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 MODULE_ALIAS("ip6t_sctp");
  17
  18 #ifdef DEBUG_SCTP
  19 #define duprintf(format, args...) printk(format , ## args)
  20 #else
  21 #define duprintf(format, args...)
  22 #endif
  23
  24 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
  25                                               || (!!((invflag) & (option)) ^ (cond)))
  26
  27 static bool
  28 match_flags(const struct xt_sctp_flag_info *flag_info,
  29             const int flag_count,
  30             u_int8_t chunktype,
  31             u_int8_t chunkflags)
  32 {
  33         int i;
  34
  35         for (i = 0; i < flag_count; i++)
  36                 if (flag_info[i].chunktype == chunktype)
  37                         return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
  38
  39         return true;
  40 }
  41
  42 static inline bool
  43 match_packet(const struct sk_buff *skb,
  44              unsigned int offset,
  45              const struct xt_sctp_info *info,
  46              bool *hotdrop)
  47 {
  48         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
  49         sctp_chunkhdr_t _sch, *sch;
  50         int chunk_match_type = info->chunk_match_type;
  51         const struct xt_sctp_flag_info *flag_info = info->flag_info;
  52         int flag_count = info->flag_count;
  53
  54 #ifdef DEBUG_SCTP
  55         int i = 0;
  56 #endif
  57
  58         if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
  59                 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
  60
  61         do {
  62                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  63                 if (sch == NULL || sch->length == 0) {
  64                         duprintf("Dropping invalid SCTP packet.\n");
  65                         *hotdrop = true;
  66                         return false;
  67                 }
  68
  69                 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
  70                                 ++i, offset, sch->type, htons(sch->length), sch->flags);
  71
  72                 offset += (ntohs(sch->length) + 3) & ~3;
  73
  74                 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
  75
  76                 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
  77                         switch (chunk_match_type) {
  78                         case SCTP_CHUNK_MATCH_ANY:
  79                                 if (match_flags(flag_info, flag_count,
  80                                         sch->type, sch->flags)) {
  81                                         return true;
  82                                 }
  83                                 break;
  84
  85                         case SCTP_CHUNK_MATCH_ALL:
  86                                 if (match_flags(flag_info, flag_count,
  87                                     sch->type, sch->flags))
  88                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
  89                                 break;
  90
  91                         case SCTP_CHUNK_MATCH_ONLY:
  92                                 if (!match_flags(flag_info, flag_count,
  93                                     sch->type, sch->flags))
  94                                         return false;
  95                                 break;
  96                         }
  97                 } else {
  98                         switch (chunk_match_type) {
  99                         case SCTP_CHUNK_MATCH_ONLY:
 100                                 return false;
 101                         }
 102                 }
 103         } while (offset < skb->len);
 104
 105         switch (chunk_match_type) {
 106         case SCTP_CHUNK_MATCH_ALL:
 107                 return SCTP_CHUNKMAP_IS_CLEAR(info->chunkmap);
 108         case SCTP_CHUNK_MATCH_ANY:
 109                 return false;
 110         case SCTP_CHUNK_MATCH_ONLY:
 111                 return true;
 112         }
 113
 114         /* This will never be reached, but required to stop compiler whine */
 115         return false;
 116 }
 117
 118 static bool
 119 match(const struct sk_buff *skb,
 120       const struct net_device *in,
 121       const struct net_device *out,
 122       const struct xt_match *match,
 123       const void *matchinfo,
 124       int offset,
 125       unsigned int protoff,
 126       bool *hotdrop)
 127 {
 128         const struct xt_sctp_info *info = matchinfo;
 129         sctp_sctphdr_t _sh, *sh;
 130
 131         if (offset) {
 132                 duprintf("Dropping non-first fragment.. FIXME\n");
 133                 return false;
 134         }
 135
 136         sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
 137         if (sh == NULL) {
 138                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
 139                 *hotdrop = true;
 140                 return false;
 141         }
 142         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 143
 144         return  SCCHECK(ntohs(sh->source) >= info->spts[0]
 145                         && ntohs(sh->source) <= info->spts[1],
 146                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 147                 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
 148                         && ntohs(sh->dest) <= info->dpts[1],
 149                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 150                 && SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t),
 151                                         info, hotdrop),
 152                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 153 }
 154
 155 static bool
 156 checkentry(const char *tablename,
 157            const void *inf,
 158            const struct xt_match *match,
 159            void *matchinfo,
 160            unsigned int hook_mask)
 161 {
 162         const struct xt_sctp_info *info = matchinfo;
 163
 164         return !(info->flags & ~XT_SCTP_VALID_FLAGS)
 165                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
 166                 && !(info->invflags & ~info->flags)
 167                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
 168                         (info->chunk_match_type &
 169                                 (SCTP_CHUNK_MATCH_ALL
 170                                 | SCTP_CHUNK_MATCH_ANY
 171                                 | SCTP_CHUNK_MATCH_ONLY)));
 172 }
 173
 174 static struct xt_match xt_sctp_match[] __read_mostly = {
 175         {
 176                 .name           = "sctp",
 177                 .family         = AF_INET,
 178                 .checkentry     = checkentry,
 179                 .match          = match,
 180                 .matchsize      = sizeof(struct xt_sctp_info),
 181                 .proto          = IPPROTO_SCTP,
 182                 .me             = THIS_MODULE
 183         },
 184         {
 185                 .name           = "sctp",
 186                 .family         = AF_INET6,
 187                 .checkentry     = checkentry,
 188                 .match          = match,
 189                 .matchsize      = sizeof(struct xt_sctp_info),
 190                 .proto          = IPPROTO_SCTP,
 191                 .me             = THIS_MODULE
 192         },
 193 };
 194
 195 static int __init xt_sctp_init(void)
 196 {
 197         return xt_register_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
 198 }
 199
 200 static void __exit xt_sctp_fini(void)
 201 {
 202         xt_unregister_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
 203 }
 204
 205 module_init(xt_sctp_init);
 206 module_exit(xt_sctp_fini);