draft-ietf-savi-mix-14.txt   draft-ietf-savi-mix-15.txt 
SAVI J. Bi SAVI J. Bi
Internet-Draft THU Internet-Draft Tsinghua University
Intended status: Standards Track G. Yao Intended status: Standards Track G. Yao
Expires: June 1, 2017 Baidu/THU Expires: July 5, 2017 Tsinghua University/Baidu
J. Halpern J. Halpern
Newbridge Ericsson
E. Levy-Abegnoli, Ed. E. Levy-Abegnoli, Ed.
Cisco Cisco
November 28, 2016 January 1, 2017
SAVI for Mixed Address Assignment Methods Scenario SAVI for Mixed Address Assignment Methods Scenario
draft-ietf-savi-mix-14 draft-ietf-savi-mix-15
Abstract Abstract
In networks that use multiple techniques for address assignment, the In networks that use multiple techniques for address assignment, the
appropriate Source Address Validation Improvement (SAVI) methods must spoofing of addresses assigned by each technique can be prevented
be used to prevent spoofing of addresses assigned by each such using the appropriate Source Address Validation Improvement (SAVI)
technique. This document reviews how multiple SAVI methods can methods. This document reviews how multiple SAVI methods can coexist
coexist in a single SAVI device and collisions are resolved when the in a single SAVI device and collisions are resolved when the same
same binding entry is discovered by two or more methods. binding entry is discovered by two or more methods.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 1, 2017. This Internet-Draft will expire on July 5, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Problem Scope . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Scope . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Recommendations for preventing collisions . . . . . . . . . . 5 5. Recommendations for assignment separation . . . . . . . . . . 5
6. Resolving binding collisions . . . . . . . . . . . . . . . . 6 6. Resolving binding collisions . . . . . . . . . . . . . . . . 6
6.1. Same Address on Different Binding Anchors . . . . . . . . 6 6.1. Same Address on Different Binding Anchors . . . . . . . . 6
6.1.1. Basic preference . . . . . . . . . . . . . . . . . . 6 6.1.1. Basic preference . . . . . . . . . . . . . . . . . . 6
6.1.2. Overwritten preference . . . . . . . . . . . . . . . 7 6.1.2. Exceptions . . . . . . . . . . . . . . . . . . . . . 7
6.1.3. Multiple SAVI Device Scenario . . . . . . . . . . . . 8 6.1.3. Multiple SAVI Device Scenario . . . . . . . . . . . . 8
6.2. Same Address on the Same Binding Anchor . . . . . . . . . 8 6.2. Same Address on the Same Binding Anchor . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 9 10. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9 11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 10 11.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
There are currently several Source Address Validaiton Improvement There are currently several Source Address Validation Improvement
(SAVI) documents ([RFC6620], [RFC7513] and [RFC7219]) that describe (SAVI) documents ([RFC6620], [RFC7513] and [RFC7219]) that describe
the different methods by which a switch can discover and record the different methods by which a switch can discover and record
bindings between a node's IP address and a binding anchor and use bindings between a node's IP address and a binding anchor and use
that binding to perform source address validation. Each of these that binding to perform source address validation. Each of these
documents specifies how to learn on-link addresses, based on the documents specifies how to learn on-link addresses, based on the
technique used for their assignment, respectively: StateLess technique used for their assignment, respectively: StateLess
Autoconfiguration (SLAAC), Dynamic Host Control Protocol (DHCP) and Autoconfiguration (SLAAC), Dynamic Host Control Protocol (DHCP) and
Secure Neighbor Discovery (SeND). Each of these documents describes Secure Neighbor Discovery (SeND). Each of these documents describes
separately how one particular SAVI method deals with address separately how one particular SAVI method deals with address
collisions (same address, different binding anchor). collisions (same address, different binding anchor).
skipping to change at page 3, line 29 skipping to change at page 3, line 29
FCFS[RFC6620] FCFS[RFC6620]
2. Dynamic Host Control Protocol address assignment (DHCP) - 2. Dynamic Host Control Protocol address assignment (DHCP) -
analyzed in SAVI-DHCP[RFC7513] analyzed in SAVI-DHCP[RFC7513]
3. Secure Neighbor Discovery (SeND) address assignment, analyzed in 3. Secure Neighbor Discovery (SeND) address assignment, analyzed in
SAVI-SEND[RFC7219] SAVI-SEND[RFC7219]
In addition, there is a fourth technique for managing (i.e., In addition, there is a fourth technique for managing (i.e.,
creation, management, deletion) a binding on the switch, referred to creation, management, deletion) a binding on the switch, referred to
as "manual". It is based on manual binding configuration and is as "manual". It is based on manual binding configuration. Because
analyzed in [RFC6620] and [RFC7039]. how to manage manual bindings is determined by operators, there is
not a new SAVI method for manual addresses.
