| #include <linux/types.h> |
| #include <linux/module.h> |
| #include <net/ip.h> |
| #include <linux/ipv6.h> |
| #include <net/ipv6.h> |
| #include <net/tcp.h> |
| #include <net/udp.h> |
| #include <linux/netfilter/x_tables.h> |
| #include <linux/netfilter/xt_tcpudp.h> |
| #include <linux/netfilter_ipv4/ip_tables.h> |
| #include <linux/netfilter_ipv6/ip6_tables.h> |
| |
| MODULE_DESCRIPTION("x_tables match for TCP and UDP(-Lite), supports IPv4 and IPv6"); |
| MODULE_LICENSE("GPL"); |
| MODULE_ALIAS("xt_tcp"); |
| MODULE_ALIAS("xt_udp"); |
| MODULE_ALIAS("ipt_udp"); |
| MODULE_ALIAS("ipt_tcp"); |
| MODULE_ALIAS("ip6t_udp"); |
| MODULE_ALIAS("ip6t_tcp"); |
| |
| #ifdef DEBUG_IP_FIREWALL_USER |
| #define duprintf(format, args...) printk(format , ## args) |
| #else |
| #define duprintf(format, args...) |
| #endif |
| |
| |
| /* Returns 1 if the port is matched by the range, 0 otherwise */ |
| static inline bool |
| port_match(u_int16_t min, u_int16_t max, u_int16_t port, bool invert) |
| { |
| return (port >= min && port <= max) ^ invert; |
| } |
| |
| static bool |
| tcp_find_option(u_int8_t option, |
| const struct sk_buff *skb, |
| unsigned int protoff, |
| unsigned int optlen, |
| bool invert, |
| bool *hotdrop) |
| { |
| /* tcp.doff is only 4 bits, ie. max 15 * 4 bytes */ |
| u_int8_t _opt[60 - sizeof(struct tcphdr)], *op; |
| unsigned int i; |
| |
| duprintf("tcp_match: finding option\n"); |
| |
| if (!optlen) |
| return invert; |
| |
| /* If we don't have the whole header, drop packet. */ |
| op = skb_header_pointer(skb, protoff + sizeof(struct tcphdr), |
| optlen, _opt); |
| if (op == NULL) { |
| *hotdrop = true; |
| return false; |
| } |
| |
| for (i = 0; i < optlen; ) { |
| if (op[i] == option) return !invert; |
| if (op[i] < 2) i++; |
| else i += op[i+1]?:1; |
| } |
| |
| return invert; |
| } |
| |
| static bool |
| tcp_match(const struct sk_buff *skb, |
| const struct net_device *in, |
| const struct net_device *out, |
| const struct xt_match *match, |
| const void *matchinfo, |
| int offset, |
| unsigned int protoff, |
| bool *hotdrop) |
| { |
| struct tcphdr _tcph, *th; |
| const struct xt_tcp *tcpinfo = matchinfo; |
| |
| if (offset) { |
| /* To quote Alan: |
| |
| Don't allow a fragment of TCP 8 bytes in. Nobody normal |
| causes this. Its a cracker trying to break in by doing a |
| flag overwrite to pass the direction checks. |
| */ |
| if (offset == 1) { |
| duprintf("Dropping evil TCP offset=1 frag.\n"); |
| *hotdrop = true; |
| } |
| /* Must not be a fragment. */ |
| return false; |
| } |
| |
| #define FWINVTCP(bool,invflg) ((bool) ^ !!(tcpinfo->invflags & invflg)) |
| |
| th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); |
| if (th == NULL) { |
| /* We've been asked to examine this packet, and we |
| can't. Hence, no choice but to drop. */ |
| duprintf("Dropping evil TCP offset=0 tinygram.\n"); |
| *hotdrop = true; |
| return false; |
| } |
| |
| if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], |
| ntohs(th->source), |
| !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) |
| return false; |
| if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], |
| ntohs(th->dest), |
| !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) |
| return false; |
| if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask) |
| == tcpinfo->flg_cmp, |
| XT_TCP_INV_FLAGS)) |
| return false; |
| if (tcpinfo->option) { |
| if (th->doff * 4 < sizeof(_tcph)) { |
| *hotdrop = true; |
| return false; |
| } |
| if (!tcp_find_option(tcpinfo->option, skb, protoff, |
