draft-ietf-ipsecme-split-dns-14.txt   draft-ietf-ipsecme-split-dns-15.txt 
Network T. Pauly Network T. Pauly
Internet-Draft Apple Inc. Internet-Draft Apple Inc.
Intended status: Standards Track P. Wouters Intended status: Standards Track P. Wouters
Expires: May 7, 2019 Red Hat Expires: May 26, 2019 Red Hat
November 3, 2018 November 22, 2018
Split DNS Configuration for IKEv2 Split DNS Configuration for IKEv2
draft-ietf-ipsecme-split-dns-14 draft-ietf-ipsecme-split-dns-15
Abstract Abstract
This document defines two Configuration Payload Attribute Types for This document defines two Configuration Payload Attribute Types
the IKEv2 protocol that add support for private DNS domains. These (INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA) for the Internet Key
domains are intended to be resolved using DNS servers reachable Exchange Protocol Version 2 (IKEv2). These payloads add support for
through an IPsec connection, while leaving all other DNS resolution private (internal-only) DNS domains. These domains are intended to
unchanged. This approach of resolving a subset of domains using non- be resolved using non-public DNS servers that are only reachable
public DNS servers is referred to as "Split DNS". through the IPsec connection. DNS resolution for other domains
remains unchanged. These Configuration Payloads only apply to split
tunnel configurations.
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
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 7, 2019. This Internet-Draft will expire on May 26, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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
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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
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Protocol Exchange . . . . . . . . . . . . . . . . . . . . . . 3 2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Configuration Request . . . . . . . . . . . . . . . . . . 4 3. Protocol Exchange . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Configuration Reply . . . . . . . . . . . . . . . . . . . 4 3.1. Configuration Request . . . . . . . . . . . . . . . . . . 5
2.3. Mapping DNS Servers to Domains . . . . . . . . . . . . . 5 3.2. Configuration Reply . . . . . . . . . . . . . . . . . . . 5
2.4. Example Exchanges . . . . . . . . . . . . . . . . . . . . 5 3.3. Mapping DNS Servers to Domains . . . . . . . . . . . . . 6
2.4.1. Simple Case . . . . . . . . . . . . . . . . . . . . . 5 3.4. Example Exchanges . . . . . . . . . . . . . . . . . . . . 6
2.4.2. Requesting Domains and DNSSEC trust anchors . . . . . 6 3.4.1. Simple Case . . . . . . . . . . . . . . . . . . . . . 6
3. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 6 3.4.2. Requesting Domains and DNSSEC trust anchors . . . . . 7
3.1. INTERNAL_DNS_DOMAIN Configuration Attribute Type Request 4. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 7
and Reply . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. INTERNAL_DNS_DOMAIN Configuration Attribute Type Request
3.2. INTERNAL_DNSSEC_TA Configuration Attribute . . . . . . . 7 and Reply . . . . . . . . . . . . . . . . . . . . . . . . 8
4. INTERNAL_DNS_DOMAIN Usage Guidelines . . . . . . . . . . . . 9 4.2. INTERNAL_DNSSEC_TA Configuration Attribute . . . . . . . 8
5. INTERNAL_DNSSEC_TA Usage Guidelines . . . . . . . . . . . . . 10 5. INTERNAL_DNS_DOMAIN Usage Guidelines . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. INTERNAL_DNSSEC_TA Usage Guidelines . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 9.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
Split DNS is a common configuration for secure tunnels, such as Split tunnel Virtual Private Network ("VPN") configurations only send
Virtual Private Networks in which host machines private to an packets with a specific destination IP range, usually chosen from
organization can only be resolved using internal DNS resolvers [RFC1918], via the VPN. All other traffic is not sent via the VPN.
[RFC2775]. In such configurations, it is often desirable to only This allows an enterprise deployment to offer Remote Access VPN
resolve hosts within a set of private domains using the tunnel, while services without needing to accept and forward all the non-enterprise
letting resolutions for public hosts be handled by a device's default related network traffic generated by their remote users. Resources
DNS configuration. within the enterprise can be accessed by the user via the VPN, while
all other traffic generated by the user is not send over the VPN.
The Internet Key Exchange protocol version 2 [RFC7296] negotiates These internal resources tend to only have internal-only DNS names
configuration parameters using Configuration Payload Attribute Types. and require the use of special internal-only DNS servers to get
This document defines two Configuration Payload Attribute Types that resolved. Split DNS [RFC2775] is a common configuration that is part
add support for trusted Split DNS domains. of split tunnel VPN configurations to support configuring Remote
Access users to use these special internal-only domain names.
The INTERNAL_DNS_DOMAIN attribute type is used to convey one or more The IKEv2 protocol [RFC7296] negotiates configuration parameters
DNS domains that MUST be resolved only using the provided DNS using Configuration Payload Attribute Types. This document defines
two Configuration Payload Attribute Types that add support for
trusted Split DNS domains.
The INTERNAL_DNS_DOMAIN attribute type is used to convey that the
specified DNS domain MUST be resolved using the provided DNS
nameserver IP addresses, causing these requests to use the IPsec nameserver IP addresses, causing these requests to use the IPsec
connection. connection.
The INTERNAL_DNSSEC_TA attribute type is used to convey DNSSEC trust The INTERNAL_DNSSEC_TA attribute type is used to convey a DNSSEC
anchors for those domains. trust anchor for such a domain. This is required if the external
view uses DNSSEC that would prove the internal view does not exist or
would expect a different DNSSEC key on the different versions
(internal and external) of the enterprise domain.
