mod_auth_digest
User authentication using MD5 Digest Authentication
Extension
mod_auth_digest.c
auth_digest_module

This module implements HTTP Digest Authentication (RFC2617), and provides a more secure alternative to mod_auth_basic.

AuthName
AuthType
Require
Match
Authentication howto

# Using Digest Authentication

To use MD5 Digest authentication, simply change the normal `AuthType Basic` and AuthBasicProvider to `AuthType Digest` and AuthDigestProvider, when setting up authentication, then add a AuthDigestDomain directive containing at least the root URI(s) for this protection space.

Appropriate user (text) files can be created using the htdigest tool.

## 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>

## Note

Digest authentication is more secure than Basic authentication, but only works with supporting browsers. As of September 2004, major browsers that support digest authentication include Amaya, Konqueror, MS Internet Explorer for Mac OS X and Windows (although the Windows version fails when used with a query string -- see "Working with MS Internet Explorer" below for a workaround), Mozilla, Netscape 7, Opera, and Safari. lynx does not support digest authentication. Since digest authentication is not as widely implemented as basic authentication, you should use it only in environments where all users will have supporting browsers.

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

# Working with MS Internet Explorer

The Digest authentication implementation in previous Internet Explorer for Windows versions (5 and 6) had issues, namely that `GET` requests with a query string were not RFC compliant. There are a few ways to work around this issue.

The first way is to use `POST` requests instead of `GET` requests to pass data to your program. This method is the simplest approach if your application can work with this limitation.

Since version 2.0.51 Apache also provides a workaround in the `AuthDigestEnableQueryStringHack` environment variable. If `AuthDigestEnableQueryStringHack` 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.

## Using Digest Authentication with MSIE:

BrowserMatch "MSIE" AuthDigestEnableQueryStringHack=On

This workaround is not necessary for MSIE 7, though enabling it does not cause any compatibility issues or significant overhead.

See the BrowserMatch directive for more details on conditionally setting environment variables.

AuthDigestProvider
Sets the authentication provider(s) for this location
AuthDigestProvider provider-name [provider-name] ...
AuthDigestProvider file
directory
.htaccess
AuthConfig

The AuthDigestProvider directive sets which provider is used to authenticate the users for this location. The default `file` provider is implemented by the mod_authn_file module. Make sure that the chosen provider module is present in the server.

See mod_authn_dbm, mod_authn_file, mod_authn_dbd and mod_authn_socache for providers.

AuthDigestQop
Determines the quality-of-protection to use in digest authentication
AuthDigestQop none|auth|auth-int [auth|auth-int]
AuthDigestQop auth
directory
.htaccess
AuthConfig

The AuthDigestQop directive determines the quality-of-protection to use. `auth` will only do authentication (username/password); `auth-int` is authentication plus integrity checking (an MD5 hash of the entity is also computed and checked); `none` will cause the module to use the old RFC-2069 digest algorithm (which does not include integrity checking). Both `auth` and `auth-int` may be specified, in which the case the browser will choose which of these to use. `none` should only be used if the browser for some reason does not like the challenge it receives otherwise.

`auth-int` is not implemented yet.

AuthDigestNonceLifetime
How long the server nonce is valid
AuthDigestNonceLifetime seconds
AuthDigestNonceLifetime 300
directory
.htaccess
AuthConfig

The AuthDigestNonceLifetime 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 `stale=true`. If seconds 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 seconds is less than 0 then the nonce never expires.

AuthDigestNonceFormat
Determines how the nonce is generated
AuthDigestNonceFormat format
directory
.htaccess
AuthConfig

Not implemented yet.

AuthDigestNcCheck
Enables or disables checking of the nonce-count sent by the server
AuthDigestNcCheck On|Off
AuthDigestNcCheck Off
server config

Not implemented yet.

AuthDigestAlgorithm
Selects the algorithm used to calculate the challenge and response hashes in digest authentication
AuthDigestAlgorithm MD5|MD5-sess
AuthDigestAlgorithm MD5
directory
.htaccess
AuthConfig

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

`MD5-sess` is not correctly implemented yet.

AuthDigestDomain
URIs that are in the same protection space for digest authentication
AuthDigestDomain URI [URI] ...
directory
.htaccess
AuthConfig

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. Apart from increasing the size of the request, it may also have a detrimental effect on performance if AuthDigestNcCheck is on.

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.

AuthDigestShmemSize
The amount of shared memory to allocate for keeping track of clients
AuthDigestShmemSize size
AuthDigestShmemSize 1000
server config

The AuthDigestShmemSize 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 necessary for tracking at least one client. This value is dependant on your system. If you want to find out the exact value, you may simply set AuthDigestShmemSize to the value of `0` and read the error message after trying to start the server.

The size is normally expressed in Bytes, but you may follow the number with a `K` or an `M` to express your value as KBytes or MBytes. For example, the following directives are all equivalent:

AuthDigestShmemSize 1048576
AuthDigestShmemSize 1024K
AuthDigestShmemSize 1M