draft-ietf-geopriv-lis-discovery-08.txt   draft-ietf-geopriv-lis-discovery-09.txt 
GEOPRIV M. Thomson GEOPRIV M. Thomson
Internet-Draft J. Winterbottom Internet-Draft J. Winterbottom
Intended status: Standards Track Andrew Intended status: Standards Track Andrew
Expires: September 24, 2009 March 23, 2009 Expires: October 3, 2009 April 1, 2009
Discovering the Local Location Information Server (LIS) Discovering the Local Location Information Server (LIS)
draft-ietf-geopriv-lis-discovery-08 draft-ietf-geopriv-lis-discovery-09
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Abstract Abstract
Discovery of the correct Location Information Server (LIS) in the Discovery of the correct Location Information Server (LIS) in the
local access network is necessary for devices that wish to acquire local access network is necessary for devices that wish to acquire
location information from the network. A method is described for the location information from the network. A method is described for the
discovery of a LIS. Dynamic Host Configuration Protocol (DHCP) discovery of a LIS. Dynamic Host Configuration Protocol (DHCP)
options for IP versions 4 and 6 are defined that specify a URI for a options for IP versions 4 and 6 are defined that specify a URI for a
LIS in the local access network. Additional DHCP options are LIS in the local access network. An alternative method that uses
provided that enable authentication of the indicated LIS. An URI-enabled NAPTR (U-NAPTR) is described for use where the DHCP
alternative method that uses URI-enabled NAPTR (U-NAPTR) is described option is unsuccessful.
for use where the DHCP option is unsuccessful.
Table of Contents Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3
1.1. DHCP Discovery . . . . . . . . . . . . . . . . . . . . . . 3 1.1. DHCP Discovery . . . . . . . . . . . . . . . . . . . . . . 3
1.2. U-NAPTR Discovery . . . . . . . . . . . . . . . . . . . . 4 1.2. U-NAPTR Discovery . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. LIS Discovery Using DHCP . . . . . . . . . . . . . . . . . . . 5 2. LIS Discovery Using DHCP . . . . . . . . . . . . . . . . . . . 4
2.1. DHCPv4 LIS URI Option . . . . . . . . . . . . . . . . . . 5 2.1. DHCPv4 LIS URI Option . . . . . . . . . . . . . . . . . . 4
2.2. DHCPv6 LIS URI Option . . . . . . . . . . . . . . . . . . 5 2.2. DHCPv6 LIS URI Option . . . . . . . . . . . . . . . . . . 5
2.3. LIS Authentication . . . . . . . . . . . . . . . . . . . . 6 3. U-NAPTR for LIS Discovery . . . . . . . . . . . . . . . . . . 6
2.3.1. Alternative Certificates . . . . . . . . . . . . . . . 7 3.1. Determining a Domain Name . . . . . . . . . . . . . . . . 7
2.3.2. Sub-Option Codes . . . . . . . . . . . . . . . . . . . 8 4. Overall Discovery Procedure . . . . . . . . . . . . . . . . . 7
2.3.3. Authentication Algorithm Summary . . . . . . . . . . . 9 4.1. Residential Gateways . . . . . . . . . . . . . . . . . . . 8
2.3.4. DHCPv4 LIS Certificate Fingerprint Option . . . . . . 10 4.2. Virtual Private Networks (VPNs) . . . . . . . . . . . . . 9
2.3.5. DHCPv6 LIS Certificate Fingerprint Option . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
3. U-NAPTR for LIS Discovery . . . . . . . . . . . . . . . . . . 13 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
3.1. Determining a Domain Name . . . . . . . . . . . . . . . . 14 6.1. Registration of DHCPv4 and DHCPv6 LIS URI Option Codes . . 10
4. Overall Discovery Procedure . . . . . . . . . . . . . . . . . 15 6.2. Registration of a Location Server Application Service
4.1. Virtual Private Networks (VPNs) . . . . . . . . . . . . . 16 Tag . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17 6.3. Registration of a Location Server Application Protocol
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Registration of DHCPv4 and DHCPv6 LIS URI Option Codes . . 18 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
6.2. Registration of DHCPv4 and DHCPv6 LIS Certificate 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Fingerprint Option Codes . . . . . . . . . . . . . . . . . 18 8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
6.3. Creation of Registry for LIS Certificate Fingerprint 8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Sub-Option Codes . . . . . . . . . . . . . . . . . . . . . 18
6.4. Registration of a Location Server Application Service
Tag . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.5. Registration of a Location Server Application Protocol
Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 19
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1. Normative References . . . . . . . . . . . . . . . . . . . 21
8.2. Informative References . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction and Overview 1. Introduction and Overview
The location of a device is a useful and sometimes necessary part of The location of a device is a useful and sometimes necessary part of
many services. A Location Information Server (LIS) is responsible many services. A Location Information Server (LIS) is responsible
for providing that location information to devices with an access for providing that location information to devices with an access
network. The LIS uses knowledge of the access network and its network. The LIS uses knowledge of the access network and its
physical topology to generate and serve location information to physical topology to generate and serve location information to
devices. devices.
skipping to change at page 3, line 49 skipping to change at page 3, line 49
DHCP ([RFC2131], [RFC3315]) is a commonly used mechanism for DHCP ([RFC2131], [RFC3315]) is a commonly used mechanism for
providing bootstrap configuration information allowing a device to providing bootstrap configuration information allowing a device to
operate in a specific network environment. The bulk of DHCP operate in a specific network environment. The bulk of DHCP
information is largely static; consisting of configuration information is largely static; consisting of configuration
information that does not change over the period that the device is information that does not change over the period that the device is
attached to the network. Physical location information might change attached to the network. Physical location information might change
over this time, however the address of the LIS does not. Thus, DHCP over this time, however the address of the LIS does not. Thus, DHCP
is suitable for configuring a device with the address of a LIS. is suitable for configuring a device with the address of a LIS.
