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/slab.h> 14 #include <linux/spinlock.h> 15 #include <net/ip.h> 16 #include <linux/dccp.h> 17 18 #include <linux/netfilter/x_tables.h> 19 #include <linux/netfilter/xt_dccp.h> 20 21 #include <linux/netfilter_ipv4/ip_tables.h> 22 #include <linux/netfilter_ipv6/ip6_tables.h> 23 24 MODULE_LICENSE("GPL"); 25 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 26 MODULE_DESCRIPTION("Xtables: DCCP protocol packet match"); 27 MODULE_ALIAS("ipt_dccp"); 28 MODULE_ALIAS("ip6t_dccp"); 29 30 #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ 31 || (!!((invflag) & (option)) ^ (cond))) 32 33 static unsigned char *dccp_optbuf; 34 static DEFINE_SPINLOCK(dccp_buflock); 35 36 static inline bool 37 dccp_find_option(u_int8_t option, 38 const struct sk_buff *skb, 39 unsigned int protoff, 40 const struct dccp_hdr *dh, 41 bool *hotdrop) 42 { 43 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ 44 const unsigned char *op; 45 unsigned int optoff = __dccp_hdr_len(dh); 46 unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); 47 unsigned int i; 48 49 if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) 50 goto invalid; 51 52 if (!optlen) 53 return false; 54 55 spin_lock_bh(&dccp_buflock); 56 op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf); 57 if (op == NULL) { 58 /* If we don't have the whole header, drop packet. */ 59 goto partial; 60 } 61 62 for (i = 0; i < optlen; ) { 63 if (op[i] == option) { 64 spin_unlock_bh(&dccp_buflock); 65 return true; 66 } 67 68 if (op[i] < 2) 69 i++; 70 else 71 i += op[i+1]?:1; 72 } 73 74 spin_unlock_bh(&dccp_buflock); 75 return false; 76 77 partial: 78 spin_unlock_bh(&dccp_buflock); 79 invalid: 80 *hotdrop = true; 81 return false; 82 } 83 84 85 static inline bool 86 match_types(const struct dccp_hdr *dh, u_int16_t typemask) 87 { 88 return typemask & (1 << dh->dccph_type); 89 } 90 91 static inline bool 92 match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, 93 const struct dccp_hdr *dh, bool *hotdrop) 94 { 95 return dccp_find_option(option, skb, protoff, dh, hotdrop); 96 } 97 98 static bool 99 dccp_mt(const struct sk_buff *skb, struct xt_action_param *par) 100 { 101 const struct xt_dccp_info *info = par->matchinfo; 102 const struct dccp_hdr *dh; 103 struct dccp_hdr _dh; 104 105 if (par->fragoff != 0) 106 return false; 107 108 dh = skb_header_pointer(skb, par->thoff, sizeof(_dh), &_dh); 109 if (dh == NULL) { 110 par->hotdrop = true; 111 return false; 112 } 113 114 return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0] 115 && ntohs(dh->dccph_sport) <= info->spts[1], 116 XT_DCCP_SRC_PORTS, info->flags, info->invflags) 117 && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0] 118 && ntohs(dh->dccph_dport) <= info->dpts[1], 119 XT_DCCP_DEST_PORTS, info->flags, info->invflags) 120 && DCCHECK(match_types(dh, info->typemask), 121 XT_DCCP_TYPE, info->flags, info->invflags) 122 && DCCHECK(match_option(info->option, skb, par->thoff, dh, 123 &par->hotdrop), 124 XT_DCCP_OPTION, info->flags, info->invflags); 125 } 126 127 static int dccp_mt_check(const struct xt_mtchk_param *par) 128 { 129 const struct xt_dccp_info *info = par->matchinfo; 130 131 if (info->flags & ~XT_DCCP_VALID_FLAGS) 132 return -EINVAL; 133 if (info->invflags & ~XT_DCCP_VALID_FLAGS) 134 return -EINVAL; 135 if (info->invflags & ~info->flags) 136 return -EINVAL; 137 return 0; 138 } 139 140 static struct xt_match dccp_mt_reg[] __read_mostly = { 141 { 142 .name = "dccp", 143 .family = NFPROTO_IPV4, 144 .checkentry = dccp_mt_check, 145 .match = dccp_mt, 146 .matchsize = sizeof(struct xt_dccp_info), 147 .proto = IPPROTO_DCCP, 148 .me = THIS_MODULE, 149 }, 150 { 151 .name = "dccp", 152 .family = NFPROTO_IPV6, 153 .checkentry = dccp_mt_check, 154 .match = dccp_mt, 155 .matchsize = sizeof(struct xt_dccp_info), 156 .proto = IPPROTO_DCCP, 157 .me = THIS_MODULE, 158 }, 159 }; 160 161 static int __init dccp_mt_init(void) 162 { 163 int ret; 164 165 /* doff is 8 bits, so the maximum option size is (4*256). Don't put 166 * this in BSS since DaveM is worried about locked TLB's for kernel 167 * BSS. */ 168 dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); 169 if (!dccp_optbuf) 170 return -ENOMEM; 171 ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); 172 if (ret) 173 goto out_kfree; 174 return ret; 175 176 out_kfree: 177 kfree(dccp_optbuf); 178 return ret; 179 } 180 181 static void __exit dccp_mt_exit(void) 182 { 183 xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); 184 kfree(dccp_optbuf); 185 } 186 187 module_init(dccp_mt_init); 188 module_exit(dccp_mt_exit); 189