Authorization for NSIS Signaling Layer Protocols
draft-ietf-nsis-nslp-auth-07
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 5981.
|
|
|---|---|---|---|
| Authors | Roland Bless , Martin Stiemerling , Hannes Tschofenig , Jukka Manner | ||
| Last updated | 2020-01-21 (Latest revision 2010-09-22) | ||
| Replaces | draft-manner-nsis-nslp-auth | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Experimental | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | (None) | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 5981 (Experimental) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Lars Eggert | ||
| Send notices to | (None) |
draft-ietf-nsis-nslp-auth-07
Network Working Group J. Manner
Internet-Draft Aalto Univ
Intended status: Experimental M. Stiemerling
Expires: March 26, 2011 NEC
H. Tschofenig
Nokia Siemens Networks
R. Bless, Ed.
KIT
September 22, 2010
Authorization for NSIS Signaling Layer Protocols
draft-ietf-nsis-nslp-auth-07.txt
Abstract
Signaling layer protocols specified within the NSIS framework may
rely on the GIST (General Internet Signaling Transport) protocol to
handle authorization. Still, the signaling layer protocol above GIST
itself may require separate authorization to be performed when a node
receives a request for a certain kind of service or resources. This
draft presents a generic model and object formats for session
authorization within the NSIS Signaling Layer Protocols. The goal of
session authorization is to allow the exchange of information between
network elements in order to authorize the use of resources for a
service and to coordinate actions between the signaling and transport
planes.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 26, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Conventions used in this document . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Session Authorization Object . . . . . . . . . . . . . . . . . 7
3.1. Session Authorization Object format . . . . . . . . . . . 7
3.2. Session Authorization Attributes . . . . . . . . . . . . . 8
3.2.1. Authorizing Entity Identifier . . . . . . . . . . . . 9
3.2.2. Session Identifier . . . . . . . . . . . . . . . . . . 11
3.2.3. Source Address . . . . . . . . . . . . . . . . . . . . 11
3.2.4. Destination Address . . . . . . . . . . . . . . . . . 13
3.2.5. Start time . . . . . . . . . . . . . . . . . . . . . . 14
3.2.6. End time . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.7. NSLP Object List . . . . . . . . . . . . . . . . . . . 15
3.2.8. Authentication data . . . . . . . . . . . . . . . . . 17
4. Integrity of the SESSION_AUTH policy element . . . . . . . . . 18
4.1. Shared symmetric keys . . . . . . . . . . . . . . . . . . 18
4.1.1. Operational Setting using shared symmetric keys . . . 18
4.2. Kerberos . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3. Public Key . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3.1. Operational Setting for public key based
authentication . . . . . . . . . . . . . . . . . . . . 21
4.4. HMAC Signed . . . . . . . . . . . . . . . . . . . . . . . 23
5. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.1. The Coupled Model . . . . . . . . . . . . . . . . . . . . 26
5.2. The associated model with one policy server . . . . . . . 26
5.3. The associated model with two policy servers . . . . . . . 27
5.4. The non-associated model . . . . . . . . . . . . . . . . . 27
6. Message Processing Rules . . . . . . . . . . . . . . . . . . . 28
6.1. Generation of the SESSION_AUTH by the authorizing
entity . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.2. Processing within the QoS NSLP . . . . . . . . . . . . . . 28
6.2.1. Message Generation . . . . . . . . . . . . . . . . . . 28
6.2.2. Message Reception . . . . . . . . . . . . . . . . . . 29
6.2.3. Authorization (QNE or PDP) . . . . . . . . . . . . . . 29
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6.2.4. Error Signaling . . . . . . . . . . . . . . . . . . . 30
6.3. Processing with the NAT/FW NSLP . . . . . . . . . . . . . 30
6.3.1. Message Generation . . . . . . . . . . . . . . . . . . 31
6.3.2. Message Reception . . . . . . . . . . . . . . . . . . 31
6.3.3. Authorization (Router/PDP) . . . . . . . . . . . . . . 31
6.3.4. Error Signaling . . . . . . . . . . . . . . . . . . . 32
6.4. Integrity Protection of NSLP messages . . . . . . . . . . 32
7. Security Considerations . . . . . . . . . . . . . . . . . . . 34
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 39
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
10.1. Normative References . . . . . . . . . . . . . . . . . . . 40
10.2. Informative References . . . . . . . . . . . . . . . . . . 40
Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45
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1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
The term "NSLP node" (NN) is used to refer to an NSIS node running an
NSLP protocol that can make use of the authorization object discussed
in this document. Currently, this node would run either the QoS NSLP
[I-D.ietf-nsis-qos-nslp] or the NAT/FW NSLP
[I-D.ietf-nsis-nslp-natfw] service.
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2. Introduction
The Next Steps in Signaling (NSIS) framework [RFC4080] defines a
suite of protocols for the next generation in Internet signaling.
The design is based on a generalized transport protocol for signaling
applications, the General Internet Signaling Transport (GIST)
[I-D.ietf-nsis-ntlp], and various kinds of signaling applications.
Two signaling applications and their NSIS Signaling Layer Protocol
(NSLP) have been designed, a Quality of Service application (QoS
NSLP) [I-D.ietf-nsis-qos-nslp] and a NAT/firewall application
(NAT/FW) [I-D.ietf-nsis-nslp-natfw].
The basic security architecture for NSIS is based on a chain-of-trust
model, where each GIST hop may choose the appropriate security
protocol, taking into account the signaling application requirements.
For instance, communication between two directly adjacent GIST peers
may be secured via TCP/TLS. On the one hand this model is
appropriate for a number of different use cases, and allows the
signaling applications to leave the handling of security to GIST. On
the other hand, several sessions of different signaling applications
are then multiplexed onto the same GIST TLS connection.
Yet, in order to allow for finer-grain per-session or per-user
admission control, it is necessary to provide a mechanism for
ensuring that the use of resources by a host has been properly
authorized before allowing the signaling application to commit the
resource request, e.g., a QoS reservation or mappings for NAT
traversal. In order to meet this requirement, there must be
information in the NSLP message which may be used to verify the
validity of the request. This can be done by providing the host with
a session authorization policy element which is inserted into the
message and verified by the respective network elements.
This document describes a generic NSLP layer session authorization
policy object (SESSION_AUTH) used to convey authorization information
for the request. Generic in this context means that it is usable by
all NSLPs. The scheme is based on third-party tokens. A trusted
third party provides authentication tokens to clients and allows
verification of the information by the network elements. The
requesting host inserts its authorization information acquired from
the trusted third party into the NSLP message to allow verification
of the network resource request. Network elements verify the request
and then process it based on admission policy (e.g., they perform a
resource reservation or change bindings or firewall filter). This
work is based on RFC 3520 [RFC3520] and RFC 3521 [RFC3521].
The default operation when using NSLP layer session authorization is
to add one authorization policy object. Yet, in order to support
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end-to-end signaling and request authorization from different
networks, a host initiating an NSLP signaling session may add more
than one SESSION_AUTH object in the message. The identifier of the
authorizing entity can be used by the network elements to use the
third party they trust to verify the request.
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3. Session Authorization Object
This section presents a new NSLP layer object called session
authorization (SESSION_AUTH). The SESSION_AUTH object can be used in
the currently specified and future NSLP protocols.
