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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 | ||
ba4e58ec | 13 | MODULE_DESCRIPTION("x_tables match for TCP and UDP(-Lite), supports IPv4 and IPv6"); |
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 */ | |
45 | u_int8_t _opt[60 - sizeof(struct tcphdr)], *op; | |
46 | unsigned int i; | |
47 | ||
48 | duprintf("tcp_match: finding option\n"); | |
49 | ||
50 | if (!optlen) | |
51 | return invert; | |
52 | ||
53 | /* If we don't have the whole header, drop packet. */ | |
54 | op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr), | |
55 | optlen, _opt); | |
56 | if (op == NULL) { | |
cff533ac | 57 | *hotdrop = true; |
1d93a9cb | 58 | return false; |
2e4e6a17 HW |
59 | } |
60 | ||
61 | for (i = 0; i < optlen; ) { | |
62 | if (op[i] == option) return !invert; | |
63 | if (op[i] < 2) i++; | |
64 | else i += op[i+1]?:1; | |
65 | } | |
66 | ||
67 | return invert; | |
68 | } | |
69 | ||
1d93a9cb | 70 | static bool |
2e4e6a17 HW |
71 | tcp_match(const struct sk_buff *skb, |
72 | const struct net_device *in, | |
73 | const struct net_device *out, | |
c4986734 | 74 | const struct xt_match *match, |
2e4e6a17 HW |
75 | const void *matchinfo, |
76 | int offset, | |
77 | unsigned int protoff, | |
cff533ac | 78 | bool *hotdrop) |
2e4e6a17 HW |
79 | { |
80 | struct tcphdr _tcph, *th; | |
81 | const struct xt_tcp *tcpinfo = matchinfo; | |
82 | ||
83 | if (offset) { | |
84 | /* To quote Alan: | |
85 | ||
86 | Don't allow a fragment of TCP 8 bytes in. Nobody normal | |
87 | causes this. Its a cracker trying to break in by doing a | |
88 | flag overwrite to pass the direction checks. | |
89 | */ | |
90 | if (offset == 1) { | |
91 | duprintf("Dropping evil TCP offset=1 frag.\n"); | |
cff533ac | 92 | *hotdrop = true; |
2e4e6a17 HW |
93 | } |
94 | /* Must not be a fragment. */ | |
1d93a9cb | 95 | return false; |
2e4e6a17 HW |
96 | } |
97 | ||
98 | #define FWINVTCP(bool,invflg) ((bool) ^ !!(tcpinfo->invflags & invflg)) | |
99 | ||
100 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); | |
101 | if (th == NULL) { | |
102 | /* We've been asked to examine this packet, and we | |
103 | can't. Hence, no choice but to drop. */ | |
104 | duprintf("Dropping evil TCP offset=0 tinygram.\n"); | |
cff533ac | 105 | *hotdrop = true; |
1d93a9cb | 106 | return false; |
2e4e6a17 HW |
107 | } |
108 | ||
109 | if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], | |
110 | ntohs(th->source), | |
111 | !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) | |
1d93a9cb | 112 | return false; |
2e4e6a17 HW |
113 | if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], |
114 | ntohs(th->dest), | |
115 | !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) | |
1d93a9cb | 116 | return false; |
2e4e6a17 HW |
117 | if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask) |
118 | == tcpinfo->flg_cmp, | |
119 | XT_TCP_INV_FLAGS)) | |
1d93a9cb | 120 | return false; |
2e4e6a17 HW |
121 | if (tcpinfo->option) { |
122 | if (th->doff * 4 < sizeof(_tcph)) { | |
cff533ac | 123 | *hotdrop = true; |
1d93a9cb | 124 | return false; |
2e4e6a17 HW |
125 | } |
126 | if (!tcp_find_option(tcpinfo->option, skb, protoff, | |
127 | th->doff*4 - sizeof(_tcph), | |
128 | tcpinfo->invflags & XT_TCP_INV_OPTION, | |
129 | hotdrop)) | |
1d93a9cb | 130 | return false; |
2e4e6a17 | 131 | } |
1d93a9cb | 132 | return true; |
2e4e6a17 HW |
133 | } |
134 | ||
135 | /* Called when user tries to insert an entry of this type. */ | |
ccb79bdc | 136 | static bool |
2e4e6a17 HW |
137 | tcp_checkentry(const char *tablename, |
138 | const void *info, | |
c4986734 | 139 | const struct xt_match *match, |
2e4e6a17 | 140 | void *matchinfo, |
2e4e6a17 HW |
141 | unsigned int hook_mask) |
142 | { | |
2e4e6a17 HW |
143 | const struct xt_tcp *tcpinfo = matchinfo; |
144 | ||
5d04bff0 PM |
145 | /* Must specify no unknown invflags */ |
146 | return !(tcpinfo->invflags & ~XT_TCP_INV_MASK); | |
2e4e6a17 HW |
147 | } |
148 | ||
1d93a9cb | 149 | static bool |
