net/netfilter/xt_dccp.c

   1 /*
   2  * iptables module for DCCP protocol header matching
   3  *
   4  * (C) 2005 by Harald Welte <laforge@netfilter.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/spinlock.h>
  14 #include <net/ip.h>
  15 #include <linux/dccp.h>
  16
  17 #include <linux/netfilter/x_tables.h>
  18 #include <linux/netfilter/xt_dccp.h>
  19
  20 #include <linux/netfilter_ipv4/ip_tables.h>
  21 #include <linux/netfilter_ipv6/ip6_tables.h>
  22
  23 MODULE_LICENSE("GPL");
  24 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  25 MODULE_DESCRIPTION("Match for DCCP protocol packets");
  26 MODULE_ALIAS("ipt_dccp");
  27
  28 #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
  29                                   || (!!((invflag) & (option)) ^ (cond)))
  30
  31 static unsigned char *dccp_optbuf;
  32 static DEFINE_SPINLOCK(dccp_buflock);
  33
  34 static inline int
  35 dccp_find_option(u_int8_t option,
  36                  const struct sk_buff *skb,
  37                  unsigned int protoff,
  38                  const struct dccp_hdr *dh,
  39                  int *hotdrop)
  40 {
  41         /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
  42         unsigned char *op;
  43         unsigned int optoff = __dccp_hdr_len(dh);
  44         unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
  45         unsigned int i;
  46
  47         if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) {
  48                 *hotdrop = 1;
  49                 return 0;
  50         }
  51
  52         if (!optlen)
  53                 return 0;
  54
  55         spin_lock_bh(&dccp_buflock);
  56         op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
  57         if (op == NULL) {
  58                 /* If we don't have the whole header, drop packet. */
  59                 spin_unlock_bh(&dccp_buflock);
  60                 *hotdrop = 1;
  61                 return 0;
  62         }
  63
  64         for (i = 0; i < optlen; ) {
  65                 if (op[i] == option) {
  66                         spin_unlock_bh(&dccp_buflock);
  67                         return 1;
  68                 }
  69
  70                 if (op[i] < 2)
  71                         i++;
  72                 else
  73                         i += op[i+1]?:1;
  74         }
  75
  76         spin_unlock_bh(&dccp_buflock);
  77         return 0;
  78 }
  79
  80
  81 static inline int
  82 match_types(const struct dccp_hdr *dh, u_int16_t typemask)
  83 {
  84         return (typemask & (1 << dh->dccph_type));
  85 }
  86
  87 static inline int
  88 match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
  89              const struct dccp_hdr *dh, int *hotdrop)
  90 {
  91         return dccp_find_option(option, skb, protoff, dh, hotdrop);
  92 }
  93
  94 static int
  95 match(const struct sk_buff *skb,
  96       const struct net_device *in,
  97       const struct net_device *out,
  98       const void *matchinfo,
  99       int offset,
 100       unsigned int protoff,
 101       int *hotdrop)
 102 {
 103         const struct xt_dccp_info *info =
 104                                 (const struct xt_dccp_info *)matchinfo;
 105         struct dccp_hdr _dh, *dh;
 106
 107         if (offset)
 108                 return 0;
 109
 110         dh = skb_header_pointer(skb, protoff, sizeof(_dh), &_dh);
 111         if (dh == NULL) {
 112                 *hotdrop = 1;
 113                 return 0;
 114         }
 115
 116         return  DCCHECK(((ntohs(dh->dccph_sport) >= info->spts[0])
 117                         && (ntohs(dh->dccph_sport) <= info->spts[1])),
 118                         XT_DCCP_SRC_PORTS, info->flags, info->invflags)
 119                 && DCCHECK(((ntohs(dh->dccph_dport) >= info->dpts[0])
 120                         && (ntohs(dh->dccph_dport) <= info->dpts[1])),
 121                         XT_DCCP_DEST_PORTS, info->flags, info->invflags)
 122                 && DCCHECK(match_types(dh, info->typemask),
 123                            XT_DCCP_TYPE, info->flags, info->invflags)
 124                 && DCCHECK(match_option(info->option, skb, protoff, dh,
 125                                         hotdrop),
 126                            XT_DCCP_OPTION, info->flags, info->invflags);
 127 }
 128
 129 static int
 130 checkentry(const char *tablename,
 131            const void *inf,
 132            void *matchinfo,
 133            unsigned int matchsize,
 134            unsigned int hook_mask)
 135 {
 136         const struct ipt_ip *ip = inf;
 137         const struct xt_dccp_info *info;
 138
 139         info = (const struct xt_dccp_info *)matchinfo;
 140
 141         return ip->proto == IPPROTO_DCCP
 142                 && !(ip->invflags & XT_INV_PROTO)
 143                 && matchsize == XT_ALIGN(sizeof(struct xt_dccp_info))
 144                 && !(info->flags & ~XT_DCCP_VALID_FLAGS)
 145                 && !(info->invflags & ~XT_DCCP_VALID_FLAGS)
 146                 && !(info->invflags & ~info->flags);
 147 }
 148
 149 static int
 150 checkentry6(const char *tablename,
 151            const void *inf,
 152            void *matchinfo,
 153            unsigned int matchsize,
 154            unsigned int hook_mask)
 155 {
 156         const struct ip6t_ip6 *ip = inf;
 157         const struct xt_dccp_info *info;
 158
 159         info = (const struct xt_dccp_info *)matchinfo;
 160
 161         return ip->proto == IPPROTO_DCCP
 162                 && !(ip->invflags & XT_INV_PROTO)
 163                 && matchsize == XT_ALIGN(sizeof(struct xt_dccp_info))
 164                 && !(info->flags & ~XT_DCCP_VALID_FLAGS)
 165                 && !(info->invflags & ~XT_DCCP_VALID_FLAGS)
 166                 && !(info->invflags & ~info->flags);
 167 }
 168
 169
 170 static struct xt_match dccp_match =
 171 {
 172         .name           = "dccp",
 173         .match          = &match,
 174         .checkentry     = &checkentry,
 175         .me             = THIS_MODULE,
 176 };
 177 static struct xt_match dccp6_match =
 178 {
 179         .name           = "dccp",
 180         .match          = &match,
 181         .checkentry     = &checkentry6,
 182         .me             = THIS_MODULE,
 183 };
 184
 185
 186 static int __init init(void)
 187 {
 188         int ret;
 189
 190         /* doff is 8 bits, so the maximum option size is (4*256).  Don't put
 191          * this in BSS since DaveM is worried about locked TLB's for kernel
 192          * BSS. */
 193         dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
 194         if (!dccp_optbuf)
 195                 return -ENOMEM;
 196         ret = xt_register_match(AF_INET, &dccp_match);
 197         if (ret)
 198                 goto out_kfree;
 199         ret = xt_register_match(AF_INET6, &dccp6_match);
 200         if (ret)
 201                 goto out_unreg;
 202
 203         return ret;
 204
 205 out_unreg:
 206         xt_unregister_match(AF_INET, &dccp_match);
 207 out_kfree:
 208         kfree(dccp_optbuf);
 209
 210         return ret;
 211 }
 212
 213 static void __exit fini(void)
 214 {
 215         xt_unregister_match(AF_INET6, &dccp6_match);
 216         xt_unregister_match(AF_INET, &dccp_match);
 217         kfree(dccp_optbuf);
 218 }
 219
 220 module_init(init);
 221 module_exit(fini);