diff options
Diffstat (limited to 'net/netfilter/xt_sctp.c')
-rw-r--r-- | net/netfilter/xt_sctp.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/net/netfilter/xt_sctp.c b/net/netfilter/xt_sctp.c new file mode 100644 index 0000000..a189ada --- /dev/null +++ b/net/netfilter/xt_sctp.c @@ -0,0 +1,196 @@ +#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"); + +#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 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_SCTP + 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) { + 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(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, const struct xt_match_param *par) +{ + const struct xt_sctp_info *info = par->matchinfo; + const sctp_sctphdr_t *sh; + sctp_sctphdr_t _sh; + + if (par->fragoff != 0) { + duprintf("Dropping non-first fragment.. FIXME\n"); + return false; + } + + sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh); + if (sh == NULL) { + duprintf("Dropping evil TCP offset=0 tinygram.\n"); + *par->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, par->thoff + sizeof(sctp_sctphdr_t), + info, par->hotdrop), + XT_SCTP_CHUNK_TYPES, info->flags, info->invflags); +} + +static bool sctp_mt_check(const struct xt_mtchk_param *par) +{ + const struct xt_sctp_info *info = par->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 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); |