Apache Module mod_auth_dbm

AuthDBMAuthoritative Directive

Description:	Sets whether authentication and authorization will be passed on to lower level modules
Syntax:	AuthDBMAuthoritative On|Off
Default:	AuthDBMAuthoritative On
Context:	directory, .htaccess
Override:	AuthConfig
Status:	Extension
Module:	mod_auth_dbm

Setting the AuthDBMAuthoritative directive explicitly to Off allows for both authentication and authorization to be passed on to lower level modules (as defined in the modules.c files) if there is no userID or rule matching the supplied userID. If there is a userID and/or rule specified; the usual password and access checks will be applied and a failure will give an "Authentication Required" reply.

So if a userID appears in the database of more than one module; or if a valid Require directive applies to more than one module; then the first module will verify the credentials; and no access is passed on; regardless of the AuthDBMAuthoritative setting.

A common use for this is in conjunction with one of the basic auth modules; such as mod_auth. Whereas this DBM module supplies the bulk of the user credential checking; a few (administrator) related accesses fall through to a lower level with a well protected .htpasswd file.

By default, control is not passed on and an unknown userID or rule will result in an "Authentication Required" reply. Not setting it thus keeps the system secure and forces an NCSA compliant behaviour.

AuthDBMGroupFile Directive

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

The AuthDBMGroupFile directive sets the name of a DBM file containing the list of user groups for user authentication. 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.

Security: 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:

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

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 authentication module. This is what www.telescope.org uses for its combined password and group database.

AuthDBMType Directive

Description:	Sets the type of database file that is used to store passwords
Syntax:	AuthDBMType default|SDBM|GDBM|NDBM|DB
Default:	AuthDBMType default
Context:	directory, .htaccess
Override:	AuthConfig
Status:	Extension
Module:	mod_auth_dbm
Compatibility:	Available in version 2.0.30 and later.

Sets the type of database file that is used to store the passwords. 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 password files is configured to use the same type of database.

AuthDBMUserFile Directive

Description:	Sets thename of a database file containing the list of users and passwords for authentication
Syntax:	AuthDBMUserFile file-path
Context:	directory, .htaccess
Override:	AuthConfig
Status:	Extension
Module:	mod_auth_dbm

The AuthDBMUserFile directive sets the name of a DBM file containing the list of users and passwords for user authentication. File-path is the absolute path to the user file.

The user file is keyed on the username. The value for a user is the encrypted password, optionally followed by a colon and arbitrary data. The colon and the data following it will be ignored by the server.

Important compatibility note: The implementation of "dbmopen" in the apache modules reads the string length of the hashed values from the DBM data structures, rather than relying upon the string being NULL-appended. Some applications, such as the Netscape web server, rely upon the string being NULL-appended, so if you are having trouble using DBM files interchangeably between applications this may be a part of the problem.

A perl script called dbmmanage is included with Apache. This program can be used to create and update DBM format password files for use with this module.