| 1 | /* |
| 2 | * IP6 tables REJECT target module |
| 3 | * Linux INET6 implementation |
| 4 | * |
| 5 | * Copyright (C)2003 USAGI/WIDE Project |
| 6 | * |
| 7 | * Authors: |
| 8 | * Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp> |
| 9 | * |
| 10 | * Based on net/ipv4/netfilter/ipt_REJECT.c |
| 11 | * |
| 12 | * This program is free software; you can redistribute it and/or |
| 13 | * modify it under the terms of the GNU General Public License |
| 14 | * as published by the Free Software Foundation; either version |
| 15 | * 2 of the License, or (at your option) any later version. |
| 16 | */ |
| 17 | |
| 18 | #include <linux/module.h> |
| 19 | #include <linux/skbuff.h> |
| 20 | #include <linux/icmpv6.h> |
| 21 | #include <linux/netdevice.h> |
| 22 | #include <net/ipv6.h> |
| 23 | #include <net/tcp.h> |
| 24 | #include <net/icmp.h> |
| 25 | #include <net/ip6_checksum.h> |
| 26 | #include <net/ip6_fib.h> |
| 27 | #include <net/ip6_route.h> |
| 28 | #include <net/flow.h> |
| 29 | #include <linux/netfilter/x_tables.h> |
| 30 | #include <linux/netfilter_ipv6/ip6_tables.h> |
| 31 | #include <linux/netfilter_ipv6/ip6t_REJECT.h> |
| 32 | |
| 33 | MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>"); |
| 34 | MODULE_DESCRIPTION("IP6 tables REJECT target module"); |
| 35 | MODULE_LICENSE("GPL"); |
| 36 | |
| 37 | #if 0 |
| 38 | #define DEBUGP printk |
| 39 | #else |
| 40 | #define DEBUGP(format, args...) |
| 41 | #endif |
| 42 | |
| 43 | /* Send RST reply */ |
| 44 | static void send_reset(struct sk_buff *oldskb) |
| 45 | { |
| 46 | struct sk_buff *nskb; |
| 47 | struct tcphdr otcph, *tcph; |
| 48 | unsigned int otcplen, hh_len; |
| 49 | int tcphoff, needs_ack; |
| 50 | struct ipv6hdr *oip6h = ipv6_hdr(oldskb), *ip6h; |
| 51 | struct dst_entry *dst = NULL; |
| 52 | u8 proto; |
| 53 | struct flowi fl; |
| 54 | |
| 55 | if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) || |
| 56 | (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) { |
| 57 | DEBUGP("ip6t_REJECT: addr is not unicast.\n"); |
| 58 | return; |
| 59 | } |
| 60 | |
| 61 | proto = oip6h->nexthdr; |
| 62 | tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto); |
| 63 | |
| 64 | if ((tcphoff < 0) || (tcphoff > oldskb->len)) { |
| 65 | DEBUGP("ip6t_REJECT: Can't get TCP header.\n"); |
| 66 | return; |
| 67 | } |
| 68 | |
| 69 | otcplen = oldskb->len - tcphoff; |
| 70 | |
| 71 | /* IP header checks: fragment, too short. */ |
| 72 | if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) { |
| 73 | DEBUGP("ip6t_REJECT: proto(%d) != IPPROTO_TCP, or too short. otcplen = %d\n", |
| 74 | proto, otcplen); |
| 75 | return; |
| 76 | } |
| 77 | |
| 78 | if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr))) |
| 79 | BUG(); |
| 80 | |
| 81 | /* No RST for RST. */ |
| 82 | if (otcph.rst) { |
| 83 | DEBUGP("ip6t_REJECT: RST is set\n"); |
| 84 | return; |
| 85 | } |
| 86 | |
| 87 | /* Check checksum. */ |
| 88 | if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP, |
| 89 | skb_checksum(oldskb, tcphoff, otcplen, 0))) { |
| 90 | DEBUGP("ip6t_REJECT: TCP checksum is invalid\n"); |
