (C) 2002 Greg Kroah-Hartman <greg@kroah.com>
*
* Prevents any programs running with egid == 0 if a specific USB device
* is not present in the system. Yes, it can be gotten around, but is a
* nice starting point for people to play with, and learn the LSM
* interface.
*
* If you want to turn this into something with a semblance of security,
* you need to hook the task_* functions also.
*
* See http://www.linuxjournal.com/article.php?sid=6279 for more information
* about this code.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/usb.h>
/* flag to keep track of how we were registered */
static int secondary;
/* default is a generic type of usb to serial converter */
static int vendor_id = 0x0557;
static int product_id = 0x2008;
module_param(vendor_id, uint, 0400);
MODULE_PARM_DESC(vendor_id, "USB Vendor ID of device to look for");
module_param(product_id, uint, 0400);
MODULE_PARM_DESC(product_id, "USB Product ID of device to look for");
/* should we print out debug messages */
static int debug = 0;
module_param(debug, bool, 0600);
MODULE_PARM_DESC(debug, "Debug enabled or not");
#if defined(CONFIG_SECURITY_ROOTPLUG_MODULE)
#define MY_NAME THIS_MODULE->name
#else
#define MY_NAME "root_plug"
#endif
#define root_dbg(fmt, arg...) \
do { \
if (debug) \
printk(KERN_DEBUG "%s: %s: " fmt , \
MY_NAME , __FUNCTION__ , \
## arg); \
} while (0)
static int rootplug_bprm_check_security (struct linux_binprm *bprm)
{
struct usb_device *dev;
root_dbg("file %s, e_uid = %d, e_gid = %d\n",
bprm->filename, bprm->e_uid, bprm->e_gid);
if (bprm->e_gid == 0) {
dev = usb_find_device(vendor_id, product_id);
if (!dev) {
root_dbg("e_gid = 0, and device not found, "
"task not allowed to run...\n");
return -EPERM;
}
usb_put_dev(dev);
}
return 0;
}
static struct security_operations rootplug_security_ops = {
/* Use the capability functions for some of the hooks */
.ptrace = cap_ptrace,
.capget = cap_capget,
.capset_check = cap_capset_check,
.capset_set = cap_capset_set,
.capable = cap_capable,
.bprm_apply_creds = cap_bprm_apply_creds,
.bprm_set_security = cap_bprm_set_security,
.task_post_setuid = cap_task_post_setuid,
.task_reparent_to_init = cap_task_reparent_to_init,
.bprm_check_security = rootplug_bprm_check_security,
};
static int __init rootplug_init (void)
{
/* register ourselves with the security framework */
if (register_security (&rootplug_security_ops)) {
printk (KERN_INFO
"Failure registering Root Plug module with the kernel\n");
/* try registering with primary module */
if (mod_reg_security (MY_NAME, &rootplug_security_ops)) {
printk (KERN_INFO "Failure registering Root Plug "
" module with primary security module.\n");
return -EINVAL;
}
secondary = 1;
}
printk (KERN_INFO "Root Plug module initialized, "
"vendor_id = %4.4x, product id = %4.4x\n", vendor_id, product_id);
return 0;
}
static void __exit rootplug_exit (void)
{
/* remove ourselves from the security framework */
if (secondary) {
if (mod_unreg_security (MY_NAME, &rootplug_security_ops))
printk (KERN_INFO "Failure unregistering Root Plug "
" module with primary module.\n");
} else {
if (unregister_security (&rootplug_security_ops)) {
printk (KERN_INFO "Failure unregistering Root Plug "
"module with the kernel\n");
}
}
printk (KERN_INFO "Root Plug module removed\n");
}
security_initcall (rootplug_init);
module_exit (rootplug_exit);
MODULE_DESCRIPTION("Root Plug sample LSM module, written for Linux Journal article");
MODULE_LICENSE("GPL");
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