RFC 2752
Identity Representation for RSVP
Pages: 17
Obsoleted by: 3182
Obsoleted by: 3182
Network Working Group S. Yadav Request for Comments: 2752 R. Yavatkar Category: Standards Track Intel R. Pabbati P. Ford T. Moore Microsoft S. Herzog IPHighway January 2000 Identity Representation for RSVP Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved.Abstract
This document describes the representation of identity information in POLICY_DATA object [POL-EXT] for supporting policy based admission control in RSVP. The goal of identity representation is to allow a process on a system to securely identify the owner and the application of the communicating process (e.g. user id) and convey this information in RSVP messages (PATH or RESV) in a secure manner. We describe the encoding of identities as RSVP policy element. We describe the processing rules to generate identity policy elements for multicast merged flows. Subsequently, we describe representations of user identities for Kerberos and Public Key based user authentication mechanisms. In summary we describe the use of this identity information in an operational setting.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 [RFC-2119].
2. Introduction
RSVP [RFC 2205] is a resource reservation setup protocol designed for an integrated services Internet [RFC 1633]. RSVP is used by a host to request specific quality of service (QoS) from the network for particular application data streams or flows. RSVP is also used by routers to deliver QoS requests to all nodes along the path(s) of the flows and to establish and maintain state to provide the requested service. RSVP requests will generally result in resources being reserved in each node along the data path. RSVP allows particular users to obtain preferential access to network resources, under the control of an admission control mechanism. Permission to make a reservation is based both upon the availability of the requested resources along the path of the data and upon satisfaction of policy rules. Providing policy based admission control mechanism based on user identity or application is one of the prime requirements. In order to solve these problems and implement identity based policy control it is required to identify the user and/or application making a RSVP request. This document proposes a mechanism for sending identification information in the RSVP messages and enables authorization decisions based on policy and identity. We describe the authentication policy element (AUTH_DATA) contained in the POLICY_DATA object. User process can generate an AUTH_DATA policy element and gives it to RSVP process (service) on the originating host. RSVP service inserts AUTH_DATA into the RSVP message to identify the owner (user and/or application) making the request for network resources. Network elements, such as routers, authenticate request using the credentials presented in the AUTH_DATA and admit the RSVP message based on admission policy. After a request has been authenticated, first hop router installs the RSVP state and forwards the new policy element returned by the Policy Decision Point (PDP) [POL-FRAME].3. Policy Element for Authentication Data
3.1 Policy Data Object Format
POLICY_DATA objects contain policy information and are carried by RSVP messages. A detail description of the format of POLICY_DATA object can be found in "RSVP Extensions for Policy Control" [POL- EXT].
3.2 Authentication Data Policy Element
In this section, we describe a policy element (PE) called authentication data (AUTH_DATA). AUTH_DATA policy element contains a list of authentication attributes. +-------------+-------------+-------------+-------------+ | Length | P-Type = Identity Type | +-------------+-------------+-------------+-------------+ // Authentication Attribute List // +-------------------------------------------------------+ Length The length of the policy element (including the Length and P- Type) is in number of octets (MUST be a multiple of 4) and indicates the end of the authentication attribute list. P-Type (Identity Type) Type of identity information contained in this Policy Element supplied as the Policy element type (P-type). The Internet Assigned Numbers Authority (IANA) acts as a registry for policy element types for identity as described in the [POL-EXT]. Initially, the registry contains the following P-Types for identity: 1 AUTH_USER Authentication scheme to identify users 2 AUTH_APP Authentication scheme to identify applications Authentication Attribute List Authentication attributes contain information specific to authentication method and type of AUTH_DATA. The policy element provides the mechanism for grouping a collection of authentication attributes.3.3 Authentication Attributes
Authentication attributes MUST be encoded as a multiple of 4 octets, attributes that are not a multiple of 4 octets long MUST be padded to a 4-octet boundary. +--------+--------+--------+--------+ | Length | A-Type |SubType | +--------+--------+--------+--------+ | Value ... +--------+--------+--------+--------+
Length
The length field is two octets and indicates the actual length of
the attribute (including the Length and A-Type fields) in number
of octets. The length does not include any bytes padding to the
value field to make the attribute multiple of 4 octets long.
