xt_SECMARK.c revision f51f5ec6909fad9ddfcaa962377f7892d7918302 
1/*
2 * Module for modifying the secmark field of the skb, for use by
3 * security subsystems.
4 *
5 * Based on the nfmark match by:
6 * (C) 1999-2001 Marc Boucher <marc@mbsi.ca>
7 *
8 * (C) 2006 Red Hat, Inc., James Morris <jmorris@redhat.com>
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
13 *
14 */
15#include <linux/module.h>
16#include <linux/skbuff.h>
17#include <linux/selinux.h>
18#include <linux/netfilter/x_tables.h>
19#include <linux/netfilter/xt_SECMARK.h>
20
21MODULE_LICENSE("GPL");
22MODULE_AUTHOR("James Morris <jmorris@redhat.com>");
23MODULE_DESCRIPTION("Xtables: packet security mark modification");
24MODULE_ALIAS("ipt_SECMARK");
25MODULE_ALIAS("ip6t_SECMARK");
26
27#define PFX "SECMARK: "
28
29static u8 mode;
30
31static unsigned int
32secmark_tg(struct sk_buff *skb, const struct net_device *in,
33           const struct net_device *out, unsigned int hooknum,
34           const struct xt_target *target, const void *targinfo)
35{
36	u32 secmark = 0;
37	const struct xt_secmark_target_info *info = targinfo;
38
39	BUG_ON(info->mode != mode);
40
41	switch (mode) {
42	case SECMARK_MODE_SEL:
43		secmark = info->u.sel.selsid;
44		break;
45
46	default:
47		BUG();
48	}
49
50	skb->secmark = secmark;
51	return XT_CONTINUE;
52}
53
54static bool checkentry_selinux(struct xt_secmark_target_info *info)
55{
56	int err;
57	struct xt_secmark_target_selinux_info *sel = &info->u.sel;
58
59	sel->selctx[SECMARK_SELCTX_MAX - 1] = '\0';
60
61	err = selinux_string_to_sid(sel->selctx, &sel->selsid);
62	if (err) {
63		if (err == -EINVAL)
64			printk(KERN_INFO PFX "invalid SELinux context \'%s\'\n",
65			       sel->selctx);
66		return false;
67	}
68
69	if (!sel->selsid) {
70		printk(KERN_INFO PFX "unable to map SELinux context \'%s\'\n",
71		       sel->selctx);
72		return false;
73	}
74
75	err = selinux_secmark_relabel_packet_permission(sel->selsid);
76	if (err) {
77		printk(KERN_INFO PFX "unable to obtain relabeling permission\n");
78		return false;
79	}
80
81	selinux_secmark_refcount_inc();
82	return true;
83}
84
85static bool
86secmark_tg_check(const char *tablename, const void *entry,
87                 const struct xt_target *target, void *targinfo,
88                 unsigned int hook_mask)
89{
90	struct xt_secmark_target_info *info = targinfo;
91
92	if (mode && mode != info->mode) {
93		printk(KERN_INFO PFX "mode already set to %hu cannot mix with "
94		       "rules for mode %hu\n", mode, info->mode);
95		return false;
96	}
97
98	switch (info->mode) {
99	case SECMARK_MODE_SEL:
100		if (!checkentry_selinux(info))
101			return false;
102		break;
103
104	default:
105		printk(KERN_INFO PFX "invalid mode: %hu\n", info->mode);
106		return false;
107	}
108
109	if (!mode)
110		mode = info->mode;
111	return true;
112}
113
114static void secmark_tg_destroy(const struct xt_target *target, void *targinfo)
115{
116	switch (mode) {
117	case SECMARK_MODE_SEL:
118		selinux_secmark_refcount_dec();
119	}
120}
121
122static struct xt_target secmark_tg_reg[] __read_mostly = {
123	{
124		.name		= "SECMARK",
125		.family		= AF_INET,
126		.checkentry	= secmark_tg_check,
127		.destroy	= secmark_tg_destroy,
128		.target		= secmark_tg,
129		.targetsize	= sizeof(struct xt_secmark_target_info),
130		.table		= "mangle",
131		.me		= THIS_MODULE,
132	},
133	{
134		.name		= "SECMARK",
135		.family		= AF_INET6,
136		.checkentry	= secmark_tg_check,
137		.destroy	= secmark_tg_destroy,
138		.target		= secmark_tg,
139		.targetsize	= sizeof(struct xt_secmark_target_info),
140		.table		= "mangle",
141		.me		= THIS_MODULE,
142	},
143};
144
145static int __init secmark_tg_init(void)
146{
147	return xt_register_targets(secmark_tg_reg, ARRAY_SIZE(secmark_tg_reg));
148}
149
150static void __exit secmark_tg_exit(void)
151{
152	xt_unregister_targets(secmark_tg_reg, ARRAY_SIZE(secmark_tg_reg));
153}
154
155module_init(secmark_tg_init);
156module_exit(secmark_tg_exit);
157