Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 1 | #include <linux/types.h> |
| 2 | #include <linux/module.h> |
| 3 | #include <net/ip.h> |
David S. Miller | 37d8dc8 | 2006-01-13 16:19:44 -0800 | [diff] [blame] | 4 | #include <linux/ipv6.h> |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 5 | #include <net/ipv6.h> |
| 6 | #include <net/tcp.h> |
| 7 | #include <net/udp.h> |
| 8 | #include <linux/netfilter/x_tables.h> |
| 9 | #include <linux/netfilter/xt_tcpudp.h> |
| 10 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 11 | #include <linux/netfilter_ipv6/ip6_tables.h> |
| 12 | |
| 13 | MODULE_DESCRIPTION("x_tables match for TCP and UDP, supports IPv4 and IPv6"); |
| 14 | MODULE_LICENSE("GPL"); |
| 15 | MODULE_ALIAS("xt_tcp"); |
| 16 | MODULE_ALIAS("xt_udp"); |
| 17 | MODULE_ALIAS("ipt_udp"); |
| 18 | MODULE_ALIAS("ipt_tcp"); |
| 19 | MODULE_ALIAS("ip6t_udp"); |
| 20 | MODULE_ALIAS("ip6t_tcp"); |
| 21 | |
| 22 | #ifdef DEBUG_IP_FIREWALL_USER |
| 23 | #define duprintf(format, args...) printk(format , ## args) |
| 24 | #else |
| 25 | #define duprintf(format, args...) |
| 26 | #endif |
| 27 | |
| 28 | |
| 29 | /* Returns 1 if the port is matched by the range, 0 otherwise */ |
| 30 | static inline int |
| 31 | port_match(u_int16_t min, u_int16_t max, u_int16_t port, int invert) |
| 32 | { |
| 33 | int ret; |
| 34 | |
| 35 | ret = (port >= min && port <= max) ^ invert; |
| 36 | return ret; |
| 37 | } |
| 38 | |
| 39 | static int |
| 40 | tcp_find_option(u_int8_t option, |
| 41 | const struct sk_buff *skb, |
| 42 | unsigned int protoff, |
| 43 | unsigned int optlen, |
| 44 | int invert, |
| 45 | int *hotdrop) |
| 46 | { |
| 47 | /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ |
| 48 | u_int8_t _opt[60 - sizeof(struct tcphdr)], *op; |
| 49 | unsigned int i; |
| 50 | |
| 51 | duprintf("tcp_match: finding option\n"); |
| 52 | |
| 53 | if (!optlen) |
| 54 | return invert; |
| 55 | |
| 56 | /* If we don't have the whole header, drop packet. */ |
| 57 | op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr), |
| 58 | optlen, _opt); |
| 59 | if (op == NULL) { |
| 60 | *hotdrop = 1; |
| 61 | return 0; |
| 62 | } |
| 63 | |
| 64 | for (i = 0; i < optlen; ) { |
| 65 | if (op[i] == option) return !invert; |
| 66 | if (op[i] < 2) i++; |
| 67 | else i += op[i+1]?:1; |
| 68 | } |
| 69 | |
| 70 | return invert; |
| 71 | } |
| 72 | |
| 73 | static int |
| 74 | tcp_match(const struct sk_buff *skb, |
| 75 | const struct net_device *in, |
| 76 | const struct net_device *out, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 77 | const struct xt_match *match, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 78 | const void *matchinfo, |
| 79 | int offset, |
| 80 | unsigned int protoff, |
| 81 | int *hotdrop) |
| 82 | { |
| 83 | struct tcphdr _tcph, *th; |
| 84 | const struct xt_tcp *tcpinfo = matchinfo; |
| 85 | |
| 86 | if (offset) { |
| 87 | /* To quote Alan: |
| 88 | |
| 89 | Don't allow a fragment of TCP 8 bytes in. Nobody normal |
| 90 | causes this. Its a cracker trying to break in by doing a |
| 91 | flag overwrite to pass the direction checks. |
| 92 | */ |
| 93 | if (offset == 1) { |
| 94 | duprintf("Dropping evil TCP offset=1 frag.\n"); |
| 95 | *hotdrop = 1; |
| 96 | } |
| 97 | /* Must not be a fragment. */ |
| 98 | return 0; |
| 99 | } |
| 100 | |
| 101 | #define FWINVTCP(bool,invflg) ((bool) ^ !!(tcpinfo->invflags & invflg)) |
| 102 | |
| 103 | th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
| 104 | if (th == NULL) { |
| 105 | /* We've been asked to examine this packet, and we |
| 106 | can't. Hence, no choice but to drop. */ |
| 107 | duprintf("Dropping evil TCP offset=0 tinygram.\n"); |
| 108 | *hotdrop = 1; |
| 109 | return 0; |
| 110 | } |
| 111 | |
| 112 | if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], |
| 113 | ntohs(th->source), |
| 114 | !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) |
| 115 | return 0; |
| 116 | if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], |
| 117 | ntohs(th->dest), |
| 118 | !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) |
| 119 | return 0; |
| 120 | if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask) |
| 121 | == tcpinfo->flg_cmp, |
| 122 | XT_TCP_INV_FLAGS)) |
| 123 | return 0; |
| 124 | if (tcpinfo->option) { |
| 125 | if (th->doff * 4 < sizeof(_tcph)) { |
| 126 | *hotdrop = 1; |
| 127 | return 0; |
| 128 | } |
| 129 | if (!tcp_find_option(tcpinfo->option, skb, protoff, |
| 130 | th->doff*4 - sizeof(_tcph), |
| 131 | tcpinfo->invflags & XT_TCP_INV_OPTION, |
| 132 | hotdrop)) |
| 133 | return 0; |
| 134 | } |
| 135 | return 1; |
| 136 | } |
| 137 | |
| 138 | /* Called when user tries to insert an entry of this type. */ |
| 139 | static int |
| 140 | tcp_checkentry(const char *tablename, |
| 141 | const void *info, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 142 | const struct xt_match *match, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 143 | void *matchinfo, |
