Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6.git] / net / netfilter / xt_tcpudp.c
1 #include <linux/types.h>
2 #include <linux/module.h>
3 #include <net/ip.h>
4 #include <linux/ipv6.h>
5 #include <net/ipv6.h>
6 #include <net/tcp.h>
7 #include <net/udp.h>
8 #include <linux/netfilter/x_tables.h>
9 #include <linux/netfilter/xt_tcpudp.h>
10 #include <linux/netfilter_ipv4/ip_tables.h>
11 #include <linux/netfilter_ipv6/ip6_tables.h>
12
13 MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
14 MODULE_LICENSE("GPL");
15 MODULE_ALIAS("xt_tcp");
16 MODULE_ALIAS("xt_udp");
17 MODULE_ALIAS("ipt_udp");
18 MODULE_ALIAS("ipt_tcp");
19 MODULE_ALIAS("ip6t_udp");
20 MODULE_ALIAS("ip6t_tcp");
21
22 #ifdef DEBUG_IP_FIREWALL_USER
23 #define duprintf(format, args...) printk(format , ## args)
24 #else
25 #define duprintf(format, args...)
26 #endif
27
28
29 /* Returns 1 if the port is matched by the range, 0 otherwise */
30 static inline bool
31 port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
32 {
33         return (port >= min && port <= max) ^ invert;
34 }
35
36 static bool
37 tcp_find_option(u_int8_t option,
38                 const struct sk_buff *skb,
39                 unsigned int protoff,
40                 unsigned int optlen,
41                 bool invert,
42                 bool *hotdrop)
43 {
44         /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
45         const u_int8_t *op;
46         u_int8_t _opt[60 - sizeof(struct tcphdr)];
47         unsigned int i;
48
49         duprintf("tcp_match: finding option\n");
50
51         if (!optlen)
52                 return invert;
53
54         /* If we don't have the whole header, drop packet. */
55         op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
56                                 optlen, _opt);
57         if (op == NULL) {
58                 *hotdrop = true;
59                 return false;
60         }
61
62         for (i = 0; i < optlen; ) {
63                 if (op[i] == option) return !invert;
64                 if (op[i] < 2) i++;
65                 else i += op[i+1]?:1;
66         }
67
68         return invert;
69 }
70
71 static bool tcp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
72 {
73         const struct tcphdr *th;
74         struct tcphdr _tcph;
75         const struct xt_tcp *tcpinfo = par->matchinfo;
76
77         if (par->fragoff != 0) {
78                 /* To quote Alan:
79
80                    Don't allow a fragment of TCP 8 bytes in. Nobody normal
81                    causes this. Its a cracker trying to break in by doing a
82                    flag overwrite to pass the direction checks.
83                 */
84                 if (par->fragoff == 1) {
85                         duprintf("Dropping evil TCP offset=1 frag.\n");
86                         *par->hotdrop = true;
87                 }
88                 /* Must not be a fragment. */
89                 return false;
90         }
91
92 #define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))
93
94         th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
95         if (th == NULL) {
96                 /* We've been asked to examine this packet, and we
97                    can't.  Hence, no choice but to drop. */
98                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
99                 *par->hotdrop = true;
100                 return false;
101         }
102
103         if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
104                         ntohs(th->source),
105                         !!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
106                 return false;
107         if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
108                         ntohs(th->dest),
109                         !!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
110                 return false;
111         if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
112                       == tcpinfo->flg_cmp,
113                       XT_TCP_INV_FLAGS))
114                 return false;
115         if (tcpinfo->option) {
116                 if (th->doff * 4 < sizeof(_tcph)) {
117                         *par->hotdrop = true;
118                         return false;
119                 }
120                 if (!tcp_find_option(tcpinfo->option, skb, par->thoff,
121                                      th->doff*4 - sizeof(_tcph),
122                                      tcpinfo->invflags & XT_TCP_INV_OPTION,
