1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20#include <linux/module.h>
21#include <linux/moduleparam.h>
22#include <linux/netfilter.h>
23#include <linux/slab.h>
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
31MODULE_LICENSE("GPL");
32MODULE_AUTHOR("Michal Schmidt <mschmidt@redhat.com>");
33MODULE_DESCRIPTION("SANE connection tracking helper");
34MODULE_ALIAS_NFCT_HELPER("sane");
35
36static char *sane_buffer;
37
38static DEFINE_SPINLOCK(nf_sane_lock);
39
40#define MAX_PORTS 8
41static u_int16_t ports[MAX_PORTS];
42static unsigned int ports_c;
43module_param_array(ports, ushort, &ports_c, 0400);
44
45struct sane_request {
46 __be32 RPC_code;
47#define SANE_NET_START 7
48
49 __be32 handle;
50};
51
52struct sane_reply_net_start {
53 __be32 status;
54#define SANE_STATUS_SUCCESS 0
55
56 __be16 zero;
57 __be16 port;
58
59};
60
61static int help(struct sk_buff *skb,
62 unsigned int protoff,
63 struct nf_conn *ct,
64 enum ip_conntrack_info ctinfo)
65{
66 unsigned int dataoff, datalen;
67 const struct tcphdr *th;
68 struct tcphdr _tcph;
69 void *sb_ptr;
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;
77
78 ct_sane_info = &nfct_help(ct)->help.ct_sane_info;
79
80 if (ctinfo != IP_CT_ESTABLISHED &&
81 ctinfo != IP_CT_ESTABLISHED_REPLY)
82 return NF_ACCEPT;
83
84
85 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
86 if (th == NULL)
87 return NF_ACCEPT;
88
89
90 dataoff = protoff + th->doff * 4;
91 if (dataoff >= skb->len)
92 return NF_ACCEPT;
93
94 datalen = skb->len - dataoff;
95
96 spin_lock_bh(&nf_sane_lock);
97 sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer);
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
104 req = sb_ptr;
105 if (req->RPC_code != htonl(SANE_NET_START)) {
106
107 ct_sane_info->state = SANE_STATE_NORMAL;
108 goto out;
109 }
110
111
112 ct_sane_info->state = SANE_STATE_START_REQUESTED;
113 goto out;
114 }
115
116
117 if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
118 goto out;
119
120
121 ct_sane_info->state = SANE_STATE_NORMAL;
122
123 if (datalen < sizeof(struct sane_reply_net_start)) {
124 pr_debug("nf_ct_sane: NET_START reply too short\n");
125 goto out;
126 }
127
128 reply = sb_ptr;
129 if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
130
131 pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n",
132 ntohl(reply->status));
133 goto out;
134 }
135
136
137 if (reply->zero != 0)
138 goto out;
139
140 exp = nf_ct_expect_alloc(ct);
141 if (exp == NULL) {
142 ret = NF_DROP;
143 goto out;
144 }
145
146 tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
147 nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, nf_ct_l3num(ct),
148 &tuple->src.u3, &tuple->dst.u3,
149 IPPROTO_TCP, NULL, &reply->port);
150
151 pr_debug("nf_ct_sane: expect: ");
152 nf_ct_dump_tuple(&exp->tuple);
153
154
155 if (nf_ct_expect_related(exp) != 0)
156 ret = NF_DROP;
157
158 nf_ct_expect_put(exp);
159
160out:
161 spin_unlock_bh(&nf_sane_lock);
162 return ret;
163}
164
165static struct nf_conntrack_helper sane[MAX_PORTS][2] __read_mostly;
166static char sane_names[MAX_PORTS][2][sizeof("sane-65535")] __read_mostly;
167
168static const struct nf_conntrack_expect_policy sane_exp_policy = {
169 .max_expected = 1,
170 .timeout = 5 * 60,
171};
172
173
174static 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++) {
180 pr_debug("nf_ct_sane: unregistering helper for pf: %d "
181 "port: %d\n",
182 sane[i][j].tuple.src.l3num, ports[i]);
183 nf_conntrack_helper_unregister(&sane[i][j]);
184 }
185 }
186
187 kfree(sane_buffer);
188}
189
190static 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
203
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;
210 sane[i][j].expect_policy = &sane_exp_policy;
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
220 pr_debug("nf_ct_sane: registering helper for pf: %d "
221 "port: %d\n",
222 sane[i][j].tuple.src.l3num, ports[i]);
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
237module_init(nf_conntrack_sane_init);
238module_exit(nf_conntrack_sane_fini);
239
