draft-ietf-ipsecme-ikev2-null-auth-05.txt   draft-ietf-ipsecme-ikev2-null-auth-06.txt 
Network Working Group V. Smyslov Network Working Group V. Smyslov
Internet-Draft ELVIS-PLUS Internet-Draft ELVIS-PLUS
Intended status: Standards Track P. Wouters Updates: 4301 (if approved) P. Wouters
Expires: September 27, 2015 Red Hat Intended status: Standards Track Red Hat
March 26, 2015 Expires: October 22, 2015 April 20, 2015
The NULL Authentication Method in IKEv2 Protocol The NULL Authentication Method in IKEv2 Protocol
draft-ietf-ipsecme-ikev2-null-auth-05 draft-ietf-ipsecme-ikev2-null-auth-06
Abstract Abstract
This document specifies the NULL Authentication method and the This document specifies the NULL Authentication method and the
ID_NULL Identification Payload ID Type for the IKEv2 Protocol. This ID_NULL Identification Payload ID Type for the IKEv2 Protocol. This
allows two IKE peers to establish single-side authenticated or mutual allows two IKE peers to establish single-side authenticated or mutual
unauthenticated IKE sessions for those use cases where a peer is unauthenticated IKE sessions for those use cases where a peer is
unwilling or unable to authenticate or identify itself. This ensures unwilling or unable to authenticate or identify itself. This ensures
IKEv2 can be used for Opportunistic Security (also known as IKEv2 can be used for Opportunistic Security (also known as
Opportunistic Encryption) to defend against Pervasive Monitoring Opportunistic Encryption) to defend against Pervasive Monitoring
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This Internet-Draft will expire on September 27, 2015. This Internet-Draft will expire on October 22, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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3. Security Considerations . . . . . . . . . . . . . . . . . . . 8 3. Security Considerations . . . . . . . . . . . . . . . . . . . 8
3.1. Audit trail and peer identification . . . . . . . . . . . 8 3.1. Audit trail and peer identification . . . . . . . . . . . 8
3.2. Resource management and robustness . . . . . . . . . . . . 8 3.2. Resource management and robustness . . . . . . . . . . . . 8
3.3. IKE configuration selection . . . . . . . . . . . . . . . 9 3.3. IKE configuration selection . . . . . . . . . . . . . . . 9
3.4. Networking topology changes . . . . . . . . . . . . . . . 9 3.4. Networking topology changes . . . . . . . . . . . . . . . 9
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Normative References . . . . . . . . . . . . . . . . . . . 12 6.1. Normative References . . . . . . . . . . . . . . . . . . . 12
6.2. Informative References . . . . . . . . . . . . . . . . . . 12 6.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Appendix A. Update of PAD processing in RFC4301 . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
The Internet Key Exchange Protocol version 2 (IKEv2), specified in The Internet Key Exchange Protocol version 2 (IKEv2), specified in
[RFC7296], provides a way for two parties to perform an authenticated [RFC7296], provides a way for two parties to perform an authenticated
key exchange. While the authentication methods used by the peers can key exchange. While the authentication methods used by the peers can
be different, there is no method for one or both parties to remain be different, there is no method for one or both parties to remain
unauthenticated and anonymous. This document extends the unauthenticated and anonymous. This document extends the
authentication methods to support unauthenticated and anonymous IKE authentication methods to support unauthenticated and anonymous IKE
sessions. sessions.
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o Two peers without any trust relationship wish to defend against o Two peers without any trust relationship wish to defend against
widespread pervasive monitoring attacks as described in [RFC7258]. widespread pervasive monitoring attacks as described in [RFC7258].
Without a trust relationship, the peers cannot authenticate each Without a trust relationship, the peers cannot authenticate each
other. Opportunistic Security [RFC7435] states that other. Opportunistic Security [RFC7435] states that
unauthenticated encrypted communication is preferred over unauthenticated encrypted communication is preferred over
cleartext communication. The peers want to use IKE to setup an cleartext communication. The peers want to use IKE to setup an
unauthenticated encrypted connection, that gives them protection unauthenticated encrypted connection, that gives them protection
against pervasive monitoring attacks. An attacker that is able against pervasive monitoring attacks. An attacker that is able
and willing to send packets can still launch a Man-in-the-Middle and willing to send packets can still launch a Man-in-the-Middle
attack to obtain access to the decrypted communication. This case attack to obtain a copy of the unencrypted communication. This
uses a fully unauthenticated key exchange. case uses a fully unauthenticated key exchange.
