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 += (ntohs(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 struct xt_match *match,
 127       const void *matchinfo,
 128       int offset,
 129       unsigned int protoff,
 130       int *hotdrop)
 131 {
 132         const struct xt_sctp_info *info = matchinfo;
 133         sctp_sctphdr_t _sh, *sh;
 134
 135         if (offset) {
 136                 duprintf("Dropping non-first fragment.. FIXME\n");
 137                 return 0;
 138         }
 139
 140         sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh);
 141         if (sh == NULL) {
 142                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
 143                 *hotdrop = 1;
 144                 return 0;
 145         }
 146         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 147
 148         return  SCCHECK(((ntohs(sh->source) >= info->spts[0])
 149                         && (ntohs(sh->source) <= info->spts[1])),
 150                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 151                 && SCCHECK(((ntohs(sh->dest) >= info->dpts[0])
 152                         && (ntohs(sh->dest) <= info->dpts[1])),
 153                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 154                 && SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t),
 155                                         info->chunkmap, info->chunk_match_type,
 156                                         info->flag_info, info->flag_count,
 157                                         hotdrop),
 158                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 159 }
 160
 161 static int
 162 checkentry(const char *tablename,
 163            const void *inf,
 164            const struct xt_match *match,
 165            void *matchinfo,
 166            unsigned int hook_mask)
 167 {
 168         const struct xt_sctp_info *info = matchinfo;
 169
 170         return !(info->flags & ~XT_SCTP_VALID_FLAGS)
 171                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
 172                 && !(info->invflags & ~info->flags)
 173                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
 174                         (info->chunk_match_type &
 175                                 (SCTP_CHUNK_MATCH_ALL
 176                                 | SCTP_CHUNK_MATCH_ANY
 177                                 | SCTP_CHUNK_MATCH_ONLY)));
 178 }
 179
 180 static struct xt_match xt_sctp_match[] = {
 181         {
 182                 .name           = "sctp",
 183                 .family         = AF_INET,
 184                 .checkentry     = checkentry,
 185                 .match          = match,
 186                 .matchsize      = sizeof(struct xt_sctp_info),
 187                 .proto          = IPPROTO_SCTP,
 188                 .me             = THIS_MODULE
 189         },
 190         {
 191                 .name           = "sctp",
 192                 .family         = AF_INET6,
 193                 .checkentry     = checkentry,
 194                 .match          = match,
 195                 .matchsize      = sizeof(struct xt_sctp_info),
 196                 .proto          = IPPROTO_SCTP,
 197                 .me             = THIS_MODULE
 198         },
 199 };
 200
 201 static int __init xt_sctp_init(void)
 202 {
 203         return xt_register_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
 204 }
 205
 206 static void __exit xt_sctp_fini(void)
 207 {
 208         xt_unregister_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match));
 209 }
 210
 211 module_init(xt_sctp_init);
 212 module_exit(xt_sctp_fini);