When only a subset of traffic is routed into a private network using If an INTERNAL_DNS_DOMAIN is sent by the responder, the responder
an IPsec SA, these Configuration Payload options can be used to MUST also include one or more INTERNAL_IP4_DNS or INTERNAL_IP6_DNS
define which private domains are intended to be resolved through the attributes that contain the IPv4 or IPv6 address of the internal DNS
IPsec connection without affecting the client's global DNS server.
resolution.
For the purposes of this document, DNS resolution servers accessible For the purposes of this document, DNS resolution servers accessible
through an IPsec connection will be referred to as "internal DNS through an IPsec connection will be referred to as "internal DNS
servers", and other DNS servers will be referred to as "external DNS servers", and other DNS servers will be referred to as "external DNS
servers". servers".
A client using these configuration payloads will be able to request
and receive Split DNS configurations using the INTERNAL_DNS_DOMAIN
and INTERNAL_DNSSEC_TA configuration attributes. The client device
can use the internal DNS server(s) for any DNS queries within the
assigned domains. DNS queries for other domains SHOULD be sent to
the regular external DNS server.
Other tunnel-establishment protocols already support the assignment Other tunnel-establishment protocols already support the assignment
of Split DNS domains. For example, there are proprietary extensions of Split DNS domains. For example, there are proprietary extensions
to IKEv1 that allow a server to assign Split DNS domains to a client. to IKEv1 that allow a server to assign Split DNS domains to a client.
However, the IKEv2 standard does not include a method to configure However, the IKEv2 standard does not include a method to configure
this option. This document defines a standard way to negotiate this this option. This document defines a standard way to negotiate this
option for IKEv2. option for IKEv2.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
captials, as shown here. captials, as shown here.
2. Protocol Exchange 2. Applicability
If the negotiated IPsec connection is not a split tunnel
configuration, the INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA
Configuration Payloads MUST be ignored. This prevents generic (non-
enterprise) VPN services from overriding the public DNS hierarchy,
which could lead to malicious overrides of DNS and DNSSEC.
Such configurations SHOULD instead use only the INTERNAL_IP4_DNS and
INTERNAL_IP6_DNS Configuration Payloads to ensure all of the user's
DNS traffic is send through the IPsec connection and does not leak
unencrypted onto the local network, as the local network is often
explicitely exempted from IPsec encryption.
For split tunnel configurations, an enterprise can require one or
more DNS domains to be resolved via internal DNS servers. This can
be a special domain, such as "corp.example.com" for an enterprise
that is publicly known to use "example.com". In this case, the
remote user needs to be informed what the internal-only domain names
are and what the IP addresses of the internal DNS servers are. An
enterprise can also run a different version of its public domain on
its internal network. In that case, the VPN client is instructed to
send DNS queries for the enterprise public domain (eg "example.com")
to the internal DNS servers. A configuration for this deployment
scenario is referred to as a Split DNS configuration.
Split DNS configurations are often preferable to sending all DNS
queries to the enterprise. This allows the remote user to only send
DNS queries for the enterprise to the internal DNS servers. The
enterprise remains unaware of all non-enterprise (DNS) activitiy of
the user. It also allows the enterprise DNS servers to only be
configured for the enterprise DNS domains which removes the legal and
technical responsibility of the enterprise to resolve every DNS
domain potentially asked for by the remote user.
A client using these configuration payloads will be able to request
and receive Split DNS configurations using the INTERNAL_DNS_DOMAIN
and INTERNAL_DNSSEC_TA configuration attributes. These attributes
MUST be accompanied by one or more INTERNAL_IP4_DNS or
INTERNAL_IP6_DNS configuration attributes. The client device can
then use the internal DNS server(s) for any DNS queries within the
assigned domains. DNS queries for other domains MUST be sent to the
regular DNS service of the client.
3. Protocol Exchange
In order to negotiate which domains are considered internal to an In order to negotiate which domains are considered internal to an
IKEv2 tunnel, initiators indicate support for Split DNS in their IKEv2 tunnel, initiators indicate support for Split DNS in their
CFG_REQUEST payloads, and responders assign internal domains (and CFG_REQUEST payloads, and responders assign internal domains (and
DNSSEC trust anchors) in their CFG_REPLY payloads. When Split DNS DNSSEC trust anchors) in their CFG_REPLY payloads. When Split DNS
has been negotiated, the existing DNS server configuration attributes has been negotiated, the existing DNS server configuration attributes
will be interpreted as internal DNS servers that can resolve will be interpreted as internal DNS servers that can resolve
hostnames within the internal domains. hostnames within the internal domains.
2.1. Configuration Request 3.1. Configuration Request
To indicate support for Split DNS, an initiator includes one more To indicate support for Split DNS, an initiator includes one more
INTERNAL_DNS_DOMAIN attributes as defined in Section 3 as part of the INTERNAL_DNS_DOMAIN attributes as defined in Section 4 as part of the
CFG_REQUEST payload. If an INTERNAL_DNS_DOMAIN attribute is included CFG_REQUEST payload. If an INTERNAL_DNS_DOMAIN attribute is included
in the CFG_REQUEST, the initiator MUST also include one or more in the CFG_REQUEST, the initiator MUST also include one or more
INTERNAL_IP4_DNS and INTERNAL_IP6_DNS attributes in the CFG_REQUEST. INTERNAL_IP4_DNS and INTERNAL_IP6_DNS attributes in the CFG_REQUEST.
