net/netfilter/xt_sctp.c

   1 #include <linux/module.h>
   2 #include <linux/skbuff.h>
   3 #include <net/ip.h>
   4 #include <net/ipv6.h>
   5 #include <linux/sctp.h>
   6
   7 #include <linux/netfilter/x_tables.h>
   8 #include <linux/netfilter/xt_sctp.h>
   9 #include <linux/netfilter_ipv4/ip_tables.h>
  10 #include <linux/netfilter_ipv6/ip6_tables.h>
  11
  12 MODULE_LICENSE("GPL");
  13 MODULE_AUTHOR("Kiran Kumar Immidi");
  14 MODULE_DESCRIPTION("Match for SCTP protocol packets");
  15 MODULE_ALIAS("ipt_sctp");
  16
  17 #ifdef DEBUG_SCTP
  18 #define duprintf(format, args...) printk(format , ## args)
  19 #else
  20 #define duprintf(format, args...)
  21 #endif
  22
  23 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
  24                                               || (!!((invflag) & (option)) ^ (cond)))
  25
  26 static int
  27 match_flags(const struct xt_sctp_flag_info *flag_info,
  28             const int flag_count,
  29             u_int8_t chunktype,
  30             u_int8_t chunkflags)
  31 {
  32         int i;
  33
  34         for (i = 0; i < flag_count; i++) {
  35                 if (flag_info[i].chunktype == chunktype) {
  36                         return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
  37                 }
  38         }
  39
  40         return 1;
  41 }
  42
  43 static inline int
  44 match_packet(const struct sk_buff *skb,
  45              unsigned int offset,
  46              const u_int32_t *chunkmap,
  47              int chunk_match_type,
  48              const struct xt_sctp_flag_info *flag_info,
  49              const int flag_count,
  50              int *hotdrop)
  51 {
  52         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
  53         sctp_chunkhdr_t _sch, *sch;
  54
  55 #ifdef DEBUG_SCTP
  56         int i = 0;
  57 #endif
  58
  59         if (chunk_match_type == SCTP_CHUNK_MATCH_ALL) {
  60                 SCTP_CHUNKMAP_COPY(chunkmapcopy, chunkmap);
  61         }
  62
  63         do {
  64                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  65                 if (sch == NULL || sch->length == 0) {
  66                         duprintf("Dropping invalid SCTP packet.\n");
  67                         *hotdrop = 1;
  68                         return 0;
  69                 }
  70
  71                 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
  72                                 ++i, offset, sch->type, htons(sch->length), sch->flags);
  73
  74                 offset += (htons(sch->length) + 3) & ~3;
  75
  76                 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
  77
  78                 if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) {
  79                         switch (chunk_match_type) {
  80                         case SCTP_CHUNK_MATCH_ANY:
  81                                 if (match_flags(flag_info, flag_count,
  82                                         sch->type, sch->flags)) {
  83                                         return 1;
  84                                 }
  85                                 break;
  86
  87                         case SCTP_CHUNK_MATCH_ALL:
  88                                 if (match_flags(flag_info, flag_count,
  89                                         sch->type, sch->flags)) {
  90                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
  91                                 }
  92                                 break;
  93
  94                         case SCTP_CHUNK_MATCH_ONLY:
  95                                 if (!match_flags(flag_info, flag_count,
  96                                         sch->type, sch->flags)) {
  97                                         return 0;
  98                                 }
  99                                 break;
 100                         }
 101                 } else {
 102                         switch (chunk_match_type) {
 103                         case SCTP_CHUNK_MATCH_ONLY:
 104                                 return 0;
 105                         }
 106                 }
 107         } while (offset < skb->len);
 108
 109         switch (chunk_match_type) {
 110         case SCTP_CHUNK_MATCH_ALL:
 111                 return SCTP_CHUNKMAP_IS_CLEAR(chunkmap);
 112         case SCTP_CHUNK_MATCH_ANY:
 113                 return 0;
 114         case SCTP_CHUNK_MATCH_ONLY:
 115                 return 1;
 116         }
 117
 118         /* This will never be reached, but required to stop compiler whine */
 119         return 0;
 120 }
 121
 122 static int
 123 match(const struct sk_buff *skb,
 124       const struct net_device *in,
