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<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<!-- $LastChangedRevision$ -->
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<modulesynopsis metafile="mod_auth_digest.xml.meta">
<name>mod_auth_digest</name>
<description>User authentication using MD5
Digest Authentication.</description>
<status>Experimental</status>
<sourcefile>mod_auth_digest.c</sourcefile>
<identifier>auth_digest_module</identifier>
<summary>
<p>This module implements HTTP Digest Authentication. However, it
has not been extensively tested and is therefore marked
experimental.</p>
</summary>
<seealso><directive module="core">AuthName</directive></seealso>
<seealso><directive module="core">AuthType</directive></seealso>
<seealso><directive module="core">Require</directive></seealso>
<seealso><directive module="core">Satisfy</directive></seealso>
<section id="using"><title>Using Digest Authentication</title>
<p>Using MD5 Digest authentication is very simple. Simply set
up authentication normally, using <code>AuthType Digest</code> and
<directive module="mod_auth_digest">AuthDigestFile</directive> instead
of the normal <code>AuthType Basic</code> and <directive
module="mod_auth">AuthUserFile</directive>; also, replace any <directive
module="mod_auth">AuthGroupFile</directive> with <directive
module="mod_auth_digest">AuthDigestGroupFile</directive>. Then add a
<directive module="mod_auth_digest">AuthDigestDomain</directive> directive
containing at least the root URI(s) for this protection space.</p>
<p>Appropriate user (text) files can be created using the
<program>htdigest</program> tool.</p>
<example><title>Example:</title>
<Location /private/><br />
<indent>
AuthType Digest<br />
AuthName "private area"<br />
AuthDigestDomain /private/ http://mirror.my.dom/private2/<br />
AuthDigestFile /web/auth/.digest_pw<br />
Require valid-user<br />
</indent>
</Location>
</example>
<note><title>Note</title>
<p>Digest authentication provides a more secure password system
than Basic authentication, but only works with supporting
browsers. As of November 2002, the major browsers that support digest
authentication are <a href="http://www.opera.com/">Opera</a>, <a
href="http://www.microsoft.com/windows/ie/">MS Internet
Explorer</a> (fails when used with a query string - see "<a href="#msie"
>Working with MS Internet Explorer</a>" below for a workaround), <a
href="http://www.w3.org/Amaya/">Amaya</a>, <a
href="http://www.mozilla.org">Mozilla</a> and <a
href="http://channels.netscape.com/ns/browsers/download.jsp"
>Netscape</a> since version 7. Since digest authentication is not
as widely implemented as basic authentication, you should use it only
in controlled environments.</p>
</note>
</section>
<section id="msie"><title>Working with MS Internet Explorer</title>
<p>The Digest authentication implementation in previous Internet
Explorer for Windows versions (5 and 6) had issues, namely that
<code>GET</code> requests with a query string were not RFC compliant.
There are a few ways to work around this issue.</p>
<p>
The first way is to use <code>POST</code> requests instead of
<code>GET</code> requests to pass data to your program. This method
is the simplest approach if your application can work with this
limitation.
</p>
<p>Since version 2.0.51 Apache also provides a workaround in the
<code>AuthDigestEnableQueryStringHack</code> environment variable.
If <code>AuthDigestEnableQueryStringHack</code> is set for the
request, Apache will take steps to work around the MSIE bug and
remove the query string from the digest comparison. Using this
method would look similar to the following.</p>
<example><title>Using Digest Authentication with MSIE:</title>
BrowserMatch "MSIE" AuthDigestEnableQueryStringHack=On
</example>
<p>This workaround is not necessary for MSIE 7, though enabling it does
not cause any compatibility issues or significant overhead.</p>
<p>See the <directive module="mod_setenvif">BrowserMatch</directive>
directive for more details on conditionally setting environment
variables</p>
</section>
<directivesynopsis>
<name>AuthDigestFile</name>
<description>Location of the text file containing the list
of users and encoded passwords for digest authentication</description>
<syntax>AuthDigestFile <var>file-path</var></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>The <directive>AuthDigestFile</directive> directive sets the
name of a textual file containing the list of users and encoded
passwords for digest authentication. <var>File-path</var> is the
absolute path to the user file.</p>
<p>The digest file uses a special format. Files in this format
can be created using the <program>htdigest</program> utility found in
the <code>support/</code> subdirectory of the Apache distribution.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestGroupFile</name>
<description>Name of the text file containing the list of groups
for digest authentication</description>
<syntax>AuthDigestGroupFile <var>file-path</var></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>The <directive>AuthDigestGroupFile</directive> directive sets
the name of a textual file containing the list of groups and their
members (user names). <var>File-path</var> is the absolute path to
the group file.</p>
<p>Each line of the group file contains a groupname followed by
a colon, followed by the member usernames separated by spaces.
Example:</p>
<example>mygroup: bob joe anne</example>
<p>Note that searching large text files is <em>very</em>
inefficient.</p>
<note type="warning"><title>Security:</title>
<p>Make sure that the <directive>AuthGroupFile</directive> is stored
outside the document tree of the web-server; do <em>not</em> put it in
the directory that it protects. Otherwise, clients may be able
to download the <directive>AuthGroupFile</directive>.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestQop</name>
<description>Determines the quality-of-protection to use in digest
authentication</description>
<syntax>AuthDigestQop none|auth|auth-int [auth|auth-int]</syntax>
<default>AuthDigestQop auth</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>The <directive>AuthDigestQop</directive> directive determines
the <dfn>quality-of-protection</dfn> to use. <code>auth</code> will only do
authentication (username/password); <code>auth-int</code> is
authentication plus integrity checking (an MD5 hash of the entity
is also computed and checked); <code>none</code> will cause the module
to use the old RFC-2069 digest algorithm (which does not include
integrity checking). Both <code>auth</code> and <code>auth-int</code> may
be specified, in which the case the browser will choose which of
these to use. <code>none</code> should only be used if the browser for
some reason does not like the challenge it receives otherwise.</p>
<note>
<code>auth-int</code> is not implemented yet.
