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 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

       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

           {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

       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 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[7]BOBO in a federation with
           FEDERATION_DOMAIN[6]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[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()



        8. www.dss.ca

        9. LICENSE

DACS 1.4.28b                      02/04/2014                    DACS.GROUPS(5)