mirror of https://github.com/hak5/openwrt.git
Florian Fainelli
parent
d97af0443e
commit
b147f12cb2
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@ -1,318 +0,0 @@
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--- a/net/netfilter/Kconfig
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+++ b/net/netfilter/Kconfig
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@@ -469,6 +469,23 @@ config NETFILTER_XT_TARGET_SECMARK
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To compile it as a module, choose M here. If unsure, say N.
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+config NETFILTER_XT_TARGET_TARPIT
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+ tristate '"TARPIT" target support'
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+ depends on NETFILTER_XTABLES
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+ ---help---
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+ Adds a TARPIT target to iptables, which captures and holds
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+ incoming TCP connections using no local per-connection resources.
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+ Connections are accepted, but immediately switched to the persist
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+ state (0 byte window), in which the remote side stops sending data
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+ and asks to continue every 60-240 seconds. Attempts to close the
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+ connection are ignored, forcing the remote side to time out the
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+ connection in 12-24 minutes.
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+
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+ This offers similar functionality to LaBrea
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+ <http://www.hackbusters.net/LaBrea/>, but does not require dedicated
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+ hardware or IPs. Any TCP port that you would normally DROP or REJECT
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+ can instead become a tarpit.
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+
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config NETFILTER_XT_TARGET_TCPMSS
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tristate '"TCPMSS" target support'
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depends on (IPV6 || IPV6=n)
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--- a/net/netfilter/Makefile
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+++ b/net/netfilter/Makefile
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@@ -51,6 +51,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE
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obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o
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obj-$(CONFIG_NETFILTER_XT_TARGET_RATEEST) += xt_RATEEST.o
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obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
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+obj-$(CONFIG_NETFILTER_XT_TARGET_TARPIT) += xt_TARPIT.o
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obj-$(CONFIG_NETFILTER_XT_TARGET_TPROXY) += xt_TPROXY.o
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obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
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obj-$(CONFIG_NETFILTER_XT_TARGET_TCPOPTSTRIP) += xt_TCPOPTSTRIP.o
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--- /dev/null
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+++ b/net/netfilter/xt_TARPIT.c
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@@ -0,0 +1,279 @@
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+/*
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+ * Kernel module to capture and hold incoming TCP connections using
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+ * no local per-connection resources.
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+ *
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+ * Based on ipt_REJECT.c and offering functionality similar to
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+ * LaBrea <http://www.hackbusters.net/LaBrea/>.
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+ *
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+ * Copyright (c) 2002 Aaron Hopkins <tools@die.net>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation; either version 2 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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+ *
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+ * Goal:
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+ * - Allow incoming TCP connections to be established.
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+ * - Passing data should result in the connection being switched to the
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+ * persist state (0 byte window), in which the remote side stops sending
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+ * data and asks to continue every 60 seconds.
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+ * - Attempts to shut down the connection should be ignored completely, so
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+ * the remote side ends up having to time it out.
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+ *
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+ * This means:
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+ * - Reply to TCP SYN,!ACK,!RST,!FIN with SYN-ACK, window 5 bytes
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+ * - Reply to TCP SYN,ACK,!RST,!FIN with RST to prevent spoofing
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+ * - Reply to TCP !SYN,!RST,!FIN with ACK, window 0 bytes, rate-limited
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+ */
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+
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+#include <linux/version.h>
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+#include <linux/module.h>
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+#include <linux/skbuff.h>
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+#include <linux/ip.h>
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+#include <net/ip.h>
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+#include <net/tcp.h>
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+#include <net/icmp.h>
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+struct in_device;
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+#include <net/route.h>
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+#include <linux/random.h>
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+#include <linux/netfilter_ipv4/ip_tables.h>
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+
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+#if 0
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+#define DEBUGP printk
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+#else
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+#define DEBUGP(format, args...)
