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2e4e6a17 HW |
1 | #include <linux/types.h> |
2 | #include <linux/module.h> | |
3 | #include <net/ip.h> | |
37d8dc82 | 4 | #include <linux/ipv6.h> |
2e4e6a17 HW |
5 | #include <net/ipv6.h> |
6 | #include <net/tcp.h> | |
7 | #include <net/udp.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> | |
12 | ||
2ae15b64 | 13 | MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match"); |
2e4e6a17 HW |
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"); | |
21 | ||
22 | #ifdef DEBUG_IP_FIREWALL_USER | |
23 | #define duprintf(format, args...) printk(format , ## args) | |
24 | #else | |
25 | #define duprintf(format, args...) | |
26 | #endif | |
27 | ||
28 | ||
29 | /* Returns 1 if the port is matched by the range, 0 otherwise */ | |
1d93a9cb JE |
30 | static inline bool |
31 | port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert) | |
2e4e6a17 | 32 | { |
1d93a9cb | 33 | return (port >= min && port <= max) ^ invert; |
2e4e6a17 HW |
34 | } |
35 | ||
1d93a9cb | 36 | static bool |
2e4e6a17 HW |
37 | tcp_find_option(u_int8_t option, |
38 | const struct sk_buff *skb, | |
39 | unsigned int protoff, | |
40 | unsigned int optlen, | |
1d93a9cb | 41 | bool invert, |
cff533ac | 42 | bool *hotdrop) |
2e4e6a17 HW |
43 | { |
44 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ | |
3cf93c96 JE |
45 | const u_int8_t *op; |
46 | u_int8_t _opt[60 - sizeof(struct tcphdr)]; | |
2e4e6a17 HW |
47 | unsigned int i; |
48 | ||
49 | duprintf("tcp_match: finding option\n"); | |
50 | ||
51 | if (!optlen) | |
52 | return invert; | |
53 | ||
54 | /* If we don't have the whole header, drop packet. */ | |
55 | op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr), | |
56 | optlen, _opt); | |
57 | if (op == NULL) { | |
cff533ac | 58 | *hotdrop = true; |
1d93a9cb | 59 | return false; |
2e4e6a17 HW |
60 | } |
61 | ||
62 | for (i = 0; i < optlen; ) { | |
63 | if (op[i] == option) return !invert; | |
64 | if (op[i] < 2) i++; | |
65 | else i += op[i+1]?:1; | |
66 | } | |
67 | ||
68 | return invert; | |
69 | } | |
70 | ||
f7108a20 | 71 | static bool tcp_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
2e4e6a17 | 72 | { |
3cf93c96 JE |
73 | const struct tcphdr *th; |
74 | struct tcphdr _tcph; | |
f7108a20 | 75 | const struct xt_tcp *tcpinfo = par->matchinfo; |
2e4e6a17 | 76 | |
f7108a20 | 77 | if (par->fragoff != 0) { |
2e4e6a17 HW |
78 | /* To quote Alan: |
79 | ||
80 | Don't allow a fragment of TCP 8 bytes in. Nobody normal | |
81 | causes this. Its a cracker trying to break in by doing a | |
82 | flag overwrite to pass the direction checks. | |
83 | */ | |
f7108a20 | 84 | if (par->fragoff == 1) { |
2e4e6a17 | 85 | duprintf("Dropping evil TCP offset=1 frag.\n"); |
f7108a20 | 86 | *par->hotdrop = true; |
2e4e6a17 HW |
87 | } |
88 | /* Must not be a fragment. */ | |
1d93a9cb | 89 | return false; |
2e4e6a17 HW |
90 | } |
91 | ||
7c4e36bc | 92 | #define FWINVTCP(bool, invflg) ((bool) ^ !!(tcpinfo->invflags & (invflg))) |
2e4e6a17 | 93 | |
f7108a20 | 94 | th = skb_header_pointer(skb, par->thoff, sizeof(_tcph), &_tcph); |
2e4e6a17 HW |
95 | if (th == NULL) { |
96 | /* We've been asked to examine this packet, and we | |
97 | can't. Hence, no choice but to drop. */ | |
98 | duprintf("Dropping evil TCP offset=0 tinygram.\n"); | |
f7108a20 | 99 | *par->hotdrop = true; |
1d93a9cb | 100 | return false; |
2e4e6a17 HW |
101 | } |
102 | ||
103 | if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], | |
104 | ntohs(th->source), | |
105 | !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) | |
1d93a9cb | 106 | return false; |
2e4e6a17 HW |
107 | if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], |
108 | ntohs(th->dest), | |
109 | !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) | |
1d93a9cb | 110 | return false; |
2e4e6a17 HW |
111 | if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask) |
112 | == tcpinfo->flg_cmp, | |
113 | XT_TCP_INV_FLAGS)) | |
1d93a9cb | 114 | return false; |
2e4e6a17 HW |
115 | if (tcpinfo->option) { |
116 | if (th->doff * 4 < sizeof(_tcph)) { | |
f7108a20 | 117 | *par->hotdrop = true; |
