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d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
6fecd198 MS |
2 | /* SANE connection tracking helper |
3 | * (SANE = Scanner Access Now Easy) | |
4 | * For documentation about the SANE network protocol see | |
5 | * http://www.sane-project.org/html/doc015.html | |
6 | */ | |
7 | ||
8 | /* Copyright (C) 2007 Red Hat, Inc. | |
9 | * Author: Michal Schmidt <mschmidt@redhat.com> | |
10 | * Based on the FTP conntrack helper (net/netfilter/nf_conntrack_ftp.c): | |
11 | * (C) 1999-2001 Paul `Rusty' Russell | |
12 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> | |
13 | * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org> | |
14 | * (C) 2003 Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp> | |
6fecd198 MS |
15 | */ |
16 | ||
ad6d9503 PNA |
17 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
18 | ||
6fecd198 MS |
19 | #include <linux/module.h> |
20 | #include <linux/moduleparam.h> | |
21 | #include <linux/netfilter.h> | |
5a0e3ad6 | 22 | #include <linux/slab.h> |
6fecd198 MS |
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 | ||
08010a21 FL |
30 | #define HELPER_NAME "sane" |
31 | ||
6fecd198 MS |
32 | MODULE_LICENSE("GPL"); |
33 | MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>"); | |
34 | MODULE_DESCRIPTION("SANE connection tracking helper"); | |
08010a21 | 35 | MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); |
6fecd198 MS |
36 | |
37 | static char *sane_buffer; | |
38 | ||
39 | static DEFINE_SPINLOCK(nf_sane_lock); | |
40 | ||
41 | #define MAX_PORTS 8 | |
42 | static u_int16_t ports[MAX_PORTS]; | |
43 | static unsigned int ports_c; | |
44 | module_param_array(ports, ushort, &ports_c, 0400); | |
45 | ||
6fecd198 MS |
46 | struct sane_request { |
47 | __be32 RPC_code; | |
48 | #define SANE_NET_START 7 /* RPC code */ | |
49 | ||
50 | __be32 handle; | |
51 | }; | |
52 | ||
53 | struct sane_reply_net_start { | |
54 | __be32 status; | |
55 | #define SANE_STATUS_SUCCESS 0 | |
56 | ||
57 | __be16 zero; | |
58 | __be16 port; | |
59 | /* other fields aren't interesting for conntrack */ | |
60 | }; | |
61 | ||
3db05fea | 62 | static int help(struct sk_buff *skb, |
6fecd198 MS |
63 | unsigned int protoff, |
64 | struct nf_conn *ct, | |
65 | enum ip_conntrack_info ctinfo) | |
66 | { | |
67 | unsigned int dataoff, datalen; | |
02e23f40 JE |
68 | const struct tcphdr *th; |
69 | struct tcphdr _tcph; | |
70 | void *sb_ptr; | |
6fecd198 MS |
71 | int ret = NF_ACCEPT; |
72 | int dir = CTINFO2DIR(ctinfo); | |
1afc5679 | 73 | struct nf_ct_sane_master *ct_sane_info = nfct_help_data(ct); |
6fecd198 MS |
74 | struct nf_conntrack_expect *exp; |
75 | struct nf_conntrack_tuple *tuple; | |
76 | struct sane_request *req; | |
77 | struct sane_reply_net_start *reply; | |
6fecd198 | 78 | |
6fecd198 MS |
79 | /* Until there's been traffic both ways, don't look in packets. */ |
80 | if (ctinfo != IP_CT_ESTABLISHED && | |
fb048833 | 81 | ctinfo != IP_CT_ESTABLISHED_REPLY) |
6fecd198 MS |
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)) { | |
