// SPDX-License-Identifier: GPL-2.0-only
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/*
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* iptables module for DCCP protocol header matching
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*
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* (C) 2005 by Harald Welte <laforge@netfilter.org>
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*/
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <net/ip.h>
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#include <linux/dccp.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_dccp.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("Harald Welte <laforge@netfilter.org>");
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MODULE_DESCRIPTION("Xtables: DCCP protocol packet match");
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MODULE_ALIAS("ipt_dccp");
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MODULE_ALIAS("ip6t_dccp");
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#define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \
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|| (!!((invflag) & (option)) ^ (cond)))
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static unsigned char *dccp_optbuf;
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static DEFINE_SPINLOCK(dccp_buflock);
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static inline bool
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dccp_find_option(u_int8_t option,
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const struct sk_buff *skb,
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unsigned int protoff,
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const struct dccp_hdr *dh,
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bool *hotdrop)
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{
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/* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */
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const unsigned char *op;
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unsigned int optoff = __dccp_hdr_len(dh);
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unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh);
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unsigned int i;
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if (dh->dccph_doff * 4 < __dccp_hdr_len(dh))
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goto invalid;
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if (!optlen)
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return false;
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spin_lock_bh(&dccp_buflock);
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op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf);
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if (op == NULL) {
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/* If we don't have the whole header, drop packet. */
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goto partial;
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}
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for (i = 0; i < optlen; ) {
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if (op[i] == option) {
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spin_unlock_bh(&dccp_buflock);
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return true;
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}
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if (op[i] < 2)
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i++;
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else
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i += op[i+1]?:1;
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}
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spin_unlock_bh(&dccp_buflock);
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return false;
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partial:
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spin_unlock_bh(&dccp_buflock);
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invalid:
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*hotdrop = true;
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return false;
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}
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static inline bool
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match_types(const struct dccp_hdr *dh, u_int16_t typemask)
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{
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return typemask & (1 << dh->dccph_type);
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}
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static inline bool
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match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff,
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const struct dccp_hdr *dh, bool *hotdrop)
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{
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return dccp_find_option(option, skb, protoff, dh, hotdrop);
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}
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static bool
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dccp_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_dccp_info *info = par->matchinfo;
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const struct dccp_hdr *dh;
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struct dccp_hdr _dh;
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if (par->fragoff != 0)
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return false;
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dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh);
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if (dh == NULL) {
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par->hotdrop = true;
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return false;
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}
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return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0]
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&& ntohs(dh->dccph_sport) <= info->spts[1],
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XT_DCCP_SRC_PORTS, info->flags, info->invflags)
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&& DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0]
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&& ntohs(dh->dccph_dport) <= info->dpts[1],
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XT_DCCP_DEST_PORTS, info->flags, info->invflags)
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&& DCCHECK(match_types(dh, info->typemask),
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XT_DCCP_TYPE, info->flags, info->invflags)
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&& DCCHECK(match_option(info->option, skb, par->thoff, dh,
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&par->hotdrop),
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XT_DCCP_OPTION, info->flags, info->invflags);
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}
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static int dccp_mt_check(const struct xt_mtchk_param *par)
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{
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const struct xt_dccp_info *info = par->matchinfo;
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if (info->flags & ~XT_DCCP_VALID_FLAGS)
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return -EINVAL;
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if (info->invflags & ~XT_DCCP_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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return 0;
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}
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static struct xt_match dccp_mt_reg[] __read_mostly = {
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{
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.name = "dccp",
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.family = NFPROTO_IPV4,
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.checkentry = dccp_mt_check,
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.match = dccp_mt,
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.matchsize = sizeof(struct xt_dccp_info),
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.proto = IPPROTO_DCCP,
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.me = THIS_MODULE,
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},
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{
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.name = "dccp",
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.family = NFPROTO_IPV6,
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.checkentry = dccp_mt_check,
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.match = dccp_mt,
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.matchsize = sizeof(struct xt_dccp_info),
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.proto = IPPROTO_DCCP,
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.me = THIS_MODULE,
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},
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};
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static int __init dccp_mt_init(void)
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{
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int ret;
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/* doff is 8 bits, so the maximum option size is (4*256). Don't put
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* this in BSS since DaveM is worried about locked TLB's for kernel
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* BSS. */
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dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL);
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if (!dccp_optbuf)
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return -ENOMEM;
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ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
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if (ret)
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goto out_kfree;
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return ret;
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out_kfree:
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kfree(dccp_optbuf);
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return ret;
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}
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static void __exit dccp_mt_exit(void)
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{
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xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg));
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kfree(dccp_optbuf);
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}
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module_init(dccp_mt_init);
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module_exit(dccp_mt_exit);
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