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestNonceLifetime</name>
<description>How long the server nonce is valid</description>
<syntax>AuthDigestNonceLifetime <var>seconds</var></syntax>
<default>AuthDigestNonceLifetime 300</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>The <directive>AuthDigestNonceLifetime</directive> directive
controls how long the server nonce is valid. When the client
contacts the server using an expired nonce the server will send
back a 401 with <code>stale=true</code>. If <var>seconds</var> is
greater than 0 then it specifies the amount of time for which the
nonce is valid; this should probably never be set to less than 10
seconds. If <var>seconds</var> is less than 0 then the nonce never
expires. <!-- Not implemented yet: If <var>seconds</var> is 0 then
the nonce may be used exactly once by the client. Note that while
one-time-nonces provide higher security against replay attacks,
they also have significant performance implications, as the
browser cannot pipeline or multiple connections for the
requests. Because browsers cannot easily detect that
one-time-nonces are being used, this may lead to browsers trying
to pipeline requests and receiving 401 responses for all but the
first request, requiring the browser to resend the requests. Note
also that the protection against reply attacks only makes sense
for dynamically generated content and things like POST requests;
for static content the attacker may already have the complete
response, so one-time-nonces do not make sense here. -->
</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestNonceFormat</name>
<description>Determines how the nonce is generated</description>
<syntax>AuthDigestNonceFormat <var>format</var></syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<note>Not implemented yet.</note>
<!-- The AuthDigestNonceFormat directive determines how the nonce is
generated. -->
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestNcCheck</name>
<description>Enables or disables checking of the nonce-count sent by the
server</description>
<syntax>AuthDigestNcCheck On|Off</syntax>
<default>AuthDigestNcCheck Off</default>
<contextlist><context>server config</context></contextlist>
<usage>
<note>
Not implemented yet.
</note>
<!--
<p>The AuthDigestNcCheck directive enables or disables the checking of the
nonce-count sent by the server.</p>
<p>While recommended from a security standpoint, turning this directive
On has one important performance implication. To check the nonce-count
*all* requests (which have an Authorization header, irrespective of
whether they require digest authentication) must be serialized through
a critical section. If the server is handling a large number of
requests which contain the Authorization header then this may noticeably
impact performance.</p>
-->
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestAlgorithm</name>
<description>Selects the algorithm used to calculate the challenge and
response hases in digest authentication</description>
<syntax>AuthDigestAlgorithm MD5|MD5-sess</syntax>
<default>AuthDigestAlgorithm MD5</default>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>The <directive>AuthDigestAlgorithm</directive> directive
selects the algorithm used to calculate the challenge and response
hashes.</p>
<note>
<code>MD5-sess</code> is not correctly implemented yet.
</note>
<!--
<p>To use <code>MD5-sess</code> you must first code up the
<code>get_userpw_hash()</code> function in
<code>mod_auth_digest.c</code>.</p>
-->
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestDomain</name>
<description>URIs that are in the same protection space for digest
authentication</description>
<syntax>AuthDigestDomain <var>URI</var> [<var>URI</var>] ...</syntax>
<contextlist><context>directory</context><context>.htaccess</context>
</contextlist>
<override>AuthConfig</override>
<usage>
<p>The <directive>AuthDigestDomain</directive> directive allows
you to specify one or more URIs which are in the same protection
space (<em>i.e.</em> use the same realm and username/password info).
The specified URIs are prefixes, <em>i.e.</em> the client will assume
that all URIs "below" these are also protected by the same
username/password. The URIs may be either absolute URIs (<em>i.e.</em>
including a scheme, host, port, etc) or relative URIs.</p>
<p>This directive <em>should</em> always be specified and
contain at least the (set of) root URI(s) for this space.
Omitting to do so will cause the client to send the
Authorization header for <em>every request</em> sent to this
server. Apart from increasing the size of the request, it may
also have a detrimental effect on performance if <directive
module="mod_auth_digest">AuthDigestNcCheck</directive> is on.</p>
<p>The URIs specified can also point to different servers, in
which case clients (which understand this) will then share
username/password info across multiple servers without
prompting the user each time.</p>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>AuthDigestShmemSize</name>
<description>The amount of shared memory to allocate for keeping track
of clients</description>
<syntax>AuthDigestShmemSize <var>size</var></syntax>
<default>AuthDigestShmemSize 1000</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>AuthDigestShmemSize</directive> directive defines
the amount of shared memory, that will be allocated at the server
startup for keeping track of clients. Note that the shared memory
segment cannot be set less than the space that is neccessary for
tracking at least <em>one</em> client. This value is dependant on your
system. If you want to find out the exact value, you may simply
set <directive>AuthDigestShmemSize</directive> to the value of
<code>0</code> and read the error message after trying to start the
server.</p>
<p>The <var>size</var> is normally expressed in Bytes, but you
may let the number follow a <code>K</code> or an <code>M</code> to
express your value as KBytes or MBytes. For example, the following
directives are all equivalent:</p>
<example>
AuthDigestShmemSize 1048576<br />
AuthDigestShmemSize 1024K<br />
AuthDigestShmemSize 1M
</example>
</usage>
</directivesynopsis>
</modulesynopsis>
|