All combinations of address assignment techniques can coexist within All combinations of address assignment techniques can coexist within
a layer-2 domain. A SAVI device MUST implement the corresponding a layer-2 domain. A SAVI device MUST implement the corresponding
binding setup methods (referred to as a "SAVI method") for each such binding setup methods (referred to as a "SAVI method") for each such
technique that is in use if it is to provide Source Address technique that is in use if it is to provide Source Address
Validation. Validation.
SAVI methods are normally viewed as independent from each other, each SAVI methods are normally viewed as independent from each other, each
one handling its own entries. If multiple methods are used in the one handling its own entries. If multiple methods are used in the
same device without coordination, each method will attempt to reject same device without coordination, each method will attempt to reject
packets sourced with any addresses that method did not discover. To packets sourced with any addresses that method did not discover. To
prevent addresses discovered by one SAVI method from being filtered prevent addresses discovered by one SAVI method from being filtered
out by another method, the SAVI binding table should be shared by all out by another method, the SAVI binding table SHOULD be shared by all
the SAVI methods in use in the device. This in turn could create the SAVI methods in use in the device. This in turn could create
some conflict when the same entry is discovered by two different some conflict when the same entry is discovered by two different
methods. The purpose of this document is of two folds: provide methods. The purpose of this document is of two folds: provide
recommendations and methods to avoid conflicts, and to resolve recommendations and methods to avoid conflicts, and to resolve
conflicts when they happen. Collisions happening within a given conflicts when they happen. Collisions happening within a given
method are outside the scope of this document. method are outside the scope of this document.
4. Architecture 4. Architecture
A SAVI device may implement ant use multiple SAVI methods. This A SAVI device may implement and use multiple SAVI methods. This
mechanism, called SAVI-MIX, is proposed as a arbiter of the binding mechanism, called SAVI-MIX, is proposed as a arbiter of the binding
generation algorithms from these multiple methods, generating the generation algorithms from these multiple methods, generating the
final binding entries as illustrated in Figure 1. Once a SAVI method final binding entries as illustrated in Figure 1. Once a SAVI method
generates a candidate binding, it will request SAVI-MIX to set up a generates a candidate binding, it will request SAVI-MIX to set up a
corresponding entry in the binding table. Then SAVI-MIX will check corresponding entry in the binding table. Then SAVI-MIX will check
if there is any conflict in the binding table. A new binding will be if there is any conflict in the binding table. A new binding will be
generated if there is no conflict. If there is a conflict, SAVI-MIX generated if there is no conflict. If there is a conflict, SAVI-MIX
will determine whether to replace the existing binding or reject the will determine whether to replace the existing binding or reject the
candidate binding based on the policies specified in Section 6. candidate binding based on the policies specified in Section 6.
skipping to change at page 5, line 39 skipping to change at page 5, line 39
| +--------------+ | | +--------------+ |
| | | |
+--------------------------------------------------------+ +--------------------------------------------------------+
Figure 1: SAVI-Mix Architecture Figure 1: SAVI-Mix Architecture
Each entry in the binding table will contain the following fields: Each entry in the binding table will contain the following fields:
1. IP source address 1. IP source address
2. Binding anchor 2. Binding anchor[RFC7039]
3. Lifetime 3. Lifetime
4. Creation time 4. Creation time
5. Binding methods: the SAVI method used for this entry. 5. Binding methods: the SAVI method used for this entry.
5. Recommendations for preventing collisions 5. Recommendations for assignment separation
If each address assignment technique uses a separate portion of the If each address assignment technique uses a separate portion of the
IP address space, collisions won't happen. Using non overlapping IP address space, collisions won't happen. Using non overlapping
address space across address assignment techniques, and thus across address space across address assignment techniques, and thus across
SAVI methods is therefore recommended. To that end, one should: SAVI methods is therefore recommended. To that end, one should:
1. DHCP/SLAAC: use non-overlapping prefix for DHCP and SLAAC. Set 1. DHCP and SLAAC: use non-overlapping prefix for DHCP and SLAAC.
the A bit in Prefix information option of Router Advertisement Set the A bit in Prefix information option of Router
for SLAAC prefix, and set the M bit in Router Advertisement for Advertisement for SLAAC prefix, and set the M bit in Router
DHCP prefix. For detail explanations on these bits, refer to Advertisement for DHCP prefix. For detail explanations on these
[RFC4861][RFC4862]. bits, refer to [RFC4861][RFC4862].
