iptables: snat: add randomize-full support

This patch provides the userspace part for snat in order to make
randomize-full support available in {ip,nf}tables. It allows for
enabling full port randomization that was motivated in [1] and
introduced to the kernel in [2].

Joint work between Hannes Frederic Sowa and Daniel Borkmann.

 [1] https://sites.google.com/site/hayashulman/files/NIC-derandomisation.pdf
 [2] http://patchwork.ozlabs.org/patch/304306/

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/extensions/libip6t_SNAT.c b/extensions/libip6t_SNAT.c
index 7382ad0660c53bc7db5356676840cbbd0f056025..8eb50b8de8ef4acbce44fe72abf0a43f1fb5b876 100644 (file)
--- a/extensions/libip6t_SNAT.c
+++ b/extensions/libip6t_SNAT.c
@@ -18,11 +18,13 @@
 enum {
        O_TO_SRC = 0,
        O_RANDOM,
+       O_RANDOM_FULLY,
        O_PERSISTENT,
        O_X_TO_SRC,
-       F_TO_SRC   = 1 << O_TO_SRC,
-       F_RANDOM   = 1 << O_RANDOM,
-       F_X_TO_SRC = 1 << O_X_TO_SRC,
+       F_TO_SRC       = 1 << O_TO_SRC,
+       F_RANDOM       = 1 << O_RANDOM,
+       F_RANDOM_FULLY = 1 << O_RANDOM_FULLY,
+       F_X_TO_SRC     = 1 << O_X_TO_SRC,
 };
 
 static void SNAT_help(void)
@@ -31,13 +33,14 @@ static void SNAT_help(void)
 "SNAT target options:\n"
 " --to-source [<ipaddr>[-<ipaddr>]][:port[-port]]\n"
 "                              Address to map source to.\n"
-"[--random] [--persistent]\n");
+"[--random] [--random-fully] [--persistent]\n");
 }
 
 static const struct xt_option_entry SNAT_opts[] = {
        {.name = "to-source", .id = O_TO_SRC, .type = XTTYPE_STRING,
         .flags = XTOPT_MAND | XTOPT_MULTI},
        {.name = "random", .id = O_RANDOM, .type = XTTYPE_NONE},
+       {.name = "random-fully", .id = O_RANDOM_FULLY, .type = XTTYPE_NONE},
        {.name = "persistent", .id = O_PERSISTENT, .type = XTTYPE_NONE},
        XTOPT_TABLEEND,
 };
@@ -180,10 +183,13 @@ static void SNAT_parse(struct xt_option_call *cb)
 static void SNAT_fcheck(struct xt_fcheck_call *cb)
 {
        static const unsigned int f = F_TO_SRC | F_RANDOM;
+       static const unsigned int r = F_TO_SRC | F_RANDOM_FULLY;
        struct nf_nat_range *range = cb->data;
 
        if ((cb->xflags & f) == f)
                range->flags |= NF_NAT_RANGE_PROTO_RANDOM;
+       if ((cb->xflags & r) == r)
+               range->flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;
 }
 
 static void print_range(const struct nf_nat_range *range)
@@ -215,6 +221,8 @@ static void SNAT_print(const void *ip, const struct xt_entry_target *target,
        print_range(range);
        if (range->flags & NF_NAT_RANGE_PROTO_RANDOM)
                printf(" random");
+       if (range->flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)
+               printf(" random-fully");
        if (range->flags & NF_NAT_RANGE_PERSISTENT)
                printf(" persistent");
 }
@@ -227,6 +235,8 @@ static void SNAT_save(const void *ip, const struct xt_entry_target *target)
        print_range(range);
        if (range->flags & NF_NAT_RANGE_PROTO_RANDOM)
                printf(" --random");
+       if (range->flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)
+               printf(" --random-fully");
        if (range->flags & NF_NAT_RANGE_PERSISTENT)
                printf(" --persistent");
 }

diff --git a/extensions/libipt_SNAT.c b/extensions/libipt_SNAT.c
index 1a24f3d82883272168dae8546520a68476ee9db7..78d2c2b1e6b61bbe8e673b40964eba2f049ad369 100644 (file)
--- a/extensions/libipt_SNAT.c
+++ b/extensions/libipt_SNAT.c
@@ -11,11 +11,13 @@
 enum {
        O_TO_SRC = 0,
        O_RANDOM,
+       O_RANDOM_FULLY,
        O_PERSISTENT,
        O_X_TO_SRC,
-       F_TO_SRC   = 1 << O_TO_SRC,
-       F_RANDOM   = 1 << O_RANDOM,
-       F_X_TO_SRC = 1 << O_X_TO_SRC,
+       F_TO_SRC       = 1 << O_TO_SRC,
+       F_RANDOM       = 1 << O_RANDOM,
+       F_RANDOM_FULLY = 1 << O_RANDOM_FULLY,
+       F_X_TO_SRC     = 1 << O_X_TO_SRC,
 };
 
