LXR linux/security/root

   1/*
   2 * Root Plug sample LSM module
   3 *
   4 * Originally written for a Linux Journal.
   5 *
   6 * Copyright (C) 2002 Greg Kroah-Hartman <greg@kroah.com>
   7 *
   8 * Prevents any programs running with egid == 0 if a specific USB device
   9 * is not present in the system.  Yes, it can be gotten around, but is a
  10 * nice starting point for people to play with, and learn the LSM
  11 * interface.
  12 *
  13 * If you want to turn this into something with a semblance of security,
  14 * you need to hook the task_* functions also.
  15 *
  16 * See http://www.linuxjournal.com/article.php?sid=6279 for more information
  17 * about this code.
  18 *
  19 *      This program is free software; you can redistribute it and/or
  20 *      modify it under the terms of the GNU General Public License as
  21 *      published by the Free Software Foundation, version 2 of the
  22 *      License.
  23 */
  24
  25#include <linux/kernel.h>
  26#include <linux/init.h>
  27#include <linux/security.h>
  28#include <linux/usb.h>
  29#include <linux/moduleparam.h>
  30
  31/* default is a generic type of usb to serial converter */
  32static int vendor_id = 0x0557;
  33static int product_id = 0x2008;
  34
  35module_param(vendor_id, uint, 0400);
  36module_param(product_id, uint, 0400);
  37
  38/* should we print out debug messages */
  39static int debug = 0;
  40
  41module_param(debug, bool, 0600);
  42
  43#define MY_NAME "root_plug"
  44
  45#define root_dbg(fmt, arg...)                                   \
  46        do {                                                    \
  47                if (debug)                                      \
  48                        printk(KERN_DEBUG "%s: %s: " fmt ,      \
  49                                MY_NAME , __func__ ,    \
  50                                ## arg);                        \
  51        } while (0)
  52
  53static int rootplug_bprm_check_security (struct linux_binprm *bprm)
  54{
  55        struct usb_device *dev;
  56
  57        root_dbg("file %s, e_uid = %d, e_gid = %d\n",
  58                 bprm->filename, bprm->e_uid, bprm->e_gid);
  59
  60        if (bprm->e_gid == 0) {
  61                dev = usb_find_device(vendor_id, product_id);
  62                if (!dev) {
  63                        root_dbg("e_gid = 0, and device not found, "
  64                                 "task not allowed to run...\n");
  65                        return -EPERM;
  66                }
  67                usb_put_dev(dev);
  68        }
  69
  70        return 0;
  71}
  72
  73static struct security_operations rootplug_security_ops = {
  74        /* Use the capability functions for some of the hooks */
  75        .ptrace_may_access =            cap_ptrace_may_access,
  76        .ptrace_traceme =               cap_ptrace_traceme,
  77        .capget =                       cap_capget,
  78        .capset_check =                 cap_capset_check,
  79        .capset_set =                   cap_capset_set,
  80        .capable =                      cap_capable,
  81
  82        .bprm_apply_creds =             cap_bprm_apply_creds,
  83        .bprm_set_security =            cap_bprm_set_security,
  84
  85        .task_post_setuid =             cap_task_post_setuid,
  86        .task_reparent_to_init =        cap_task_reparent_to_init,
  87        .task_prctl =                   cap_task_prctl,
  88
  89        .bprm_check_security =          rootplug_bprm_check_security,
  90};
  91
  92static int __init rootplug_init (void)
  93{
  94        /* register ourselves with the security framework */
  95        if (register_security (&rootplug_security_ops)) {
  96                printk (KERN_INFO 
  97                        "Failure registering Root Plug module with the kernel\n");
  98                        return -EINVAL;
  99        }
 100        printk (KERN_INFO "Root Plug module initialized, "
 101                "vendor_id = %4.4x, product id = %4.4x\n", vendor_id, product_id);
 102        return 0;
 103}
 104
 105security_initcall (rootplug_init);
 106