This adds IPv6 support for the tarpit target. It performs the same
functionality as the v4 version, but with IPv6 connections.
Signed-off-by: Josh Hunt <johunt@xxxxxxxxxx>
---
extensions/xt_TARPIT.c | 211 ++++++++++++++++++++++++++++++++++++++++++++---
1 files changed, 197 insertions(+), 14 deletions(-)
diff --git a/extensions/xt_TARPIT.c b/extensions/xt_TARPIT.c
index 528c012..22d0768 100644
--- a/extensions/xt_TARPIT.c
+++ b/extensions/xt_TARPIT.c
@@ -51,6 +51,12 @@
#include "compat_xtables.h"
#include "xt_TARPIT.h"
+#include <net/ipv6.h>
+#include <linux/netfilter_ipv6.h>
+#include <net/ip6_route.h>
+#include <net/ip6_checksum.h>
+#include <net/addrconf.h>
+
static bool xttarpit_tarpit(struct tcphdr *oth, struct tcphdr *tcph) {
/* No replies for RST, FIN or !SYN,!ACK */
@@ -167,7 +173,7 @@ static bool tarpit_generic(struct tcphdr *oth, struct tcphdr *tcph, uint16_t pay
return true;
}
-static void tarpit_tcp(struct sk_buff *oldskb, unsigned int hook,
+static void tarpit_tcp4(struct sk_buff *oldskb, unsigned int hook,
unsigned int mode)
{
struct tcphdr _otcph, *oth, *tcph;
@@ -297,8 +303,131 @@ static void tarpit_tcp(struct sk_buff *oldskb, unsigned int hook,
kfree_skb(nskb);
}
+static void tarpit_tcp6(struct sk_buff *oldskb, unsigned int hook,
+ unsigned int mode)
+{
+ struct sk_buff *nskb;
+ struct tcphdr *tcph, oth;
+ unsigned int otcplen;
+ int tcphoff;
+ const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
+ struct ipv6hdr *ip6h;
+#define DEFAULT_TOS_VALUE 0x0U
+ const __u8 tclass = DEFAULT_TOS_VALUE;
+ u8 proto;
+ uint16_t payload;
+
+ proto = oip6h->nexthdr;
+ tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto);
+
+ if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
+ pr_debug("Cannot get TCP header.\n");
+ return;
+ }
+
+ otcplen = oldskb->len - tcphoff;
+
+ /* IP header checks: fragment, too short. */
+ if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) {
+ pr_debug("proto(%d) != IPPROTO_TCP, "
+ "or too short. otcplen = %d\n",
+ proto, otcplen);
+ return;
+ }
+
+ if (skb_copy_bits(oldskb, tcphoff, &oth, sizeof(struct tcphdr)))
+ BUG();
+
+ /* Check checksum. */
+ if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,
+ skb_checksum(oldskb, tcphoff, otcplen, 0))) {
+ pr_debug("TCP checksum is invalid\n");
+ return;
+ }
+
+ nskb = skb_copy_expand(oldskb, LL_MAX_HEADER,
+ skb_tailroom(oldskb), GFP_ATOMIC);
+ if (!nskb) {
+ if (net_ratelimit())
+ pr_debug("cannot alloc skb\n");
+ return;
+ }
+
+ /* This packet will not be the same as the other: clear nf fields */
+ nf_reset(nskb);
+ skb_nfmark(nskb) = 0;
+ skb_init_secmark(nskb);
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 18)
+ skb_shinfo(nskb)->gso_size = 0;
+ skb_shinfo(nskb)->gso_segs = 0;
+ skb_shinfo(nskb)->gso_type = 0;
+#endif
+
+ skb_put(nskb, sizeof(struct ipv6hdr));
+ ip6h = ipv6_hdr(nskb);
+ *(__be32 *)ip6h = htonl(0x60000000 | (tclass << 20));
+ ip6h->nexthdr = IPPROTO_TCP;
+ ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr);
+ ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr);
+
+ /* Adjust IP TTL */
+ if (mode == XTTARPIT_HONEYPOT)
+ ip6h->hop_limit = 128;
+ else
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 26)
+ ip6h->hop_limit = ip6_dst_hoplimit(skb_dst(nskb));
+#else
+ ip6h->hop_limit = dst_metric(dst, RTAX_HOPLIMIT);
+ if (ip6h->hop_limit < 0)
+ ip6h->hop_limit = ipv6_get_hoplimit((skb_dst(nskb))->dev).