The INTERNAL_DNS_DOMAIN attribute sent by the initiator is usually The INTERNAL_DNS_DOMAIN attribute sent by the initiator is usually
empty but MAY contain a suggested domain name. empty but MAY contain a suggested domain name.
The absence of INTERNAL_DNS_DOMAIN attributes in the CFG_REQUEST The absence of INTERNAL_DNS_DOMAIN attributes in the CFG_REQUEST
payload indicates that the initiator does not support or is unwilling payload indicates that the initiator does not support or is unwilling
to accept Split DNS configuration. to accept Split DNS configuration.
To indicate support for DNSSEC, an initiator includes one or more To indicate support for DNSSEC, an initiator includes one or more
INTERNAL_DNSSEC_TA attributes as defined in Section 3 as part of the INTERNAL_DNSSEC_TA attributes as defined in Section 4 as part of the
CFG_REQUEST payload. If an INTERNAL_DNSSEC_TA attribute is included CFG_REQUEST payload. If an INTERNAL_DNSSEC_TA attribute is included
in the CFG_REQUEST, the initiator MUST also include one or more in the CFG_REQUEST, the initiator MUST also include one or more
INTERNAL_DNS_DOMAIN attributes in the CFG_REQUEST. If the initiator INTERNAL_DNS_DOMAIN attributes in the CFG_REQUEST. If the initiator
includes an INTERNAL_DNSSEC_TA attribute, but does not inclue an includes an INTERNAL_DNSSEC_TA attribute, but does not inclue an
INTERNAL_DNS_DOMAIN attribute, the responder MAY still respond with INTERNAL_DNS_DOMAIN attribute, the responder MAY still respond with
both INTERNAL_DNSSEC_TA and INTERNAL_DNS_DOMAIN attributes. both INTERNAL_DNSSEC_TA and INTERNAL_DNS_DOMAIN attributes.
An initiator MAY convey its current DNSSEC trust anchors for the An initiator MAY convey its current DNSSEC trust anchors for the
domain specified in the INTERNAL_DNS_DOMAIN attribute. If it does domain specified in the INTERNAL_DNS_DOMAIN attribute. If it does
not wish to convey this information, it MUST use a length of 0. not wish to convey this information, it MUST use a length of 0.
The absence of INTERNAL_DNSSEC_TA attributes in the CFG_REQUEST The absence of INTERNAL_DNSSEC_TA attributes in the CFG_REQUEST
payload indicates that the initiator does not support or is unwilling payload indicates that the initiator does not support or is unwilling
to accept DNSSEC trust anchor configuration. to accept DNSSEC trust anchor configuration.
2.2. Configuration Reply 3.2. Configuration Reply
Responders MAY send one or more INTERNAL_DNS_DOMAIN attributes in Responders MAY send one or more INTERNAL_DNS_DOMAIN attributes in
their CFG_REPLY payload. If an INTERNAL_DNS_DOMAIN attribute is their CFG_REPLY payload. If an INTERNAL_DNS_DOMAIN attribute is
included in the CFG_REPLY, the responder MUST also include one or included in the CFG_REPLY, the responder MUST also include one or
both of the INTERNAL_IP4_DNS and INTERNAL_IP6_DNS attributes in the both of the INTERNAL_IP4_DNS and INTERNAL_IP6_DNS attributes in the
CFG_REPLY. These DNS server configurations are necessary to define CFG_REPLY. These DNS server configurations are necessary to define
which servers can receive queries for hostnames in internal domains. which servers can receive queries for hostnames in internal domains.
If the CFG_REQUEST included an INTERNAL_DNS_DOMAIN attribute, but the If the CFG_REQUEST included an INTERNAL_DNS_DOMAIN attribute, but the
CFG_REPLY does not include an INTERNAL_DNS_DOMAIN attribute, the CFG_REPLY does not include an INTERNAL_DNS_DOMAIN attribute, the
initiator MUST behave as if Split DNS configurations are not initiator MUST behave as if Split DNS configurations are not
skipping to change at page 5, line 20 skipping to change at page 6, line 20
suggestion by the responder. suggestion by the responder.
For each DNS domain specified in an INTERNAL_DNS_DOMAIN attribute, For each DNS domain specified in an INTERNAL_DNS_DOMAIN attribute,
one or more INTERNAL_DNSSEC_TA attributes MAY be included by the one or more INTERNAL_DNSSEC_TA attributes MAY be included by the
responder. This attribute lists the corresponding internal DNSSEC responder. This attribute lists the corresponding internal DNSSEC
trust anchor in the DNS presentation format of a DS record as trust anchor in the DNS presentation format of a DS record as
specified in [RFC4034]. The INTERNAL_DNSSEC_TA attribute MUST specified in [RFC4034]. The INTERNAL_DNSSEC_TA attribute MUST
immediately follow the INTERNAL_DNS_DOMAIN attribute that it applies immediately follow the INTERNAL_DNS_DOMAIN attribute that it applies
to. to.
2.3. Mapping DNS Servers to Domains 3.3. Mapping DNS Servers to Domains
All DNS servers provided in the CFG_REPLY MUST support resolving All DNS servers provided in the CFG_REPLY MUST support resolving
hostnames within all INTERNAL_DNS_DOMAIN domains. In other words, hostnames within all INTERNAL_DNS_DOMAIN domains. In other words,
the INTERNAL_DNS_DOMAIN attributes in a CFG_REPLY payload form a the INTERNAL_DNS_DOMAIN attributes in a CFG_REPLY payload form a
single list of Split DNS domains that applies to the entire list of single list of Split DNS domains that applies to the entire list of
INTERNAL_IP4_DNS and INTERNAL_IP6_DNS attributes. INTERNAL_IP4_DNS and INTERNAL_IP6_DNS attributes.
