/* * iptables module for DCCP protocol header matching * * (C) 2005 by Harald Welte <laforge@netfilter.org> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/module.h> #include <linux/skbuff.h> #include <linux/slab.h> #include <linux/spinlock.h> #include <net/ip.h> #include <linux/dccp.h> #include <linux/netfilter/x_tables.h> #include <linux/netfilter/xt_dccp.h> #include <linux/netfilter_ipv4/ip_tables.h> #include <linux/netfilter_ipv6/ip6_tables.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); MODULE_DESCRIPTION("Xtables: DCCP protocol packet match"); MODULE_ALIAS("ipt_dccp"); MODULE_ALIAS("ip6t_dccp"); #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ || (!!((invflag) & (option)) ^ (cond))) static unsigned char *dccp_optbuf; static DEFINE_SPINLOCK(dccp_buflock); static inline bool dccp_find_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, const struct dccp_hdr *dh, bool *hotdrop) { /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ const unsigned char *op; unsigned int optoff = __dccp_hdr_len(dh); unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); unsigned int i; if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) goto invalid; if (!optlen) return false; spin_lock_bh(&dccp_buflock); op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf); if (op == NULL) { /* If we don't have the whole header, drop packet. */ goto partial; } for (i = 0; i < optlen; ) { if (op[i] == option) { spin_unlock_bh(&dccp_buflock); return true; } if (op[i] < 2) i++; else i += op[i+1]?:1; } spin_unlock_bh(&dccp_buflock); return false; partial: spin_unlock_bh(&dccp_buflock); invalid: *hotdrop = true; return false; } static inline bool match_types(const struct dccp_hdr *dh, u_int16_t typemask) { return typemask & (1 << dh->dccph_type); } static inline bool match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, const struct dccp_hdr *dh, bool *hotdrop) { return dccp_find_option(option, skb, protoff, dh, hotdrop); } static bool dccp_mt(const struct sk_buff *skb, struct xt_action_param *par) { const struct xt_dccp_info *info = par->matchinfo; const struct dccp_hdr *dh; struct dccp_hdr _dh; if (par->fragoff != 0) return false; dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh); if (dh == NULL) { par->hotdrop = true; return false; } return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0] && ntohs(dh->dccph_sport) <= info->spts[1], XT_DCCP_SRC_PORTS, info->flags, info->invflags) && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0] && ntohs(dh->dccph_dport) <= info->dpts[1], XT_DCCP_DEST_PORTS, info->flags, info->invflags) && DCCHECK(match_types(dh, info->typemask), XT_DCCP_TYPE, info->flags, info->invflags) && DCCHECK(match_option(info->option, skb, par->thoff, dh, &par->hotdrop), XT_DCCP_OPTION, info->flags, info->invflags); } static int dccp_mt_check(const struct xt_mtchk_param *par) { const struct xt_dccp_info *info = par->matchinfo; if (info->flags & ~XT_DCCP_VALID_FLAGS) return -EINVAL; if (info->invflags & ~XT_DCCP_VALID_FLAGS) return -EINVAL; if (info->invflags & ~info->flags) return -EINVAL; return 0; } static struct xt_match dccp_mt_reg[] __read_mostly = { { .name = "dccp", .family = NFPROTO_IPV4, .checkentry = dccp_mt_check, .match = dccp_mt, .matchsize = sizeof(struct xt_dccp_info), .proto = IPPROTO_DCCP, .me = THIS_MODULE, }, { .name = "dccp", .family = NFPROTO_IPV6, .checkentry = dccp_mt_check, .match = dccp_mt, .matchsize = sizeof(struct xt_dccp_info), .proto = IPPROTO_DCCP, .me = THIS_MODULE, }, }; static int __init dccp_mt_init(void) { int ret; /* doff is 8 bits, so the maximum option size is (4*256). Don't put * this in BSS since DaveM is worried about locked TLB's for kernel * BSS. */ dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); if (!dccp_optbuf) return -ENOMEM; ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); if (ret) goto out_kfree; return ret; out_kfree: kfree(dccp_optbuf); return ret; } static void __exit dccp_mt_exit(void) { xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); kfree(dccp_optbuf); } module_init(dccp_mt_init); module_exit(dccp_mt_exit);