1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * iptables module for DCCP protocol header matching 4 * 5 * (C) 2005 by Harald Welte <laforge@netfilter.org> 6 */ 7 8 #include <linux/module.h> 9 #include <linux/skbuff.h> 10 #include <linux/slab.h> 11 #include <linux/spinlock.h> 12 #include <net/ip.h> 13 #include <linux/dccp.h> 14 15 #include <linux/netfilter/x_tables.h> 16 #include <linux/netfilter/xt_dccp.h> 17 18 #include <linux/netfilter_ipv4/ip_tables.h> 19 #include <linux/netfilter_ipv6/ip6_tables.h> 20 21 MODULE_LICENSE("GPL"); 22 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 23 MODULE_DESCRIPTION("Xtables: DCCP protocol packet match"); 24 MODULE_ALIAS("ipt_dccp"); 25 MODULE_ALIAS("ip6t_dccp"); 26 27 #define DCCHECK(cond, option, flag, invflag) (!((flag) & (option)) \ 28 || (!!((invflag) & (option)) ^ (cond))) 29 30 static unsigned char *dccp_optbuf; 31 static DEFINE_SPINLOCK(dccp_buflock); 32 33 static inline bool 34 dccp_find_option(u_int8_t option, 35 const struct sk_buff *skb, 36 unsigned int protoff, 37 const struct dccp_hdr *dh, 38 bool *hotdrop) 39 { 40 /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ 41 const unsigned char *op; 42 unsigned int optoff = __dccp_hdr_len(dh); 43 unsigned int optlen = dh->dccph_doff*4 - __dccp_hdr_len(dh); 44 unsigned int i; 45 46 if (dh->dccph_doff * 4 < __dccp_hdr_len(dh)) 47 goto invalid; 48 49 if (!optlen) 50 return false; 51 52 spin_lock_bh(&dccp_buflock); 53 op = skb_header_pointer(skb, protoff + optoff, optlen, dccp_optbuf); 54 if (op == NULL) { 55 /* If we don't have the whole header, drop packet. */ 56 goto partial; 57 } 58 59 for (i = 0; i < optlen; ) { 60 if (op[i] == option) { 61 spin_unlock_bh(&dccp_buflock); 62 return true; 63 } 64 65 if (op[i] < 2) 66 i++; 67 else 68 i += op[i+1]?:1; 69 } 70 71 spin_unlock_bh(&dccp_buflock); 72 return false; 73 74 partial: 75 spin_unlock_bh(&dccp_buflock); 76 invalid: 77 *hotdrop = true; 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, struct xt_action_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 int dccp_mt_check(const struct xt_mtchk_param *par) 125 { 126 const struct xt_dccp_info *info = par->matchinfo; 127 128 if (info->flags & ~XT_DCCP_VALID_FLAGS) 129 return -EINVAL; 130 if (info->invflags & ~XT_DCCP_VALID_FLAGS) 131 return -EINVAL; 132 if (info->invflags & ~info->flags) 133 return -EINVAL; 134 return 0; 135 } 136 137 static struct xt_match dccp_mt_reg[] __read_mostly = { 138 { 139 .name = "dccp", 140 .family = NFPROTO_IPV4, 141 .checkentry = dccp_mt_check, 142 .match = dccp_mt, 143 .matchsize = sizeof(struct xt_dccp_info), 144 .proto = IPPROTO_DCCP, 145 .me = THIS_MODULE, 146 }, 147 { 148 .name = "dccp", 149 .family = NFPROTO_IPV6, 150 .checkentry = dccp_mt_check, 151 .match = dccp_mt, 152 .matchsize = sizeof(struct xt_dccp_info), 153 .proto = IPPROTO_DCCP, 154 .me = THIS_MODULE, 155 }, 156 }; 157 158 static int __init dccp_mt_init(void) 159 { 160 int ret; 161 162 /* doff is 8 bits, so the maximum option size is (4*256). Don't put 163 * this in BSS since DaveM is worried about locked TLB's for kernel 164 * BSS. */ 165 dccp_optbuf = kmalloc(256 * 4, GFP_KERNEL); 166 if (!dccp_optbuf) 167 return -ENOMEM; 168 ret = xt_register_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); 169 if (ret) 170 goto out_kfree; 171 return ret; 172 173 out_kfree: 174 kfree(dccp_optbuf); 175 return ret; 176 } 177 178 static void __exit dccp_mt_exit(void) 179 { 180 xt_unregister_matches(dccp_mt_reg, ARRAY_SIZE(dccp_mt_reg)); 181 kfree(dccp_optbuf); 182 } 183 184 module_init(dccp_mt_init); 185 module_exit(dccp_mt_exit); 186