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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 | ||
13 | MODULE_DESCRIPTION("x_tables match for TCP and UDP, supports IPv4 and IPv6"); | |
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 */ | |
30 | static inline int | |
31 | port_match(u_int16_t min, u_int16_t max, u_int16_t port, int invert) | |
32 | { | |
33 | int ret; | |
34 | ||
35 | ret = (port >= min && port <= max) ^ invert; | |
36 | return ret; | |
37 | } | |
38 | ||
39 | static int | |
40 | tcp_find_option(u_int8_t option, | |
41 | const struct sk_buff *skb, | |
42 | unsigned int protoff, | |
43 | unsigned int optlen, | |
44 | int invert, | |
45 | int *hotdrop) | |
46 | { | |
47 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ | |
48 | u_int8_t _opt[60 - sizeof(struct tcphdr)], *op; | |
49 | unsigned int i; | |
50 | ||
51 | duprintf("tcp_match: finding option\n"); | |
52 | ||
53 | if (!optlen) | |
54 | return invert; | |
55 | ||
56 | /* If we don't have the whole header, drop packet. */ | |
57 | op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr), | |
58 | optlen, _opt); | |
59 | if (op == NULL) { | |
60 | *hotdrop = 1; | |
61 | return 0; | |
62 | } | |
63 | ||
64 | for (i = 0; i < optlen; ) { | |
65 | if (op[i] == option) return !invert; | |
66 | if (op[i] < 2) i++; | |
67 | else i += op[i+1]?:1; | |
68 | } | |
69 | ||
70 | return invert; | |
71 | } | |
72 | ||
73 | static int | |
74 | tcp_match(const struct sk_buff *skb, | |
75 | const struct net_device *in, | |
76 | const struct net_device *out, | |
c4986734 | 77 | const struct xt_match *match, |
2e4e6a17 HW |
78 | const void *matchinfo, |
79 | int offset, | |
80 | unsigned int protoff, | |
81 | int *hotdrop) | |
82 | { | |
83 | struct tcphdr _tcph, *th; | |
84 | const struct xt_tcp *tcpinfo = matchinfo; | |
85 | ||
86 | if (offset) { | |
87 | /* To quote Alan: | |
88 | ||
89 | Don't allow a fragment of TCP 8 bytes in. Nobody normal | |
90 | causes this. Its a cracker trying to break in by doing a | |
91 | flag overwrite to pass the direction checks. | |
92 | */ | |
93 | if (offset == 1) { | |
94 | duprintf("Dropping evil TCP offset=1 frag.\n"); | |
95 | *hotdrop = 1; | |
96 | } | |
97 | /* Must not be a fragment. */ | |
98 | return 0; | |
99 | } | |
100 | ||
101 | #define FWINVTCP(bool,invflg) ((bool) ^ !!(tcpinfo->invflags & invflg)) | |
102 | ||
103 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); | |
104 | if (th == NULL) { | |
105 | /* We've been asked to examine this packet, and we | |
106 | can't. Hence, no choice but to drop. */ | |
107 | duprintf("Dropping evil TCP offset=0 tinygram.\n"); | |
108 | *hotdrop = 1; | |
109 | return 0; | |
110 | } | |
111 | ||
112 | if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], | |
113 | ntohs(th->source), | |
114 | !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) | |
115 | return 0; | |
116 | if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], | |
117 | ntohs(th->dest), | |
118 | !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) | |
119 | return 0; | |
120 | if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask) | |
121 | == tcpinfo->flg_cmp, | |
122 | XT_TCP_INV_FLAGS)) | |
123 | return 0; | |
124 | if (tcpinfo->option) { | |
125 | if (th->doff * 4 < sizeof(_tcph)) { | |
126 | *hotdrop = 1; | |
127 | return 0; | |
128 | } | |
129 | if (!tcp_find_option(tcpinfo->option, skb, protoff, | |
130 | th->doff*4 - sizeof(_tcph), | |
131 | tcpinfo->invflags & XT_TCP_INV_OPTION, | |
132 | hotdrop)) | |
133 | return 0; | |
134 | } | |
135 | return 1; | |
136 | } | |
137 | ||
138 | /* Called when user tries to insert an entry of this type. */ | |
139 | static int | |
140 | tcp_checkentry(const char *tablename, | |
