1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
3 | #include <linux/types.h> |
4 | #include <linux/module.h> |
5 | #include <net/ip.h> |
6 | #include <linux/ipv6.h> |
7 | #include <linux/icmp.h> |
8 | #include <net/ipv6.h> |
9 | #include <net/tcp.h> |
10 | #include <net/udp.h> |
11 | #include <linux/netfilter/x_tables.h> |
12 | #include <linux/netfilter/xt_tcpudp.h> |
13 | #include <linux/netfilter_ipv4/ip_tables.h> |
14 | #include <linux/netfilter_ipv6/ip6_tables.h> |
15 | |
16 | MODULE_DESCRIPTION("Xtables: TCP, UDP and UDP-Lite match" ); |
17 | MODULE_LICENSE("GPL" ); |
18 | MODULE_ALIAS("xt_tcp" ); |
19 | MODULE_ALIAS("xt_udp" ); |
20 | MODULE_ALIAS("ipt_udp" ); |
21 | MODULE_ALIAS("ipt_tcp" ); |
22 | MODULE_ALIAS("ip6t_udp" ); |
23 | MODULE_ALIAS("ip6t_tcp" ); |
24 | MODULE_ALIAS("ipt_icmp" ); |
25 | MODULE_ALIAS("ip6t_icmp6" ); |
26 | |
27 | /* Returns 1 if the port is matched by the range, 0 otherwise */ |
28 | static inline bool |
29 | port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert) |
30 | { |
31 | return (port >= min && port <= max) ^ invert; |
32 | } |
33 | |
34 | static bool |
35 | tcp_find_option(u_int8_t option, |
36 | const struct sk_buff *skb, |
37 | unsigned int protoff, |
38 | unsigned int optlen, |
39 | bool invert, |
40 | bool *hotdrop) |
41 | { |
42 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ |
43 | const u_int8_t *op; |
44 | u_int8_t _opt[60 - sizeof(struct tcphdr)]; |
45 | unsigned int i; |
46 | |
47 | pr_debug("finding option\n" ); |
48 | |
49 | if (!optlen) |
50 | return invert; |
51 | |
52 | /* If we don't have the whole header, drop packet. */ |
53 | op = skb_header_pointer(skb, offset: protoff + sizeof(struct tcphdr), |
54 | len: optlen, buffer: _opt); |
55 | if (op == NULL) { |
56 | *hotdrop = true; |
57 | return false; |
58 | } |
59 | |
60 | for (i = 0; i < optlen; ) { |
61 | if (op[i] == option) return !invert; |
62 | if (op[i] < 2) i++; |
63 | else i += op[i+1]?:1; |
64 | } |
65 | |
66 | return invert; |
67 | } |
68 | |
69 | static bool tcp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
70 | { |
71 | const struct tcphdr *th; |
72 | struct tcphdr _tcph; |
73 | const struct xt_tcp *tcpinfo = par->matchinfo; |
74 | |
75 | if (par->fragoff != 0) { |
76 | /* To quote Alan: |
77 | |
78 | Don't allow a fragment of TCP 8 bytes in. Nobody normal |
79 | causes this. Its a cracker trying to break in by doing a |
80 | flag overwrite to pass the direction checks. |
81 | */ |
82 | if (par->fragoff == 1) { |
83 | pr_debug("Dropping evil TCP offset=1 frag.\n" ); |
84 | par->hotdrop = true; |
85 | } |
86 | /* Must not be a fragment. */ |
87 | return false; |
88 | } |
89 | |
90 | th = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_tcph), buffer: &_tcph); |
91 | if (th == NULL) { |
92 | /* We've been asked to examine this packet, and we |
93 | can't. Hence, no choice but to drop. */ |
94 | pr_debug("Dropping evil TCP offset=0 tinygram.\n" ); |
95 | par->hotdrop = true; |
96 | return false; |
97 | } |
98 | |
99 | if (!port_match(min: tcpinfo->spts[0], max: tcpinfo->spts[1], |
100 | ntohs(th->source), |
101 | invert: !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) |
102 | return false; |
103 | if (!port_match(min: tcpinfo->dpts[0], max: tcpinfo->dpts[1], |
104 | ntohs(th->dest), |
105 | invert: !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) |
106 | return false; |
107 | if (!NF_INVF(tcpinfo, XT_TCP_INV_FLAGS, |
108 | (((unsigned char *)th)[13] & tcpinfo->flg_mask) == tcpinfo->flg_cmp)) |
109 | return false; |
110 | if (tcpinfo->option) { |
111 | if (th->doff * 4 < sizeof(_tcph)) { |
112 | par->hotdrop = true; |
113 | return false; |
