One document matched: draft-rafiee-6man-ra-privacy-02.txt
Differences from draft-rafiee-6man-ra-privacy-01.txt
IPv6 maintenance Working Group (6man) H. Rafiee
INTERNET-DRAFT C. Meinel
Updates RFC 4941 (if approved) Hasso Plattner Institute
Intended status: Proposed Standard
Expires: November 14, 2013 May 14, 2013
Router Advertisement based privacy extension in IPv6 autoconfiguration
<draft-rafiee-6man-ra-privacy-02.txt>
Abstract
Privacy is an important issue concerning many governments and users
with its importance becoming more evident every day. Nodes might
change their IP addresses frequently in order to avoid being tracked
by attackers. This frequent IP address change also helps in the
prevention of information being leaked by nodes. In IPv6 networks
there is currently one solution to maintain the privacy of nodes when
IPv6 StateLess Address AutoConfiguration (SLAAC) (RFC 4662) is used.
Unfortunately there are some problems associated with this solution
which entails the use of the Privacy Extension (RFC 4941). Some of
these problems are not generating a new Interface ID (IID) after
changing the router prefix, the fact that nodes may use an IID that
was generated based on a MAC address and use this in their response,
the act of cutting the current connections to other nodes if the max
lifetime of the old IID has elapsed, and a need to have stable
storage for generating a randomized IID. The RFC also gives no
explanation as to how to use CGA in its randomizing solution when
stable storage is not available. The purpose of this document is to
address these issues and to update the current RFC.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute working
documents as Internet-Drafts. The list of current Internet-Drafts is
at http://datatracker.ietf.org/drafts/current.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on Expires: November 14, 2013.
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Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. This document is subject to
BCP 78 and the IETF Trust's Legal Provisions Relating to IETF
Documents (http://trustee.ietf.org/license-info) in effect on the
date of publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Algorithms Overview . . . . . . . . . . . . . . . . . . . . . 4
3.1. Duplicate Address Detection (DAD) Process . . . . . . . . 5
4. Interface ID (IID) generation based on the MAC address . . . 5
5. Lifetime of Interface ID (IID) . . . . . . . . . . . . . . . 5
5.1. Automate the process for setting the lifetime . . . . . . 6
6. Threat Analysis . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Location based tracking . . . . . . . . . . . . . . . . . 6
6.2. Obtaining confidential data . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Privacy and security have a close relationship. Privacy, simply
stated, is the act of allowing a user to choose which data he wants
to make available to others or which data he wants to keep from
others. Security, on the other hand, is the ability to protect your
data or to keep your data confidential. There are times, however,
where one will have to be sacrificed for the sake of the other. The
gathering of location information for security reasons might prove
detrimental to privacy. But in many cases, when cryptography or other
approaches are used to protect the content of the data, you are not
only securing them but also providing privacy.
This document defines the meaning of privacy as it relates to methods
for maintaining our confidential data so that it does not become
available to or is exposed to unscrupulous people who would use it to
harm us or to use it for their ill gains. There is currently only one
solution available in IPv6 autoconfiguration (RFC-4662) which is the,
Privacy Extension [RFC4941]. In the Privacy Extension document two
different approaches are used for IID generation. In the first
approach, the use of stable storage enables it to find which IIDs are
in use and which are in reserve. In the second approach, where stable
storage is not available, it suggests the use of some randomizing
approaches and also comments about other available randomizing
mechanisms such as Cryptographically Generated Addresses (CGA)
[RFC3972] or Dynamic Host Configuration Protocol (DHCPv6). The
Privacy Extension document also referred to the use of named
approaches as a mechanism for greater randomization. Here we offer an
update to section 3.2.2 of RFC 4941 in order to explain how to use
CGA when security is not the issue. An additional update to this RFC
will explain how to maintain the lifetime of the IP address when the
router prefix changes. This is needed because, in this RFC, the key
role is the lifetime of the IID, which might not expire when the
router prefix is changed. This means that the node might not change
its IID when it moves to another network unless the node is rebooted.
