1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Amanda extension for IP connection tracking
3  *
4  * (C) 2002 by Brian J. Murrell <netfilter@interlinx.bc.ca>
5  * based on HW's ip_conntrack_irc.c as well as other modules
6  * (C) 2006 Patrick McHardy <kaber@trash.net>
7  */
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/moduleparam.h>
11 #include <linux/textsearch.h>
12 #include <linux/skbuff.h>
13 #include <linux/in.h>
14 #include <linux/udp.h>
15 #include <linux/netfilter.h>
16 #include <linux/gfp.h>
17 
18 #include <net/netfilter/nf_conntrack.h>
19 #include <net/netfilter/nf_conntrack_expect.h>
20 #include <net/netfilter/nf_conntrack_ecache.h>
21 #include <net/netfilter/nf_conntrack_helper.h>
22 #include <linux/netfilter/nf_conntrack_amanda.h>
23 
24 static unsigned int master_timeout __read_mostly = 300;
25 static char *ts_algo = "kmp";
26 
27 #define HELPER_NAME "amanda"
28 
29 MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
30 MODULE_DESCRIPTION("Amanda connection tracking module");
31 MODULE_LICENSE("GPL");
32 MODULE_ALIAS("ip_conntrack_amanda");
33 MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
34 
35 module_param(master_timeout, uint, 0600);
36 MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
37 module_param(ts_algo, charp, 0400);
38 MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
39 
40 unsigned int (*nf_nat_amanda_hook)(struct sk_buff *skb,
41 				   enum ip_conntrack_info ctinfo,
42 				   unsigned int protoff,
43 				   unsigned int matchoff,
44 				   unsigned int matchlen,
45 				   struct nf_conntrack_expect *exp)
46 				   __read_mostly;
47 EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
48 
49 enum amanda_strings {
50 	SEARCH_CONNECT,
51 	SEARCH_NEWLINE,
52 	SEARCH_DATA,
53 	SEARCH_MESG,
54 	SEARCH_INDEX,
55 	SEARCH_STATE,
56 };
57 
58 static struct {
59 	const char		*string;
60 	size_t			len;
61 	struct ts_config	*ts;
62 } search[] __read_mostly = {
63 	[SEARCH_CONNECT] = {
64 		.string	= "CONNECT ",
65 		.len	= 8,
66 	},
67 	[SEARCH_NEWLINE] = {
68 		.string	= "\n",
69 		.len	= 1,
70 	},
71 	[SEARCH_DATA] = {
72 		.string	= "DATA ",
73 		.len	= 5,
74 	},
75 	[SEARCH_MESG] = {
76 		.string	= "MESG ",
77 		.len	= 5,
78 	},
79 	[SEARCH_INDEX] = {
80 		.string = "INDEX ",
81 		.len	= 6,
82 	},
83 	[SEARCH_STATE] = {
84 		.string = "STATE ",
85 		.len	= 6,
86 	},
87 };
88 
amanda_help(struct sk_buff * skb,unsigned int protoff,struct nf_conn * ct,enum ip_conntrack_info ctinfo)89 static int amanda_help(struct sk_buff *skb,
90 		       unsigned int protoff,
91 		       struct nf_conn *ct,
92 		       enum ip_conntrack_info ctinfo)
93 {
94 	struct nf_conntrack_expect *exp;
95 	struct nf_conntrack_tuple *tuple;
96 	unsigned int dataoff, start, stop, off, i;
97 	char pbuf[sizeof("65535")], *tmp;
98 	u_int16_t len;
99 	__be16 port;
100 	int ret = NF_ACCEPT;
101 	typeof(nf_nat_amanda_hook) nf_nat_amanda;
102 
103 	/* Only look at packets from the Amanda server */
104 	if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL)
105 		return NF_ACCEPT;
106 
107 	/* increase the UDP timeout of the master connection as replies from
108 	 * Amanda clients to the server can be quite delayed */
109 	nf_ct_refresh(ct, skb, master_timeout * HZ);
110 
111 	/* No data? */
112 	dataoff = protoff + sizeof(struct udphdr);
113 	if (dataoff >= skb->len) {
114 		net_err_ratelimited("amanda_help: skblen = %u\n", skb->len);
115 		return NF_ACCEPT;
116 	}
117 
118 	start = skb_find_text(skb, dataoff, skb->len,
