Internet DRAFT - draft-osterweil-dane-ipsec
draft-osterweil-dane-ipsec
DANE E. Osterweil
Internet-Draft G. Wiley
Intended status: Standards Track T. Okubo
Expires: January 7, 2016 R. Lavu
A. Mohaisen
VeriSign, Inc.
July 6, 2015
Opportunistic Encryption with DANE Semantics and IPsec: IPSECA
draft-osterweil-dane-ipsec-03
Abstract
This document defines a new Domain Name System (DNS) resource record
type called the IPSECA RR that is used to associate an X.509
certificate or a public key to an Internet Protocol Security (IPsec)
gateway in a similar manner TLSA RR is used in the DNS-based
Authentication of Named Entities (DANE) protocol does that for
Transport Layer Security (TLS) in order to make the credential
discovery easier through DNS and to allow credential discovery to be
performed in a secure manner leveraging DNS Security Extensions
(DNSSEC). Among the issues addressed in this draft is the danger of
IP address spoofing that can be a liability to IPsec endpoints. It
is important to note that the "right destination" in this document is
strictly defined by the response of the DNS and does not attest to
the identity of the organization or the ownership of the IP address
space. The identity of the organization shall be attested in an
X.509 certificate issued by a certification authority if desired and
the ownership of the IP address space shall be attested by other
mechanisms such as Towards A Secure Routing System (TASRS)
architecture or Resource Public Key Infrastructure (RPKI).
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."
Osterweil, et al. Expires January 7, 2016 [Page 1]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
This Internet-Draft will expire on January 7, 2016.
Copyright Notice
Copyright (c) 2015 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
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Osterweil, et al. Expires January 7, 2016 [Page 2]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. What IPSECA Adds to DNSSEC Transactions . . . . . . . . . 5
1.2. IP-Centric IPsec Tunnel Discovery Using IPSECKEY . . . . . 6
1.3. Service-Centric IPsec Tunnel Discovery Using IPSECA
and DANE . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. The IPSECA Resource Record . . . . . . . . . . . . . . . . . . 8
2.1. IPSECA RDATA Wire Format . . . . . . . . . . . . . . . . . 8
2.1.1. The Usage Field . . . . . . . . . . . . . . . . . . . 8
2.1.2. The Selector Field . . . . . . . . . . . . . . . . . . 9
2.1.3. The Matching Field . . . . . . . . . . . . . . . . . . 9
2.1.4. The Certificate Association Data Field . . . . . . . . 9
2.2. IPSECA RR Presentation Format . . . . . . . . . . . . . . 10
2.3. Domain Names used for IPSEC Records . . . . . . . . . . . 10
2.4. IPSECA RR Examples . . . . . . . . . . . . . . . . . . . . 10
2.4.1. OE to a DNS Name Server Example . . . . . . . . . . . 11
3. Operational Considerations . . . . . . . . . . . . . . . . . . 12
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
5.1. Interactions . . . . . . . . . . . . . . . . . . . . . . . 13
5.2. Last Mile Security Analysis . . . . . . . . . . . . . . . 14
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
7.1. Normative References . . . . . . . . . . . . . . . . . . . 15
7.2. Informative References . . . . . . . . . . . . . . . . . . 16
Appendix A. Name Server OE Configuration Example . . . . . . . . 17
Appendix B. Recursive Resolver OE Configuration Example . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Osterweil, et al. Expires January 7, 2016 [Page 3]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
1. Introduction
This document defines a new Domain Name System (DNS) [RFC1035]
resource record type called the IPSECA RR that is used to associate
an X.509 certificate or a public key to an Internet Protocol Security
(IPsec) gateway in a similar manner TLSA RR is used in the DNS-based
Authentication of Named Entities (DANE) protocol [RFC6698] does that
for Transport Layer Security (TLS) [RFC5248]
The benefit of associating an X.509 certificate or a public key to an
IPsec gateway is twofold. One is to make the credential discovery
easier through DNS: a protocol that is widely adopted throughout the
Internet and mechanism that is publicly available. The other is to
allow credential discovery to be performed in a secure manner
leveraging DNS Security Extensions (DNSSEC) [RFC4033], [RFC4034],
[RFC4035]. DNSSEC protects the authenticity and integrity of the
signed DNS response, which plays an instrumental role in assuring
that the gateway is connecting to the right destination and is using
the the appropriate Internet Key Exchange Protocol Version 2 (IKEv2)
[RFC5996] credentials to establish the tunnel.