The authorization attributes follow the format and specification
given in RFC3520 [RFC3520].
3.1. Session Authorization Object format
The SESSION_AUTH object contains a list of fields which describe the
session, along with other attributes. The object header follows the
generic NSLP object header, therefore it can be used together with
any NSLP.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|B|r|r| Type |r|r|r|r| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +
// Session Authorization Attribute List //
+ +
+---------------------------------------------------------------+
The value for the Type field comes from shared NSLP object type
space. The Length field is given in units of 32 bit words and
measures the length of the Value component of the TLV object (i.e. it
does not include the standard header).
The bits marked 'A' and 'B' are extensibility flags, and used to
signal the desired treatment for objects whose treatment has not been
defined in the protocol specification (i.e. whose Type field is
unknown at the receiver). The following four categories of object
have been identified, and are described here for informational
purposes only, i.e., for normative behavior refer to the particular
NSLP documents (e.g., [I-D.ietf-nsis-qos-nslp]
[I-D.ietf-nsis-nslp-natfw]).
AB=00 ("Mandatory"): If the object is not understood, the entire
message containing it MUST be rejected, and an error message sent
back (usually of class/code "Protocol Error/Unknown object present").
AB=01 ("Ignore"): If the object is not understood, it MUST be deleted
and the rest of the message processed as usual.
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AB=10 ("Forward"): If the object is not understood, it MUST be
retained unchanged in any message forwarded as a result of message
processing, but not stored locally.
AB=11 ("Refresh"): If the object is not understood, it should be
incorporated into the locally stored signaling application state for
this flow/session, forwarded in any resulting message, and also used
in any refresh or repair message which is generated locally. This
flag combination is not used by all NSLPs, e.g., it is not used in
NATFW NSLP.
The remaining bits marked 'r' are reserved. The extensibility flags
follow the definition in the GIST specification. The SESSION_AUTH
object defines in this specification MUST have the AB-bits set to
"10". An NSLP Node (NN) may use the authorization information if it
is configured to do so, but may also just skip the object.
Type: SESSION_AUTH_OBJ (IANA-TBD)
Length: Variable, contains length of Session authorization object
list in units of 32 bit words.
Session Authorization Attribute List: variable length
The session authorization attribute list is a collection of
objects that describes the session and provides other information
necessary to verify resource request (e.g., a resource
reservation, binding, or firewall filter change request). An
initial set of valid objects is described in Section 3.2.
3.2. Session Authorization Attributes
A session authorization attribute may contain a variety of
information and has both an attribute type and subtype. The
attribute itself MUST be a multiple of 4 octets in length, and any
attributes that are not a multiple of 4 octets long MUST be padded to
a 4-octet boundary. All padding bytes MUST have a value of zero.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Value ... //
+---------------------------------------------------------------+
Length: 16 bits
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The Length field is two octets and indicates the actual length of
the attribute (including Length, X-Type and SubType fields) in
number of octets. The length does NOT include any bytes padding
to the value field to make the attribute a multiple of 4 octets
long.
X-Type: 8 bits
Session authorization attribute type (X-Type) field is one octet.
IANA acts as a registry for X-Types as described in Section 8,
IANA Considerations. This specification uses the following
X-Types:
1. AUTH_ENT_ID The unique identifier of the entity that authorized
the session.
2. SESSION_ID Unique identifier for this session, usually created
locally at the authorizing entity. See also RFC 3520 [RFC3520],
not to be confused with the SESSIONID of GIST/NSIS.
3. SOURCE_ADDR Address specification for the signaling session
initiator, i.e., the source address of the signaling message
originator.
4. DEST_ADDR Address specification for the signaling session end-
point.
5. START_TIME The starting time for the session.
6. END_TIME The end time for the session.
7. AUTHENTICATION_DATA Authentication data of the session
authorization policy element.
SubType: 8 bits
Session authorization attribute sub-type is one octet in length.
The value of the SubType depends on the X-Type.
Value: variable length
The attribute specific information.
3.2.1. Authorizing Entity Identifier
AUTH_ENT_ID is used to identify the entity that authorized the
initial service request and generated the session authorization
policy element. The AUTH_ENT_ID may be represented in various
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formats, and the SubType is used to define the format for the ID.
The format for AUTH_ENT_ID is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: AUTH_ENT_ID
SubType:
The following sub-types for AUTH_ENT_ID are defined. IANA acts as
a registry for AUTH_ENT_ID sub-types as described in Section 8,
IANA Considerations. Initially, the registry contains the
following sub-types of AUTH_ENT_ID:
1. IPV4_ADDRESS IPv4 address represented in 32 bits
2. IPV6_ADDRESS IPv6 address represented in 128 bits
3. FQDN Fully Qualified Domain Name as defined in [RFC1034] as an
ASCII string.
4. ASCII_DN X.500 Distinguished name as defined in [RFC4514] as an
ASCII string.
5. UNICODE_DN X.500 Distinguished name as defined in [RFC4514] as a
UTF-8 string.
6. URI Universal Resource Identifier, as defined in [RFC3986].
7. KRB_PRINCIPAL Fully Qualified Kerberos Principal name
represented by the ASCII string of a principal followed by the @
realm name as defined in [RFC4120] (e.g., johndoe@nowhere).
8. X509_V3_CERT The Distinguished Name of the subject of the
certificate as defined in [RFC4514] as a UTF-8 string.
9. PGP_CERT The OpenPGP certificate of the authorizing entity as
defined as Public-Key Packet in [RFC4880].
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10. HMAC_SIGNED Indicates that the AUTHENTICATION_DATA attribute
contains a self-signed HMAC signature [RFC2104] that ensures the
integrity of the NSLP message. The HMAC is calculated over all
NSLP objects given in the NSLP_OBJECT_LIST attribute that MUST
also be present. The object specifies the Hash Algorithm that
is used for calculation of the HMAC as Transform ID from
Transform Type 3 of the IKEv2 registry [RFC4306].
OctetString: Contains the authorizing entity identifier.
3.2.2. Session Identifier
SESSION_ID is a unique identifier used by the authorizing entity to
identify the request. It may be used for a number of purposes,
including replay detection, or to correlate this request to a policy
decision entry made by the authorizing entity. For example, the
SESSION_ID can be based on simple sequence numbers or on a standard
NTP timestamp.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: SESSION_ID
SubType:
No subtypes for SESSION_ID are currently defined; this field MUST be
set to zero. The authorizing entity is the only network entity that
needs to interpret the contents of the SESSION_ID therefore the
contents and format are implementation dependent.
OctetString: The OctetString contains the session identifier.
3.2.3. Source Address
SOURCE_ADDR is used to identify the source address specification of
the authorized session. This X-Type may be useful in some scenarios
to make sure the resource request has been authorized for that
particular source address and/or port. Usually, it corresponds to
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the signaling source, e.g., the IP source address of the GIST packet,
or flow source or flow destination address respectively, which are
contained in the GIST MRI (Message Routing Information) object.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: SOURCE_ADDR
SubType:
The following sub types for SOURCE_ADDR are defined. IANA acts as
a registry for SOURCE_ADDR sub-types as described in Section 8,
IANA Considerations. Initially, the registry contains the
following sub types for SOURCE_ADDR:
1. IPV4_ADDRESS IPv4 address represented in 32 bits
2. IPV6_ADDRESS IPv6 address represented in 128 bits
3. UDP_PORT_LIST list of UDP port specifications, represented as 16
bits per list entry.