+#endif
+
+ tcph = (struct tcphdr *)(skb_network_header(nskb) + sizeof(struct ipv6hdr));
+
+ /* Truncate to length (no data) */
+ skb_trim(nskb, sizeof(struct ipv6hdr) + sizeof(struct tcphdr));
+ tcph->doff = sizeof(struct tcphdr)/4;
+ tcph->source = oth.dest;
+ tcph->dest = oth.source;
+
+ tcph->urg_ptr = 0;
+ /* Reset flags */
+ ((u_int8_t *)tcph)[13] = 0;
+
+ payload = nskb->len - sizeof(struct ipv6hdr) - sizeof(struct tcphdr);
+
+ if (!tarpit_generic(&oth, tcph, payload, mode))
+ return;
+
+ ip6h->payload_len = htons(sizeof(struct tcphdr));
+ tcph->check = 0;
+
+ /* Adjust TCP checksum */
+ tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
+ &ipv6_hdr(nskb)->daddr,
+ sizeof(struct tcphdr), IPPROTO_TCP,
+ csum_partial(tcph,
+ sizeof(struct tcphdr), 0));
+
+ if (ip6_route_me_harder(nskb))
+ goto free_nskb;
+
+ nskb->ip_summed = CHECKSUM_NONE;
+
+ nf_ct_attach(nskb, oldskb);
+
+ NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT, nskb, NULL,
+ skb_dst(nskb)->dev, dst_output);
+ return;
+
+free_nskb:
+ kfree_skb(nskb);
+
+}
+
static unsigned int
-tarpit_tg(struct sk_buff **pskb, const struct xt_action_param *par)
+tarpit_tg4(struct sk_buff **pskb, const struct xt_action_param *par)
{
const struct sk_buff *skb = *pskb;
const struct iphdr *iph = ip_hdr(skb);
@@ -329,29 +458,82 @@ tarpit_tg(struct sk_buff **pskb, const struct xt_action_param *par)
if (iph->frag_off & htons(IP_OFFSET))
return NF_DROP;
- tarpit_tcp(*pskb, par->hooknum, info->variant);
+ tarpit_tcp4(*pskb, par->hooknum, info->variant);
+ return NF_DROP;
+}
+
+
+static unsigned int
+tarpit_tg6(struct sk_buff **pskb, const struct xt_action_param *par)
+{
+ const struct sk_buff *skb = *pskb;
+ const struct ipv6hdr *iph = ipv6_hdr(skb);
+ const struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
+ const struct xt_tarpit_tginfo *info = par->targinfo;
+ u8 proto;
+
+ /* Do we have an input route cache entry? (Not in PREROUTING.) */
+ if (rt == NULL) {
+ pr_debug("Dropping no input route cache entry\n");
+ return NF_DROP;
+ }
+
+ /* No replies to physical multicast/broadcast */
+ /* skb != PACKET_OTHERHOST handled by ip_rcv() */
+ if (skb->pkt_type != PACKET_HOST) {
+ pr_debug("type != PACKET_HOST");
+ return NF_DROP;
+ }
+
+ /*
+ * Our naive response construction does not deal with IP
+ * options, and probably should not try.
+ */
+ proto = iph->nexthdr;
+ if (ipv6_skip_exthdr(skb, skb_network_header_len(skb), &proto) != sizeof(struct ipv6hdr))
+ return NF_DROP;
+
+ if ((!(ipv6_addr_type(&iph->saddr) & IPV6_ADDR_UNICAST)) ||
+ (!(ipv6_addr_type(&iph->daddr) & IPV6_ADDR_UNICAST))) {
+ pr_debug("addr is not unicast.\n");
+ return NF_DROP;
+ }
+
+ tarpit_tcp6(*pskb, par->hooknum, info->variant);
return NF_DROP;
}
-static struct xt_target tarpit_tg_reg __read_mostly = {
- .name = "TARPIT",
- .revision = 0,
- .family = NFPROTO_IPV4,
- .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD),
- .proto = IPPROTO_TCP,
- .target = tarpit_tg,
- .targetsize = sizeof(struct xt_tarpit_tginfo),
- .me = THIS_MODULE,
+static struct xt_target tarpit_tg_reg[] __read_mostly = {
+ {
+ .name = "TARPIT",
+ .revision = 0,
+ .family = NFPROTO_IPV4,
+ .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD),
+ .proto = IPPROTO_TCP,
+ .target = tarpit_tg4,
+ .targetsize = sizeof(struct xt_tarpit_tginfo),
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "TARPIT",
+ .revision = 0,
+ .family = NFPROTO_IPV6,
+ .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD),
+ .proto = IPPROTO_TCP,
+ .target = tarpit_tg6,
+ .targetsize = sizeof(struct xt_tarpit_tginfo),
+ .me = THIS_MODULE,
+ },
};
static int __init tarpit_tg_init(void)
{
- return xt_register_target(&tarpit_tg_reg);
+ return xt_register_targets(tarpit_tg_reg, ARRAY_SIZE(tarpit_tg_reg));
}
static void __exit tarpit_tg_exit(void)
{
- xt_unregister_target(&tarpit_tg_reg);
+ xt_unregister_targets(tarpit_tg_reg, ARRAY_SIZE(tarpit_tg_reg));
}
module_init(tarpit_tg_init);
@@ -360,3 +542,4 @@ MODULE_DESCRIPTION("Xtables: \"TARPIT\", capture and hold TCP connections");
MODULE_AUTHOR("Jan Engelhardt <jengelh@xxxxxxxxxx>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_TARPIT");
+MODULE_ALIAS("ip6t_TARPIT");
--
1.7.0.4
--
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