It is important to note that the "right destination" in this document
is strictly defined by the response of the DNS and does not attest to
the identity of the organization or the ownership of the IP address
space. The identity of the organization shall be attested in a X.509
certificate issued by a certification authority if desired and the
ownership of the IP address space shall be attested by other
mechanisms such as Towards A Secure Routing System (TASRS) [TASRS]
architecture or Resource Public Key Infrastructure (RPKI) [RFC6810].
In addition to the fact that the combination of DNS and DNSSEC will
provide a secure and robust foundation for IPsec to perform
opportunistic encryption, it also provides an alternative for those
who wish to deploy opportunistic encryption for IPsec but have
difficulty getting the sub-delegation for the reverse DNS. By
removing the obstacle, this mechanism will allow more entities to
effectively and efficiently enable opportunistic encryption for their
IPsec facilities. In other words, IPSECA RR will maximize the "Fax
Effect" for IPsec opportunistic encryption.
This document details the motivation for, the synergy from, and a
protocol to advertise and verify security credentials that can be
used to verify Opportunistic Encryption (OE) IPsec [RFC4301],
[RFC6071] tunnels for DNS transactions. Securing DNS transactions in
this way is both necessary and sufficient for providing
confidentiality of many types of DNS-transaction meta data, which can
betray user privacy. This document details a new DANE-like [RFC6698]
DNS Resource Record (RR) type called IPSECA, and explains how to use
Osterweil, et al. Expires January 7, 2016 [Page 4]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
it to bootstrap entries in IPsec Security Policy Databases (SPDs) and
to subsequently verify Security Associations (SAs) for OE IPsec
tunnels.
1.1. What IPSECA Adds to DNSSEC Transactions
DNSSEC's focus on object level security leaves the types of
protections offered by IPsec unaddressed. Specifically, the way (or
ways) to associate certificate(s) used by IPsec with a DNSSEC-aware
name server need to be codified. This can be especially complicated
if different IPsec certificates need to be discovered for different
services that are running on the same IP address. This can become
complicated if certificates are learned solely by the IP addresses of
networked-services. This gap is inherently overcome during
certificate discovery in DANE protocols by the concept of "Service
Address Records," [I-D.draft-ogud-dane-vocabulary]. These Security
Associations are defined by, and discovered by, domain names rather
than just IP addresses. [RFC6698] standardizes a way for security
associations of certificates to be made with service domains for TLS,
rather than just IP addresses. As one of the underlying facilities
of DANE's approach to certificate verification, this adds a necessary
enhancement to certificate learning in IPsec, over approaches that
are based solely on IP addresses in DNS (such as described in
[RFC4025] and [RFC4322]).
The advantages of using DANE for IPsec OE also include other
simplifications that the DANE protocol inherently offers all of its
protocols. Such as, the automatic de-authorization of certificates
that happens when they are removed from a DNS zone, which may (under
many circumstances) obviate the need for extensive use of revocation
mechanisms (OCSP [RFC6960] or CRL [RFC5280]). Details of these
relative trade offs is described in more detail in [DANE_SATIN12].
Once a certificate is learned from DANE, it should be periodically
rechecked, but without out-of-band maintenance, the association will
remain valid until its X.509 signature (if certain Usage Types that
include PKIX validation are used) expires.
