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09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
be91fd5e | 2 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
2e4e6a17 HW |
3 | #include <linux/types.h> |
4 | #include <linux/module.h> | |
5 | #include <net/ip.h> | |
37d8dc82 | 6 | #include <linux/ipv6.h> |
2e4e6a17 HW |
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 | ||
2ae15b64 | 15 | MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match"); |
2e4e6a17 HW |
16 | MODULE_LICENSE("GPL"); |
17 | MODULE_ALIAS("xt_tcp"); | |
18 | MODULE_ALIAS("xt_udp"); | |
19 | MODULE_ALIAS("ipt_udp"); | |
20 | MODULE_ALIAS("ipt_tcp"); | |
21 | MODULE_ALIAS("ip6t_udp"); | |
22 | MODULE_ALIAS("ip6t_tcp"); | |
23 | ||
2e4e6a17 | 24 | /* Returns 1 if the port is matched by the range, 0 otherwise */ |
1d93a9cb JE |
25 | static inline bool |
26 | port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert) | |
2e4e6a17 | 27 | { |
1d93a9cb | 28 | return (port >= min && port <= max) ^ invert; |
2e4e6a17 HW |
29 | } |
30 | ||
1d93a9cb | 31 | static bool |
2e4e6a17 HW |
32 | tcp_find_option(u_int8_t option, |
33 | const struct sk_buff *skb, | |
34 | unsigned int protoff, | |
35 | unsigned int optlen, | |
1d93a9cb | 36 | bool invert, |
cff533ac | 37 | bool *hotdrop) |
2e4e6a17 HW |
38 | { |
39 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ | |
3cf93c96 JE |
40 | const u_int8_t *op; |
41 | u_int8_t _opt[60 - sizeof(struct tcphdr)]; | |
2e4e6a17 HW |
42 | unsigned int i; |
43 | ||
be91fd5e | 44 | pr_debug("finding option\n"); |
2e4e6a17 HW |
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) { | |
cff533ac | 53 | *hotdrop = true; |
1d93a9cb | 54 | return false; |
2e4e6a17 HW |
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 | ||
62fc8051 | 66 | static bool tcp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
2e4e6a17 | 67 | { |
3cf93c96 JE |
68 | const struct tcphdr *th; |
69 | struct tcphdr _tcph; | |
f7108a20 | 70 | const struct xt_tcp *tcpinfo = par->matchinfo; |
2e4e6a17 | 71 | |
f7108a20 | 72 | if (par->fragoff != 0) { |
2e4e6a17 HW |
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 | */ | |
f7108a20 | 79 | if (par->fragoff == 1) { |
be91fd5e | 80 | pr_debug("Dropping evil TCP offset=1 frag.\n"); |
b4ba2611 | 81 | par->hotdrop = true; |
2e4e6a17 HW |
82 | } |
83 | /* Must not be a fragment. */ | |
1d93a9cb | 84 | return false; |
2e4e6a17 HW |
85 | } |
86 | ||
f7108a20 | 87 | th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph); |
2e4e6a17 HW |
88 | if (th == NULL) { |
89 | /* We've been asked to examine this packet, and we | |
90 | can't. Hence, no choice but to drop. */ | |
be91fd5e | 91 | pr_debug("Dropping evil TCP offset=0 tinygram.\n"); |
b4ba2611 | 92 | par->hotdrop = true; |
1d93a9cb | 93 | return false; |
2e4e6a17 HW |
94 | } |
95 | ||
96 | if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], | |
97 | ntohs(th->source), | |
98 | !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) | |
1d93a9cb | 99 | return false; |
2e4e6a17 HW |
100 | if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], |
101 | ntohs(th->dest), | |
102 | !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) | |
1d93a9cb | 103 | return false; |
c37a2dfa JP |
104 | if (!NF_INVF(tcpinfo, XT_TCP_INV_FLAGS, |
105 | (((unsigned char *)th)[13] & tcpinfo->flg_mask) == tcpinfo->flg_cmp)) | |
1d93a9cb | 106 | return false; |
2e4e6a17 HW |
107 | if (tcpinfo->option) { |
108 | if (th->doff * 4 < sizeof(_tcph)) { | |
b4ba2611 | 109 | par->hotdrop = true; |
1d93a9cb | 110 | return false; |
2e4e6a17 | 111 | } |
f7108a20 | 112 | if (!tcp_find_option(tcpinfo->option, skb, par->thoff, |
2e4e6a17 HW |
113 | th->doff*4 - sizeof(_tcph), |
114 | tcpinfo->invflags & XT_TCP_INV_OPTION, | |
b4ba2611 | 115 | &par->hotdrop)) |
1d93a9cb | 116 | return false; |
2e4e6a17 | 117 | } |
1d93a9cb | 118 | return true; |
2e4e6a17 HW |
119 | } |
120 | ||
