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 <net/sctp/sctp.h>
   7 #include <linux/sctp.h>
   8
   9 #include <linux/netfilter/x_tables.h>
  10 #include <linux/netfilter/xt_sctp.h>
  11 #include <linux/netfilter_ipv4/ip_tables.h>
  12 #include <linux/netfilter_ipv6/ip6_tables.h>
  13
  14 MODULE_LICENSE("GPL");
  15 MODULE_AUTHOR("Kiran Kumar Immidi");
  16 MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
  17 MODULE_ALIAS("ipt_sctp");
  18 MODULE_ALIAS("ip6t_sctp");
  19
  20 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
  21                                               || (!!((invflag) & (option)) ^ (cond)))
  22
  23 static bool
  24 match_flags(const struct xt_sctp_flag_info *flag_info,
  25             const int flag_count,
  26             u_int8_t chunktype,
  27             u_int8_t chunkflags)
  28 {
  29         int i;
  30
  31         for (i = 0; i < flag_count; i++)
  32                 if (flag_info[i].chunktype == chunktype)
  33                         return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
  34
  35         return true;
  36 }
  37
  38 static inline bool
  39 match_packet(const struct sk_buff *skb,
  40              unsigned int offset,
  41              const struct xt_sctp_info *info,
  42              bool *hotdrop)
  43 {
  44         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
  45         const sctp_chunkhdr_t *sch;
  46         sctp_chunkhdr_t _sch;
  47         int chunk_match_type = info->chunk_match_type;
  48         const struct xt_sctp_flag_info *flag_info = info->flag_info;
  49         int flag_count = info->flag_count;
  50
  51 #ifdef DEBUG
  52         int i = 0;
  53 #endif
  54
  55         if (chunk_match_type == SCTP_CHUNK_MATCH_ALL)
  56                 SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap);
  57
  58         do {
  59                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  60                 if (sch == NULL || sch->length == 0) {
  61                         pr_debug("Dropping invalid SCTP packet.\n");
  62                         *hotdrop = true;
  63                         return false;
  64                 }
  65 #ifdef DEBUG
  66                 pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d"
  67                          "\tflags: %x\n",
  68                          ++i, offset, sch->type, htons(sch->length),
  69                          sch->flags);
  70 #endif
  71                 offset += SCTP_PAD4(ntohs(sch->length));
  72
  73                 pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset);
  74
  75                 if (SCTP_CHUNKMAP_IS_SET(info->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(chunkmapcopy);
 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 sctp_mt(const struct sk_buff *skb, struct xt_action_param *par)
 119 {
 120         const struct xt_sctp_info *info = par->matchinfo;
 121         const sctp_sctphdr_t *sh;
 122         sctp_sctphdr_t _sh;
 123
 124         if (par->fragoff != 0) {
 125                 pr_debug("Dropping non-first fragment.. FIXME\n");
 126                 return false;
 127         }
 128
 129         sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
 130         if (sh == NULL) {
 131                 pr_debug("Dropping evil TCP offset=0 tinygram.\n");
 132                 par->hotdrop = true;
 133                 return false;
 134         }
 135         pr_debug("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 136
 137         return  SCCHECK(ntohs(sh->source) >= info->spts[0]
 138                         && ntohs(sh->source) <= info->spts[1],
 139                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 140                 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
 141                         && ntohs(sh->dest) <= info->dpts[1],
 142                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 143                 && SCCHECK(match_packet(skb, par->thoff + sizeof(sctp_sctphdr_t),
 144                                         info, &par->hotdrop),
 145                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 146 }
 147
 148 static int sctp_mt_check(const struct xt_mtchk_param *par)
 149 {
 150         const struct xt_sctp_info *info = par->matchinfo;
 151
 152         if (info->flags & ~XT_SCTP_VALID_FLAGS)
 153                 return -EINVAL;
 154         if (info->invflags & ~XT_SCTP_VALID_FLAGS)
 155                 return -EINVAL;
 156         if (info->invflags & ~info->flags)
 157                 return -EINVAL;
 158         if (!(info->flags & XT_SCTP_CHUNK_TYPES))
 159                 return 0;
 160         if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL |
 161             SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY))
 162                 return 0;
 163         return -EINVAL;
 164 }
 165
 166 static struct xt_match sctp_mt_reg[] __read_mostly = {
 167         {
 168                 .name           = "sctp",
 169                 .family         = NFPROTO_IPV4,
 170                 .checkentry     = sctp_mt_check,
 171                 .match          = sctp_mt,
 172                 .matchsize      = sizeof(struct xt_sctp_info),
 173                 .proto          = IPPROTO_SCTP,
 174                 .me             = THIS_MODULE
 175         },
 176         {
 177                 .name           = "sctp",
 178                 .family         = NFPROTO_IPV6,
 179                 .checkentry     = sctp_mt_check,
 180                 .match          = sctp_mt,
 181                 .matchsize      = sizeof(struct xt_sctp_info),
 182                 .proto          = IPPROTO_SCTP,
 183                 .me             = THIS_MODULE
 184         },
 185 };
 186
 187 static int __init sctp_mt_init(void)
 188 {
 189         return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
 190 }
 191
 192 static void __exit sctp_mt_exit(void)
 193 {
 194         xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
 195 }
 196
 197 module_init(sctp_mt_init);
 198 module_exit(sctp_mt_exit);