slapo-dds(5)
NAME
slapo-dds - Dynamic Directory Services overlay to slapd
SYNOPSIS
/etc/ldap/slapd.conf
DESCRIPTION
The dds overlay to slapd(8) implements dynamic objects as per RFC 2589. The name dds stands for Dynamic Directory Services. It allows to define dynamic objects, characterized by the dynamicObject objectClass. Dynamic objects have a limited lifetime, determined by a time-to-live (TTL) that can be refreshed by means of a specific refresh extended operation. This operation allows to set the Client Refresh Period (CRP), namely the period between refreshes that is required to preserve the dynamic object from expiration. The expiration time is computed by adding the requested TTL to the current time. When dynamic objects reach the end of their lifetime without being further refreshed, they are automatically deleted. There is no guarantee of immediate deletion, so clients should not count on it. Dynamic objects can have subordinates, provided these also are dynamic objects. RFC 2589 does not specify what the behavior of a dynamic directory service should be when a dynamic object with (dynamic) subordinates expires. In this implementation, the lifetime of dynamic objects with subordinates is prolonged until all the dynamic subordinates expire. This slapd.conf(5) directive adds the dds overlay to the current database: overlay dds The database must have a rootdn specified, otherwise, the dds overlay will not be able to delete expired objects. The dds overlay may be used with any backend that implements the add, modify, search, and delete operations. Since its use may result in many internal entry lookups, adds and deletes, it should be best used in conjunction with backends that have reasonably good write performances. The config directives that are specific to the dds overlay are prefixed by dds-, to avoid potential conflicts with directives specific to the underlying database or to other stacked overlays. dds-max-ttl <ttl> Specifies the max TTL value. This is also the default TTL newly created dynamic objects receive, unless dds-default-ttl is set. When the client with a refresh extended operation requests a TTL higher than it, sizeLimitExceeded is returned. This value must be between 86400 (1 day, the default) and 31557600 (1 year plus 6 hours, as per RFC 2589). dds-min-ttl <ttl> Specifies the min TTL value; clients requesting a lower TTL by means of the refresh extended operation actually obtain this value as CRP. If set to 0 (the default), no lower limit is set. dds-default-ttl <ttl> Specifies the default TTL value that newly created dynamic objects get. If set to 0 (the default), the dds-max-ttl is used. dds-interval <ttl> Specifies the interval between expiration checks; defaults to 1 hour. dds-tolerance <ttl> Specifies an extra time that is added to the timer that actually wakes up the thread that will delete an expired dynamic object. So the nominal lifetime of the entry is that specified in the entryTtl attribute, but its lifetime will actually be entryTtl + tolerance. Note that there is no guarantee that the lifetime of a dynamic object will be exactly the requested TTL; due to implementation details, it may be longer, which is allowed by RFC 2589. By default, tolerance is 0. dds-max-dynamicObjects <num> Specifies the maximum number of dynamic objects that can simultaneously exist within a naming context. This allows to limit the amount of resources (mostly in terms of run-queue size) that are used by dynamic objects. By default, no limit is set. dds-state {TRUE|false} Specifies if the Dynamic Directory Services feature is enabled or not. By default it is; however, a proxy does not need to keep track of dynamic objects itself, it only needs to inform the frontend that support for dynamic objects is available.
ACCESS CONTROL
The dds overlay restricts the refresh operation by requiring manage access to the entryTtl attribute (see slapd.access(5) for details about the manage access privilege). Since the entryTtl is an operational, NO-USER-MODIFICATION attribute, no direct write access to it is possible. So the dds overlay turns refresh extended operation into an internal modification to the value of the entryTtl attribute with the relax control set. RFC 2589 recommends that anonymous clients should not be allowed to refresh a dynamic object. This can be implemented by appropriately crafting access control to obtain the desired effect. Example: restrict refresh to authenticated clients access to attrs=entryTtl by users manage by * read Example: restrict refresh to the creator of the dynamic object access to attrs=entryTtl by dnattr=creatorsName manage by * read Another suggested usage of dynamic objects is to implement dynamic meetings; in this case, all the participants to the meeting are allowed to refresh the meeting object, but only the creator can delete it (otherwise it will be deleted when the TTL expires) Example: assuming participant is a valid DN-valued attribute, allow users to start a meeting and to join it; restrict refresh to the participants; restrict delete to the creator access to dn.base="cn=Meetings" attrs=children by users write access to dn.onelevel="cn=Meetings" attrs=entry by dnattr=creatorsName write by * read access to dn.onelevel="cn=Meetings" attrs=participant by dnattr=creatorsName write by users selfwrite by * read access to dn.onelevel="cn=Meetings" attrs=entryTtl by dnattr=participant manage by * read
REPLICATION
This implementation of RFC 2589 provides a restricted interpretation of
how dynamic objects replicate. Only the master takes care of handling
dynamic object expiration, while replicas simply see the dynamic object
as a plain object.
When replicating these objects, one needs to explicitly exclude the
dynamicObject class and the entryTtl attribute. This implementation of
RFC 2589 introduces a new operational attribute, entryExpireTimestamp,
that contains the expiration timestamp. This must be excluded from
replication as well.
The quick and dirty solution is to set schemacheck=off in the syncrepl
configuration and, optionally, exclude the operational attributes from
replication, using
syncrepl ...
exattrs=entryTtl,entryExpireTimestamp
In any case the overlay must be either statically built in or run-time
loaded by the consumer, so that it is aware of the entryExpireTimestamp
operational attribute; however, it must not be configured in the shadow
database. Currently, there is no means to remove the dynamicObject
class from the entry; this may be seen as a feature, since it allows to
see the dynamic properties of the object.
FILES
/etc/ldap/slapd.conf
default slapd configuration file
SEE ALSO
slapd.conf(5), slapd-config(5), slapd(8).
AUTHOR
Implemented by Pierangelo Masarati.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