1d93a9cb | 118 | return false; |
2e4e6a17 | 119 | } |
f7108a20 | 120 | if (!tcp_find_option(tcpinfo->option, skb, par->thoff, |
2e4e6a17 HW |
121 | th->doff*4 - sizeof(_tcph), |
122 | tcpinfo->invflags & XT_TCP_INV_OPTION, | |
f7108a20 | 123 | par->hotdrop)) |
1d93a9cb | 124 | return false; |
2e4e6a17 | 125 | } |
1d93a9cb | 126 | return true; |
2e4e6a17 HW |
127 | } |
128 | ||
9b4fce7a | 129 | static bool tcp_mt_check(const struct xt_mtchk_param *par) |
2e4e6a17 | 130 | { |
9b4fce7a | 131 | const struct xt_tcp *tcpinfo = par->matchinfo; |
2e4e6a17 | 132 | |
5d04bff0 PM |
133 | /* Must specify no unknown invflags */ |
134 | return !(tcpinfo->invflags & ~XT_TCP_INV_MASK); | |
2e4e6a17 HW |
135 | } |
136 | ||
f7108a20 | 137 | static bool udp_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
2e4e6a17 | 138 | { |
3cf93c96 JE |
139 | const struct udphdr *uh; |
140 | struct udphdr _udph; | |
f7108a20 | 141 | const struct xt_udp *udpinfo = par->matchinfo; |
2e4e6a17 HW |
142 | |
143 | /* Must not be a fragment. */ | |
f7108a20 | 144 | if (par->fragoff != 0) |
1d93a9cb | 145 | return false; |
2e4e6a17 | 146 | |
f7108a20 | 147 | uh = skb_header_pointer(skb, par->thoff, sizeof(_udph), &_udph); |
2e4e6a17 HW |
148 | if (uh == NULL) { |
149 | /* We've been asked to examine this packet, and we | |
150 | can't. Hence, no choice but to drop. */ | |
151 | duprintf("Dropping evil UDP tinygram.\n"); | |
f7108a20 | 152 | *par->hotdrop = true; |
1d93a9cb | 153 | return false; |
2e4e6a17 HW |
154 | } |
155 | ||
156 | return port_match(udpinfo->spts[0], udpinfo->spts[1], | |
157 | ntohs(uh->source), | |
158 | !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) | |
159 | && port_match(udpinfo->dpts[0], udpinfo->dpts[1], | |
160 | ntohs(uh->dest), | |
161 | !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); | |
162 | } | |
163 | ||
9b4fce7a | 164 | static bool udp_mt_check(const struct xt_mtchk_param *par) |
2e4e6a17 | 165 | { |
9b4fce7a | 166 | const struct xt_udp *udpinfo = par->matchinfo; |
2e4e6a17 | 167 | |
5d04bff0 PM |
168 | /* Must specify no unknown invflags */ |
169 | return !(udpinfo->invflags & ~XT_UDP_INV_MASK); | |
2e4e6a17 HW |
170 | } |
171 | ||
d3c5ee6d | 172 | static struct xt_match tcpudp_mt_reg[] __read_mostly = { |
4470bbc7 PM |
173 | { |
174 | .name = "tcp", | |
ee999d8b | 175 | .family = NFPROTO_IPV4, |
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 = "tcp", | |
ee999d8b | 184 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
185 | .checkentry = tcp_mt_check, |
186 | .match = tcp_mt, | |
4470bbc7 PM |
187 | .matchsize = sizeof(struct xt_tcp), |
188 | .proto = IPPROTO_TCP, | |
189 | .me = THIS_MODULE, | |
190 | }, | |
191 | { | |
192 | .name = "udp", | |
ee999d8b | 193 | .family = NFPROTO_IPV4, |
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 | }, | |
200 | { | |
201 | .name = "udp", | |
ee999d8b | 202 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
203 | .checkentry = udp_mt_check, |
204 | .match = udp_mt, | |
4470bbc7 PM |
205 | .matchsize = sizeof(struct xt_udp), |
206 | .proto = IPPROTO_UDP, | |
207 | .me = THIS_MODULE, | |
208 | }, | |
ba4e58ec GR |
209 | { |
210 | .name = "udplite", | |
ee999d8b | 211 | .family = NFPROTO_IPV4, |
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 | }, | |
218 | { | |
219 | .name = "udplite", | |
ee999d8b | 220 | .family = NFPROTO_IPV6, |
d3c5ee6d JE |
221 | .checkentry = udp_mt_check, |
222 | .match = udp_mt, | |
ba4e58ec GR |
223 | .matchsize = sizeof(struct xt_udp), |
224 | .proto = IPPROTO_UDPLITE, | |
225 | .me = THIS_MODULE, | |
226 | }, | |
2e4e6a17 HW |
227 | }; |
228 | ||
d3c5ee6d | 229 | static int __init tcpudp_mt_init(void) |
2e4e6a17 | 230 | { |
d3c5ee6d | 231 | return xt_register_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
2e4e6a17 HW |
232 | } |
233 | ||
d3c5ee6d | 234 | static void __exit tcpudp_mt_exit(void) |
2e4e6a17 | 235 | { |
d3c5ee6d | 236 | xt_unregister_matches(tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
2e4e6a17 HW |
237 | } |
238 | ||
d3c5ee6d JE |
239 | module_init(tcpudp_mt_init); |
240 | module_exit(tcpudp_mt_exit); |