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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 = nfct_help_data(ct);
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
79 if (ctinfo != IP_CT_ESTABLISHED &&
80 ctinfo != IP_CT_ESTABLISHED_REPLY)
81 return NF_ACCEPT;
82
83
84 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
85 if (th == NULL)
86 return NF_ACCEPT;
87
88
89 dataoff = protoff + th->doff * 4;
90 if (dataoff >= skb->len)
91 return NF_ACCEPT;
92
93 datalen = skb->len - dataoff;
94
95 spin_lock_bh(&nf_sane_lock);
96 sb_ptr = skb_header_pointer(skb, dataoff, datalen, sane_buffer);
97 BUG_ON(sb_ptr == NULL);
98
99 if (dir == IP_CT_DIR_ORIGINAL) {
100 if (datalen != sizeof(struct sane_request))
101 goto out;
102
103 req = sb_ptr;
104 if (req->RPC_code != htonl(SANE_NET_START)) {
105
106 ct_sane_info->state = SANE_STATE_NORMAL;
107 goto out;
108 }
109
110
111 ct_sane_info->state = SANE_STATE_START_REQUESTED;
112 goto out;
113 }
114
115
116 if (ct_sane_info->state != SANE_STATE_START_REQUESTED)
117 goto out;
118
119
120 ct_sane_info->state = SANE_STATE_NORMAL;
121
122 if (datalen < sizeof(struct sane_reply_net_start)) {
123 pr_debug("nf_ct_sane: NET_START reply too short\n");
124 goto out;
125 }
126
127 reply = sb_ptr;
128 if (reply->status != htonl(SANE_STATUS_SUCCESS)) {
129
130 pr_debug("nf_ct_sane: unsuccessful SANE_STATUS = %u\n",
131 ntohl(reply->status));
132 goto out;
133 }
134
135
136 if (reply->zero != 0)
137 goto out;
138
139 exp = nf_ct_expect_alloc(ct);
140 if (exp == NULL) {
141 nf_ct_helper_log(skb, ct, "cannot alloc expectation");
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 nf_ct_helper_log(skb, ct, "cannot add expectation");
157 ret = NF_DROP;
158 }
159
160 nf_ct_expect_put(exp);
161
162out:
163 spin_unlock_bh(&nf_sane_lock);
164 return ret;
165}
166
167static struct nf_conntrack_helper sane[MAX_PORTS][2] __read_mostly;
168
169static const struct nf_conntrack_expect_policy sane_exp_policy = {
170 .max_expected = 1,
171 .timeout = 5 * 60,
172};
173
174
175static void nf_conntrack_sane_fini(void)
176{
177 int i, j;
178
179 for (i = 0; i < ports_c; i++) {
180 for (j = 0; j < 2; j++) {
181 pr_debug("nf_ct_sane: unregistering helper for pf: %d "
182 "port: %d\n",
183 sane[i][j].tuple.src.l3num, ports[i]);
184 nf_conntrack_helper_unregister(&sane[i][j]);
185 }
186 }
187
188 kfree(sane_buffer);
189}
190
191static int __init nf_conntrack_sane_init(void)
192{
193 int i, j = -1, ret = 0;
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].data_len = sizeof(struct nf_ct_sane_master);
209 sane[i][j].tuple.src.u.tcp.port = htons(ports[i]);
210 sane[i][j].tuple.dst.protonum = IPPROTO_TCP;
211 sane[i][j].expect_policy = &sane_exp_policy;
212 sane[i][j].me = THIS_MODULE;
213 sane[i][j].help = help;
214 if (ports[i] == SANE_PORT)
215 sprintf(sane[i][j].name, "sane");
216 else
217 sprintf(sane[i][j].name, "sane-%d", ports[i]);
218
219 pr_debug("nf_ct_sane: registering helper for pf: %d "
220 "port: %d\n",
221 sane[i][j].tuple.src.l3num, ports[i]);
222 ret = nf_conntrack_helper_register(&sane[i][j]);
223 if (ret) {
224 printk(KERN_ERR "nf_ct_sane: failed to "
225 "register helper for pf: %d port: %d\n",
226 sane[i][j].tuple.src.l3num, ports[i]);
227 nf_conntrack_sane_fini();
228 return ret;
229 }
230 }
231 }
232
233 return 0;
234}
235
236module_init(nf_conntrack_sane_init);
237module_exit(nf_conntrack_sane_fini);
238
