[linux.git] / security / root_plug.c

/*
 * Root Plug sample LSM module
 *
 * Originally written for a Linux Journal.
 *
 * Copyright (C) 2002 Greg Kroah-Hartman <[email protected]>
 *
 * 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/kernel.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/usb.h>
#include <linux/moduleparam.h>

/* 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_param(product_id, uint, 0400);

/* should we print out debug messages */
static int debug = 0;

module_param(debug, bool, 0600);

#define MY_NAME "root_plug"

#define root_dbg(fmt, arg...)					\
	do {							\
		if (debug)					\
			printk(KERN_DEBUG "%s: %s: " fmt ,	\
				MY_NAME , __func__ , 	\
				## 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->cred->euid, bprm->cred->egid);

	if (bprm->cred->egid == 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 = {
	.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");
			return -EINVAL;
	}
	printk (KERN_INFO "Root Plug module initialized, "
		"vendor_id = %4.4x, product id = %4.4x\n", vendor_id, product_id);
	return 0;
}

security_initcall (rootplug_init);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Root Plug sample LSM module
	3	*
	4	* Originally written for a Linux Journal.
	5	*
	6	* Copyright (C) 2002 Greg Kroah-Hartman <[email protected]>
	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
1da177e4 LT	25	#include <linux/kernel.h>
	26	#include <linux/init.h>
	27	#include <linux/security.h>
	28	#include <linux/usb.h>
20510f2f	29	#include <linux/moduleparam.h>
1da177e4	30
1da177e4 LT	31	/* default is a generic type of usb to serial converter */
	32	static int vendor_id = 0x0557;
	33	static int product_id = 0x2008;
	34
	35	module_param(vendor_id, uint, 0400);
1da177e4	36	module_param(product_id, uint, 0400);
1da177e4 LT	37
	38	/* should we print out debug messages */
	39	static int debug = 0;
	40
	41	module_param(debug, bool, 0600);
1da177e4	42
1da177e4	43	#define MY_NAME "root_plug"
1da177e4 LT	44
	45	#define root_dbg(fmt, arg...) \
	46	do { \
	47	if (debug) \
	48	printk(KERN_DEBUG "%s: %s: " fmt , \
dd6f953a	49	MY_NAME , __func__ , \
1da177e4 LT	50	## arg); \
	51	} while (0)
	52
	53	static 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",
a6f76f23	58	bprm->filename, bprm->cred->euid, bprm->cred->egid);
1da177e4	59
a6f76f23	60	if (bprm->cred->egid == 0) {
1da177e4 LT	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
	73	static struct security_operations rootplug_security_ops = {
1da177e4 LT	74	.bprm_check_security = rootplug_bprm_check_security,
	75	};
	76
	77	static int __init rootplug_init (void)
	78	{
	79	/* register ourselves with the security framework */
	80	if (register_security (&rootplug_security_ops)) {
	81	printk (KERN_INFO
	82	"Failure registering Root Plug module with the kernel\n");
1da177e4	83	return -EINVAL;
1da177e4 LT	84	}
	85	printk (KERN_INFO "Root Plug module initialized, "
	86	"vendor_id = %4.4x, product id = %4.4x\n", vendor_id, product_id);
	87	return 0;
	88	}
	89
1da177e4	90	security_initcall (rootplug_init);