A-Type
Authentication attribute type (A-Type) field is one octet. IANA
acts as a registry for A-Types as described in the section 9,
IANA Considerations. Initially, the registry contains the
following A-Types:
1 POLICY_LOCATOR Unique string for locating the
admission policy (such as X.500 DN
described in [RFC 1779]).
2 CREDENTIAL User credential such as Kerberos
ticket, or digital certificate.
Application credential such as
application ID.
3 DIGITAL_SIGNATURE Digital signature of the
authentication data policy element.
4 POLICY_ERROR_OBJECT Detailed information on policy
failures.
SubType
Authentication attribute sub-type field is one octet. Value of
SubType depends on A-type.
Value:
The value field contains the attribute specific information.
3.3.1 Policy Locator
POLICY_LOCATOR is used to locate the admission policy for the user
or application. Distinguished Name (DN) is unique for each User or
application hence a DN is used as policy locator.
+-------+-------+-------+-------+
| Length |A-Type |SubType|
+-------+-------+-------+-------+
| OctetString ...
+-------+-------+-------+--------
Length
Length of the attribute, which MUST be >= 4.
A-Type
POLICY_LOCATOR
SubType
Following sub types for POLICY_LOCATOR are defined. IANA acts as
a registry for POLICY_LOCATOR sub types as described in the
section 9, IANA Considerations. Initially, the registry contains
the following sub types for POLICY_LOCATOR:
1 ASCII_DN OctetString contains the X.500 DN as described
in the RFC 1779 as an ASCII string.
2 UNICODE_DN OctetString contains the X.500 DN described in
the RFC 1779 as an UNICODE string.
3 ASCII_DN_ENCRYPT OctetString contains the encrypted X.500
DN. The Kerberos session key or digital
certificate private key is used for encryption.
For Kerberos encryption the format is the same
as returned from gss_seal [RFC 1509].
4 UNICODE_DN_ENCRYPT OctetString contains the encrypted
UNICODE X.500 DN. The Kerberos session key or
digital certificate private key is used for
encryption. For Kerberos encryption the format
is the same as returned from gss_seal [RFC
1509].
OctetString
The OctetString field contains the DN.
3.3.2 Credential
CREDENTIAL indicates the credential of the user or application to be
authenticated. For Kerberos authentication method the CREDENTIAL
object contains the Kerberos session ticket. For public key based
authentication this field contains a digital certificate.
A summary of the CREDENTIAL attribute format is shown below. The
fields are transmitted from left to right.
+-------+-------+-------+-------+
| Length |A-Type |SubType|
+-------+-------+-------+-------+
| OctetString ...
+-------+-------+-------+--------
Length
Length of the attribute, which MUST be >= 4.
A-Type
CREDENTIAL
SubType
IANA acts as a registry for CREDENTIAL sub types as described in
the section 9, IANA Considerations. Initially, the registry
contains the following sub types for CREDENTIAL:
1 ASCII_ID OctetString contains user or application
identification in plain ASCII text string.
2 UNICODE_ID OctetString contains user or application
identification in plain UNICODE text string.
3 KERBEROS_TKT OctetString contains Kerberos ticket.
4 X509_V3_CERT OctetString contains X.509 V3 digital
certificate [X.509].
5 PGP_CERT OctetString contains PGP digital certificate.
OctetString
The OctetString contains the user or application credential.
3.3.3 Digital Signature
The DIGITAL_SIGNATURE attribute MUST be the last attribute in the
attribute list and contains the digital signature of the AUTH_DATA
policy element. The digital signature signs all data in the
AUTH_DATA policy element up to the DIGITAL_SIGNATURE. The algorithm
used to compute the digital signature depends on the authentication
method specified by the CREDENTIAL SubType field.
A summary of DIGITAL_SIGNATURE attribute format is described below.
+-------+-------+-------+-------+
| Length |A-Type |SubType|
+-------+-------+-------+-------+
| OctetString ...
+-------+-------+-------+--------
Length
Length of the attribute, which MUST be >= 4.
ti3 A-Type
DIGITAL_SIGNATURE
SubType
No sub types for DIGITAL_SIGNATURE are currently defined. This
field MUST be set to 0.
OctetString
OctetString contains the digital signature of the AUTH_DATA.
