net/ipv4/netfilter/ipt_sctp.c

   1 #include <linux/module.h>
   2 #include <linux/skbuff.h>
   3 #include <net/ip.h>
   4 #include <linux/sctp.h>
   5
   6 #include <linux/netfilter_ipv4/ip_tables.h>
   7 #include <linux/netfilter_ipv4/ipt_sctp.h>
   8
   9 #ifdef DEBUG_SCTP
  10 #define duprintf(format, args...) printk(format , ## args)
  11 #else
  12 #define duprintf(format, args...)
  13 #endif
  14
  15 #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
  16                                               || (!!((invflag) & (option)) ^ (cond)))
  17
  18 static int
  19 match_flags(const struct ipt_sctp_flag_info *flag_info,
  20             const int flag_count,
  21             u_int8_t chunktype,
  22             u_int8_t chunkflags)
  23 {
  24         int i;
  25
  26         for (i = 0; i < flag_count; i++) {
  27                 if (flag_info[i].chunktype == chunktype) {
  28                         return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
  29                 }
  30         }
  31
  32         return 1;
  33 }
  34
  35 static int
  36 match_packet(const struct sk_buff *skb,
  37              const u_int32_t *chunkmap,
  38              int chunk_match_type,
  39              const struct ipt_sctp_flag_info *flag_info,
  40              const int flag_count,
  41              int *hotdrop)
  42 {
  43         int offset;
  44         u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
  45         sctp_chunkhdr_t _sch, *sch;
  46
  47 #ifdef DEBUG_SCTP
  48         int i = 0;
  49 #endif
  50
  51         if (chunk_match_type == SCTP_CHUNK_MATCH_ALL) {
  52                 SCTP_CHUNKMAP_COPY(chunkmapcopy, chunkmap);
  53         }
  54
  55         offset = skb->nh.iph->ihl * 4 + sizeof (sctp_sctphdr_t);
  56         do {
  57                 sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
  58                 if (sch == NULL) {
  59                         duprintf("Dropping invalid SCTP packet.\n");
  60                         *hotdrop = 1;
  61                         return 0;
  62                 }
  63
  64                 duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
  65                                 ++i, offset, sch->type, htons(sch->length), sch->flags);
  66
  67                 offset += (htons(sch->length) + 3) & ~3;
  68
  69                 duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
  70
  71                 if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) {
  72                         switch (chunk_match_type) {
  73                         case SCTP_CHUNK_MATCH_ANY:
  74                                 if (match_flags(flag_info, flag_count,
  75                                         sch->type, sch->flags)) {
  76                                         return 1;
  77                                 }
  78                                 break;
  79
  80                         case SCTP_CHUNK_MATCH_ALL:
  81                                 if (match_flags(flag_info, flag_count,
  82                                         sch->type, sch->flags)) {
  83                                         SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
  84                                 }
  85                                 break;
  86
  87                         case SCTP_CHUNK_MATCH_ONLY:
  88                                 if (!match_flags(flag_info, flag_count,
  89                                         sch->type, sch->flags)) {
  90                                         return 0;
  91                                 }
  92                                 break;
  93                         }
  94                 } else {
  95                         switch (chunk_match_type) {
  96                         case SCTP_CHUNK_MATCH_ONLY:
  97                                 return 0;
  98                         }
  99                 }
 100         } while (offset < skb->len);
 101
 102         switch (chunk_match_type) {
 103         case SCTP_CHUNK_MATCH_ALL:
 104                 return SCTP_CHUNKMAP_IS_CLEAR(chunkmap);
 105         case SCTP_CHUNK_MATCH_ANY:
 106                 return 0;
 107         case SCTP_CHUNK_MATCH_ONLY:
 108                 return 1;
 109         }
 110
 111         /* This will never be reached, but required to stop compiler whine */
 112         return 0;
 113 }
 114
 115 static int
 116 match(const struct sk_buff *skb,
 117       const struct net_device *in,
 118       const struct net_device *out,
 119       const void *matchinfo,
 120       int offset,
 121       int *hotdrop)
 122 {
 123         const struct ipt_sctp_info *info;
 124         sctp_sctphdr_t _sh, *sh;
 125
 126         info = (const struct ipt_sctp_info *)matchinfo;
 127
 128         if (offset) {
 129                 duprintf("Dropping non-first fragment.. FIXME\n");
 130                 return 0;
 131         }
 132
 133         sh = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_sh), &_sh);
 134         if (sh == NULL) {
 135                 duprintf("Dropping evil TCP offset=0 tinygram.\n");
 136                 *hotdrop = 1;
 137                 return 0;
 138         }
 139         duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
 140
 141         return  SCCHECK(((ntohs(sh->source) >= info->spts[0])
 142                         && (ntohs(sh->source) <= info->spts[1])),
 143                         IPT_SCTP_SRC_PORTS, info->flags, info->invflags)
 144                 && SCCHECK(((ntohs(sh->dest) >= info->dpts[0])
 145                         && (ntohs(sh->dest) <= info->dpts[1])),
 146                         IPT_SCTP_DEST_PORTS, info->flags, info->invflags)
 147                 && SCCHECK(match_packet(skb, info->chunkmap, info->chunk_match_type,
 148                                         info->flag_info, info->flag_count,
 149                                         hotdrop),
 150                            IPT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
 151 }
 152
 153 static int
 154 checkentry(const char *tablename,
 155            const struct ipt_ip *ip,
 156            void *matchinfo,
 157            unsigned int matchsize,
 158            unsigned int hook_mask)
 159 {
 160         const struct ipt_sctp_info *info;
 161
 162         info = (const struct ipt_sctp_info *)matchinfo;
 163
 164         return ip->proto == IPPROTO_SCTP
 165                 && !(ip->invflags & IPT_INV_PROTO)
 166                 && matchsize == IPT_ALIGN(sizeof(struct ipt_sctp_info))
 167                 && !(info->flags & ~IPT_SCTP_VALID_FLAGS)
 168                 && !(info->invflags & ~IPT_SCTP_VALID_FLAGS)
 169                 && !(info->invflags & ~info->flags)
 170                 && ((!(info->flags & IPT_SCTP_CHUNK_TYPES)) ||
 171                         (info->chunk_match_type &
 172                                 (SCTP_CHUNK_MATCH_ALL
 173                                 | SCTP_CHUNK_MATCH_ANY
 174                                 | SCTP_CHUNK_MATCH_ONLY)));
 175 }
 176
 177 static struct ipt_match sctp_match =
 178 {
 179         .list = { NULL, NULL},
 180         .name = "sctp",
 181         .match = &match,
 182         .checkentry = &checkentry,
 183         .destroy = NULL,
 184         .me = THIS_MODULE
 185 };
 186
 187 static int __init init(void)
 188 {
 189         return ipt_register_match(&sctp_match);
 190 }
 191
 192 static void __exit fini(void)
 193 {
 194         ipt_unregister_match(&sctp_match);
 195 }
 196
 197 module_init(init);
 198 module_exit(fini);
 199
 200 MODULE_LICENSE("GPL");
 201 MODULE_AUTHOR("Kiran Kumar Immidi");
 202 MODULE_DESCRIPTION("Match for SCTP protocol packets");
 203