A second DHCP option is defined that enables the authentication of a
LIS based on a fingerprint of the X.509 certificate [RFC5280] it
presents. Use of this option provides an alternative to the
authentication defined in HELD that relies on the domain name of the
LIS.
1.2. U-NAPTR Discovery 1.2. U-NAPTR Discovery
Where DHCP is not available, the DNS might be able to provide a URI. Where DHCP is not available, the DNS might be able to provide a URI.
This document describes a method that uses URI-enabled NAPTR This document describes a method that uses URI-enabled NAPTR
(U-NAPTR) [RFC4848], a Dynamic Delegation Discovery Service (DDDS) (U-NAPTR) [RFC4848], a Dynamic Delegation Discovery Service (DDDS)
profile that supports URI results. profile that supports URI results.
For the LIS discovery DDDS application, an Application Service tag For the LIS discovery DDDS application, an Application Service tag
"LIS" and an Application Protocol tag "HELD" are created and "LIS" and an Application Protocol tag "HELD" are created and
registered with the IANA. Taking a domain name, this U-NAPTR registered with the IANA. Taking a domain name, this U-NAPTR
application uses the two tags to determine the LIS URI. application uses the two tags to determine the LIS URI.
A domain name is the crucial input to the U-NAPTR resolution process.
Section 3.1 of this document describes several methods for deriving
an appropriate domain name.
1.3. Terminology 1.3. Terminology
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].
This document also uses the term "device" to refer to an end host, or This document also uses the term "device" to refer to an end host, or
client consistent with its use in HELD. In HELD and RFC3693 client consistent with its use in HELD. In HELD and RFC3693
[RFC3693] parlance, the Device is also the Target. [RFC3693] parlance, the Device is also the Target.
skipping to change at page 5, line 12 skipping to change at page 4, line 38
a public IP address and for directly or indirectly providing a LIS a public IP address and for directly or indirectly providing a LIS
service. service.
2. LIS Discovery Using DHCP 2. LIS Discovery Using DHCP
DHCP allows the access network provider to specify the address of a DHCP allows the access network provider to specify the address of a
LIS as part of network configuration. If the device is able to LIS as part of network configuration. If the device is able to
acquire a LIS URI using DHCP then this URI is used directly; the acquire a LIS URI using DHCP then this URI is used directly; the
U-NAPTR process is not necessary if this option is provided. U-NAPTR process is not necessary if this option is provided.
This document registers DHCP options for a LIS URI for both IPv4 and This document registers a DHCP option for a LIS URI for both IPv4 and
IPv6. A second option for both DHCP versions is also registered to IPv6. An "https:" LIS URI that is a product of U-NAPTR MUST be
convey a fingerprint of the certificate expected to be used by the authenticated using the domain name method described in Section 3.1
LIS. of RFC 2818 [RFC2818].
2.1. DHCPv4 LIS URI Option 2.1. DHCPv4 LIS URI Option
This section defines a DHCP for IPv4 (DHCPv4) option for the address This section defines a DHCP for IPv4 (DHCPv4) option for the address
of a LIS. of a LIS.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LIS_URI | Length | | | LIS_URI | Length | |
skipping to change at page 6, line 27 skipping to change at page 6, line 10
RFC-Editor Note: Please replace TBD with the assigned DHCPv6 RFC-Editor Note: Please replace TBD with the assigned DHCPv6
option code.]] option code.]]
Length: The length of the LIS URI option in octets. Length: The length of the LIS URI option in octets.
The semantics and format of the remainder of the LIS URI option The semantics and format of the remainder of the LIS URI option
are identical to the DHCPv4 option, except for the larger are identical to the DHCPv4 option, except for the larger
allowance for URI length granted by the 16 bit length field. allowance for URI length granted by the 16 bit length field.
DHCPv6 prohibits concatenation of option values. DHCPv6 prohibits concatenation of option values.
2.3. LIS Authentication
HTTP over TLS [RFC2818] describes how a host is authenticated based
on an expected domain name using public key infrastructure. Relying
exclusively on a domain name for authentication is not appropriate
for a LIS, since the domain name associated with the access network
might not be known. Indeed, it is often inappropriate to attempt to
assign any particular domain name to an access network.
This specification defines an alternative means of establishing an
expected identity for the server that uses a certificate fingerprint.
One or more fingerprints for the server certificate used by the LIS
is included in a second DHCP option. The device uses the fingerprint
information provided by the DHCP server to authenticate the LIS when
it establishes a TLS session. The domain name MUST NOT be used to
authenticate the LIS if a non-empty fingerprint information option is
provided.
This fingerprint option is of particular use for private networks
where authentication based on domain name is either infeasible or not
desirable.
The LIS certificate fingerprint option uses a format of "sub-
options", that allows for the inclusion of multiple fingerprint
values. Each "sub-option" includes a fingerprint generated by a
different cryptographic hash algorithm. The "sub-option" code
indicates the hash algorithm used for generating the fingerprint.