114 | } |
115 | if (!tcp_find_option(option: tcpinfo->option, skb, protoff: par->thoff, |
116 | optlen: th->doff*4 - sizeof(_tcph), |
117 | invert: tcpinfo->invflags & XT_TCP_INV_OPTION, |
118 | hotdrop: &par->hotdrop)) |
119 | return false; |
120 | } |
121 | return true; |
122 | } |
123 | |
124 | static int tcp_mt_check(const struct xt_mtchk_param *par) |
125 | { |
126 | const struct xt_tcp *tcpinfo = par->matchinfo; |
127 | |
128 | /* Must specify no unknown invflags */ |
129 | return (tcpinfo->invflags & ~XT_TCP_INV_MASK) ? -EINVAL : 0; |
130 | } |
131 | |
132 | static bool udp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
133 | { |
134 | const struct udphdr *uh; |
135 | struct udphdr _udph; |
136 | const struct xt_udp *udpinfo = par->matchinfo; |
137 | |
138 | /* Must not be a fragment. */ |
139 | if (par->fragoff != 0) |
140 | return false; |
141 | |
142 | uh = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_udph), buffer: &_udph); |
143 | if (uh == NULL) { |
144 | /* We've been asked to examine this packet, and we |
145 | can't. Hence, no choice but to drop. */ |
146 | pr_debug("Dropping evil UDP tinygram.\n" ); |
147 | par->hotdrop = true; |
148 | return false; |
149 | } |
150 | |
151 | return port_match(min: udpinfo->spts[0], max: udpinfo->spts[1], |
152 | ntohs(uh->source), |
153 | invert: !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) |
154 | && port_match(min: udpinfo->dpts[0], max: udpinfo->dpts[1], |
155 | ntohs(uh->dest), |
156 | invert: !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); |
157 | } |
158 | |
159 | static int udp_mt_check(const struct xt_mtchk_param *par) |
160 | { |
161 | const struct xt_udp *udpinfo = par->matchinfo; |
162 | |
163 | /* Must specify no unknown invflags */ |
164 | return (udpinfo->invflags & ~XT_UDP_INV_MASK) ? -EINVAL : 0; |
165 | } |
166 | |
167 | /* Returns 1 if the type and code is matched by the range, 0 otherwise */ |
168 | static bool type_code_in_range(u8 test_type, u8 min_code, u8 max_code, |
169 | u8 type, u8 code) |
170 | { |
171 | return type == test_type && code >= min_code && code <= max_code; |
172 | } |
173 | |
174 | static bool icmp_type_code_match(u8 test_type, u8 min_code, u8 max_code, |
175 | u8 type, u8 code, bool invert) |
176 | { |
177 | return (test_type == 0xFF || |
178 | type_code_in_range(test_type, min_code, max_code, type, code)) |
179 | ^ invert; |
180 | } |
181 | |
182 | static bool icmp6_type_code_match(u8 test_type, u8 min_code, u8 max_code, |
183 | u8 type, u8 code, bool invert) |
184 | { |
185 | return type_code_in_range(test_type, min_code, max_code, type, code) ^ invert; |
186 | } |
187 | |
188 | static bool |
189 | icmp_match(const struct sk_buff *skb, struct xt_action_param *par) |
190 | { |
191 | const struct icmphdr *ic; |
192 | struct icmphdr _icmph; |
193 | const struct ipt_icmp *icmpinfo = par->matchinfo; |
194 | |
195 | /* Must not be a fragment. */ |
196 | if (par->fragoff != 0) |
197 | return false; |
198 | |
199 | ic = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_icmph), buffer: &_icmph); |
200 | if (!ic) { |
201 | /* We've been asked to examine this packet, and we |
202 | * can't. Hence, no choice but to drop. |
203 | */ |
204 | par->hotdrop = true; |
205 | return false; |
206 | } |
207 | |
208 | return icmp_type_code_match(test_type: icmpinfo->type, |
209 | min_code: icmpinfo->code[0], |
210 | max_code: icmpinfo->code[1], |
211 | type: ic->type, code: ic->code, |
212 | invert: !!(icmpinfo->invflags & IPT_ICMP_INV)); |
213 | } |
214 | |
215 | static bool |
216 | icmp6_match(const struct sk_buff *skb, struct xt_action_param *par) |
217 | { |
218 | const struct icmp6hdr *ic; |
