From 2e4e6a17af35be359cc8f1c924f8f198fbd478cc Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Thu, 12 Jan 2006 13:30:04 -0800 Subject: [NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables This monster-patch tries to do the best job for unifying the data structures and backend interfaces for the three evil clones ip_tables, ip6_tables and arp_tables. In an ideal world we would never have allowed this kind of copy+paste programming... but well, our world isn't (yet?) ideal. o introduce a new x_tables module o {ip,arp,ip6}_tables depend on this x_tables module o registration functions for tables, matches and targets are only wrappers around x_tables provided functions o all matches/targets that are used from ip_tables and ip6_tables are now implemented as xt_FOOBAR.c files and provide module aliases to ipt_FOOBAR and ip6t_FOOBAR o header files for xt_matches are in include/linux/netfilter/, include/linux/netfilter_{ipv4,ipv6} contains compatibility wrappers around the xt_FOOBAR.h headers Based on this patchset we're going to further unify the code, gradually getting rid of all the layer 3 specific assumptions. Signed-off-by: Harald Welte Signed-off-by: David S. Miller --- net/netfilter/xt_tcpudp.c | 333 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 333 insertions(+) create mode 100644 net/netfilter/xt_tcpudp.c (limited to 'net/netfilter/xt_tcpudp.c') diff --git a/net/netfilter/xt_tcpudp.c b/net/netfilter/xt_tcpudp.c new file mode 100644 index 0000000..33f86fd --- /dev/null +++ b/net/netfilter/xt_tcpudp.c @@ -0,0 +1,333 @@ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +MODULE_DESCRIPTION("x_tables match for TCP and UDP, 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 int +port_match(u_int16_t min, u_int16_t max, u_int16_t port, int invert) +{ + int ret; + + ret = (port >= min && port <= max) ^ invert; + return ret; +} + +static int +tcp_find_option(u_int8_t option, + const struct sk_buff *skb, + unsigned int protoff, + unsigned int optlen, + int invert, + int *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 = 1; + return 0; + } + + 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 int +tcp_match(const struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + const void *matchinfo, + int offset, + unsigned int protoff, + int *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 = 1; + } + /* Must not be a fragment. */ + return 0; + } + +#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 = 1; + return 0; + } + + if (!port_match(tcpinfo->spts[0], tcpinfo->spts[1], + ntohs(th->source), + !!(tcpinfo->invflags & XT_TCP_INV_SRCPT))) + return 0; + if (!port_match(tcpinfo->dpts[0], tcpinfo->dpts[1], + ntohs(th->dest), + !!(tcpinfo->invflags & XT_TCP_INV_DSTPT))) + return 0; + if (!FWINVTCP((((unsigned char *)th)[13] & tcpinfo->flg_mask) + == tcpinfo->flg_cmp, + XT_TCP_INV_FLAGS)) + return 0; + if (tcpinfo->option) { + if (th->doff * 4 < sizeof(_tcph)) { + *hotdrop = 1; + return 0; + } + if (!tcp_find_option(tcpinfo->option, skb, protoff, + th->doff*4 - sizeof(_tcph), + tcpinfo->invflags & XT_TCP_INV_OPTION, + hotdrop)) + return 0; + } + return 1; +} + +/* Called when user tries to insert an entry of this type. */ +static int +tcp_checkentry(const char *tablename, + const void *info, + void *matchinfo, + unsigned int matchsize, + unsigned int hook_mask) +{ + const struct ipt_ip *ip = info; + const struct xt_tcp *tcpinfo = matchinfo; + + /* Must specify proto == TCP, and no unknown invflags */ + return ip->proto == IPPROTO_TCP + && !(ip->invflags & XT_INV_PROTO) + && matchsize == XT_ALIGN(sizeof(struct xt_tcp)) + && !(tcpinfo->invflags & ~XT_TCP_INV_MASK); +} + +/* Called when user tries to insert an entry of this type. */ +static int +tcp6_checkentry(const char *tablename, + const void *entry, + void *matchinfo, + unsigned int matchsize, + unsigned int hook_mask) +{ + const struct ip6t_ip6 *ipv6 = entry; + const struct xt_tcp *tcpinfo = matchinfo; + + /* Must specify proto == TCP, and no unknown invflags */ + return ipv6->proto == IPPROTO_TCP + && !