Provided by: dacs_1.4.28b-3ubuntu2_amd64 bug


       dacs_autologin_ssl - use an SSL client certificate to automatically obtain DACS


       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 place.

       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

       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 dacs_authenticate(8)[4].


       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

           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 dacs_autologin_ssl.

           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 USERNAME.


       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

       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

           <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], autologin(8)[8]


       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