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![Marcelo Ricardo Leitner](/assets/img/avatar_default.png)
To something more meaningful these days, specially because this is working on packet headers or lengths and which are not tied to any CPU arch but to the protocol itself. So, WORD_TRUNC becomes SCTP_TRUNC4 and WORD_ROUND becomes SCTP_PAD4. Reported-by: David Laight <David.Laight@ACULAB.COM> Reported-by: David Miller <davem@davemloft.net> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
198 lines
5 KiB
C
198 lines
5 KiB
C
#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 sctp_chunkhdr_t *sch;
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sctp_chunkhdr_t _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 sctp_sctphdr_t *sh;
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sctp_sctphdr_t _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(sctp_sctphdr_t),
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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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