To meet these needs this document introduces the NULL Authentication To meet these needs, this document introduces the NULL Authentication
method, and the ID_NULL ID type. This allows an IKE peer to method, and the ID_NULL ID type. This allows an IKE peer to
explicitly indicate that it is unwilling or unable to certify its explicitly indicate that it is unwilling or unable to certify its
identity. identity.
1.1. Conventions Used in This Document 1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
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2.1. Authentication Payload 2.1. Authentication Payload
NULL Authentication still requires a properly formed AUTH payload to NULL Authentication still requires a properly formed AUTH payload to
be present in the IKE_AUTH exchange messages, as the AUTH payload be present in the IKE_AUTH exchange messages, as the AUTH payload
cryptographically links the IKE_SA_INIT exchange messages with the cryptographically links the IKE_SA_INIT exchange messages with the
other messages sent over this IKE SA. other messages sent over this IKE SA.
When using NULL Authentication, the content of the AUTH payload is When using NULL Authentication, the content of the AUTH payload is
computed using the syntax of pre-shared secret authentication, computed using the syntax of pre-shared secret authentication,
described in Section 2.15 of [RFC7296]. The values SK_pi and SK_pr described in Section 2.15 of [RFC7296]. The value of SK_pi for the
are used as shared secrets for the content of the AUTH payloads initiator and SK_pr for the responder is used as the shared secret
generated by the initiator and the responder respectively. Note that for the content of the AUTH payload. Implementers should note this
this is identical to how the content of the two last AUTH payloads is means that authentication keys used by the two peers are different in
generated for the non-key-generating EAP methods (see Section 2.16 of each direction. This is identical to how the content of the two last
[RFC7296] for details). AUTH payloads is generated for the non-key-generating EAP methods
(see Section 2.16 of [RFC7296] for details).
The IKEv2 Authentication Method value for NULL Authentication is 13. The IKEv2 Authentication Method value for NULL Authentication is 13.
2.2. Identification Payload 2.2. Identification Payload
When a remote peer is not authenticated, any ID presented in the When a remote peer is not authenticated, any ID presented in the
Identification Data field of the ID payload cannot be validated. To Identification Data field of the ID payload cannot be validated. To
avoid the need of sending a bogus ID Type with placeholder data, this avoid the need of sending a bogus ID Type with placeholder data, this
specification defines a new ID Type, ID_NULL. The Identification specification defines a new ID Type, ID_NULL. The Identification
Data field of the ID payload for this ID Type MUST be empty. Data field of the ID payload for this ID Type MUST be empty.
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Implementations should weigh the resource consumption of sending Implementations should weigh the resource consumption of sending
Liveness Checks against the memory usage of possible orphaned IKE Liveness Checks against the memory usage of possible orphaned IKE
SAs. Implementations may choose to handle situations with thousands SAs. Implementations may choose to handle situations with thousands
of unauthenticated IKE SAs differently from situations with very few of unauthenticated IKE SAs differently from situations with very few
such SAs. such SAs.
2.4. Interaction with Peer Authorization Database (PAD) 2.4. Interaction with Peer Authorization Database (PAD)
Section 4.4.3 of [RFC4301] defines the Peer Authorization Database Section 4.4.3 of [RFC4301] defines the Peer Authorization Database
(PAD), which provides the link between Security Policy Database (SPD) (PAD), which provides the link between Security Policy Database (SPD)
and the IKEv2. The PAD contains an ordered list of records, with and the IKEv2. The PAD contains an ordered list of records with
peers' identities along with corresponding authentication data and peers' identities along with corresponding authentication data and
Child SA authorization data. When the IKE SA is being established Child SA authorization data. When the IKE SA is being established
the PAD is consulted to determine how the peer should be the PAD is consulted to determine how the peer should be
authenticated and what Child SAs it is authorized to create. authenticated and what Child SAs it is authorized to create.
When using NULL Authentication, the peer identity is not When using NULL Authentication, the peer identity is not
authenticated and cannot be trusted. If ID_NULL is used with NULL authenticated and cannot be trusted. If ID_NULL is used with NULL
Authentication, there is no ID at all. The processing of PAD Authentication, there is no ID at all. The processing of PAD
described in Section 4.4.3.4 of [RFC4301] must be updated. described in Section 4.4.3 of [RFC4301] is updated for NULL
Authentication as follows.