2.4. Example Exchanges 3.4. Example Exchanges
2.4.1. Simple Case 3.4.1. Simple Case
In this example exchange, the initiator requests INTERNAL_IP4_DNS and In this example exchange, the initiator requests INTERNAL_IP4_DNS and
INTERNAL_DNS_DOMAIN attributes in the CFG_REQUEST, but does not INTERNAL_DNS_DOMAIN attributes in the CFG_REQUEST, but does not
specify any value for either. This indicates that it supports Split specify any value for either. This indicates that it supports Split
DNS, but has no preference for which DNS requests will be routed DNS, but has no preference for which DNS requests will be routed
through the tunnel. through the tunnel.
The responder replies with two DNS server addresses, and two internal The responder replies with two DNS server addresses, and two internal
domains, "example.com" and "city.other.com". domains, "example.com" and "city.other.test".
Any subsequent DNS queries from the initiator for domains such as Any subsequent DNS queries from the initiator for domains such as
"www.example.com" SHOULD use 198.51.100.2 or 198.51.100.4 to resolve. "www.example.com" SHOULD use 198.51.100.2 or 198.51.100.4 to resolve.
CP(CFG_REQUEST) = CP(CFG_REQUEST) =
INTERNAL_IP4_ADDRESS() INTERNAL_IP4_ADDRESS()
INTERNAL_IP4_DNS() INTERNAL_IP4_DNS()
INTERNAL_DNS_DOMAIN() INTERNAL_DNS_DOMAIN()
CP(CFG_REPLY) = CP(CFG_REPLY) =
INTERNAL_IP4_ADDRESS(198.51.100.234) INTERNAL_IP4_ADDRESS(198.51.100.234)
INTERNAL_IP4_DNS(198.51.100.2) INTERNAL_IP4_DNS(198.51.100.2)
INTERNAL_IP4_DNS(198.51.100.4) INTERNAL_IP4_DNS(198.51.100.4)
INTERNAL_DNS_DOMAIN(example.com) INTERNAL_DNS_DOMAIN(example.com)
INTERNAL_DNS_DOMAIN(city.other.com) INTERNAL_DNS_DOMAIN(city.other.test)
2.4.2. Requesting Domains and DNSSEC trust anchors 3.4.2. Requesting Domains and DNSSEC trust anchors
In this example exchange, the initiator requests INTERNAL_IP4_DNS, In this example exchange, the initiator requests INTERNAL_IP4_DNS,
INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA attributes in the INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA attributes in the
CFG_REQUEST. CFG_REQUEST.
Any subsequent DNS queries from the initiator for domains such as Any subsequent DNS queries from the initiator for domains such as
"www.example.com" or "city.other.com" would be DNSSEC validated using "www.example.com" or "city.other.test" would be DNSSEC validated
the DNSSEC trust anchor received in the CFG_REPLY. using the DNSSEC trust anchor received in the CFG_REPLY.
In this example, the initiator has no existing DNSSEC trust anchors In this example, the initiator has no existing DNSSEC trust anchors
would the requested domain. the "example.com" dommain has DNSSEC would the requested domain. the "example.com" dommain has DNSSEC
trust anchors that are returned, while the "other.com" domain has no trust anchors that are returned, while the "other.test" domain has no
DNSSEC trust anchors. DNSSEC trust anchors.
CP(CFG_REQUEST) = CP(CFG_REQUEST) =
INTERNAL_IP4_ADDRESS() INTERNAL_IP4_ADDRESS()
INTERNAL_IP4_DNS() INTERNAL_IP4_DNS()
INTERNAL_DNS_DOMAIN() INTERNAL_DNS_DOMAIN()
INTERNAL_DNSSEC_TA() INTERNAL_DNSSEC_TA()
CP(CFG_REPLY) = CP(CFG_REPLY) =
INTERNAL_IP4_ADDRESS(198.51.100.234) INTERNAL_IP4_ADDRESS(198.51.100.234)
INTERNAL_IP4_DNS(198.51.100.2) INTERNAL_IP4_DNS(198.51.100.2)
INTERNAL_IP4_DNS(198.51.100.4) INTERNAL_IP4_DNS(198.51.100.4)
INTERNAL_DNS_DOMAIN(example.com) INTERNAL_DNS_DOMAIN(example.com)
INTERNAL_DNSSEC_TA(43547,8,1,B6225AB2CC613E0DCA7962BDC2342EA4...) INTERNAL_DNSSEC_TA(43547,8,1,B6225AB2CC613E0DCA7962BDC2342EA4...)
INTERNAL_DNSSEC_TA(31406,8,2,F78CF3344F72137235098ECBBD08947C...) INTERNAL_DNSSEC_TA(31406,8,2,F78CF3344F72137235098ECBBD08947C...)
INTERNAL_DNS_DOMAIN(city.other.com) INTERNAL_DNS_DOMAIN(city.other.test)
3. Payload Formats 4. Payload Formats
All multi-octet fields representing integers are laid out in big All multi-octet fields representing integers are laid out in big
endian order (also known as "most significant byte first", or endian order (also known as "most significant byte first", or
"network byte order"). "network byte order").
