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6fecd198 MS |
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> | |
5a0e3ad6 | 23 | #include <linux/slab.h> |
6fecd198 MS |
24 | #include <linux/in.h> |
25 | #include <linux/tcp.h> | |
26 | #include <net/netfilter/nf_conntrack.h> | |
27 | #include <net/netfilter/nf_conntrack_helper.h> | |
28 | #include <net/netfilter/nf_conntrack_expect.h> | |
29 | #include <linux/netfilter/nf_conntrack_sane.h> | |
30 | ||
31 | MODULE_LICENSE("GPL"); | |
32 | MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>"); | |
33 | MODULE_DESCRIPTION("SANE connection tracking helper"); | |
4dc06f96 | 34 | MODULE_ALIAS_NFCT_HELPER("sane"); |
6fecd198 MS |
35 | |
36 | static char *sane_buffer; | |
37 | ||
38 | static DEFINE_SPINLOCK(nf_sane_lock); | |
39 | ||
40 | #define MAX_PORTS 8 | |
41 | static u_int16_t ports[MAX_PORTS]; | |
42 | static unsigned int ports_c; | |
43 | module_param_array(ports, ushort, &ports_c, 0400); | |
44 | ||
6fecd198 MS |
45 | struct sane_request { |
46 | __be32 RPC_code; | |
47 | #define SANE_NET_START 7 /* RPC code */ | |
48 | ||
49 | __be32 handle; | |
50 | }; | |
51 | ||
52 | struct sane_reply_net_start { | |
53 | __be32 status; | |
54 | #define SANE_STATUS_SUCCESS 0 | |
55 | ||
56 | __be16 zero; | |
57 | __be16 port; | |
58 | /* other fields aren't interesting for conntrack */ | |
59 | }; | |
60 | ||
3db05fea | 61 | static int help(struct sk_buff *skb, |
6fecd198 MS |
62 | unsigned int protoff, |
63 | struct nf_conn *ct, | |
64 | enum ip_conntrack_info ctinfo) | |
65 | { | |
66 | unsigned int dataoff, datalen; | |
02e23f40 JE |
67 | const struct tcphdr *th; |
68 | struct tcphdr _tcph; | |
69 | void *sb_ptr; | |
6fecd198 MS |
70 | int ret = NF_ACCEPT; |
71 | int dir = CTINFO2DIR(ctinfo); | |
72 | struct nf_ct_sane_master *ct_sane_info; | |
73 | struct nf_conntrack_expect *exp; | |
74 | struct nf_conntrack_tuple *tuple; | |
75 | struct sane_request *req; | |
76 | struct sane_reply_net_start *reply; | |
6fecd198 MS |
77 | |
78 | ct_sane_info = &nfct_help(ct)->help.ct_sane_info; | |
79 | /* Until there's been traffic both ways, don't look in packets. */ | |
80 | if (ctinfo != IP_CT_ESTABLISHED && | |
81 | ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) | |
82 | return NF_ACCEPT; | |
83 | ||
84 | /* Not a full tcp header? */ | |
3db05fea | 85 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
6fecd198 MS |
86 | if (th == NULL) |
87 | return NF_ACCEPT; | |
88 | ||
89 | /* No data? */ | |
90 | dataoff = protoff + th->doff * 4; | |
3db05fea | 91 | if (dataoff >= skb->len) |
6fecd198 MS |
92 | return NF_ACCEPT; |
93 | ||
3db05fea | 94 | datalen = skb->len - dataoff; |
6fecd198 MS |
95 | |
96 | spin_lock_bh(&nf_sane_lock); | |
3db05fea | 97 | sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer); |
6fecd198 MS |
98 | BUG_ON(sb_ptr == NULL); |
99 | ||
100 | if (dir == IP_CT_DIR_ORIGINAL) { | |
101 | if (datalen != sizeof(struct sane_request)) | |
102 | goto out; | |
103 | ||
02e23f40 | 104 | req = sb_ptr; |
6fecd198 MS |
105 | if (req->RPC_code != htonl(SANE_NET_START)) { |
106 | /* Not an interesting command */ | |
107 | ct_sane_info->state = SANE_STATE_NORMAL; | |
108 | goto out; | |
109 | } | |
110 | ||
111 | /* We're interested in the next reply */ | |
112 | ct_sane_info->state = SANE_STATE_START_REQUESTED; | |
113 | goto out; | |
114 | } | |
115 | ||
116 | /* Is it a reply to an uninteresting command? */ | |
117 | if (ct_sane_info->state != SANE_STATE_START_REQUESTED) | |
118 | goto out; | |
119 | ||
120 | /* It's a reply to SANE_NET_START. */ | |
121 | ct_sane_info->state = SANE_STATE_NORMAL; | |
122 | ||
123 | if (datalen < sizeof(struct sane_reply_net_start)) { | |
0d53778e | 124 | pr_debug("nf_ct_sane: NET_START reply too short\n"); |
6fecd198 MS |
125 | goto out; |
126 | } | |
127 | ||
02e23f40 | 128 | reply = sb_ptr; |
6fecd198 MS |