119 			      search[SEARCH_CONNECT].ts);
120 	if (start == UINT_MAX)
121 		goto out;
122 	start += dataoff + search[SEARCH_CONNECT].len;
123 
124 	stop = skb_find_text(skb, start, skb->len,
125 			     search[SEARCH_NEWLINE].ts);
126 	if (stop == UINT_MAX)
127 		goto out;
128 	stop += start;
129 
130 	for (i = SEARCH_DATA; i <= SEARCH_STATE; i++) {
131 		off = skb_find_text(skb, start, stop, search[i].ts);
132 		if (off == UINT_MAX)
133 			continue;
134 		off += start + search[i].len;
135 
136 		len = min_t(unsigned int, sizeof(pbuf) - 1, stop - off);
137 		if (skb_copy_bits(skb, off, pbuf, len))
138 			break;
139 		pbuf[len] = '\0';
140 
141 		port = htons(simple_strtoul(pbuf, &tmp, 10));
142 		len = tmp - pbuf;
143 		if (port == 0 || len > 5)
144 			break;
145 
146 		exp = nf_ct_expect_alloc(ct);
147 		if (exp == NULL) {
148 			nf_ct_helper_log(skb, ct, "cannot alloc expectation");
149 			ret = NF_DROP;
150 			goto out;
151 		}
152 		tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
153 		nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT,
154 				  nf_ct_l3num(ct),
155 				  &tuple->src.u3, &tuple->dst.u3,
156 				  IPPROTO_TCP, NULL, &port);
157 
158 		nf_nat_amanda = rcu_dereference(nf_nat_amanda_hook);
159 		if (nf_nat_amanda && ct->status & IPS_NAT_MASK)
160 			ret = nf_nat_amanda(skb, ctinfo, protoff,
161 					    off - dataoff, len, exp);
162 		else if (nf_ct_expect_related(exp, 0) != 0) {
163 			nf_ct_helper_log(skb, ct, "cannot add expectation");
164 			ret = NF_DROP;
165 		}
166 		nf_ct_expect_put(exp);
167 	}
168 
169 out:
170 	return ret;
171 }
172 
173 static const struct nf_conntrack_expect_policy amanda_exp_policy = {
174 	.max_expected		= 4,
175 	.timeout		= 180,
176 };
177 
178 static struct nf_conntrack_helper amanda_helper[2] __read_mostly = {
179 	{
180 		.name			= HELPER_NAME,
181 		.me			= THIS_MODULE,
182 		.help			= amanda_help,
183 		.tuple.src.l3num	= AF_INET,
184 		.tuple.src.u.udp.port	= cpu_to_be16(10080),
185 		.tuple.dst.protonum	= IPPROTO_UDP,
186 		.expect_policy		= &amanda_exp_policy,
187 		.nat_mod_name		= NF_NAT_HELPER_NAME(HELPER_NAME),
188 	},
189 	{
190 		.name			= "amanda",
191 		.me			= THIS_MODULE,
192 		.help			= amanda_help,
193 		.tuple.src.l3num	= AF_INET6,
194 		.tuple.src.u.udp.port	= cpu_to_be16(10080),
195 		.tuple.dst.protonum	= IPPROTO_UDP,
196 		.expect_policy		= &amanda_exp_policy,
197 		.nat_mod_name		= NF_NAT_HELPER_NAME(HELPER_NAME),
198 	},
199 };
200 
nf_conntrack_amanda_fini(void)201 static void __exit nf_conntrack_amanda_fini(void)
202 {
203 	int i;
204 
205 	nf_conntrack_helpers_unregister(amanda_helper,
206 					ARRAY_SIZE(amanda_helper));
207 	for (i = 0; i < ARRAY_SIZE(search); i++)
208 		textsearch_destroy(search[i].ts);
209 }
210 
nf_conntrack_amanda_init(void)211 static int __init nf_conntrack_amanda_init(void)
212 {
213 	int ret, i;
214 
215 	NF_CT_HELPER_BUILD_BUG_ON(0);
216 
217 	for (i = 0; i < ARRAY_SIZE(search); i++) {
218 		search[i].ts = textsearch_prepare(ts_algo, search[i].string,
219 						  search[i].len,
220 						  GFP_KERNEL, TS_AUTOLOAD);
221 		if (IS_ERR(search[i].ts)) {
222 			ret = PTR_ERR(search[i].ts);
223 			goto err1;
224 		}
225 	}
226 	ret = nf_conntrack_helpers_register(amanda_helper,
227 					    ARRAY_SIZE(amanda_helper));
228 	if (ret < 0)
229 		goto err1;
230 	return 0;
231 
232 err1:
233 	while (--i >= 0)
234 		textsearch_destroy(search[i].ts);
235 
236 	return ret;
237 }
238 
239 module_init(nf_conntrack_amanda_init);
240 module_exit(nf_conntrack_amanda_fini);
241