Module mod_auth

This module provides for user authentication using text files.

Status: Base
Source File: mod_auth.c
Module Identifier: auth_module

Summary

This module allows the use of HTTP Basic Authentication to restrict access by looking up users in plain text password and group files. Similar functionality and greater scalability is provided by mod_auth_dbm and mod_auth_db. HTTP Digest Authentication is provided by mod_auth_digest.

Note that these credential-based security mechanisms are only as strong as your Web server's security. As a rule, they are not as strong as the operating system's own security system.

Directives

• AuthGroupFile
• AuthUserFile
• AuthAuthoritative

See also: require, satisfy, and mod_auth require keywords.

mod_auth Require Keywords

The mod_auth module supports the following keywords that can be given to the Require directive:

user username [...]

The supplied username and password must be in the AuthUserFile database, and the username must also be one of those listed on the Require directive.

group groupname [...]

The supplied username and password must be in the AuthUserFile database, and the username must also be a member of one of the named groups in the AuthGroupFile database.

valid-user

The supplied username and password must be in the AuthUserFile database. Any valid username from that file will be allowed.

file-owner

[Available after Apache 1.3.20] The supplied username and password must be in the AuthUserFile database, and the username must also match the system's name for the owner of the file being requested. That is, if the operating system say the requested file is owned by jones, then the username used to access it through the Web must be jones as well.

file-group

[Available after Apache 1.3.20] The supplied username and password must be in the AuthUserFile database, the name of the group that owns the file must be in the AuthGroupFile database, and the username must be a member of that group. For example, if the operating system says the requested file is owned by group accounts, the group accounts must be in the AuthGroupFile database and the username used in the request must be a member of that group.

Example of Require file-owner

Consider a multi-user system running the Apache Web server, with each user having his or her own files in ~/public_html/private. Assuming that there is a single AuthUserFile database that lists all of their usernames, and that their Web usernames match the ones that actually own the files on the server, then the following stanza would allow only the user himself access to his own files. User jones would not be allowed to access files in /home/smith/public_html/private unless they were owned by jones instead of smith.

    <Directory /home/*/public_html/private>
        AuthType Basic
        AuthName MyPrivateFile
        AuthUserFile /usr/local/apache/etc/.htpasswd-allusers
        Satisfy All
        Require file-owner
    </Directory>

AuthGroupFile directive

The AuthGroupFile directive sets the name of a textual file containing the list of user groups for user authentication. File-path is the path to the group file. If it is not absolute (i.e., if it doesn't begin with a slash), it is treated as relative to the ServerRoot.

Each line of the group file contains a groupname followed by a colon, followed by the member usernames separated by spaces. Example:

mygroup: bob joe anne

Security: make sure that the AuthGroupFile 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 AuthGroupFile.

See also AuthName, AuthType and AuthUserFile.

AuthUserFile directive

The AuthUserFile directive sets the name of a textual file containing the list of users and passwords for user authentication. File-path is the path to the user file. If it is not absolute (i.e., if it doesn't begin with a slash), it is treated as relative to the ServerRoot.

Each line of the user file contains a username followed by a colon, followed by the crypt() encrypted password. The behavior of multiple occurrences of the same user is undefined.

The utility htpasswd which is installed as part of the binary distribution, or which can be found in src/support, is used to maintain this password file. See the man page for more details. In short

htpasswd -c Filename username
Create a password file 'Filename' with 'username' as the initial ID. It will prompt for the password. htpasswd Filename username2
Adds or modifies in password file 'Filename' the 'username'.

Note that searching large text files is very inefficient; AuthDBMUserFile should be used instead.

Security:

Make sure that the AuthUserFile is stored outside the document tree of the web-server; do not put it in the directory that it protects. Otherwise, clients may be able to download the AuthUserFile.

Also be aware that null usernames are permitted, and null passwords as well (through Apache 1.3.20). If your AuthUserFile includes a line containing only a colon (':'), a 'Require valid-user' will allow access if both the username and password in the credentials are omitted.

AuthAuthoritative directive

Setting the AuthAuthoritative directive explicitly to 'off' allows for both authentication and authorization to be passed on to lower level modules (as defined in the Configuration and 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 Authorization 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 AuthAuthoritative setting.

A common use for this is in conjunction with one of the database modules; such as mod_auth_db.c, mod_auth_dbm.c, mod_auth_msql.c, and mod_auth_anon.c. These modules supply the bulk of the user credential checking; but a few (administrator) related accesses fall through to a lower level with a well protected AuthUserFile.

Default: By default; control is not passed on; and an unknown userID or rule will result in an Authorization Required reply. Not setting it thus keeps the system secure; and forces an NCSA compliant behavior.

Security: Do consider the implications of allowing a user to allow fall-through in his .htaccess file; and verify that this is really what you want; Generally it is easier to just secure a single .htpasswd file, than it is to secure a database such as mSQL. Make sure that the AuthUserFile 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 AuthUserFile.

See also AuthName, AuthType and AuthGroupFile.