[NETFILTER]: nfctnetlink: Don't allow to change helper
[linux-2.6] / net / netfilter / nf_conntrack_sane.c
1 /* SANE connection tracking helper
2  * (SANE = Scanner Access Now Easy)
3  * For documentation about the SANE network protocol see
4  * http://www.sane-project.org/html/doc015.html
5  */
6
7 /* Copyright (C) 2007 Red Hat, Inc.
8  * Author: Michal Schmidt <mschmidt@redhat.com>
9  * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c):
10  *  (C) 1999-2001 Paul `Rusty' Russell
11  *  (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
12  *  (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
13  *  (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
14  *
15  * This program is free software; you can redistribute it and/or modify
16  * it under the terms of the GNU General Public License version 2 as
17  * published by the Free Software Foundation.
18  */
19
20 #include <linux/module.h>
21 #include <linux/moduleparam.h>
22 #include <linux/netfilter.h>
23 #include <linux/in.h>
24 #include <linux/tcp.h>
25 #include <net/netfilter/nf_conntrack.h>
26 #include <net/netfilter/nf_conntrack_helper.h>
27 #include <net/netfilter/nf_conntrack_expect.h>
28 #include <linux/netfilter/nf_conntrack_sane.h>
29
30 MODULE_LICENSE("GPL");
31 MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>");
32 MODULE_DESCRIPTION("SANE connection tracking helper");
33
34 static char *sane_buffer;
35
36 static DEFINE_SPINLOCK(nf_sane_lock);
37
38 #define MAX_PORTS 8
39 static u_int16_t ports[MAX_PORTS];
40 static unsigned int ports_c;
41 module_param_array(ports, ushort, &ports_c, 0400);
42
43 #if 0
44 #define DEBUGP printk
45 #else
46 #define DEBUGP(format, args...)
47 #endif
48
49 struct sane_request {
50         __be32 RPC_code;
51 #define SANE_NET_START      7   /* RPC code */
52
53         __be32 handle;
54 };
55
56 struct sane_reply_net_start {
57         __be32 status;
58 #define SANE_STATUS_SUCCESS 0
59
60         __be16 zero;
61         __be16 port;
62         /* other fields aren't interesting for conntrack */
63 };
64
65 static int help(struct sk_buff **pskb,
66                 unsigned int protoff,
67                 struct nf_conn *ct,
68                 enum ip_conntrack_info ctinfo)
69 {
70         unsigned int dataoff, datalen;
71         struct tcphdr _tcph, *th;
72         char *sb_ptr;
73         int ret = NF_ACCEPT;
74         int dir = CTINFO2DIR(ctinfo);
75         struct nf_ct_sane_master *ct_sane_info;
76         struct nf_conntrack_expect *exp;
77         struct nf_conntrack_tuple *tuple;
78         struct sane_request *req;
79         struct sane_reply_net_start *reply;
80         int family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
81
82         ct_sane_info = &nfct_help(ct)->help.ct_sane_info;
83         /* Until there's been traffic both ways, don't look in packets. */
84         if (ctinfo != IP_CT_ESTABLISHED &&
85             ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY)
86                 return NF_ACCEPT;
87
88         /* Not a full tcp header? */
89         th = skb_header_pointer(*pskb, protoff, sizeof(_tcph), &_tcph);
90         if (th == NULL)
91                 return NF_ACCEPT;
92
93         /* No data? */
94         dataoff = protoff + th->doff * 4;
95         if (dataoff >= (*pskb)->len)
96                 return NF_ACCEPT;
97
98         datalen = (*pskb)->len - dataoff;
99
100         spin_lock_bh(&nf_sane_lock);
101         sb_ptr = skb_header_pointer(*pskb, dataoff, datalen, sane_buffer);
102         BUG_ON(sb_ptr == NULL);
103
104         if (dir == IP_CT_DIR_ORIGINAL) {
105                 if (datalen != sizeof(struct sane_request))
106                         goto out;
107
108                 req = (struct sane_request *)sb_ptr;
109                 if (req->RPC_code != htonl(SANE_NET_START)) {
110                         /* Not an interesting command */
111                         ct_sane_info->state = SANE_STATE_NORMAL;
112                         goto out;
113                 }
114
115                 /* We're interested in the next reply */
116                 ct_sane_info->state = SANE_STATE_START_REQUESTED;
117                 goto out;
118         }
119
120         /* Is it a reply to an uninteresting command? */
121         if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
122                 goto out;
123
124         /* It's a reply to SANE_NET_START. */
125         ct_sane_info->state = SANE_STATE_NORMAL;
126
127         if (datalen < sizeof(struct sane_reply_net_start)) {