Each hash algorithm is identified by the assigned code from the IANA
registry "TLS HashAlgorithm Registry" established in [RFC5246].
The use of sub-options provides a means to upgrade hash functions
without affecting backward compatibility. New hash algorithms can be
used without affecting devices that do not yet support the algorithm.
A device MUST use the first fingerprint that it supports. If any
supported fingerprint does not match, the LIS MUST be considered
unauthenticated. If none of the specified hash algorithms are
supported by the device, it MUST consider the LIS to be
unauthenticated.
A fingerprint is generated or checked by applying a cryptographic
hash function to the DER-encoded certificate. Implementations MUST
support the SHA-1 algorithm, using a sub-option code of 2.
A device SHOULD request the LIS certificate fingerprint option at the
same time as the LIS URI option. Without the LIS certificate
fingerprint option a device cannot authenticate the LIS; absence of
this option prevents authentication.
An access network operator is able to nominate authentication based
on a domain name by omitting fingerprints. If an empty option is
provided, the device MUST authenticate the server using the default
method for the applicable URI scheme. For https: URIs, the
authentication described in Section 3.1 of RFC 2818 [RFC2818] MUST be
used if the LIS certificate fingerprint option is empty.
The certificate fingerprint can be ignored if the LIS URI indicates a
protocol that does not support exchange of certificates (such as
http:). Such a LIS cannot be authenticated using this option. The
LIS certificate fingerprint option MUST be empty if no means of
achieving authentication is available.
Note: Whether the device goes on to use the information provided by
an unauthenticated LIS depends on device policy. A device might
choose to continue with discovery using different network
interfaces or methods before falling back to an unauthenticated
LIS.
2.3.1. Alternative Certificates
There is a need to renew certificates as they expire. Around the
time that a certificate is replaced, DHCP configuration identifying
the certificate fingerprint might become invalid. Therefore, to
prevent , or where circumstances require that the LIS function is
served by multiple hosts, there is a need to allow for alternative
certificates. Authentication based on a fingerprint of a single
certificate fails around the time that a certificate is replaced, or
if there is a need for alternative servers that use different
certificates.
A sub-option code of 0 indicates that the sub-option contains a
certificate serial number. The value of the sub-option is the
integer value in network byte order. All subsequent fingerprint
values until the next occurence of sub-option 0 apply only to
certificates with the given serial number.
This method means that ordering of sub-options is signficant. All
fingerprint values after a certificate serial number apply to
certificates with that serial number only. The DHCP server MUST NOT
include fingerprint values before the first serial number, if a
serial number is used. Serial numbers can be omitted if there is
only one valid certificate.
Note that serial number alone is not a guarantee of uniqueness.
There is small probability that two different certificate issuers
could provide the same serial number with the same fingerprint. If
re-issue of the certificate is not viable, selection of a different
hash function might remove the collision.
2.3.2. Sub-Option Codes
The LIS certificate fingerprint option use sub-option codes that
identify the hash function that is used to generate the fingerprint.
A value of 0 indicates that the sub-option contains a certificate
serial number.
The following list is the current state of the "TLS HashAlgorithm
Registry" established in [RFC5246] and maintained by the IANA. As
additional values are added to the registry, these MAY be used as
option.
0: (serial number) This code indicates that the sub-option contains a
certificate serial number.
1: The sub-option contains a fingerprint generated using the MD5 hash
algorithm.
2: A fingerprint generated using SHA-1.
3: A fingerprint generated using SHA-224.
4: A fingerprint generated using SHA-256.
5: A fingerprint generated using SHA-384.
6: A fingerprint generated using SHA-512.
The sub-option code of 0 corresponds to the "none" value in the "TLS
HashAlgorithm Registry"; sub-option codes 1 through 6 correspond to
the same value.
Sub-option 0 contains a long integer value in network byte order.
This value is compared numerically. Negative and zero values are
possible (see [RFC5280]), and are expressed in twos complement;
therefore, the most significant bit of the first octet is interpreted
as having a negative value. This value could be up to 20 octets in
size. Note that the sub-option does not contain values encoded using
the distinguished encoding rules (DER).
2.3.3. Authentication Algorithm Summary
Once a device acquires the LIS URI option and the LIS certificate
fingerprint option, it is able to authenticate a LIS. Assuming that
the LIS URI indicates use of TLS, the device establishes a TLS
session and acquires a certificate from the LIS.
The LIS certificate fingerprint option is either empty, or it
contains a set of fingerprints. The set of fingerprints is either
divided into groups based on certificate serial number, or all of the
fingerprints describe the same certificate using different hash
algorithms. This is shown in Figure 3.
Without serial numbers With serial numbers
<hash> : <value> <serial> : <hash> : <value>
<hash> : <value> : <hash> : <value>
... <serial> : <hash> : <value>
: <hash> : <value>
...
Figure 3: LIS Certificate Fingerprint Option Structure
If the LIS certificate fingerprint option is empty, the LIS is
authenticated using the domain name indicated in its offered
certificate, using the mechanism described in Section 3.1 of
[RFC2818].
If the LIS certificate fingerprint option contains data, the LIS is
authenticated based on a fingerprint of its certificate. If multiple
certificates are indicated using serial numbers, the first sub-option
contains the serial numbers sub-option (code 0).
