[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>

8 files changed, 46 insertions, 4 deletions

diff --git a/net/ipv4/netfilter/ip_nat_core.c b/net/ipv4/netfilter/ip_nat_core.c
index 9d1a5175dcd4..5e08c2bf887d 100644
--- 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 b586d18b3fb3..14ff24f53a7a 100644
--- 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 5ced0877b32f..dfd521672891 100644
--- 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 a176aa3031e0..6ebaad36c06d 100644
--- 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 86a92272b053..998b2557692c 100644
--- 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 7e26a7e9bee1..439164c7a626 100644
--- 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 ab0ce4c8699f..8cae6e063bb6 100644
--- 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 b868ee0195d4..3745efe70302 100644
--- 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;
 }