219 | struct icmp6hdr _icmph; |
220 | const struct ip6t_icmp *icmpinfo = par->matchinfo; |
221 | |
222 | /* Must not be a fragment. */ |
223 | if (par->fragoff != 0) |
224 | return false; |
225 | |
226 | ic = skb_header_pointer(skb, offset: par->thoff, len: sizeof(_icmph), buffer: &_icmph); |
227 | if (!ic) { |
228 | /* We've been asked to examine this packet, and we |
229 | * can't. Hence, no choice but to drop. |
230 | */ |
231 | par->hotdrop = true; |
232 | return false; |
233 | } |
234 | |
235 | return icmp6_type_code_match(test_type: icmpinfo->type, |
236 | min_code: icmpinfo->code[0], |
237 | max_code: icmpinfo->code[1], |
238 | type: ic->icmp6_type, code: ic->icmp6_code, |
239 | invert: !!(icmpinfo->invflags & IP6T_ICMP_INV)); |
240 | } |
241 | |
242 | static int icmp_checkentry(const struct xt_mtchk_param *par) |
243 | { |
244 | const struct ipt_icmp *icmpinfo = par->matchinfo; |
245 | |
246 | return (icmpinfo->invflags & ~IPT_ICMP_INV) ? -EINVAL : 0; |
247 | } |
248 | |
249 | static int icmp6_checkentry(const struct xt_mtchk_param *par) |
250 | { |
251 | const struct ip6t_icmp *icmpinfo = par->matchinfo; |
252 | |
253 | return (icmpinfo->invflags & ~IP6T_ICMP_INV) ? -EINVAL : 0; |
254 | } |
255 | |
256 | static struct xt_match tcpudp_mt_reg[] __read_mostly = { |
257 | { |
258 | .name = "tcp" , |
259 | .family = NFPROTO_IPV4, |
260 | .checkentry = tcp_mt_check, |
261 | .match = tcp_mt, |
262 | .matchsize = sizeof(struct xt_tcp), |
263 | .proto = IPPROTO_TCP, |
264 | .me = THIS_MODULE, |
265 | }, |
266 | { |
267 | .name = "tcp" , |
268 | .family = NFPROTO_IPV6, |
269 | .checkentry = tcp_mt_check, |
270 | .match = tcp_mt, |
271 | .matchsize = sizeof(struct xt_tcp), |
272 | .proto = IPPROTO_TCP, |
273 | .me = THIS_MODULE, |
274 | }, |
275 | { |
276 | .name = "udp" , |
277 | .family = NFPROTO_IPV4, |
278 | .checkentry = udp_mt_check, |
279 | .match = udp_mt, |
280 | .matchsize = sizeof(struct xt_udp), |
281 | .proto = IPPROTO_UDP, |
282 | .me = THIS_MODULE, |
283 | }, |
284 | { |
285 | .name = "udp" , |
286 | .family = NFPROTO_IPV6, |
287 | .checkentry = udp_mt_check, |
288 | .match = udp_mt, |
289 | .matchsize = sizeof(struct xt_udp), |
290 | .proto = IPPROTO_UDP, |
291 | .me = THIS_MODULE, |
292 | }, |
293 | { |
294 | .name = "udplite" , |
295 | .family = NFPROTO_IPV4, |
296 | .checkentry = udp_mt_check, |
297 | .match = udp_mt, |
298 | .matchsize = sizeof(struct xt_udp), |
299 | .proto = IPPROTO_UDPLITE, |
300 | .me = THIS_MODULE, |
301 | }, |
302 | { |
303 | .name = "udplite" , |
304 | .family = NFPROTO_IPV6, |
305 | .checkentry = udp_mt_check, |
306 | .match = udp_mt, |
307 | .matchsize = sizeof(struct xt_udp), |
308 | .proto = IPPROTO_UDPLITE, |
309 | .me = THIS_MODULE, |
310 | }, |
311 | { |
312 | .name = "icmp" , |
313 | .match = icmp_match, |
314 | .matchsize = sizeof(struct ipt_icmp), |
315 | .checkentry = icmp_checkentry, |
316 | .proto = IPPROTO_ICMP, |
317 | .family = NFPROTO_IPV4, |
318 | .me = THIS_MODULE, |
319 | }, |
320 | { |
321 | .name = "icmp6" , |
322 | .match = icmp6_match, |
323 | .matchsize = sizeof(struct ip6t_icmp), |
324 | .checkentry = icmp6_checkentry, |
325 | .proto = IPPROTO_ICMPV6, |
326 | .family = NFPROTO_IPV6, |
327 | .me = THIS_MODULE, |
328 | }, |
329 | }; |
330 | |
331 | static int __init tcpudp_mt_init(void) |
332 | { |
333 | return xt_register_matches(match: tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
334 | } |
335 | |
336 | static void __exit tcpudp_mt_exit(void) |
337 | { |
338 | xt_unregister_matches(match: tcpudp_mt_reg, ARRAY_SIZE(tcpudp_mt_reg)); |
339 | } |
340 | |
341 | module_init(tcpudp_mt_init); |
342 | module_exit(tcpudp_mt_exit); |
343 | |