No serial numbers: The device matches the certificate fingerprint it
calculates from the LIS certificate against any of the fingerprint
sub-options.
Serial numbers: The device matches the certificate fingerprint it
calculates against a fingerprint sub-option that follows a serial
number sub-option containing the certificate serial number.
If no match can be found, the LIS is not authenticated.
2.3.4. DHCPv4 LIS Certificate Fingerprint Option
This section defines a DHCP for IPv4 (DHCPv4) option for LIS
certificate fingerprints.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LIS_CERT_FP | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. Fingerprint-Sub-Options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: DHCPv4 LIS Certificate Fingerprint Option
LIS_CERT_FP: The IANA assigned option number (TBD). [[IANA/
RFC-Editor Note: Please replace TBD with the assigned DHCPv4
option code.]]
Length: The length of the entire LIS certificate fingerprint option
in octets.
Fingerprint-Sub-Options: A series of one or more sub-options, as
shown in Figure 5.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Option | Length | Fingerprint-Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: DHCPv4 LIS Certificate Fingerprint Sub-Option
Sub-Option: A code that identifies the hash algorithm used to
generate the fingerprint, or a certificate serial number. The set
of codes are defined in Section 2.3.2.
Length: The length, in octets of the "Fingerprint-Value" sub-option.
Fingerprint-Value: The octet values of the certificate fingerprint
(or a certificate serial number for sub-option 0). An invalid
fingerprint is not equivalent to no fingerprint. If the length of
this field does not match the expected length of the hash function
output, the fingerprint MUST be considered invalid.
DHCPv4 option concatenation [RFC3396] SHOULD be avoided, but is
permitted if long values are required. The sub-options described in
this document do not require any more than 255 octets to express
fully, so concatenation of sub-options is not necessary.
2.3.5. DHCPv6 LIS Certificate Fingerprint Option
This section defines a DHCP for IPv6 (DHCPv6) option for LIS
certificate fingerprints. The DHCPv6 option for this parameter is
similarly formatted to the DHCPv4 option.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LIS_CERT_FP | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Fingerprint-Sub-Options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: DHCPv6 LIS Certificate Fingerprint Option
OPTION_LIS_CERT_FP: The IANA assigned option number (TBD). [[IANA/
RFC-Editor Note: Please replace TBD with the assigned DHCPv6
option code.]]
Length: The length of the LIS certificate fingerprint option in
octets.
Fingerprint-Sub-Options: A series of one or more sub-options, as
shown in Figure 7.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Option | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Fingerprint-Value .
. ... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: DHCPv6 LIS Certificate Fingerprint Sub-Option
The semantics of the DHCPv6 LIS certificate fingerprint sub-options
are identical to the DHCPv4 option except that concatenation is
neither required nor permitted. Length fields are 16 bits in length;
therefore, concatenation is not needed to accomodate values longer
than 255 octets. DHCPv6 prohibits concatenation of option values.
3. U-NAPTR for LIS Discovery 3. U-NAPTR for LIS Discovery
U-NAPTR resolution for a LIS takes a domain name as input and U-NAPTR resolution for a LIS takes a domain name as input and
produces a URI that identifies the LIS. This process also requires produces a URI that identifies the LIS. This process also requires
an Application Service tag and an Application Protocol tag, which an Application Service tag and an Application Protocol tag, which
differentiate LIS-related NAPTR records from other records for that differentiate LIS-related NAPTR records from other records for that
domain. domain.
Section 6.4 defines an Application Service tag of "LIS", which is Section 6.2 defines an Application Service tag of "LIS", which is
used to identify the location service for a particular domain. The used to identify the location service for a particular domain. The
Application Protocol tag "HELD", defined in Section 6.5, is used to Application Protocol tag "HELD", defined in Section 6.3, is used to
identify a LIS that understands the HELD protocol identify a LIS that understands the HELD protocol
[I-D.ietf-geopriv-http-location-delivery]. [I-D.ietf-geopriv-http-location-delivery].
The NAPTR records in the following example demonstrate the use of the The NAPTR records in the following example demonstrate the use of the
Application Service and Protocol tags. Iterative NAPTR resolution is Application Service and Protocol tags. Iterative NAPTR resolution is
used to delegate responsibility for the LIS service from used to delegate responsibility for the LIS service from
"zonea.example.net." and "zoneb.example.net." to "zonea.example.net." and "zoneb.example.net." to
"outsource.example.com.". "outsource.example.com.".
zonea.example.net. zonea.example.net.
skipping to change at page 13, line 44 skipping to change at page 6, line 49
"" ; regex "" ; regex
outsource.example.com. ; replacement outsource.example.com. ; replacement
) )
outsource.example.com. outsource.example.com.
;; order pref flags ;; order pref flags
IN NAPTR 100 10 "u" "LIS:HELD" ( ; service IN NAPTR 100 10 "u" "LIS:HELD" ( ; service
"!*.!https://lis.example.org:4802/?c=ex!" ; regex "!*.!https://lis.example.org:4802/?c=ex!" ; regex
. ; replacement . ; replacement
) )
Figure 8: Sample LIS:HELD Service NAPTR Records Figure 3: Sample LIS:HELD Service NAPTR Records
Details for the "LIS" Application Service tag and the "HELD" Details for the "LIS" Application Service tag and the "HELD"
Application Protocol tag are included in Section 6. Application Protocol tag are included in Section 6.
