Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 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 int |
| 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 | int *hotdrop) |
| 40 | { |
| 41 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ |
| 42 | 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 = 1; |
| 49 | return 0; |
| 50 | } |
| 51 | |
| 52 | if (!optlen) |
| 53 | return 0; |
| 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 = 1; |
| 61 | return 0; |
| 62 | } |
| 63 | |
| 64 | for (i = 0; i < optlen; ) { |
| 65 | if (op[i] == option) { |
| 66 | spin_unlock_bh(&dccp_buflock); |
| 67 | return 1; |
| 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 0; |
| 78 | } |
| 79 | |
| 80 | |
| 81 | static inline int |
| 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 int |
| 88 | match_option(u_int8_t option, const struct sk_buff *skb, unsigned int protoff, |
| 89 | const struct dccp_hdr *dh, int *hotdrop) |
| 90 | { |
| 91 | return dccp_find_option(option, skb, protoff, dh, hotdrop); |
| 92 | } |
| 93 | |
| 94 | static int |
| 95 | match(const struct sk_buff *skb, |
| 96 | const struct net_device *in, |
| 97 | const struct net_device *out, |
| 98 | const void *matchinfo, |
| 99 | int offset, |
| 100 | unsigned int protoff, |
| 101 | int *hotdrop) |
| 102 | { |
| 103 | const struct xt_dccp_info *info = |
| 104 | (const struct xt_dccp_info *)matchinfo; |
| 105 | struct dccp_hdr _dh, *dh; |
| 106 | |
| 107 | if (offset) |
| 108 | return 0; |
| 109 | |
| 110 | dh = skb_header_pointer(skb, protoff, sizeof(_dh), &_dh); |
| 111 | if (dh == NULL) { |
| 112 | *hotdrop = 1; |
| 113 | return 0; |
| 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 int |
| 130 | checkentry(const char *tablename, |
| 131 | const void *inf, |
| 132 | void *matchinfo, |
| 133 | unsigned int matchsize, |
| 134 | unsigned int hook_mask) |
| 135 | { |
| 136 | const struct ipt_ip *ip = inf; |
| 137 | const struct xt_dccp_info *info; |
| 138 | |
| 139 | info = (const struct xt_dccp_info *)matchinfo; |
| 140 | |
| 141 | return ip->proto == IPPROTO_DCCP |
| 142 | && !(ip->invflags & XT_INV_PROTO) |
| 143 | && matchsize == XT_ALIGN(sizeof(struct xt_dccp_info)) |
| 144 | && !(info->flags & ~XT_DCCP_VALID_FLAGS) |
| 145 | && !(info->invflags & ~XT_DCCP_VALID_FLAGS) |
| 146 | && !(info->invflags & ~info->flags); |
| 147 | } |
| 148 | |
| 149 | static int |
| 150 | checkentry6(const char *tablename, |
| 151 | const void *inf, |
| 152 | void *matchinfo, |
| 153 | unsigned int matchsize, |
| 154 | unsigned int hook_mask) |
| 155 | { |
| 156 | const struct ip6t_ip6 *ip = inf; |
| 157 | const struct xt_dccp_info *info; |
| 158 | |
| 159 | info = (const struct xt_dccp_info *)matchinfo; |
| 160 | |
| 161 | return ip->proto == IPPROTO_DCCP |
| 162 | && !(ip->invflags & XT_INV_PROTO) |
| 163 | && matchsize == XT_ALIGN(sizeof(struct xt_dccp_info)) |
| 164 | && !(info->flags & ~XT_DCCP_VALID_FLAGS) |
| 165 | && !(info->invflags & ~XT_DCCP_VALID_FLAGS) |
| 166 | && !(info->invflags & ~info->flags); |
| 167 | } |
| 168 | |
| 169 | |
| 170 | static struct xt_match dccp_match = |
| 171 | { |
| 172 | .name = "dccp", |
| 173 | .match = &match, |
| 174 | .checkentry = &checkentry, |
| 175 | .me = THIS_MODULE, |
| 176 | }; |
| 177 | static struct xt_match dccp6_match = |
| 178 | { |
| 179 | .name = "dccp", |
| 180 | .match = &match, |
| 181 | .checkentry = &checkentry6, |
| 182 | .me = THIS_MODULE, |
| 183 | }; |
| 184 | |
| 185 | |
| 186 | static int __init init(void) |
| 187 | { |
| 188 | int ret; |
| 189 | |
| 190 | /* doff is 8 bits, so the maximum option size is (4*256). Don't put |
| 191 | * this in BSS since DaveM is worried about locked TLB's for kernel |
| 192 | * BSS. */ |
| 193 | dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); |
| 194 | if (!dccp_optbuf) |
| 195 | return -ENOMEM; |
| 196 | ret = xt_register_match(AF_INET, &dccp_match); |
| 197 | if (ret) |
| 198 | goto out_kfree; |
| 199 | ret = xt_register_match(AF_INET6, &dccp6_match); |
| 200 | if (ret) |
| 201 | goto out_unreg; |
| 202 | |
| 203 | return ret; |
| 204 | |
| 205 | out_unreg: |
| 206 | xt_unregister_match(AF_INET, &dccp_match); |
| 207 | out_kfree: |
| 208 | kfree(dccp_optbuf); |
| 209 | |
| 210 | return ret; |
| 211 | } |
| 212 | |
| 213 | static void __exit fini(void) |
| 214 | { |
| 215 | xt_unregister_match(AF_INET6, &dccp6_match); |
| 216 | xt_unregister_match(AF_INET, &dccp_match); |
| 217 | kfree(dccp_optbuf); |
| 218 | } |
| 219 | |
| 220 | module_init(init); |
| 221 | module_exit(fini); |