MediaWiki is the powerful software on which Wikipedia and many other sites are built. It does not, however, come with the option to password protect pages from being viewed. (It can password protect pages from being edited.)
If you need to setup a private, members-only wiki for internal use, here is how you can do it with MediaWiki software and the Apache server extension mod_auth_mysql:
1. Install MediaWiki as usual. Create a user account for yourself.
2. Add the following line to your LocalSettings.php file, located in the root of your MediaWiki installation. This will cause MediaWiki to use a simple MD5 hash for user passwords in the database, instead of the more complicated “salted hash hash” that it normally uses.
$wgPasswordSalt = false;
3. Activate mod_auth_mysql in Apache. This is usually done with a LoadModule line in your Apache configuration file (httpd.conf), provided the module is available. (If not, you may need to compile or download the module.)
LoadModule mysql_auth_module libexec/apache2/mod_auth_mysql.so
4. Create a new MySQL user that has SELECT access to the “user_name” and “user_password” fields in the “user” table of your MediaWiki installation. Apache will use this MySQL user for connecting to the MediaWiki database.
5. Configure mod_auth_mysql to use the MediaWiki user table for authentication by placing the follow directives in your Apache configuration file:
AuthName "This wiki is password protected (make sure the first letter of the username is Uppercase)"
AuthType Basic
require valid-user
AuthMySQLEnable On
AuthMySQLHost localhost
AuthMySQLUser unprivilegeduser
AuthMySQLPassword thesecretpassword
AuthMySQLDB mediawikidatabase
AuthMySQLUserTable user
AuthMySQLNameField user_name
AuthMySQLPasswordField user_password
AuthMySQLPwEncryption md5
AuthMySQLAuthoritative On
6. Restart Apache.
Your installation of MediaWiki should now be password-protected, but your username and password will let you in. This protects the entire wiki; no one will even know that MediaWiki is present until they login. To give other people access, you can either create user accounts for them, or you can create a guest account that they can use until they sign themselves up.
P.S. Thanks to Gary Thornock for helping me with the details of installing mod_auth_mysql on FreeBSD.
UPDATE (2008-09-11):
The latest version of MediaWiki (version 1.13) uses a new password format which is incompatible with mod_auth_mysql. It prepends “:A:” to each MD5 hash. Here is a workaround:
1. Create a MySQL view that mirrors the username and password, minus the prefix:
CREATE VIEW user_view AS SELECT user_id, user_name, substring_index(user_password, ':', -1) AS user_password FROM user;
2. Configure mod_auth_mysql to use user_view instead of user as the lookup table.