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Network Working Group                                            S. Hole
Internet Draft: ACAP Authid Dataset Classes         The Esys Corporation
Document: draft-ietf-acap-authid-01.txt                       March 1998
                                                     Expires in 6 months


             ACAP Authorization Identifier Dataset Classes


Status of this memo

     This document is an Internet Draft.  Internet Drafts are working
     documents of the Internet Engineering Task Force (IETF), its Areas,
     and its Working Groups.  Note that other groups may also distribute
     working documents as Internet Drafts.

     Internet Drafts are draft documents valid for a maximum of six
     months.  Internet Drafts may be updated, replaced, or obsoleted by
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     Drafts as reference material or to cite them other than as a
     ``working draft'' or ``work in progress``.

     To learn the current status of any Internet-Draft, please check the
     1id-abstracts.txt listing contained in the Internet-Drafts Shadow
     Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
     munnari.oz.au.

     Discussion and suggestions for improvement are requested.  This
     document will expire six months after publication.  Distribution of
     this draft is unlimited.


0. Administrivia

0.1.  Changes from Last Internet Draft

1)   Added a glossary of terms section at the beginning.



2)   Changed the group.members attribute of a groupid entry from a
     multivalued attribute to a subdataset attribute.   This is to
     address the scaling issues of very large groups, insertion and
     deletion.   Each entry in the subdataset refers to a member --
     either a userid or groupid.   The namespace for userid and groupid
     is separated by prefixing all userid member references with the
     "userid." prefix string, and all groupid member references are
     prefixed with a "groupid."  string.



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3)   Punted on the issue of recursive or circular group references.   It
     is up to the agent using the group information to do spanning tree
     calculations and/or set reductions to arrive at a unique membership
     list.  This MAY include the ACAP server itself if it uses the
     authid dataset classes for authorization information.


0.2.  Open Issues


1)   Need to review the group membership namespace solution.   The
     current model is quite flexible and should be capable of mapping
     all known group membership models.   The calculation for resolving
     to a unique list of users from a set of group references might need
     some discussion.


1. Introduction

     Most distributed (client/server) applications require an
     authentication process between the client and the server before the
     server will grant access to its managed resources.  Many
     applications provide varying levels of access to server resources
     based on a combination of authentication credentials and access
     control rules.   The collection of information used to control
     access to resources is called "authorization information".

     The ACAP authorization identifier datasets offers a more powerful,
     secure, and user friendly representation for authorization
     information than simple authentication identifiers in distributed
     applications.  The authorization identifer datasets contain lists
     of users and groups of users that can be used by applications for
     authorization purposes.  Access control mechanisms can be
     abstracted from underlying authentication mechanisms and credential
     formats.  They can be extended to include group memberships in
     dynamic calculations for access rights to resources or in
     definition of one time authorization certificates.

     The Application Configuration Access Protocol (ACAP) supports the
     remote storage and access of many types of structured configuration
     information.  The authorization identifier datasets specification
     describes the "userid" and "groupid" datasets which contain the
     authorization information.  It also describes ACAP server
     capabilities that advertise a server's support for authorization
     user and group semantics.


2. Conventions used in this document



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     The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
     in this document are to be interpreted as described in [KEYWORD].

     The attribute syntax specifications use the Augmented Backus-Naur
     Form (ABNF) notation as specified in [ABNF].


3. Definition of Terms

     Historically, different operating and network systems have used
     authentication and authorization terminology interchangeably.  They
     often did not distinguish between authentication and authorization,
     binding both into a single process.  Terms like "userid",
     "username", "login", "access" and others are used and mean somewhat
     different things in different systems.

     Following is an introductory glossary of the terminology used by
     this specification.  The terminology is defined specifically for
     Internet client/server applications, although the terminology could
     be applied to any application.  It reuses some historical terms,
     but defines each with a specific role, scope and usage.


3.1.  Authentication and authorization model

     Granting access to server resources in a client/server application
     is a two step process.  Step 1 is called "authentication", Step 2
     is "authorization".  Step 1 is performed once per session and
     establishes the identity of the individual that desires to access
     server resources.  Step 2 may be executed many times as access
     rights for the authenticated client are calculated for different
     resources managed by the server.

