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       dacs.groups - DACS groups


       These files are part of the DACS suite.

       Groups are a convenient shorthand for a jurisdiction's administrator to use when
       specifying access control rules. Rather than explicitly listing the set of users who have
       certain access rights to a service, an administrator can reference a group name that
       represents the membership of the set. The set's membership is built dynamically and
       consists of any combination of users and other group names. The membership of a particular
       group may vary over time and is resolved when a service request is subjected to access
       control. A jurisdiction may define any number of groups and specify their membership;
       these definitions may then be referenced by other jurisdictions, in their access control
       rules and their group definitions. It is the task of the DACS group membership service to
       manage group membership and determine the set of users who belong to each group defined
       within DACS.

       A group's membership is determined solely by the administrator of the jurisdiction that
       defines it, unless membership is delegated to other jurisdictions.

       For its own purposes, a jurisdiction often maintains group membership information, such as
       the organizational unit within the jurisdiction to which each of its users belong.  DACS
       can consult such a group membership database to associate roles (or "internal-group
       membership") with the jurisdiction's users. This separately maintained information may
       easily be imported into DACS, eliminating the administrative burden that would arise from
       having to maintain the same information within two different systems.

       When DACS needs to resolve group membership to determine whether the user making a service
       request is a member of a particular group, it may need to consult any combination of local
       group definitions, the roles associated with the user, and remote group definitions
       (groups defined by other jurisdictions).

       DACS does not dictate any particular method of storing group information; group
       information is accessed through the DACS virtual filestore.

       Every referenced group must be defined somewhere within DACS, whether locally or by
       another jurisdiction, before the referencing group is considered valid by DACS.

   Role-Based Group Membership
       Jurisdictions (such as companies or organizations) typically have a hierarchical internal
       structure, perhaps based on subdivisions such as departments, groups, projects, and so on,
       and typically associate an individual with one or more of these subdivisions.
       Alternatively, they might use a organizational structure that is based on the role of each
       individual. Regardless of the type of structure, jurisdictions may have information
       services that describe and manage where an individual belongs within that structure. A
       directory system, such as X.500 or Microsoft's Active Directory, which is typically
       accessible using the Lightweight Directory Access Protocol (LDAP), is a common example of
       such an information service. Another example is Unix-type systems, which assign their
       users to groups for access control purposes. By exporting this information, a jurisdiction
       can use DACS to provide role-based security.

       DACS uses the concept of a role-based group to allow a jurisdiction to implicitly create
       groups and associate users with them. At authentication time, a jurisdiction can indicate
       which roles a user belongs to within the jurisdiction. This information becomes part of
       the user's credentials and is consulted when determining whether the user is a member of a
       given group. The entire membership of a role-based group, potentially very large and
       possibly sensitive, need never be revealed or distributed to other jurisdictions.

       Group information may sometimes be extracted from a directory system by processing the
       distinguished names of users. Consider the distinguished name:

           {cou=CA, prov=BC, o=BigBank, ou=RandD, ou=Software, ou=Networks, cn=Auggie Doggie}

       For this individual, a role descriptor asserting membership in three groups within the
       jurisdiction might be produced: 1) RandD, 2) Software within RandD, and 3) Networks within
       Software under RandD. Within DACS access control rules, these groups might be referred to
       as "%BigBank:RandD", "%BigBank:RandD-Software", and "%BigBank:RandD-Software-Networks".
       These group names may also be included in the membership of other groups. Also, a group
       having one of these names can be defined and administered using DACS's standard group
       membership methods; its membership is the union of the role-based group members and the
       explicitly named group members.

       A concise syntax is available for expressing hierarchically-related elements of a role
       descriptor. The role descriptor "RandD/Software/Networks" is an equivalent way of
       expressing the three-element descriptor given above.

       It is relatively easy for a jurisdiction to use its existing services to export the
       required role description to DACS. The Roles clause (see dacs.conf(5)[1]) configures how
       this is done.

   Group Syntax and Semantics
       The following BNF syntax describes the names and symbols used in group definitions. Upper
       and lower case are distinct in the defined strings and all strings are constructed from a
       subset of the printable ASCII characters (e.g., the group name DSS:abc is different from
       the group name DSS:AbC).

