Apache Module mod_auth_digest
Description: | User authentication using MD5 Digest Authentication |
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Status: | Extension |
ModuleIdentifier: | auth_digest_module |
SourceFile: | 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.
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 pasword 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 |
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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 |
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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.
AuthDigestNonceLifetime Directive
Description: | How long the server nonce is valid |
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Syntax: | AuthDigestNonceLifetime seconds |
Default: | AuthDigestNonceLifetime 300 |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_auth_digest |
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.
AuthDigestProvider Directive
Description: | Sets the authentication provider(s) for this location |
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Syntax: | AuthDigestProvider provider-name [provider-name] ... |
Default: | AuthDigestProvider file |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_auth_digest |
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 Directive
Description: | Determines the quality-of-protection to use in digest authentication |
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Syntax: | AuthDigestQop none|auth|auth-int [auth|auth-int] |
Default: | AuthDigestQop auth |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_auth_digest |
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. AuthDigestShmemSize Directive
Description: | The amount of shared memory to allocate for keeping track of clients |
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Syntax: | AuthDigestShmemSize size |
Default: | AuthDigestShmemSize 1000 |
Context: | server config |
Status: | Extension |
Module: | mod_auth_digest |
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 dependent 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
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