     In the ACAP model, authentication information is held independently
     of and bound too authorization information using the ACAP
     authorization identifiers.


3.2.  Glossary of Terms


authid

     The "authentication identifier" used to uniquely identify the
     individual connecting to a service.   The syntax and semantics of
     authids are specific to a particular authentication mechanism,
     network, and/or host operating system.




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userid

     The "authorization user identifier" used to identify an individual
     that a service will grant access rights to for its managed
     resources.  The syntax and semantics of ACAP userids are
     application independent.



groupid

     The "authorization group identifier" used to identify a set of
     individuals and/or groups that a service will grant access rights
     to for its managed resources.  The syntax and semantics of ACAP
     groupids are application independent.



rights

     The type of access that an individual is granted to a resource.
     The specific rights that can be granted to a resource is
     application specific.



ACL

     An "access control list" is a set of rules that binds an
     authorization id (authid, groupid) to a set of rights.   The form
     and content of ACLs are application specific.



authentication

     The negotiation between a client and server application that
     unambiguously establishes the identity of the client and server
     parties.



authorization

     The calculation performed by the server to grant access rights to a
     resource for an authenticated client.





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4. Authorization user identifiers

     An ACAP "userid" (user identifier) is an abstraction for an
     individual user that accesses server resources -- an authorization
     user.  Typically, this is a person acting as him or herself, a
     person acting in a role, or an application process.  Access rights
     to server resources can be granted or denied to a userid.

     Authentication information is tied to a userid by an authentication
     mechanism specific "authid" (authentication identifier).  More than
     one authid can be associated with a single userid.

     Userids can be listed and displayed by a client without giving away
     critical information on authentication information -- specifically
     lists of authids.   Using ACAP access control lists, the authids
     tied to a userid MAY be searched by a client but SHOULD NOT be
     retrievable by a client.


3.1. ACAP userid dataset class

     Datasets whose names begin with "/userid" contain "userid" entries
     as defined in this specification.  If present, an ACAP server
     SHOULD calculate access rights for its own information resources
     using the authorization information in this dataset.


3.2. Userid entry attributes

     A "userid" entry defines an authorization user for an application.
     It is used by the application to grant or deny access to
     application resources.  An application supporting ACAP "USER"
     authorization semantics (as defined in section 5.) binds userids to
     its resource access control rules.  Resource access rights are
     calculated by applying, in an application specific way, the access
     control rules that are bound to the current user's userid.


3.2.1.  Mandatory userid attributes


entry

     The "entry" attribute MUST be defined for a userid entry.  It's
     value is used by applications to calculate access rights to server
     resources.  This SHOULD include the ACAP server itself.  The syntax
     for the "entry" attribute is defined in [ACAP].




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userid.authid

     The "userid.authid" attribute MUST be defined for userid entry.  It
     MAY be multivalued.  It contains a list of authentication mechanism
     specific authentication identifiers that bind to this userid.

     userid-authid ::= 1*TEXT_UTF8_CHAR
                       ;; multi-valued

3.2.2.  Optional userid attributes

userid.displayname

     The "userid.displayname" attribute MAY be defined for a userid
     entry.  It contains a name string which is suitable for
     presentation by an ACAP client.  If present in a userid entry,
     clients SHOULD present this value to the user rather than the value
     of the "entry" attribute.  It is assumed to contain a more
     descriptive label for the user than the userid itself, eg. the
     user's full name.

     userid-displayname ::= 1*TEXT_UTF8_CHAR


userid.description

     The "userid.description" attribute MAY be defined for a userid
     entry.  It MUST be single valued.  The value contains text that
     provides an extended description of the user.  This information can
     be presented to a user to assist them in disambiguating userid
     entries with similar (or identical) "userid.displayname" attribute
     values.

     userid-description ::= 1*TEXT_UTF8_CHAR


userid.whitepage-info

     The "userid.whitepage-info" attribute MAY be defined for a userid
     entry.  It MAY be multivalued.  The value contains one or more
     URL's that reference whitepages information for the user.  There
     are no restrictions on the type of the URL, but it is most likely
     that the URL will be either an ACAP URL pointing to an addressbook
     dataset class entry or an LDAP URL pointing to a person entry.
     This information can be presented to a user to assist them in
     disambiguating userid entries with similar (or identical)
     "userid.displayname" attribute values.