It is also noteworthy that DANE offers flexibility that is not
available in IP-centric certificate discovery and IP-centric OE
[RFC4322], while still being backwards compatible with them. That
is, while users can use IPSECA records to map OE IPsec tunnels to
service names, they can also use IPSECA records in their reverse DNS
zone in a similar fashion to the IPSECKEY [RFC4025] record used in
[RFC4322]. However, while this document illustrates an example usage
of DANE with IPsec OE, any specification for how the IPSECA resource
record MUST get used with OE is beyond the scope of this document.
Osterweil, et al. Expires January 7, 2016 [Page 5]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
1.2. IP-Centric IPsec Tunnel Discovery Using IPSECKEY
In contrast to a DANE-centric discovery, [RFC4025] specifies a DNS
resource record called IPSECKEY. The IPsec certificate learning
described therein prescribes that relying parties learn the intended
usage of IPsec certificates after they locate them in DNS and
retrieve them. The types of information that relying parties learn
from IPSECKEY responses include: precedence, gateway type, algorithm,
gateway, and possibly the public key. After learning the key and
creating the Security Association, the relying party can use
techniques like [RFC4322] to initialize an OE IPsec tunnel.
The inherent key learning and verification technique in [RFC4322] is
based on learning tunnels from IP addresses only (IP-centric).
Because of this technique's focus on IP-centric learning, operational
entities running services on a specific IP address may not have
access to annotate the reverse DNS zone for their services
(especially if they are shared environments). So, this type of OE
may often be a non-starter. One example would be when zones are
hosted and/or served by cloud service providers. In this case,
customers are almost certainly not allowed to annotate the reverse
DNS zone for their providers.
1.3. Service-Centric IPsec Tunnel Discovery Using IPSECA and DANE
The suggested usage of this document is to aid in discovering where
OE IPsec tunnels exist, and to act as an out of band verification
substrate that can validate the certificates received during IPsec
key exchange. For example, if a DNS caching recursive resolver is
configured to attempt OE IPsec tunnels to DNS name servers (using a
specific key exchange protocol, like [RFC5996], etc.), then when it
receives a referral it SHOULD query name servers for corresponding
IPSECA resource records. (we discuss the format of the resource
record and domain names below in Section 2). When an IPSECA record
is discovered by a resolver, that resolver SHOULD follow its
configurations and setup an SPD entry, in order to signal its IPsec
layer to attempt to attempt to establish an SA. Note, this document
does not specify a new, or any modifications to any existing, IPsec
key exchange protocols. Rather, after adding an SPD and a successful
tunnel establishment, the credentials used for the Security
Association with the name server SHOULD be cross-checked with the
IPSECA resource record(s).
We note that simply adding PAD entries with the IPSECA keys and
identifying them with IP addresses so that the traditional IPSEC
implementations work would result in several security issues. In
particular, each zone answering a forward A and IPSEC lookups could
give their keys for an arbitrary IP address that they are bound to,
Osterweil, et al. Expires January 7, 2016 [Page 6]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
allowing to intercept some else's tunnel. To address this issue, we
require that a resource certification mechanisms (such as Towards A
Secure Routing System (TASRS) [TASRS] architecture or Resource Public
Key Infrastructure (RPKI) [RFC6810]) be used. In particular, a
verifiable certification of the association of a resource with an A
record would limit the ability of an adversary from publishing such
answers to an IPSEC lookup. We note that this does not only address
this security issue, but also marginalizes other issues associated
with the many-to-one mapping from DNS domain names to IP addresses.
When using IPSECA resource records to verify OE tunnels, clients MUST
perform full DNSSEC validation of the DNSSEC chain of trust that
leads to IPSECA RRs. As specified in [RFC6698]:
"A [IPSECA] RRSet whose DNSSEC validation state is secure MUST be
used as a certificate association for [IPsec] unless a local
policy would prohibit the use of the specific certificate
association in the secure TLSA RRSet.