3.3.4 Policy Error Object
This attribute is used to carry any specific policy control errors
generated by a node when processing/validating an Authentication Data
Policy Element. When a RSVP policy node (local policy decision point
or remote PDP) encounters a request that fails policy control due to
its Authentication Policy Element, it SHOULD add a POLICY_ERROR_CODE
containing additional information about the reason the failure
occurred into the policy element. This will then cause an appropriate
PATH_ERROR or RESV_ERROR message to be generated with the policy
element and appropriate RSVP error code in the message, which is
returned to the request's source.
The AUTH_DATA policy element in the PATH or RSVP message SHOULD not
contain the POLICY_ERROR_OBJECT attribute. These are only inserted
into PATH_ERROR and RESV_ERROR messages when generated by policy
aware intermediate nodes.
+----------+----------+----------+----------+
| Length | A-Type |SubType(0)|
+----------+----------+----------+----------+
| 0 (Reserved) | ErrorValue |
+----------+----------+----------+----------+
| OctetString ...
+----------+----------+----------+----------+
Length
Length of the attribute, which MUST be >= 8.
A-Type
POLICY_ERROR_CODE
ErrorValue
A 32-bit bit code containing the reason that the policy decision
point failed to process the policy element. Following values have
been defined.
1 ERROR_NO_MORE_INFO No information is available.
2 UNSUPPORTED_CREDENTIAL_TYPE This type of credentials is
not supported.
3 INSUFFICIENT_PRIVILEGES The credentials do not have
sufficient privilege.
4 EXPIRED_CREDENTIAL The credential has expired.
5 IDENTITY_CHANGED Identity has changed.
OctetString
The OctetString field contains information from the policy
decision point that MAY contain additional information about the
policy failure. For example, it may include a human-readable
message in the ASCII text.
4. Authentication Data Formats
Authentication attributes are grouped in a policy element to
represent the identity credentials.
4.1 Simple User Authentication
In simple user authentication method the user login ID (in plain
ASCII or UNICODE text) is encoded as CREDENTIAL attribute. A summary
of the simple user AUTH_DATA policy element is shown below.
+--------------+--------------+--------------+--------------+
| Length | P-type = AUTH_USER |
+--------------+--------------+--------------+--------------+
| Length |POLICY_LOCATOR| SubType |
+--------------+--------------+--------------+--------------+
| OctetString (User's Distinguished Name) ...
+--------------+--------------+--------------+--------------+
| Length |CREDENTIAL | ASCII_ID |
+--------------+--------------+--------------+--------------+
| OctetString (User's login ID) ...
+--------------+--------------+--------------+--------------+
4.2 Kerberos User Authentication
Kerberos [RFC 1510] authentication uses a trusted third party (the Kerberos Distribution Center - KDC) to provide for authentication of the user to a network server. It is assumed that a KDC is present and both host and verifier of authentication information (router or PDP) implement Kerberos authentication. A summary of the Kerberos AUTH_DATA policy element is shown below. +--------------+--------------+--------------+--------------+ | Length | P-type = AUTH_USER | +--------------+--------------+--------------+--------------+ | Length |POLICY_LOCATOR| SubType | +--------------+--------------+--------------+--------------+ | OctetString (User's Distinguished Name) ... +--------------+--------------+--------------+--------------+ | Length | CREDENTIAL | KERBEROS_TKT | +--------------+--------------+--------------+--------------+ | OctetString (Kerberos Session Ticket) ... +--------------+--------------+--------------+--------------+4.2.1. Operational Setting using Kerberos Identities
An RSVP enabled host is configured to construct and insert AUTH_DATA policy element into RSVP messages that designate use of the Kerberos authentication method (KERBEROS_TKT). Upon RSVP session initialization, the user application contacts the KDC to obtain a Kerberos ticket for the next network node or its PDP. A router when generating a RSVP message contacts the KDC to obtain a Kerberos ticket for the next hop network node or its PDP. The identity of the PDP or next network hop can be statically configured, learned via DHCP or maintained in a directory service. The Kerberos ticket is sent to the next network node (which may be a router or host) in a RSVP message. The KDC is used to validate the ticket and authentication the user sending RSVP message.4.3 Public Key based User Authentication
In public key based user authentication method digital certificate is encoded as user credentials. The digital signature is used for authenticating the user. A summary of the public key user AUTH_DATA policy element is shown below.