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     userid-whitepage-info ::= relativeURL
                       ;; as defined in [REL-URL]
                       ;; ACAP relative URL is defined in [ACAP]


userid.memberof

     The "userid.memberof" attribute MUST be defined for an entry if the
     server supports the ACAP "GROUP" authorization semantics.  The
     value of the attribute is the list of groupids that the userid is a
     member of.  It is provided as an optimization convenience to the
     client in the presence of group authorization semantics as defined
     in section 5.  The value is readonly and MUST be calculated by the
     server.

     userid-memberof ::= relativeURL
                        ;; as defined in [REL-URL]
                        ;; ACAP relative URL is defined in [ACAP]

4. Authorization group identifiers

     An ACAP "groupid" (group identifier) is an abstraction for a set of
     users that access server resources -- an authorization group.  A
     groupid entry contains a list of userids that are members of the
     group.  Access rights to server resources can be granted or denied
     to a groupid.


4.1. ACAP groupid dataset class

     Datasets whose names begin with "/groupid" are assumed to contain
     groupid entries as defined in this specification.  If present, an
     ACAP server SHOULD support group authorization semantics defined in
     section 5.


4.2. Groupid entry attributes

     A "groupid" entry defines an authorization group for an
     application.  It is used by an application to grant or deny access
     to application resources.  An application supporting ACAP "GROUP"
     authorization semantics (as defined in section 5.) binds groupids
     to its resource access control rules.  Resource access rights are
     calculated by applying, in an application specific way, the access
     control rules that are bound to the groupids that the current
     user's userid is a member of.

     Each "groupid" entry is a subdataset entry.   Each entry in the



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     subdataset is called a "member" and references either a userid or
     another groupid entry.


4.2.1.  Mandatory groupid attributes


entry

     The "entry" attribute MUST be defined for a groupid entry.  Its
     value is used by applications to calculate access rights to server
     resources.  This SHOULD include the ACAP server itself.   The
     syntax for the "entry" attribute is defined in [ACAP].



subdataset

     The "subdataset" attribute MUST be defined for a groupid entry.
     Its value is a relative URL pointing to a dataset whose entries are
     the members of the group.   The syntax for the "subdataset"
     attribute is defined in [ACAP].


4.2.2.  Optional groupid attributes


group.name

     The "group.name" attribute MAY be defined for a groupid entry.  It
     MUST be single valued.  It contains a name string which is suitable
     for presentation by an ACAP client.  If present in a groupid entry,
     clients SHOULD present this value to the user rather than the value
     of the "entry" attribute.  It is assumed to contain a more
     descriptive label for the group than the groupid itself, eg. the
     group's organizational title.

     groupid-name ::= 1*TEXT_UTF8_CHAR


group.description

     The "group.description" attribute MAY be defined for a groupid
     entry.  It MUST be single valued.   The value contains text that
     describes the group.

     groupid-description ::= 1*TEXT_UTF8_CHAR




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4.3.  Group member entry attributes


     An ACAP group is a subdataset whose entries enumerate the
     membership of the group.  Each entry references a user entry in the
     "/userid" dataset class, or a group entry in the "/groupid" dataset
     class.


4.3.1.  Mandatory member entry attributes

entry

     The "entry" attribute MUST be defined for a member entry.  In
     addition to the restrictions placed on "entry" by [ACAP], a member
     entry is constrained to be of the form "userid.<userid>" or
     "groupid.<groupid>", where "<userid>" is a userid entry defined in
     the "/userid" dataset and "<groupid>" is a groupid entry defined in
     the "/groupid" dataset.  The formal syntax for a member entry name
     is:

    group-member = userid-entry-ref / groupid-entry-ref

    groupid-entry-ref = "groupid." entry-name
                        # entry-name refers to an entry in the
                          "/groupid" dataset

    userid-entry-ref =  "userid." entry-name
                        # entry-name refers to an entry in the
                         "/userid" dataset


     Note that there are no restrictions on the membership of a group.
     A group may include itself as a member.   Elimination of recursive
     references to groups MUST be performed by the agent responsible for
     calculating group membership attributes like that defined in
     section 3.2.2, or by agents that use group information in rights
     calculations.