4. TCP_PORT_LIST list of TCP port specifications, represented as 16
bits per list entry.
5. SPI Security Parameter Index represented in 32 bits
OctetString: The OctetString contains the source address information.
In scenarios where a source address is required (see Section 5), at
least one of the subtypes 1 or 2 MUST be included in every Session
Authorization Data Policy Element. Multiple SOURCE_ADDR attributes
MAY be included if multiple addresses have been authorized. The
source address of the request (e.g., a QoS NSLP RESERVE) MUST match
one of the SOURCE_ADDR attributes contained in this Session
Authorization Data Policy Element.
At most, one instance of subtype 3 MAY be included in every Session
Authorization Data Policy Element. At most, one instance of subtype
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4 MAY be included in every Session Authorization Data Policy Element.
Inclusion of a subtype 3 attribute does not prevent inclusion of a
subtype 4 attribute (i.e., both UDP and TCP ports may be authorized).
If no PORT attributes are specified, then all ports are considered
valid; otherwise, only the specified ports are authorized for use.
Every source address and port list must be included in a separate
SOURCE_ADDR attribute.
3.2.4. Destination Address
DEST_ADDR is used to identify the destination address of the
authorized session. This X-Type may be useful in some scenarios to
make sure the resource request has been authorized for that
particular destination address and/or port.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute in number of octets, which MUST be >
4.
X-Type: DEST_ADDR
SubType:
The following sub types for DEST_ADDR are defined. IANA acts as a
registry for DEST_ADDR sub-types as described in Section 8, IANA
Considerations. Initially, the registry contains the following
sub types for DEST_ADDR:
1. IPV4_ADDRESS IPv4 address represented in 32 bits
2. IPV6_ADDRESS IPv6 address represented in 128 bits
3. UDP_PORT_LIST list of UDP port specifications, represented as 16
bits per list entry.
4. TCP_PORT_LIST list of TCP port specifications, represented as 16
bits per list entry.
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5. SPI Security Parameter Index represented in 32 bits
OctetString: The OctetString contains the destination address
specification.
In scenarios where a destination address is required (see Section 5),
at least one of the subtypes 1 or 2 MUST be included in every Session
Authorization Data Policy Element. Multiple DEST_ADDR attributes MAY
be included if multiple addresses have been authorized. The
destination address field of the resource reservation datagram (e.g.,
QoS NSLP Reserve) MUST match one of the DEST_ADDR attributes
contained in this Session Authorization Data Policy Element.
At most, one instance of subtype 3 MAY be included in every Session
Authorization Data Policy Element. At most, one instance of subtype
4 MAY be included in every Session Authorization Data Policy Element.
Inclusion of a subtype 3 attribute does not prevent inclusion of a
subtype 4 attribute (i.e., both UDP and TCP ports may be authorized).
If no PORT attributes are specified, then all ports are considered
valid; otherwise, only the specified ports are authorized for use.
Every destination address and port list must be included in a
separate DEST_ADDR attribute.
3.2.5. Start time
START_TIME is used to identify the start time of the authorized
session and can be used to prevent replay attacks. If the
SESSION_AUTH policy element is presented in a resource request, the
network SHOULD reject the request if it is not received within a few
seconds of the start time specified.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: START_TIME
SubType:
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The following sub types for START_TIME are defined. IANA acts as a
registry for START_TIME sub-types as described in Section 8, IANA
Considerations. Initially, the registry contains the following sub
types for START_TIME:
1. 1 NTP_TIMESTAMP NTP Timestamp Format as defined in RFC 5905
[RFC5905].
OctetString: The OctetString contains the start time.
3.2.6. End time
END_TIME is used to identify the end time of the authorized session
and can be used to limit the amount of time that resources are
authorized for use (e.g., in prepaid session scenarios).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: END_TIME
SubType:
The following sub types for END_TIME are defined. IANA acts as a
registry for END_TIME sub-types as described in Section 8, IANA
Considerations. Initially, the registry contains the following sub
types for END_TIME:
1. NTP_TIMESTAMP NTP Timestamp Format as defined in RFC 5905
[RFC5905].
OctetString: The OctetString contains the end time.
3.2.7. NSLP Object List
The NSLP_OBJECT_LIST attribute contains a list of NSLP objects types
that are used in the keyed-hash computation whose result is given in
the AUTHENTICATION_DATA attribute. This allows for an integrity
protection of NSLP PDUs. If an NSLP_OBJECT_LIST attribute has been
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included in the SESSION_AUTH policy element, an AUTHENTICATION_DATA
attribute MUST also be present.
The creator of this attribute lists every NSLP object type whose NSLP
PDU object was included in the computation of the hash. The hash
computation has to follow the order of the NSLP object types as
specified by the list. The receiver can verify the integrity of the
NSLP PDU by computing a hash over all NSLP objects that are listed in
this attribute (in the given order) including all the attributes of
the authorization object. Since all NSLP object types are unique
over all different NSLPs, this will work for any NSLP.
Basic NTLP/NSLP objects like the session ID, the NSLPID and the MRI
MUST be always included in the HMAC. Since they are not carried
within the NSLP itself, but only within GIST, they have to be
provided for HMAC calculation, e.g., they can be delivered via the
GIST API. They MUST be normalized to their network representation
from [I-D.ietf-nsis-ntlp] again before calculating the hash. These
values MUST be hashed first (in order sessionID, NSLPID, MRI), before
any other NSLP object values that are included in the hash
computation.
A summary of the NSLP_OBJECT_LIST attribute format is described
below.
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
+---------------+---------------+---------------+---------------+
| Length | NSLP_OBJ_LIST | zero |
+---------------+---------------+-------+-------+---------------+
| # of signed NSLP objects = n | rsv | NSLP object type (1) |
+-------+-------+---------------+-------+-------+---------------+
| rsv | NSLP object type (2) | ..... //
+-------+-------+---------------+---------------+---------------+
| rsv | NSLP object type (n) | (padding if required) |
+--------------+----------------+---------------+---------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: NSLP_OBJECT_LIST
SubType: No sub types for NSLP_OBJECT_LIST are currently defined.
This field MUST be set to 0 and ignored upon reception.
# of signed NSLP objects: The number n of NSLP object types that
follow. n=0 is allowed, i.e., only a padding field is contained then.
rsv: reserved bits and MUST be set to 0 (zero) and ignored upon
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reception.
NSLP object type: the NSLP 12-bit object type identifier of the
object that was included in the hash calculation. The NSLP object
type values comprise only 12 bit, so four bits per type value are
currently not used within the list. Depending on the number of
signed objects, a corresponding padding word of 16 bit must be
supplied.
padding: padding MUST be added if the number of NSLP objects is even
and MUST NOT be added if the number of NSLP objects is odd. If
padding has to be applied the padding field MUST be 16 bit set to 0
and its contents MUST be ignored upon reception.