U-NAPTR MUST only be used if the DHCP LIS URI option is not An "https:" LIS URI that is a product of U-NAPTR MUST be
available. authenticated using the domain name method described in Section 3.1
of RFC 2818 [RFC2818].
An https: LIS URI that is a product of U-NAPTR MUST be authenticated
using the domain name method described in Section 3.1 of RFC 2818
[RFC2818].
3.1. Determining a Domain Name 3.1. Determining a Domain Name
The U-NAPTR discovery method described requires a domain name as The U-NAPTR discovery method described requires a domain name as
input. This document does not specify how that domain name is input. This document does not specify how that domain name is
acquired by a device. If a device knows one or more of the domain acquired by a device. If a device knows one or more domain names
names assigned to it, it MAY attempt to use each domain name as that might be used for discovery, it is able to attempt to use each
input. Static configuration of a device is possible if a domain name domain name as input to the U-NAPTR discovery process. Static
is known to work for this purpose. configuration of a device is possible if a domain name is known to
work for this purpose.
A fully qualified domain name (FQDN) for the device might be provided A fully qualified domain name (FQDN) for the device might be provided
by a DHCP server ([RFC4702] for DHCPv4, [RFC4704] for DHCPv6). by a DHCP server ([RFC4702] for DHCPv4, [RFC4704] for DHCPv6).
DHCPv4 option 15 [RFC2131] could also be used as a source of a domain DHCPv4 option 15 [RFC2131] could also be used as a source of a domain
name suffix for the device. If DHCP and any of these options are name suffix for the device. If DHCP and any of these options are
available, these values could be used as input the U-NAPTR procedure; available, these values could be used as input the U-NAPTR procedure;
however, implementers need to be aware that many DHCP servers do not however, implementers need to be aware that many DHCP servers do not
provide a sensible value for these options. provide a sensible value for these options. Therefore, this method
of discovery SHOULD be given lesser precedence than methods that are
based on more explicit assurances.
4. Overall Discovery Procedure 4. Overall Discovery Procedure
The individual components of discovery are combined into a single The individual components of discovery are combined into a single
discovery procedure. Some networks maintain a topology analogous to discovery procedure. Some networks maintain a topology analogous to
an onion and are comprised of layers, or segments, separating hosts an onion and are comprised of layers, or segments, separating devices
from the Internet through intermediate networks. Applying the from the Internet through intermediate networks. Applying the
individual discovery methods in an order that favours a physically individual discovery methods in an order that favours a physically
proximate LIS over a remote LIS is preferred. proximate LIS over a remote LIS is preferred.
A host MUST support DHCP discovery and MAY support U-NAPTR discovery. A device MUST support DHCP discovery, where applicable. Devices
The process described in this document is known to not work in a very SHOULD support U-NAPTR discovery unless no input domain names can be
common deployment scenario, namely the fixed wired environment determined.
described in Section 3.1 of [I-D.ietf-geopriv-l7-lcp-ps].
Alternative methods of discovery to address this limitation are
likely.
The following process ensures a greater likelihood of a LIS in close The following process ensures a greater likelihood of a LIS in close
physical proximity being discovered: physical proximity being discovered:
1. Request the DHCP LIS URI Option for each network interface. 1. Request the DHCP LIS URI Option for each network interface.
2. Use U-NAPTR to discover a LIS URI using all known domain names. 2. Use U-NAPTR to discover a LIS URI using all known domain names.
3. Use a statically configured LIS URI. 3. Use a statically configured LIS URI.
A host that has multiple network interfaces could potentially be A device that has multiple network interfaces could potentially be
served by a different access network on each interface, each with a served by a different access network on each interface, each with a
different LIS. The host SHOULD attempt to discover the LIS different LIS. The device SHOULD attempt to discover the LIS
applicable to each network interface, stopping when a LIS is applicable to each network interface, stopping when a LIS is
successfully discovered on any interface. successfully discovered on any interface.
A host that discovers a LIS URI MUST attempt to verify that the LIS A device that discovers a LIS URI MUST attempt to verify that the LIS
is able to provide location information. For the HELD protocol, the is able to provide location information. For the HELD protocol, the
host MUST make a location request to the LIS. If the LIS responds to device MUST make a location request to the LIS. If - at any time -
this request with the "notLocatable" error code (see Section 4.3.2 of the LIS responds to a request with the "notLocatable" error code (see
[I-D.ietf-geopriv-http-location-delivery]), the host MUST continue Section 4.3.2 of [I-D.ietf-geopriv-http-location-delivery]), the
the discovery process and not make further requests to that LIS on device MUST continue or restart the discovery process. A device
that network interface. SHOULD NOT make further requests to a LIS that provides a
"notLocatable" error until its network attachment changes, or it
discovers the LIS on an alternative network interface.
DHCP discovery MUST be attempted before any other discovery method. DHCP discovery MUST be attempted before any other discovery method.
This allows the network access provider a direct and explicit means This allows the network access provider a direct and explicit means
of configuring a LIS address. Alternative methods are only specified of configuring a LIS address. Alternative methods are only specified
as a means to discover a LIS where the DHCP infrastructure does not as a means to discover a LIS where the DHCP infrastructure does not
support the LIS URI option. support the LIS URI option.
This document does not mandate any particular source for the domain This document does not mandate any particular source for the domain
name that is used as input to U-NAPTR. Alternative methods for name that is used as input to U-NAPTR.
determining the domain name MAY be used.