2e4e6a17 HW |
150 | udp_match(const struct sk_buff *skb, |
151 | const struct net_device *in, | |
152 | const struct net_device *out, | |
c4986734 | 153 | const struct xt_match *match, |
2e4e6a17 HW |
154 | const void *matchinfo, |
155 | int offset, | |
156 | unsigned int protoff, | |
cff533ac | 157 | bool *hotdrop) |
2e4e6a17 HW |
158 | { |
159 | struct udphdr _udph, *uh; | |
160 | const struct xt_udp *udpinfo = matchinfo; | |
161 | ||
162 | /* Must not be a fragment. */ | |
163 | if (offset) | |
1d93a9cb | 164 | return false; |
2e4e6a17 HW |
165 | |
166 | uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph); | |
167 | if (uh == NULL) { | |
168 | /* We've been asked to examine this packet, and we | |
169 | can't. Hence, no choice but to drop. */ | |
170 | duprintf("Dropping evil UDP tinygram.\n"); | |
cff533ac | 171 | *hotdrop = true; |
1d93a9cb | 172 | return false; |
2e4e6a17 HW |
173 | } |
174 | ||
175 | return port_match(udpinfo->spts[0], udpinfo->spts[1], | |
176 | ntohs(uh->source), | |
177 | !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) | |
178 | && port_match(udpinfo->dpts[0], udpinfo->dpts[1], | |
179 | ntohs(uh->dest), | |
180 | !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); | |
181 | } | |
182 | ||
183 | /* Called when user tries to insert an entry of this type. */ | |
ccb79bdc | 184 | static bool |
2e4e6a17 HW |
185 | udp_checkentry(const char *tablename, |
186 | const void *info, | |
c4986734 | 187 | const struct xt_match *match, |
2e4e6a17 | 188 | void *matchinfo, |
2e4e6a17 HW |
189 | unsigned int hook_mask) |
190 | { | |
5d04bff0 | 191 | const struct xt_tcp *udpinfo = matchinfo; |
2e4e6a17 | 192 | |
5d04bff0 PM |
193 | /* Must specify no unknown invflags */ |
194 | return !(udpinfo->invflags & ~XT_UDP_INV_MASK); | |
2e4e6a17 HW |
195 | } |
196 | ||
4470bbc7 PM |
197 | static struct xt_match xt_tcpudp_match[] = { |
198 | { | |
199 | .name = "tcp", | |
200 | .family = AF_INET, | |
201 | .checkentry = tcp_checkentry, | |
202 | .match = tcp_match, | |
203 | .matchsize = sizeof(struct xt_tcp), | |
204 | .proto = IPPROTO_TCP, | |
205 | .me = THIS_MODULE, | |
206 | }, | |
207 | { | |
208 | .name = "tcp", | |
209 | .family = AF_INET6, | |
210 | .checkentry = tcp_checkentry, | |
211 | .match = tcp_match, | |
212 | .matchsize = sizeof(struct xt_tcp), | |
213 | .proto = IPPROTO_TCP, | |
214 | .me = THIS_MODULE, | |
215 | }, | |
216 | { | |
217 | .name = "udp", | |
218 | .family = AF_INET, | |
219 | .checkentry = udp_checkentry, | |
220 | .match = udp_match, | |
221 | .matchsize = sizeof(struct xt_udp), | |
222 | .proto = IPPROTO_UDP, | |
223 | .me = THIS_MODULE, | |
224 | }, | |
225 | { | |
226 | .name = "udp", | |
227 | .family = AF_INET6, | |
228 | .checkentry = udp_checkentry, | |
229 | .match = udp_match, | |
230 | .matchsize = sizeof(struct xt_udp), | |
231 | .proto = IPPROTO_UDP, | |
232 | .me = THIS_MODULE, | |
233 | }, | |
ba4e58ec GR |
234 | { |
235 | .name = "udplite", | |
236 | .family = AF_INET, | |
237 | .checkentry = udp_checkentry, | |
238 | .match = udp_match, | |
239 | .matchsize = sizeof(struct xt_udp), | |
240 | .proto = IPPROTO_UDPLITE, | |
241 | .me = THIS_MODULE, | |
242 | }, | |
243 | { | |
244 | .name = "udplite", | |
245 | .family = AF_INET6, | |
246 | .checkentry = udp_checkentry, | |
247 | .match = udp_match, | |
248 | .matchsize = sizeof(struct xt_udp), | |
249 | .proto = IPPROTO_UDPLITE, | |
250 | .me = THIS_MODULE, | |
251 | }, | |
2e4e6a17 HW |
252 | }; |
253 | ||
65b4b4e8 | 254 | static int __init xt_tcpudp_init(void) |
2e4e6a17 | 255 | { |
4470bbc7 PM |
256 | return xt_register_matches(xt_tcpudp_match, |
257 | ARRAY_SIZE(xt_tcpudp_match)); | |
2e4e6a17 HW |
258 | } |
259 | ||
65b4b4e8 | 260 | static void __exit xt_tcpudp_fini(void) |
2e4e6a17 | 261 | { |
4470bbc7 | 262 | xt_unregister_matches(xt_tcpudp_match, ARRAY_SIZE(xt_tcpudp_match)); |
2e4e6a17 HW |
263 | } |
264 | ||
65b4b4e8 AM |
265 | module_init(xt_tcpudp_init); |
266 | module_exit(xt_tcpudp_fini); |