3.2.8. Authentication data
The AUTHENTICATION_DATA attribute contains the authentication data of
the SESSION_AUTH policy element and signs all the data in the policy
element up to the AUTHENTICATION_DATA. If the AUTHENTICATION_DATA
attribute has been included in the SESSION_AUTH policy element, it
MUST be the last attribute in the list. The algorithm used to
compute the authentication data depends on the AUTH_ENT_ID SubType
field. See Section 4 entitled Integrity of the SESSION_AUTH policy
element.
A summary of AUTHENTICATION_DATA attribute format is described below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | X-Type | SubType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// OctetString ... //
+---------------------------------------------------------------+
Length: Length of the attribute, which MUST be > 4.
X-Type: AUTHENTICATION_DATA
SubType: No sub types for AUTHENTICATION_DATA are currently defined.
This field MUST be set to 0 and ignored upon reception.
OctetString: The OctetString contains the authentication data of the
SESSION_AUTH.
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4. Integrity of the SESSION_AUTH policy element
This section describes how to ensure the integrity of the policy
element is preserved.
4.1. Shared symmetric keys
In shared symmetric key environments, the AUTH_ENT_ID MUST be of
subtypes: IPV4_ADDRESS, IPV6_ADDRESS, FQDN, ASCII_DN, UNICODE_DN or
URI. An example SESSION_AUTH object is shown below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0| Type = SESSION_AUTH |0|0|0|0| Object Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_ENT_ID | IPV4_ADDRESS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (The authorizing entity's Identifier) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_DATA | zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| KEY_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (Authentication data) |
+---------------------------------------------------------------+
4.1.1. Operational Setting using shared symmetric keys
This assumes both the Authorizing Entity and the Network router/PDP
(Policy Decision Point) are provisioned with shared symmetric keys
and with policies detailing which algorithm to be used for computing
the authentication data along with the expected length of the
authentication data for that particular algorithm.
Key maintenance is outside the scope of this document, but
SESSION_AUTH implementations MUST at least provide the ability to
manually configure keys and their parameters. The key used to
produce the authentication data is identified by the AUTH_ENT_ID
field. Since multiple keys may be configured for a particular
AUTH_ENT_ID value, the first 32 bits of the AUTH_DATA field MUST be a
key ID to be used to identify the appropriate key. Each key must
also be configured with lifetime parameters for the time period
within which it is valid as well as an associated cryptographic
algorithm parameter specifying the algorithm to be used with the key.
At a minimum, all SESSION_AUTH implementations MUST support the HMAC-
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SHA2-256 [RFC4868] [RFC2104] cryptographic algorithm for computing
the authentication data.
It is good practice to regularly change keys. Keys MUST be
configurable such that their lifetimes overlap allowing smooth
transitions between keys. At the midpoint of the lifetime overlap
between two keys, senders should transition from using the current
key to the next/longer-lived key. Meanwhile, receivers simply accept
any identified key received within its configured lifetime and reject
those that are not.
4.2. Kerberos
Since Kerberos [RFC4120] is widely used for end-user authorization,
e.g., in Windows domains, it is well suited for being used in the
context of user-based authorization for NSIS sessions. For instance,
a user may request a ticket for authorization of installing rules in
an NATFW-capable router.
In a Kerberos environment, it is assumed that the user of the
requesting NSLP host requests a ticket from the (the Kerberos Key
Distribution Center - KDC) for using the NSLP Node (router) as
resource (target service). The NSLP requesting host (client) can
present the ticket to the NSLP node via Kerberos by sending a
KRB_CRED message to the NSLP node independently but prior to the NSLP
exchange. Thus, the principal name of the service must be known at
the client in advance, though the exact IP address may not be known
in advance. How the name is assigned and made available to the
client is implementation specific. The extracted common session key
can subsequently be used for using the HMAC_SIGNED variant of the
SESSION_AUTH object.
Another option is to encapsulate the credentials in the AUTH_DATA
portion of the SESSION_AUTH object. In this case the AUTH_ENT_ID
MUST be of the subtype KRB_PRINCIPAL. The KRB_PRINCIPAL field is
defined as the Fully Qualified Kerberos Principal name of the
authorizing entity. The AUTH_DATA portion of the SESSION_AUTH object
contains the KRB_CRED message that the receiving NSLP node has to
extract and verify. A second SESSION_AUTH object of type HMAC_SIGNED
SHOULD protect the integrity of the NSLP message, including the prior
SESSION_AUTH object. The session key included in the first
SESSION_AUTH object has to be used for HMAC calculation.
An example of the Kerberos AUTH_DATA policy element is shown below in
Figure 1.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0| Type = SESSION_AUTH |0|0|0|0| Object Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_ENT_ID | KERB_P. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (The principal@realm name) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_DATA | zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (KRB_CRED Data) |
+---------------------------------------------------------------+
Figure 1
4.3. Public Key
In a public key environment, the AUTH_ENT_ID MUST be of the subtypes:
X509_V3_CERT or PGP_CERT. The authentication data is used for
authenticating the authorizing entity. Two examples of the public
key SESSION_AUTH policy element are shown in Figure 2 and Figure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0| Type = SESSION_AUTH |0|0|0|0| Object Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_ENT_ID | PGP_CERT |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (Authorizing entity Digital Certificate) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_DATA | zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (Authentication data) |
+---------------------------------------------------------------+
Example of a SESSION_AUTH_OBJECT using a PGP Certificate
Figure 2
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0| Type = SESSION_AUTH |0|0|0|0| Object Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_ENT_ID | X509_V3_CERT |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (Authorizing entity Digital Certificate) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_DATA | zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OctetString ... (Authentication data) |
+---------------------------------------------------------------+
Example of a SESSION_AUTH_OBJECT using an X509_V3_CERT Certificate
Figure 3
4.3.1. Operational Setting for public key based authentication
Public key based authentication assumes the following:
o Authorizing entities have a pair of keys (private key and public
key).
o Private key is secured with the authorizing entity.
o Public keys are stored in digital certificates and a trusted
party, certificate authority (CA) issues these digital
certificates.
o The verifier (PDP or router) has the ability to verify the digital
certificate.
Authorizing entity uses its private key to generate
AUTHENTICATION_DATA. Authenticators (router, PDP) use the
authorizing entity's public key (stored in the digital certificate)
to verify and authenticate the policy element.
4.3.1.1. X.509 V3 digital certificates
When the AUTH_ENT_ID is of type X509_V3_CERT, AUTHENTICATION_DATA
MUST be generated by the authorizing entity following these steps:
o A Signed-data is constructed as defined in RFC5652 [RFC5652]. A
digest is computed on the content (as specified in Section 6.1)
with a signer-specific message-digest algorithm. The certificates
field contains the chain of authorizing entity's X.509 V3 digital
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certificates. The certificate revocation list is defined in the
crls field. The digest output is digitally signed following
Section 8 of RFC 3447 [RFC3447], using the signer's private key.
When the AUTH_ENT_ID is of type X509_V3_CERT, verification at the
verifying network element (PDP or router) MUST be done following
these steps:
o Parse the X.509 V3 certificate to extract the distinguished name
of the issuer of the certificate.
o Certification Path Validation is performed as defined in Section 6
of RFC 5280 [RFC5280].
o Parse through the Certificate Revocation list to verify that the
received certificate is not listed.
o Once the X.509 V3 certificate is validated, the public key of the
authorizing entity can be extracted from the certificate.
o Extract the digest algorithm and the length of the digested data
by parsing the CMS signed-data.
o The recipient independently computes the message digest. This
message digest and the signer's public key are used to verify the
signature value.