 125       const struct net_device *out,
 126       const void *matchinfo,
 127       int offset,
 128       unsigned int protoff,
 129       int *hotdrop)
 130 {
 131         const struct xt_sctp_info *info;
 132         sctp_sctphdr_t _sh, *sh;
 133
 134         info = (const struct xt_sctp_info *)matchinfo;
 135
 136         if (offset) {
 137                 duprintf("Dropping non-first fragment.. FIXME\n");
 138                 return 0;
 139         }
 140
 141         sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
 142         if (sh == NULL) {
 143                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
 144                 *hotdrop = 1;
 145                 return 0;
 146         }
 147         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 148
 149         return  SCCHECK(((ntohs(sh->source) >= info->spts[0])
 150                         && (ntohs(sh->source) <= info->spts[1])),
 151                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 152                 && SCCHECK(((ntohs(sh->dest) >= info->dpts[0])
 153                         && (ntohs(sh->dest) <= info->dpts[1])),
 154                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 155                 && SCCHECK(match_packet(skb, protoff,
 156                                         info->chunkmap, info->chunk_match_type,
 157                                         info->flag_info, info->flag_count,
 158                                         hotdrop),
 159                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 160 }
 161
 162 static int
 163 checkentry(const char *tablename,
 164            const void *inf,
 165            void *matchinfo,
 166            unsigned int matchsize,
 167            unsigned int hook_mask)
 168 {
 169         const struct xt_sctp_info *info;
 170         const struct ipt_ip *ip = inf;
 171
 172         info = (const struct xt_sctp_info *)matchinfo;
 173
 174         return ip->proto == IPPROTO_SCTP
 175                 && !(ip->invflags & XT_INV_PROTO)
 176                 && matchsize == XT_ALIGN(sizeof(struct xt_sctp_info))
 177                 && !(info->flags & ~XT_SCTP_VALID_FLAGS)
 178                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
 179                 && !(info->invflags & ~info->flags)
 180                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
 181                         (info->chunk_match_type &
 182                                 (SCTP_CHUNK_MATCH_ALL
 183                                 | SCTP_CHUNK_MATCH_ANY
 184                                 | SCTP_CHUNK_MATCH_ONLY)));
 185 }
 186
 187 static int
 188 checkentry6(const char *tablename,
 189            const void *inf,
 190            void *matchinfo,
 191            unsigned int matchsize,
 192            unsigned int hook_mask)
 193 {
 194         const struct xt_sctp_info *info;
 195         const struct ip6t_ip6 *ip = inf;
 196
 197         info = (const struct xt_sctp_info *)matchinfo;
 198
 199         return ip->proto == IPPROTO_SCTP
 200                 && !(ip->invflags & XT_INV_PROTO)
 201                 && matchsize == XT_ALIGN(sizeof(struct xt_sctp_info))
 202                 && !(info->flags & ~XT_SCTP_VALID_FLAGS)
 203                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
 204                 && !(info->invflags & ~info->flags)
 205                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
 206                         (info->chunk_match_type &
 207                                 (SCTP_CHUNK_MATCH_ALL
 208                                 | SCTP_CHUNK_MATCH_ANY
 209                                 | SCTP_CHUNK_MATCH_ONLY)));
 210 }
 211
 212
 213 static struct xt_match sctp_match =
 214 {
 215         .name = "sctp",
 216         .match = &match,
 217         .checkentry = &checkentry,
 218         .me = THIS_MODULE
 219 };
 220 static struct xt_match sctp6_match =
 221 {
 222         .name = "sctp",
 223         .match = &match,
 224         .checkentry = &checkentry6,
 225         .me = THIS_MODULE
 226 };
 227
 228
 229 static int __init init(void)
 230 {
 231         int ret;
 232         ret = xt_register_match(AF_INET, &sctp_match);
 233         if (ret)
 234                 return ret;
 235
 236         ret = xt_register_match(AF_INET6, &sctp6_match);
 237         if (ret)
 238                 xt_unregister_match(AF_INET, &sctp_match);
 239
 240         return ret;
 241 }
 242
 243 static void __exit fini(void)
 244 {
 245         xt_unregister_match(AF_INET6, &sctp6_match);
 246         xt_unregister_match(AF_INET, &sctp_match);
 247 }
 248
 249 module_init(init);
 250 module_exit(fini);