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#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");
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 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 bool
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[] __read_mostly = {
{
.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);
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