This can afford an attacker the ability to track this node, and
obtain enough confidential information about this node, to allow for
further attacks. The third problem occurs if the node responds to the
request from other nodes using the IID generated based on the MAC
address. This could happen if the RFC does not force the node to use
only the IID generated using this approach. The forth problem can
occur when the node cuts current connections to other nodes because
the maximum lifetime for this IID has expired. Finally, a node may
require a large stable storage area in which to store each generated
IID to preclude the use of an already used value. If there is no
stable storage available, the node may not be able to make use of a
greatly randomized IID.
2. Conventions used in this document
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC 2119 significance.
In this document the use of || indicates the concatenation of the
values on either side of the sign.
3. Algorithms Overview
This section explains how to use the modified version of the CGA
algorithm for higher randomization of the IID without the need for
stable storage. This approach is RECOMMENDED and preferable over the
first approach where stable storage is needed. In this approach the
node will not need to maintain a large space.
1. Generate a 16 byte random number called modifier. To generate this
modifier implementations SHOULD use a random seed to aid in the
randomization of this number.
2. Obtain Router prefix from the router advertisement
3. Obtain the nodes' current time and convert it to timestamp. The
timestamp is a 64-bit unsigned integer field containing a timestamp.
The value indicates the number of seconds since January 1, 1970,
00:00 UTC, by using a fixed point format.
4. Concatenate the modifier to the timestamp and router prefix.
R1=(modifier(16 bytes)||timestamp(8 bytes)|| router prefix)
5. Execute SHA2 (256) on the result from step 4.
digest=SHA256(R1)
The use of SHA2 (256) is RECOMMENDED because the chances of finding a
collision are less than when using SHA1 and the generation time is
acceptable (in microseconds using a standard CPU). If, in the future,
a faster and collision free algorithm becomes available, then it
SHOULD be used. It is RECOMMENDED that the implementation be able to
support any new algorithms.
6. Take the 64 leftmost bits from the resulting output from step 5
(SHA2 digest) and set bits u and g (bits 7 and 8) to zero and call
this the IID.
7. Concatenate the IID to the local subnet prefix in order to set the
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local IP address. If the lifetime of the old local address has not
expired, then the node MIGHT skip this step. Otherwise it will
receive a new router prefix.
8. Concatenate the IID to the router subnet prefix (Global subnet
prefix), obtained from the RA message, and set it as a tentative
global IP address. This IP address will become permanent after
Duplicate Address Detection (DAD) processing. This is another update
to RFC 4941. The status of IP addresses in RFC 4941 are temporary
while it SHOULD be permanent with a life time explained in section 4.
3.1. Duplicate Address Detection (DAD) Process
After the DAD process, if the node finds collisions in the network
then the modifier will be incremented and the DAD process will be
repeated. If after 3 times, it receives the same result, it will
consider this an attack and will start using that IP address.
4. Interface ID (IID) generation based on the MAC address
When a node uses the mechanism explained in this document for IID
generation, it MUST not use any other IID generation approaches,
especially those approaches based on MAC addresses. For debugging and
trouble shooting purposes, the implementation MUST provide a means of
partially disabling the mechanism explained in this document.
Allowing for manually setting and unsettling a flag, which would
indicate the debugging mode, is one way to accomplish this. This
means that when this flag is set, the node SHOULD not generate any
new IIDs and SHOULD change the lifetime for this IID to a large
number. As soon as trouble shooting ends and the flag is set back to
zero, then the node MUST generate a new IID and start using it. The
lifetime of the old IID must also be set to an appropriate value at
this time.
5. Lifetime of Interface ID (IID)
One of the problems with the Privacy Extension document as explained
earlier is that the IID might not change when the node joins new
network or receives a new router prefix. Here we update this
document. The router prefix has a higher priority than the IID's
current lifetime. This means that if the node receives new router
prefix while its current IID is still valid, it MUST generate new
randomized IID and start using it. The IIDs MUST only be valid for a
short period of time which will depend on the network policy in
vogue. Any implementations SHOULD provide a means of allowing for
users to change the lifetime default value.
