2 <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
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10 The ASF licenses this file to You under the Apache License, Version 2.0
11 (the "License"); you may not use this file except in compliance with
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23 <modulesynopsis metafile="mod_auth_digest.xml.meta">
25 <name>mod_auth_digest</name>
26 <description>User authentication using MD5
27 Digest Authentication</description>
28 <status>Extension</status>
29 <sourcefile>mod_auth_digest.c</sourcefile>
30 <identifier>auth_digest_module</identifier>
33 <p>This module implements HTTP Digest Authentication
34 (<a href="http://www.faqs.org/rfcs/rfc2617.html">RFC2617</a>), and
35 provides a more secure alternative to <module>mod_auth_basic</module>.</p>
38 <seealso><directive module="mod_authn_core">AuthName</directive></seealso>
39 <seealso><directive module="mod_authn_core">AuthType</directive></seealso>
40 <seealso><directive module="mod_authz_core">Require</directive></seealso>
41 <seealso><a href="../howto/auth.html">Authentication howto</a></seealso>
43 <section id="using"><title>Using Digest Authentication</title>
45 <p>To use MD5 Digest authentication, simply
46 change the normal <code>AuthType Basic</code> and
47 <directive module="mod_auth_basic">AuthBasicProvider</directive>
48 to <code>AuthType Digest</code> and
49 <directive module="mod_auth_digest">AuthDigestProvider</directive>,
50 when setting up authentication, then add a
51 <directive module="mod_auth_digest"
52 >AuthDigestDomain</directive> directive containing at least the root
53 URI(s) for this protection space.</p>
55 <p>Appropriate user (text) files can be created using the
56 <program>htdigest</program> tool.</p>
58 <example><title>Example:</title>
59 <highlight language="config">
60 <Location /private/>
62 AuthName "private area"
63 AuthDigestDomain /private/ http://mirror.my.dom/private2/
65 AuthDigestProvider file
66 AuthUserFile /web/auth/.digest_pw
72 <note><title>Note</title>
73 <p>Digest authentication is more secure than Basic authentication,
74 but only works with supporting browsers. As of September 2004, major
75 browsers that support digest authentication include <a
76 href="http://www.w3.org/Amaya/">Amaya</a>, <a
77 href="http://konqueror.kde.org/">Konqueror</a>, <a
78 href="http://www.microsoft.com/windows/ie/">MS Internet Explorer</a>
79 for Mac OS X and Windows (although the Windows version fails when
80 used with a query string -- see "<a href="#msie" >Working with MS
81 Internet Explorer</a>" below for a workaround), <a
82 href="http://www.mozilla.org">Mozilla</a>, <a
83 href="http://channels.netscape.com/ns/browsers/download.jsp">
84 Netscape</a> 7, <a href="http://www.opera.com/">Opera</a>, and <a
85 href="http://www.apple.com/safari/">Safari</a>. <a
86 href="http://lynx.isc.org/">lynx</a> does <strong>not</strong>
87 support digest authentication. Since digest authentication is not as
88 widely implemented as basic authentication, you should use it only
89 in environments where all users will have supporting browsers.</p>
90 <p><module>mod_auth_digest</module> only works properly on platforms
91 where APR supports shared memory.</p>
95 <section id="msie"><title>Working with MS Internet Explorer</title>
96 <p>The Digest authentication implementation in previous Internet
97 Explorer for Windows versions (5 and 6) had issues, namely that
98 <code>GET</code> requests with a query string were not RFC compliant.
99 There are a few ways to work around this issue.</p>
102 The first way is to use <code>POST</code> requests instead of
103 <code>GET</code> requests to pass data to your program. This method
104 is the simplest approach if your application can work with this
108 <p>Since version 2.0.51 Apache also provides a workaround in the
109 <code>AuthDigestEnableQueryStringHack</code> environment variable.