5. ACAP authorization

     The ACAP authorization information can be used by any application,
     including the ACAP server itself.  The following sections describe
     the use of the authorization identifier datasets by an ACAP
     application (client or server) itself.

     Other applications are assumed to provide their own definitions for



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     use of ACAP authorization information.  Specifically, they are
     expected to define how they notify clients that their access
     control mechanisms make use of ACAP authorization information
     datasets.


5.1. Userid access semantics

     If an ACAP server supports the "/userid" dataset, then it SHOULD
     use the authorization information provided by it for access control
     purposes.  After successful authentication to the ACAP server, an
     authorization userid should be selected as the "current user" for
     the ACAP server, either using the authid mapping information in the
     userid entries, or using explicit userid information supported by
     the authentication mechanism.  ACAP ACL's are based on userids
     rather than authids.  Resource access rights are calculated
     relative to the current userid.


5.1.1. ACAP "USER" capability

     If an ACAP server supports the "/userid" dataset and userid
     authorization semantics, then it MUST express the "USER" capability
     in an ACAP capability response.   The "USER" capability informs an
     ACAP client that it MUST use the "/userid" dataset contents for any
     ACL management on the server.   If a server does not express the
     "USER" capability, then the client will assume that the server uses
     authid information in ACL's.


5.2. Group access semantics

     If an ACAP server supports the "/groupid" dataset, then it SHOULD
     use the authentication information in it.  ACAP ACL's can include
     groupids in the ACL.  Resource access rights are calculated
     relative to the current userid, and all groups that the current
     userid is a member of.


5.2.1. ACAP "GROUP" capability

     If an ACAP server supports the "/groupid" dataset and userid
     authorization semantics, then it MUST express the "GROUP"
     capability in an ACAP capability response.   The "GROUP" capability
     informs an ACAP client that it MUST use the "/groupid" dataset
     contents for any ACL management on the server.   If a server does
     not express the "GROUP" capability, then the client will assume
     that the server does not support group semantics, and should not



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     present group information in ACAP ACL management functions.

     In addition, the server MUST support calculation of the
     "userid.memberof" attribute in the "/userid" dataset class entries.


6. References
[ACAP] Newman, C., Myers, J. G., "Application Configuration Access
    Protocol", RFC 2244, July 1997.

[KEYWORD] S. Bradner, "Key words for use in RFCs to Indicate Requirement
    Level", RFC 2119, March 1997.

[ABNF] Dave Crocker, P. Overell, "Augmented BNF for Syntax
    Specifications: ABNF", RFC 2234, July, 1997

[REL-URL] Fielding, "Relative Uniform Resource Locators", RFC 1808,
    UC Irvine, June 1995.


7. Security Considerations

     This specification defines a protocol for storing, accessing and
     managing application resource authorization information.  It is
     expected that this information will be used to grant and/or deny
     access to users and groups for server based resources.

     ACAP server access controls should be set correctly on userid entry
     attributes.  Clients SHOULD be able to search for userid entries
     based on authentication identifier attributes, but SHOULD NOT be
     able to retrieve any authentication identifier information.

     This specification does not define any kind of process, mechanism
     or protocol for authentication in distributed network applications.
     Use of the data and protocol elements described in this
     specification are to be used after successful authentication
     between the client and server.

     This specification does not discuss storage of any kind of
     authentication credentials, in the form of private keys, shared
     secrets or passwords in userid entries.   The information in the
     authid dataset is intended purely for authorization and access
     control purposes.


8. Acknowledgments

The authors would like to acknowledge the contributions made to this



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document.  Randy Gellens, for editorial comment and feedback on the
group membership model.   Chris Newman for editorial comment and
clarification of the security and access control rights issues for the
ACAP server itself.

9. Authors' Addresses

Steve Hole
The Esys Corporation
900 10040 - 104 St.
Edmonton, Alberta, T5J 0Z2, CANADA

Email: Steve.Hole@esys.ca






































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