NULL authentication needs to be added as one of supported NULL authentication is added as one of supported authentication
authentication methods. This method does not have any authentication methods. This method does not have any authentication data. ID_NULL
data. To add support for ID_NULL, it needs to be included into the is included into the list of allowed ID types. The matching rule for
list of ID types, specified in Section 4.4.3.1 of [RFC4301]. The ID_NULL consists only of whether this type is used, i.e. no actual ID
matching rule for ID_NULL consists only of whether this type is used, matching is done, as ID_NULL contains no identity data.
i.e. no actual ID matching is done, as ID_NULL contains no identity
data.
Section 4.4.3.3 of the [RFC4301] describes how the IKE ID is matched When using the NULL authentication method those matching rules MUST
against the SPD entries. When using the NULL authentication method include matching of a new flag in the SPD entry specifying whether
those matching rules MUST include matching of a new flag in the SPD unauthenticated users are allowed to use that entry. I.e. each SPD
entry specifying whether unauthenticated users are allowed to use entry needs to be augmented to have a flag specifying whether it can
that entry. I.e. each SPD entry needs to be augmented to have a flag be used with NULL authentication or not, and only those rules that
specifying whether it can be used with NULL authentication or not, explicitly have that flag turned on can be used with unauthenticated
and only those rules that explictly have that flag turned on can be connections.
used with unauthenticated connections.
The specific updates of text in Section 4.4.3 of [RFC4301] are listed
in Appendix A.
2.5. Traffic Selectors 2.5. Traffic Selectors
Traffic Selectors and narrowing allow two IKE peers to mutually agree Traffic Selectors and narrowing allow two IKE peers to mutually agree
on a traffic range for an IPsec SA. An unauthenticated peer must not on a traffic range for an IPsec SA. An unauthenticated peer must not
be allowed to use this mechanism to steal traffic that an IKE peer be allowed to use this mechanism to steal traffic that an IKE peer
intended to be for another host. This is especially problematic when intended to be for another host. This is especially problematic when
supporting anonymous IKE peers behind NAT, as such IKE peers build an supporting anonymous IKE peers behind NAT, as such IKE peers build an
IPsec SA using their pre-NAT IP address that are different from the IPsec SA using their pre-NAT IP address that are different from the
source IP of their IKE packets. A rogue IKE peer could use malicious source IP of their IKE packets. A rogue IKE peer could use malicious
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all anonymous IKE peers from each other and itself and only allow it all anonymous IKE peers from each other and itself and only allow it
access to itself and possibly its intended network ranges. access to itself and possibly its intended network ranges.
One method to achieve this is to always assign internal IP addresses One method to achieve this is to always assign internal IP addresses
to unauthenticated IKE clients, as described in Section 2.19 of to unauthenticated IKE clients, as described in Section 2.19 of
[RFC7296]. Implementations may also use other techniques, such as [RFC7296]. Implementations may also use other techniques, such as
internal NAT and connection tracking. internal NAT and connection tracking.
Implementations MAY force unauthenticated IKE peers to single host- Implementations MAY force unauthenticated IKE peers to single host-
to-host IPsec SAs. When using IPv6 this is not always possible, so to-host IPsec SAs. When using IPv6 this is not always possible, so
in this case implementations MUST be able to assign full /64 address implementations MUST be able to assign full /64 address block to the
block to the peer as described in [RFC5739], even if it is not peer as described in [RFC5739], even if it is not authenticated.
authenticated.
3. Security Considerations 3. Security Considerations
If authenticated IKE sessions are possible for a certain traffic If authenticated IKE sessions are possible for a certain traffic
selector range between the peers, then unauthenticated IKE SHOULD NOT selector range between the peers, then unauthenticated IKE SHOULD NOT
be allowed for that traffic selector range. When mixing be allowed for that traffic selector range. When mixing
authenticated and unauthenticated IKE with the same peer, policy authenticated and unauthenticated IKE with the same peer, policy
rules should ensure the highest level of security will be used to rules should ensure the highest level of security will be used to
protect the communication between the two peers. See [RFC7435] for protect the communication between the two peers. See [RFC7435] for
details. details.
