apache/docs/manual/mod/mod_authnz_fcgi.xml

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<modulesynopsis metafile="mod_authnz_fcgi.xml.meta">

<name>mod_authnz_fcgi</name>
<description>Allows a FastCGI authorizer application to handle Apache
httpd authentication and authorization</description>
<status>Extension</status>
<sourcefile>mod_authnz_fcgi.c</sourcefile>
<identifier>authnz_fcgi_module</identifier>
<compatibility>Available in version 2.4.10 and later</compatibility>

<summary>
    <p>This module allows FastCGI authorizer applications to
    authenticate users and authorize access to resources.  It supports
    generic FastCGI authorizers which participate in a single phase
    for authentication and authorization as well as Apache httpd-specific
    authenticators and authorizors which participate in one or both
    phases.</p>

    <p>FastCGI authorizers can authenticate using user id and password, 
    such as for Basic authentication, or can authenticate using arbitrary
    mechanisms.</p>
</summary>

<seealso><a href="../howto/auth.html">Authentication, Authorization,
and Access Control</a></seealso>
<seealso><module>mod_auth_basic</module></seealso>
<seealso><program>fcgistarter</program></seealso>
<seealso><module>mod_proxy_fcgi</module></seealso>

<section id="invocations"><title>Invocation modes</title>

    <p>The invocation modes for FastCGI authorizers supported by this 
    module are distinguished by two characteristics, <em>type</em> and
    auth <em>mechanism</em>.</p>

    <p><em>Type</em> is simply <code>authn</code> for authentication,
    <code>authz</code> for authorization, or <code>authnz</code> for
    combined authentication and authorization.</p>

    <p>Auth <em>mechanism</em> refers to the Apache httpd configuration
    mechanisms and processing phases, and can be <code>
    AuthBasicProvider</code>, <code>Require</code>, or <code>
    check_user_id</code>.  The first two of these
    correspond to the directives used to enable participation in the
    appropriate processing phase.</p>

    <p>Descriptions of each mode:</p>

    <dl>
      <dt><em>Type</em> <code>authn</code>, <em>mechanism</em>
      <code>AuthBasicProvider</code></dt>

      <dd>In this mode, 
      <code>FCGI_ROLE</code> is set to <code>AUTHORIZER</code> and
      <code>FCGI_APACHE_ROLE</code> is set to <code>AUTHENTICATOR</code>.
      The application must be defined as provider type <em>authn</em>
      using <directive module="mod_authnz_fcgi">
      AuthnzFcgiDefineProvider</directive> and enabled with
      <directive module="mod_auth_basic">AuthBasicProvider</directive>.
      When invoked, the application is
      expected to authenticate the client using the provided user id and
      password.  Example application:

<highlight language="perl">
#!/usr/bin/perl
use FCGI;
while (FCGI::accept >= 0) {
    die if $ENV{'FCGI_APACHE_ROLE'} ne "AUTHENTICATOR";
    die if $ENV{'FCGI_ROLE'}        ne "AUTHORIZER";
    die if !$ENV{'REMOTE_PASSWD'};
    die if !$ENV{'REMOTE_USER'};

    print STDERR "This text is written to the web server error log.\n";

    if ( ($ENV{'REMOTE_USER' } eq "foo" || $ENV{'REMOTE_USER'} eq "foo1") &amp;&amp;
        $ENV{'REMOTE_PASSWD'} eq "bar" ) {
        print "Status: 200\n";
        print "Variable-AUTHN_1: authn_01\n";
        print "Variable-AUTHN_2: authn_02\n";
        print "\n";
    }
    else {
        print "Status: 401\n\n";
    }
}
</highlight>

      Example configuration:
<highlight language="config">
AuthnzFcgiDefineProvider authn FooAuthn fcgi://localhost:10102/
&lt;Location /protected/&gt;
  AuthType Basic
  AuthName "Restricted"
  AuthBasicProvider FooAuthn
  Require ...
&lt;/Location&gt;
</highlight>
      </dd>

      <dt><em>Type</em> <code>authz</code>, <em>mechanism</em>
      <code>Require</code></dt>
      <dd>In this mode, <code>FCGI_ROLE</code> is set to <code>
      AUTHORIZER</code> and <code>FCGI_APACHE_ROLE</code> is set to
      <code>AUTHORIZER</code>.  The application must be defined as
      provider type <em>authz</em> using <directive module="mod_authnz_fcgi">
      AuthnzFcgiDefineProvider</directive>.  When invoked, the application 
      is expected to authorize the client using the provided user id and other
      request data.  Example application:
<highlight language="perl">
#!/usr/bin/perl
use FCGI;
while (FCGI::accept >= 0) {
    die if $ENV{'FCGI_APACHE_ROLE'} ne "AUTHORIZER";
    die if $ENV{'FCGI_ROLE'}        ne "AUTHORIZER";
    die if $ENV{'REMOTE_PASSWD'};

    print STDERR "This text is written to the web server error log.\n";

    if ($ENV{'REMOTE_USER'} eq "foo1") {
        print "Status: 200\n";
        print "Variable-AUTHZ_1: authz_01\n";
        print "Variable-AUTHZ_2: authz_02\n";
        print "\n";
    }
    else {
        print "Status: 403\n\n";
    }
}
</highlight>