| 144 | unsigned int matchsize, |
| 145 | unsigned int hook_mask) |
| 146 | { |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 147 | const struct xt_tcp *tcpinfo = matchinfo; |
| 148 | |
Patrick McHardy | 5d04bff | 2006-03-20 18:01:58 -0800 | [diff] [blame] | 149 | /* Must specify no unknown invflags */ |
| 150 | return !(tcpinfo->invflags & ~XT_TCP_INV_MASK); |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 151 | } |
| 152 | |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 153 | static int |
| 154 | udp_match(const struct sk_buff *skb, |
| 155 | const struct net_device *in, |
| 156 | const struct net_device *out, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 157 | const struct xt_match *match, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 158 | const void *matchinfo, |
| 159 | int offset, |
| 160 | unsigned int protoff, |
| 161 | int *hotdrop) |
| 162 | { |
| 163 | struct udphdr _udph, *uh; |
| 164 | const struct xt_udp *udpinfo = matchinfo; |
| 165 | |
| 166 | /* Must not be a fragment. */ |
| 167 | if (offset) |
| 168 | return 0; |
| 169 | |
| 170 | uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph); |
| 171 | if (uh == NULL) { |
| 172 | /* We've been asked to examine this packet, and we |
| 173 | can't. Hence, no choice but to drop. */ |
| 174 | duprintf("Dropping evil UDP tinygram.\n"); |
| 175 | *hotdrop = 1; |
| 176 | return 0; |
| 177 | } |
| 178 | |
| 179 | return port_match(udpinfo->spts[0], udpinfo->spts[1], |
| 180 | ntohs(uh->source), |
| 181 | !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) |
| 182 | && port_match(udpinfo->dpts[0], udpinfo->dpts[1], |
| 183 | ntohs(uh->dest), |
| 184 | !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); |
| 185 | } |
| 186 | |
| 187 | /* Called when user tries to insert an entry of this type. */ |
| 188 | static int |
| 189 | udp_checkentry(const char *tablename, |
| 190 | const void *info, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 191 | const struct xt_match *match, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 192 | void *matchinfo, |
Patrick McHardy | 5d04bff | 2006-03-20 18:01:58 -0800 | [diff] [blame] | 193 | unsigned int matchsize, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 194 | unsigned int hook_mask) |
| 195 | { |
Patrick McHardy | 5d04bff | 2006-03-20 18:01:58 -0800 | [diff] [blame] | 196 | const struct xt_tcp *udpinfo = matchinfo; |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 197 | |
Patrick McHardy | 5d04bff | 2006-03-20 18:01:58 -0800 | [diff] [blame] | 198 | /* Must specify no unknown invflags */ |
| 199 | return !(udpinfo->invflags & ~XT_UDP_INV_MASK); |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 200 | } |
| 201 | |
Patrick McHardy | 4470bbc | 2006-08-22 00:34:04 -0700 | [diff] [blame^] | 202 | static struct xt_match xt_tcpudp_match[] = { |
| 203 | { |
| 204 | .name = "tcp", |
| 205 | .family = AF_INET, |
| 206 | .checkentry = tcp_checkentry, |
| 207 | .match = tcp_match, |
| 208 | .matchsize = sizeof(struct xt_tcp), |
| 209 | .proto = IPPROTO_TCP, |
| 210 | .me = THIS_MODULE, |
| 211 | }, |
| 212 | { |
| 213 | .name = "tcp", |
| 214 | .family = AF_INET6, |
| 215 | .checkentry = tcp_checkentry, |
| 216 | .match = tcp_match, |
| 217 | .matchsize = sizeof(struct xt_tcp), |
| 218 | .proto = IPPROTO_TCP, |
| 219 | .me = THIS_MODULE, |
| 220 | }, |
| 221 | { |
| 222 | .name = "udp", |
| 223 | .family = AF_INET, |
| 224 | .checkentry = udp_checkentry, |
| 225 | .match = udp_match, |
| 226 | .matchsize = sizeof(struct xt_udp), |
| 227 | .proto = IPPROTO_UDP, |
| 228 | .me = THIS_MODULE, |
| 229 | }, |
| 230 | { |
| 231 | .name = "udp", |
| 232 | .family = AF_INET6, |
| 233 | .checkentry = udp_checkentry, |
| 234 | .match = udp_match, |
| 235 | .matchsize = sizeof(struct xt_udp), |
| 236 | .proto = IPPROTO_UDP, |
| 237 | .me = THIS_MODULE, |
| 238 | }, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 239 | }; |
| 240 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 241 | static int __init xt_tcpudp_init(void) |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 242 | { |
Patrick McHardy | 4470bbc | 2006-08-22 00:34:04 -0700 | [diff] [blame^] | 243 | return xt_register_matches(xt_tcpudp_match, |
| 244 | ARRAY_SIZE(xt_tcpudp_match)); |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 245 | } |
| 246 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 247 | static void __exit xt_tcpudp_fini(void) |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 248 | { |
Patrick McHardy | 4470bbc | 2006-08-22 00:34:04 -0700 | [diff] [blame^] | 249 | xt_unregister_matches(xt_tcpudp_match, ARRAY_SIZE(xt_tcpudp_match)); |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 250 | } |
| 251 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 252 | module_init(xt_tcpudp_init); |
| 253 | module_exit(xt_tcpudp_fini); |