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("Match for DCCP protocol packets"); 26 MODULE_ALIAS("ipt_dccp"); 27 28 #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ 29 || (!!((invflag) & (option)) ^ (cond))) 30 31 static unsigned char *dccp_optbuf; 32 static DEFINE_SPINLOCK(dccp_buflock); 33 34 static inline bool 35 dccp_find_option(u_int8_t option, 36 const struct sk_buff *skb, 37 unsigned int protoff, 38 const struct dccp_hdr *dh, 39 bool *hotdrop) 40 { 41 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ 42 const unsigned char *op; 43 unsigned int optoff = __dccp_hdr_len(dh); 44 unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); 45 unsigned int i; 46 47 if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) { 48 *hotdrop = true; 49 return false; 50 } 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 spin_unlock_bh(&dccp_buflock); 60 *hotdrop = true; 61 return false; 62 } 63 64 for (i = 0; i < optlen; ) { 65 if (op[i] == option) { 66 spin_unlock_bh(&dccp_buflock); 67 return true; 68 } 69 70 if (op[i] < 2) 71 i++; 72 else 73 i += op[i+1]?:1; 74 } 75 76 spin_unlock_bh(&dccp_buflock); 77 return false; 78 } 79 80 81 static inline bool 82 match_types(const struct dccp_hdr *dh, u_int16_t typemask) 83 { 84 return typemask & (1 << dh->dccph_type); 85 } 86 87 static inline bool 88 match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, 89 const struct dccp_hdr *dh, bool *hotdrop) 90 { 91 return dccp_find_option(option, skb, protoff, dh, hotdrop); 92 } 93 94 static bool 95 match(const struct sk_buff *skb, 96 const struct net_device *in, 97 const struct net_device *out, 98 const struct xt_match *match, 99 const void *matchinfo, 100 int offset, 101 unsigned int protoff, 102 bool *hotdrop) 103 { 104 const struct xt_dccp_info *info = matchinfo; 105 struct dccp_hdr _dh, *dh; 106 107 if (offset) 108 return false; 109 110 dh = skb_header_pointer(skb, protoff, sizeof(_dh), &_dh); 111 if (dh == NULL) { 112 *hotdrop = true; 113 return false; 114 } 115 116 return DCCHECK(ntohs(dh->dccph_sport) >= info->spts[0] 117 && ntohs(dh->dccph_sport) <= info->spts[1], 118 XT_DCCP_SRC_PORTS, info->flags, info->invflags) 119 && DCCHECK(ntohs(dh->dccph_dport) >= info->dpts[0] 120 && ntohs(dh->dccph_dport) <= info->dpts[1], 121 XT_DCCP_DEST_PORTS, info->flags, info->invflags) 122 && DCCHECK(match_types(dh, info->typemask), 123 XT_DCCP_TYPE, info->flags, info->invflags) 124 && DCCHECK(match_option(info->option, skb, protoff, dh, 125 hotdrop), 126 XT_DCCP_OPTION, info->flags, info->invflags); 127 } 128 129 static bool 130 checkentry(const char *tablename, 131 const void *inf, 132 const struct xt_match *match, 133 void *matchinfo, 134 unsigned int hook_mask) 135 { 136 const struct xt_dccp_info *info = matchinfo; 137 138 return !(info->flags & ~XT_DCCP_VALID_FLAGS) 139 && !(info->invflags & ~XT_DCCP_VALID_FLAGS) 140 && !(info->invflags & ~info->flags); 141 } 142 143 static struct xt_match xt_dccp_match[] = { 144 { 145 .name = "dccp", 146 .family = AF_INET, 147 .checkentry = checkentry, 148 .match = match, 149 .matchsize = sizeof(struct xt_dccp_info), 150 .proto = IPPROTO_DCCP, 151 .me = THIS_MODULE, 152 }, 153 { 154 .name = "dccp", 155 .family = AF_INET6, 156 .checkentry = checkentry, 157 .match = match, 158 .matchsize = sizeof(struct xt_dccp_info), 159 .proto = IPPROTO_DCCP, 160 .me = THIS_MODULE, 161 }, 162 }; 163 164 static int __init xt_dccp_init(void) 165 { 166 int ret; 167 168 /* doff is 8 bits, so the maximum option size is (4*256). Don't put 169 * this in BSS since DaveM is worried about locked TLB's for kernel 170 * BSS. */ 171 dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); 172 if (!dccp_optbuf) 173 return -ENOMEM; 174 ret = xt_register_matches(xt_dccp_match, ARRAY_SIZE(xt_dccp_match)); 175 if (ret) 176 goto out_kfree; 177 return ret; 178 179 out_kfree: 180 kfree(dccp_optbuf); 181 return ret; 182 } 183 184 static void __exit xt_dccp_fini(void) 185 { 186 xt_unregister_matches(xt_dccp_match, ARRAY_SIZE(xt_dccp_match)); 187 kfree(dccp_optbuf); 188 } 189 190 module_init(xt_dccp_init); 191 module_exit(xt_dccp_fini); 192