| th->doff*4 - sizeof(_tcph), |
| tcpinfo->invflags & XT_TCP_INV_OPTION, |
| hotdrop)) |
| return false; |
| } |
| return true; |
| } |
| |
| /* Called when user tries to insert an entry of this type. */ |
| static int |
| tcp_checkentry(const char *tablename, |
| const void *info, |
| const struct xt_match *match, |
| void *matchinfo, |
| unsigned int hook_mask) |
| { |
| const struct xt_tcp *tcpinfo = matchinfo; |
| |
| /* Must specify no unknown invflags */ |
| return !(tcpinfo->invflags & ~XT_TCP_INV_MASK); |
| } |
| |
| static bool |
| udp_match(const struct sk_buff *skb, |
| const struct net_device *in, |
| const struct net_device *out, |
| const struct xt_match *match, |
| const void *matchinfo, |
| int offset, |
| unsigned int protoff, |
| bool *hotdrop) |
| { |
| struct udphdr _udph, *uh; |
| const struct xt_udp *udpinfo = matchinfo; |
| |
| /* Must not be a fragment. */ |
| if (offset) |
| return false; |
| |
| uh = skb_header_pointer(skb, protoff, sizeof(_udph), &_udph); |
| if (uh == NULL) { |
| /* We've been asked to examine this packet, and we |
| can't. Hence, no choice but to drop. */ |
| duprintf("Dropping evil UDP tinygram.\n"); |
| *hotdrop = true; |
| return false; |
| } |
| |
| return port_match(udpinfo->spts[0], udpinfo->spts[1], |
| ntohs(uh->source), |
| !!(udpinfo->invflags & XT_UDP_INV_SRCPT)) |
| && port_match(udpinfo->dpts[0], udpinfo->dpts[1], |
| ntohs(uh->dest), |
| !!(udpinfo->invflags & XT_UDP_INV_DSTPT)); |
| } |
| |
| /* Called when user tries to insert an entry of this type. */ |
| static int |
| udp_checkentry(const char *tablename, |
| const void *info, |
| const struct xt_match *match, |
| void *matchinfo, |
| unsigned int hook_mask) |
| { |
| const struct xt_tcp *udpinfo = matchinfo; |
| |
| /* Must specify no unknown invflags */ |
| return !(udpinfo->invflags & ~XT_UDP_INV_MASK); |
| } |
| |
| static struct xt_match xt_tcpudp_match[] = { |
| { |
| .name = "tcp", |
| .family = AF_INET, |
| .checkentry = tcp_checkentry, |
| .match = tcp_match, |
| .matchsize = sizeof(struct xt_tcp), |
| .proto = IPPROTO_TCP, |
| .me = THIS_MODULE, |
| }, |
| { |
| .name = "tcp", |
| .family = AF_INET6, |
| .checkentry = tcp_checkentry, |
| .match = tcp_match, |
| .matchsize = sizeof(struct xt_tcp), |
| .proto = IPPROTO_TCP, |
| .me = THIS_MODULE, |
| }, |
| { |
| .name = "udp", |
| .family = AF_INET, |
| .checkentry = udp_checkentry, |
| .match = udp_match, |
| .matchsize = sizeof(struct xt_udp), |
| .proto = IPPROTO_UDP, |
| .me = THIS_MODULE, |
| }, |
| { |
| .name = "udp", |
| .family = AF_INET6, |
| .checkentry = udp_checkentry, |
| .match = udp_match, |
| .matchsize = sizeof(struct xt_udp), |
| .proto = IPPROTO_UDP, |
| .me = THIS_MODULE, |
| }, |
| { |
| .name = "udplite", |
| .family = AF_INET, |
| .checkentry = udp_checkentry, |
| .match = udp_match, |
| .matchsize = sizeof(struct xt_udp), |
| .proto = IPPROTO_UDPLITE, |
| .me = THIS_MODULE, |
| }, |
| { |
| .name = "udplite", |
| .family = AF_INET6, |
| .checkentry = udp_checkentry, |
| .match = udp_match, |
| .matchsize = sizeof(struct xt_udp), |
| .proto = IPPROTO_UDPLITE, |
| .me = THIS_MODULE, |
| }, |
| }; |
| |
| static int __init xt_tcpudp_init(void) |
| { |
| return xt_register_matches(xt_tcpudp_match, |
| ARRAY_SIZE(xt_tcpudp_match)); |
| } |
| |
| static void __exit xt_tcpudp_fini(void) |
| { |
| xt_unregister_matches(xt_tcpudp_match, ARRAY_SIZE(xt_tcpudp_match)); |
| } |
| |
| module_init(xt_tcpudp_init); |
| module_exit(xt_tcpudp_fini); |