[NETFILTER]: NAT: optional source port randomization support

This patch adds support to NAT to randomize source ports.

Signed-off-by: Eric Leblond <eric@inl.fr>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netfilter_ipv4/ip_nat.h b/include/linux/netfilter_ipv4/ip_nat.h
index bdf5536..bbca89a 100644 (file)
--- a/include/linux/netfilter_ipv4/ip_nat.h
+++ b/include/linux/netfilter_ipv4/ip_nat.h
@@ -16,6 +16,7 @@ enum ip_nat_manip_type
 
 #define IP_NAT_RANGE_MAP_IPS 1
 #define IP_NAT_RANGE_PROTO_SPECIFIED 2
+#define IP_NAT_RANGE_PROTO_RANDOM 4 /* add randomness to "port" selection */
 
 /* NAT sequence number modifications */
 struct ip_nat_seq {

diff --git a/include/net/netfilter/nf_nat.h b/include/net/netfilter/nf_nat.h
index 61c6206..bc57dd7 100644 (file)
--- a/include/net/netfilter/nf_nat.h
+++ b/include/net/netfilter/nf_nat.h
@@ -16,6 +16,7 @@ enum nf_nat_manip_type
 
 #define IP_NAT_RANGE_MAP_IPS 1
 #define IP_NAT_RANGE_PROTO_SPECIFIED 2
+#define IP_NAT_RANGE_PROTO_RANDOM 4
 
 /* NAT sequence number modifications */
 struct nf_nat_seq {

diff --git a/net/ipv4/netfilter/ip_nat_core.c b/net/ipv4/netfilter/ip_nat_core.c
index 9d1a517..5e08c2b 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_core.c
+++ b/net/ipv4/netfilter/ip_nat_core.c
@@ -246,8 +246,9 @@ get_unique_tuple(struct ip_conntrack_tuple *tuple,
        if (maniptype == IP_NAT_MANIP_SRC) {
                if (find_appropriate_src(orig_tuple, tuple, range)) {
                        DEBUGP("get_unique_tuple: Found current src map\n");
-                       if (!ip_nat_used_tuple(tuple, conntrack))
-                               return;
+                       if (!(range->flags & IP_NAT_RANGE_PROTO_RANDOM))
+                               if (!ip_nat_used_tuple(tuple, conntrack))
+                                       return;
                }
        }
 
@@ -261,6 +262,13 @@ get_unique_tuple(struct ip_conntrack_tuple *tuple,
 
        proto = ip_nat_proto_find_get(orig_tuple->dst.protonum);
 
+       /* Change protocol info to have some randomization */
+       if (range->flags & IP_NAT_RANGE_PROTO_RANDOM) {
+               proto->unique_tuple(tuple, range, maniptype, conntrack);
+               ip_nat_proto_put(proto);
+               return;
+       }
+
        /* Only bother mapping if it's not already in range and unique */
        if ((!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED)
             || proto->in_range(tuple, maniptype, &range->min, &range->max))

diff --git a/net/ipv4/netfilter/ip_nat_proto_tcp.c b/net/ipv4/netfilter/ip_nat_proto_tcp.c
index b586d18..14ff24f 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_proto_tcp.c
+++ b/net/ipv4/netfilter/ip_nat_proto_tcp.c
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 #include <linux/init.h>
+#include <linux/random.h>
 #include <linux/netfilter.h>
 #include <linux/ip.h>
 #include <linux/tcp.h>
@@ -75,6 +76,10 @@ tcp_unique_tuple(struct ip_conntrack_tuple *tuple,
                range_size = ntohs(range->max.tcp.port) - min + 1;
        }
 
+       /* Start from random port to avoid prediction */
+       if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
+               port =  net_random();
+
        for (i = 0; i < range_size; i++, port++) {
                *portptr = htons(min + port % range_size);
                if (!ip_nat_used_tuple(tuple, conntrack)) {

diff --git a/net/ipv4/netfilter/ip_nat_proto_udp.c b/net/ipv4/netfilter/ip_nat_proto_udp.c
index 5ced087..dfd5216 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_proto_udp.c
+++ b/net/ipv4/netfilter/ip_nat_proto_udp.c
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 #include <linux/init.h>
+#include <linux/random.h>
 #include <linux/netfilter.h>
 #include <linux/ip.h>
 #include <linux/udp.h>
@@ -74,6 +75,10 @@ udp_unique_tuple(struct ip_conntrack_tuple *tuple,
                range_size = ntohs(range->max.udp.port) - min + 1;
        }
 
