| 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); |