110 If <code>AuthDigestEnableQueryStringHack</code> is set for the
111 request, Apache will take steps to work around the MSIE bug and
112 remove the query string from the digest comparison. Using this
113 method would look similar to the following.</p>
115 <example><title>Using Digest Authentication with MSIE:</title>
116 <highlight language="config">
117 BrowserMatch "MSIE" AuthDigestEnableQueryStringHack=On
121 <p>This workaround is not necessary for MSIE 7, though enabling it does
122 not cause any compatibility issues or significant overhead.</p>
124 <p>See the <directive module="mod_setenvif">BrowserMatch</directive>
125 directive for more details on conditionally setting environment
131 <name>AuthDigestProvider</name>
132 <description>Sets the authentication provider(s) for this location</description>
133 <syntax>AuthDigestProvider <var>provider-name</var>
134 [<var>provider-name</var>] ...</syntax>
135 <default>AuthDigestProvider file</default>
136 <contextlist><context>directory</context><context>.htaccess</context>
138 <override>AuthConfig</override>
141 <p>The <directive>AuthDigestProvider</directive> directive sets
142 which provider is used to authenticate the users for this location.
143 The default <code>file</code> provider is implemented
144 by the <module>mod_authn_file</module> module. Make sure
145 that the chosen provider module is present in the server.</p>
147 <p>See <module>mod_authn_dbm</module>, <module>mod_authn_file</module>,
148 <module>mod_authn_dbd</module> and <module>mod_authn_socache</module>
154 <name>AuthDigestQop</name>
155 <description>Determines the quality-of-protection to use in digest
156 authentication</description>
157 <syntax>AuthDigestQop none|auth|auth-int [auth|auth-int]</syntax>
158 <default>AuthDigestQop auth</default>
159 <contextlist><context>directory</context><context>.htaccess</context>
161 <override>AuthConfig</override>
164 <p>The <directive>AuthDigestQop</directive> directive determines
165 the <dfn>quality-of-protection</dfn> to use. <code>auth</code> will
166 only do authentication (username/password); <code>auth-int</code> is
167 authentication plus integrity checking (an MD5 hash of the entity
168 is also computed and checked); <code>none</code> will cause the module
169 to use the old RFC-2069 digest algorithm (which does not include
170 integrity checking). Both <code>auth</code> and <code>auth-int</code> may
171 be specified, in which the case the browser will choose which of
172 these to use. <code>none</code> should only be used if the browser for
173 some reason does not like the challenge it receives otherwise.</p>
176 <code>auth-int</code> is not implemented yet.
182 <name>AuthDigestNonceLifetime</name>
183 <description>How long the server nonce is valid</description>
184 <syntax>AuthDigestNonceLifetime <var>seconds</var></syntax>
185 <default>AuthDigestNonceLifetime 300</default>
186 <contextlist><context>directory</context><context>.htaccess</context>
188 <override>AuthConfig</override>
191 <p>The <directive>AuthDigestNonceLifetime</directive> directive
192 controls how long the server nonce is valid. When the client
193 contacts the server using an expired nonce the server will send
194 back a 401 with <code>stale=true</code>. If <var>seconds</var> is
195 greater than 0 then it specifies the amount of time for which the
196 nonce is valid; this should probably never be set to less than 10
197 seconds. If <var>seconds</var> is less than 0 then the nonce never
198 expires. <!-- Not implemented yet: If <var>seconds</var> is 0 then
199 the nonce may be used exactly once by the client. Note that while
200 one-time-nonces provide higher security against replay attacks,
201 they also have significant performance implications, as the
202 browser cannot pipeline or multiple connections for the
203 requests. Because browsers cannot easily detect that
204 one-time-nonces are being used, this may lead to browsers trying
205 to pipeline requests and receiving 401 responses for all but the
206 first request, requiring the browser to resend the requests. Note
207 also that the protection against replay attacks only makes sense
208 for dynamically generated content and things like POST requests;
209 for static content the attacker may already have the complete
210 response, so one-time-nonces do not make sense here. -->
216 <name>AuthDigestNonceFormat</name>
217 <description>Determines how the nonce is generated</description>
218 <syntax>AuthDigestNonceFormat <var>format</var></syntax>