Static configuration MAY be used if all other discovery methods fail. Static configuration MAY be used if all other discovery methods fail.
Note however, that if a host has moved from its customary location, Note however, that if a device has moved from its customary location,
static configuration might indicate a LIS that is unable to provide a static configuration might indicate a LIS that is unable to provide
location. accurate location information.
The product of the LIS discovery process is an http: or https: URI. The product of the LIS discovery process is an "https:" or "http:"
Nothing distinguishes this URI from other URIs with the same scheme, URI. Nothing distinguishes this URI from other URIs with the same
aside from the fact that it is the product of this process. Only scheme, aside from the fact that it is the product of this process.
URIs produced by the discovery process can be used for location Only URIs produced by the discovery process can be used for location
configuration using HELD. URIs that are not a product of LIS configuration using HELD. URIs that are not a product of LIS
discovery MUST NOT be used for location configuration. discovery MUST NOT be used for location configuration.
4.1. Virtual Private Networks (VPNs) 4.1. Residential Gateways
The process described in this document is known to not work in a very
common deployment scenario. A fixed wireline scenario is described
in more detail in Section 3.1 of [I-D.ietf-geopriv-l7-lcp-ps]. In
this fixed wireline environment an intervening residential gateway
exists between the device and the access network. If the residential
gateway does not provide this option to the devices it serves, those
devices are unable to discover a LIS.
Support of this specification by residential gateways ensures that
the devices they serve are able to acquire location information. In
most cases the residential gateway configures the devices it serves
using DHCP. When DHCP is used, the residential gateway MUST provide
the devices it serves with a LIS URI option. In order to provide a
sensible value for this option, the residential gateway MUST either:
1. act as a LIS and provide location information to the devices that
it serves, or
2. discover a LIS on its external interface and relay this
information to devices.
In either case, the residential gateway provides a LIS URI option to
devices.
4.2. Virtual Private Networks (VPNs)
LIS discovery over a VPN network interface SHOULD NOT be performed. LIS discovery over a VPN network interface SHOULD NOT be performed.
A LIS discovered in this way is unlikely to have the information A LIS discovered in this way is unlikely to have the information
necessary to determine an accurate location. necessary to determine an accurate location.
Since not all interfaces connected to a VPN can be detected by Not all interfaces connected to a VPN can be detected by devices or
devices, a LIS MUST NOT provide location information in response to the software running on them. A LIS MUST NOT provide location
requests that it can identify as originating from a device on the information in response to requests that it can identify as
remote end of a VPN interface. This ensures that even if a host originating from a device on the remote end of a VPN tunnel, unless
it is able to accurately determine location. The "notLocatable" HELD
error code can be used to indicate to a device that discovery has
revealed an unsuitable LIS. This ensures that even if a device
discovers a LIS over the VPN, it does not rely on a LIS that is discovers a LIS over the VPN, it does not rely on a LIS that is
unable to provide accurate location information. The exception to unable to provide accurate location information.
this is where the LIS and host are able to determine a location
without access network support.
5. Security Considerations 5. Security Considerations
The primary attack against the methods described in this document is The primary attack against the methods described in this document is
one that would lead to impersonation of a LIS. The LIS is one that would lead to impersonation of a LIS. The LIS is
responsible for providing location information and this information responsible for providing location information and this information
is critical to a number of network services; furthermore, a host does is critical to a number of network services; furthermore, a device
not necessarily have a prior relationship with a LIS. Several does not necessarily have a prior relationship with a LIS. Several
methods are described here that can limit the probablity of, or methods are described here that can limit the probablity of, or
provide some protection against, such an attack. provide some protection against, such an attack.
The address of a LIS is usually well-known within an access network; The address of a LIS is usually well-known within an access network;
therefore, interception of messages does not introduce any specific therefore, interception of messages does not introduce any specific
concerns. concerns.
Section 2.3 describes how a LIS is authenticated by devices, using
either certificate fingerprints or a domain name certificate. This
mechanism relies on the integrity of the information provided by the
DHCP server.
An attacker that is able to modify or spoof messages from a DHCP An attacker that is able to modify or spoof messages from a DHCP
server could provide a falsified LIS URI and certificate fingerprint server could provide a falsified LIS URI that a device would be able
options that a device would be able to use to successfully to use to successfully authenticate the LIS. Preventing DHCP
authenticate the LIS. Preventing DHCP messages from being modified messages from being modified or spoofed by attackers is necessary if
or spoofed by attackers is necessary if this information is to be this information is to be relied upon. Physical or link layer
relied upon. Physical or link layer security are commonplace methods security are commonplace methods that can reduce the possibility of
that can reduce the possibility of such an attack within an access such an attack within an access network; alternatively, DHCP
network; alternatively, DHCP authentication [RFC3118] can provide a authentication [RFC3118] can provide a degree of protection against
degree of protection against modification or spoofing. modification or spoofing.
An attacker could attempt to compromise the U-NAPTR resolution. A An attacker could attempt to compromise the U-NAPTR resolution. A
more thorough description of the security considerations for U-NAPTR more thorough description of the security considerations for U-NAPTR
applications is included in [RFC4848]. applications is included in [RFC4848]. In addition to considerations
related to U-NAPTR, it is important to recognize that the output of
U-NAPTR discovery is entirely dependent on its input. An attacker
who can control the domain name is therefore able to control the
final URI.
