1 // SPDX-License-Identifier: GPL-2.0-only
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3 #include <linux/types.h>
4 #include <linux/module.h>
6 #include <linux/ipv6.h>
7 #include <linux/icmp.h>
11 #include <linux/netfilter/x_tables.h>
12 #include <linux/netfilter/xt_tcpudp.h>
13 #include <linux/netfilter_ipv4/ip_tables.h>
14 #include <linux/netfilter_ipv6/ip6_tables.h>
16 MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match");
17 MODULE_LICENSE("GPL");
18 MODULE_ALIAS("xt_tcp");
19 MODULE_ALIAS("xt_udp");
20 MODULE_ALIAS("ipt_udp");
21 MODULE_ALIAS("ipt_tcp");
22 MODULE_ALIAS("ip6t_udp");
23 MODULE_ALIAS("ip6t_tcp");
24 MODULE_ALIAS("ipt_icmp");
25 MODULE_ALIAS("ip6t_icmp6");
27 /* Returns 1 if the port is matched by the range, 0 otherwise */
29 port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert)
31 return (port >= min && port <= max) ^ invert;
35 tcp_find_option(u_int8_t option,
36 const struct sk_buff *skb,
42 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
44 u_int8_t _opt[60 - sizeof(struct tcphdr)];
47 pr_debug("finding option\n");
52 /* If we don't have the whole header, drop packet. */
53 op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr),
60 for (i = 0; i < optlen; ) {
61 if (op[i] == option) return !invert;
69 static bool tcp_mt(const struct sk_buff *skb, struct xt_action_param *par)
71 const struct tcphdr *th;
73 const struct xt_tcp *tcpinfo = par->matchinfo;
75 if (par->fragoff != 0) {
78 Don't allow a fragment of TCP 8 bytes in. Nobody normal
79 causes this. Its a cracker trying to break in by doing a
80 flag overwrite to pass the direction checks.
82 if (par->fragoff == 1) {
83 pr_debug("Dropping evil TCP offset=1 frag.\n");
86 /* Must not be a fragment. */
90 th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph);
92 /* We've been asked to examine this packet, and we
93 can't. Hence, no choice but to drop. */
94 pr_debug("Dropping evil TCP offset=0 tinygram.\n");
99 if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1],
101 !!(tcpinfo->invflags & XT_TCP_INV_SRCPT)))
103 if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1],
105 !!(tcpinfo->invflags & XT_TCP_INV_DSTPT)))
107 if (!NF_INVF(tcpinfo, XT_TCP_INV_FLAGS,
108 (((unsigned char *)th)[13] & tcpinfo->flg_mask) == tcpinfo->flg_cmp))
110 if (tcpinfo->option) {
111 if (th->doff * 4 < sizeof(_tcph)) {
115 if (!tcp_find_option(tcpinfo->option, skb, par->thoff,
116 th->doff*4 - sizeof(_tcph),
117 tcpinfo->invflags & XT_TCP_INV_OPTION,
124 static int tcp_mt_check(const struct xt_mtchk_param *par)
126 const struct xt_tcp *tcpinfo = par->matchinfo;
128 /* Must specify no unknown invflags */
129 return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0;
132 static bool udp_mt(const struct sk_buff *skb, struct xt_action_param *par)
134 const struct udphdr *uh;
136 const struct xt_udp *udpinfo = par->matchinfo;
138 /* Must not be a fragment. */
139 if (par->fragoff != 0)
142 uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph);
144 /* We've been asked to examine this packet, and we
145 can't. Hence, no choice but to drop. */
146 pr_debug("Dropping evil UDP tinygram.\n");
151 return port_match(udpinfo->spts[0], udpinfo->spts[1],
153 !!(udpinfo->invflags & XT_UDP_INV_SRCPT))
154 && port_match(udpinfo->dpts[0], udpinfo->dpts[1],
156 !!(udpinfo->invflags & XT_UDP_INV_DSTPT));
159 static int udp_mt_check(const struct xt_mtchk_param *par)
161 const struct xt_udp *udpinfo = par->matchinfo;
163 /* Must specify no unknown invflags */
164 return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0;
167 /* Returns 1 if the type and code is matched by the range, 0 otherwise */
168 static bool type_code_in_range(u8 test_type, u8 min_code, u8 max_code,
171 return type == test_type && code >= min_code && code <= max_code;
174 static bool icmp_type_code_match(u8 test_type, u8 min_code, u8 max_code,
175 u8 type, u8 code, bool invert)
177 return (test_type == 0xFF ||
178 type_code_in_range(test_type, min_code, max_code, type, code))
182 static bool icmp6_type_code_match(u8 test_type, u8 min_code, u8 max_code,
183 u8 type, u8 code, bool invert)
185 return type_code_in_range(test_type, min_code, max_code, type, code) ^ invert;
189 icmp_match(const struct sk_buff *skb, struct xt_action_param *par)
191 const struct icmphdr *ic;
192 struct icmphdr _icmph;
193 const struct ipt_icmp *icmpinfo = par->matchinfo;
195 /* Must not be a fragment. */
196 if (par->fragoff != 0)
199 ic = skb_header_pointer(skb, par->thoff, sizeof(_icmph), &_icmph);
201 /* We've been asked to examine this packet, and we
202 * can't. Hence, no choice but to drop.