+--------------+--------------+--------------+--------------+ | Length | P-type = AUTH_USER | +--------------+--------------+--------------+--------------+ | Length |POLICY_LOCATOR| SubType | +--------------+--------------+--------------+--------------+ | OctetString (User's Distinguished Name) ... +--------------+--------------+--------------+--------------+ | Length | CREDENTIAL | SubType | +--------------+--------------+--------------+--------------+ | OctetString (User's Digital Certificate) ... +--------------+--------------+--------------+--------------+ | Length |DIGITAL_SIGN. | 0 | +--------------+--------------+--------------+--------------+ | OctetString (Digital signature) ... +--------------+--------------+--------------+--------------+4.3.1. Operational Setting for public key based authentication
Public key based authentication assumes following: - RSVP service requestors have a pair of keys (private key and public key). - Private key is secured with the user. - Public keys are stored in digital certificates and a trusted party, certificate authority (CA) issues these digital certificates. - The verifier (PDP or router) has the ability to verify the digital certificate. RSVP requestor uses its private key to generate DIGITAL_SIGNATURE. User Authenticators (router, PDP) use the user's public key (stored in the digital certificate) to verify the signature and authenticate the user.4.4 Simple Application Authentication
The application authentication method encodes the application identification such as an executable filename as plain ASCII or UNICODE text.
+----------------+--------------+--------------+--------------+ | Length | P-type = AUTH_APP | +----------------+--------------+--------------+--------------+ | Length |POLICY_LOCATOR| SubType | +----------------+--------------+--------------+--------------+ | OctetString (Application Identity attributes in | the form of a Distinguished Name) ... +----------------+--------------+--------------+--------------+ | Length | CREDENTIAL | ASCII_ID | +----------------+--------------+--------------+--------------+ | OctetString (Application Id, e.g., vic.exe) +----------------+--------------+--------------+--------------+5. Operation
+-----+ +-----+ | PDP |-------+ | PDP | +-----+ | ................... +-----+ | : : | +--------+ : Transit : +-------+ +----| Router |------: Network : -------| Router|--+ | +--------+ : : +-------+ | | | :.................: | | | | | | Host A B C D Figure 1: User and Application Authentication using AUTH_DATA PE Network nodes (hosts/routers) generate AUTH_DATA policy elements, contents of which are depend on the identity type used and the authentication method used. These generally contain authentication credentials (Kerberos ticket or digital certificate) and policy locators (which can be the X.500 Distinguished Name of the user or network node or application names). Network nodes generate AUTH_DATA policy element containing the authentication identity when making the RSVP request or forwarding a RSVP message. Network nodes generate user AUTH_DATA policy element using the following rules 1. For unicast sessions the user policy locator is copied from the previous hop. The authentication credentials are for the current network node identity. 2. For multicast messages the user policy locator is for the current network node identity. The authentication credentials are for the current network node.
Network nodes generate application AUTH_DATA policy element using the
following rules:
1. For unicast sessions the application AUTH_DATA is copied from the
previous hop.
2. For multicast messages the application AUTH_DATA is either the
first application AUTH_DATA in the message or chosen by the PDP.
6. Message Processing Rules
6.1 Message Generation (RSVP Host)
An RSVP message is created as specified in [RFC2205] with following
modifications.
1. RSVP message MAY contain multiple AUTH_DATA policy elements.
2. Authentication policy element (AUTH_DATA) is created and the
IdentityType field is set to indicate the identity type in the
policy element.
- DN is inserted as POLICY_LOCATOR attribute.
- Credentials such as Kerberos ticket or digital certificate are
inserted as the CREDENTIAL attribute.
3. POLICY_DATA object (containing the AUTH_DATA policy element) is
inserted in the RSVP message in appropriate place. If INTEGRITY
object is not computed for the RSVP message then an INTEGRITY
object SHOULD be computed for this POLICY_DATA object, as
described in the [POL_EXT], and SHOULD be inserted as a Policy
Data option.
6.2 Message Reception (Router)
RSVP message is processed as specified in [RFC2205] with following
modifications.
1. If router is not policy aware then it SHOULD send the RSVP message
to the PDP and wait for response. If the router is policy unaware
then it ignores the policy data objects and continues processing
the RSVP message.
