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// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include <net/sctp/sctp.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 struct sctp_chunkhdr *sch;
struct sctp_chunkhdr _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 += SCTP_PAD4(ntohs(sch->length));
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 struct sctphdr *sh;
struct sctphdr _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(_sh),
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);
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