In addition to considerations related to U-NAPTR, it is important to A LIS that is identified by an "http:" URI cannot be authenticated.
recognize that the output of this is entirely dependent on its input. Use of HTTP also does not meet requirements in HELD for
An attacker who can control the domain name is therefore able to confidentiality and integrity. If an "http:" URI is the product of
control the final URI. DHCP or U-NAPTR discovery, this leaves devices vulnerable to several
attacks. Lower layer protections, such as layer 2 traffic separation
might provide some guarantees.
6. IANA Considerations 6. IANA Considerations
6.1. Registration of DHCPv4 and DHCPv6 LIS URI Option Codes 6.1. Registration of DHCPv4 and DHCPv6 LIS URI Option Codes
The IANA has assigned an option code of (TBD) for the DHCPv4 option The IANA has assigned an option code of (TBD) for the DHCPv4 option
for a LIS URI, as described in Section 2.1 of this document. for a LIS URI, as described in Section 2.1 of this document.
The IANA has assigned an option code of (TBD) for the DHCPv6 option The IANA has assigned an option code of (TBD) for the DHCPv6 option
for a LIS URI, as described in Section 2.2 of this document. for a LIS URI, as described in Section 2.2 of this document.
6.2. Registration of DHCPv4 and DHCPv6 LIS Certificate Fingerprint 6.2. Registration of a Location Server Application Service Tag
Option Codes
The IANA has assigned an option code of (TBD) for the DHCPv4 option
for LIS certificate fingerprints, as described in Section 2.3.4 of
this document.
The IANA has assigned an option code of (TBD) for the DHCPv6 option
for LIS certificate fingerprints, as described in Section 2.3.5 of
this document.
6.3. Creation of Registry for LIS Certificate Fingerprint Sub-Option
Codes
The IANA has created a registry entitled "DHCP Certificate
Fingerprint Sub-Option Codes" that contains codes identifying the
sub-option codes used for the DHCPv4 and DHCPv6 LIS certificate
fingerprint option. This registry is a sub-registry of "Dynamic Host
Configuration Protocol (DHCP) and Bootstrap Protocol (BOOTP)
Parameters".
The registry contains the following fields for each registration:
Sub-Option Code: The numerical value of the sub-option code. Values
from 0 through 255 (decimal) apply to DHCPv4 and DHCPv6. Values
from 256 to 65535 only apply to the DHCPv6 option.
Semantics: The name of the hash algorithm that the sub-option
represents, or a reference to the document defining specific
semantics.
TLS HashAlgorithm Code: For sub-options that refer to hash
algorithms, the code used in the "TLS HashAlgorithm Registry".
The initial values for this registry are included in Section 2.3.2 of
this document.
This registry operates under the "Specification Required" rule
[RFC5226]. For hash algorithms, the only specification required is
the specification referenced in the "TLS HashAlgorithm Registry".
6.4. Registration of a Location Server Application Service Tag
This section registers a new S-NAPTR/U-NAPTR Application Service tag This section registers a new S-NAPTR/U-NAPTR Application Service tag
for a LIS, as mandated by [RFC3958]. for a LIS, as mandated by [RFC3958].
Application Service Tag: LIS Application Service Tag: LIS
Intended usage: Identifies a service that provides a host with its Intended usage: Identifies a service that provides a device with its
location information. location information.
Defining publication: RFCXXXX Defining publication: RFCXXXX
Related publications: HELD [I-D.ietf-geopriv-http-location-delivery] Related publications: HELD [I-D.ietf-geopriv-http-location-delivery]
Contact information: The authors of this document Contact information: The authors of this document
Author/Change controller: The IESG Author/Change controller: The IESG
6.5. Registration of a Location Server Application Protocol Tag for 6.3. Registration of a Location Server Application Protocol Tag for
HELD HELD
This section registers a new S-NAPTR/U-NAPTR Application Protocol tag This section registers a new S-NAPTR/U-NAPTR Application Protocol tag
for the HELD [I-D.ietf-geopriv-http-location-delivery] protocol, as for the HELD [I-D.ietf-geopriv-http-location-delivery] protocol, as
mandated by [RFC3958]. mandated by [RFC3958].
Application Service Tag: HELD Application Service Tag: HELD
Intended Usage: Identifies the HELD protocol. Intended Usage: Identifies the HELD protocol.
skipping to change at page 20, line 11 skipping to change at page 11, line 37
Contact Information: The authors of this document Contact Information: The authors of this document
Author/Change Controller: The IESG Author/Change Controller: The IESG
7. Acknowledgements 7. Acknowledgements
The authors would like to thank Leslie Daigle for her work on The authors would like to thank Leslie Daigle for her work on
U-NAPTR; Peter Koch for feedback on how not to use DNS for discovery; U-NAPTR; Peter Koch for feedback on how not to use DNS for discovery;
Andy Newton for constructive suggestions with regards to document Andy Newton for constructive suggestions with regards to document
direction; Hannes Tschofenig and Richard Barnes for input and direction; Hannes Tschofenig and Richard Barnes for input and
reviews; Dean Willis for constructive feedback; Pasi Eronen for the reviews; Dean Willis for constructive feedback.
certificate fingerprint concept; Ralph Droms, David W. Hankins,
Damien Neil, and Bernie Volz for DHCP option format.
