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