2. SeND/non-SeND: avoid mixed environment (where SeND and non-SeND 2. SeND and non-SeND: avoid mixed environment (where SeND and non-
nodes are deployed) or separate the prefixes announced to SeND SeND nodes are deployed) or separate the prefixes announced to
and non-SenD nodes. One way to separate the prefixes is to have SeND and non-SenD nodes. One way to separate the prefixes is to
the router(s) announcing different (non-overlapping) prefixes to have the router(s) announcing different (non-overlapping)
SeND and to non-SeND nodes, using unicast Router prefixes to SeND and to non-SeND nodes, using unicast Router
Advertisements[RFC6085], in response to SeND/non-SeND Router Advertisements[RFC6085], in response to SeND/non-SeND Router
Solicit. Solicit.
6. Resolving binding collisions 6. Resolving binding collisions
In situations where collisions can not be avoided by assignment In situations where collisions can not be avoided by assignment
separation, two cases should be considered: separation, two cases should be considered:
1. The same address is bound on two different binding anchors by 1. The same address is bound on two different binding anchors by
different SAVI methods. different SAVI methods.
skipping to change at page 6, line 43 skipping to change at page 6, line 43
This would typically occur in case assignment address spaces could This would typically occur in case assignment address spaces could
not be separated. For instance, an address is assigned by SLAAC on not be separated. For instance, an address is assigned by SLAAC on
node X, installed in the binding table using SAVI-FCFS, anchored to node X, installed in the binding table using SAVI-FCFS, anchored to
"anchor-X". Later, the same address is assigned by DHCP to node Y, "anchor-X". Later, the same address is assigned by DHCP to node Y,
and SAVI-DHCP will generate a candidate binding entry, anchored to and SAVI-DHCP will generate a candidate binding entry, anchored to
"anchor-Y". "anchor-Y".
6.1.1. Basic preference 6.1.1. Basic preference
The SAVI device must decide to whom the address should be bound If there is any manually configured binding, the SAVI device SHOULD
choose the manual configured binding acnhor.
For an address not covered by any manual bindings, the SAVI device
must decide to which binding anchor the address should be bound
(anchor-X or anchor-Y in this example). Current standard documents (anchor-X or anchor-Y in this example). Current standard documents
of address assignment methods have implied the prioritization of address assignment methods have implied the prioritization
relationship based on order in time, i.e., first-come first-served. relationship based on order in time, i.e., first-come first-served.
1. SLAAC: s5.4.5 of [RFC4862] o SLAAC: s5.4.5 of [RFC4862]
2. DHCPv4: s3.1-p5 of [RFC2131] o DHCPv4: s3.1-p5 of [RFC2131]
3. DHCPv6: s18.1.8 of [RFC3315]
4. SeND: s8 of [RFC3971] o DHCPv6: s18.1.8 of [RFC3315]
o SeND: s8 of [RFC3971]
In the absence of any configuration or protocol hint (see In the absence of any configuration or protocol hint (see
Section 6.1.2) the SAVI device should choose the first-come binding Section 6.1.2) the SAVI device SHOULD choose the first-come binding
anchor, whether it was learnt from SLAAC, SeND or DHCP. anchor, whether it was learnt from SLAAC, SeND or DHCP.
6.1.2. Overwritten preference 6.1.2. Exceptions
There are two identified exceptions to the general prioritization There are two identified exceptions to the general prioritization
model, one of them being CGA addresses, another one controlled by the model, one of them being CGA addresses[RFC3971], another one
configuration of the switch. controlled by the configuration of the switch.
6.1.2.1. CGA preference 6.1.2.1. CGA preference
When CGA addresses are used, and a collision is detected, preference When CGA addresses are used, and a collision is detected, preference
should be given to the anchor that carries the CGA credentials once should be given to the anchor that carries the CGA credentials once
they are verified, in particular the CGA parameters and the RSA they are verified, in particular the CGA parameters and the RSA
options. Note that if an attacker was trying to replay CGA options. Note that if an attacker was trying to replay CGA
credentials, he would then compete on the base of "First-Come, First- credentials, he would then compete on the base of "First-Come, First-
Served" (FCFS) principle. Served" (FCFS) principle.
