| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* Kernel module to match Hop-by-Hop and Destination parameters. */ |
| 3 | |
| 4 | /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu> |
| 5 | */ |
| 6 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 7 | #include <linux/module.h> |
| 8 | #include <linux/skbuff.h> |
| 9 | #include <linux/ipv6.h> |
| 10 | #include <linux/types.h> |
| 11 | #include <net/checksum.h> |
| 12 | #include <net/ipv6.h> |
| 13 | |
| 14 | #include <asm/byteorder.h> |
| 15 | |
| 16 | #include <linux/netfilter/x_tables.h> |
| 17 | #include <linux/netfilter_ipv6/ip6_tables.h> |
| 18 | #include <linux/netfilter_ipv6/ip6t_opts.h> |
| 19 | |
| 20 | MODULE_LICENSE("GPL"); |
| 21 | MODULE_DESCRIPTION("Xtables: IPv6 Hop-By-Hop and Destination Header match"); |
| 22 | MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>"); |
| 23 | MODULE_ALIAS("ip6t_dst"); |
| 24 | |
| 25 | /* |
| 26 | * (Type & 0xC0) >> 6 |
| 27 | * 0 -> ignorable |
| 28 | * 1 -> must drop the packet |
| 29 | * 2 -> send ICMP PARM PROB regardless and drop packet |
| 30 | * 3 -> Send ICMP if not a multicast address and drop packet |
| 31 | * (Type & 0x20) >> 5 |
| 32 | * 0 -> invariant |
| 33 | * 1 -> can change the routing |
| 34 | * (Type & 0x1F) Type |
| 35 | * 0 -> Pad1 (only 1 byte!) |
| 36 | * 1 -> PadN LENGTH info (total length = length + 2) |
| 37 | * C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k ) |
| 38 | * 5 -> RTALERT 2 x x |
| 39 | */ |
| 40 | |
| 41 | static struct xt_match hbh_mt6_reg[] __read_mostly; |
| 42 | |
| 43 | static bool |
| 44 | hbh_mt6(const struct sk_buff *skb, struct xt_action_param *par) |
| 45 | { |
| 46 | struct ipv6_opt_hdr _optsh; |
| 47 | const struct ipv6_opt_hdr *oh; |
| 48 | const struct ip6t_opts *optinfo = par->matchinfo; |
| 49 | unsigned int temp; |
| 50 | unsigned int ptr = 0; |
| 51 | unsigned int hdrlen = 0; |
| 52 | bool ret = false; |
| 53 | u8 _opttype; |
| 54 | u8 _optlen; |
| 55 | const u_int8_t *tp = NULL; |
| 56 | const u_int8_t *lp = NULL; |
| 57 | unsigned int optlen; |
| 58 | int err; |
| 59 | |
| 60 | err = ipv6_find_hdr(skb, &ptr, |
| 61 | (par->match == &hbh_mt6_reg[0]) ? |
| 62 | NEXTHDR_HOP : NEXTHDR_DEST, NULL, NULL); |
| 63 | if (err < 0) { |
| 64 | if (err != -ENOENT) |
| 65 | par->hotdrop = true; |
| 66 | return false; |
| 67 | } |
| 68 | |
| 69 | oh = skb_header_pointer(skb, ptr, sizeof(_optsh), &_optsh); |
| 70 | if (oh == NULL) { |
| 71 | par->hotdrop = true; |
| 72 | return false; |
| 73 | } |
| 74 | |
| 75 | hdrlen = ipv6_optlen(oh); |
| 76 | if (skb->len - ptr < hdrlen) { |
| 77 | /* Packet smaller than it's length field */ |
| 78 | return false; |
| 79 | } |
| 80 | |
| 81 | pr_debug("IPv6 OPTS LEN %u %u ", hdrlen, oh->hdrlen); |
| 82 | |
| 83 | pr_debug("len %02X %04X %02X ", |
| 84 | optinfo->hdrlen, hdrlen, |
| 85 | (!(optinfo->flags & IP6T_OPTS_LEN) || |
| 86 | ((optinfo->hdrlen == hdrlen) ^ |
| 87 | !!(optinfo->invflags & IP6T_OPTS_INV_LEN)))); |
| 88 | |
| 89 | ret = (!(optinfo->flags & IP6T_OPTS_LEN) || |
| 90 | ((optinfo->hdrlen == hdrlen) ^ |
| 91 | !!(optinfo->invflags & IP6T_OPTS_INV_LEN))); |
| 92 | |
| 93 | ptr += 2; |
| 94 | hdrlen -= 2; |
| 95 | if (!(optinfo->flags & IP6T_OPTS_OPTS)) { |
| 96 | return ret; |
| 97 | } else { |
| 98 | pr_debug("Strict "); |
