Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * This is a module which is used for rejecting packets. | |
3 | * Added support for customized reject packets (Jozsef Kadlecsik). | |
4 | * Added support for ICMP type-3-code-13 (Maciej Soltysiak). [RFC 1812] | |
5 | */ | |
6 | ||
7 | /* (C) 1999-2001 Paul `Rusty' Russell | |
8 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> | |
9 | * | |
10 | * This program is free software; you can redistribute it and/or modify | |
11 | * it under the terms of the GNU General Public License version 2 as | |
12 | * published by the Free Software Foundation. | |
13 | */ | |
14 | ||
1da177e4 LT |
15 | #include <linux/module.h> |
16 | #include <linux/skbuff.h> | |
17 | #include <linux/ip.h> | |
18 | #include <linux/udp.h> | |
19 | #include <linux/icmp.h> | |
20 | #include <net/icmp.h> | |
21 | #include <net/ip.h> | |
22 | #include <net/tcp.h> | |
23 | #include <net/route.h> | |
24 | #include <net/dst.h> | |
25 | #include <linux/netfilter_ipv4/ip_tables.h> | |
26 | #include <linux/netfilter_ipv4/ipt_REJECT.h> | |
27 | #ifdef CONFIG_BRIDGE_NETFILTER | |
28 | #include <linux/netfilter_bridge.h> | |
29 | #endif | |
30 | ||
31 | MODULE_LICENSE("GPL"); | |
32 | MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); | |
33 | MODULE_DESCRIPTION("iptables REJECT target module"); | |
34 | ||
35 | #if 0 | |
36 | #define DEBUGP printk | |
37 | #else | |
38 | #define DEBUGP(format, args...) | |
39 | #endif | |
40 | ||
1da177e4 LT |
41 | /* Send RST reply */ |
42 | static void send_reset(struct sk_buff *oldskb, int hook) | |
43 | { | |
44 | struct sk_buff *nskb; | |
6150bacf | 45 | struct iphdr *iph = oldskb->nh.iph; |
1da177e4 | 46 | struct tcphdr _otcph, *oth, *tcph; |
6a19d614 AV |
47 | __be16 tmp_port; |
48 | __be32 tmp_addr; | |
1da177e4 | 49 | int needs_ack; |
9d02002d | 50 | unsigned int addr_type; |
1da177e4 LT |
51 | |
52 | /* IP header checks: fragment. */ | |
53 | if (oldskb->nh.iph->frag_off & htons(IP_OFFSET)) | |
54 | return; | |
55 | ||
56 | oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4, | |
57 | sizeof(_otcph), &_otcph); | |
58 | if (oth == NULL) | |
59 | return; | |
60 | ||
61 | /* No RST for RST. */ | |
62 | if (oth->rst) | |
63 | return; | |
64 | ||
6150bacf | 65 | /* Check checksum */ |
96f6bf82 | 66 | if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP)) |
6150bacf PM |
67 | return; |
68 | ||
1da177e4 LT |
69 | /* We need a linear, writeable skb. We also need to expand |
70 | headroom in case hh_len of incoming interface < hh_len of | |
71 | outgoing interface */ | |
9d02002d | 72 | nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb), |
1da177e4 | 73 | GFP_ATOMIC); |
9d02002d | 74 | if (!nskb) |
1da177e4 | 75 | return; |
1da177e4 LT |
76 | |
77 | /* This packet will not be the same as the other: clear nf fields */ | |
78 | nf_reset(nskb); | |
82e91ffe | 79 | nskb->mark = 0; |
984bc16c | 80 | skb_init_secmark(nskb); |
1da177e4 LT |
81 | |
82 | tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl); | |
83 | ||
84 | /* Swap source and dest */ | |