If the DNSSEC validation state on the response to the request for
the [IPSECA] RRSet is bogus, this MUST cause IPsec not to be
started or, if the IPsec negotiation is already in progress, MUST
cause the connection to be aborted.
A [IPSECA] RRSet whose DNSSEC validation state is indeterminate or
insecure cannot be used for [IPsec] and MUST be considered
unusable."
This is to ensure that the SPD entries and SA(s) used for tunnels are
fully verified. This verification MAY include local trust anchor
processing, such that local DNSKEY resource records can be used to
verify corresponding RRSIGs. Trust anchors (which may be distributed
during dynamic host configuration) may be useful for bootstrapping.
For example, consider the case where private address space [RFC1918]
is used for internal recursive resolvers. Here, the locally
provisioned DNS names for the private address space (in the reverse
tree) that are secured using DNSSEC MAY use local trust anchors.
That is, if an [RFC1918] address is used internally, the
corresponding domain name MUST also resolve and be verifiable through
DNS and DNSSEC, but a local trust anchor MAY be used to verify
covered RRSIGs. This shifts the onus of securing DNS transactions to
the initial configuration step. The intuition behind this reasons
that if the first (configuration) step was already where the local
resolver was configured, then the security of the DNS transactions
already hinged on learning the valid resolver this way. So, this
step is already used to convey trusted configurations
(bootstrapping). Adversaries attempting to subvert an end host have
only the narrow attack window that is associated with learning
Osterweil, et al. Expires January 7, 2016 [Page 7]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
configurations. In contrast, an insecure DNS resolver offers an
attack window every time it issues or responds to a query. We
discuss this further in Section 5.2.
2. The IPSECA Resource Record
The IPSECA resource record is modeled heavily off of the IPSECKEY RR
[RFC4025], but it differs in significant ways. The format of IPSECA
is harmonized with the architectural direction set by other DANE work
[RFC6698], [I-D.draft-ogud-dane-vocabulary].
2.1. IPSECA RDATA Wire Format
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Usage | Selector | Matching | /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ /
| /
/ Certificate Association Data /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
Figure 1
2.1.1. The Usage Field
The meaning, semantics, and interpretation of the Usage field of the
IPSECA resource record follow the specification described in Section
2.1 of [RFC7218]:
+-------+----------+--------------------------------+-----------+
| Value | Acronym | Short Description | Reference |
+-------+----------+--------------------------------+-----------+
| 0 | PKIX-TA | CA constraint | [RFC6698] |
| 1 | PKIX-EE | Service certificate constraint | [RFC6698] |
| 2 | DANE-TA | Trust anchor assertion | [RFC6698] |
| 3 | DANE-EE | Domain-issued certificate | [RFC6698] |
| 4-254 | | Unassigned | |
| 255 | PrivCert | Reserved for Private Use | [RFC6698] |
+-------+----------+--------------------------------+-----------+
Table 1: TLSA Certificate Usages
Osterweil, et al. Expires January 7, 2016 [Page 8]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
2.1.2. The Selector Field
The meaning, semantics, and interpretation of the Selector field of
the IPSECA resource record follow the specification described in
Section 2.2 of [RFC7218]:
+-------+---------+--------------------------+-----------+
| Value | Acronym | Short Description | Reference |
+-------+---------+--------------------------+-----------+
| 0 | Cert | Full certificate | [RFC6698] |
| 1 | SPKI | SubjectPublicKeyInfo | [RFC6698] |
| 2-254 | | Unassigned | |
| 255 | PrivSel | Reserved for Private Use | [RFC6698] |
+-------+---------+--------------------------+-----------+
Table 2: TLSA Selectors
2.1.3. The Matching Field
The meaning, semantics, and interpretation of the Matching field of
the IPSECA resource record follow the specification described in
Section 2.3 of [RFC7218]:
+-------+-----------+--------------------------+-----------+
| Value | Acronym | Short Description | Reference |
+-------+-----------+--------------------------+-----------+
| 0 | Full | No hash used | [RFC6698] |
| 1 | SHA2-256 | 256 bit hash by SHA2 | [RFC6698] |
| 2 | SHA2-512 | 512 bit hash by SHA2 | [RFC6698] |
| 3-254 | | Unassigned | |
| 255 | PrivMatch | Reserved for Private Use | [RFC6698] |
+-------+-----------+--------------------------+-----------+
Table 3: TLSA Matching Types
2.1.4. The Certificate Association Data Field
The meaning, semantics, and interpretation of the Certificate
Association Data field of the IPSECA resource record follow the
specification of the same field in the TLSA resource record,
described in Section 2.1.4 of [RFC6698]:
"This field specifies the 'certificate association data' to be
matched. These bytes are either raw data (that is, the full
Osterweil, et al. Expires January 7, 2016 [Page 9]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
certificate or its SubjectPublicKeyInfo, depending on the
selector) for matching type 0, or the hash of the raw data for
matching types 1 and 2. The data refers to the certificate in
the association, not to the TLS ASN.1 Certificate object."
