Authentication, Authorization and Access Control

Authentication is any process by which you verify that someone is who they claim they are. Authorization is any process by which someone is allowed to be where they want to go, or to have information that they want to have.

- -

Introduction

- +

Related Modules and Directives
Introduction
The Prerequisites
Getting it working
Letting more than one +person in
Possible problems
What other neat stuff can I +do?
More information

Related Modules and Directives

+ +

Related Modules	Related Directives
`mod_auth_basic` `mod_authn_file` `mod_authz_groupfile` `mod_authz_host`	`Allow` `AuthGroupFile` `AuthName` `AuthType` `AuthUserFile` `Deny` `Options` `Require`

Introduction

If you have information on your web site that is sensitive or intended for only a small group of people, the techniques in this article will help you make sure that the people that see @@ -80,28 +47,28 @@

This article covers the "standard" way of protecting parts of your web site that most of you are going to use.

- -

The - prerequisites

- +

The Prerequisites

The directives discussed in this article will need to go either in your main server configuration file (typically in a - <Directory> section), or in per-directory configuration - files (.htaccess files).

+ <Directory> section), or + in per-directory configuration files (.htaccess files).

If you plan to use .htaccess files, you will need to have a server configuration that permits putting authentication directives in these files. This is done with the - AllowOverride - directive, which specifies which directives, if any, may be put - in per-directory configuration files.

+ AllowOverride directive, which + specifies which directives, if any, may be put in per-directory + configuration files.

Since we're talking here about authentication, you will need - an AllowOverride directive like the following:

-    AllowOverride AuthConfig
-

+ an AllowOverride directive like the + following:

+ +

+ AllowOverride AuthConfig +

Or, if you are just going to put the directives directly in your main server configuration file, you will of course need to @@ -111,36 +78,36 @@ structure of your server, in order to know where some files are kept. This should not be terribly difficult, and I'll try to make this clear when we come to that point.

- -

Getting it working

- +

Getting it working

Here's the basics of password protecting a directory on your server.

You'll need to create a 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.

+ 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 +

To create the file, use the htpasswd utility that came with Apache. This be located in the bin directory of wherever you installed Apache. To create the file, type:

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

+ +

+ 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
-

+ +

+ # 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. @@ -155,36 +122,34 @@ /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 + placed in httpd.conf inside a <Directory /usr/local/apache/apache/htdocs/secret> section.

-        AuthType Basic
-        AuthName "Restricted Files"
-        AuthUserFile /usr/local/apache/passwd/passwords
-        require user rbowen
-

- -

Let's examine each of those directives individually. The AuthType directive selects + +

+ AuthType Basic + AuthName "Restricted Files" + 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. It - is important to be aware, however, that Basic authentication - sends the password from the client to the browser unencrypted. - This method should therefore not be used for highly sensitive - data. Apache supports one other authentication method: - AuthType Digest. This method is implemented by mod_auth_digest and is - much more secure. Only the most recent versions of clients are - known to 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 + implemented by mod_auth_basic. It is important to be aware, + however, that Basic authentication sends the password from the client to + the browser unencrypted. This method should therefore not be used for + highly sensitive data. Apache supports one other authentication method: + AuthType Digest. This method is implemented by mod_auth_digest and is much more secure. Only the most recent + versions of clients are known to 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. @@ -194,58 +159,51 @@ will always need to ask again for the password whenever the hostname of the server changes.

The AuthUserFile +

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_auth_dbm module - provides the AuthDBMUserFile - directive. These files can be created and - manipulated with the dbmmanage program. Many + 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 + party modules in the Apache Modules Database.

Finally, the require +

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.

- -

Letting more than one - person in

- + Require directive.

Letting more than one +person in

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.

+ 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
-

+ +

+ 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/password dpitts
-

+ +

+ htpasswd /usr/local/apache/passwd/password dpitts +

You'll get the same response as before, but it will be appended to the existing file, rather than creating a new file. @@ -254,39 +212,39 @@

Now, you need to modify your .htaccess file to look like the following:

-        AuthType Basic
-        AuthName "By Invitation Only"
-        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.

+ +

+ AuthType Basic + AuthName "By Invitation Only" + 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 +

+ 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. You can even emulate the group behavior here, by just keeping a separate password file for each group. The advantage of this approach is that Apache only has to check one file, rather than two. The disadvantage is that you have to maintain a bunch of password - files, and remember to reference th right one in the - AuthUserFile directive.

- -

Possible - problems

- + files, and remember to reference the right one in the + AuthUserFile directive.

Possible problems

Because of the way that Basic authentication is specified, your username and password must be verified every time you request a document from the server. This is even if you're @@ -304,28 +262,30 @@ server machine, but you can expect to see slowdowns once you get above a few hundred entries, and may wish to consider a different authentication method at that time.

- -

What other neat stuff can - I do?

- +

What other neat stuff can I +do?

Authentication by username and password is only part of the story. Frequently you want to let people in based on something other than who they are. Something such as where they are coming from.

The allow and deny directives let +

The Allow and + Deny directives let you allow and deny access based on the host name, or host address, of the machine requesting a document. The - order directive goes hand-in-hand with these two, - and tells Apache in which order to apply the filters.

+ Order directive goes + hand-in-hand with these two, and tells Apache in which order to + apply the filters.

The usage of these directives is:

-        allow from address
-

where address is an IP address (or a partial IP +

+ Allow from address +

+ +

where address is an IP address (or a partial IP address) or a fully qualified domain name (or a partial domain name); you may provide multiple addresses or domain names, if desired.

@@ -333,47 +293,50 @@

For example, if you have someone spamming your message board, and you want to keep them out, you could do the following:

-        deny from 205.252.46.165
-

+ +

+ Deny from 205.252.46.165 +

Visitors coming from that address will not be able to see the content covered by this directive. If, instead, you have a machine name, rather than an IP address, you can use that.

-        deny from host.example.com
-

+ +

+ Deny from host.example.com +

And, if you'd like to block access from an entire domain, you can specify just part of an address or domain name:

-        deny from 192.101.205
-        deny from cyberthugs.com moreidiots.com
-        deny from ke
-

- -

Using order will let you be sure that you are - actually restricting things to the group that you want to let - in, by combining a deny and an allow - directive:

-        order deny,allow
-        deny from all
-        allow from dev.example.com
-

- -

Listing just the allow directive would not do - what you want, because it will let folks from that host in, in - addition to letting everyone in. What you want is to let - only those folks in.

More - information

- -

You should also read the documentation for mod_auth and mod_access which +

+ Deny from 192.101.205 + Deny from cyberthugs.com moreidiots.com + Deny from ke +

+ +

Using Order will let you + be sure that you are actually restricting things to the group that you want + to let in, by combining a Deny and an Allow directive:

+ +

+ Order deny,allow + Deny from all + Allow from dev.example.com +

+ +

Listing just the Allow + directive would not do what you want, because it will let folks from that + host in, in addition to letting everyone in. What you want is to let + only those folks in.

More information

You should also read the documentation for + mod_auth_basic and mod_authz_host which contain some more information about how this all works.

- - - +