Provided by: dacs_1.4.28b-3ubuntu2_i386 bug


       dacs_autologin_ssl - use an SSL client certificate to automatically
       obtain DACS credentials


       dacs_autologin_ssl [dacsoptions[1]]


       This program is part of the DACS suite.

       The dacs_autologin_ssl CGI program, in conjunction with appropriate
       DACS configuration and a valid SSL client certificate, can be used for
       user-transparent DACS authentication. A user is not prompted for a
       username or password, and no user-visible sign-on procedure takes

       At present, the program merely acts as glue to indirectly invoke
       dacs_authenticate(8)[2]. Any valid X.509 certificate can be used for
       this purpose, including a self-signed certificate. Please refer to the
       OpenSSL[3] documentation for additional information about certificates.

       This program can be used to automatically and transparently
       authenticate a user that has been issued an SSL client certificate.
       When an unauthenticated user is denied access to a DACS-wrapped
       resource, she can be automatically authenticated and redirected back to
       the resource without any user input or action. This assumes that the
       client certificate is sent automatically by the browser and that no
       additional user prompting is needed by the authenticating jurisdiction.
       For redirection to the original resource to work properly. the original
       request must have used the GET method.

           The cert style of authentication must be configured when
           dacs_autologin_ssl is being used as described. See


       Only the standard dacsoptions[1] command line arguments are recognized.

   Web Service Arguments
       dasc_autologin_ssl understands the following CGI arguments.

           When dacs_autologin_ssl is invoked as a result of DACS event
           handling, DACS_ERROR_URL is automatically passed to it by
           dacs_acs(8)[5] and represents the original URL to which access was
           denied. In typical use, dacs_autologin_ssl is configured as the
           handler for a dacs_acs 902 error code (NO_AUTH, "Authentication by
           DACS is required").  dacs_autologin_ssl then invokes
           dacs_authenticate. If DACS authentication is successful,
           dacs_authenticate ordinarily issues a browser redirect to the value
           of DACS_ERROR_URL and a cookie bearing the credentials are set in
           the browser (but see the NOREDIRECT argument). This argument is
           optional; if not provided, the jurisdiction's configured
           post-authentication action will occur.

           If this optional argument is present (its value is immaterial),
           dacs_autologin_ssl instructs dacs_authenticate to not issue a
           browser redirect to the value of DACS_ERROR_URL.

           If this optional argument is present, it gives the name of the
           jurisdiction at which authentication should take place. By default,
           dacs_authenticate is invoked at the same jurisdiction as

           This optional argument explicitly names the attribute in the
           certificate from which to set USERNAME. The default value is
           SSL_CLIENT_S_DN_CN. It is an error if the specified attribute name
           does not exist. Giving the value of CERT_NAME_ATTR as the empty
           string results in the empty string being passed as the value of


       A typical use of dacs_autologin_ssl is to transparently authenticate a
       user via his SSL client certificate.

       In the DACS configuration file, dacs.conf, jurisdiction EXAMPLE is
       configured as follows (this excerpt from a configuration file uses
       fictitious domain names):

           <Jurisdiction uri="">



           <!-- Authenticate using an SSL certificate. -->
           <Auth id="cert">
           URL ""
           STYLE "cert"
           CONTROL "sufficient"
           CERT_CA_PATH "/usr/local/apache2.2/conf/ssl.crt"


       Assume the following access control rule applies to the request:

           <acl_rule status="enabled">
               <service url_pattern='/foo.html'/>

             <rule order="allow,deny">

       The preceding configuration results in the following behaviour. An
       unauthenticated user accessing foo.html (
       is denied access because the rule governing that web page tests for
       authentication and no credentials are sent with the request. As a
       result, the ACS_ERROR_HANDLER[6] directive causes the user to be
       redirected to dacs_autologin_ssl, which redirects the user to
       dacs_authenticate, passing arguments as necessary.

       dacs_authenticate then invokes local_cert_authenticate[4], passing it
       the client's certificate. The certificate is validated and a username
       is extracted from it and mapped to a valid DACS username.

       If authentication succeeds, DACS credentials for the jurisdiction
       EXAMPLE are generated. These credentials are returned to the browser
       within a cookie and the browser is redirected to the value of
       DACS_ERROR_URL (recall that DACS_ERROR_URL was passed to
       dacs_autologin_ssl by dacs_acs when the 902 handler was invoked and was
       forwarded to dacs_authenticate). In this example the user is redirected
       to Given the rule above, this time the
       user's request for foo.html will be granted.

       dacs_autologin_ssl may also be used as the target of an explicit
       authentication link. For example:

           <a href="\

       Following the link should result in the user being authenticated and
       redirected to the specified URL.


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


       dacs_authenticate(8)[2], dacs_acs(8)[5], dacs.conf(5)[7],


       Distributed Systems Software ([9])


       Copyright2003-2012 Distributed Systems Software. See the LICENSE[10]
       file that accompanies the distribution for licensing information.


        1. dacsoptions

        2. dacs_authenticate(8)

        3. OpenSSL

        4. dacs_authenticate(8)

        5. dacs_acs(8)


        7. dacs.conf(5)

        8. autologin(8)


       10. LICENSE