file caps: always start with clear bprm->caps_*
[linux-2.6.git] / security / root_plug.c
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 */
32 static int vendor_id = 0x0557;
33 static int product_id = 0x2008;
34
35 module_param(vendor_id, uint, 0400);
36 module_param(product_id, uint, 0400);
37
38 /* should we print out debug messages */
39 static int debug = 0;
40
41 module_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
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",
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
73 static 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
92 static 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
105 security_initcall (rootplug_init);