      Example configuration:
<highlight language="config">
AuthnzFcgiDefineProvider authz FooAuthz fcgi://localhost:10103/
&lt;Location /protected/&gt;
  AuthType ...
  AuthName ...
  AuthBasicProvider ...
  Require FooAuthz
&lt;/Location&gt;
</highlight>
      </dd>

      <dt><em>Type</em> <code>authnz</code>, <em>mechanism</em>
      <code>AuthBasicProvider</code> <em>+</em> <code>Require</code></dt>

      <dd>In this mode, which supports the web server-agnostic FastCGI
      <code>AUTHORIZER</code> protocol, <code>FCGI_ROLE</code> is set to
      <code>AUTHORIZER</code> and <code>FCGI_APACHE_ROLE</code> is not set.
      The application must be defined as provider type <em>authnz</em>
      using <directive module="mod_authnz_fcgi">
      AuthnzFcgiDefineProvider</directive>.  The application is expected to
      handle both authentication and authorization in the same invocation
      using the user id, password, and other request data.  The invocation 
      occurs during the Apache httpd API authentication phase.  If the 
      application returns 200 and the same provider is invoked during the
      authorization phase (via <directive>Require</directive>), mod_authnz_fcgi
      will return success for the authorization phase without invoking the
      application.  Example application:
<highlight language="perl">
#!/usr/bin/perl
use FCGI;
while (FCGI::accept >= 0) {
    die if $ENV{'FCGI_APACHE_ROLE'};
    die if $ENV{'FCGI_ROLE'} ne "AUTHORIZER";
    die if !$ENV{'REMOTE_PASSWD'};
    die if !$ENV{'REMOTE_USER'};

    print STDERR "This text is written to the web server error log.\n";

    if ( ($ENV{'REMOTE_USER' } eq "foo" || $ENV{'REMOTE_USER'} eq "foo1") &amp;&amp;
        $ENV{'REMOTE_PASSWD'} eq "bar" &amp;&amp;
        $ENV{'REQUEST_URI'} =~ m%/bar/.*%) {
        print "Status: 200\n";
        print "Variable-AUTHNZ_1: authnz_01\n";
        print "Variable-AUTHNZ_2: authnz_02\n";
        print "\n";
    }
    else {
        print "Status: 401\n\n";
    }
}
</highlight>

      Example configuration:
<highlight language="config">
AuthnzFcgiDefineProvider authnz FooAuthnz fcgi://localhost:10103/
&lt;Location /protected/&gt;
  AuthType Basic
  AuthName "Restricted"
  AuthBasicProvider FooAuthnz
  Require FooAuthnz
&lt;/Location&gt;
</highlight>
      </dd>

      <dt><em>Type</em> <code>authn</code>, <em>mechanism</em>
      <code>check_user_id</code></dt>

      <dd>In this mode, <code>FCGI_ROLE</code> is set to <code>
      AUTHORIZER</code> and <code>FCGI_APACHE_ROLE</code> is set to
      <code>AUTHENTICATOR</code>.  The application must be defined as
      provider type <em>authn</em> using <directive module="mod_authnz_fcgi">
      AuthnzFcgiDefineProvider</directive>.  <directive 
      module="mod_authnz_fcgi">AuthnzFcgiCheckAuthnProvider</directive>
      specifies when it is called.  Example application:
<highlight language="perl">
#!/usr/bin/perl
use FCGI;
while (FCGI::accept >= 0) {
    die if $ENV{'FCGI_APACHE_ROLE'} ne "AUTHENTICATOR";
    die if $ENV{'FCGI_ROLE'} ne "AUTHORIZER";

    # This authorizer assumes that the RequireBasicAuth option of 
    # AuthnzFcgiCheckAuthnProvider is On:
    die if !$ENV{'REMOTE_PASSWD'};
    die if !$ENV{'REMOTE_USER'};

    print STDERR "This text is written to the web server error log.\n";

    if ( ($ENV{'REMOTE_USER' } eq "foo" || $ENV{'REMOTE_USER'} eq "foo1") &amp;&amp;
        $ENV{'REMOTE_PASSWD'} eq "bar" ) {
        print "Status: 200\n";
        print "Variable-AUTHNZ_1: authnz_01\n";
        print "Variable-AUTHNZ_2: authnz_02\n";
        print "\n";
    }
    else {
        print "Status: 401\n\n";
        # If a response body is written here, it will be returned to
        # the client.
    }
}
</highlight>