2.2. IPSECA RR Presentation Format
</STUBBED OUT SECTION>
2.3. Domain Names used for IPSEC Records
The IPSECA resource record SHOULD be mapped to a domain name that is
intuitive when discovering OE IPsec tunnels for specific services.
The expected procedure for constructing the domain names for IPSECA
records that enable OE for DNS (port 53) are:
1. The left-most label begins with an underscore character (_),
followed by the decimal representation of the port number that
corresponds to the service that should be conducted over IPsec.
For example, the DNS transactions discussed in this document
would result in "_53".
2. Next, the fully qualified domain name [RFC1035] of the service is
appended to the right side. In the case of a DNS name server,
that is its domain name. In the case of a service that is locate
using an IP address, the service address records MUST be its full
reverse octet name (including the appropriate suffix, such as
.in-addr.arpa. for IPv4 addresses and .ip6.arpa for IPv6
addresses).
Any custom configured tunnels and port mappings may result local
policies that use their own domain name format. Such custom OE
tunnels are non-standard, and may not be discoverable by other
relying parties.
2.4. IPSECA RR Examples
Because the IPSECA record is intended to be associated with a Service
Address Records, it can (implicitly) also be associated with an IP
address through the reverse DNS. A few illustrative mappings are
presented here as examples. Note that these domain name / resource
record mappings are not necessarily intended to update the processing
of protocols like IKEv1 [RFC2409], IKEv2 [RFC5996], etc. or other OE
protocols [RFC4322]. Rather, these mappings are intended to serve as
examples of IPsec tunnels, and their proper configuration. Those
mappings MAY be used in verifying Security Associations. However, we
note that a specific protocol to do the verification is beyond the
scope of this document.
Osterweil, et al. Expires January 7, 2016 [Page 10]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
We note that there are several issues associated with using forward
DNS in the following examples. In particular, a malicious actor may
intercept a tunnel by showing a key for an association with an A
record to an arbitrary initiator. We note that this is more of a
foundational problem addressed by Internet Number Resource
Certification. Systems proposed to address this include the Resource
Public Key Infrastructure (RPKI), and others.
2.4.1. OE to a DNS Name Server Example
Suppose a DNS zone example.com is served by the name servers
ns1.example.com and ns2.example.com. If the zone operators want to
advertise their willingness to offer OE to their name servers using
IKEv2 [RFC5996], then the following domain names MUST be placed under
the example.com zone (the contents of the resource records, below,
are exemplary only and MAY have whatever values a zone operator
chooses):
_53.ns1.example.com. IN IPSECA (
0 1 1 edeff39034cd2ee83446633a9fba
d815a579134ecd7636e51af92ec7
207fd490 ) ; Verify IPsec for DNS txns
_53.ns2.example.com. IN IPSECA (
0 1 1 edeff39034cd2ee83446633a9fba
d815a579134ecd7636e51af92ec7
207fd490 ) ; Verify IPsec for DNS txns
This example illustrates how a zone MAY indicate where an SPD entry
and SA establishment endpoints exist for its name servers (note, they
are not required to be the name servers themselves). Here, each name
server is a tunnel end point, and these two name servers are mapped
to service ports for DNS (port 53). The IPSECA records above
indicate that they verify the CA who must have issued the IPsec
certificate used and they represent a SHA256 hash of that
certificate's SPKI.
