How to: Secure a site using Apache

How to: Secure a site using Apache

If I had to, I would probably say that most people who use Apache do it to publish sites that are publicly accessible and/or have built-in security (say WordPress which manages itself access to the application and data). So now that I wanted to publish a site that request a username/password or some sort of restriction so that only I can see its data (think management console) I had no clue where to start.

Apache does offer both modalities which can be used independently or in combination: Authentication and Authorization.

Authentication means the user needs to provide credentials in order to access and its session is authenticated (identified) throughout its stay.

Authorization means the client is authorized to access the page. The individual user is not necessarily identified. For example if authorization is based on the source host (ip address) then there is no need for authentication (Apache Module mod_authz_host.)

Below is the relevant information to configure Apache in a simple way (obtained from: http://httpd.apache.org/docs/2.2/howto/auth.html)


There are three types of modules involved in the authentication and authorization process. You will usually need to choose at least one module from each group.

The module mod_authnz_ldap is both an authentication and authorization provider. The module mod_authn_alias is not an authentication provider in itself, but allows other authentication providers to be configured in a flexible manner.

The module mod_authz_host provides authorization and access control based on hostname, IP address or characteristics of the request, but is not part of the authentication provider system.

 


 

First, you need to create a password file. Exactly how you do this will vary depending on what authentication provider you have chosen. More on that later. To start with, we’ll use a text password file.

This file should be placed somewhere not accessible from the web. This is so that folks cannot download the password file. For example, if your documents are served out of /usr/local/apache/htdocs you might want to put the password file(s) in/usr/local/apache/passwd.

To create the file, use the htpasswd utility that came with Apache. This will be located in the bin directory of wherever you installed Apache. If you have installed Apache from a third-party package, it may be in your execution path.

To create the file, type:

htpasswd -c /usr/local/apache/passwd/passwords rbowen

htpasswd will ask you for the password, and then ask you to type it again to confirm it:

# htpasswd -c /usr/local/apache/passwd/passwords rbowen
New password: mypassword
Re-type new password: mypassword
Adding password for user rbowen

If htpasswd is not in your path, of course you’ll have to type the full path to the file to get it to run. With a default installation, it’s located at /usr/local/apache2/bin/htpasswd

Next, you’ll need to configure the server to request a password and tell the server which users are allowed access. You can do this either by editing the httpd.conf file or using an .htaccess file. For example, if you wish to protect the directory/usr/local/apache/htdocs/secret, you can use the following directives, either placed in the file /usr/local/apache/htdocs/secret/.htaccess, or placed in httpd.conf inside a <Directory /usr/local/apache/apache/htdocs/secret> section.

AuthType Basic
AuthName "Restricted Files"
# (Following line optional)
AuthBasicProvider file
AuthUserFile /usr/local/apache/passwd/passwords
Require user rbowen

Let’s examine each of those directives individually. The AuthType directive selects that method that is used to authenticate the user. The most common method is Basic, and this is the method implemented by mod_auth_basic. It is important to be aware, however, that Basic authentication sends the password from the client to the server unencrypted. This method should therefore not be used for highly sensitive data, unless accompanied by mod_ssl. Apache supports one other authentication method:AuthType Digest. This method is implemented by mod_auth_digest and is much more secure. Most recent browsers support Digest authentication.

The AuthName directive sets the Realm to be used in the authentication. The realm serves two major functions. First, the client often presents this information to the user as part of the password dialog box. Second, it is used by the client to determine what password to send for a given authenticated area.

So, for example, once a client has authenticated in the "Restricted Files" area, it will automatically retry the same password for any area on the same server that is marked with the "Restricted Files" Realm. Therefore, you can prevent a user from being prompted more than once for a password by letting multiple restricted areas share the same realm. Of course, for security reasons, the client will always need to ask again for the password whenever the hostname of the server changes.

The AuthBasicProvider is, in this case, optional, since file is the default value for this directive. You’ll need to use this directive if you are choosing a different source for authentication, such as mod_authn_dbm or mod_authn_dbd.

The AuthUserFile directive sets the path to the password file that we just created with htpasswd. If you have a large number of users, it can be quite slow to search through a plain text file to authenticate the user on each request. Apache also has the ability to store user information in fast database files. The mod_authn_dbm module provides the AuthDBMUserFile directive. These files can be created and manipulated with the dbmmanage program. Many other types of authentication options are available from third party modules in the Apache Modules Database.

Finally, the Require directive provides the authorization part of the process by setting the user that is allowed to access this region of the server. In the next section, we discuss various ways to use the Require directive.

 


 

The Satisfy directive can be used to specify that several criteria may be considered when trying to decide if a particular user will be granted admission. Satisfy can take as an argument one of two options – all or any. By default, it is assumed that the value is all. This means that if several criteria are specified, then all of them must be met in order for someone to get in. However, if set to any, then several criteria may be specified, but if the user satisfies any of these, then they will be granted entrance.

An example of this is using access control to assure that, although a resource is password protected from outside your network, all hosts inside the network will be given unauthenticated access to the resource. This would be accomplished by using the Satisfy directive, as shown below.

<Directory /usr/local/apache/htdocs/sekrit>
AuthType Basic
AuthName intranet
AuthUserFile /www/passwd/users
AuthGroupFile /www/passwd/groups
Require group customers
Order allow,deny
Allow from internal.com
Satisfy any
</Directory>

 


 

The directives above only let one person (specifically someone with a username of rbowen) into the directory. In most cases, you’ll want to let more than one person in. This is where the AuthGroupFile comes in.

If you want to let more than one person in, you’ll need to create a group file that associates group names with a list of users in that group. The format of this file is pretty simple, and you can create it with your favorite editor. The contents of the file will look like this:

GroupName: rbowen dpitts sungo rshersey

That’s just a list of the members of the group in a long line separated by spaces.

To add a user to your already existing password file, type:

htpasswd /usr/local/apache/passwd/passwords dpitts

You’ll get the same response as before, but it will be appended to the existing file, rather than creating a new file. (It’s the -c that makes it create a new password file).

Now, you need to modify your .htaccess file or <Directory> block to look like the following:

AuthType Basic
AuthName "By Invitation Only"
# Optional line:
AuthBasicProvider file
AuthUserFile /usr/local/apache/passwd/passwords
AuthGroupFile /usr/local/apache/passwd/groups
Require group GroupName

Now, anyone that is listed in the group GroupName, and has an entry in the password file, will be let in, if they type the correct password.

There’s another way to let multiple users in that is less specific. Rather than creating a group file, you can just use the following directive:

Require valid-user

Using that rather than the Require user rbowen line will allow anyone in that is listed in the password file, and who correctly enters their password.

 


 

Because storing passwords in plain text files has the above problems, you may wish to store your passwords somewhere else, such as in a database.

mod_authn_dbm and mod_authn_dbd are two modules which make this possible. Rather than selecting AuthBasicProvider file, instead you can choose dbm or dbd as your storage format.

To select a dbd file rather than a text file, for example:

<Directory /www/docs/private>
AuthName "Private"
AuthType Basic
AuthBasicProvider dbm
AuthDBMUserFile /www/passwords/passwd.dbm
Require valid-user
</Directory>

Other options are available. Consult the mod_authn_dbm documentation for more details.

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