6.1.2.2. configuration preference 6.1.2.2. configuration preference
For configuration driven exceptions, the SAVI device may allow the For configuration driven exceptions, the SAVI device may allow the
configuration of a triplet ("prefix", "anchor", "method") or configuration of a triplet ("prefix", "anchor", "method") or
("address", "anchor", "method"). The "prefix" or "address" ("address", "anchor", "method"). The "prefix" or "address"
represents the address or address prefix to which this preference represents the address or address prefix to which this preference
entry applies. The "anchor" is the value of a know binding anchor entry applies. The "anchor" is the value of a known binding anchor
that this device expects to see using this address or addresses from that this device expects to see using this address or addresses from
this prefix. The "method" is the SAVI method that this device this prefix. The "method" is the SAVI method that this device
expects to use in validating address binding entries from the address expects to use in validating address binding entries from the address
or prefix. At least one of "anchor" and "method" MUST be specified. or prefix. At least one of "anchor" and "method" MUST be specified.
Later, if a DAD message is received with the following conditions Later, if a DAD message [RFC4861] is received with the following
verified: conditions verified:
1. The target in the DAD message does not exist in the binding table 1. The target in the DAD message does not exist in the binding table
2. The target is within configured "prefix" (or equal to "address") 2. The target is within the configured "prefix" (or equal to
"address")
3. The anchor bound to target is different from the configured 3. The anchor bound to target is different from the configured
anchor, when specified anchor, when specified
4. The configured method, if any, is different from SAVI-FCFS 4. The configured method, if any, is different from SAVI-FCFS
The switch should defend the address by responding to the DAD The switch SHOULD defend the address by responding to the DAD
message, with a NA message, on behalf of the target node. The DAD message, with a NA message, on behalf of the target node. It SHOULD
message should be discarded and not forwarded. Forwarding it may NOT install the entry into the binding table. The DAD message SHOULD
cause other SAVI devices to send additional defense NAs. SeND nodes be discarded and not forwarded. Forwarding it may cause other SAVI
in the network MUST disable the option to ignore unsecured devices to send additional defense NAs. SeND nodes in the network
advertisements (see s8 of [RFC3971]). If the option is enabled, the MUST disable the option to ignore unsecured advertisements (see s8 of
case is outside the scope of this document. It is suggested to limit [RFC3971]). If the option is enabled, the case is outside the scope
the rate of defense NAs to reduce security threats to the switch. of this document. It is suggested to limit the rate of defense NAs
to reduce security threats to the switch. Or else, a malicious host
could consume the resource of the switch heavily with flooding DAD
messages.
It should not install the entry into the binding table. It will This will simply prevent the node from assigning the address, and
simply prevent the node to assign the address, and will de-facto will de-facto prioritize the configured anchor. It is especially
prioritize the configured anchor. This is especially useful to useful to protect well known bindings such as a static address of a
protect well known bindings such as a static address of a server over server over anybody, even when the server is down. It is also a way
anybody, even when the server is down. It is also a way to give to give priority to a binding learnt from SAVI-DHCP over a binding
priority to a binding learnt from SAVI-DHCP over a binding for the for the same address, learnt from SAVI-FCFS.
same address, learnt from SAVI-FCFS.
6.1.3. Multiple SAVI Device Scenario 6.1.3. Multiple SAVI Device Scenario
A single SAVI device doesn't have the information of all bound A single SAVI device doesn't have the information of all bound
addresses on the perimeter. Therefore it is not enough to lookup addresses on the perimeter. Therefore it is not enough to lookup
local bindings to identify a collision. However, assuming DAD is local bindings to identify a collision. However, assuming DAD is
performed throughout the security perimeter for all addresses performed throughout the security perimeter for all addresses
regardless of the assignment method, then DAD response will inform regardless of the assignment method, then DAD response will inform
all SAVI devices about any collision. In that case, FCFS will apply all SAVI devices about any collision. In that case, "First-Come,
the same way as in a single switch scenario. If the admin configured First- Served" will apply the same way as in a single switch
on one the switches a prefix (or a single static binding) to defend, scenario. If the admin configured on one the switches a prefix (or a
the DAD response generated by this switch will also prevent the single static binding) to defend, the DAD response generated by this
binding to be installed on other switches of the perimeter. The SAVI switch will also prevent the binding to be installed on other
MIX preferences of all the SAVI devices in the same layer-2 domain switches of the perimeter. The SAVI MIX preferences of all the SAVI
should be consistent. Inconsistent configurations may cause network devices in the same layer-2 domain should be consistent.
breaks. Inconsistent configurations may cause network breaks.