           <Jurisdiction-Name>       ::= [A-Za-z][A-Za-z0-9\-_]*
           <Jurisdiction-Group-Name> ::= [A-Za-z][A-Za-z0-9\-_]*

       Thus, jurisdiction names and group names are composed of upper and lower case letters,
       digits, dashes, and underscores and must begin with a letter.

       The name of a group is formed from two components:

           <Group-Name> ::= <Jurisdiction-Name> ':' <Jurisdiction-Group-Name>

       The <Jurisdiction-Name> is the unique, officially-assigned abbreviated name for the DACS
       jurisdiction. The <Jurisdiction-Group-Name> is a unique name for the group within the
       jurisdiction that defines the <Group-Name>.

       The following XML DTD is used as the external representation of group definitions and
       membership. It is used by DACS both to distribute this information from one jurisdiction
       to another.

           <!ELEMENT groups (group_definition)* >

           <!ELEMENT group_definition (group_member*) >
           <!ATTLIST group_definition
               jurisdiction    CDATA #REQUIRED
               name            CDATA #REQUIRED
               mod_date        CDATA #REQUIRED
               type            (public | private) #REQUIRED

           <!ELEMENT group_member EMPTY >
           <!ATTLIST group_member
               jurisdiction    CDATA #REQUIRED
               name            CDATA #REQUIRED
               alt_name        CDATA #IMPLIED
               type            (role | dacs | username | meta) #REQUIRED
               dacs_url        CDATA #IMPLIED
               authenticates   (yes | no) #IMPLIED
               prompts         (yes | no) #IMPLIED
               auxiliary       CDATA #IMPLIED

       A group_definition gives the official name of the jurisdiction that defined the group
       (jurisdiction), a name for the group that is unique with that jurisdiction (name), the
       date and time the group's definition was last changed (mod_date) and whether the group's
       membership is to be kept private (type). The date and time are expressed in UTC and using
       a 24 hour clock, in the format Wdy, DD-Mon-YYYY HH:MM:SS GMT, based on RFC 822[2], with
       the variations that the only legal time zone is GMT and the separators between the
       elements of the date must be dashes. If public, the type attribute indicates that the
       group membership may be distributed to other jurisdictions and included in the definition
       of another group that is distributed.

       Each group_member specifies a member of the group. The type is role if the named member is
       a role, username if it is a DACS username, and dacs if it is the name of another DACS
       group. The special type meta is reserved for the internal use of DACS and associated with
       this type only is the presence of information about the jurisdiction: dacs_url, name,
       altname, authenticates, and prompts, each of which must be present for this type, and
       auxiliary, which is optional. Refer to DACS Metadata[3] for additional information.

           In conjunction with dacs_list_jurisdictions(8)[4], if the dacs_url attribute value
           does not begin with "http" or "https", then name interpolation is performed on the
           value as if by the pathname()[5] function with hostname formed by prepending the name
           attribute value to the FEDERATION_DOMAIN[6] and port obtained from the port associated
           with the dacs_list_jurisdictions request.

           For example, assuming FEDERATION_DOMAIN is and given the entry:

               <group_member jurisdiction="METALOGIC" name="Metalogic"
                 type="meta" alt_name="Metalogic Software Corp."
                 dacs_url="%2+/metalogic/dacs" authenticates="yes"
                prompts="no" auxiliary="local" />

           and the request:


           then the effective value of dacs_url for the entry would be:


           And assuming FEDERATION_DOMAIN is and given the entry:

               <group_member jurisdiction="DACS" name="DSS Inc." type="meta"
                alt_name="DSS Inc." dacs_url="%0:%p/cgi-bin/dacs" authenticates="yes"
                prompts="no" auxiliary="local" />

           and the request:


           then the effective value of dacs_url would be:


       If the type is role, any user who has credentials that name the given role is a member of
       the group.

       The appearance of a group name in the membership list of a group definition effectively
       inserts the entire membership of that referenced group in the definition. This type of
       inclusion is recursive, allowing for a configurable maximum depth. A cycle of inclusions
       is detected and not considered an error. Duplicate members are culled from the final
       membership list. All invalid group definitions are considered by DACS to have no members
       (that is, they are treated as having an empty membership list). The included group may
       belong to the same jurisdiction as the one being defined or it may refer to a group
       defined by some other jurisdiction. In the latter case, the administrator who defines the
       group delegates part of the responsibility for the group definition to another
       administrator who might do the same.

       A group may be defined to be empty (i.e., not having any members).