128                 DEBUGP("nf_ct_sane: NET_START reply too short\n");
129                 goto out;
130         }
131
132         reply = (struct sane_reply_net_start *)sb_ptr;
133         if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
134                 /* saned refused the command */
135                 DEBUGP("nf_ct_sane: unsuccessful SANE_STATUS = %u\n",
136                         ntohl(reply->status));
137                 goto out;
138         }
139
140         /* Invalid saned reply? Ignore it. */
141         if (reply->zero != 0)
142                 goto out;
143
144         exp = nf_conntrack_expect_alloc(ct);
145         if (exp == NULL) {
146                 ret = NF_DROP;
147                 goto out;
148         }
149
150         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
151         nf_conntrack_expect_init(exp, family,
152                                  &tuple->src.u3, &tuple->dst.u3,
153                                  IPPROTO_TCP,
154                                  NULL, &reply->port);
155
156         DEBUGP("nf_ct_sane: expect: ");
157         NF_CT_DUMP_TUPLE(&exp->tuple);
158         NF_CT_DUMP_TUPLE(&exp->mask);
159
160         /* Can't expect this?  Best to drop packet now. */
161         if (nf_conntrack_expect_related(exp) != 0)
162                 ret = NF_DROP;
163
164         nf_conntrack_expect_put(exp);
165
166 out:
167         spin_unlock_bh(&nf_sane_lock);
168         return ret;
169 }
170
171 static struct nf_conntrack_helper sane[MAX_PORTS][2];
172 static char sane_names[MAX_PORTS][2][sizeof("sane-65535")];
173
174 /* don't make this __exit, since it's called from __init ! */
175 static void nf_conntrack_sane_fini(void)
176 {
177         int i, j;
178
179         for (i = 0; i < ports_c; i++) {
180                 for (j = 0; j < 2; j++) {
181                         DEBUGP("nf_ct_sane: unregistering helper for pf: %d "
182                                "port: %d\n",
183                                 sane[i][j].tuple.src.l3num, ports[i]);
184                         nf_conntrack_helper_unregister(&sane[i][j]);
185                 }
186         }
187
188         kfree(sane_buffer);
189 }
190
191 static int __init nf_conntrack_sane_init(void)
192 {
193         int i, j = -1, ret = 0;
194         char *tmpname;
195
196         sane_buffer = kmalloc(65536, GFP_KERNEL);
197         if (!sane_buffer)
198                 return -ENOMEM;
199
200         if (ports_c == 0)
201                 ports[ports_c++] = SANE_PORT;
202
203         /* FIXME should be configurable whether IPv4 and IPv6 connections
204                  are tracked or not - YK */
205         for (i = 0; i < ports_c; i++) {
206                 sane[i][0].tuple.src.l3num = PF_INET;
207                 sane[i][1].tuple.src.l3num = PF_INET6;
208                 for (j = 0; j < 2; j++) {
209                         sane[i][j].tuple.src.u.tcp.port = htons(ports[i]);
210                         sane[i][j].tuple.dst.protonum = IPPROTO_TCP;
211                         sane[i][j].mask.src.u.tcp.port = 0xFFFF;
212                         sane[i][j].mask.dst.protonum = 0xFF;
213                         sane[i][j].max_expected = 1;
214                         sane[i][j].timeout = 5 * 60;    /* 5 Minutes */
215                         sane[i][j].me = THIS_MODULE;
216                         sane[i][j].help = help;
217                         tmpname = &sane_names[i][j][0];
218                         if (ports[i] == SANE_PORT)
219                                 sprintf(tmpname, "sane");
220                         else
221                                 sprintf(tmpname, "sane-%d", ports[i]);
222                         sane[i][j].name = tmpname;
223
224                         DEBUGP("nf_ct_sane: registering helper for pf: %d "
225                                "port: %d\n",
226                                 sane[i][j].tuple.src.l3num, ports[i]);
227                         ret = nf_conntrack_helper_register(&sane[i][j]);
228                         if (ret) {
229                                 printk(KERN_ERR "nf_ct_sane: failed to "
230                                        "register helper for pf: %d port: %d\n",
231                                         sane[i][j].tuple.src.l3num, ports[i]);
232                                 nf_conntrack_sane_fini();
233                                 return ret;
234                         }
235                 }
236         }
237
238         return 0;
239 }
240
241 module_init(nf_conntrack_sane_init);
242 module_exit(nf_conntrack_sane_fini);