net/netfilter/xt_sctp.c

   1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   2 #include <linux/module.h>
   3 #include <linux/skbuff.h>
   4 #include <net/ip.h>
   5 #include <net/ipv6.h>
   6 #include <linux/sctp.h>
   7
   8 #include <linux/netfilter/x_tables.h>
   9 #include <linux/netfilter/xt_sctp.h>
  10 #include <linux/netfilter_ipv4/ip_tables.h>
  11 #include <linux/netfilter_ipv6/ip6_tables.h>
  12
  13 MODULE_LICENSE("GPL");
  14 MODULE_AUTHOR("Kiran Kumar Immidi");
  15 MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
  16 MODULE_ALIAS("ipt_sctp");
  17 MODULE_ALIAS("ip6t_sctp");
  18
  19 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
  20                                               || (!!((invflag) & (option)) ^ (cond)))
  21
  22 static bool
  23 match_flags(const struct xt_sctp_flag_info *flag_info,
  24             const int flag_count,
  25             u_int8_t chunktype,
  26             u_int8_t chunkflags)
  27 {
  28         int i;
  29
  30         for (i = 0; i < flag_count; i++)
  31                 if (flag_info[i].chunktype == chunktype)
  32                         return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
  33
  34         return true;
  35 }
  36
  37 static inline bool
  38 match_packet(const struct sk_buff *skb,
  39              unsigned int offset,
  40              const struct xt_sctp_info *info,
  41              bool *hotdrop)
  42 {
  43         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
  44         const sctp_chunkhdr_t *sch;
  45         sctp_chunkhdr_t _sch;
  46         int chunk_match_type = info->chunk_match_type;
  47         const struct xt_sctp_flag_info *flag_info = info->flag_info;
  48         int flag_count = info->flag_count;
  49
  50 #ifdef DEBUG
  51         int i = 0;
  52 #endif
  53
  54         if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
  55                 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
  56
  57         do {
  58                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  59                 if (sch == NULL || sch->length == 0) {
  60                         pr_debug("Dropping invalid SCTP packet.\n");
  61                         *hotdrop = true;
  62                         return false;
  63                 }
  64 #ifdef DEBUG
  65                 pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d"
  66                          "\tflags: %x\n",
  67                          ++i, offset, sch->type, htons(sch->length),
  68                          sch->flags);
  69 #endif
  70                 offset += (ntohs(sch->length) + 3) & ~3;
  71
  72                 pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset);
  73
  74                 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
  75                         switch (chunk_match_type) {
  76                         case SCTP_CHUNK_MATCH_ANY:
  77                                 if (match_flags(flag_info, flag_count,
  78                                         sch->type, sch->flags)) {
  79                                         return true;
  80                                 }
  81                                 break;
  82
  83                         case SCTP_CHUNK_MATCH_ALL:
  84                                 if (match_flags(flag_info, flag_count,
  85                                     sch->type, sch->flags))
  86                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
  87                                 break;
  88
  89                         case SCTP_CHUNK_MATCH_ONLY:
  90                                 if (!match_flags(flag_info, flag_count,
  91                                     sch->type, sch->flags))
  92                                         return false;
  93                                 break;
  94                         }
  95                 } else {
  96                         switch (chunk_match_type) {
  97                         case SCTP_CHUNK_MATCH_ONLY:
  98                                 return false;
  99                         }
 100                 }
 101         } while (offset < skb->len);
 102
 103         switch (chunk_match_type) {
 104         case SCTP_CHUNK_MATCH_ALL:
 105                 return SCTP_CHUNKMAP_IS_CLEAR(chunkmapcopy);
 106         case SCTP_CHUNK_MATCH_ANY:
 107                 return false;
 108         case SCTP_CHUNK_MATCH_ONLY:
 109                 return true;
 110         }
 111
 112         /* This will never be reached, but required to stop compiler whine */
 113         return false;
 114 }
 115
 116 static bool
 117 sctp_mt(const struct sk_buff *skb, struct xt_action_param *par)
 118 {
 119         const struct xt_sctp_info *info = par->matchinfo;
 120         const sctp_sctphdr_t *sh;
 121         sctp_sctphdr_t _sh;
 122
 123         if (par->fragoff != 0) {
 124                 pr_debug("Dropping non-first fragment.. FIXME\n");
 125                 return false;
 126         }
 127
 128         sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
 129         if (sh == NULL) {
 130                 pr_debug("Dropping evil TCP offset=0 tinygram.\n");
 131                 par->hotdrop = true;
 132                 return false;
 133         }
 134         pr_debug("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 135
 136         return  SCCHECK(ntohs(sh->source) >= info->spts[0]
 137                         && ntohs(sh->source) <= info->spts[1],
 138                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 139                 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
 140                         && ntohs(sh->dest) <= info->dpts[1],
 141                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 142                 && SCCHECK(match_packet(skb, par->thoff + sizeof(sctp_sctphdr_t),
 143                                         info, &par->hotdrop),
 144                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 145 }
 146
 147 static int sctp_mt_check(const struct xt_mtchk_param *par)
 148 {
 149         const struct xt_sctp_info *info = par->matchinfo;
 150
 151         if (info->flags & ~XT_SCTP_VALID_FLAGS)
 152                 return -EINVAL;
 153         if (info->invflags & ~XT_SCTP_VALID_FLAGS)
 154                 return -EINVAL;
 155         if (info->invflags & ~info->flags)
 156                 return -EINVAL;
 157         if (!(info->flags & XT_SCTP_CHUNK_TYPES))
 158                 return 0;
 159         if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL |
 160             SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY))
 161                 return 0;
 162         return -EINVAL;
 163 }
 164
 165 static struct xt_match sctp_mt_reg[] __read_mostly = {
 166         {
 167                 .name           = "sctp",
 168                 .family         = NFPROTO_IPV4,
 169                 .checkentry     = sctp_mt_check,
 170                 .match          = sctp_mt,
 171                 .matchsize      = sizeof(struct xt_sctp_info),
 172                 .proto          = IPPROTO_SCTP,
 173                 .me             = THIS_MODULE
 174         },
 175         {
 176                 .name           = "sctp",
 177                 .family         = NFPROTO_IPV6,
 178                 .checkentry     = sctp_mt_check,
 179                 .match          = sctp_mt,
 180                 .matchsize      = sizeof(struct xt_sctp_info),
 181                 .proto          = IPPROTO_SCTP,
 182                 .me             = THIS_MODULE
 183         },
 184 };
 185
 186 static int __init sctp_mt_init(void)
 187 {
 188         return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
 189 }
 190
 191 static void __exit sctp_mt_exit(void)
 192 {
 193         xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
 194 }
 195
 196 module_init(sctp_mt_init);
 197 module_exit(sctp_mt_exit);