8. References 8. References
8.1. Normative References 8.1. Normative References
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host
Configuration Protocol",
RFC 2131, March 1997. RFC 2131, March 1997.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2818] Rescorla, E., "HTTP Over
TLS", RFC 2818, May 2000.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Bound, J.,
and M. Carney, "Dynamic Host Configuration Protocol for Volz, B., Lemon, T.,
IPv6 (DHCPv6)", RFC 3315, July 2003. Perkins, C., and M.
Carney, "Dynamic Host
Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315,
July 2003.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the [RFC3396] Lemon, T. and S. Cheshire,
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, "Encoding Long Options in
the Dynamic Host
Configuration Protocol
(DHCPv4)", RFC 3396,
November 2002. November 2002.
[RFC4702] Stapp, M., Volz, B., and Y. Rekhter, "The Dynamic Host [RFC4702] Stapp, M., Volz, B., and
Configuration Protocol (DHCP) Client Fully Qualified Y. Rekhter, "The Dynamic
Domain Name (FQDN) Option", RFC 4702, October 2006. Host Configuration
Protocol (DHCP) Client
[RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for Fully Qualified Domain
IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN) Name (FQDN) Option",
Option", RFC 4704, October 2006. RFC 4702, October 2006.
[RFC4848] Daigle, L., "Domain-Based Application Service Location
Using URIs and the Dynamic Delegation Discovery Service
(DDDS)", RFC 4848, April 2007.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC4704] Volz, B., "The Dynamic
IANA Considerations Section in RFCs", BCP 26, RFC 5226, Host Configuration
May 2008. Protocol for IPv6 (DHCPv6)
Client Fully Qualified
Domain Name (FQDN)
Option", RFC 4704,
October 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC4848] Daigle, L., "Domain-Based
(TLS) Protocol Version 1.2", RFC 5246, August 2008. Application Service
Location Using URIs and
the Dynamic Delegation
Discovery Service (DDDS)",
RFC 4848, April 2007.
[I-D.ietf-geopriv-http-location-delivery] [I-D.ietf-geopriv-http-location-delivery] Barnes, M., Winterbottom,
Barnes, M., Winterbottom, J., Thomson, M., and B. Stark, J., Thomson, M., and B.
"HTTP Enabled Location Delivery (HELD)", Stark, "HTTP Enabled
draft-ietf-geopriv-http-location-delivery-13 (work in Location Delivery (HELD)",
progress), February 2009. draft-ietf-geopriv-http-
location-delivery-13 (work
in progress),
February 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words
Requirement Levels", BCP 14, RFC 2119, March 1997. for use in RFCs to
Indicate Requirement
Levels", BCP 14, RFC 2119,
March 1997.
8.2. Informative References 8.2. Informative References
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP [RFC3118] Droms, R. and W. Arbaugh,
Messages", RFC 3118, June 2001. "Authentication for DHCP
Messages", RFC 3118,
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and June 2001.
J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application [RFC3693] Cuellar, J., Morris, J.,
Service Location Using SRV RRs and the Dynamic Delegation Mulligan, D., Peterson,
Discovery Service (DDDS)", RFC 3958, January 2005. J., and J. Polk, "Geopriv
Requirements", RFC 3693,
February 2004.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC3958] Daigle, L. and A. Newton,
Housley, R., and W. Polk, "Internet X.509 Public Key "Domain-Based Application
Infrastructure Certificate and Certificate Revocation List Service Location Using SRV
(CRL) Profile", RFC 5280, May 2008. RRs and the Dynamic
Delegation Discovery
Service (DDDS)", RFC 3958,
January 2005.
[I-D.ietf-geopriv-l7-lcp-ps] [I-D.ietf-geopriv-l7-lcp-ps] Tschofenig, H. and H.
Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7 Schulzrinne, "GEOPRIV
Location Configuration Protocol; Problem Statement and Layer 7 Location
Requirements", draft-ietf-geopriv-l7-lcp-ps-09 (work in Configuration Protocol;
progress), February 2009. Problem Statement and
Requirements", draft-ietf-
geopriv-l7-lcp-ps-09 (work
in progress),
February 2009.
[I-D.ietf-geopriv-lbyr-requirements] [I-D.ietf-geopriv-lbyr-requirements] Marshall, R.,
Marshall, R., "Requirements for a Location-by-Reference "Requirements for a
Mechanism", draft-ietf-geopriv-lbyr-requirements-07 (work Location-by-Reference
in progress), February 2009. Mechanism", draft-ietf-
geopriv-lbyr-requirements-
07 (work in progress),
February 2009.
Authors' Addresses Authors' Addresses
Martin Thomson Martin Thomson
Andrew Andrew
PO Box U40 PO Box U40
Wollongong University Campus, NSW 2500 Wollongong University Campus, NSW 2500
AU AU
Phone: +61 2 4221 2915 Phone: +61 2 4221 2915
Email: martin.thomson@andrew.com EMail: martin.thomson@andrew.com
URI: http://www.andrew.com/ URI: http://www.andrew.com/
James Winterbottom James Winterbottom
Andrew Andrew
PO Box U40 PO Box U40
Wollongong University Campus, NSW 2500 Wollongong University Campus, NSW 2500
AU AU
Phone: +61 2 4221 2938 Phone: +61 2 4221 2938
Email: james.winterbottom@andrew.com EMail: james.winterbottom@andrew.com
URI: http://www.andrew.com/ URI: http://www.andrew.com/
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