Alternately, suppose an enterprise wants to configure OE for DNS
transactions between its desktop clients and its recursive resolver.
In this case, if the enterprise has configured their desktop clients
(perhaps through DHCP) to forward their DNS queries to a caching
recursive resolver at the IP address 192.168.1.2, then the following
IPSECA mapping should be placed in an internally managed DNS reverse
zone:
Osterweil, et al. Expires January 7, 2016 [Page 11]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
_53.2.1.168.192.in-addr.arpa. IN IPSECA (
3 0 2 8f6ea3c50b5c488bef74c7c4a17a
24e8b0f4777d13c211a29223b69a
ea7a89184ac4d272a2e3d9760966
fb3f220b39f7fdfb325998289e50
311ce0748f13c1ed ) ; Verify data in IKEv2 SA
This example illustrates how a caching recursive resolver MAY
indicate where it will accept IPsec tunnel establishment and what the
certificate used for a SA should be. Here the DNS service port and
the IPSECA records describe the nature of the authentic certificate
that SHOULD be used in an SA with this endpoint. In this example,
the IPSECA records both specify that a DANE-EE cert should be
expected in an SA with this resolver, and the SHA-512 hash of that
full certificate should match the encoded value in the IPSECA
resource record.
Of note here is that since SAs MAY be identified by domain names
(which map to IP addresses), some IP addresses may host services that
offer IPsec, and some that do not. The IPSECA record allows hosts to
advertise these nuanced configurations in the same way that these
services are discovered (through the DNS itself).
3. Operational Considerations
Scaling IPsec connections to the full capacity that large recursive
resolvers or large authoritative name servers operate at could be
cause for concern. The additional overhead required to establish and
maintain SAs could exceed the provisioning capacity of deployed
systems. However, there are several relevant observations:
1. If a resolver enables OE, but no (or relatively few) name servers
provision IPSECA records, then no IPsec tunnels will be
established, and the load will remain static (or marginally
increase).
2. If an authoritative name server provisions IPSECA record, it will
only result in additional load if querying resolvers are
configured to attempt OE.
3. Using white-listing techniques (such as those used during pilot
deployments of AAAA records) would allow authoritative name
servers to only return IPSECA responses to clients that have been
white-listed. This would allow name servers to control the
amount of IPsec overhead they incur. For the same reason,
resolvers can be configured to only query for IPSECA records from
white-listed name servers.
Osterweil, et al. Expires January 7, 2016 [Page 12]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
4. IANA Considerations
This document uses a new DNS resource record type, called IPSECA.
This resource record will need to have a new value assigned to it.
Current implementations are advised to use a type number TYPE65347.
This document uses the same semantics and values as the TLSA resource
record [RFC6698] for its Usage, Selector, and Matching fields. Any
future use or modification of an IANA registry for that resource
record will have similar effects on this resource record.
5. Security Considerations
This document details some of the benefits of using IPsec OE for DNS
transactions. Such a utility does not reduce the benefits of other
security protections. For example, the object-level security
assurances that are offered by DNSSEC are cooperative with the
session-level security of IPsec. Additional discussions are
available in [IPSEC_APPEAL]. Moreover, the protections described
herein also offer cooperative benefits with higher layer protocol
protections, like TLS [RFC5246]. Any combination of these types of
protections offer both defense-in-depth (securing transactions at
multiple levels) and offer security practitioners a larger mosaic of
security tools from which to construct and maintain their security
postures.