| 91 | return; |
| 92 | } |
| 93 | |
| 94 | memset(&fl, 0, sizeof(fl)); |
| 95 | fl.proto = IPPROTO_TCP; |
| 96 | ipv6_addr_copy(&fl.fl6_src, &oip6h->daddr); |
| 97 | ipv6_addr_copy(&fl.fl6_dst, &oip6h->saddr); |
| 98 | fl.fl_ip_sport = otcph.dest; |
| 99 | fl.fl_ip_dport = otcph.source; |
| 100 | security_skb_classify_flow(oldskb, &fl); |
| 101 | dst = ip6_route_output(NULL, &fl); |
| 102 | if (dst == NULL) |
| 103 | return; |
| 104 | if (dst->error || xfrm_lookup(&dst, &fl, NULL, 0)) |
| 105 | return; |
| 106 | |
| 107 | hh_len = (dst->dev->hard_header_len + 15)&~15; |
| 108 | nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr) |
| 109 | + sizeof(struct tcphdr) + dst->trailer_len, |
| 110 | GFP_ATOMIC); |
| 111 | |
| 112 | if (!nskb) { |
| 113 | if (net_ratelimit()) |
| 114 | printk("ip6t_REJECT: Can't alloc skb\n"); |
| 115 | dst_release(dst); |
| 116 | return; |
| 117 | } |
| 118 | |
| 119 | nskb->dst = dst; |
| 120 | |
| 121 | skb_reserve(nskb, hh_len + dst->header_len); |
| 122 | |
| 123 | skb_put(nskb, sizeof(struct ipv6hdr)); |
| 124 | skb_reset_network_header(nskb); |
| 125 | ip6h = ipv6_hdr(nskb); |
| 126 | ip6h->version = 6; |
| 127 | ip6h->hop_limit = dst_metric(dst, RTAX_HOPLIMIT); |
| 128 | ip6h->nexthdr = IPPROTO_TCP; |
| 129 | ip6h->payload_len = htons(sizeof(struct tcphdr)); |
| 130 | ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr); |
| 131 | ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr); |
| 132 | |
| 133 | tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); |
| 134 | /* Truncate to length (no data) */ |
| 135 | tcph->doff = sizeof(struct tcphdr)/4; |
| 136 | tcph->source = otcph.dest; |
| 137 | tcph->dest = otcph.source; |
| 138 | |
| 139 | if (otcph.ack) { |
| 140 | needs_ack = 0; |
| 141 | tcph->seq = otcph.ack_seq; |
| 142 | tcph->ack_seq = 0; |
| 143 | } else { |
| 144 | needs_ack = 1; |
| 145 | tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin |
| 146 | + otcplen - (otcph.doff<<2)); |
| 147 | tcph->seq = 0; |
| 148 | } |
| 149 | |
| 150 | /* Reset flags */ |
| 151 | ((u_int8_t *)tcph)[13] = 0; |
| 152 | tcph->rst = 1; |
| 153 | tcph->ack = needs_ack; |
| 154 | tcph->window = 0; |
| 155 | tcph->urg_ptr = 0; |
| 156 | tcph->check = 0; |
| 157 | |
| 158 | /* Adjust TCP checksum */ |
| 159 | tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, |
| 160 | &ipv6_hdr(nskb)->daddr, |
| 161 | sizeof(struct tcphdr), IPPROTO_TCP, |
| 162 | csum_partial(tcph, |
| 163 | sizeof(struct tcphdr), 0)); |
| 164 | |
| 165 | nf_ct_attach(nskb, oldskb); |
| 166 | |
| 167 | NF_HOOK(PF_INET6, NF_IP6_LOCAL_OUT, nskb, NULL, nskb->dst->dev, |
| 168 | dst_output); |
| 169 | } |
| 170 | |
| 171 | static inline void |
| 172 | send_unreach(struct sk_buff *skb_in, unsigned char code, unsigned int hooknum) |
| 173 | { |
| 174 | if (hooknum == NF_IP6_LOCAL_OUT && skb_in->dev == NULL) |
| 175 | skb_in->dev = &loopback_dev; |
| 176 | |
| 177 | icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0, NULL); |
| 178 | } |
| 179 | |
| 180 | static unsigned int reject6_target(struct sk_buff **pskb, |
| 181 | const struct net_device *in, |
