// SPDX-License-Identifier: GPL-2.0-only
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#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 <net/ipv6.h>
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#include <net/sctp/sctp.h>
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#include <linux/sctp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_sctp.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Kiran Kumar Immidi");
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MODULE_DESCRIPTION("Xtables: SCTP protocol packet match");
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MODULE_ALIAS("ipt_sctp");
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MODULE_ALIAS("ip6t_sctp");
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#define SCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
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|| (!!((invflag) & (option)) ^ (cond)))
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static bool
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match_flags(const struct xt_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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return true;
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}
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static inline bool
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match_packet(const struct sk_buff *skb,
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unsigned int offset,
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const struct xt_sctp_info *info,
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bool *hotdrop)
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{
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u_int32_t chunkmapcopy[256 / sizeof (u_int32_t)];
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const struct sctp_chunkhdr *sch;
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struct sctp_chunkhdr _sch;
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int chunk_match_type = info->chunk_match_type;
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const struct xt_sctp_flag_info *flag_info = info->flag_info;
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int flag_count = info->flag_count;
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#ifdef DEBUG
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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, info->chunkmap);
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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 || sch->length == 0) {
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pr_debug("Dropping invalid SCTP packet.\n");
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*hotdrop = true;
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return false;
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}
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#ifdef DEBUG
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pr_debug("Chunk num: %d\toffset: %d\ttype: %d\tlength: %d"
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"\tflags: %x\n",
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++i, offset, sch->type, htons(sch->length),
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sch->flags);
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#endif
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offset += SCTP_PAD4(ntohs(sch->length));
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pr_debug("skb->len: %d\toffset: %d\n", skb->len, offset);
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if (SCTP_CHUNKMAP_IS_SET(info->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 true;
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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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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 false;
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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 false;
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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(chunkmapcopy);
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case SCTP_CHUNK_MATCH_ANY:
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return false;
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case SCTP_CHUNK_MATCH_ONLY:
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return true;
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}
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/* This will never be reached, but required to stop compiler whine */
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return false;
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}
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static bool
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sctp_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_sctp_info *info = par->matchinfo;
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const struct sctphdr *sh;
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struct sctphdr _sh;
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if (par->fragoff != 0) {
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pr_debug("Dropping non-first fragment.. FIXME\n");
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return false;
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}
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sh = skb_header_pointer(skb, par->thoff, sizeof(_sh), &_sh);
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if (sh == NULL) {
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pr_debug("Dropping evil TCP offset=0 tinygram.\n");
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par->hotdrop = true;
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return false;
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}
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pr_debug("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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XT_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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XT_SCTP_DEST_PORTS, info->flags, info->invflags) &&
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SCCHECK(match_packet(skb, par->thoff + sizeof(_sh),
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info, &par->hotdrop),
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XT_SCTP_CHUNK_TYPES, info->flags, info->invflags);
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}
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static int sctp_mt_check(const struct xt_mtchk_param *par)
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{
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const struct xt_sctp_info *info = par->matchinfo;
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if (info->flags & ~XT_SCTP_VALID_FLAGS)
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return -EINVAL;
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if (info->invflags & ~XT_SCTP_VALID_FLAGS)
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return -EINVAL;
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if (info->invflags & ~info->flags)
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return -EINVAL;
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if (!(info->flags & XT_SCTP_CHUNK_TYPES))
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return 0;
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if (info->chunk_match_type & (SCTP_CHUNK_MATCH_ALL |
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SCTP_CHUNK_MATCH_ANY | SCTP_CHUNK_MATCH_ONLY))
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return 0;
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return -EINVAL;
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}
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static struct xt_match sctp_mt_reg[] __read_mostly = {
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{
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.name = "sctp",
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.family = NFPROTO_IPV4,
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.checkentry = sctp_mt_check,
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.match = sctp_mt,
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.matchsize = sizeof(struct xt_sctp_info),
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.proto = IPPROTO_SCTP,
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.me = THIS_MODULE
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},
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{
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.name = "sctp",
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.family = NFPROTO_IPV6,
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.checkentry = sctp_mt_check,
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.match = sctp_mt,
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.matchsize = sizeof(struct xt_sctp_info),
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.proto = IPPROTO_SCTP,
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.me = THIS_MODULE
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},
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};
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static int __init sctp_mt_init(void)
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{
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return xt_register_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
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}
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static void __exit sctp_mt_exit(void)
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{
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xt_unregister_matches(sctp_mt_reg, ARRAY_SIZE(sctp_mt_reg));
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}
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module_init(sctp_mt_init);
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module_exit(sctp_mt_exit);
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