6.2. Same Address on the Same Binding Anchor 6.2. Same Address on the Same Binding Anchor
A binding may be set up on the same binding anchor by multiple A binding may be set up on the same binding anchor by multiple
methods, typically SAVI-FCFS and SAVI-DHCP. If the binding lifetimes methods, typically SAVI-FCFS and SAVI-DHCP. If the binding lifetimes
obtained from the two methods are different, priority should be given obtained from the two methods are different, priority should be given
to 1) Manual configuration 2) SAVI-DHCP 3) SAVI-FCFS as the least to 1) Manual configuration 2) SAVI-DHCP 3) SAVI-FCFS as the least
authoritative. The binding will be removed when the prioritized authoritative. The binding will be removed when the prioritized
lifetime expires, even if a less authoritative method had a longer lifetime expires, even if a less authoritative method had a longer
lifetime. lifetime.
skipping to change at page 9, line 16 skipping to change at page 9, line 24
will be the sum of the rates of all enabled SAVI methods. will be the sum of the rates of all enabled SAVI methods.
Implementers must take these added resource requirements into Implementers must take these added resource requirements into
account. Second, because SAVI MIX supports multiple binding account. Second, because SAVI MIX supports multiple binding
mechanisms, it potentially reduces the security level to that of the mechanisms, it potentially reduces the security level to that of the
weakest supported method, unless additional steps (e.g. requiring weakest supported method, unless additional steps (e.g. requiring
non-overlapping address spaces for different methods) are taken. non-overlapping address spaces for different methods) are taken.
8. Privacy Considerations 8. Privacy Considerations
When implementing multiple SAVI methods, privacy considerations of When implementing multiple SAVI methods, privacy considerations of
all methods apply cumulatively. In addition, there is a minor all methods apply cumulatively.
additional loss of privacy in that the SAVI device can correlate
information from different SAVI methods.
9. IANA Considerations 9. IANA Considerations
This memo asks the IANA for no new parameters. This memo asks the IANA for no new parameters.
10. Acknowledgment 10. Acknowledgment
Thanks to Christian Vogt, Eric Nordmark, Marcelo Bagnulo Braun, David Thanks to Christian Vogt, Eric Nordmark, Marcelo Bagnulo Braun, David
Lamparter, Scott G. Kelly and Jari Arkko for their valuable Lamparter, Scott G. Kelly and Jari Arkko for their valuable
contributions. contributions.
skipping to change at page 10, line 44 skipping to change at page 11, line 4
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>. <http://www.rfc-editor.org/info/rfc4862>.
[RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
"Source Address Validation Improvement (SAVI) Framework", "Source Address Validation Improvement (SAVI) Framework",
RFC 7039, DOI 10.17487/RFC7039, October 2013, RFC 7039, DOI 10.17487/RFC7039, October 2013,
<http://www.rfc-editor.org/info/rfc7039>. <http://www.rfc-editor.org/info/rfc7039>.
Authors' Addresses Authors' Addresses
Jun Bi Jun Bi
Tsinghua University Tsinghua University
Network Research Center, Tsinghua University Network Research Center, Tsinghua University
Beijing 100084 Beijing 100084
China China
EMail: junbi@tsinghua.edu.cn EMail: junbi@tsinghua.edu.cn
Guang Yao Guang Yao
Baidu/Tsinghua University Tsinghua University/Baidu
Baidu Science and Technology Park, Building 1 Baidu Science and Technology Park, Building 1
Beijing 100193 Beijing 100193
China China
EMail: yaoguang.china@gmail.com EMail: yaoguang.china@gmail.com
Joel M. Halpern Joel M. Halpern
Newbridge Networks Inc Ericsson
EMail: jmh@joelhalpern.com EMail: joel.halpern@ericsson.com
Eric Levy-Abegnoli (editor) Eric Levy-Abegnoli (editor)
Cisco Systems Cisco Systems
Village d'Entreprises Green Side - 400, Avenue Roumanille Village d'Entreprises Green Side - 400, Avenue Roumanille
Biot-Sophia Antipolis 06410 Biot-Sophia Antipolis 06410
France France
EMail: elevyabe@cisco.com EMail: elevyabe@cisco.com
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