+       /* Start from random port to avoid prediction */
+       if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
+               port = net_random();
+
        for (i = 0; i < range_size; i++, port++) {
                *portptr = htons(min + port % range_size);
                if (!ip_nat_used_tuple(tuple, conntrack))

diff --git a/net/ipv4/netfilter/ip_nat_rule.c b/net/ipv4/netfilter/ip_nat_rule.c
index a176aa3..6ebaad3 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_rule.c
+++ b/net/ipv4/netfilter/ip_nat_rule.c
@@ -193,6 +193,10 @@ static int ipt_dnat_checkentry(const char *tablename,
                printk("DNAT: multiple ranges no longer supported\n");
                return 0;
        }
+       if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM) {
+               printk("DNAT: port randomization not supported\n");
+               return 0;
+       }
        return 1;
 }
 

diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
index 86a9227..998b255 100644 (file)
--- a/net/ipv4/netfilter/nf_nat_core.c
+++ b/net/ipv4/netfilter/nf_nat_core.c
@@ -254,8 +254,9 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
        if (maniptype == IP_NAT_MANIP_SRC) {
                if (find_appropriate_src(orig_tuple, tuple, range)) {
                        DEBUGP("get_unique_tuple: Found current src map\n");
-                       if (!nf_nat_used_tuple(tuple, ct))
-                               return;
+                       if (!(range->flags & IP_NAT_RANGE_PROTO_RANDOM))
+                               if (!nf_nat_used_tuple(tuple, ct))
+                                       return;
                }
        }
 
@@ -269,6 +270,13 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
 
        proto = nf_nat_proto_find_get(orig_tuple->dst.protonum);
 
+       /* Change protocol info to have some randomization */
+       if (range->flags & IP_NAT_RANGE_PROTO_RANDOM) {
+               proto->unique_tuple(tuple, range, maniptype, ct);
+               nf_nat_proto_put(proto);
+               return;
+       }
+
        /* Only bother mapping if it's not already in range and unique */
        if ((!(range->flags & IP_NAT_RANGE_PROTO_SPECIFIED) ||
             proto->in_range(tuple, maniptype, &range->min, &range->max)) &&

diff --git a/net/ipv4/netfilter/nf_nat_proto_tcp.c b/net/ipv4/netfilter/nf_nat_proto_tcp.c
index 7e26a7e..439164c 100644 (file)
--- a/net/ipv4/netfilter/nf_nat_proto_tcp.c
+++ b/net/ipv4/netfilter/nf_nat_proto_tcp.c
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 #include <linux/init.h>
+#include <linux/random.h>
 #include <linux/ip.h>
 #include <linux/tcp.h>
 
@@ -75,6 +76,9 @@ tcp_unique_tuple(struct nf_conntrack_tuple *tuple,
                range_size = ntohs(range->max.tcp.port) - min + 1;
        }
 
+       if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
+               port =  net_random();
+
        for (i = 0; i < range_size; i++, port++) {
                *portptr = htons(min + port % range_size);
                if (!nf_nat_used_tuple(tuple, ct))

diff --git a/net/ipv4/netfilter/nf_nat_proto_udp.c b/net/ipv4/netfilter/nf_nat_proto_udp.c
index ab0ce4c..8cae6e0 100644 (file)
--- a/net/ipv4/netfilter/nf_nat_proto_udp.c
+++ b/net/ipv4/netfilter/nf_nat_proto_udp.c
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 #include <linux/init.h>
+#include <linux/random.h>
 #include <linux/ip.h>
 #include <linux/udp.h>
 
@@ -73,6 +74,9 @@ udp_unique_tuple(struct nf_conntrack_tuple *tuple,
                range_size = ntohs(range->max.udp.port) - min + 1;
        }
 
+       if (range->flags & IP_NAT_RANGE_PROTO_RANDOM)
+               port = net_random();
+
        for (i = 0; i < range_size; i++, port++) {
                *portptr = htons(min + port % range_size);
                if (!nf_nat_used_tuple(tuple, ct))

diff --git a/net/ipv4/netfilter/nf_nat_rule.c b/net/ipv4/netfilter/nf_nat_rule.c
index b868ee0..3745efe 100644 (file)
--- a/net/ipv4/netfilter/nf_nat_rule.c
+++ b/net/ipv4/netfilter/nf_nat_rule.c
@@ -226,6 +226,10 @@ static int ipt_dnat_checkentry(const char *tablename,
                printk("DNAT: multiple ranges no longer supported\n");
                return 0;
        }
+       if (mr->range[0].flags & IP_NAT_RANGE_PROTO_RANDOM) {
+               printk("DNAT: port randomization not supported\n");
+               return 0;
+       }
        return 1;
 }