85 | tmp_addr = nskb->nh.iph->saddr; | |
86 | nskb->nh.iph->saddr = nskb->nh.iph->daddr; | |
87 | nskb->nh.iph->daddr = tmp_addr; | |
88 | tmp_port = tcph->source; | |
89 | tcph->source = tcph->dest; | |
90 | tcph->dest = tmp_port; | |
91 | ||
92 | /* Truncate to length (no data) */ | |
93 | tcph->doff = sizeof(struct tcphdr)/4; | |
94 | skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr)); | |
95 | nskb->nh.iph->tot_len = htons(nskb->len); | |
96 | ||
97 | if (tcph->ack) { | |
98 | needs_ack = 0; | |
99 | tcph->seq = oth->ack_seq; | |
100 | tcph->ack_seq = 0; | |
101 | } else { | |
102 | needs_ack = 1; | |
103 | tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin | |
104 | + oldskb->len - oldskb->nh.iph->ihl*4 | |
105 | - (oth->doff<<2)); | |
106 | tcph->seq = 0; | |
107 | } | |
108 | ||
109 | /* Reset flags */ | |
110 | ((u_int8_t *)tcph)[13] = 0; | |
111 | tcph->rst = 1; | |
112 | tcph->ack = needs_ack; | |
113 | ||
114 | tcph->window = 0; | |
115 | tcph->urg_ptr = 0; | |
116 | ||
af443b6d PM |
117 | /* Adjust TCP checksum */ |
118 | tcph->check = 0; | |
119 | tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr), | |
120 | nskb->nh.iph->saddr, | |
121 | nskb->nh.iph->daddr, | |
122 | csum_partial((char *)tcph, | |
123 | sizeof(struct tcphdr), 0)); | |
124 | ||
9d02002d PM |
125 | /* Set DF, id = 0 */ |
126 | nskb->nh.iph->frag_off = htons(IP_DF); | |
127 | nskb->nh.iph->id = 0; | |
128 | ||
129 | addr_type = RTN_UNSPEC; | |
130 | if (hook != NF_IP_FORWARD | |
131 | #ifdef CONFIG_BRIDGE_NETFILTER | |
132 | || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED) | |
133 | #endif | |
134 | ) | |
135 | addr_type = RTN_LOCAL; | |
136 | ||
137 | if (ip_route_me_harder(&nskb, addr_type)) | |
138 | goto free_nskb; | |
139 | ||
4cf411de | 140 | nskb->ip_summed = CHECKSUM_NONE; |
af443b6d | 141 | |
9d02002d | 142 | /* Adjust IP TTL */ |
e8eaedf2 | 143 | nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT); |
1da177e4 LT |
144 | |
145 | /* Adjust IP checksum */ | |
146 | nskb->nh.iph->check = 0; | |
147 | nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph, | |
148 | nskb->nh.iph->ihl); | |
149 | ||
150 | /* "Never happens" */ | |
151 | if (nskb->len > dst_mtu(nskb->dst)) | |
152 | goto free_nskb; | |
153 | ||
154 | nf_ct_attach(nskb, oldskb); | |
155 | ||
156 | NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev, | |
157 | dst_output); | |
158 | return; | |
159 | ||
160 | free_nskb: | |
161 | kfree_skb(nskb); | |
162 | } | |
163 | ||
164 | static inline void send_unreach(struct sk_buff *skb_in, int code) | |
165 | { | |
166 | icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); | |
167 | } | |
168 | ||
169 | static unsigned int reject(struct sk_buff **pskb, | |
170 | const struct net_device *in, | |
171 | const struct net_device *out, | |
172 | unsigned int hooknum, | |
c4986734 | 173 | const struct xt_target *target, |
fe1cb108 | 174 | const void *targinfo) |
1da177e4 LT |
175 | { |
176 | const struct ipt_reject_info *reject = targinfo; | |
177 | ||
