1 /* 2 * iptables module for DCCP protocol header matching 3 * 4 * (C) 2005 by Harald Welte <laforge@netfilter.org> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 */ 10 11 #include <linux/module.h> 12 #include <linux/skbuff.h> 13 #include <linux/spinlock.h> 14 #include <net/ip.h> 15 #include <linux/dccp.h> 16 17 #include <linux/netfilter/x_tables.h> 18 #include <linux/netfilter/xt_dccp.h> 19 20 #include <linux/netfilter_ipv4/ip_tables.h> 21 #include <linux/netfilter_ipv6/ip6_tables.h> 22 23 MODULE_LICENSE("GPL"); 24 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 25 MODULE_DESCRIPTION("Xtables: DCCP protocol packet match"); 26 MODULE_ALIAS("ipt_dccp"); 27 MODULE_ALIAS("ip6t_dccp"); 28 29 #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ 30 || (!!((invflag) & (option)) ^ (cond))) 31 32 static unsigned char *dccp_optbuf; 33 static DEFINE_SPINLOCK(dccp_buflock); 34 35 static inline bool 36 dccp_find_option(u_int8_t option, 37 const struct sk_buff *skb, 38 unsigned int protoff, 39 const struct dccp_hdr *dh, 40 bool *hotdrop) 41 { 42 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ 43 const unsigned char *op; 44 unsigned int optoff = __dccp_hdr_len(dh); 45 unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); 46 unsigned int i; 47 48 if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) { 49 *hotdrop = true; 50 return false; 51 } 52 53 if (!optlen) 54 return false; 55 56 spin_lock_bh(&dccp_buflock); 57 op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf); 58 if (op == NULL) { 59 /* If we don't have the whole header, drop packet. */ 60 spin_unlock_bh(&dccp_buflock); 61 *hotdrop = true; 62 return false; 63 } 64 65 for (i = 0; i < optlen; ) { 66 if (op[i] == option) { 67 spin_unlock_bh(&dccp_buflock); 68 return true; 69 } 70 71 if (op[i] < 2) 72 i++; 73 else 74 i += op[i+1]?:1; 75 } 76 77 spin_unlock_bh(&dccp_buflock); 78 return false; 79 } 80 81 82 static inline bool 83 match_types(const struct dccp_hdr *dh, u_int16_t typemask) 84 { 85 return typemask & (1 << dh->dccph_type); 86 } 87 88 static inline bool 89 match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, 90 const struct dccp_hdr *dh, bool *hotdrop) 91 { 92 return dccp_find_option(option, skb, protoff, dh, hotdrop); 93 } 94 95 static bool 96 dccp_mt(const struct sk_buff *skb, const struct xt_match_param *par) 97 { 98 const struct xt_dccp_info *info = par->matchinfo; 99 const struct dccp_hdr *dh; 100 struct dccp_hdr _dh; 101 102 if (par->fragoff != 0) 103 return false; 104 105 dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh); 106 if (dh == NULL) { 107 *par->hotdrop = true; 108 return false; 109 } 110 111 return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0] 112 && ntohs(dh->dccph_sport) <= info->spts[1], 113 XT_DCCP_SRC_PORTS, info->flags, info->invflags) 114 && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0] 115 && ntohs(dh->dccph_dport) <= info->dpts[1], 116 XT_DCCP_DEST_PORTS, info->flags, info->invflags) 117 && DCCHECK(match_types(dh, info->typemask), 118 XT_DCCP_TYPE, info->flags, info->invflags) 119 && DCCHECK(match_option(info->option, skb, par->thoff, dh, 120 par->hotdrop), 121 XT_DCCP_OPTION, info->flags, info->invflags); 122 } 123 124 static bool dccp_mt_check(const struct xt_mtchk_param *par) 125 { 126 const struct xt_dccp_info *info = par->matchinfo; 127 128 return !(info->flags & ~XT_DCCP_VALID_FLAGS) 129 && !(info->invflags & ~XT_DCCP_VALID_FLAGS) 130 && !(info->invflags & ~info->flags); 131 } 132 133 static struct xt_match dccp_mt_reg[] __read_mostly = { 134 { 135 .name = "dccp", 136 .family = NFPROTO_IPV4, 137 .checkentry = dccp_mt_check, 138 .match = dccp_mt, 139 .matchsize = sizeof(struct xt_dccp_info), 140 .proto = IPPROTO_DCCP, 141 .me = THIS_MODULE, 142 }, 143 { 144 .name = "dccp", 145 .family = NFPROTO_IPV6, 146 .checkentry = dccp_mt_check, 147 .match = dccp_mt, 148 .matchsize = sizeof(struct xt_dccp_info), 149 .proto = IPPROTO_DCCP, 150 .me = THIS_MODULE, 151 }, 152 }; 153 154 static int __init dccp_mt_init(void) 155 { 156 int ret; 157 158 /* doff is 8 bits, so the maximum option size is (4*256). Don't put 159 * this in BSS since DaveM is worried about locked TLB's for kernel 160 * BSS. */ 161 dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); 162 if (!dccp_optbuf) 163 return -ENOMEM; 164 ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); 165 if (ret) 166 goto out_kfree; 167 return ret; 168 169 out_kfree: 170 kfree(dccp_optbuf); 171 return ret; 172 } 173 174 static void __exit dccp_mt_exit(void) 175 { 176 xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); 177 kfree(dccp_optbuf); 178 } 179 180 module_init(dccp_mt_init); 181 module_exit(dccp_mt_exit); 182