| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| #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("Xtables: SCTP protocol packet match"); |
| MODULE_ALIAS("ipt_sctp"); |
| MODULE_ALIAS("ip6t_sctp"); |
| |
| #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 struct xt_sctp_info *info, |
| bool *hotdrop) |
| { |
| u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)]; |
| const sctp_chunkhdr_t *sch; |
| sctp_chunkhdr_t _sch; |
| int chunk_match_type = info->chunk_match_type; |
| const struct xt_sctp_flag_info *flag_info = info->flag_info; |
| int flag_count = info->flag_count; |
| |
| #ifdef DEBUG |
| int i = 0; |
| #endif |
| |
| if (chunk_match_type == SCTP_CHUNK_MATCH_ALL) |
| SCTP_CHUNKMAP_COPY(chunkmapcopy, info->chunkmap); |
| |
| do { |
| sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch); |
| if (sch == NULL || sch->length == 0) { |
| pr_debug("Dropping invalid SCTP packet.\n"); |
| *hotdrop = true; |
| return false; |
| } |
| #ifdef DEBUG |
| pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d" |
| "\tflags: %x\n", |
| ++i, offset, sch->type, htons(sch->length), |
| sch->flags); |
| #endif |
| offset += (ntohs(sch->length) + 3) & ~3; |
| |
| pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset); |
| |
| if (SCTP_CHUNKMAP_IS_SET(info->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(chunkmapcopy); |
| 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 |
| sctp_mt(const struct sk_buff *skb, struct xt_action_param *par) |
| { |
| const struct xt_sctp_info *info = par->matchinfo; |
| const sctp_sctphdr_t *sh; |
| sctp_sctphdr_t _sh; |
| |
| if (par->fragoff != 0) { |
| pr_debug("Dropping non-first fragment.. FIXME\n"); |
| return false; |
| } |
| |
| sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh); |
| if (sh == NULL) { |
| pr_debug("Dropping evil TCP offset=0 tinygram.\n"); |
| par->hotdrop = true; |
| return false; |
| } |
| pr_debug("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, par->thoff + sizeof(sctp_sctphdr_t), |
| info, &par->hotdrop), |
| XT_SCTP_CHUNK_TYPES, info->flags, info->invflags); |
| } |
| |
| static int sctp_mt_check(const struct xt_mtchk_param *par) |
| { |
| const struct xt_sctp_info *info = par->matchinfo; |
| |
| if (info->flags & ~XT_SCTP_VALID_FLAGS) |
| return -EINVAL; |
| if (info->invflags & ~XT_SCTP_VALID_FLAGS) |
| return -EINVAL; |
| if (info->invflags & ~info->flags) |
| return -EINVAL; |
| if (!(info->flags & XT_SCTP_CHUNK_TYPES)) |
| return 0; |
| if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL | |
| SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY)) |
| return 0; |
| return -EINVAL; |
| } |
| |
| static struct xt_match sctp_mt_reg[] __read_mostly = { |
| { |
| .name = "sctp", |
| .family = NFPROTO_IPV4, |
| .checkentry = sctp_mt_check, |
| .match = sctp_mt, |
| .matchsize = sizeof(struct xt_sctp_info), |
| .proto = IPPROTO_SCTP, |
| .me = THIS_MODULE |
| }, |
| { |
| .name = "sctp", |
| .family = NFPROTO_IPV6, |
| .checkentry = sctp_mt_check, |
| .match = sctp_mt, |
| .matchsize = sizeof(struct xt_sctp_info), |
| .proto = IPPROTO_SCTP, |
| .me = THIS_MODULE |
| }, |
| }; |
| |
| static int __init sctp_mt_init(void) |
| { |
| return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg)); |
| } |
| |
| static void __exit sctp_mt_exit(void) |
| { |
| xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg)); |
| } |
| |
| module_init(sctp_mt_init); |
| module_exit(sctp_mt_exit); |