| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <net/ip.h> |
| #include <net/ipv6.h> |
| #include <linux/sctp.h> |
| |
| #include <linux/netfilter/x_tables.h> |
| #include <linux/netfilter/xt_sctp.h> |
| #include <linux/netfilter_ipv4/ip_tables.h> |
| #include <linux/netfilter_ipv6/ip6_tables.h> |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Kiran Kumar Immidi"); |
| MODULE_DESCRIPTION("Match for SCTP protocol packets"); |
| MODULE_ALIAS("ipt_sctp"); |
| |
| #ifdef DEBUG_SCTP |
| #define duprintf(format, args...) printk(format , ## args) |
| #else |
| #define duprintf(format, args...) |
| #endif |
| |
| #define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ |
| || (!!((invflag) & (option)) ^ (cond))) |
| |
| static bool |
| match_flags(const struct xt_sctp_flag_info *flag_info, |
| const int flag_count, |
| u_int8_t chunktype, |
| u_int8_t chunkflags) |
| { |
| int i; |
| |
| for (i = 0; i < flag_count; i++) { |
| if (flag_info[i].chunktype == chunktype) { |
| return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag; |
| } |
| } |
| |
| return true; |
| } |
| |
| static inline bool |
| match_packet(const struct sk_buff *skb, |
| unsigned int offset, |
| const u_int32_t *chunkmap, |
| int chunk_match_type, |
| const struct xt_sctp_flag_info *flag_info, |
| const int flag_count, |
| bool *hotdrop) |
| { |
| u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)]; |
| sctp_chunkhdr_t _sch, *sch; |
| |
| #ifdef DEBUG_SCTP |
| int i = 0; |
| #endif |
| |
| if (chunk_match_type == SCTP_CHUNK_MATCH_ALL) { |
| SCTP_CHUNKMAP_COPY(chunkmapcopy, chunkmap); |
| } |
| |
| do { |
| sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch); |
| if (sch == NULL || sch->length == 0) { |
| duprintf("Dropping invalid SCTP packet.\n"); |
| *hotdrop = true; |
| return false; |
| } |
| |
| duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n", |
| ++i, offset, sch->type, htons(sch->length), sch->flags); |
| |
| offset += (ntohs(sch->length) + 3) & ~3; |
| |
| duprintf("skb->len: %d\toffset: %d\n", skb->len, offset); |
| |
| if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) { |
| switch (chunk_match_type) { |
| case SCTP_CHUNK_MATCH_ANY: |
| if (match_flags(flag_info, flag_count, |
| sch->type, sch->flags)) { |
| return true; |
| } |
| break; |
| |
| case SCTP_CHUNK_MATCH_ALL: |
| if (match_flags(flag_info, flag_count, |
| sch->type, sch->flags)) { |
| SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type); |
| } |
| break; |
| |
| case SCTP_CHUNK_MATCH_ONLY: |
| if (!match_flags(flag_info, flag_count, |
| sch->type, sch->flags)) { |
| return false; |
| } |
| break; |
| } |
| } else { |
| switch (chunk_match_type) { |
| case SCTP_CHUNK_MATCH_ONLY: |
| return false; |
| } |
| } |
| } while (offset < skb->len); |
| |
| switch (chunk_match_type) { |
| case SCTP_CHUNK_MATCH_ALL: |
| return SCTP_CHUNKMAP_IS_CLEAR(chunkmap); |
| case SCTP_CHUNK_MATCH_ANY: |
| return false; |
| case SCTP_CHUNK_MATCH_ONLY: |
| return true; |
| } |
| |
| /* This will never be reached, but required to stop compiler whine */ |
| return false; |
| } |
| |
| static bool |
| match(const struct sk_buff *skb, |
| const struct net_device *in, |
| const struct net_device *out, |
| const struct xt_match *match, |
| const void *matchinfo, |
| int offset, |
| unsigned int protoff, |
| bool *hotdrop) |
| { |
| const struct xt_sctp_info *info = matchinfo; |
| sctp_sctphdr_t _sh, *sh; |
| |
| if (offset) { |
| duprintf("Dropping non-first fragment.. FIXME\n"); |
| return false; |
| } |
| |
| sh = skb_header_pointer(skb, protoff, sizeof(_sh), &_sh); |
| if (sh == NULL) { |
| duprintf("Dropping evil TCP offset=0 tinygram.\n"); |
| *hotdrop = true; |
| return false; |
| } |
| duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest)); |
| |
| return SCCHECK(((ntohs(sh->source) >= info->spts[0]) |
| && (ntohs(sh->source) <= info->spts[1])), |
| XT_SCTP_SRC_PORTS, info->flags, info->invflags) |
| && SCCHECK(((ntohs(sh->dest) >= info->dpts[0]) |
| && (ntohs(sh->dest) <= info->dpts[1])), |
| XT_SCTP_DEST_PORTS, info->flags, info->invflags) |
| && SCCHECK(match_packet(skb, protoff + sizeof (sctp_sctphdr_t), |
| info->chunkmap, info->chunk_match_type, |
| info->flag_info, info->flag_count, |
| hotdrop), |
| XT_SCTP_CHUNK_TYPES, info->flags, info->invflags); |
| } |
| |
| static int |
| checkentry(const char *tablename, |
| const void *inf, |
| const struct xt_match *match, |
| void *matchinfo, |
| unsigned int hook_mask) |
| { |
| const struct xt_sctp_info *info = matchinfo; |
| |
| return !(info->flags & ~XT_SCTP_VALID_FLAGS) |
| && !(info->invflags & ~XT_SCTP_VALID_FLAGS) |
| && !(info->invflags & ~info->flags) |
| && ((!(info->flags & XT_SCTP_CHUNK_TYPES)) || |
| (info->chunk_match_type & |
| (SCTP_CHUNK_MATCH_ALL |
| | SCTP_CHUNK_MATCH_ANY |
| | SCTP_CHUNK_MATCH_ONLY))); |
| } |
| |
| static struct xt_match xt_sctp_match[] = { |
| { |
| .name = "sctp", |
| .family = AF_INET, |
| .checkentry = checkentry, |
| .match = match, |
| .matchsize = sizeof(struct xt_sctp_info), |
| .proto = IPPROTO_SCTP, |
| .me = THIS_MODULE |
| }, |
| { |
| .name = "sctp", |
| .family = AF_INET6, |
| .checkentry = checkentry, |
| .match = match, |
| .matchsize = sizeof(struct xt_sctp_info), |
| .proto = IPPROTO_SCTP, |
| .me = THIS_MODULE |
| }, |
| }; |
| |
| static int __init xt_sctp_init(void) |
| { |
| return xt_register_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match)); |
| } |
| |
| static void __exit xt_sctp_fini(void) |
| { |
| xt_unregister_matches(xt_sctp_match, ARRAY_SIZE(xt_sctp_match)); |
| } |
| |
| module_init(xt_sctp_init); |
| module_exit(xt_sctp_fini); |