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This patch allows you to NAT the network address prefix onto another
network address prefix, a.k.a. netmapping.
Userspace must specify the NF_NAT_RANGE_NETMAP flag and the prefix
address through the NFTA_NAT_REG_ADDR_MIN and NFTA_NAT_REG_ADDR_MAX
netlink attributes.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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This is a patch proposal to support shifted ranges in portmaps. (i.e. tcp/udp
incoming port 5000-5100 on WAN redirected to LAN 192.168.1.5:2000-2100)
Currently DNAT only works for single port or identical port ranges. (i.e.
ports 5000-5100 on WAN interface redirected to a LAN host while original
destination port is not altered) When different port ranges are configured,
either 'random' mode should be used, or else all incoming connections are
mapped onto the first port in the redirect range. (in described example
WAN:5000-5100 will all be mapped to 192.168.1.5:2000)
This patch introduces a new mode indicated by flag NF_NAT_RANGE_PROTO_OFFSET
which uses a base port value to calculate an offset with the destination port
present in the incoming stream. That offset is then applied as index within the
redirect port range (index modulo rangewidth to handle range overflow).
In described example the base port would be 5000. An incoming stream with
destination port 5004 would result in an offset value 4 which means that the
NAT'ed stream will be using destination port 2004.
Other possibilities include deterministic mapping of larger or multiple ranges
to a smaller range : WAN:5000-5999 -> LAN:5000-5099 (maps WAN port 5*xx to port
51xx)
This patch does not change any current behavior. It just adds new NAT proto
range functionality which must be selected via the specific flag when intended
to use.
A patch for iptables (libipt_DNAT.c + libip6t_DNAT.c) will also be proposed
which makes this functionality immediately available.
Signed-off-by: Thierry Du Tre <thierry@dtsystems.be>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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license
Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.
By default are files without license information under the default
license of the kernel, which is GPLV2. Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:
NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".
otherwise syscall usage would not be possible.
Update the files which contain no license information with an SPDX
license identifier. The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception. SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Both SNAT and DNAT (and the upcoming masquerade) can have additional
configuration parameters, such as port randomization and NAT addressing
persistence. We can cover these scenarios by simply adding a flag
attribute for userspace to fill when needed.
The flags to use are defined in include/uapi/linux/netfilter/nf_nat.h:
NF_NAT_RANGE_MAP_IPS
NF_NAT_RANGE_PROTO_SPECIFIED
NF_NAT_RANGE_PROTO_RANDOM
NF_NAT_RANGE_PERSISTENT
NF_NAT_RANGE_PROTO_RANDOM_FULLY
NF_NAT_RANGE_PROTO_RANDOM_ALL
The caller must take care of not messing up with the flags, as they are
added unconditionally to the final resulting nf_nat_range.
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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We currently use prandom_u32() for allocation of ports in tcp bind(0)
and udp code. In case of plain SNAT we try to keep the ports as is
or increment on collision.
SNAT --random mode does use per-destination incrementing port
allocation. As a recent paper pointed out in [1] that this mode of
port allocation makes it possible to an attacker to find the randomly
allocated ports through a timing side-channel in a socket overloading
attack conducted through an off-path attacker.
So, NF_NAT_RANGE_PROTO_RANDOM actually weakens the port randomization
in regard to the attack described in this paper. As we need to keep
compatibility, add another flag called NF_NAT_RANGE_PROTO_RANDOM_FULLY
that would replace the NF_NAT_RANGE_PROTO_RANDOM hash-based port
selection algorithm with a simple prandom_u32() in order to mitigate
this attack vector. Note that the lfsr113's internal state is
periodically reseeded by the kernel through a local secure entropy
source.
More details can be found in [1], the basic idea is to send bursts
of packets to a socket to overflow its receive queue and measure
the latency to detect a possible retransmit when the port is found.
Because of increasing ports to given destination and port, further
allocations can be predicted. This information could then be used by
an attacker for e.g. for cache-poisoning, NS pinning, and degradation
of service attacks against DNS servers [1]:
The best defense against the poisoning attacks is to properly
deploy and validate DNSSEC; DNSSEC provides security not only
against off-path attacker but even against MitM attacker. We hope
that our results will help motivate administrators to adopt DNSSEC.
However, full DNSSEC deployment make take significant time, and
until that happens, we recommend short-term, non-cryptographic
defenses. We recommend to support full port randomisation,
according to practices recommended in [2], and to avoid
per-destination sequential port allocation, which we show may be
vulnerable to derandomisation attacks.
Joint work between Hannes Frederic Sowa and Daniel Borkmann.
[1] https://sites.google.com/site/hayashulman/files/NIC-derandomisation.pdf
[2] http://arxiv.org/pdf/1205.5190v1.pdf
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>
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Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>
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