204 lines
4.8 KiB
C
204 lines
4.8 KiB
C
#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <net/ip.h>
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#include <linux/sctp.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv4/ipt_sctp.h>
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#ifdef DEBUG_SCTP
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#define duprintf(format, args...) printk(format , ## args)
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#else
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#define duprintf(format, args...)
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#endif
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#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
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|| (!!((invflag) & (option)) ^ (cond)))
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static int
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match_flags(const struct ipt_sctp_flag_info *flag_info,
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const int flag_count,
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u_int8_t chunktype,
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u_int8_t chunkflags)
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{
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int i;
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for (i = 0; i < flag_count; i++) {
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if (flag_info[i].chunktype == chunktype) {
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return (chunkflags & flag_info[i].flag_mask) == flag_info[i].flag;
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}
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}
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return 1;
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}
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static int
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match_packet(const struct sk_buff *skb,
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const u_int32_t *chunkmap,
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int chunk_match_type,
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const struct ipt_sctp_flag_info *flag_info,
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const int flag_count,
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int *hotdrop)
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{
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int offset;
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u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
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sctp_chunkhdr_t _sch, *sch;
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#ifdef DEBUG_SCTP
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int i = 0;
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#endif
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if (chunk_match_type == SCTP_CHUNK_MATCH_ALL) {
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SCTP_CHUNKMAP_COPY(chunkmapcopy, chunkmap);
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}
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offset = skb->nh.iph->ihl * 4 + sizeof (sctp_sctphdr_t);
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do {
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sch = skb_header_pointer(skb, offset, sizeof(_sch), &_sch);
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if (sch == NULL) {
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duprintf("Dropping invalid SCTP packet.\n");
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*hotdrop = 1;
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return 0;
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}
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duprintf("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d\tflags: %x\n",
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++i, offset, sch->type, htons(sch->length), sch->flags);
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offset += (htons(sch->length) + 3) & ~3;
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duprintf("skb->len: %d\toffset: %d\n", skb->len, offset);
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if (SCTP_CHUNKMAP_IS_SET(chunkmap, sch->type)) {
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switch (chunk_match_type) {
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case SCTP_CHUNK_MATCH_ANY:
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if (match_flags(flag_info, flag_count,
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sch->type, sch->flags)) {
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return 1;
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}
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break;
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case SCTP_CHUNK_MATCH_ALL:
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if (match_flags(flag_info, flag_count,
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sch->type, sch->flags)) {
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SCTP_CHUNKMAP_CLEAR(chunkmapcopy, sch->type);
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}
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break;
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case SCTP_CHUNK_MATCH_ONLY:
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if (!match_flags(flag_info, flag_count,
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sch->type, sch->flags)) {
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return 0;
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}
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break;
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}
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} else {
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switch (chunk_match_type) {
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case SCTP_CHUNK_MATCH_ONLY:
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return 0;
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}
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}
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} while (offset < skb->len);
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switch (chunk_match_type) {
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case SCTP_CHUNK_MATCH_ALL:
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return SCTP_CHUNKMAP_IS_CLEAR(chunkmap);
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case SCTP_CHUNK_MATCH_ANY:
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return 0;
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case SCTP_CHUNK_MATCH_ONLY:
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return 1;
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}
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/* This will never be reached, but required to stop compiler whine */
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return 0;
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}
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static int
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match(const struct sk_buff *skb,
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const struct net_device *in,
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const struct net_device *out,
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const void *matchinfo,
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int offset,
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int *hotdrop)
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{
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const struct ipt_sctp_info *info;
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sctp_sctphdr_t _sh, *sh;
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info = (const struct ipt_sctp_info *)matchinfo;
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if (offset) {
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duprintf("Dropping non-first fragment.. FIXME\n");
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return 0;
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}
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sh = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_sh), &_sh);
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if (sh == NULL) {
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duprintf("Dropping evil TCP offset=0 tinygram.\n");
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*hotdrop = 1;
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return 0;
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}
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duprintf("spt: %d\tdpt: %d\n", ntohs(sh->source), ntohs(sh->dest));
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return SCCHECK(((ntohs(sh->source) >= info->spts[0])
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&& (ntohs(sh->source) <= info->spts[1])),
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IPT_SCTP_SRC_PORTS, info->flags, info->invflags)
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&& SCCHECK(((ntohs(sh->dest) >= info->dpts[0])
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&& (ntohs(sh->dest) <= info->dpts[1])),
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IPT_SCTP_DEST_PORTS, info->flags, info->invflags)
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&& SCCHECK(match_packet(skb, info->chunkmap, info->chunk_match_type,
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info->flag_info, info->flag_count,
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hotdrop),
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IPT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
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}
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static int
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checkentry(const char *tablename,
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const struct ipt_ip *ip,
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void *matchinfo,
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unsigned int matchsize,
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unsigned int hook_mask)
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{
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const struct ipt_sctp_info *info;
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info = (const struct ipt_sctp_info *)matchinfo;
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return ip->proto == IPPROTO_SCTP
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&& !(ip->invflags & IPT_INV_PROTO)
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&& matchsize == IPT_ALIGN(sizeof(struct ipt_sctp_info))
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&& !(info->flags & ~IPT_SCTP_VALID_FLAGS)
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&& !(info->invflags & ~IPT_SCTP_VALID_FLAGS)
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&& !(info->invflags & ~info->flags)
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&& ((!(info->flags & IPT_SCTP_CHUNK_TYPES)) ||
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(info->chunk_match_type &
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(SCTP_CHUNK_MATCH_ALL
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| SCTP_CHUNK_MATCH_ANY
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| SCTP_CHUNK_MATCH_ONLY)));
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}
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static struct ipt_match sctp_match =
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{
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.list = { NULL, NULL},
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.name = "sctp",
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.match = &match,
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.checkentry = &checkentry,
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.destroy = NULL,
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.me = THIS_MODULE
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};
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static int __init init(void)
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{
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return ipt_register_match(&sctp_match);
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}
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static void __exit fini(void)
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{
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ipt_unregister_match(&sctp_match);
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}
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module_init(init);
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module_exit(fini);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Kiran Kumar Immidi");
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MODULE_DESCRIPTION("Match for SCTP protocol packets");
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