ad6d9503 | 124 | pr_debug("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 */ | |
ad6d9503 | 131 | pr_debug("unsuccessful SANE_STATUS = %u\n", |
0d53778e | 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 | 141 | if (exp == NULL) { |
b20ab9cc | 142 | nf_ct_helper_log(skb, ct, "cannot alloc expectation"); |
6fecd198 MS |
143 | ret = NF_DROP; |
144 | goto out; | |
145 | } | |
146 | ||
147 | tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; | |
5e8fbe2a | 148 | nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct), |
6002f266 | 149 | &tuple->src.u3, &tuple->dst.u3, |
6823645d | 150 | IPPROTO_TCP, NULL, &reply->port); |
6fecd198 | 151 | |
ad6d9503 | 152 | pr_debug("expect: "); |
3c9fba65 | 153 | nf_ct_dump_tuple(&exp->tuple); |
6fecd198 MS |
154 | |
155 | /* Can't expect this? Best to drop packet now. */ | |
3c00fb0b | 156 | if (nf_ct_expect_related(exp, 0) != 0) { |
b20ab9cc | 157 | nf_ct_helper_log(skb, ct, "cannot add expectation"); |
6fecd198 | 158 | ret = NF_DROP; |
b20ab9cc | 159 | } |
6fecd198 | 160 | |
6823645d | 161 | nf_ct_expect_put(exp); |
6fecd198 MS |
162 | |
163 | out: | |
164 | spin_unlock_bh(&nf_sane_lock); | |
165 | return ret; | |
166 | } | |
167 | ||
82de0be6 | 168 | static struct nf_conntrack_helper sane[MAX_PORTS * 2] __read_mostly; |
6fecd198 | 169 | |
6002f266 PM |
170 | static const struct nf_conntrack_expect_policy sane_exp_policy = { |
171 | .max_expected = 1, | |
172 | .timeout = 5 * 60, | |
173 | }; | |
174 | ||
35341a61 | 175 | static void __exit nf_conntrack_sane_fini(void) |
6fecd198 | 176 | { |
82de0be6 | 177 | nf_conntrack_helpers_unregister(sane, ports_c * 2); |
6fecd198 MS |
178 | kfree(sane_buffer); |
179 | } | |
180 | ||
181 | static int __init nf_conntrack_sane_init(void) | |
182 | { | |
82de0be6 | 183 | int i, ret = 0; |
6fecd198 | 184 | |
dcf67740 FW |
185 | NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_sane_master)); |
186 | ||
6fecd198 MS |
187 | sane_buffer = kmalloc(65536, GFP_KERNEL); |
188 | if (!sane_buffer) | |
189 | return -ENOMEM; | |
190 | ||
191 | if (ports_c == 0) | |
192 | ports[ports_c++] = SANE_PORT; | |
193 | ||
194 | /* FIXME should be configurable whether IPv4 and IPv6 connections | |
195 | are tracked or not - YK */ | |
196 | for (i = 0; i < ports_c; i++) { | |
08010a21 FL |
197 | nf_ct_helper_init(&sane[2 * i], AF_INET, IPPROTO_TCP, |
198 | HELPER_NAME, SANE_PORT, ports[i], ports[i], | |
9f0f3ebe | 199 | &sane_exp_policy, 0, help, NULL, |
82de0be6 | 200 | THIS_MODULE); |
08010a21 FL |
201 | nf_ct_helper_init(&sane[2 * i + 1], AF_INET6, IPPROTO_TCP, |
202 | HELPER_NAME, SANE_PORT, ports[i], ports[i], | |
9f0f3ebe | 203 | &sane_exp_policy, 0, help, NULL, |
82de0be6 GF |
204 | THIS_MODULE); |
205 | } | |
206 | ||
207 | ret = nf_conntrack_helpers_register(sane, ports_c * 2); | |
208 | if (ret < 0) { | |
209 | pr_err("failed to register helpers\n"); | |
210 | kfree(sane_buffer); | |
211 | return ret; | |
6fecd198 MS |
212 | } |
213 | ||
214 | return 0; | |
215 | } | |
216 | ||
217 | module_init(nf_conntrack_sane_init); | |
218 | module_exit(nf_conntrack_sane_fini); |