nf_conntrack_amanda.c

  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
 24static unsigned int master_timeout __read_mostly = 300;
 25static char *ts_algo = "kmp";
 26
 27#define HELPER_NAME "amanda"
 28
 29MODULE_AUTHOR("Brian J. Murrell <netfilter@interlinx.bc.ca>");
 30MODULE_DESCRIPTION("Amanda connection tracking module");
 31MODULE_LICENSE("GPL");
 32MODULE_ALIAS("ip_conntrack_amanda");
 33MODULE_ALIAS_NFCT_HELPER(HELPER_NAME);
 34
 35module_param(master_timeout, uint, 0600);
 36MODULE_PARM_DESC(master_timeout, "timeout for the master connection");
 37module_param(ts_algo, charp, 0400);
 38MODULE_PARM_DESC(ts_algo, "textsearch algorithm to use (default kmp)");
 39
 40unsigned 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;
 47EXPORT_SYMBOL_GPL(nf_nat_amanda_hook);
 48
 49enum amanda_strings {
 50	SEARCH_CONNECT,
 51	SEARCH_NEWLINE,
 52	SEARCH_DATA,
 53	SEARCH_MESG,
 54	SEARCH_INDEX,
 55	SEARCH_STATE,
 56};
 57
 58static 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
 89static 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, 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
169out:
170	return ret;
171}
172
173static const struct nf_conntrack_expect_policy amanda_exp_policy = {
174	.max_expected		= 4,
175	.timeout		= 180,
176};
177
178static 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
201static 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
211static 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
232err1:
233	while (--i >= 0)
234		textsearch_destroy(search[i].ts);
235
236	return ret;
237}
238
239module_init(nf_conntrack_amanda_init);
240module_exit(nf_conntrack_amanda_fini);