3.1. INTERNAL_DNS_DOMAIN Configuration Attribute Type Request and Reply 4.1. INTERNAL_DNS_DOMAIN Configuration Attribute Type Request and Reply
1 2 3 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 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
+-+-----------------------------+-------------------------------+ +-+-----------------------------+-------------------------------+
|R| Attribute Type | Length | |R| Attribute Type | Length |
+-+-----------------------------+-------------------------------+ +-+-----------------------------+-------------------------------+
| | | |
~ Domain Name in DNS presentation format ~ ~ Domain Name in DNS presentation format ~
| | | |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
skipping to change at page 7, line 29 skipping to change at page 8, line 29
o Attribute Type (15 bits) set to value 25 for INTERNAL_DNS_DOMAIN. o Attribute Type (15 bits) set to value 25 for INTERNAL_DNS_DOMAIN.
o Length (2 octets) - Length of domain name. o Length (2 octets) - Length of domain name.
o Domain Name (0 or more octets) - A Fully Qualified Domain Name o Domain Name (0 or more octets) - A Fully Qualified Domain Name
used for Split DNS rules, such as "example.com", in DNS used for Split DNS rules, such as "example.com", in DNS
presentation format and optionally using IDNA [RFC5890] for presentation format and optionally using IDNA [RFC5890] for
Internationalized Domain Names. Implementors need to be careful Internationalized Domain Names. Implementors need to be careful
that this value is not null-terminated. that this value is not null-terminated.
3.2. INTERNAL_DNSSEC_TA Configuration Attribute 4.2. INTERNAL_DNSSEC_TA Configuration Attribute
An INTERNAL_DNSSEC_TA Configuration Attribute can either be empty, or An INTERNAL_DNSSEC_TA Configuration Attribute can either be empty, or
it can contain one Trust Anchor by containing a non-zero Length with it can contain one Trust Anchor by containing a non-zero Length with
a DNSKEY Key Tag, DNSKEY Algorithm, Digest Type and Digest Data a DNSKEY Key Tag, DNSKEY Algorithm, Digest Type and Digest Data
fields. fields.
An empty INTERNAL_DNSSEC_TA CFG attribute: An empty INTERNAL_DNSSEC_TA CFG attribute:
1 2 3 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 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
skipping to change at page 9, line 5 skipping to change at page 10, line 5
Each INTERNAL_DNSSEC_TA attribute in the CFG_REPLY payload MUST Each INTERNAL_DNSSEC_TA attribute in the CFG_REPLY payload MUST
immediately follow a corresponding INTERNAL_DNS_DOMAIN attribute. As immediately follow a corresponding INTERNAL_DNS_DOMAIN attribute. As
the INTERNAL_DNSSEC_TA format itself does not contain the domain the INTERNAL_DNSSEC_TA format itself does not contain the domain
name, it relies on the preceding INTERNAL_DNS_DOMAIN to provide the name, it relies on the preceding INTERNAL_DNS_DOMAIN to provide the
domain for which it specifies the trust anchor. Any domain for which it specifies the trust anchor. Any
INTERNAL_DNSSEC_TA attribute that is not immediately preceded by an INTERNAL_DNSSEC_TA attribute that is not immediately preceded by an
INTERNAL_DNS_DOMAIN or another INTERNAL_DNSSEC_TA attribute applying INTERNAL_DNS_DOMAIN or another INTERNAL_DNSSEC_TA attribute applying
to the same domain name MUST be ignored and treated as a protocol to the same domain name MUST be ignored and treated as a protocol
error. error.
4. INTERNAL_DNS_DOMAIN Usage Guidelines 5. INTERNAL_DNS_DOMAIN Usage Guidelines
If a CFG_REPLY payload contains no INTERNAL_DNS_DOMAIN attributes, If a CFG_REPLY payload contains no INTERNAL_DNS_DOMAIN attributes,
the client MAY use the provided INTERNAL_IP4_DNS or INTERNAL_IP6_DNS the client MAY use the provided INTERNAL_IP4_DNS or INTERNAL_IP6_DNS
servers as the default DNS server(s) for all queries. servers as the default DNS server(s) for all queries.
If a client is configured by local policy to only accept a limited If a client is configured by local policy to only accept a limited
number of INTERNAL_DNS_DOMAIN values, the client MUST ignore any number of INTERNAL_DNS_DOMAIN values, the client MUST ignore any
other INTERNAL_DNS_DOMAIN values. other INTERNAL_DNS_DOMAIN values.
For each INTERNAL_DNS_DOMAIN entry in a CFG_REPLY payload that is not For each INTERNAL_DNS_DOMAIN entry in a CFG_REPLY payload that is not
prohibited by local policy, the client MUST use the provided prohibited by local policy, the client MUST use the provided
INTERNAL_IP4_DNS or INTERNAL_IP6_DNS DNS servers as the only INTERNAL_IP4_DNS or INTERNAL_IP6_DNS DNS servers as the only
resolvers for the listed domains and its sub-domains and it MUST NOT resolvers for the listed domains and its sub-domains and it MUST NOT
attempt to resolve the provided DNS domains using its external DNS attempt to resolve the provided DNS domains using its external DNS
servers. Other domain names SHOULD be resolved using some other servers. Other domain names SHOULD be resolved using some other
external DNS resolver(s), configured independently from IKE. Queries external DNS resolver(s), configured independently from IKE. Queries
for these other domains MAY be sent to the internal DNS resolver(s) for these other domains MAY be sent to the internal DNS resolver(s)
listed in that CFG_REPLY message, but have no guarantee of being listed in that CFG_REPLY message, but have no guarantee of being
answered. For example, if the INTERNAL_DNS_DOMAIN attribute answered. For example, if the INTERNAL_DNS_DOMAIN attribute
specifies "example.com", then "example.com", "www.example.com" and specifies "example.test", then "example.test", "www.example.test" and
"mail.eng.example.com" MUST be resolved using the internal DNS "mail.eng.example.test" MUST be resolved using the internal DNS
resolver(s), but "anotherexample.com" and "ample.com" SHOULD NOT be resolver(s), but "otherexample.test" and "ple.test" MUST NOT be
resolved using the internal resolver and SHOULD use the system's resolved using the internal resolver and MUST use the system's
external DNS resolver(s). external DNS resolver(s).