219 <contextlist><context>directory</context><context>.htaccess</context>
221 <override>AuthConfig</override>
224 <note>Not implemented yet.</note>
225 <!-- The AuthDigestNonceFormat directive determines how the nonce is
231 <name>AuthDigestNcCheck</name>
232 <description>Enables or disables checking of the nonce-count sent by the
234 <syntax>AuthDigestNcCheck On|Off</syntax>
235 <default>AuthDigestNcCheck Off</default>
236 <contextlist><context>server config</context></contextlist>
243 <p>The AuthDigestNcCheck directive enables or disables the checking of the
244 nonce-count sent by the server.</p>
246 <p>While recommended from a security standpoint, turning this directive
247 On has one important performance implication. To check the nonce-count
248 *all* requests (which have an Authorization header, irrespective of
249 whether they require digest authentication) must be serialized through
250 a critical section. If the server is handling a large number of
251 requests which contain the Authorization header then this may noticeably
252 impact performance.</p>
258 <name>AuthDigestAlgorithm</name>
259 <description>Selects the algorithm used to calculate the challenge and
260 response hashes in digest authentication</description>
261 <syntax>AuthDigestAlgorithm MD5|MD5-sess</syntax>
262 <default>AuthDigestAlgorithm MD5</default>
263 <contextlist><context>directory</context><context>.htaccess</context>
265 <override>AuthConfig</override>
268 <p>The <directive>AuthDigestAlgorithm</directive> directive
269 selects the algorithm used to calculate the challenge and response
273 <code>MD5-sess</code> is not correctly implemented yet.
276 <p>To use <code>MD5-sess</code> you must first code up the
277 <code>get_userpw_hash()</code> function in
278 <code>mod_auth_digest.c</code>.</p>
284 <name>AuthDigestDomain</name>
285 <description>URIs that are in the same protection space for digest
286 authentication</description>
287 <syntax>AuthDigestDomain <var>URI</var> [<var>URI</var>] ...</syntax>
288 <contextlist><context>directory</context><context>.htaccess</context>
290 <override>AuthConfig</override>
293 <p>The <directive>AuthDigestDomain</directive> directive allows
294 you to specify one or more URIs which are in the same protection
295 space (<em>i.e.</em> use the same realm and username/password info).
296 The specified URIs are prefixes; the client will assume
297 that all URIs "below" these are also protected by the same
298 username/password. The URIs may be either absolute URIs (<em>i.e.</em>
299 including a scheme, host, port, etc.) or relative URIs.</p>
301 <p>This directive <em>should</em> always be specified and
302 contain at least the (set of) root URI(s) for this space.
303 Omitting to do so will cause the client to send the
304 Authorization header for <em>every request</em> sent to this
305 server. Apart from increasing the size of the request, it may
306 also have a detrimental effect on performance if <directive
307 module="mod_auth_digest">AuthDigestNcCheck</directive> is on.</p>
309 <p>The URIs specified can also point to different servers, in
310 which case clients (which understand this) will then share
311 username/password info across multiple servers without
312 prompting the user each time. </p>
317 <name>AuthDigestShmemSize</name>
318 <description>The amount of shared memory to allocate for keeping track
319 of clients</description>
320 <syntax>AuthDigestShmemSize <var>size</var></syntax>
321 <default>AuthDigestShmemSize 1000</default>
322 <contextlist><context>server config</context></contextlist>
325 <p>The <directive>AuthDigestShmemSize</directive> directive defines
326 the amount of shared memory, that will be allocated at the server
327 startup for keeping track of clients. Note that the shared memory
328 segment cannot be set less than the space that is necessary for
329 tracking at least <em>one</em> client. This value is dependant on your
330 system. If you want to find out the exact value, you may simply
331 set <directive>AuthDigestShmemSize</directive> to the value of
332 <code>0</code> and read the error message after trying to start the
335 <p>The <var>size</var> is normally expressed in Bytes, but you
336 may follow the number with a <code>K</code> or an <code>M</code> to
337 express your value as KBytes or MBytes. For example, the following
338 directives are all equivalent:</p>
340 <highlight language="config">
341 AuthDigestShmemSize 1048576
342 AuthDigestShmemSize 1024K
343 AuthDigestShmemSize 1M