5.1. Interactions
This document requires that all fully qualified domain names
[RFC1035] must be secured by DNSSEC. This includes domains in the
reverse tree of DNS (which represent IP addresses). An important
question in this context is whether an unvalidated IPSECA record
would be better than nothing. In other words, would it be better to
tolerate failed validation or even unsigned (non-DNSSEC) IPSECA
records than to refuse to allow a connection? Permitting the use of
unsigned records introduces a vector for downgrade attacks.
The use of IPSECA resource records does not constitute a source of
information leakage. Rather, it provides a mechanism to help bolster
confidentiality, by obfuscating DNS transactions.
Expressing tunnel endpoints through DNS may allow adversaries a
vehicle to learn where OE is being offered by name servers. However,
OE tunnels to these name servers will only be attempted if querying
resolvers are configured to attempt IPsec. As a result, adversaries
may be able to learn of potential tunnel endpoints, but if they aim
to disrupt active IPsec traffic, they must still observe which
Osterweil, et al. Expires January 7, 2016 [Page 13]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
resolvers are trying to initiate IPsec communications. Therefore,
adversaries would have no greater opportunity to disrupt IPsec
traffic than they already do. They would still begin by (for
example) observing VPN tunnel setup on wireless LANs (such as at
public WiFi hot-spots).
5.2. Last Mile Security Analysis
For the last mile, we define one type of attack as the case where an
adversary intercepts messages that can be undetectably spoofed. For
example, if a zone (like example.com) has deployed DNSSEC, then if an
adversary responds to a DNS query for www.exmaple.com, a validating
DNS resolver should be able to detect the forgery. However, if an
adversary responds to a query that is sent for a non-DNSSEC zone, a
resolver cannot distinguish the spoofed response from an authentic
response. In addition to this, many bootstrapping protocols (such as
DHCP [RFC2131]) represent the first opportunity for an adversary to
disrupt DNS transactions (by subverting the bootstrapping of the
resolver itself on stub-resolvers). Under this model, a DNS stub-
resolver's security posture is enhanced by keeping an adversary's
attack window to the smallest value possible.
Therefore, the attack window offered by DNS clients in a given time
span T is comprised of the set of transactions that bootstrap
configurations W_cfg(T), plus any DNS transactions that are not
verifiable. Of note, however, is that the DNSSEC transactions
between stub-resolvers and recursive resolvers are not protected by
DNSSEC's cryptography. The only indication of protections is a
header bit (the AD bit), which is spoofable. As a result, the attack
window includes all DNS transactions W_rDNS(T).
From this, the attack window can be expressible as:
W(T) = W_cfg(T) + W_rDNS(T)
Of note is that under most circumstances, resolvers issue many more
queries than configuration requests. So,
W_cfg(T) = 1, and W_rDNS(T) >> W_cfg(T).
However, consider the attack window when using OE: {W(T)}. If the
initial configuration includes a DNSKEY trust anchor that can be used
to verify DNSSEC data that corresponds to a resolver's corresponding
reverse zone (i.e., the IPSECA RR under in-addr.arpa or ip6.arpa),
then {W_cfg(T)} = 1 and {W_rDNS(T)} = 0. Therefore, since W_rDNS(T)
>> W_cfg(T) and {W_rDNS(T)} = 0, then by the transitive property,
Osterweil, et al. Expires January 7, 2016 [Page 14]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
W(T) >> {W(T)}.
While this protocol is designed to enable best effort encryption for
IPsec without any prearrangement between entities, this mechanism
does not attempt to provide authentication. Entities that are
security conscious may choose to undergo an authentication and
verification process at a certification authority to obtain a
certificate that attests to the organization's identity. Entities
that are concerned about the IP resource ownership or route origin
may consider adopting an additional mechanism that is designed for
that purpose.
6. Acknowledgements
The editors would like to express their thanks for the early support
and insights given by Danny McPherson.