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becomes unauthenticated. This makes the IKE session vulnerable to becomes unauthenticated. This makes the IKE session vulnerable to
active Man-in-the-Middle Attacks. active Man-in-the-Middle Attacks.
Using an ID Type other than ID_NULL with the NULL Authentication Using an ID Type other than ID_NULL with the NULL Authentication
Method may compromise the client's anonymity in case of an active Method may compromise the client's anonymity in case of an active
MITM attack. MITM attack.
IKE implementations without NULL Authentication have always performed IKE implementations without NULL Authentication have always performed
mutual authentication and were not designed for use with mutual authentication and were not designed for use with
unauthenticated IKE peers. Implementations might have made unauthenticated IKE peers. Implementations might have made
assumptions remote peers are identified. With NULL Authentication assumptions that remote peers are identified. With NULL
these assumptions are no longer valid. Furthermore, the host itself Authentication these assumptions are no longer valid. Furthermore,
might have made trust assumptions or may not be aware of the network the host itself might have made trust assumptions or may not be aware
topology changes that resulted from IPsec SAs from unauthenticated of the network topology changes that resulted from IPsec SAs from
IKE peers. unauthenticated IKE peers.
3.1. Audit trail and peer identification 3.1. Audit trail and peer identification
With NULL Authentication an established IKE session is no longer With NULL Authentication an established IKE session is no longer
guaranteed to provide a verifiable (authenticated) entity known to guaranteed to provide a verifiable (authenticated) entity known to
the system or network. Implementers that implement NULL the system or network. Implementers that implement NULL
Authentication should ensure their implementation does not make any Authentication should ensure their implementation does not make any
assumptions that depend on IKE peers being "friendly", "trusted" or assumptions that depend on IKE peers being "friendly", "trusted" or
"identifiable". "identifiable".
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[AUTOVPN] Sheffer, Y. and Y. Nir, "The AutoVPN Architecture", Work [AUTOVPN] Sheffer, Y. and Y. Nir, "The AutoVPN Architecture", Work
in Progress, draft-sheffer-autovpn-00, February 2014. in Progress, draft-sheffer-autovpn-00, February 2014.
[DDOS-PROTECTION] [DDOS-PROTECTION]
Nir, Y., "Protecting Internet Key Exchange (IKE) Nir, Y., "Protecting Internet Key Exchange (IKE)
Implementations from Distributed Denial of Service Implementations from Distributed Denial of Service
Attacks", draft-ietf-ipsecme-ddos-protection-00 (work in Attacks", draft-ietf-ipsecme-ddos-protection-00 (work in
progress), October 2014. progress), October 2014.
Appendix A. Update of PAD processing in RFC4301
This appendix lists the specific updates of the text in Section 4.4.3
of [RFC4301] that should be followed when implementing NULL
Authentication.
A new item is added to the list of supported ID types in Section
4.4.3.1
o NULL ID (matches ID type only)
and the following text is added at the end of the section:
Added text:
The NULL ID type is defined as having no data. For this name type
the matching function is defined as comparing the ID type only.
A new item is added to the list of authentication data types in
Section 4.4.3.2
- NULL authentication
and the next paragraph is updated as follows:
Old:
For authentication based on an X.509 certificate [...] For
authentication based on a pre-shared secret, the PAD contains the
pre-shared secret to be used by IKE.
New:
For authentication based on an X.509 certificate [...] For
authentication based on a pre-shared secret, the PAD contains the
pre-shared secret to be used by IKE. For NULL authentication the
PAD contains no data.
In addition the following text is added at the end of Section 4.4.3.4
Added text:
When using the NULL authentication method implementations MUST
make sure that they do not mix authenticated and not-authenticated
SPD rules, i.e. implementations need to keep them separately, for
example by adding flag in SPD to tell whether NULL authentication
can be used or not for the entry. I.e. each SPD entry needs to be
augmented to have a flag specifying whether it can be used with
NULL authentication or not, and only those rules that explictly
have that flag set can be used with unauthenticated connections.
Authors' Addresses Authors' Addresses
Valery Smyslov Valery Smyslov
ELVIS-PLUS ELVIS-PLUS
PO Box 81 PO Box 81
Moscow (Zelenograd) 124460 Moscow (Zelenograd) 124460
Russian Federation Russian Federation
Phone: +7 495 276 0211 Phone: +7 495 276 0211
Email: svan@elvis.ru Email: svan@elvis.ru
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