129 | if (reply->status != htonl(SANE_STATUS_SUCCESS)) { |
130 | /* saned refused the command */ | |
0d53778e PM |
131 | pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n", |
132 | ntohl(reply->status)); | |
6fecd198 MS |
133 | goto out; |
134 | } | |
135 | ||
136 | /* Invalid saned reply? Ignore it. */ | |
137 | if (reply->zero != 0) | |
138 | goto out; | |
139 | ||
6823645d | 140 | exp = nf_ct_expect_alloc(ct); |
6fecd198 MS |
141 | if (exp == NULL) { |
142 | ret = NF_DROP; | |
143 | goto out; | |
144 | } | |
145 | ||
146 | tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; | |
5e8fbe2a | 147 | nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct), |
6002f266 | 148 | &tuple->src.u3, &tuple->dst.u3, |
6823645d | 149 | IPPROTO_TCP, NULL, &reply->port); |
6fecd198 | 150 | |
0d53778e | 151 | pr_debug("nf_ct_sane: expect: "); |
3c9fba65 | 152 | nf_ct_dump_tuple(&exp->tuple); |
6fecd198 MS |
153 | |
154 | /* Can't expect this? Best to drop packet now. */ | |
6823645d | 155 | if (nf_ct_expect_related(exp) != 0) |
6fecd198 MS |
156 | ret = NF_DROP; |
157 | ||
6823645d | 158 | nf_ct_expect_put(exp); |
6fecd198 MS |
159 | |
160 | out: | |
161 | spin_unlock_bh(&nf_sane_lock); | |
162 | return ret; | |
163 | } | |
164 | ||
ec59a111 PM |
165 | static struct nf_conntrack_helper sane[MAX_PORTS][2] __read_mostly; |
166 | static char sane_names[MAX_PORTS][2][sizeof("sane-65535")] __read_mostly; | |
6fecd198 | 167 | |
6002f266 PM |
168 | static const struct nf_conntrack_expect_policy sane_exp_policy = { |
169 | .max_expected = 1, | |
170 | .timeout = 5 * 60, | |
171 | }; | |
172 | ||
6fecd198 MS |
173 | /* don't make this __exit, since it's called from __init ! */ |
174 | static void nf_conntrack_sane_fini(void) | |
175 | { | |
176 | int i, j; | |
177 | ||
178 | for (i = 0; i < ports_c; i++) { | |
179 | for (j = 0; j < 2; j++) { | |
0d53778e PM |
180 | pr_debug("nf_ct_sane: unregistering helper for pf: %d " |
181 | "port: %d\n", | |
182 | sane[i][j].tuple.src.l3num, ports[i]); | |
6fecd198 MS |
183 | nf_conntrack_helper_unregister(&sane[i][j]); |
184 | } | |
185 | } | |
186 | ||
187 | kfree(sane_buffer); | |
188 | } | |
189 | ||
190 | static int __init nf_conntrack_sane_init(void) | |
191 | { | |
192 | int i, j = -1, ret = 0; | |
193 | char *tmpname; | |
194 | ||
195 | sane_buffer = kmalloc(65536, GFP_KERNEL); | |
196 | if (!sane_buffer) | |
197 | return -ENOMEM; | |
198 | ||
199 | if (ports_c == 0) | |
200 | ports[ports_c++] = SANE_PORT; | |
201 | ||
202 | /* FIXME should be configurable whether IPv4 and IPv6 connections | |
203 | are tracked or not - YK */ | |
204 | for (i = 0; i < ports_c; i++) { | |
205 | sane[i][0].tuple.src.l3num = PF_INET; | |
206 | sane[i][1].tuple.src.l3num = PF_INET6; | |
207 | for (j = 0; j < 2; j++) { | |
208 | sane[i][j].tuple.src.u.tcp.port = htons(ports[i]); | |
209 | sane[i][j].tuple.dst.protonum = IPPROTO_TCP; | |
6002f266 | 210 | sane[i][j].expect_policy = &sane_exp_policy; |
6fecd198 MS |
211 | sane[i][j].me = THIS_MODULE; |
212 | sane[i][j].help = help; | |
213 | tmpname = &sane_names[i][j][0]; | |
214 | if (ports[i] == SANE_PORT) | |
215 | sprintf(tmpname, "sane"); | |
216 | else | |
217 | sprintf(tmpname, "sane-%d", ports[i]); | |
218 | sane[i][j].name = tmpname; | |
219 | ||
0d53778e PM |
220 | pr_debug("nf_ct_sane: registering helper for pf: %d " |
221 | "port: %d\n", | |
222 | sane[i][j].tuple.src.l3num, ports[i]); | |
6fecd198 MS |
223 | ret = nf_conntrack_helper_register(&sane[i][j]); |
224 | if (ret) { | |
225 | printk(KERN_ERR "nf_ct_sane: failed to " | |
226 | "register helper for pf: %d port: %d\n", | |
227 | sane[i][j].tuple.src.l3num, ports[i]); | |
228 | nf_conntrack_sane_fini(); | |
229 | return ret; | |
230 | } | |
231 | } | |
232 | } | |
233 | ||
234 | return 0; | |
235 | } | |
236 | ||
237 | module_init(nf_conntrack_sane_init); | |
238 | module_exit(nf_conntrack_sane_fini); |