   DACS Metadata
       At each jurisdiction in a federation, DACS requires metadata that describes the
       jurisdictions. This information might be used by middleware or client-side software, for
       instance, for creating a menu to present to the user, which would need to obtain a list of
       jurisdictions. The metadata is also used for various internal purposes.

           The DACS metadata is stored in a group definition named "jurisdictions" relative to
           the groups item type. By default, at a jurisdiction with JURISDICTION_NAME[7] BOBO in
           a federation with FEDERATION_DOMAIN[6], this will be a file named
           jurisdictions.grp in the directory /usr/local/dacs/federations/

           DACS does not care about the values of the name and alt_name attributes, provided that
           they are well-formed. The alt_name might provide descriptive information in another
           language. These attributes might be used by middleware to construct a menu for users
           to select their home jurisdiction when logging in, for instance. For consistency, a
           federation should consider adopting a convention across all jurisdictions for how
           these two attributes are used.

           The dacs_url attribute is important because it tells DACS how to construct a URL for
           any DACS web service at the jurisdiction.

       Group information about jurisdictions is indicated by the meta attribute value for the
       type attribute.

       This example group definition describes a four jurisdiction DACS federation:

               jurisdiction="DACS" name="jurisdictions" mod_date="Tue, 11-Sep-2001 3:00:00 GMT" type="public">

             <group_member jurisdiction="METALOGIC"
               name="Full name of this jurisdiction, in English"
               alt_name="Full name of this jurisdiction, in French"
               prompts="no" />

             <group_member jurisdiction="BC"
               name="Full name of this jurisdiction, in English"
               alt_name="Full name of this jurisdiction, in French"
               prompts="no" />

             <group_member jurisdiction="ON"
               name="Full name of this jurisdiction, in English"
               alt_name="Full name of this jurisdiction, in French"
               prompts="no" />

             <group_member jurisdiction="NF"
               name="Full name of this jurisdiction, in English"
               alt_name="Full name of this jurisdiction, in French"
               prompts="yes" />



       The group ON:gis is defined by the jurisdiction ON to consist of three ordinary users:

               jurisdiction="ON" name="gis" mod_date="Fri, 30-Nov-2001 13:17:00 GMT" type="public">
               <group_member jurisdiction="NF" name="" type="username"/>
               <group_member jurisdiction="ON" name="" type="username"/>
               <group_member jurisdiction="METALOGIC" name="" type="username"/>

       This example defines a group that includes other groups as members:

               jurisdiction="METALOGIC" name="admin" mod_date="Fri, 30-Nov-2001 9:17:00 GMT" type="public">
               <group_member jurisdiction="NF" name="admin" type="dacs"/>
               <group_member jurisdiction="ON" name="admin" type="dacs"/>
               <group_member jurisdiction="BC" name="admin" type="dacs"/>
               <group_member jurisdiction="NF" name="" type="username"/>

       The group METALOGIC:admin is defined by jurisdiction METALOGIC to consist of the
       membership of three other groups (NF:admin, ON:admin, and BC:admin) and a user.

       This group, BC:nobody, has no members:

               jurisdiction="BC" name="nobody" mod_date="Fri, 30-Nov-2001 10:17:00 GMT" type="public"/>

       Here is an example of a private group:

               jurisdiction="BC" name="pilot_admin" mod_date="Fri, 28-Dec-2001 23:59:00 GMT" type="private">
               <group_member jurisdiction="BC" name="" type="username"/>

       As the first group in the example above has been declared to be private, access control
       rules may be constructed to make its membership invisible to other jurisdictions, to
       forbid its definition from being forwarded to other jurisdictions, and so on.

       Here is a group with dynamic, role-based membership:

               jurisdiction="BC" name="admin" mod_date="Wed, 22-Aug-2001 17:51:00 GMT" type="public">
               <group_member jurisdiction="BC" name="ou_admin" type="role"/>
               <group_member jurisdiction="METALOGIC" name="" type="username"/>
               <group_member jurisdiction="BC" name="admin" type="dacs"/>

       This definition references a role (ou_admin), a username, and a group.


       Distributed Systems Software ([8])


       Copyright2003-2012 Distributed Systems Software. See the LICENSE[9] file that accompanies
       the distribution for licensing information.


        1. dacs.conf(5)

        2. RFC 822

        3. DACS Metadata

        4. dacs_list_jurisdictions(8)

        5. pathname()




        9. LICENSE