This verification ensures integrity, non-repudiation and data origin.
4.3.1.2. PGP digital certificates
When the AUTH_ENT_ID is of type PGP_CERT, AUTHENTICATION_DATA MUST be
generated by the authorizing entity following these steps:
AUTHENTICATION_DATA contains a Signature Packet as defined in Section
5.2.3 of RFC 4880 [RFC4880]. In summary:
o Compute the hash of all data in the SESSION_AUTH policy element up
to the AUTHENTICATION_DATA.
o The hash output is digitally signed following Section 8 of RFC
3447, using the signer's private key.
When the AUTH_ENT_ID is of type PGP_CERT, verification MUST be done
by the verifying network element (PDP or router) following these
steps:
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o Validate the certificate.
o Once the PGP certificate is validated, the public key of the
authorizing entity can be extracted from the certificate.
o Extract the hash algorithm and the length of the hashed data by
parsing the PGP signature packet.
o The recipient independently computes the message digest. This
message digest and the signer's public key are used to verify the
signature value.
This verification ensures integrity, non-repudiation and data origin.
4.4. HMAC Signed
A SESSION_AUTH object that carries an AUTH_ENT_ID of HMAC_SIGNED is
used as integrity protection for NSLP messages. The SESSION_AUTH
object MUST contain the following attributes:
o SOURCE_ADDR the source address of the entity that created the HMAC
o START_TIME the timestamp when the HMAC signature was calculated.
This MUST be different for any two messages in sequence in order
to prevent replay attacks. Since the NTP timestamp provides
currently a resolution of 200 pico seconds this should be
sufficient.
o NSLP_OBJECT_LIST this attribute lists all NSLP objects that are
included into HMAC calculation.
o AUTHENTICATION_DATA this attribute contains the Key-ID that is
used for HMAC calculation as well as the HMAC data itself
[RFC2104].
The key used for HMAC calculation must be exchanged securely by some
other means, e.g., a Kerberos Ticket or pre-shared manual
installation etc. The Key-ID in the AUTHENTICATION_DATA allows the
reference to the appropriate key and also to periodically change
signing keys within a session. The key length MUST be 64-bit at
least, but it is ideally longer in order to defend against brute
force attacks during the key validity period. For scalability
reasons it is suggested to use a per-user key for signing NSLP
messages, but using a per-session key is possible, too, at the cost
of a per-session key exchange. A per-user key allows for
verification of the authenticity of the message and thus provides a
basis for a session-based per-user authorization. It is RECOMMENDED
to periodically change the shared key in order to prevent
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eavesdroppers from performing a brute force off-line attacks on the
shared key. The actual hash algorithm used in the HMAC computation
is specified by the "Transform ID" field (given as Transform Type 3
of the IKEv2 registry [RFC4306]). The hash algorithm MUST be chosen
consistently between the object creator and the NN verifying the
HMAC; this can be accomplished by out-of-band mechanisms when the
shared key is exchanged.
Figure 4 shows an example of an object that is used for integrity
protection of NSLP messages.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0| Type = SESSION_AUTH |0|0|0|0| Object Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AUTH_ENT_ID | HMAC_SIGNED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| reserved | Transform ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | SOURCE_ADDR | IPV4_ADDRESS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Source Address of NSLP sender |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | START_TIME | NTP_TIME_STAMP|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP Time Stamp (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP Time Stamp (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | NSLP_OBJ_LIST | zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|No. of signed NSLP objects = n | rsv | NSLP object type (1) |
+-------+-------+---------------+-------+-------+---------------+
| rsv | NSLP object type (2) | ..... //
+-------+-------+---------------+---------------+---------------+
| rsv | NSLP object type (n) | (padding if required) |
+--------------+----------------+---------------+---------------+
| Length | AUTH_DATA | zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| KEY_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Authentication Code HMAC Data |
+---------------------------------------------------------------+
Example of a SESSION_AUTH_OBJECT that provides integrity protection
for NSLP messages
Figure 4
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5. Framework
RFC3521 [RFC3521] describes a framework in which the SESSION_AUTH
policy element may be utilized to transport information required for
authorizing resource reservation for data flows (e.g., media flows).
RFC3521 introduces 4 different models:
1. The coupled model
2. The associated model with one policy server
3. The associated model with two policy servers
4. The non-associated model.
The fields that are required in a SESSION_AUTH policy element depend
on which of the models is used.
5.1. The Coupled Model
In the coupled model, the only information that MUST be included in
the policy element is the SESSION_ID; it is used by the Authorizing
Entity to correlate the resource reservation request with the media
authorized during session set up. Since the End Host is assumed to
be untrusted, the Policy Server SHOULD take measures to ensure that
the integrity of the SESSION_ID is preserved in transit; the exact
mechanisms to be used and the format of the SESSION_ID are
implementation dependent.
5.2. The associated model with one policy server
In this model, the contents of the SESSION_AUTH policy element MUST
include:
o A session identifier - SESSION_ID. This is information that the
authorizing entity can use to correlate the resource request with
the data flows authorized during session set up.
o The identity of the authorizing entity - AUTH_ENT_ID. This
information is used by an NN to determine which authorizing entity
(Policy Server) should be used to solicit resource policy
decisions.
In some environments, an NN may have no means for determining if the
identity refers to a legitimate Policy Server within its domain. In
order to protect against redirection of authorization requests to a
bogus authorizing entity, the SESSION_AUTH MUST also include:
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AUTHENTICATION_DATA. This authentication data is calculated over
all other fields of the SESSION_AUTH policy element.
5.3. The associated model with two policy servers
The content of the SESSION_AUTH Policy Element is identical to the
associated model with one policy server.
5.4. The non-associated model
In this model, the SESSION_AUTH MUST contain sufficient information
to allow the Policy Server to make resource policy decisions
autonomously from the authorizing entity. The policy element is
created using information about the session by the authorizing
entity. The information in the SESSION_AUTH policy element MUST
include:
o Initiating party IP address or Identity (e.g., FQDN) - SOURCE_ADDR
X-TYPE
o Responding party IP address or Identity (e.g., FQDN) - DEST_ADDR
X-TYPE
o The authorization lifetime - START_TIME X-TYPE
o The identity of the authorizing entity to allow for validation of
the token in shared symmetric key and Kerberos schemes -
AUTH_ENT_ID X-TYPE
o The credentials of the authorizing entity in a public-key scheme -
AUTH_ENT_ID X-TYPE
o Authentication data used to prevent tampering with the
SESSION_AUTH policy element - AUTHENTICATION_DATA
Furthermore, the SESSION_AUTH policy element MAY contain:
o The lifetime of (each of) the media stream(s) - END_TIME X-TYPE
o Initiating party port number - SOURCE_ADDR X-TYPE
o Responding party port number - DEST_ADDR X-TYPE
All SESSION_AUTH fields MUST match with the resource request. If a
field does not match, the request SHOULD be denied.