      Example configuration:
<highlight language="config">
AuthnzFcgiDefineProvider authn FooAuthn fcgi://localhost:10103/
&lt;Location /protected/&gt;
  AuthType ...
  AuthName ...
  AuthnzFcgiCheckAuthnProvider FooAuthn \
                               Authoritative On \
                               RequireBasicAuth Off \
                               UserExpr "%{reqenv:REMOTE_USER}"
  Require ...
&lt;/Location&gt;
</highlight>
      </dd>

    </dl>
    
</section>

<section id="examples"><title>Additional examples</title>

  <ol>
    <li>If your application supports the separate authentication and
    authorization roles (<code>AUTHENTICATOR</code> and <code>AUTHORIZER</code>), define 
    separate providers as follows, even if they map to the same
    application:

<highlight language="config">
AuthnzFcgiDefineProvider authn  FooAuthn  fcgi://localhost:10102/
AuthnzFcgiDefineProvider authz  FooAuthz  fcgi://localhost:10102/
</highlight>

    Specify the authn provider on 
    <directive module="mod_auth_basic">AuthBasicProvider</directive>
    and the authz provider on
    <directive module="mod_authz_core">Require</directive>:

<highlight language="config">
AuthType Basic
AuthName "Restricted"
AuthBasicProvider FooAuthn
Require FooAuthz
</highlight>
    </li>

    <li>If your application supports the generic <code>AUTHORIZER</code> role 
    (authentication and authorizer in one invocation), define a
    single provider as follows:

<highlight language="config">
AuthnzFcgiDefineProvider authnz FooAuthnz fcgi://localhost:10103/
</highlight>

    Specify the authnz provider on both <directive>AuthBasicProvider</directive>
    and <directive>Require</directive>:

<highlight language="config">
AuthType Basic
AuthName "Restricted"
AuthBasicProvider FooAuthnz
Require FooAuthnz
</highlight>
    </li>
</ol>
</section>

<section id="limitations"><title>Limitations</title>

    <p>The following are potential features which are not currently
    implemented:</p>

    <dl>
      <dt>Apache httpd access checker</dt>
      <dd>The Apache httpd API <em>access check</em> phase is a separate
      phase from authentication and authorization.  Some other FastCGI
      implementations implement this phase, which is denoted by the 
      setting of <code>FCGI_APACHE_ROLE</code> to <code>ACCESS_CHECKER</code>.</dd>

      <dt>Local (Unix) sockets or pipes</dt>
      <dd>Only TCP sockets are currently supported.</dd>

      <dt>Support for mod_authn_socache</dt>
      <dd>mod_authn_socache interaction should be implemented for
      applications which participate in Apache httpd-style
      authentication.</dd>

      <dt>Support for digest authentication using AuthDigestProvider</dt>
      <dd>This is expected to be a permanent limitation as there is
      no authorizer flow for retrieving a hash.</dd>

      <dt>Application process management</dt>
      <dd>This is expected to be permanently out of scope for
      this module.  Application processes must be controlled by
      other means.  For example, <program>fcgistarter</program> can be used to
      start them.</dd>

      <dt>AP_AUTH_INTERNAL_PER_URI</dt>
      <dd>All providers are currently registered as 
      AP_AUTH_INTERNAL_PER_CONF, which means that checks are not
      performed again for internal subrequests with the same
      access control configuration as the initial request.</dd>

      <dt>Protocol data charset conversion</dt>
      <dd>If mod_authnz_fcgi runs in an EBCDIC compilation
      environment, all FastCGI protocol data is written in EBCDIC
      and expected to be received in EBCDIC.</dd>

      <dt>Multiple requests per connection</dt>
      <dd>Currently the connection to the FastCGI authorizer is
      closed after every phase of processing.  For example, if the
      authorizer handles separate <em>authn</em> and <em>authz</em>
      phases then two connections will be used.</dd>

      <dt>URI Mapping</dt>
      <dd>URIs from clients can't be mapped, such as with the <directive>
      ProxyPass</directive> used with FastCGI responders.</dd>

    </dl>

</section>

<section id="logging"><title>Logging</title>

    <ol>
        <li>Processing errors are logged at log level <code>error</code>
        and higher.</li>
        <li>Messages written by the application are logged at log
        level <code>warn</code>.</li>
        <li>General messages for debugging are logged at log level
        <code>debug</code>.</li>
        <li>Environment variables passed to the application are
        logged at log level <code>trace2</code>. The value of the 
        <code>REMOTE_PASSWD</code> variable will be obscured,
        but <strong>any other sensitive data will be visible in the 
        log</strong>.</li>
        <li>All I/O between the module and the FastCGI application,
        including all environment variables, will be logged in printable
        and hex format at log level <code>trace5</code>.  <strong>All
        sensitive data will be visible in the log.</strong></li>
    </ol>