The initiator SHOULD allow the DNS domains listed in the The initiator SHOULD allow the DNS domains listed in the
INTERNAL_DNS_DOMAIN attributes to resolve to special IP address INTERNAL_DNS_DOMAIN attributes to resolve to special IP address
ranges, such as those of [RFC1918], even if the initiator host is ranges, such as those of [RFC1918], even if the initiator host is
otherwise configured to block DNS answer containing these special IP otherwise configured to block DNS answer containing these special IP
addresses. address ranges.
When an IKE SA is terminated, the DNS forwarding MUST be When an IKE SA is terminated, the DNS forwarding MUST be
unconfigured. This includes deleting the DNS forwarding rules; unconfigured. This includes deleting the DNS forwarding rules;
flushing all cached data for DNS domains provided by the flushing all cached data for DNS domains provided by the
INTERNAL_DNS_DOMAIN attribute, including negative cache entries; INTERNAL_DNS_DOMAIN attribute, including negative cache entries;
removing any obtained DNSSEC trust anchors from the list of trust removing any obtained DNSSEC trust anchors from the list of trust
anchors; and clearing the outstanding DNS request queue. anchors; and clearing the outstanding DNS request queue.
INTERNAL_DNS_DOMAIN attributes SHOULD only be used on split tunnel INTERNAL_DNS_DOMAIN attributes SHOULD only be used on split tunnel
configurations where only a subset of traffic is routed into a configurations where only a subset of traffic is routed into a
private remote network using the IPsec connection. If all traffic is private remote network using the IPsec connection. If all traffic is
routed over the IPsec connection, the existing global routed over the IPsec connection, the existing global
INTERNAL_IP4_DNS and INTERNAL_IP6_DNS can be used without creating INTERNAL_IP4_DNS and INTERNAL_IP6_DNS can be used without creating
specific DNS exemptions. specific DNS exemptions.
5. INTERNAL_DNSSEC_TA Usage Guidelines 6. INTERNAL_DNSSEC_TA Usage Guidelines
DNS records can be used to publish specific records containing trust DNS records can be used to publish specific records containing trust
anchors for applications. The most common record type is the TLSA anchors for applications. The most common record type is the TLSA
record specified in [RFC6698]. This DNS record type publishes which record specified in [RFC6698]. This DNS record type publishes which
CA certificate or EE certificate to expect for a certain host name. CA certificate or EE certificate to expect for a certain host name.
These records are protected by DNSSEC and thus can be trusted by the These records are protected by DNSSEC and thus can be trusted by the
application. Whether to trust TLSA records instead of the application. Whether to trust TLSA records instead of the
traditional WebPKI depends on the local policy of the client. By traditional WebPKI depends on the local policy of the client. By
accepting an INTERNAL_DNSSEC_TA trust anchor via IKE from the remote accepting an INTERNAL_DNSSEC_TA trust anchor via IKE from the remote
IKE server, the IPsec client might be allowing the remote IKE server IKE server, the IPsec client might be allowing the remote IKE server
to override the trusted certificates for TLS. Similar override to override the trusted certificates for TLS. Similar override
concerns apply to other public key or fingerprint based DNS records, concerns apply to other public key or fingerprint based DNS records,
such as OPENPGPKEY, SMIMEA or IPSECKEY records. such as OPENPGPKEY, SMIMEA or IPSECKEY records.
Thus, installing an INTERNAL_DNSSEC_TA trust anchor can be seen as Thus, installing an INTERNAL_DNSSEC_TA trust anchor can be seen as
the equivalent of installing an Enterprise Certificate Agency (CA) the equivalent of installing an Enterprise Certificate Authority (CA)
certificate. It allows the remote IKE/IPsec server to modify DNS certificate. It allows the remote IKE/IPsec server to modify DNS
answers including its DNSSEC cryptographic signatures by overriding answers including its DNSSEC cryptographic signatures by overriding
existing DNS information with trust anchor conveyed via IKE and existing DNS information with trust anchor conveyed via IKE and
(temporarilly) installed on the IKE client. Of specific concern is (temporarilly) installed on the IKE client. Of specific concern is
the overriding of [RFC6698] based TLSA records, which represent a the overriding of [RFC6698] based TLSA records, which represent a
confirmation or override of an existing WebPKI TLS certificate. confirmation or override of an existing WebPKI TLS certificate.
Other DNS record types that convey cryptographic materials (public Other DNS record types that convey cryptographic materials (public
keys or fingerprints) are OPENPGPKEY, SMIMEA, SSHP and IPSECKEY keys or fingerprints) are OPENPGPKEY, SMIMEA, SSHP and IPSECKEY
records. records.