208 return icmp_type_code_match(icmpinfo->type,
212 !!(icmpinfo->invflags & IPT_ICMP_INV));
216 icmp6_match(const struct sk_buff *skb, struct xt_action_param *par)
218 const struct icmp6hdr *ic;
219 struct icmp6hdr _icmph;
220 const struct ip6t_icmp *icmpinfo = par->matchinfo;
222 /* Must not be a fragment. */
223 if (par->fragoff != 0)
226 ic = skb_header_pointer(skb, par->thoff, sizeof(_icmph), &_icmph);
228 /* We've been asked to examine this packet, and we
229 * can't. Hence, no choice but to drop.
235 return icmp6_type_code_match(icmpinfo->type,
238 ic->icmp6_type, ic->icmp6_code,
239 !!(icmpinfo->invflags & IP6T_ICMP_INV));
242 static int icmp_checkentry(const struct xt_mtchk_param *par)
244 const struct ipt_icmp *icmpinfo = par->matchinfo;
246 return (icmpinfo->invflags & ~IPT_ICMP_INV) ? -EINVAL : 0;
249 static int icmp6_checkentry(const struct xt_mtchk_param *par)
251 const struct ip6t_icmp *icmpinfo = par->matchinfo;
253 return (icmpinfo->invflags & ~IP6T_ICMP_INV) ? -EINVAL : 0;
256 static struct xt_match tcpudp_mt_reg[] __read_mostly = {
259 .family = NFPROTO_IPV4,
260 .checkentry = tcp_mt_check,
262 .matchsize = sizeof(struct xt_tcp),
263 .proto = IPPROTO_TCP,
268 .family = NFPROTO_IPV6,
269 .checkentry = tcp_mt_check,
271 .matchsize = sizeof(struct xt_tcp),
272 .proto = IPPROTO_TCP,
277 .family = NFPROTO_IPV4,
278 .checkentry = udp_mt_check,
280 .matchsize = sizeof(struct xt_udp),
281 .proto = IPPROTO_UDP,
286 .family = NFPROTO_IPV6,
287 .checkentry = udp_mt_check,
289 .matchsize = sizeof(struct xt_udp),
290 .proto = IPPROTO_UDP,
295 .family = NFPROTO_IPV4,
296 .checkentry = udp_mt_check,
298 .matchsize = sizeof(struct xt_udp),
299 .proto = IPPROTO_UDPLITE,
304 .family = NFPROTO_IPV6,
305 .checkentry = udp_mt_check,
307 .matchsize = sizeof(struct xt_udp),
308 .proto = IPPROTO_UDPLITE,
314 .matchsize = sizeof(struct ipt_icmp),
315 .checkentry = icmp_checkentry,
316 .proto = IPPROTO_ICMP,
317 .family = NFPROTO_IPV4,
322 .match = icmp6_match,
323 .matchsize = sizeof(struct ip6t_icmp),
324 .checkentry = icmp6_checkentry,
325 .proto = IPPROTO_ICMPV6,
326 .family = NFPROTO_IPV6,
331 static int __init tcpudp_mt_init(void)
333 return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
336 static void __exit tcpudp_mt_exit(void)
338 xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg));
341 module_init(tcpudp_mt_init);
342 module_exit(tcpudp_mt_exit);