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6. Message Processing Rules
This section discusses the message processing related to the
SESSION_AUTH object. Details of the processing the SESSION_AUTH
object within QoS NSLP and NAT/FW NSLP are described. New NSLP
protocols should use the same logic in making use of the SESSION_AUTH
object.
6.1. Generation of the SESSION_AUTH by the authorizing entity
1. Generate the SESSION_AUTH policy element with the appropriate
contents as specified in Section 3.
2. If authentication is needed, the entire SESSION_AUTH policy
element is constructed, excluding the length, type and subtype
fields of the SESSION_AUTH field. Note that the message MUST
include a START_TIME to prevent replay attacks. The output of
the authentication algorithm, plus appropriate header
information, is appended as AUTHENTICATION_DATA attribute to the
SESSION_AUTH policy element.
6.2. Processing within the QoS NSLP
The SESSION_AUTH object may be used with QoS NSLP QUERY and RESERVE
messages to authorize the query operation for network resources, and
a resource reservation request, respectively.
Moreover, the SESSION_AUTH object may also be used with RESPONSE
messages in order to indicate that the authorizing entity changed the
original request. For example, the session start or end times may
have been modified, or the client may have requested authorization
for all ports, but the authorizing entity only allowed the use of
certain ports.
If the QoS NSIS Initiator (QNI) receives a RESPONSE message with a
SESSION_AUTH object, the QNI MUST inspect the SESSION_AUTH object to
see what authentication attribute was changed by an authorizing
entity. The QNI SHOULD also silently accept SESSION_AUTH objects in
RESPONSE message, which do not indicate any change to the original
authorization request.
6.2.1. Message Generation
A QoS NSLP message is created as specified in
[I-D.ietf-nsis-qos-nslp].
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1. The policy element received from the authorizing entity MUST be
copied without modification into the SESSION_AUTH object.
2. The SESSION_AUTH object (containing the policy element) is
inserted in the NSLP message in the appropriate place.
6.2.2. Message Reception
The QoS NSLP message is processed as specified in
[I-D.ietf-nsis-qos-nslp] with following modifications.
1. If the QNE is policy aware then it SHOULD use the Diameter QoS
application or the RADIUS QoS protocol to communicate with the
PDP. To construct the AAA message it is necessary to extract the
SESSION_AUTH object and the QoS related objects from the QoS NSLP
message and to craft the respective RADIUS or Diameter message.
The message processing and object format is described in the
respective RADIUS or Diameter QoS protocol, respectively. If the
QNE is policy unaware then it ignores the policy data objects and
continues processing the NSLP message.
2. If the response from the PDP is negative the request must be
rejected. A negative response in RADIUS is an Access-Reject and
in Diameter is based on the 'DIAMETER_SUCCESS' value in the
Result-Code AVP of the QoS-Authz-Answer (QAA) message. The QNE
must construct and send a RESPONSE message with the status of
authorization failure as specified in [I-D.ietf-nsis-qos-nslp].
3. Continue processing the NSIS message.
6.2.3. Authorization (QNE or PDP)
1. Retrieve the policy element from the SESSION_AUTH object. Check
the AUTH_ENT_ID type and SubType fields and return an error if
the identity type is not supported.
2. Verify the message integrity.
* Shared symmetric key authentication: The QNE or PDP uses the
AUTH_ENT_ID field to consult a table keyed by that field. The
table should identify the cryptographic authentication
algorithm to be used along with the expected length of the
authentication data and the shared symmetric key for the
authorizing entity. Verify that the indicated length of the
authentication data is consistent with the configured table
entry and validate the authentication data.
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* Public Key: Validate the certificate chain against the trusted
Certificate Authority (CA) and validate the message signature
using the public key.
* HMAC signed: The QNE or PDP uses the Key-ID field of the
AUTHENTICATION_DATA attribute to consult a table keyed by that
field. The table should identify the cryptographic
authentication algorithm to be used along with the expected
length of the authentication data and the shared symmetric key
for the authorizing entity. Verify that the indicated length
of the authentication data is consistent with the configured
table entry and validate the integrity of parts of the NSLP
message, i.e., session ID, MRI, NSLP ID and all other NSLP
elements listed in the NSLP_OBJECT_LIST authentication data as
well as the SESSION_AUTH object contents (cf. Section 6.4).
* Kerberos: If AUTH_DATA contains an encapsulated KRB_CRED
message (cf. Section 4.2), the integrity of the KRB_CRED
message can be verified within Kerberos itself. Moreover, an
additionally present SESSION_AUTH object using HMAC_SIGNED can
be used to verify the message integrity as described above.
3. Once the identity of the authorizing entity and the validity of
the service request has been established, the authorizing router/
PDP MUST then consult its authorization policy in order to
determine whether or not the specific request is authorized
(e.g., based on available credits, information in the
subscriber's database). To the extent to which these access
control decisions require supplementary information, routers/PDPs
MUST ensure that supplementary information is obtained securely.
4. Verify the requested resources do not exceed the authorized QoS.
6.2.4. Error Signaling
When the PDP (e.g., a RADIUS or Diameter server) fails to verify the
policy element then the appropriate actions described the respective
AAA document need to be taken.
The QNE node MUST return a RESPONSE message with the INFO_SPEC error
code Authorization Failure as defined in the QoS NSLP specification.
The QNE MAY include an INFO_SPEC Object Value Info to indicate which
SESSION_AUTH attribute created the error.
6.3. Processing with the NAT/FW NSLP
This section presents processing rules for the NAT/FW NSLP
[I-D.ietf-nsis-nslp-natfw].
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6.3.1. Message Generation
A NAT/FW NSLP message is created as specified in
[I-D.ietf-nsis-nslp-natfw].
1. The policy element received from the authorizing entity MUST be
copied without modification into the SESSION_AUTH object.
2. The SESSION_AUTH object (containing the policy element) is
inserted in the NATFW NSLP message in the appropriate place.
6.3.2. Message Reception
The NAT/FW NSLP message is processed as specified in
[I-D.ietf-nsis-nslp-natfw] with following modifications.
1. If the router is policy aware then it SHOULD use the Diameter
application or the RADIUS protocol to communicate with the PDP.
To construct the AAA message it is necessary to extract the
SESSION_AUTH element and the NATFW policy rule related objects
from the NSLP message and to craft the respective RADIUS or
Diameter message. The message processing and object format is
described in the respective RADIUS or Diameter protocols,
respectively. If the router is policy unaware then it ignores
the policy data objects and continues processing the NSLP
message.
2. Reject the message if the response from the PDP is negative. A
negative response in RADIUS is an Access-Reject and in Diameter
is based on the 'DIAMETER_SUCCESS' value in the Result-Code AVP.
3. Continue processing the NSIS message.
6.3.3. Authorization (Router/PDP)
1. Retrieve the SESSION_AUTH object and the policy element. Check
the PE type field and return an error if the identity type is not
supported.
2. Verify the message integrity.
* Shared symmetric key authentication: The Network router/PDP
uses the AUTH_ENT_ID field to consult a table keyed by that
field. The table should identify the cryptographic
authentication algorithm to be used along with the expected
length of the authentication data and the shared symmetric key
for the authorizing entity. Verify that the indicated length
of the authentication data is consistent with the configured
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table entry and validate the authentication data.
* Public Key: Validate the certificate chain against the trusted
Certificate Authority (CA) and validate the message signature
using the public key.