IKE clients willing to accept INTERNAL_DNSSEC_TA attributes MUST use IKE clients willing to accept INTERNAL_DNSSEC_TA attributes MUST use
a whitelist of one or more domains that can be updated out of band. a whitelist of one or more domains that can be updated out of band.
IKE clients with an empty whitelist MUST NOT use any IKE clients with an empty whitelist MUST NOT use any
INTERNAL_DNSSEC_TA attributes received over IKE. Such clients MAY INTERNAL_DNSSEC_TA attributes received over IKE. Such clients MAY
interpret receiving an INTERNAL_DNSSEC_TA attribute for a non- interpret receiving an INTERNAL_DNSSEC_TA attribute for a non-
whitelisted domain as an indication that their local configuration whitelisted domain as an indication that their local configuration
may need to be updated out of band. may need to be updated out of band.
IKE clients should take care to only whitelist domains that apply to IKE clients should take care to only whitelist domains that apply to
internal or managed domains, rather than to generic Internet traffic. internal or managed domains, rather than to generic Internet traffic.
The DNS root zone (".") MUST NOT be whitelisted. Other generic or The DNS root zone (".") MUST be ignored if it appears in a whitelist.
public domains, such as top-level domains, similarly SHOULD NOT be Other generic or public domains, such as top-level domains (TLDs),
whitelisted. similarly MUST be ignored if these appear in a whitelist unless the
entity actually is the operator of the TLD. To determine this, an
implementation MAY interactively ask the user when a VPN profile is
installed or activated to confirm this. Alternatively, it MAY
provide a special override keyword in its provisioning configuration
to ensure non-interactive agreement can be achieved only by the party
provisioning the VPN client, who presumbly is a trusted entity by the
end-user. Similarly, an entity might be using a special domain name,
such as ".internal", for its internal-only view and might wish to
force its provisioning system to accept such a domain in a Split DNS
configuration.
Any updates to this whitelist of domain names MUST happen via Any updates to this whitelist of domain names MUST happen via
explicit human interaction to prevent invisible installation of trust explicit human interaction or by a trusted automated provision system
anchors. to prevent malicious invisible installation of trust anchors in case
of aIKE server compromise.
IKE clients SHOULD accept any INTERNAL_DNSSEC_TA updates for IKE clients SHOULD accept any INTERNAL_DNSSEC_TA updates for
subdomain names of the whitelisted domain names. For example, if subdomain names of the whitelisted domain names. For example, if
"example.net" is whitelisted, then INTERNAL_DNSSEC_TA received for "example.net" is whitelisted, then INTERNAL_DNSSEC_TA received for
"antartica.example.net" SHOULD be accepted. "antartica.example.net" SHOULD be accepted.
IKE clients MAY interpret an INTERNAL_DNSSEC_TA for domain that was IKE clients MAY interpret an INTERNAL_DNSSEC_TA for domain that was
not preconfigured as an indication that it needs to update its IKE not preconfigured as an indication that it needs to update its IKE
configuration (out of band). The client MUST NOT use such a configuration (out of band). The client MUST NOT use such a
INTERNAL_DNSSEC_TA to reconfigure its local DNS settings. INTERNAL_DNSSEC_TA to reconfigure its local DNS settings.
skipping to change at page 11, line 24 skipping to change at page 12, line 34
Configuration Payload. Configuration Payload.
In most deployment scenario's, the IKE client has an expectation that In most deployment scenario's, the IKE client has an expectation that
it is connecting, using a split-network setup, to a specific it is connecting, using a split-network setup, to a specific
organisation or enterprise. A recommended policy would be to only organisation or enterprise. A recommended policy would be to only
accept INTERNAL_DNSSEC_TA directives from that organization's DNS accept INTERNAL_DNSSEC_TA directives from that organization's DNS
names. However, this might not be possible in all deployment names. However, this might not be possible in all deployment
scenarios, such as one where the IKE server is handing out a number scenarios, such as one where the IKE server is handing out a number
of domains that are not within one parent domain. of domains that are not within one parent domain.
6. Security Considerations 7. Security Considerations
As stated in Section 2, if the negotiated IPsec connection is not a
split tunnel configuration, the INTERNAL_DNS_DOMAIN and
INTERNAL_DNSSEC_TA Configuration Payloads MUST be ignored.
Otherwise, generic VPN service providers could maliciously override
DNSSEC based trust anchors of public DNS domains.
An initiator MUST only accept INTERNAL_DNSSEC_TA's for which it has a
whitelist. It MAY treat a received INTERNAL_DNSSEC_TA for an non-
whitelisted domain as a signal to update the whitelist via a non-IKE
provisioning mechanism. See Section 6 for additional security
considerations for DNSSEC trust anchors.
The use of Split DNS configurations assigned by an IKEv2 responder is The use of Split DNS configurations assigned by an IKEv2 responder is
predicated on the trust established during IKE SA authentication. predicated on the trust established during IKE SA authentication.
However, if IKEv2 is being negotiated with an anonymous or unknown However, if IKEv2 is being negotiated with an anonymous or unknown
endpoint (such as for Opportunistic Security [RFC7435]), the endpoint (such as for Opportunistic Security [RFC7435]), the
initiator MUST ignore Split DNS configurations assigned by the initiator MUST ignore Split DNS configurations assigned by the
responder. responder.
