dacs_signout — DACS signout service


dacs_signout [dacsoptions]


This web service is part of the DACS suite.

The dacs_signout web service is invoked from a web browser to cause one or more sets of DACS credentials for the current federation, stored as HTTP cookies, to be removed from the browser. This is done by replacing one or more existing cookies with cookies that have expired. The effect is that the user agent signs out (logs off) identities previously obtained through dacs_authenticate(8) or any other DACS authentication method. A DACS-enabled portal will typically provide users with a link or web page form to invoke this service.

By default, all credentials are removed, but credentials can be selected for deletion based on a particular username (who the user was authenticated as) or a particular jurisdiction (the jurisdiction that performed that authentication).

Should copies of the selected credentials exist outside of the browser, they may still be valid; only the browser's copies are destroyed.

The SIGNOUT_HANDLER directive can optionally be used to specify where the user should be redirected before this service terminates, provided HTML output is being produced (i.e., the FORMAT does not select a variety of XML output or JSON output). If XML output is selected, a document conforming to dacs_current_credentials.dtd is returned. If JSON output is selected, a document conforming to dacs_current_credentials.rnc is returned.

Explicitly signing off using this web service is generally unnecessary because DACS credentials will either become invalid when their lifetime is reached (see AUTH_CREDENTIALS_DEFAULT_LIFETIME_SECS) or will be automatically deleted when the user's browser session terminates (or a session with a trusted servlet ends). A user can also sign off by deleting his browser's DACS cookies. Middleware can simply discard cookies.

As DACS credentials are relative to a particular federation of DACS servers, only those credentials that are associated with the federation of the DACS server that receives the service request will be affected by this service. This implies that a user who wants to explicitly sign out must do so for each federation in which he or she is currently authenticated.

Web Service Arguments

In addition to the standard CGI arguments, dacs_signout understands the following CGI arguments:


If present, all credentials associated with this username will be deleted. If not provided, the username in the credentials is immaterial.


If present, all credentials associated with this jurisdiction (given as its JURISDICTION_NAME) will be deleted. If not provided, the jurisdiction in the credentials is immaterial.


If permitted by the SIGNOUT_HANDLER directive and HTML output has been selected, redirect the user's browser to the URL specified by this parameter, which may contain a properly escaped query string. Whether the GET method is used depends on the context of the original request (and keep in mind that GET parameters may be visible and logged). This URL is not validated by DACS. When not explicitly permitted by the SIGNOUT_HANDLER directive, this parameter is ignored.


This optional parameter is as described for the dacs_authenticate(8) service.

The optional parameters are used to delete only those credentials that match a particular username or jurisdiction (or both). If neither parameter is specified in the service request, all DACS cookies associated with the federation that receives the service request will be deleted.

The name matching method can be configured through the NAME_COMPARE directive.


DACS does not currently provide an inactivity timeout feature, but it may appear in a future release. One way to add it would be to take advantage of the user tracking capability, which can record all of a user's requests for DACS-wrapped services within a federation. By simply comparing the current time with the time stamp of the user's last service request, the user's idle time can be determined. If the idle time exceeds a configured maximum, dacs_acs(8) would consider the user's credentials to be invalid (effectively expired) and take appropriate action. A straightforward implementation would be a relatively simple enhancement to DACS; its main drawback, for those that enable it, is the extra performance hit incurred from user tracking and having to compute idle time during access control processing - the significance of this cost will depend on your platforms, the configuration of your federation, and user activity patterns.


To signout from all identities in the EXAMPLE federation, a user would simply invoke a URL like:


To signout only from the identity EXAMPLE::FEDROOT:bobo, a URL like the following might be invoked:


To signout from only those identities in the EXAMPLE federation having a username component bobo, invoke a URL like:


This would signoff from EXAMPLE::FEDROOT:bobo and EXAMPLE::DSS:bobo, for instance.


The program exits 0 if everything was fine, 1 if an error occurred.


dacs_authenticate(8), dacs_current_credentials(8), dacs_auth_agent(8), dacs_auth_transfer(8), dacs_select_credentials(8), dacsauth(1), dacscred(1)

The DACS distribution includes an example of a "log off" web page: html/examples/signout.html.


It might be useful for the non-HTML formats to provide configured or requested signout handler URLs.


Distributed Systems Software (www.dss.ca)


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

DACS Version 1.4.51 20-Jun-2024 DACS_SIGNOUT(8)

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$Id: dacs_signout.8.xml 3016 2018-08-17 18:12:46Z brachman $