2. Reject the message if the response from the PDP is negative.
3. Continue processing the RSVP message.
6.3 Authentication (Router/PDP)
1. Retrieve the AUTH_DATA policy element. Check the PE type field and return an error if the identity type is not supported. 2. Verify user credential - Simple authentication: e.g. Get user ID and validate it, or get executable name and validate it. - Kerberos: Send the Kerberos ticket to the KDC to obtain the session key. Using the session key authenticate the user. - Public Key: Validate the certificate that it was issued by a trusted Certificate Authority (CA) and authenticate the user or application by verifying the digital signature.7. Error Signaling
If PDP fails to verify the AUTH_DATA policy element then it MUST return policy control failure (Error Code = 02) to the PEP. The error values are described in [RFC 2205] and [POL-EXT]. Also PDP SHOULD supply a policy data object containing an AUTH_DATA Policy Element with A-Type=POLICY_ERROR_CODE containing more details on the Policy Control failure (see section 3.3.4). The PEP will include this Policy Data object in the outgoing RSVP Error message.8. IANA Considerations
Following the policies outlined in [IANA-CONSIDERATIONS], authentication attribute types (A-Type)in the range 0-127 are allocated through an IETF Consensus action, A-Type values between 128-255 are reserved for Private Use and are not assigned by IANA. Following the policies outlined in [IANA-CONSIDERATIONS], POLICY_LOCATOR SubType values in the range 0-127 are allocated through an IETF Consensus action, POLICY_LOCATOR SubType values between 128-255 are reserved for Private Use and are not assigned by IANA. Following the policies outlined in [IANA-CONSIDERATIONS], CREDENTIAL SubType values in the range 0-127 are allocated through an IETF Consensus action, CREDENTIAL SubType values between 128-255 are reserved for Private Use and are not assigned by IANA.
9. Security Considerations
The purpose of this memo is to describe a mechanism to authenticate RSVP requests based on user identity in a secure manner. RSVP INTEGRITY object is used to protect the policy object containing user identity information from security (replay) attacks. Combining the AUTH_DATA policy element and the INTEGRITY object results in a secure access control that enforces authentication based on both the identity of the user and the identity of the originating node. Simple authentication does not contain credential that can be securely authenticated and is inherently less secured. The Kerberos authentication mechanism is reasonably well secured. User authentication using a public key certificate is known to provide the strongest security.10. Acknowledgments
We would like to thank Andrew Smith, Bob Lindell and many others for their valuable comments on this memo.11. References
[ASCII] Coded Character Set -- 7-Bit American Standard Code for Information Interchange, ANSI X3.4- 1986. [IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [POL-EXT] Herzog, S., "RSVP Extensions for Policy Control", RFC 2750, January 2000. [POL-FRAME] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework for Policy-based Admission Control RSVP", RFC 2753, January 2000. [RFC 1510] Kohl, J. and C. Neuman, "The Kerberos Network Authentication Service (V5)", RFC 1510, September 1993. [RFC 1704] Haller, N. and R. Atkinson, "On Internet Authentication", RFC 1704, October 1994.
[RFC 1779] Killie, S., "A String Representation of Distinguished Names", RFC 1779, March 1995. [RFC 2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation Protocol (RSVP) - Version 1 Functional Specification", RFC 2205, September 1997. [RFC 2209] Braden, R. and L. Zhang, "Resource ReSerVation Protocol (RSVP) - Version 1 Message Processing Rules", RFC 2209, September 1997. [UNICODE] The Unicode Consortium, "The Unicode Standard, Version 2.0", Addison-Wesley, Reading, MA, 1996. [X.509] Housley, R., Ford, W., Polk, W. and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and CRL Profile", RFC 2459, January 1999. [X.509-ITU] ITU-T (formerly CCITT) Information technology - Open Systems Interconnection - The Directory: Authentication Framework Recommendation X.509 ISO/IEC 9594-8
12. Author Information
Satyendra Yadav Intel, JF3-206 2111 NE 25th Avenue Hillsboro, OR 97124 EMail: Satyendra.Yadav@intel.com Raj Yavatkar Intel, JF3-206 2111 NE 25th Avenue Hillsboro, OR 97124 EMail: Raj.Yavatkar@intel.com Ramesh Pabbati Microsoft 1 Microsoft Way Redmond, WA 98054 EMail: rameshpa@microsoft.com Peter Ford Microsoft 1 Microsoft Way Redmond, WA 98054 EMail: peterf@microsoft.com Tim Moore Microsoft 1 Microsoft Way Redmond, WA 98054 EMail: timmoore@microsoft.com Shai Herzog IPHighway, Inc. 55 New York Avenue Framingham, MA 01701 EMail: herzog@iphighway.com
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