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+#endif
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+
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+/* Stolen from ip_finish_output2 */
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+static int ip_direct_send(struct sk_buff *skb)
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+{
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+ struct dst_entry *dst = skb->dst;
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+
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+ if (dst->hh != NULL)
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+ return neigh_hh_output(dst->hh, skb);
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+ else if (dst->neighbour != NULL)
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+ return dst->neighbour->output(skb);
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+
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+ if (net_ratelimit())
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+ printk(KERN_DEBUG "TARPIT ip_direct_send: no header cache and no neighbor!\n");
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+
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+ kfree_skb(skb);
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+ return -EINVAL;
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+}
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+
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+
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+/* Send reply */
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+static void tarpit_tcp(const struct sk_buff *oskb, struct rtable *ort,
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+ unsigned int local)
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+{
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+ struct sk_buff *nskb;
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+ struct rtable *nrt;
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+ struct tcphdr *otcph, *ntcph;
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+ struct flowi fl = {};
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+ unsigned int otcplen;
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+ u_int16_t tmp;
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+
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+ const struct iphdr *oiph = ip_hdr(oskb);
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+ struct iphdr *niph;
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+
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+ /* A truncated TCP header is not going to be useful */
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+ if (oskb->len < ip_hdrlen(oskb) + sizeof(struct tcphdr))
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+ return;
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+
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+ otcph = (void *)oiph + ip_hdrlen(oskb);
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+ otcplen = oskb->len - ip_hdrlen(oskb);
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+
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+ /* No replies for RST or FIN */
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+ if (otcph->rst || otcph->fin)
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+ return;
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+
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+ /* No reply to !SYN,!ACK. Rate-limit replies to !SYN,ACKs */
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+ if (!otcph->syn && (!otcph->ack || !xrlim_allow(&ort->u.dst, 1*HZ)))
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+ return;
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+
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+ /* Check checksum. */
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+ if (tcp_v4_check(otcplen, oiph->saddr, oiph->daddr,
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+ csum_partial((char *)otcph, otcplen, 0)) != 0)
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+ return;
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+
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+ /*
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+ * Copy skb (even if skb is about to be dropped, we cannot just
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+ * clone it because there may be other things, such as tcpdump,
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+ * interested in it)
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+ */
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+ nskb = skb_copy(oskb, GFP_ATOMIC);
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+ if (nskb == NULL)
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+ return;
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+
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+ niph = ip_hdr(nskb);
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+
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+ /* This packet will not be the same as the other: clear nf fields */
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+ nf_conntrack_put(nskb->nfct);
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+ nskb->nfct = NULL;
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+#ifdef CONFIG_NETFILTER_DEBUG
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+ nskb->nf_debug = 0;
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+#endif
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+
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+ ntcph = (void *)niph + ip_hdrlen(nskb);
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+
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+ /* Truncate to length (no data) */
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+ ntcph->doff = sizeof(struct tcphdr)/4;
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+ skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr));
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+ niph->tot_len = htons(nskb->len);
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+
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+ /* Swap source and dest */
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+ niph->daddr = xchg(&niph->saddr, niph->daddr);
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+ tmp = ntcph->source;
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+ ntcph->source = ntcph->dest;
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+ ntcph->dest = tmp;
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+
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+ /* Use supplied sequence number or make a new one */
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+ ntcph->seq = otcph->ack ? otcph->ack_seq
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+ : htonl(secure_tcp_sequence_number(niph->saddr,
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+ niph->daddr,
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+ ntcph->source,
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+ ntcph->dest));
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+
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+ /* Our SYN-ACKs must have a >0 window */
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+ ntcph->window = (otcph->syn && !otcph->ack) ? htons(5) : 0;
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+
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+ ntcph->urg_ptr = 0;
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+
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+ /* Reset flags */
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+ ((u_int8_t *)ntcph)[13] = 0;
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+
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+ if (otcph->syn && otcph->ack) {
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+ ntcph->rst = 1;
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+ ntcph->ack_seq = 0;
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+ } else {
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+ ntcph->syn = otcph->syn;
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+ ntcph->ack = 1;
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+ ntcph->ack_seq = htonl(ntohl(otcph->seq) + otcph->syn);
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+ }
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+
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+ /* Adjust TCP checksum */
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+ ntcph->check = 0;
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+ ntcph->check = tcp_v4_check(sizeof(struct tcphdr),
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+ niph->saddr,
