Apache Module mod_auth_digest

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Description:	User authentication using MD5 Digest Authentication
Status:	Extension
Module Identifier:	auth_digest_module
Source File:	mod_auth_digest.c

Summary

This module implements HTTP Digest Authentication (RFC2617), and provides an alternative to mod_auth_basic where the password is not transmitted as cleartext. However, this does not lead to a significant security advantage over basic authentication. On the other hand, the password storage on the server is much less secure with digest authentication than with basic authentication. Therefore, using basic auth and encrypting the whole connection using mod_ssl is a much better alternative.

Topics

Using Digest Authentication

Bugfix checklist

Using Digest Authentication

To use MD5 Digest authentication, configure the location to be protected as shown in the below example:

Example:

<Location "/private/">
    AuthType Digest
    AuthName "private area"
    AuthDigestDomain "/private/" "http://mirror.my.dom/private2/"
    
    AuthDigestProvider file
    AuthUserFile "/web/auth/.digest_pw"
    Require valid-user
</Location>

AuthDigestDomain should list the locations that will be protected by this configuration.

The password file referenced in the AuthUserFile directive may be created and managed using the htdigest tool.

Note

Digest authentication was intended to be more secure than basic authentication, but no longer fulfills that design goal. A man-in-the-middle attacker can trivially force the browser to downgrade to basic authentication. And even a passive eavesdropper can brute-force the password using today's graphics hardware, because the hashing algorithm used by digest authentication is too fast. Another problem is that the storage of the passwords on the server is insecure. The contents of a stolen htdigest file can be used directly for digest authentication. Therefore using mod_ssl to encrypt the whole connection is strongly recommended.

mod_auth_digest only works properly on platforms where APR supports shared memory.

AuthDigestAlgorithm Directive

Description:	Selects the algorithm used to calculate the challenge and response hashes in digest authentication
Syntax:	`AuthDigestAlgorithm MD5\|MD5-sess`
Default:	`AuthDigestAlgorithm MD5`
Context:	directory, .htaccess
Override:	AuthConfig
Status:	Extension
Module:	mod_auth_digest

The AuthDigestAlgorithm directive selects the algorithm used to calculate the challenge and response hashes.

MD5-sess is not correctly implemented yet.

AuthDigestDomain Directive

Description:	URIs that are in the same protection space for digest authentication
Syntax:	`AuthDigestDomain URI [URI] ...`
Context:	directory, .htaccess
Override:	AuthConfig
Status:	Extension
Module:	mod_auth_digest

The AuthDigestDomain directive allows you to specify one or more URIs which are in the same protection space (i.e. use the same realm and username/password info). The specified URIs are prefixes; the client will assume that all URIs "below" these are also protected by the same username/password. The URIs may be either absolute URIs (i.e. including a scheme, host, port, etc.) or relative URIs.

This directive should 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 every request sent to this server.

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.