* HMAC signed: The QNE or PDP uses the Key-ID field of the
AUTHENTICATION_DATA attribute to consult a table keyed by that
field. The table should identify the cryptographic
authentication algorithm to be used along with the expected
length of the authentication data and the shared symmetric key
for the authorizing entity. Verify that the indicated length
of the authentication data is consistent with the configured
table entry and validate the integrity of parts of the NSLP
message, i.e., session ID, MRI, NSLP ID and all other NSLP
elements listed in the NSLP_OBJECT_LIST authentication data as
well as the SESSION_AUTH object contents (cf. Section 6.4).
* Kerberos: If AUTH_DATA contains an encapsulated KRB_CRED
message (cf. Section 4.2), the integrity of the KRB_CRED
message can be verified within Kerberos itself. Moreover, an
additionally present SESSION_AUTH object using HMAC_SIGNED can
be used to verify the message integrity as described above.
3. Once the identity of the authorizing entity and the validity of
the service request has been established, the authorizing router/
PDP MUST then consult its authorization policy in order to deter
mine whether or not the specific request is authorized. To the
extent to which these access control decisions require
supplementary information, routers/PDPs MUST ensure that
supplementary information is obtained securely.
6.3.4. Error Signaling
When the PDP (e.g., a RADIUS or Diameter server) fails to verify the
SESSION_AUTH element then the appropriate actions described the
respective AAA document need to be taken. The NATFW NSLP node MUST
return an error message of class 'Permanent failure' (0x5) with error
code 'Authorization failed' (0x02).
6.4. Integrity Protection of NSLP messages
The SESSION_AUTH object can also be used to provide an integrity
protection for every NSLP signaling message, thereby also
authenticating requests or responses. Assume that a user has
deposited a shared key at some NN. This NN can then verify the
integrity of every NSLP message sent by the user to the NN. Based on
this authentication the NN can apply authorization policies to
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actions like resource reservations or opening of firewall pinholes.
The sender of an NSLP message creates a SESSION_AUTH object that
contains AUTH_ENT_ID attribute set to HMAC_SIGNED (cf. Section 4.4)
and hashes with the shared key over all NSLP objects that need to be
protected and lists them in the NSLP_OBJECT_LIST. The SESSION_AUTH
object itself is also protected by the HMAC. By inclusion of the
SESSION_AUTH object into the NSLP message, the receiver of this NSLP
message can verify its integrity if it has the suitable shared key
for the HMAC. Any response to the sender should also be protected by
inclusion of a SESSION_AUTH object in order to prevent attackers
sending unauthorized responses on behalf of the real NN.
If a SESSION_AUTH object is present that has an AUTH_ENT_ID attribute
set to HMAC_SIGNED, the integrity of all NSLP elements listed in the
NSLP_OBJECT_LIST has to be checked, including the SESSION_AUTH object
contents itself. Furthermore, session ID, MRI, and NSLP ID have to
be included into the HMAC calculation, too, as specified in
Section 3.2.7. The key that is used to calculate the HMAC is
referred to by the Key ID included in the AUTH_DATA attribute. If
the provided timestamp in START_TIME is not recent enough or the
calculated HMAC differs from the one provided in AUTH_DATA the
message must be discarded silently and an error should be logged
locally.
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7. Security Considerations
This document describes a mechanism for session authorization to
prevent theft of service. There are three types of security issues
to consider: protection against replay attacks, integrity of the
SESSION_AUTH object, and the choice of the authentication algorithms
and keys.
The first issue, replay attacks, MUST be prevented. In the non-
associated model, the SESSION_AUTH object MUST include a START_TIME
field and the NNs as well as Policy Servers MUST support NTP to
ensure proper clock synchronization. Failure to ensure proper clock
synchronization will allow replay attacks since the clocks of the
different network entities may not be in sync. The start time is
used to verify that the request is not being replayed at a later
time. In all other models, the SESSION_ID is used by the Policy
Server to ensure that the resource request successfully correlates
with records of an authorized session. If a SESSION_AUTH object is
replayed, it MUST be detected by the policy server (using internal
algorithms) and the request MUST be rejected.
The second issue, the integrity of the policy element, is preserved
in untrusted environments by including the AUTHENTICATION_DATA
attribute in such environments.
In environments where shared symmetric keys are possible, they should
be used in order to keep the SESSION_AUTH policy element size to a
strict minimum, e.g., when wireless links are used. A secondary
option would be PKI authentication, which provides a high level of
security and good scalability. However, it requires the presence of
credentials in the SESSION_AUTH policy element which impacts its
size.
The SESSION_AUTH object can also serve to protect the integrity of
NSLP message parts by using the HMAC_SIGNED Authentication Data as
described in Section 6.4.
When shared keys are used, e.g., in AUTHENTICATION_DATA Section 4.1
or in conjunction with HMAC_SIGNED Section 4.4, it is important that
the keys are kept secret, i.e., they must be exchanged, stored, and
managed in a secure and confidential manner. If the key material is
disclosed authentication and integrity protection are useless.
Furthermore, security considerations for public key mechanisms using
the X.509 certificate mechanisms described in [RFC5280] apply.
Similarly, security considerations for PGP described in [RFC4880]
apply.
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Further security issues are outlined in RFC 4081 [RFC4081].
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8. IANA Considerations
The SESSION_AUTH_OBJECT NSLP Message Object type is specified as:
(IANA-TBD)
[TO BE REMOVED: This specification makes the following request to
IANA: Assign a new object value (SESSION_AUTH_OBJECT) for the
SESSION_AUTH object from the shared NSLP Message Objects sub-
registry: http://www.iana.org/assignments/nslp-parameters/
nslp-parameters.xhtml]
This document specifies an 8-bit Session authorization attribute type
(X-Type) field as well as 8-bit SubType fields per X-Type, for which
IANA is to create and maintain corresponding sub-registries for the
NSLP Session Authorization Object.
Initial values for the X-Type registry are given below and the
Registration Procedures according to [RFC5226] are specified as
follows:
Range Registration Procedures
----- ---------------------------
0-127 Specification Required
128-255 Private or Experimental Use
X-Type Description
-------- -------------------
0 Reserved
1 AUTH_ENT_ID
2 SESSION_ID
3 SOURCE_ADDR
4 DEST_ADDR
5 START_TIME
6 END_TIME
7 NSLP_OBJECT_LIST
8 AUTHENTICATION_DATA
9-127 Unassigned
128-255 Reserved
In the following registration procedures and initial values for the
SubType registries are specified.
