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 bool
  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         return true;
  39 }
  40
  41 static inline bool
  42 match_packet(const struct sk_buff *skb,
  43              unsigned int offset,
  44              const u_int32_t *chunkmap,
  45              int chunk_match_type,
  46              const struct xt_sctp_flag_info *flag_info,
  47              const int flag_count,
  48              bool *hotdrop)
  49 {
  50         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
  51         sctp_chunkhdr_t _sch, *sch;
  52
  53 #ifdef DEBUG_SCTP
  54         int i = 0;
  55 #endif
  56
  57         if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
  58                 SCTP_CHUNKMAP_COPY(chunkmapcopy, chunkmap);
  59
  60         do {
  61                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  62                 if (sch == NULL || sch->length == 0) {
  63                         duprintf("Dropping invalid SCTP packet.\n");
  64                         *hotdrop = true;
  65                         return false;
  66                 }
  67
  68                 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
  69                                 ++i, offset, sch->type, htons(sch->length), sch->flags);
  70
  71                 offset += (ntohs(sch->length) + 3) & ~3;
  72
  73                 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
  74
  75                 if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) {
  76                         switch (chunk_match_type) {
  77                         case SCTP_CHUNK_MATCH_ANY:
  78                                 if (match_flags(flag_info, flag_count,
  79                                         sch->type, sch->flags)) {
  80                                         return true;
  81                                 }
  82                                 break;
  83
  84                         case SCTP_CHUNK_MATCH_ALL:
  85                                 if (match_flags(flag_info, flag_count,
  86                                     sch->type, sch->flags))
  87                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
  88                                 break;
  89
  90                         case SCTP_CHUNK_MATCH_ONLY:
  91                                 if (!match_flags(flag_info, flag_count,
  92                                     sch->type, sch->flags))
  93                                         return false;
  94                                 break;
  95                         }
  96                 } else {
  97                         switch (chunk_match_type) {
  98                         case SCTP_CHUNK_MATCH_ONLY:
  99                                 return false;
 100                         }
 101                 }
 102         } while (offset < skb->len);
 103
 104         switch (chunk_match_type) {
 105         case SCTP_CHUNK_MATCH_ALL:
 106                 return SCTP_CHUNKMAP_IS_CLEAR(chunkmap);
 107         case SCTP_CHUNK_MATCH_ANY:
 108                 return false;
 109         case SCTP_CHUNK_MATCH_ONLY:
 110                 return true;
 111         }
 112
 113         /* This will never be reached, but required to stop compiler whine */
 114         return false;
 115 }
 116
 117 static bool
 118 match(const struct sk_buff *skb,
 119       const struct net_device *in,
 120       const struct net_device *out,
 121       const struct xt_match *match,
 122       const void *matchinfo,
 123       int offset,
 124       unsigned int protoff,
 125       bool *hotdrop)
 126 {
 127         const struct xt_sctp_info *info = matchinfo;
 128         sctp_sctphdr_t _sh, *sh;
 129
 130         if (offset) {
 131                 duprintf("Dropping non-first fragment.. FIXME\n");
 132                 return false;
 133         }
 134
 135         sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
 136         if (sh == NULL) {
 137                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
 138                 *hotdrop = true;
 139                 return false;
 140         }
 141         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 142
 143         return  SCCHECK(ntohs(sh->source) >= info->spts[0]
 144                         && ntohs(sh->source) <= info->spts[1],
 145                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 146                 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
 147                         && ntohs(sh->dest) <= info->dpts[1],
 148                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 149                 && SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t),
 150                                         info->chunkmap, info->chunk_match_type,
 151                                         info->flag_info, info->flag_count,
 152                                         hotdrop),
 153                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 154 }
 155
 156 static bool
 157 checkentry(const char *tablename,
 158            const void *inf,
 159            const struct xt_match *match,
 160            void *matchinfo,
 161            unsigned int hook_mask)
 162 {
 163         const struct xt_sctp_info *info = matchinfo;
 164
 165         return !(info->flags & ~XT_SCTP_VALID_FLAGS)
 166                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
 167                 && !(info->invflags & ~info->flags)
 168                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
 169                         (info->chunk_match_type &
 170                                 (SCTP_CHUNK_MATCH_ALL
 171                                 | SCTP_CHUNK_MATCH_ANY
 172                                 | SCTP_CHUNK_MATCH_ONLY)));
 173 }
 174
 175 static struct xt_match xt_sctp_match[] __read_mostly = {
 176         {
 177                 .name           = "sctp",
 178                 .family         = AF_INET,
 179                 .checkentry     = checkentry,
 180                 .match          = match,
 181                 .matchsize      = sizeof(struct xt_sctp_info),
 182                 .proto          = IPPROTO_SCTP,
 183                 .me             = THIS_MODULE
 184         },
 185         {
 186                 .name           = "sctp",
 187                 .family         = AF_INET6,
 188                 .checkentry     = checkentry,
 189                 .match          = match,
 190                 .matchsize      = sizeof(struct xt_sctp_info),
 191                 .proto          = IPPROTO_SCTP,
 192                 .me             = THIS_MODULE
 193         },
 194 };
 195
 196 static int __init xt_sctp_init(void)
 197 {
 198         return xt_register_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
 199 }
 200
 201 static void __exit xt_sctp_fini(void)
 202 {
 203         xt_unregister_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
 204 }
 205
 206 module_init(xt_sctp_init);
 207 module_exit(xt_sctp_fini);