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Another problem that occurs with the use of this Privacy Extension
document is that the node will cut its current connections to the
other nodes using this IID when the maximum lifetime of the IID
expires, The update to that document will state that the node can
maintain its old connections with its old IID for a certain period of
time, but not an indefinite period of time, and it MUST not start any
new connections using the old IID. In cases where the router prefix
changes, the node SHOULD cut the connection. If for any reason there
is a need to maintain the old connections, this document RECOMMENDS
the use of Mobile IPv6 (RFC 6275).
5.1. Automate the process for setting the lifetime
The implementations MIGHT consider an option where the RA messages
update the lifetime of all addresses generated when using this
approach when processing RA messages. This will eliminate the need
for the manual step during installation which sets the default value
of lifetime for any future IIDs generated using this approach based
on network policy. The format for this lifetime value will be the
same as that explained in section 5.3.1 RFC 3971. In this lifetime
option the type for SHOULD be set to next sequential number available
in the SeND options, i.e., 15. This field SHOULD be added to the
ICMPv6 option of RA messages.
6. Threat Analysis
Privacy consists of personal data that is any information relating to
an individual, whether it relates to his or her private, professional
or public life. It can be anything from a name, a photo, an email
address, bank details, his posts on social networking websites, his
medical information, or his computer's IP address. Any unauthorized
efforts to obtain this information is considered an attack against a
user's privacy. The following sections will explain how the mechanism
detailed in this document can protect a user's privacy.
6.1. Location based tracking
As the node MUST keep its IID for only a short period of time, and
MUST also change it when the prefix changes, it is not very easy for
an attacker to track this node based on its IP address. This is also
the case when the node changes the IID within the same network. The
reason for this is because it is very difficult for the attacker to
realize that this node is the same node only with a newly generated
IID. This is especially true when there is an unlimited number of
nodes on the same network.
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6.2. Obtaining confidential data
When a node changes its IID frequently within the network and among
networks, the attacker probably won't have enough time to obtain the
user's confidential data. It will also be difficult for the attacker
to correlate the information that he does obtain to a specific user's
IP address. This means that it will be difficult for the attacker to
obtain more information about this user based on any correlation of
data. An example would be when an attacker obtains a confidential
document from a user but he is unsure about the location of this
user. If the attacker had the location the user, he would be able to
obtain much more information about this use, and then he would be
abler to start the attacks against him. But changing the IID prevents
the attacker from finding the location of this user and thus prevents
further attacks.
7. Security Considerations
As is explained in the Privacy Extension document. the same
approaches are used to maintain security, such as using Secure
Neighbor Discovery (SeND)(RFC-3971) or using a monitoring system
which would inform the administrator of the status of the network and
of any suspended activities in the network.
8. IANA Considerations
-
9. Conclusions
Privacy has become a very important issue in recent years. There is
one solution to the privacy issues, but the current solution has some
deficiencies. The purpose of the current document is to address and
solve the problem which exists with the Privacy Extension document
[RFC4941].
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4291] Hinden, R., Deering, S., "IP Version 6 Addressing
Architecture," RFC 4291, February 2006.
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[RFC3972] Aura, T., "Cryptographically Generated Addresses
(CGA)," RFC 3972, March 2005.
[RFC4941] Narten, T., Draves, R., Krishnan, S., "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T.,
Perkins, C., Carney, M. , " Dynamic Host Configuration
Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
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Authors' Addresses
Hosnieh Rafiee
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
Phone: +49 (0)331-5509-546
Email: ietf@rozanak.com
Dr. Christoph Meinel
(Professor)
Hasso-Plattner-Institute
Prof.-Dr.-Helmert-Str. 2-3
Potsdam, Germany
Email: meinel@hpi.uni-potsdam.de
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