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+ niph->daddr,
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+ csum_partial((char *)ntcph,
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+ sizeof(struct tcphdr), 0));
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+
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+ fl.nl_u.ip4_u.daddr = niph->daddr;
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+ fl.nl_u.ip4_u.saddr = local ? niph->saddr : 0;
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+ fl.nl_u.ip4_u.tos = RT_TOS(niph->tos) | RTO_CONN;
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+ fl.oif = 0;
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+
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+ if (ip_route_output_key(&init_net, &nrt, &fl))
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+ goto free_nskb;
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+
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+ dst_release(nskb->dst);
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+ nskb->dst = &nrt->u.dst;
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+
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+ /* Adjust IP TTL */
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+ niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
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+
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+ /* Set DF, id = 0 */
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+ niph->frag_off = htons(IP_DF);
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+ niph->id = 0;
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+
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+ /* Adjust IP checksum */
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+ niph->check = 0;
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+ niph->check = ip_fast_csum((unsigned char *)niph, niph->ihl);
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+
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+ /* "Never happens" */
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+ if (nskb->len > dst_mtu(nskb->dst))
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+ goto free_nskb;
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+
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+ ip_direct_send(nskb);
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+ return;
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+
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+ free_nskb:
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+ kfree_skb(nskb);
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+}
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+
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+static unsigned int xt_tarpit_target(struct sk_buff *skb,
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+ const struct net_device *in,
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+ const struct net_device *out,
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+ unsigned int hooknum,
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+ const struct xt_target *target,
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+ const void *targinfo)
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+{
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+ const struct iphdr *iph = ip_hdr(skb);
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+ struct rtable *rt = (void *)skb->dst;
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+
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+ /* Do we have an input route cache entry? */
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+ if (rt == NULL)
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+ return NF_DROP;
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+
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+ /* No replies to physical multicast/broadcast */
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+ if (skb->pkt_type != PACKET_HOST && skb->pkt_type != PACKET_OTHERHOST)
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+ return NF_DROP;
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+
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+ /* Now check at the protocol level */
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+ if (rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
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+ return NF_DROP;
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+
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+ /*
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+ * Our naive response construction does not deal with IP
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+ * options, and probably should not try.
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+ */
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+ if (iph->ihl * 4 != sizeof(struct iphdr))
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+ return NF_DROP;
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+
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+ /* We are not interested in fragments */
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+ if (iph->frag_off & htons(IP_OFFSET))
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+ return NF_DROP;
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+
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+ tarpit_tcp(skb, rt, hooknum == NF_INET_LOCAL_IN);
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+ return NF_DROP;
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+}
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+
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+static bool xt_tarpit_check(const char *tablename, const void *entry,
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+ const struct xt_target *target, void *targinfo,
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+ unsigned int hook_mask)
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+{
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+ bool invalid;
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+
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+ if (strcmp(tablename, "raw") == 0 && hook_mask == NF_INET_PRE_ROUTING)
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+ return true;
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+ if (strcmp(tablename, "filter") != 0)
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+ return false;
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+ invalid = hook_mask & ~((1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD));
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+ return !invalid;
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+}
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+
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+static struct xt_target xt_tarpit_reg = {
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+ .name = "TARPIT",
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+ .family = AF_INET,
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+ .proto = IPPROTO_TCP,
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+ .target = xt_tarpit_target,
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+ .checkentry = xt_tarpit_check,
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+ .me = THIS_MODULE,
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+};
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+
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+static int __init xt_tarpit_init(void)
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+{
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+ return xt_register_target(&xt_tarpit_reg);
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+}
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+
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+static void __exit xt_tarpit_exit(void)
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+{
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+ xt_unregister_target(&xt_tarpit_reg);
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+}
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+
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+module_init(xt_tarpit_init);
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+module_exit(xt_tarpit_exit);
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+MODULE_DESCRIPTION("netfilter xt_TARPIT target module");
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+MODULE_AUTHOR("Jan Engelhardt <jengelh@gmx.de>");
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+MODULE_LICENSE("GPL");
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+MODULE_ALIAS("ipt_TARPIT");
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Reference in New Issue