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("Xtables: SCTP protocol packet match");
  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         const sctp_chunkhdr_t *sch;
  50         sctp_chunkhdr_t _sch;
  51         int chunk_match_type = info->chunk_match_type;
  52         const struct xt_sctp_flag_info *flag_info = info->flag_info;
  53         int flag_count = info->flag_count;
  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, info->chunkmap);
  61
  62         do {
  63                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  64                 if (sch == NULL || sch->length == 0) {
  65                         duprintf("Dropping invalid SCTP packet.\n");
  66                         *hotdrop = true;
  67                         return false;
  68                 }
  69
  70                 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
  71                                 ++i, offset, sch->type, htons(sch->length), sch->flags);
  72
  73                 offset += (ntohs(sch->length) + 3) & ~3;
  74
  75                 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
  76
  77                 if (SCTP_CHUNKMAP_IS_SET(info->chunkmap, sch->type)) {
  78                         switch (chunk_match_type) {
  79                         case SCTP_CHUNK_MATCH_ANY:
  80                                 if (match_flags(flag_info, flag_count,
  81                                         sch->type, sch->flags)) {
  82                                         return true;
  83                                 }
  84                                 break;
  85
  86                         case SCTP_CHUNK_MATCH_ALL:
  87                                 if (match_flags(flag_info, flag_count,
  88                                     sch->type, sch->flags))
  89                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
  90                                 break;
  91
  92                         case SCTP_CHUNK_MATCH_ONLY:
  93                                 if (!match_flags(flag_info, flag_count,
  94                                     sch->type, sch->flags))
  95                                         return false;
  96                                 break;
  97                         }
  98                 } else {
  99                         switch (chunk_match_type) {
 100                         case SCTP_CHUNK_MATCH_ONLY:
 101                                 return false;
 102                         }
 103                 }
 104         } while (offset < skb->len);
 105
 106         switch (chunk_match_type) {
 107         case SCTP_CHUNK_MATCH_ALL:
 108                 return SCTP_CHUNKMAP_IS_CLEAR(info->chunkmap);
 109         case SCTP_CHUNK_MATCH_ANY:
 110                 return false;
 111         case SCTP_CHUNK_MATCH_ONLY:
 112                 return true;
 113         }
 114
 115         /* This will never be reached, but required to stop compiler whine */
 116         return false;
 117 }
 118
 119 static bool
 120 sctp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
 121 {
 122         const struct xt_sctp_info *info = par->matchinfo;
 123         const sctp_sctphdr_t *sh;
 124         sctp_sctphdr_t _sh;
 125
 126         if (par->fragoff != 0) {
 127                 duprintf("Dropping non-first fragment.. FIXME\n");
 128                 return false;
 129         }
 130
 131         sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
 132         if (sh == NULL) {
 133                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
 134                 *par->hotdrop = true;
 135                 return false;
 136         }
 137         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 138
 139         return  SCCHECK(ntohs(sh->source) >= info->spts[0]
 140                         && ntohs(sh->source) <= info->spts[1],
 141                         XT_SCTP_SRC_PORTS, info->flags, info->invflags)
 142                 && SCCHECK(ntohs(sh->dest) >= info->dpts[0]
 143                         && ntohs(sh->dest) <= info->dpts[1],
 144                         XT_SCTP_DEST_PORTS, info->flags, info->invflags)
 145                 && SCCHECK(match_packet(skb, par->thoff + sizeof(sctp_sctphdr_t),
 146                                         info, par->hotdrop),
 147                            XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 148 }
 149
 150 static bool sctp_mt_check(const struct xt_mtchk_param *par)
 151 {
 152         const struct xt_sctp_info *info = par->matchinfo;
 153
 154         return !(info->flags & ~XT_SCTP_VALID_FLAGS)
 155                 && !(info->invflags & ~XT_SCTP_VALID_FLAGS)
 156                 && !(info->invflags & ~info->flags)
 157                 && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) ||
 158                         (info->chunk_match_type &
 159                                 (SCTP_CHUNK_MATCH_ALL
 160                                 | SCTP_CHUNK_MATCH_ANY
 161                                 | SCTP_CHUNK_MATCH_ONLY)));
 162 }
 163
 164 static struct xt_match sctp_mt_reg[] __read_mostly = {
 165         {
 166                 .name           = "sctp",
 167                 .family         = NFPROTO_IPV4,
 168                 .checkentry     = sctp_mt_check,
 169                 .match          = sctp_mt,
 170                 .matchsize      = sizeof(struct xt_sctp_info),
 171                 .proto          = IPPROTO_SCTP,
 172                 .me             = THIS_MODULE
 173         },
 174         {
 175                 .name           = "sctp",
 176                 .family         = NFPROTO_IPV6,
 177                 .checkentry     = sctp_mt_check,
 178                 .match          = sctp_mt,
 179                 .matchsize      = sizeof(struct xt_sctp_info),
 180                 .proto          = IPPROTO_SCTP,
 181                 .me             = THIS_MODULE
 182         },
 183 };
 184
 185 static int __init sctp_mt_init(void)
 186 {
 187         return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
 188 }
 189
 190 static void __exit sctp_mt_exit(void)
 191 {
 192         xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
 193 }
 194
 195 module_init(sctp_mt_init);
 196 module_exit(sctp_mt_exit);