Sub-registry: AUTH_ENT_ID (X-Type 1) SubType values
Range Registration Procedures
---------- -----------------------
0-127 Specification Required
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128-255 Private or Experimental Use
Registry:
SubType Description
-------- -------------
0 Reserved
1 IPV4_ADDRESS
2 IPV6_ADDRESS
3 FQDN
4 ASCII_DN
5 UNICODE_DN
6 URI
7 KRB_PRINCIPAL
8 X509_V3_CERT
9 PGP_CERT
10 HMAC_SIGNED
11-127 Unassigned
128-255 Reserved
Sub-registry: SOURCE_ADDR (X-Type 3) SubType values
Range Registration Procedures
---------- -----------------------
0-127 Specification Required
128-255 Private or Experimental Use
Registry:
SubType Description
-------- -------------
0 Reserved
1 IPV4_ADDRESS
2 IPV6_ADDRESS
3 UDP_PORT_LIST
4 TCP_PORT_LIST
5 SPI
6-127 Unassigned
128-255 Reserved
Sub-registry: DEST_ADDR (X-Type 4) SubType values
Range Registration Procedures
---------- ------------------------
0-127 Specification Required
128-255 Private or Experimental Use
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Registry:
0 Reserved
1 IPV4_ADDRESS
2 IPV6_ADDRESS
3 UDP_PORT_LIST
4 TCP_PORT_LIST
5 SPI
6-127 Unassigned
128-255 Reserved
Sub-registry: START_TIME (X-Type 5) SubType values
Range Registration Procedures
---------- -----------------------
0-127 Specification Required
128-255 Private or Experimental Use
Registry:
SubType Description
-------- -------------
0 Reserved
1 NTP_TIMESTAMP
2-127 Unassigned
128-255 Reserved
Sub-registry: END_TIME (X-Type 6) SubType values
Range Registration Procedures
---------- -----------------------
0-127 Specification Required
128-255 Private or Experimental Use
Registry:
SubType Description
-------- -------------
0 Reserved
1 NTP_TIMESTAMP
2-127 Unassigned
128-255 Reserved
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9. Acknowledgments
We would like to thank Xioaming Fu and Lars Eggert for provided
reviews and comments. Helpful comments were also provided by Gen-ART
reviewer Ben Campbell as well as Sean Turner and Tim Polk from the
Security Area. This document is largely based on the RFC 3520
[RFC3520] and credit therefore goes to the authors of RFC 3520,
namely Louis-Nicolas Hamer, Brett Kosinski, Bill Gage and Hugh Shieh.
Part of this work was funded by Deutsche Telekom Laboratories within
the context of the ScaleNet project.
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10. References
10.1. Normative References
[I-D.ietf-nsis-nslp-natfw]
Stiemerling, M., Tschofenig, H., Aoun, C., and E. Davies,
"NAT/Firewall NSIS Signaling Layer Protocol (NSLP)",
draft-ietf-nsis-nslp-natfw-25 (work in progress),
April 2010.
[I-D.ietf-nsis-ntlp]
Schulzrinne, H. and M. Stiemerling, "GIST: General
Internet Signalling Transport", draft-ietf-nsis-ntlp-20
(work in progress), June 2009.
[I-D.ietf-nsis-qos-nslp]
Manner, J., Karagiannis, G., and A. McDonald, "NSLP for
Quality-of-Service Signaling", draft-ietf-nsis-qos-nslp-18
(work in progress), January 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
10.2. Informative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC3520] Hamer, L-N., Gage, B., Kosinski, B., and H. Shieh,
"Session Authorization Policy Element", RFC 3520,
April 2003.
[RFC3521] Hamer, L-N., Gage, B., and H. Shieh, "Framework for
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Session Set-up with Media Authorization", RFC 3521,
April 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4080] Hancock, R., Karagiannis, G., Loughney, J., and S. Van den
Bosch, "Next Steps in Signaling (NSIS): Framework",
RFC 4080, June 2005.
[RFC4081] Tschofenig, H. and D. Kroeselberg, "Security Threats for
Next Steps in Signaling (NSIS)", RFC 4081, June 2005.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120,
July 2005.
[RFC4514] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP): String Representation of Distinguished Names",
RFC 4514, June 2006.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
Thayer, "OpenPGP Message Format", RFC 4880, November 2007.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, September 2009.
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Appendix A. Changes
[Note to the RFC Editor: this appendix to be removed before
publication as an RFC.]
This section describes changes between draft versions.
-00: based on draft-manner-nsis-nslp-auth-04
* removed extensibility flag handling directives as the NSLPs are
responsible
* added IANA-TBD flag and SESSION_AUTH_OBJ
* changed Kerberos section
* removed calling/called party
* updated text in IANA section: removed "This specification uses
two X-types introduced by RFC3520: Session_ID and Resources."
as it may worry IANA (no action required)
* other small additions and fixes
* Updated Jukka's contact info
-01:
* addressed Xiaoming's comments of 2010-02-17
http://www.ietf.org/mail-archive/web/nsis/current/msg08726.html
* removed resource reservation specific text and used them as
examples
* removed referral to checksum and used MAC instead
* specified action if AUTH_ENT_ID or sub type are not known
* added missing _ in AUTH_SESSION
-02:
* changed intended category to experimental, because other NSIS
protocols are now in this category.
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* added text in Section 4.2 for Kerberos usage
* added more references to quoted RFCs
* moved Changes to Appendix
-03:
* Incorporated Lars Eggert's comments from AD review.
* added SESSION_ID to 3.2 with some clarifying text
* removed RESOURCES from section 5.4 since it is not directly
applicable in the NSIS context
-04:
* Updated references to new RFC 5905 (NTP), RFC 4880 (OpenPGP
Message Format), RFC 5280 (PKIX Certificate and CRL Profile)
* changed IPR to trust200902
-05:
* Replaced one remnant of RFC 2440 by RFC 4880
-06:
* Added a registry description in IANA Considerations section 8
* Relabeled AUTH_SESSION to SESSION_AUTH to better match the
verbose name of the object and to distinguish from RFC 3520
* added description for SESSION_ID (new sec. 3.2.2)
* removed a superfluous sentence in NSLP_OBJECT_LIST definition
(former sec. 3.2.6)
* fixed a typo in figure 1 (was NTLP_OBJ_LIST)
* added clarification sentences for HMAC_SIGNED in sections 6.4
and 7
-07:
* Addressed comments of Gen-ART review by Ben Campell:
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+ clarified order requirements on NSLP object list and
computing the hash
+ changed required minimum Hash implementation from HMAC-MD5
to HMAC-SHA2-256
+ clarified Section 6.4, 1st paragraph authentication vs.
authorization
+ removed MUST in Section 7, 3rd paragraph
(AUTHENTICATION_DATA is not always required)
* Addressed comments of Sean Turners review:
+ added Hash Signed and Kerberos usage to Sections 6.2.3, 2.
and 6.3.3, 2.
+ added security considerations for symmetric and public keys
+ capitalized some occurrences of MUST and RECOMMENDED
+ added figure for SESSION_AUTH object with X509_V3_CERT
+ added figure numbers for SESSION_AUTH object examples in
section 4
* many editorial nits
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Authors' Addresses
Jukka Manner
Aalto University
P.O. Box 13000
Aalto FI-00076
Finland
Phone: +358 9 470 22481
Email: jukka.manner@tkk.fi
Martin Stiemerling
Network Laboratories, NEC Europe Ltd.
Kurfuersten-Anlage 36
Heidelberg 69115
Germany
Phone: +49 (0) 6221 4342 113
Email: stiemerling@nw.neclab.eu
URI: http://www.stiemerling.org
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Roland Bless (editor)
Karlsruhe Institute of Technology
Institute of Telematics
Zirkel 2, Building 20.20
P.O. Box 6980
Karlsruhe 76049
Germany
Phone: +49 721 608 6413
Email: roland.bless@kit.edu
URI: http://tm.kit.edu/~bless
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