/* * 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/config.h> #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");