178 | /* Our naive response construction doesn't deal with IP | |
179 | options, and probably shouldn't try. */ | |
180 | if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr)) | |
181 | return NF_DROP; | |
182 | ||
183 | /* WARNING: This code causes reentry within iptables. | |
184 | This means that the iptables jump stack is now crap. We | |
185 | must return an absolute verdict. --RR */ | |
186 | switch (reject->with) { | |
187 | case IPT_ICMP_NET_UNREACHABLE: | |
188 | send_unreach(*pskb, ICMP_NET_UNREACH); | |
189 | break; | |
190 | case IPT_ICMP_HOST_UNREACHABLE: | |
191 | send_unreach(*pskb, ICMP_HOST_UNREACH); | |
192 | break; | |
193 | case IPT_ICMP_PROT_UNREACHABLE: | |
194 | send_unreach(*pskb, ICMP_PROT_UNREACH); | |
195 | break; | |
196 | case IPT_ICMP_PORT_UNREACHABLE: | |
197 | send_unreach(*pskb, ICMP_PORT_UNREACH); | |
198 | break; | |
199 | case IPT_ICMP_NET_PROHIBITED: | |
200 | send_unreach(*pskb, ICMP_NET_ANO); | |
201 | break; | |
202 | case IPT_ICMP_HOST_PROHIBITED: | |
203 | send_unreach(*pskb, ICMP_HOST_ANO); | |
204 | break; | |
205 | case IPT_ICMP_ADMIN_PROHIBITED: | |
206 | send_unreach(*pskb, ICMP_PKT_FILTERED); | |
207 | break; | |
208 | case IPT_TCP_RESET: | |
209 | send_reset(*pskb, hooknum); | |
210 | case IPT_ICMP_ECHOREPLY: | |
211 | /* Doesn't happen. */ | |
212 | break; | |
213 | } | |
214 | ||
215 | return NF_DROP; | |
216 | } | |
217 | ||
218 | static int check(const char *tablename, | |
2e4e6a17 | 219 | const void *e_void, |
c4986734 | 220 | const struct xt_target *target, |
1da177e4 | 221 | void *targinfo, |
1da177e4 LT |
222 | unsigned int hook_mask) |
223 | { | |
224 | const struct ipt_reject_info *rejinfo = targinfo; | |
2e4e6a17 | 225 | const struct ipt_entry *e = e_void; |
1da177e4 | 226 | |
1da177e4 LT |
227 | if (rejinfo->with == IPT_ICMP_ECHOREPLY) { |
228 | printk("REJECT: ECHOREPLY no longer supported.\n"); | |
229 | return 0; | |
230 | } else if (rejinfo->with == IPT_TCP_RESET) { | |
231 | /* Must specify that it's a TCP packet */ | |
232 | if (e->ip.proto != IPPROTO_TCP | |
233 | || (e->ip.invflags & IPT_INV_PROTO)) { | |
234 | DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n"); | |
235 | return 0; | |
236 | } | |
237 | } | |
1da177e4 LT |
238 | return 1; |
239 | } | |
240 | ||
241 | static struct ipt_target ipt_reject_reg = { | |
242 | .name = "REJECT", | |
243 | .target = reject, | |
1d5cd909 PM |
244 | .targetsize = sizeof(struct ipt_reject_info), |
245 | .table = "filter", | |
246 | .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | | |
247 | (1 << NF_IP_LOCAL_OUT), | |
1da177e4 LT |
248 | .checkentry = check, |
249 | .me = THIS_MODULE, | |
250 | }; | |
251 | ||
65b4b4e8 | 252 | static int __init ipt_reject_init(void) |
1da177e4 LT |
253 | { |
254 | return ipt_register_target(&ipt_reject_reg); | |
255 | } | |
256 | ||
65b4b4e8 | 257 | static void __exit ipt_reject_fini(void) |
1da177e4 LT |
258 | { |
259 | ipt_unregister_target(&ipt_reject_reg); | |
260 | } | |
261 | ||
65b4b4e8 AM |
262 | module_init(ipt_reject_init); |
263 | module_exit(ipt_reject_fini); |