Apache Module mod_auth_form 5o472x

Basic Configuration 5i1h4i

To protect a particular URL with mod_authn_file. If authentication is unsuccessful, the will be redirected to the form page.

<Location "/">
    AuthFormProvider file
    AuthFile "conf/wd"
    AuthType form
    AuthName "/"
    AuthFormRequiredLocation "http://example.com/.html"

    Session On
    SessionCookieName session path=/

    Require valid-
</Location>

The directive AuthFile specify that names and s should be checked against the chosen file.

The directives mod_session.

You can optionally add a mod_session_crypto be loaded.

In the simple example above, a URL has been protected by mod_auth_form, but the has yet to be given an opportunity to enter their name and . Options for doing so include providing a dedicated standalone page for this purpose, or for providing the page inline.

Standalone 1p3w6w

The form can be hosted as a standalone page, or can be provided inline on the same page.

When configuring the as a standalone page, unsuccessful authentication attempts should be redirected to a form created by the website for this purpose, using the AuthFormRequiredLocation directive. Typically this page will contain an HTML form, asking the to provide their usename and .

<form method="POST" action="/do.html">
  name: <input type="text" name="httpd_name" value="" />
  : <input type="" name="httpd_" value="" />
  <input type="submit" name="" value="" />
</form>

The part that does the actual is handled by the form--handler. The action of the form should point at this handler, which is configured within Apache httpd as follows:

<Location "/do.html">
    SetHandler form--handler
    AuthFormRequiredLocation "http://example.com/.html"
    AuthFormSuccessLocation "http://example.com//index.html"
    AuthFormProvider file
    AuthFile "conf/wd"
    AuthType form
    AuthName /
    Session On
    SessionCookieName session path=/
</Location>

The URLs specified by the AuthFormSuccessLocation directive specifies the URL the should be redirected to upon successful .

Alternatively, the URL to redirect the to on success can be embedded within the form, as in the example below. As a result, the same form--handler can be reused for different areas of a website.

<form method="POST" action="/do.html">
  name: <input type="text" name="httpd_name" value="" />
  : <input type="" name="httpd_" value="" />
  <input type="submit" name="" value="" />
  <input type="hidden" name="httpd_location" value="http://example.com/success.html" />
</form>

Inline 275r5j

As an alternative to having a dedicated page for a website, it is possible to configure mod_auth_form to authenticate s inline, without being redirected to another page. This allows the state of the current page to be preserved during the attempt. This can be useful in a situation where a time limited session is in force, and the session times out in the middle of the request. The can be re-authenticated in place, and they can continue where they left off.

If a non-authenticated attempts to access a page protected by AuthFormRequiredLocation directive, a HTTP_UNAUTHORIZED status code is returned to the browser indicating to the that they are not authorized to view the page.

To configure inline authentication, the overrides the error document returned by the HTTP_UNAUTHORIZED status code with a custom error document containing the form, as follows:

AuthFormProvider file
ErrorDocument 401 "/.shtml"
AuthFile "conf/wd"
AuthType form
AuthName realm
AuthFormRequiredLocation "http://example.com/.html"
Session On
SessionCookieName session path=/

The error document page should contain a form with an empty action property, as per the example below. This has the effect of submitting the form to the original protected URL, without the page having to know what that URL is.

<form method="POST" action="">
  name: <input type="text" name="httpd_name" value="" />
  : <input type="" name="httpd_" value="" />
  <input type="submit" name="" value="" />
</form>

When the end has filled in their details, the form will make an HTTP POST request to the original protected URL. mod_auth_form will intercept this POST request, and if HTML fields are found present for the name and , the will be logged in, and the original protected URL will be returned to the as a GET request.

Inline with Body Preservation 214w1b

A limitation of the inline technique described above is that should an HTML form POST have resulted in the request to authenticate or reauthenticate, the contents of the original form posted by the browser will be lost. Depending on the function of the website, this could present significant inconvenience for the end .

mod_auth_form addresses this by allowing the method and body of the original request to be embedded in the form. If authentication is successful, the original method and body will be retried by Apache httpd, preserving the state of the original request.

To enable body preservation, add three additional fields to the form as per the example below.

<form method="POST" action="">
  name: <input type="text" name="httpd_name" value="" />
  : <input type="" name="httpd_" value="" />
  <input type="submit" name="" value="" />
  
  <input type="hidden" name="httpd_method" value="POST" />
  <input type="hidden" name="httpd_mimetype" value="application/x-www-form-urlencoded" />
  <input type="hidden" name="httpd_body" value="name1=value1&name2=value2" />

</form>

How the method, mimetype and body of the original request are embedded within the form will depend on the platform and technology being used within the website.

One option is to use the KeptBodySize directive, along with a suitable CGI script to embed the variables in the form.

Another option is to render the form using a CGI script or other dynamic technology.

AuthFormProvider file
ErrorDocument 401 "/cgi-bin/.cgi"
...

Logging Out 2o5f31

To enable a to log out of a particular session, configure a page to be handled by the form--handler. Any attempt to access this URL will cause the name and to be removed from the current session, effectively logging the out.

By setting the AuthFormLocation directive, a URL can be specified that the browser will be redirected to on successful . This URL might explain to the that they have been logged out, and give the the option to again.

SetHandler form--handler
AuthName realm
AuthFormLocation "http://example.com/loggedout.html"
Session On
SessionCookieName session path=/

Note that logging a out does not delete the session; it merely removes the name and from the session. If this results in an empty session, the net effect will be the removal of that session, but this is not guaranteed. If you want to guarantee the removal of a session, set the SessionMaxAge directive to a small value, like 1 (setting the directive to zero would mean no session age limit).

SetHandler form--handler
AuthFormLocation "http://example.com/loggedout.html"
Session On
SessionMaxAge 1
SessionCookieName session path=/

names and s w3f3y

Note that form submission involves URLEncoding the form data: in this case the name and . You should therefore pick names and s that avoid characters that are URLencoded in form submission, or you may get unexpected results.