| 182 | const struct net_device *out, |
| 183 | unsigned int hooknum, |
| 184 | const struct xt_target *target, |
| 185 | const void *targinfo) |
| 186 | { |
| 187 | const struct ip6t_reject_info *reject = targinfo; |
| 188 | |
| 189 | DEBUGP(KERN_DEBUG "%s: medium point\n", __FUNCTION__); |
| 190 | /* WARNING: This code causes reentry within ip6tables. |
| 191 | This means that the ip6tables jump stack is now crap. We |
| 192 | must return an absolute verdict. --RR */ |
| 193 | switch (reject->with) { |
| 194 | case IP6T_ICMP6_NO_ROUTE: |
| 195 | send_unreach(*pskb, ICMPV6_NOROUTE, hooknum); |
| 196 | break; |
| 197 | case IP6T_ICMP6_ADM_PROHIBITED: |
| 198 | send_unreach(*pskb, ICMPV6_ADM_PROHIBITED, hooknum); |
| 199 | break; |
| 200 | case IP6T_ICMP6_NOT_NEIGHBOUR: |
| 201 | send_unreach(*pskb, ICMPV6_NOT_NEIGHBOUR, hooknum); |
| 202 | break; |
| 203 | case IP6T_ICMP6_ADDR_UNREACH: |
| 204 | send_unreach(*pskb, ICMPV6_ADDR_UNREACH, hooknum); |
| 205 | break; |
| 206 | case IP6T_ICMP6_PORT_UNREACH: |
| 207 | send_unreach(*pskb, ICMPV6_PORT_UNREACH, hooknum); |
| 208 | break; |
| 209 | case IP6T_ICMP6_ECHOREPLY: |
| 210 | /* Do nothing */ |
| 211 | break; |
| 212 | case IP6T_TCP_RESET: |
| 213 | send_reset(*pskb); |
| 214 | break; |
| 215 | default: |
| 216 | if (net_ratelimit()) |
| 217 | printk(KERN_WARNING "ip6t_REJECT: case %u not handled yet\n", reject->with); |
| 218 | break; |
| 219 | } |
| 220 | |
| 221 | return NF_DROP; |
| 222 | } |
| 223 | |
| 224 | static bool check(const char *tablename, |
| 225 | const void *entry, |
| 226 | const struct xt_target *target, |
| 227 | void *targinfo, |
| 228 | unsigned int hook_mask) |
| 229 | { |
| 230 | const struct ip6t_reject_info *rejinfo = targinfo; |
| 231 | const struct ip6t_entry *e = entry; |
| 232 | |
| 233 | if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) { |
| 234 | printk("ip6t_REJECT: ECHOREPLY is not supported.\n"); |
| 235 | return false; |
| 236 | } else if (rejinfo->with == IP6T_TCP_RESET) { |
| 237 | /* Must specify that it's a TCP packet */ |
| 238 | if (e->ipv6.proto != IPPROTO_TCP |
| 239 | || (e->ipv6.invflags & XT_INV_PROTO)) { |
| 240 | DEBUGP("ip6t_REJECT: TCP_RESET illegal for non-tcp\n"); |
| 241 | return false; |
| 242 | } |
| 243 | } |
| 244 | return true; |
| 245 | } |
| 246 | |
| 247 | static struct xt_target ip6t_reject_reg = { |
| 248 | .name = "REJECT", |
| 249 | .family = AF_INET6, |
| 250 | .target = reject6_target, |
| 251 | .targetsize = sizeof(struct ip6t_reject_info), |
| 252 | .table = "filter", |
| 253 | .hooks = (1 << NF_IP6_LOCAL_IN) | (1 << NF_IP6_FORWARD) | |
| 254 | (1 << NF_IP6_LOCAL_OUT), |
| 255 | .checkentry = check, |
| 256 | .me = THIS_MODULE |
| 257 | }; |
| 258 | |
| 259 | static int __init ip6t_reject_init(void) |
| 260 | { |
| 261 | return xt_register_target(&ip6t_reject_reg); |
| 262 | } |
| 263 | |
| 264 | static void __exit ip6t_reject_fini(void) |
| 265 | { |
| 266 | xt_unregister_target(&ip6t_reject_reg); |
| 267 | } |
| 268 | |
| 269 | module_init(ip6t_reject_init); |
| 270 | module_exit(ip6t_reject_fini); |