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be91fd5e | 1 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
2e4e6a17 HW |
2 | #include <linux/types.h> |
3 | #include <linux/module.h> | |
4 | #include <net/ip.h> | |
37d8dc82 | 5 | #include <linux/ipv6.h> |
2e4e6a17 HW |
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 | ||
2ae15b64 | 14 | MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match"); |
2e4e6a17 HW |
15 | MODULE_LICENSE("GPL"); |
16 | MODULE_ALIAS("xt_tcp"); | |
17 | MODULE_ALIAS("xt_udp"); | |
18 | MODULE_ALIAS("ipt_udp"); | |
19 | MODULE_ALIAS("ipt_tcp"); | |
20 | MODULE_ALIAS("ip6t_udp"); | |
21 | MODULE_ALIAS("ip6t_tcp"); | |
22 | ||
2e4e6a17 | 23 | /* Returns 1 if the port is matched by the range, 0 otherwise */ |
1d93a9cb JE |
24 | static inline bool |
25 | port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert) | |
2e4e6a17 | 26 | { |
1d93a9cb | 27 | return (port >= min && port <= max) ^ invert; |
2e4e6a17 HW |
28 | } |
29 | ||
1d93a9cb | 30 | static bool |
2e4e6a17 HW |
31 | tcp_find_option(u_int8_t option, |
32 | const struct sk_buff *skb, | |
33 | unsigned int protoff, | |
34 | unsigned int optlen, | |
1d93a9cb | 35 | bool invert, |
cff533ac | 36 | bool *hotdrop) |
2e4e6a17 HW |
37 | { |
38 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ | |
3cf93c96 JE |
39 | const u_int8_t *op; |
40 | u_int8_t _opt[60 - sizeof(struct tcphdr)]; | |
2e4e6a17 HW |
41 | unsigned int i; |
42 | ||
be91fd5e | 43 | pr_debug("finding option\n"); |
2e4e6a17 HW |
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) { | |
cff533ac | 52 | *hotdrop = true; |
1d93a9cb | 53 | return false; |
2e4e6a17 HW |
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 | ||
62fc8051 | 65 | static bool tcp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
2e4e6a17 | 66 | { |
3cf93c96 JE |
67 | const struct tcphdr *th; |
68 | struct tcphdr _tcph; | |
f7108a20 | 69 | const struct xt_tcp *tcpinfo = par->matchinfo; |
2e4e6a17 | 70 | |
f7108a20 | 71 | if (par->fragoff != 0) { |
2e4e6a17 HW |
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 | */ | |
f7108a20 | 78 | if (par->fragoff == 1) { |
be91fd5e | 79 | pr_debug("Dropping evil TCP offset=1 frag.\n"); |
b4ba2611 | 80 | par->hotdrop = true; |
2e4e6a17 HW |
81 | } |
82 | /* Must not be a fragment. */ | |
1d93a9cb | 83 | return false; |
2e4e6a17 HW |
84 | } |
85 | ||
f7108a20 | 86 | th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph); |
2e4e6a17 HW |
87 | if (th == NULL) { |
88 | /* We've been asked to examine this packet, and we | |
89 | can't. Hence, no choice but to drop. */ | |
be91fd5e | 90 | pr_debug("Dropping evil TCP offset=0 tinygram.\n"); |
b4ba2611 | 91 | par->hotdrop = true; |
1d93a9cb | 92 | return false; |
2e4e6a17 HW |
93 | } |
94 | ||
95 | if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], | |
96 | ntohs(th->source), | |
97 | !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) | |
1d93a9cb | 98 | return false; |
2e4e6a17 HW |
99 | if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], |
100 | ntohs(th->dest), | |
101 | !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) | |
1d93a9cb | 102 | return false; |
c37a2dfa JP |
103 | if (!NF_INVF(tcpinfo, XT_TCP_INV_FLAGS, |
104 | (((unsigned char *)th)[13] & tcpinfo->flg_mask) == tcpinfo->flg_cmp)) | |
1d93a9cb | 105 | return false; |
2e4e6a17 HW |
106 | if (tcpinfo->option) { |
107 | if (th->doff * 4 < sizeof(_tcph)) { | |
b4ba2611 | 108 | par->hotdrop = true; |
1d93a9cb | 109 | return false; |
2e4e6a17 | 110 | } |
f7108a20 | 111 | if (!tcp_find_option(tcpinfo->option, skb, par->thoff, |
2e4e6a17 HW |
112 | th->doff*4 - sizeof(_tcph), |
113 | tcpinfo->invflags & XT_TCP_INV_OPTION, | |
b4ba2611 | 114 | &par->hotdrop)) |
1d93a9cb | 115 | return false; |
2e4e6a17 | 116 | } |
1d93a9cb | 117 | return true; |
2e4e6a17 HW |
118 | } |
119 | ||
b0f38452 | 120 | static int tcp_mt_check(const struct xt_mtchk_param *par) |
2e4e6a17 | 121 | { |
9b4fce7a | 122 | const struct xt_tcp *tcpinfo = par->matchinfo; |
2e4e6a17 | 123 | |
