/Apache HTTP Server

Apache Module mod_authz_dbm

Description: Group authorization using DBM files
Status: Extension
ModuleIdentifier: authz_dbm_module
SourceFile: mod_authz_dbm.c
Compatibility: Available in Apache 2.1 and later


This module provides authorization capabilities so that authenticated users can be allowed or denied access to portions of the web site by group membership. Similar functionality is provided by mod_authz_groupfile.

The Require Directives

Apache's Require directives are used during the authorization phase to ensure that a user is allowed to access a resource. mod_authz_dbm extends the authorization types with dbm-group.

Since v2.4.8, expressions are supported within the DBM require directives.

Require dbm-group

This directive specifies group membership that is required for the user to gain access.

Require dbm-group admin

Require dbm-file-group

When this directive is specified, the user must be a member of the group assigned to the file being accessed.

Require dbm-file-group

Example usage

Note that using mod_authz_dbm requires you to require dbm-group instead of group:

<Directory "/foo/bar">
  AuthType Basic
  AuthName "Secure Area"
  AuthBasicProvider dbm
  AuthDBMUserFile "site/data/users"
  AuthDBMGroupFile "site/data/users"
  Require dbm-group admin

AuthDBMGroupFile Directive

Description: Sets the name of the database file containing the list of user groups for authorization
AuthDBMGroupFile file-path
Context: directory, .htaccess
Override: AuthConfig
Status: Extension
Module: mod_authz_dbm

The AuthDBMGroupFile directive sets the name of a DBM file containing the list of user groups for user authorization. File-path is the absolute path to the group file.

The group file is keyed on the username. The value for a user is a comma-separated list of the groups to which the users belongs. There must be no whitespace within the value, and it must never contain any colons.


Make sure that the AuthDBMGroupFile is stored outside the document tree of the web-server. Do not put it in the directory that it protects. Otherwise, clients will be able to download the AuthDBMGroupFile unless otherwise protected.

Combining Group and Password DBM files: In some cases it is easier to manage a single database which contains both the password and group details for each user. This simplifies any support programs that need to be written: they now only have to deal with writing to and locking a single DBM file. This can be accomplished by first setting the group and password files to point to the same DBM:

AuthDBMGroupFile "/www/userbase"
AuthDBMUserFile "/www/userbase"

The key for the single DBM is the username. The value consists of

Encrypted Password : List of Groups [ : (ignored) ]

The password section contains the encrypted password as before. This is followed by a colon and the comma separated list of groups. Other data may optionally be left in the DBM file after another colon; it is ignored by the authorization module. This is what www.telescope.org uses for its combined password and group database.

AuthzDBMType Directive

Description: Sets the type of database file that is used to store list of user groups
AuthzDBMType default|SDBM|GDBM|NDBM|DB
AuthzDBMType default
Context: directory, .htaccess
Override: AuthConfig
Status: Extension
Module: mod_authz_dbm

Sets the type of database file that is used to store the list of user groups. The default database type is determined at compile time. The availability of other types of database files also depends on compile-time settings.

It is crucial that whatever program you use to create your group files is configured to use the same type of database.

© 2017 The Apache Software Foundation
Licensed under the Apache License, Version 2.0.