| 99 | pr_debug("#%d ", optinfo->optsnr); |
| 100 | for (temp = 0; temp < optinfo->optsnr; temp++) { |
| 101 | /* type field exists ? */ |
| 102 | if (hdrlen < 1) |
| 103 | break; |
| 104 | tp = skb_header_pointer(skb, ptr, sizeof(_opttype), |
| 105 | &_opttype); |
| 106 | if (tp == NULL) |
| 107 | break; |
| 108 | |
| 109 | /* Type check */ |
| 110 | if (*tp != (optinfo->opts[temp] & 0xFF00) >> 8) { |
| 111 | pr_debug("Tbad %02X %02X\n", *tp, |
| 112 | (optinfo->opts[temp] & 0xFF00) >> 8); |
| 113 | return false; |
| 114 | } else { |
| 115 | pr_debug("Tok "); |
| 116 | } |
| 117 | /* Length check */ |
| 118 | if (*tp) { |
| 119 | u16 spec_len; |
| 120 | |
| 121 | /* length field exists ? */ |
| 122 | if (hdrlen < 2) |
| 123 | break; |
| 124 | lp = skb_header_pointer(skb, ptr + 1, |
| 125 | sizeof(_optlen), |
| 126 | &_optlen); |
| 127 | if (lp == NULL) |
| 128 | break; |
| 129 | spec_len = optinfo->opts[temp] & 0x00FF; |
| 130 | |
| 131 | if (spec_len != 0x00FF && spec_len != *lp) { |
| 132 | pr_debug("Lbad %02X %04X\n", *lp, |
| 133 | spec_len); |
| 134 | return false; |
| 135 | } |
| 136 | pr_debug("Lok "); |
| 137 | optlen = *lp + 2; |
| 138 | } else { |
| 139 | pr_debug("Pad1\n"); |
| 140 | optlen = 1; |
| 141 | } |
| 142 | |
| 143 | /* Step to the next */ |
| 144 | pr_debug("len%04X\n", optlen); |
| 145 | |
| 146 | if ((ptr > skb->len - optlen || hdrlen < optlen) && |
| 147 | temp < optinfo->optsnr - 1) { |
| 148 | pr_debug("new pointer is too large!\n"); |
| 149 | break; |
| 150 | } |
| 151 | ptr += optlen; |
| 152 | hdrlen -= optlen; |
| 153 | } |
| 154 | if (temp == optinfo->optsnr) |
| 155 | return ret; |
| 156 | else |
| 157 | return false; |
| 158 | } |
| 159 | |
| 160 | return false; |
| 161 | } |
| 162 | |
| 163 | static int hbh_mt6_check(const struct xt_mtchk_param *par) |
| 164 | { |
| 165 | const struct ip6t_opts *optsinfo = par->matchinfo; |
| 166 | |
| 167 | if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) { |
| 168 | pr_debug("unknown flags %X\n", optsinfo->invflags); |
| 169 | return -EINVAL; |
| 170 | } |
| 171 | |
| 172 | if (optsinfo->flags & IP6T_OPTS_NSTRICT) { |
| 173 | pr_debug("Not strict - not implemented"); |
| 174 | return -EINVAL; |
| 175 | } |
| 176 | |
| 177 | return 0; |
| 178 | } |
| 179 | |
| 180 | static struct xt_match hbh_mt6_reg[] __read_mostly = { |
| 181 | { |
| 182 | /* Note, hbh_mt6 relies on the order of hbh_mt6_reg */ |
| 183 | .name = "hbh", |
| 184 | .family = NFPROTO_IPV6, |
| 185 | .match = hbh_mt6, |
| 186 | .matchsize = sizeof(struct ip6t_opts), |
| 187 | .checkentry = hbh_mt6_check, |
| 188 | .me = THIS_MODULE, |
| 189 | }, |
| 190 | { |
| 191 | .name = "dst", |
| 192 | .family = NFPROTO_IPV6, |
| 193 | .match = hbh_mt6, |
| 194 | .matchsize = sizeof(struct ip6t_opts), |
| 195 | .checkentry = hbh_mt6_check, |
| 196 | .me = THIS_MODULE, |
| 197 | }, |
| 198 | }; |
| 199 | |
| 200 | static int __init hbh_mt6_init(void) |
| 201 | { |
| 202 | return xt_register_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg)); |
| 203 | } |
| 204 | |
| 205 | static void __exit hbh_mt6_exit(void) |
| 206 | { |
| 207 | xt_unregister_matches(hbh_mt6_reg, ARRAY_SIZE(hbh_mt6_reg)); |
| 208 | } |
| 209 | |
| 210 | module_init(hbh_mt6_init); |
| 211 | module_exit(hbh_mt6_exit); |