 /* Source NAT data consists of a multi-range, indicating where to map
@@ -32,13 +34,14 @@ static void SNAT_help(void)
 "SNAT target options:\n"
 " --to-source [<ipaddr>[-<ipaddr>]][:port[-port]]\n"
 "                              Address to map source to.\n"
-"[--random] [--persistent]\n");
+"[--random] [--random-fully] [--persistent]\n");
 }
 
 static const struct xt_option_entry SNAT_opts[] = {
        {.name = "to-source", .id = O_TO_SRC, .type = XTTYPE_STRING,
         .flags = XTOPT_MAND | XTOPT_MULTI},
        {.name = "random", .id = O_RANDOM, .type = XTTYPE_NONE},
+       {.name = "random-fully", .id = O_RANDOM_FULLY, .type = XTTYPE_NONE},
        {.name = "persistent", .id = O_PERSISTENT, .type = XTTYPE_NONE},
        XTOPT_TABLEEND,
 };
@@ -185,10 +188,13 @@ static void SNAT_parse(struct xt_option_call *cb)
 static void SNAT_fcheck(struct xt_fcheck_call *cb)
 {
        static const unsigned int f = F_TO_SRC | F_RANDOM;
+       static const unsigned int r = F_TO_SRC | F_RANDOM_FULLY;
        struct nf_nat_ipv4_multi_range_compat *mr = cb->data;
 
        if ((cb->xflags & f) == f)
                mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM;
+       if ((cb->xflags & r) == r)
+               mr->range[0].flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;
 }
 
 static void print_range(const struct nf_nat_ipv4_range *r)
@@ -222,6 +228,8 @@ static void SNAT_print(const void *ip, const struct xt_entry_target *target,
                print_range(&info->mr.range[i]);
                if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM)
                        printf(" random");
+               if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)
+                       printf(" random-fully");
                if (info->mr.range[i].flags & NF_NAT_RANGE_PERSISTENT)
                        printf(" persistent");
        }
@@ -237,6 +245,8 @@ static void SNAT_save(const void *ip, const struct xt_entry_target *target)
                print_range(&info->mr.range[i]);
                if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM)
                        printf(" --random");
+               if (info->mr.range[i].flags & NF_NAT_RANGE_PROTO_RANDOM_FULLY)
+                       printf(" --random-fully");
                if (info->mr.range[i].flags & NF_NAT_RANGE_PERSISTENT)
                        printf(" --persistent");
        }

diff --git a/extensions/libxt_SNAT.man b/extensions/libxt_SNAT.man
index f0620a21eb9ce7c6627fa8fdd89be8d4f11ae6a9..8cd0b80e9ed4a508d47247a902836931ad019820 100644 (file)
--- a/extensions/libxt_SNAT.man
+++ b/extensions/libxt_SNAT.man
@@ -29,7 +29,12 @@ anymore.
 \fB\-\-random\fP
 If option
 \fB\-\-random\fP
-is used then port mapping will be randomized (kernel >= 2.6.21).
+is used then port mapping will be randomized through a hash-based algorithm (kernel >= 2.6.21).
+.TP
+\fB\-\-random-fully\fP
+If option
+\fB\-\-random-fully\fP
+is used then port mapping will be fully randomized through a PRNG (kernel >= 3.14).
 .TP
 \fB\-\-persistent\fP
 Gives a client the same source-/destination-address for each connection.

diff --git a/include/linux/netfilter/nf_nat.h b/include/linux/netfilter/nf_nat.h
index bf0cc373ffb6ae02487e74ba478c024c3be3b477..1ad3659102b64d54a8ad814fd7be11132a136319 100644 (file)
--- a/include/linux/netfilter/nf_nat.h
+++ b/include/linux/netfilter/nf_nat.h
@@ -4,10 +4,14 @@
 #include <linux/netfilter.h>
 #include <linux/netfilter/nf_conntrack_tuple_common.h>
 
-#define NF_NAT_RANGE_MAP_IPS           1
-#define NF_NAT_RANGE_PROTO_SPECIFIED   2
-#define NF_NAT_RANGE_PROTO_RANDOM      4
-#define NF_NAT_RANGE_PERSISTENT                8
+#define NF_NAT_RANGE_MAP_IPS                   (1 << 0)
+#define NF_NAT_RANGE_PROTO_SPECIFIED           (1 << 1)
+#define NF_NAT_RANGE_PROTO_RANDOM              (1 << 2)
+#define NF_NAT_RANGE_PERSISTENT                        (1 << 3)
+#define NF_NAT_RANGE_PROTO_RANDOM_FULLY                (1 << 4)
+
+#define NF_NAT_RANGE_PROTO_RANDOM_ALL          \
+       (NF_NAT_RANGE_PROTO_RANDOM | NF_NAT_RANGE_PROTO_RANDOM_FULLY)
 
 struct nf_nat_ipv4_range {
        unsigned int                    flags;