    <p><directive module="core">LogLevel</directive> can be used
    to configure a log level specific to mod_authnz_fcgi.  For
    example:</p>

<highlight language="config">
LogLevel info authnz_fcgi:trace8
</highlight>

</section>

<directivesynopsis>
<name>AuthnzFcgiDefineProvider</name>
<description>Defines a FastCGI application as a provider for
authentication and/or authorization</description>
<syntax>AuthnzFcgiDefineProvider <em>type</em> <em>provider-name</em>
<em>backend-address</em></syntax>
<default>none</default>
<contextlist><context>server config</context></contextlist>
<usage>
    <p>This directive is used to define a FastCGI application as
    a provider for a particular phase of authentication or
    authorization.</p>

    <dl>
      <dt><em>type</em></dt>
      <dd>This must be set to <em>authn</em> for authentication,
      <em>authz</em> for authorization, or <em>authnz</em> for
      a generic FastCGI authorizer which performs both checks.</dd>

      <dt><em>provider-name</em></dt>
      <dd>This is used to assign a name to the provider which is
      used in other directives such as 
      <directive module="mod_auth_basic">AuthBasicProvider</directive>
      and 
      <directive module="mod_authz_core">Require</directive>.</dd>

      <dt><em>backend-address</em></dt>
      <dd>This specifies the address of the application, in the form
      <em>fcgi://hostname:port/</em>.  The application process(es)
      must be managed independently, such as with
      <program>fcgistarter</program>.</dd>
    </dl>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>AuthnzFcgiCheckAuthnProvider</name>
<description>Enables a FastCGI application to handle the check_authn
authentication hook.</description>
<syntax>AuthnzFcgiCheckAuthnProvider <em>provider-name</em>|<code>None</code>
<em>option</em> ...</syntax>
<default>none</default>
<contextlist><context>directory</context></contextlist>
<usage>
    <p>This directive is used to enable a FastCGI authorizer to
    handle a specific processing phase of authentication or
    authorization.</p>

    <p>Some capabilities of FastCGI authorizers require enablement
    using this directive instead of
    <directive>AuthBasicProvider</directive>:</p>

    <ul>
      <li>Non-Basic authentication; generally, determining the user
      id of the client and returning it from the authorizer; see the
      <code>UserExpr</code> option below</li>
      <li>Selecting a custom response code; for a non-200 response
      from the authorizer, the code from the authorizer will be the
      status of the response</li>
      <li>Setting the body of a non-200 response; if the authorizer
      provides a response body with a non-200 response, that body
      will be returned to the client; up to 8192 bytes of text are
      supported</li>
    </ul>

    <dl>
      <dt><em>provider-name</em></dt>
      <dd>This is the name of a provider defined with <directive>
      AuthnzFcgiDefineProvider</directive>.</dd>

      <dt><code>None</code></dt>
      <dd>Specify <code>None</code> to disable a provider enabled
      with this directive in an outer scope, such as in a parent
      directory.</dd>

      <dt><em>option</em></dt>
      <dd>The following options are supported:
      
      <dl>
         <dt>Authoritative On|Off (default On)</dt>
         <dd>This controls whether or not other modules are allowed
         to run when this module has a FastCGI authorizer configured
         and it fails the request.</dd>

         <dt>DefaultUser <em>userid</em></dt>
         <dd>When the authorizer returns success and <code>UserExpr</code>
         is configured and evaluates to an empty string (e.g., authorizer
         didn't return a variable), this value will be used as the user
         id.  This is typically used when the authorizer has a concept of
         guest, or unauthenticated, users and guest users are mapped to
         some specific user id for logging and other purposes.</dd>

         <dt>RequireBasicAuth On|Off (default Off)</dt>
         <dd>This controls whether or not Basic auth is required
         before passing the request to the authorizer.  If required,
         the authorizer won't be invoked without a user id and
         password; 401 will be returned for a request without that.</dd>

         <dt>UserExpr <em>expr</em> (no default)</dt>
         <dd>When Basic authentication isn't provided by the client
         and the authorizer determines the user, this expression,
         evaluated after calling the authorizer, determines the
         user.  The expression follows <a href="../expr.html">
         ap_expr syntax</a> and must resolve to a string.  A typical
         use is to reference a <code>Variable-<em>XXX</em></code> 
         setting returned by the authorizer using an option like
         <code>UserExpr "%{reqenv:<em>XXX</em>}"</code>.  If
         this option is specified and the user id can't be retrieved
         using the expression after a successful authentication, the
         request will be rejected with a 500 error.</dd>

       </dl>
      </dd>
     </dl>
</usage>
</directivesynopsis>

</modulesynopsis>