123                                      par->hotdrop))
124                         return false;
125         }
126         return true;
127 }
128
129 static bool tcp_mt_check(const struct xt_mtchk_param *par)
130 {
131         const struct xt_tcp *tcpinfo = par->matchinfo;
132
133         /* Must specify no unknown invflags */
134         return !(tcpinfo->invflags & ~XT_TCP_INV_MASK);
135 }
136
137 static bool udp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
138 {
139         const struct udphdr *uh;
140         struct udphdr _udph;
141         const struct xt_udp *udpinfo = par->matchinfo;
142
143         /* Must not be a fragment. */
144         if (par->fragoff != 0)
145                 return false;
146
147         uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
148         if (uh == NULL) {
149                 /* We've been asked to examine this packet, and we
150                    can't.  Hence, no choice but to drop. */
151                 duprintf("Dropping evil UDP tinygram.\n");
152                 *par->hotdrop = true;
153                 return false;
154         }
155
156         return port_match(udpinfo->spts[0], udpinfo->spts[1],
157                           ntohs(uh->source),
158                           !!(udpinfo->invflags & XT_UDP_INV_SRCPT))
159                 && port_match(udpinfo->dpts[0], udpinfo->dpts[1],
160                               ntohs(uh->dest),
161                               !!(udpinfo->invflags & XT_UDP_INV_DSTPT));
162 }
163
164 static bool udp_mt_check(const struct xt_mtchk_param *par)
165 {
166         const struct xt_udp *udpinfo = par->matchinfo;
167
168         /* Must specify no unknown invflags */
169         return !(udpinfo->invflags & ~XT_UDP_INV_MASK);
170 }
171
172 static struct xt_match tcpudp_mt_reg[] __read_mostly = {
173         {
174                 .name           = "tcp",
175                 .family         = NFPROTO_IPV4,
176                 .checkentry     = tcp_mt_check,
177                 .match          = tcp_mt,
178                 .matchsize      = sizeof(struct xt_tcp),
179                 .proto          = IPPROTO_TCP,
180                 .me             = THIS_MODULE,
181         },
182         {
183                 .name           = "tcp",
184                 .family         = NFPROTO_IPV6,
185                 .checkentry     = tcp_mt_check,
186                 .match          = tcp_mt,
187                 .matchsize      = sizeof(struct xt_tcp),
188                 .proto          = IPPROTO_TCP,
189                 .me             = THIS_MODULE,
190         },
191         {
192                 .name           = "udp",
193                 .family         = NFPROTO_IPV4,
194                 .checkentry     = udp_mt_check,
195                 .match          = udp_mt,
196                 .matchsize      = sizeof(struct xt_udp),
197                 .proto          = IPPROTO_UDP,
198                 .me             = THIS_MODULE,
199         },
200         {
201                 .name           = "udp",
202                 .family         = NFPROTO_IPV6,
203                 .checkentry     = udp_mt_check,
204                 .match          = udp_mt,
205                 .matchsize      = sizeof(struct xt_udp),
206                 .proto          = IPPROTO_UDP,
207                 .me             = THIS_MODULE,
208         },
209         {
210                 .name           = "udplite",
211                 .family         = NFPROTO_IPV4,
212                 .checkentry     = udp_mt_check,
213                 .match          = udp_mt,
214                 .matchsize      = sizeof(struct xt_udp),
215                 .proto          = IPPROTO_UDPLITE,
216                 .me             = THIS_MODULE,
217         },
218         {
219                 .name           = "udplite",
220                 .family         = NFPROTO_IPV6,
221                 .checkentry     = udp_mt_check,
222                 .match          = udp_mt,
223                 .matchsize      = sizeof(struct xt_udp),
224                 .proto          = IPPROTO_UDPLITE,
225                 .me             = THIS_MODULE,
226         },
227 };
228
229 static int __init tcpudp_mt_init(void)
230 {
231         return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
232 }
233
234 static void __exit tcpudp_mt_exit(void)
235 {
236         xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
237 }
238
239 module_init(tcpudp_mt_init);
240 module_exit(tcpudp_mt_exit);