DACS.GROUPS(5)                 DACS Formats Manual                DACS.GROUPS(5)

       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

       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

       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. Typically, an individual is
       associated with one or more of these subdivisions. Alternatively,
       jurisdictions might use an 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)[1], is a common example of such an information
       service. Another example is found in Unix-type systems, which assign
       their users to groups[2] for access control purposes. By exporting this
       information, or by creating and managing its own group definitions, 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 a distinguished
       name like the following, which might be retrieved from a directory

           {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", respectively. 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)[3]) 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

           <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

       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[4], 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[5]
       for additional information.

           In conjunction with dacs_list_jurisdictions(8)[6], 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()[7]
           function with hostname formed by prepending the name attribute value
           to the FEDERATION_DOMAIN[8] and port obtained from the port
           associated with the dacs_list_jurisdictions request.

           For example, assuming FEDERATION_DOMAIN is test-03.example.com 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 dss.ca 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[9] BOBO in a federation with
           FEDERATION_DOMAIN[8] example.com, this will be a file named
           jurisdictions.grp in the directory

           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

               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="alice@nf.example.org" type="username"/>
               <group_member jurisdiction="ON" name="bob@on.example.org" type="username"/>
               <group_member jurisdiction="METALOGIC" name="carol@example.org" 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="alice@gov.nf.example.org" 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="brain@bc.example.com" 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="bobo@example.com" 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 (www.dss.ca[10])

       Copyright © 2003-2018 Distributed Systems Software. See the LICENSE[11]
       file that accompanies the distribution for licensing information.

        1. Lightweight Directory Access Protocol (LDAP)

        2. groups

        3. dacs.conf(5)

        4. RFC 822

        5. DACS Metadata

        6. dacs_list_jurisdictions(8)

        7. pathname()



       10. www.dss.ca

       11. LICENSE

DACS 1.4.40                        02/19/2019                     DACS.GROUPS(5)