1 #include <linux/types.h>
2 #include <linux/module.h>
4 #include <linux/ipv6.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>
13 MODULE_DESCRIPTION("x_tables match for TCP and UDP(-Lite), supports IPv4 and IPv6");
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");
22 #ifdef DEBUG_IP_FIREWALL_USER
23 #define duprintf(format, args...) printk(format , ## args)
25 #define duprintf(format, args...)
29 /* Returns 1 if the port is matched by the range, 0 otherwise */
31 port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
33 return (port >= min && port <= max) ^ invert;
37 tcp_find_option(u_int8_t option,
38 const struct sk_buff *skb,
44 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
45 u_int8_t _opt[60 - sizeof(struct tcphdr)], *op;
48 duprintf("tcp_match: finding option\n");
53 /* If we don't have the whole header, drop packet. */
54 op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
61 for (i = 0; i < optlen; ) {
62 if (op[i] == option) return !invert;
71 tcp_mt(const struct sk_buff *skb, const struct net_device *in,
72 const struct net_device *out, const struct xt_match *match,
73 const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
75 struct tcphdr _tcph, *th;
76 const struct xt_tcp *tcpinfo = matchinfo;
81 Don't allow a fragment of TCP 8 bytes in. Nobody normal
82 causes this. Its a cracker trying to break in by doing a
83 flag overwrite to pass the direction checks.
86 duprintf("Dropping evil TCP offset=1 frag.\n");
89 /* Must not be a fragment. */
93 #define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg)))
95 th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph);
97 /* We've been asked to examine this packet, and we
98 can't. Hence, no choice but to drop. */
99 duprintf("Dropping evil TCP offset=0 tinygram.\n");
104 if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
106 !!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
108 if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
110 !!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
112 if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask)
116 if (tcpinfo->option) {
117 if (th->doff * 4 < sizeof(_tcph)) {
121 if (!tcp_find_option(tcpinfo->option, skb, protoff,
122 th->doff*4 - sizeof(_tcph),
123 tcpinfo->invflags & XT_TCP_INV_OPTION,
130 /* Called when user tries to insert an entry of this type. */
132 tcp_mt_check(const char *tablename, const void *info,
133 const struct xt_match *match, void *matchinfo,
134 unsigned int hook_mask)
136 const struct xt_tcp *tcpinfo = matchinfo;
138 /* Must specify no unknown invflags */
139 return !(tcpinfo->invflags & ~XT_TCP_INV_MASK);
143 udp_mt(const struct sk_buff *skb, const struct net_device *in,
144 const struct net_device *out, const struct xt_match *match,
145 const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop)
147 struct udphdr _udph, *uh;
148 const struct xt_udp *udpinfo = matchinfo;
150 /* Must not be a fragment. */
154 uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph);
156 /* We've been asked to examine this packet, and we
157 can't. Hence, no choice but to drop. */
158 duprintf("Dropping evil UDP tinygram.\n");
163 return port_match(udpinfo->spts[0], udpinfo->spts[1],
165 !!(udpinfo->invflags & XT_UDP_INV_SRCPT))
166 && port_match(udpinfo->dpts[0], udpinfo->dpts[1],
168 !!(udpinfo->invflags & XT_UDP_INV_DSTPT));
171 /* Called when user tries to insert an entry of this type. */
173 udp_mt_check(const char *tablename, const void *info,
174 const struct xt_match *match, void *matchinfo,
175 unsigned int hook_mask)
177 const struct xt_udp *udpinfo = matchinfo;
179 /* Must specify no unknown invflags */
180 return !(udpinfo->invflags & ~XT_UDP_INV_MASK);
183 static struct xt_match tcpudp_mt_reg[] __read_mostly = {
187 .checkentry = tcp_mt_check,
189 .matchsize = sizeof(struct xt_tcp),
190 .proto = IPPROTO_TCP,
196 .checkentry = tcp_mt_check,
198 .matchsize = sizeof(struct xt_tcp),
199 .proto = IPPROTO_TCP,
205 .checkentry = udp_mt_check,
207 .matchsize = sizeof(struct xt_udp),
208 .proto = IPPROTO_UDP,
214 .checkentry = udp_mt_check,
216 .matchsize = sizeof(struct xt_udp),
217 .proto = IPPROTO_UDP,
223 .checkentry = udp_mt_check,
225 .matchsize = sizeof(struct xt_udp),
226 .proto = IPPROTO_UDPLITE,
232 .checkentry = udp_mt_check,
234 .matchsize = sizeof(struct xt_udp),
235 .proto = IPPROTO_UDPLITE,
240 static int __init tcpudp_mt_init(void)
242 return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
245 static void __exit tcpudp_mt_exit(void)
247 xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
250 module_init(tcpudp_mt_init);
251 module_exit(tcpudp_mt_exit);