NAME¶

dacs_select_credentials - temporarily disable DACS credentials

SYNOPSIS¶

dacs_select_credentials [ dacsoptions[1]]

DESCRIPTION¶

This program is part of the DACS suite.

A user may concurrently possess more than one set of DACS credentials during a session, with each representing a different identity. Zero or more credentials may be submitted with a request for a DACS-wrapped web service. It is sometimes desirable or necessary for a user to switch between identities, or to be considered unauthenticated. Middleware (software situated between a user agent and a DACS-capable web server) and more sophisticated user agents might provide this functionality simply by sending some DACS HTTP cookies and not sending others, under user control. With standard browsers or in other situations where this functionality is not available, achieving this by repeatedly authenticating and signing off (or by manually deleting cookies) would be inconvenient at best.

The dacs_select_credentials web service can be used to temporarily disable credentials, leaving the remaining credentials selected for access control purposes. The user agent continues to send all DACS HTTP cookies as usual, but dacs_acs(8)[2] will ignore disabled identities before deciding to grant or deny access. This feature can be used to work around the maximum number of identities that DACS allows to be associated with a request - determined by the ACS_CREDENTIALS_LIMIT[3] directive - or for administrative, testing, or other reasons. There are similarities between dacs_select_credentials and su(1)[4].

A selected identity is handled normally, but a disabled identity is "hidden"; it is not considered for access control purposes and is not reported by dacs_current_credentials(8)[5]. A disabled identity may be re-enabled by dacs_select_credentials, however, and dacs_signout(8)[6] will work with disabled identities. All identities are considered for the purposes of revoking access, however, and in other situations described below.

The selected credentials are identified by a cryptographically protected cookie that is issued by dacs_select_credentials. The HTTP cookie name has the following format:

DACS: Federation-Name:::SELECTED

where Federation-Name is the official name assigned to the federation for which the cookie is valid. This cookie confers no identity or access control rights to its possessor. If this cookie is deleted, or just not sent with a request, all credentials accompanying the request are used for access control. If dacs_signout(8)[6] asks the browser to delete all credentials (i.e., no more credentials exist that dacs_signout is aware of), it will also ask the browser to delete the selected credentials cookie.

The FORMAT argument (see dacs(1)[7]) determines the type of output, with the default being HTML, using the style sheet dacs_select_credentials.css[8]. If XML output is selected, a document conforming to dacs_select_credentials.dtd[9] is returned.

OPTIONS¶

Web Service Arguments¶

dacs_select_credentials accepts the following arguments in addition to the standard CGI arguments[10].

OPERATION

This parameter is required and must be one of (case-insensitively):

SELECT

This operation replaces the current set of selected credentials, if any, with the set that match the DACS_USERNAME and DACS_JURISDICTION arguments. It is an error if no credentials match the arguments.

DESELECT

This operation disables the specified enabled credentials. If no credentials remain selected, the user is effectively unauthenticated as if by the SELECT_UNAUTH operation. Non-matching arguments are ignored.

ADD

The ADD operation adds the specified disabled credentials to the set of enabled credentials.

LIST

This operation lists the selection status.

CLEAR

This operation results in no selection, with all credentials available again.

SELECT_UNAUTH

This operation makes the user effectively unauthenticated; all credentials are disabled.

DESELECT_UNAUTH

This operation reverses SELECT_UNAUTH, resulting in there being no selection and all credentials are again available. It is an error if the user is not effectively unauthenticated when the operation is invoked.

DACS_USERNAME

This argument specifies a username to match against existing credentials for the SELECT, DESELECT, and ADD operations. Exact string matching is used. If this argument is absent, all usernames will be selected.

DACS_JURISDICTION

This argument specifies a jurisdiction name to match against existing credentials for the SELECT, DESELECT, and ADD operations. Exact string matching is used. If this argument is absent, all jurisdictions will be selected.

COOKIE_SYNTAX

This parameter has the same semantics as with the dacs_authenticate(8)[11] service.

Tip

The dacs_authenticate(8)[12] web service takes an optional argument, OPERATION, that can have the value SELECT. If authentication succeeds and this argument is present, the resulting credentials are selected as described above.