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-rw-r--r--net/netfilter/xt_tcpudp.c333
1 files changed, 333 insertions, 0 deletions
diff --git a/net/netfilter/xt_tcpudp.c b/net/netfilter/xt_tcpudp.c
new file mode 100644
index 0000000000000..33f86fd6f3e6a
--- /dev/null
+++ b/net/netfilter/xt_tcpudp.c
@@ -0,0 +1,333 @@
+#include <linux/types.h>
+#include <linux/module.h>
+#include <net/ip.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, 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);
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-05-05 21:29:44 +0000