b0f38452 | 121 | static int tcp_mt_check(const struct xt_mtchk_param *par) |
2e4e6a17 | 122 | { |
9b4fce7a | 123 | const struct xt_tcp *tcpinfo = par->matchinfo; |
2e4e6a17 | 124 | |
5d04bff0 | 125 | /* Must specify no unknown invflags */ |
bd414ee6 | 126 | return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0; |
2e4e6a17 HW |
127 | } |
128 | ||
62fc8051 | 129 | static bool udp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
2e4e6a17 | 130 | { |
3cf93c96 JE |
131 | const struct udphdr *uh; |
132 | struct udphdr _udph; | |
f7108a20 | 133 | const struct xt_udp *udpinfo = par->matchinfo; |
2e4e6a17 HW |
134 | |
135 | /* Must not be a fragment. */ | |
f7108a20 | 136 | if (par->fragoff != 0) |
1d93a9cb | 137 | return false; |
2e4e6a17 | 138 | |
f7108a20 | 139 | uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph); |
2e4e6a17 HW |
140 | if (uh == NULL) { |
141 | /* We've been asked to examine this packet, and we | |
142 | can't. Hence, no choice but to drop. */ | |
be91fd5e | 143 | pr_debug("Dropping evil UDP tinygram.\n"); |
b4ba2611 | 144 | par->hotdrop = true; |
1d93a9cb | 145 | return false; |
2e4e6a17 HW |
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 | ||
b0f38452 | 156 | static int udp_mt_check(const struct xt_mtchk_param *par) |
2e4e6a17 | 157 | { |
9b4fce7a | 158 | const struct xt_udp *udpinfo = par->matchinfo; |
2e4e6a17 | 159 | |
5d04bff0 | 160 | /* Must specify no unknown invflags */ |
bd414ee6 | 161 | return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0; |
2e4e6a17 HW |
162 | } |
163 | ||
d3c5ee6d | 164 | static struct xt_match tcpudp_mt_reg[] __read_mostly = { |
4470bbc7 PM |
165 | { |
166 | .name = "tcp", | |
ee999d8b | 167 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
168 | .checkentry = tcp_mt_check, |
169 | .match = tcp_mt, | |
4470bbc7 PM |
170 | .matchsize = sizeof(struct xt_tcp), |
171 | .proto = IPPROTO_TCP, | |
172 | .me = THIS_MODULE, | |
173 | }, | |
174 | { | |
175 | .name = "tcp", | |
ee999d8b | 176 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
177 | .checkentry = tcp_mt_check, |
178 | .match = tcp_mt, | |
4470bbc7 PM |
179 | .matchsize = sizeof(struct xt_tcp), |
180 | .proto = IPPROTO_TCP, | |
181 | .me = THIS_MODULE, | |
182 | }, | |
183 | { | |
184 | .name = "udp", | |
ee999d8b | 185 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
186 | .checkentry = udp_mt_check, |
187 | .match = udp_mt, | |
4470bbc7 PM |
188 | .matchsize = sizeof(struct xt_udp), |
189 | .proto = IPPROTO_UDP, | |
190 | .me = THIS_MODULE, | |
191 | }, | |
192 | { | |
193 | .name = "udp", | |
ee999d8b | 194 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
195 | .checkentry = udp_mt_check, |
196 | .match = udp_mt, | |
4470bbc7 PM |
197 | .matchsize = sizeof(struct xt_udp), |
198 | .proto = IPPROTO_UDP, | |
199 | .me = THIS_MODULE, | |
200 | }, | |
ba4e58ec GR |
201 | { |
202 | .name = "udplite", | |
ee999d8b | 203 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
204 | .checkentry = udp_mt_check, |
205 | .match = udp_mt, | |
ba4e58ec GR |
206 | .matchsize = sizeof(struct xt_udp), |
207 | .proto = IPPROTO_UDPLITE, | |
208 | .me = THIS_MODULE, | |
209 | }, | |
210 | { | |
211 | .name = "udplite", | |
ee999d8b | 212 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
213 | .checkentry = udp_mt_check, |
214 | .match = udp_mt, | |
ba4e58ec GR |
215 | .matchsize = sizeof(struct xt_udp), |
216 | .proto = IPPROTO_UDPLITE, | |
217 | .me = THIS_MODULE, | |
218 | }, | |
2e4e6a17 HW |
219 | }; |
220 | ||
d3c5ee6d | 221 | static int __init tcpudp_mt_init(void) |
2e4e6a17 | 222 | { |
d3c5ee6d | 223 | return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
2e4e6a17 HW |
224 | } |
225 | ||
d3c5ee6d | 226 | static void __exit tcpudp_mt_exit(void) |
2e4e6a17 | 227 | { |
d3c5ee6d | 228 | xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
2e4e6a17 HW |
229 | } |
230 | ||
d3c5ee6d JE |
231 | module_init(tcpudp_mt_init); |
232 | module_exit(tcpudp_mt_exit); |