141 | const void *info, | |
c4986734 | 142 | const struct xt_match *match, |
2e4e6a17 | 143 | void *matchinfo, |
2e4e6a17 HW |
144 | unsigned int hook_mask) |
145 | { | |
2e4e6a17 HW |
146 | const struct xt_tcp *tcpinfo = matchinfo; |
147 | ||
5d04bff0 PM |
148 | /* Must specify no unknown invflags */ |
149 | return !(tcpinfo->invflags & ~XT_TCP_INV_MASK); | |
2e4e6a17 HW |
150 | } |
151 | ||
2e4e6a17 HW |
152 | static int |
153 | udp_match(const struct sk_buff *skb, | |
154 | const struct net_device *in, | |
155 | const struct net_device *out, | |
c4986734 | 156 | const struct xt_match *match, |
2e4e6a17 HW |
157 | const void *matchinfo, |
158 | int offset, | |
159 | unsigned int protoff, | |
160 | int *hotdrop) | |
161 | { | |
162 | struct udphdr _udph, *uh; | |
163 | const struct xt_udp *udpinfo = matchinfo; | |
164 | ||
165 | /* Must not be a fragment. */ | |
166 | if (offset) | |
167 | return 0; | |
168 | ||
169 | uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph); | |
170 | if (uh == NULL) { | |
171 | /* We've been asked to examine this packet, and we | |
172 | can't. Hence, no choice but to drop. */ | |
173 | duprintf("Dropping evil UDP tinygram.\n"); | |
174 | *hotdrop = 1; | |
175 | return 0; | |
176 | } | |
177 | ||
178 | return port_match(udpinfo->spts[0], udpinfo->spts[1], | |
179 | ntohs(uh->source), | |
180 | !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) | |
181 | && port_match(udpinfo->dpts[0], udpinfo->dpts[1], | |
182 | ntohs(uh->dest), | |
183 | !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); | |
184 | } | |
185 | ||
186 | /* Called when user tries to insert an entry of this type. */ | |
187 | static int | |
188 | udp_checkentry(const char *tablename, | |
189 | const void *info, | |
c4986734 | 190 | const struct xt_match *match, |
2e4e6a17 | 191 | void *matchinfo, |
2e4e6a17 HW |
192 | unsigned int hook_mask) |
193 | { | |
5d04bff0 | 194 | const struct xt_tcp *udpinfo = matchinfo; |
2e4e6a17 | 195 | |
5d04bff0 PM |
196 | /* Must specify no unknown invflags */ |
197 | return !(udpinfo->invflags & ~XT_UDP_INV_MASK); | |
2e4e6a17 HW |
198 | } |
199 | ||
4470bbc7 PM |
200 | static struct xt_match xt_tcpudp_match[] = { |
201 | { | |
202 | .name = "tcp", | |
203 | .family = AF_INET, | |
204 | .checkentry = tcp_checkentry, | |
205 | .match = tcp_match, | |
206 | .matchsize = sizeof(struct xt_tcp), | |
207 | .proto = IPPROTO_TCP, | |
208 | .me = THIS_MODULE, | |
209 | }, | |
210 | { | |
211 | .name = "tcp", | |
212 | .family = AF_INET6, | |
213 | .checkentry = tcp_checkentry, | |
214 | .match = tcp_match, | |
215 | .matchsize = sizeof(struct xt_tcp), | |
216 | .proto = IPPROTO_TCP, | |
217 | .me = THIS_MODULE, | |
218 | }, | |
219 | { | |
220 | .name = "udp", | |
221 | .family = AF_INET, | |
222 | .checkentry = udp_checkentry, | |
223 | .match = udp_match, | |
224 | .matchsize = sizeof(struct xt_udp), | |
225 | .proto = IPPROTO_UDP, | |
226 | .me = THIS_MODULE, | |
227 | }, | |
228 | { | |
229 | .name = "udp", | |
230 | .family = AF_INET6, | |
231 | .checkentry = udp_checkentry, | |
232 | .match = udp_match, | |
233 | .matchsize = sizeof(struct xt_udp), | |
234 | .proto = IPPROTO_UDP, | |
235 | .me = THIS_MODULE, | |
236 | }, | |
2e4e6a17 HW |
237 | }; |
238 | ||
65b4b4e8 | 239 | static int __init xt_tcpudp_init(void) |
2e4e6a17 | 240 | { |
4470bbc7 PM |
241 | return xt_register_matches(xt_tcpudp_match, |
242 | ARRAY_SIZE(xt_tcpudp_match)); | |
2e4e6a17 HW |
243 | } |
244 | ||
65b4b4e8 | 245 | static void __exit xt_tcpudp_fini(void) |
2e4e6a17 | 246 | { |
4470bbc7 | 247 | xt_unregister_matches(xt_tcpudp_match, ARRAY_SIZE(xt_tcpudp_match)); |
2e4e6a17 HW |
248 | } |
249 | ||
65b4b4e8 AM |
250 | module_init(xt_tcpudp_init); |
251 | module_exit(xt_tcpudp_fini); |