(ipv6->invflags & XT_INV_PROTO) + && matchsize == XT_ALIGN(sizeof(struct xt_tcp)) + && !(tcpinfo->invflags & ~XT_TCP_INV_MASK); +} + + +static int +udp_match(const struct sk_buff *skb, + const struct net_device *in, + const struct net_device *out, + const void *matchinfo, + int offset, + unsigned int protoff, + int *hotdrop) +{ + struct udphdr _udph, *uh; + const struct xt_udp *udpinfo = matchinfo; + + /* Must not be a fragment. */ + if (offset) + return 0; + + 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 = 1; + return 0; + } + + 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, + void *matchinfo, + unsigned int matchinfosize, + unsigned int hook_mask) +{ + const struct ipt_ip *ip = info; + const struct xt_udp *udpinfo = matchinfo; + + /* Must specify proto == UDP, and no unknown invflags */ + if (ip->proto != IPPROTO_UDP || (ip->invflags & XT_INV_PROTO)) { + duprintf("ipt_udp: Protocol %u != %u\n", ip->proto, + IPPROTO_UDP); + return 0; + } + if (matchinfosize != XT_ALIGN(sizeof(struct xt_udp))) { + duprintf("ipt_udp: matchsize %u != %u\n", + matchinfosize, XT_ALIGN(sizeof(struct xt_udp))); + return 0; + } + if (udpinfo->invflags & ~XT_UDP_INV_MASK) { + duprintf("ipt_udp: unknown flags %X\n", + udpinfo->invflags); + return 0; + } + + return 1; +} + +/* Called when user tries to insert an entry of this type. */ +static int +udp6_checkentry(const char *tablename, + const void *entry, + void *matchinfo, + unsigned int matchinfosize, + unsigned int hook_mask) +{ + const struct ip6t_ip6 *ipv6 = entry; + const struct xt_udp *udpinfo = matchinfo; + + /* Must specify proto == UDP, and no unknown invflags */ + if (ipv6->proto != IPPROTO_UDP || (ipv6->invflags & XT_INV_PROTO)) { + duprintf("ip6t_udp: Protocol %u != %u\n", ipv6->proto, + IPPROTO_UDP); + return 0; + } + if (matchinfosize != XT_ALIGN(sizeof(struct xt_udp))) { + duprintf("ip6t_udp: matchsize %u != %u\n", + matchinfosize, XT_ALIGN(sizeof(struct xt_udp))); + return 0; + } + if (udpinfo->invflags & ~XT_UDP_INV_MASK) { + duprintf("ip6t_udp: unknown flags %X\n", + udpinfo->invflags); + return 0; + } + + return 1; +} + +static struct xt_match tcp_matchstruct = { + .name = "tcp", + .match = &tcp_match, + .checkentry = &tcp_checkentry, + .me = THIS_MODULE, +}; +static struct xt_match tcp6_matchstruct = { + .name = "tcp", + .match = &tcp_match, + .checkentry = &tcp6_checkentry, + .me = THIS_MODULE, +}; + +static struct xt_match udp_matchstruct = { + .name = "udp", + .match = &udp_match, + .checkentry = &udp_checkentry, + .me = THIS_MODULE, +}; +static struct xt_match udp6_matchstruct = { + .name = "udp", + .match = &udp_match, + .checkentry = &udp6_checkentry, + .me = THIS_MODULE, +}; + +static int __init init(void) +{ + int ret; + ret = xt_register_match(AF_INET, &tcp_matchstruct); + if (ret) + return ret; + + ret = xt_register_match(AF_INET6, &tcp6_matchstruct); + if (ret) + goto out_unreg_tcp; + + ret = xt_register_match(AF_INET, &udp_matchstruct); + if (ret) + goto out_unreg_tcp6; + + ret = xt_register_match(AF_INET6, &udp6_matchstruct); + if (ret) + goto out_unreg_udp; + + return ret; + +out_unreg_udp: + xt_unregister_match(AF_INET, &tcp_matchstruct); +out_unreg_tcp6: + xt_unregister_match(AF_INET6, &tcp6_matchstruct); +out_unreg_tcp: + xt_unregister_match(AF_INET, &tcp_matchstruct); + return ret; +} + +static void __exit fini(void) +{ + xt_unregister_match(AF_INET6, &udp6_matchstruct); + xt_unregister_match(AF_INET, &udp_matchstruct); + xt_unregister_match(AF_INET6, &tcp6_matchstruct); + xt_unregister_match(AF_INET, &tcp_matchstruct); +} + +module_init(init); +module_exit(fini); -- cgit v1.1