7. References
7.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC5248] Hansen, T. and J. Klensin, "A Registry for SMTP Enhanced
Mail System Status Codes", BCP 138, RFC 5248, June 2008.
Osterweil, et al. Expires January 7, 2016 [Page 15]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, August 2012.
[RFC6810] Bush, R. and R. Austein, "The Resource Public Key
Infrastructure (RPKI) to Router Protocol", RFC 6810,
January 2013.
[RFC7218] Gudmundsson, O., "Adding Acronyms to Simplify
Conversations about DNS-Based Authentication of Named
Entities (DANE)", RFC 7218, April 2014.
7.2. Informative References
[DANE_SATIN12]
Osterweil, E., Kaliski, B., Larson, M., and D. McPherson,
"Reducing the X.509 Attack Surface with DNSSEC's DANE",
Proceedings of Securing and Trusting Internet Names, SATIN
'12, March 2012.
[I-D.draft-ogud-dane-vocabulary]
Gudmundsson, O., "Harmonizing how applications specify
DANE-like usage", October 2013.
[IPSEC_APPEAL]
Osterweil, E. and D. McPherson, "IPsec's Appeal:
Protecting DNS Under the Covers", Verisign Labs Technical
Report #1130006 Revision 1, January 2013.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, November 1998.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
"DNS Extensions to Support IP Version 6", RFC 3596,
October 2003.
[RFC4025] Richardson, M., "A Method for Storing IPsec Keying
Material in DNS", RFC 4025, March 2005.
[RFC4322] Richardson, M. and D. Redelmeier, "Opportunistic
Encryption using the Internet Key Exchange (IKE)",
RFC 4322, December 2005.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
Osterweil, et al. Expires January 7, 2016 [Page 16]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, September 2010.
[RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and
Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
February 2011.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, June 2013.
[TASRS] Osterweil, E. and D. McPherson, "TASRS: Towards a Secure
Routing System Through Internet Number Resource
Certification", Verisign Labs Technical Report #1130009
Revision 1, February 2013.
Appendix A. Name Server OE Configuration Example
<STUBBED OUT SECTION>
NAME SERVER SIDE
o Config SPD to accept connections from any on port 53 only
o Zones add IPSECA RRs for each NS domain name and configure DNSSEC:
<examples>
RESOLVER SIDE
o resolver processing logic to intercept referrals and look for
IPSECA RR(s).
o When an IPSECA RR is found, create SPD for that IP and port 53.
</STUBBED OUT SECTION>
Appendix B. Recursive Resolver OE Configuration Example
<STUBBED OUT SECTION>
Osterweil, et al. Expires January 7, 2016 [Page 17]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
RESOLVER SIDE
o If public resolver, create SPD entry that only allows IPsec from
port 53. If internal resolver, limit to addresses serviced.
REVERSE DNS ZONE
o Add IPSECA RR(s) and configure DNSSEC
STUB SIDE
o Configure reverse zone DNSKEY (if 1918) as a local TA (such as
over DHCP). Then do onetime DNSSEC validation for fetching IPSECA
RR.
o Tools include dnskey-grab and/or NLnet Labs' xxxxx.
</STUBBED OUT SECTION>
Authors' Addresses
Eric Osterweil
VeriSign, Inc.
Reston, VA
USA
Email: eosterweil@verisign.com
Glen Wiley
VeriSign, Inc.
Reston, VA
USA
Email: gwiley@verisign.com
Tomofumi Okubo
VeriSign, Inc.
Reston, VA
USA
Email: tomokubo@Verisign.com
Osterweil, et al. Expires January 7, 2016 [Page 18]
Internet-Draft OE with DANE and IPsec: IPSECA July 2015
Ramana Lavu
VeriSign, Inc.
Reston, VA
USA
Email: RLavu@verisign.com
Aziz Mohaisen
VeriSign, Inc.
Reston, VA
USA
Email: amohaisen@verisign.com
Osterweil, et al. Expires January 7, 2016 [Page 19]