If a host connected to an authenticated IKE peer is connecting to If a host connected to an authenticated IKE peer is connecting to
another IKE peer that attempts to claim the same domain via the another IKE peer that attempts to claim the same domain via the
INTERNAL_DNS_DOMAIN attribute, the IKE connection SHOULD only process INTERNAL_DNS_DOMAIN attribute, the IKE connection SHOULD only process
the DNS information if the two connections are part of the same the DNS information if the two connections are part of the same
logical entity. Otherwise, the client SHOULD refuse the DNS logical entity. Otherwise, the client SHOULD refuse the DNS
information and potentially warn the end-user. information and potentially warn the end-user. For example, if a VPN
profile for "Example Corporation" is installed that provides two
IPsec connections, one covering 192.168.100.0/24 and one covering
10.13.14.0/24 it could be that both connections negotiate the same
INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA values. Since these are
part of the same remote organisation (or provisioning profile), the
Configuration Payloads can be used. However, if a user installs two
VPN profiles from two different unrelated independent entities, both
of these could be configured to use the same domain, for example
".internal". These two connections MUST NOT be allowed to be active
at the same time.
If the initiator is using DNSSEC validation for a domain in its If the initiator is using DNSSEC validation for a domain in its
public DNS view, and it requests and receives an INTERNAL_DNS_DOMAIN public DNS view, and it requests and receives an INTERNAL_DNS_DOMAIN
attribute without an INTERNAL_DNSSEC_TA, it will need to reconfigure attribute without an INTERNAL_DNSSEC_TA, it will need to reconfigure
its DNS resolver to allow for an insecure delegation. It SHOULD NOT its DNS resolver to allow for an insecure delegation. It SHOULD NOT
accept insecure delegations for domains that are DNSSEC signed in the accept insecure delegations for domains that are DNSSEC signed in the
public DNS view, for which it has not explicitely requested such public DNS view, for which it has not explicitly requested such
deletation by specifying the domain specifically using a deletation by specifying the domain specifically using a
INTERNAL_DNS_DOMAIN(domain) request. INTERNAL_DNS_DOMAIN(domain) request.
Deployments that configure INTERNAL_DNS_DOMAIN domains should pay Deployments that configure INTERNAL_DNS_DOMAIN domains should pay
close attention to their use of indirect reference RRtypes such as close attention to their use of indirect reference RRtypes in their
CNAME, DNAME, MX or SRV records so that resolving works as intended internal-only domain names. Examples of such RRtypes are NS, CNAME,
when all, some, or none of the IPsec connections are established. DNAME, MX or SRV records. For example, if the MX record for
"internal.example.com" points to "mx.internal.example.net", then both
"internal.example.com" and "internal.example.net" should be sent
using an INTERNAL_DNS_DOMAIN Configuration Payload.
IKE clients MAY want to require whitelisted domains for Top Level
Domains (TLDs) and Second Level Domains (SLDs) to further prevent
malicious DNS redirections for well known domains. This prevents
users from unknowingly giving DNS queries to third parties. This is
even more important if those well known domains are not deploying
DNSSEC, as the VPN service provider could then even modify the DNS
answers without detection.
The content of INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA may be The content of INTERNAL_DNS_DOMAIN and INTERNAL_DNSSEC_TA may be
passed to another (DNS) program for processing. As with any network passed to another (DNS) program for processing. As with any network
input, the content SHOULD be considered untrusted and handled input, the content SHOULD be considered untrusted and handled
accordingly. accordingly.
7. IANA Considerations 8. IANA Considerations
This document defines two new IKEv2 Configuration Payload Attribute This document defines two new IKEv2 Configuration Payload Attribute
Types, which are allocated from the "IKEv2 Configuration Payload Types, which are allocated from the "IKEv2 Configuration Payload
Attribute Types" namespace. Attribute Types" namespace.
Multi- Multi-
Value Attribute Type Valued Length Reference Value Attribute Type Valued Length Reference
------ ------------------- ------ ---------- --------------- ------ ------------------- ------ ---------- ---------------
25 INTERNAL_DNS_DOMAIN YES 0 or more [this document] 25 INTERNAL_DNS_DOMAIN YES 0 or more [this document]
26 INTERNAL_DNSSEC_TA YES 0 or more [this document] 26 INTERNAL_DNSSEC_TA YES 0 or more [this document]
Figure 1 Figure 1
8. References 9. References
8.1. Normative References 9.1. Normative References
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets", and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<https://www.rfc-editor.org/info/rfc1918>. <https://www.rfc-editor.org/info/rfc1918>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc2119>. editor.org/info/rfc2119>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions", Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005, RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/info/rfc4034>. <https://www.rfc-editor.org/info/rfc4034>.
[RFC5890] Klensin, J., "Internationalized Domain Names for [RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework", Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010, RFC 5890, DOI 10.17487/RFC5890, August 2010,
<https://www.rfc-editor.org/info/rfc5890>. <https://www.rfc-editor.org/info/rfc5890>.
skipping to change at page 13, line 19 skipping to change at page 15, line 14
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2 Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>. 2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References 9.2. Informative References
[RFC2775] Carpenter, B., "Internet Transparency", RFC 2775, [RFC2775] Carpenter, B., "Internet Transparency", RFC 2775,
DOI 10.17487/RFC2775, February 2000, DOI 10.17487/RFC2775, February 2000, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc2775>. editor.org/info/rfc2775>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435, Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <https://www.rfc-editor.org/info/rfc7435>. December 2014, <https://www.rfc-editor.org/info/rfc7435>.
Authors' Addresses Authors' Addresses
Tommy Pauly Tommy Pauly
Apple Inc. Apple Inc.
One Apple Park Way One Apple Park Way
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