Topics in Directories: Groups

Dr. Tom Barton

The University of Memphis

25 June 2002 Base CAMP 2

Outline

• What is it for?

• Design factors – how to approach the design of a groups implementation

• Examples & vignettes

• Group management issues

• Vaporware

• References

25 June 2002 Base CAMP 3

Why do groups?

Leverage existing enterprise directory infrastructure to:

• Supply data for access control policies to directory integrated applications and service platforms.

• Supply data for customization needs, especially CMSs and portals.

• Facilitate group messaging.• Facilitate automated IT resource provisioning.

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Design factors for a groups implementation

• How the group information is to be most commonly accessed.

• How the group information is to be maintained.

• How potential interactions arise between:• the type of group representation• the nature of the group (eg, size or privacy requirements)• capabilities of the particular directory service agent being

used

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Design factors:Representations of groups

• Static: group object with multivalued membership attribute.

• groupOfNames• groupOfUniqueNames

dn: cn=groupA, ou=groups, dc=some, dc=eduobjectclass: groupOfUniqueNamescn: groupAuniquemember: uid=user1,ou=people,dc=some,dc=eduuniquemember: uid=user2,ou=people,dc=some,dc=eduuniquemember: uid=user3,ou=people,dc=some,dc=edu

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Design factors:Representations of groups

• Dynamic: membership determined by executing an ldap url

• groupOfURLs (iPlanet proprietary)• No group object – ldap url exists only in applications using it.

dn: cn=groupB, ou=groups, dc=some, dc=eduobjectclass: groupOfURLscn: groupBmemberURL: ldap://ldap.some.edu389/ou=people, dc=some,dc=edu?dn?2?(ou=staff)

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Design factors:Representations of groups

• Forward reference: multivalued attribute (isMemberOf) in an object lists its memberships.

dn: uid=user1, ou=people, dc=some, dc=eduobjectclass: someEduPersoncn: Some Bodysn: Body uid: user1isMemberOf: groupAisMemberOf: groupB

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Design factors:Representations of groups

• Spatial: membership is inferred from object’s location in the DIT.

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Design factors:Application access questions

• How will applications query for group information?

• Is object X in group A?• List all members of group A.• List all groups to which X belongs.• List all members of some boolean combination of groups.

• List all members of group A meeting specified additional criteria.

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Design factors:Application access questions

• Are there application restrictions on:• group names• static group objectclass selection• ability to use object attributes (dynamic groups) • where in the DIT to look for group objects

• Are there application constraints impacting access policy?

• Can application BIND as a given user (aka serviceDN), enabling directory ACLs to accurately implement institutional access policy?

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Design factors:Group maintenance questions

• Will membership info be automatically maintained based upon institutional data?

• Will membership info be manually maintained?

• How will delegation of group update priviledges be managed?

• Is it a personal group?

• What institutional policy pertains to the visibility of the group or privacy of its membership information?

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Design factors:Group maintenance questions

• Both automatic and manual processes update the same group? Need a group maintenance application.

• Is there a need to hide personal groups from certain enterprise applications?

• Limited expressiveness of directory ACLs might limit ability to delegate maintenance of member object attributes without use of an intervening group maintenance application.

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Design factors:DSA interactions

• Size limit for static groups?

• Replication performance for large static groups.

• Processor and return size limits vs. listing membership of large dynamic groups.

• Access control language vs. delegated maintenance of dynamic (or forward reference) groups.

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Core middleware for an integrated architecture

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Example: Class website

Students & instructor(s) use a course website to support class activities. The website provides views only to those resources associated with the role they have in each class.

class: ENGL2101002.2002Uinstructor: uid=user1, …student: uid=user2, …student: uid=user3, …

class: COMP3214001.2002Uinstructor: uid=user4, …student: uid=user5, …student: uid=user6, …

SIS Metadirectory MyClass

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Example: Data Warehouse Access

GUI web reporting tool (BRIO) for DW access has native LDAP authentication, but groups used for application security are stored in the DW. Application level security priviledges are determined by combination of DW administrators and business office personnel.

owner: uid=DWadmin,…uniquemember: uid=user1, …uniquemember: uid=user2, …

owner: uid=BOadmin,…uniquemember: uid=user3, …uniquemember: uid=user4, …

DWGASP Duper BRIO

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Student vignette

Mary is a grad student at Alpha U, taking courses both in a traditional classroom and online and interns at a biotech company nearby. Using her laptop, Mary needs to access her e-mail, courseware, calendar and library resources from all three locations; home, campus and work. She also uses a wireless PDA when on-campus to stay in touch with her lab mates.

Mailbox

CalendarWireless Gateway

NAS Server

Lib Proxies

CMSauthN

attrs

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Provisioning vignette

The new Chair of the Dept. of Physiology has arrived on campus over the weekend. Dr. Agnew is very anxious to get access to campus IT resources such as e-mail, calendar, web services and the mainframe. He does not want to wait for the requisite 3-5 business days it takes to get the accounts setup. Since IT already knows of him, he can use a self-service interface to accomplish his goal.

HRS Metadirectory

Acct Init Service

authN

attrs

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Group management issues

• Maintenance & indexing of membership attributes

• Delegating management

• Referential integrity

• Personal groups

• Privacy & visibility

• Group math

• Forward referencing

• Aging

• Namespace issues

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Vapor groupware

GASP (Group Authorized Service Process). Utility that provides group create, rename, update, delete capabilities within an access controlled environment.

Grouper. Extension to DSA presenting group math capabilites to ldap clients.

RIbot. Referential Integrity maintenance utility. Maintains integrity of forward references too.

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References

Practices in Directory Groups – Tom Barton

LDAP Recipe 2.0 – Michael Gettes

(forthcoming) Groups Implementation Guide – Eileen Shepard