5d04bff0 | 124 | /* Must specify no unknown invflags */ |
bd414ee6 | 125 | return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0; |
2e4e6a17 HW |
126 | } |
127 | ||
62fc8051 | 128 | static bool udp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
2e4e6a17 | 129 | { |
3cf93c96 JE |
130 | const struct udphdr *uh; |
131 | struct udphdr _udph; | |
f7108a20 | 132 | const struct xt_udp *udpinfo = par->matchinfo; |
2e4e6a17 HW |
133 | |
134 | /* Must not be a fragment. */ | |
f7108a20 | 135 | if (par->fragoff != 0) |
1d93a9cb | 136 | return false; |
2e4e6a17 | 137 | |
f7108a20 | 138 | uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph); |
2e4e6a17 HW |
139 | if (uh == NULL) { |
140 | /* We've been asked to examine this packet, and we | |
141 | can't. Hence, no choice but to drop. */ | |
be91fd5e | 142 | pr_debug("Dropping evil UDP tinygram.\n"); |
b4ba2611 | 143 | par->hotdrop = true; |
1d93a9cb | 144 | return false; |
2e4e6a17 HW |
145 | } |
146 | ||
147 | return port_match(udpinfo->spts[0], udpinfo->spts[1], | |
148 | ntohs(uh->source), | |
149 | !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) | |
150 | && port_match(udpinfo->dpts[0], udpinfo->dpts[1], | |
151 | ntohs(uh->dest), | |
152 | !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); | |
153 | } | |
154 | ||
b0f38452 | 155 | static int udp_mt_check(const struct xt_mtchk_param *par) |
2e4e6a17 | 156 | { |
9b4fce7a | 157 | const struct xt_udp *udpinfo = par->matchinfo; |
2e4e6a17 | 158 | |
5d04bff0 | 159 | /* Must specify no unknown invflags */ |
bd414ee6 | 160 | return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0; |
2e4e6a17 HW |
161 | } |
162 | ||
d3c5ee6d | 163 | static struct xt_match tcpudp_mt_reg[] __read_mostly = { |
4470bbc7 PM |
164 | { |
165 | .name = "tcp", | |
ee999d8b | 166 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
167 | .checkentry = tcp_mt_check, |
168 | .match = tcp_mt, | |
4470bbc7 PM |
169 | .matchsize = sizeof(struct xt_tcp), |
170 | .proto = IPPROTO_TCP, | |
171 | .me = THIS_MODULE, | |
172 | }, | |
173 | { | |
174 | .name = "tcp", | |
ee999d8b | 175 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
176 | .checkentry = tcp_mt_check, |
177 | .match = tcp_mt, | |
4470bbc7 PM |
178 | .matchsize = sizeof(struct xt_tcp), |
179 | .proto = IPPROTO_TCP, | |
180 | .me = THIS_MODULE, | |
181 | }, | |
182 | { | |
183 | .name = "udp", | |
ee999d8b | 184 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
185 | .checkentry = udp_mt_check, |
186 | .match = udp_mt, | |
4470bbc7 PM |
187 | .matchsize = sizeof(struct xt_udp), |
188 | .proto = IPPROTO_UDP, | |
189 | .me = THIS_MODULE, | |
190 | }, | |
191 | { | |
192 | .name = "udp", | |
ee999d8b | 193 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
194 | .checkentry = udp_mt_check, |
195 | .match = udp_mt, | |
4470bbc7 PM |
196 | .matchsize = sizeof(struct xt_udp), |
197 | .proto = IPPROTO_UDP, | |
198 | .me = THIS_MODULE, | |
199 | }, | |
ba4e58ec GR |
200 | { |
201 | .name = "udplite", | |
ee999d8b | 202 | .family = NFPROTO_IPV4, |
d3c5ee6d JE |
203 | .checkentry = udp_mt_check, |
204 | .match = udp_mt, | |
ba4e58ec GR |
205 | .matchsize = sizeof(struct xt_udp), |
206 | .proto = IPPROTO_UDPLITE, | |
207 | .me = THIS_MODULE, | |
208 | }, | |
209 | { | |
210 | .name = "udplite", | |
ee999d8b | 211 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
212 | .checkentry = udp_mt_check, |
213 | .match = udp_mt, | |
ba4e58ec GR |
214 | .matchsize = sizeof(struct xt_udp), |
215 | .proto = IPPROTO_UDPLITE, | |
216 | .me = THIS_MODULE, | |
217 | }, | |
2e4e6a17 HW |
218 | }; |
219 | ||
d3c5ee6d | 220 | static int __init tcpudp_mt_init(void) |
2e4e6a17 | 221 | { |
d3c5ee6d | 222 | return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
2e4e6a17 HW |
223 | } |
224 | ||
d3c5ee6d | 225 | static void __exit tcpudp_mt_exit(void) |
2e4e6a17 | 226 | { |
d3c5ee6d | 227 | xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
2e4e6a17 HW |
228 | } |
229 | ||
d3c5ee6d JE |
230 | module_init(tcpudp_mt_init); |
231 | module_exit(tcpudp_mt_exit); |