<?xml version='1.0' encoding='UTF-8' ?>

<!DOCTYPE manualpage SYSTEM "/style/manualpage.dtd">

<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>

<manualpage metafile="auth.xml.meta">

<parentdocument href="./">How-To / Tutorials</parentdocument>

<title>Authentication and Authorization</title>

<summary>

<p>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.</p>

<p>For general access control, see the <a href="access.html">Access

Control How-To</a>.</p>

</summary>

<section id="related"><title>Related Modules and Directives</title>

<p>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.</p>

<ul>

<li>Authentication type (see the

<directive module="mod_authn_core">AuthType</directive> directive)

<ul>

<li><module>mod_auth_basic</module></li>

<li><module>mod_auth_digest</module></li>

</ul>

</li>

<li>Authentication provider (see the

<directive module="mod_auth_basic">AuthBasicProvider</directive> and

<directive module="mod_auth_digest">AuthDigestProvider</directive> directives)

<ul>

<li><module>mod_authn_anon</module></li>

<li><module>mod_authn_dbd</module></li>

<li><module>mod_authn_dbm</module></li>

<li><module>mod_authn_file</module></li>

<li><module>mod_authnz_ldap</module></li>

<li><module>mod_authn_socache</module></li>

</ul>

</li>

<li>Authorization (see the

<directive module="mod_authz_core">Require</directive> directive)

<ul>

<li><module>mod_authnz_ldap</module></li>

<li><module>mod_authz_dbd</module></li>

<li><module>mod_authz_dbm</module></li>

<li><module>mod_authz_groupfile</module></li>

<li><module>mod_authz_host</module></li>

<li><module>mod_authz_owner</module></li>

<li><module>mod_authz_user</module></li>

</ul>

</li>

</ul>

<p>In addition to these modules, there are also

<module>mod_authn_core</module> and

<module>mod_authz_core</module>. These modules implement core

directives that are core to all auth modules.</p>

<p>The module <module>mod_authnz_ldap</module> is both an

authentication and authorization provider. The module

<module>mod_authz_host</module> provides authorization

and access control based on hostname, IP address or characteristics

of the request, but is not part of the authentication provider

system. For backwards compatibility with the mod_access, there is

a new module <module>mod_access_compat</module>.</p>

<p>You probably also want to take a look at the <a

href="access.html">Access Control</a> howto, which discusses the

various ways to control access to your server.</p>

</section>

<section id="introduction"><title>Introduction</title>

<p>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

those pages are the people that you wanted to see them.</p>

<p>This article covers the "standard" way of protecting parts

of your web site that most of you are going to use.</p>

<note><title>Note:</title>

<p>If your data really needs to be secure, consider using

<module>mod_ssl</module> in addition to any authentication.</p>

</note>

</section>

<section id="theprerequisites"><title>The Prerequisites</title>

<p>The directives discussed in this article will need to go

either in your main server configuration file (typically in a

<directive module="core" type="section">Directory</directive> section), or

in per-directory configuration files (<code>.htaccess</code> files).</p>

<p>If you plan to use <code>.htaccess</code> files, you will

need to have a server configuration that permits putting

authentication directives in these files. This is done with the

<directive module="core">AllowOverride</directive> directive, which

specifies which directives, if any, may be put in per-directory

configuration files.</p>

<p>Since we're talking here about authentication, you will need

an <directive module="core">AllowOverride</directive> directive like the

following:</p>

<highlight language="config">

AllowOverride AuthConfig

</highlight>

<p>Or, if you are just going to put the directives directly in

your main server configuration file, you will of course need to

have write permission to that file.</p>

<p>And you'll need to know a little bit about the directory

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.</p>

<p>You will also need to make sure that the modules

<module>mod_authn_core</module> and <module>mod_authz_core</module>

have either been built into the httpd binary or loaded by the

httpd.conf configuration file. Both of these modules provide core

directives and functionality that are critical to the configuration

and use of authentication and authorization in the web server.</p>

</section>

<section id="gettingitworking"><title>Getting it working</title>

<p>Here's the basics of password protecting a directory on your

server.</p>

<p>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.</p>

<p>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 <code>/usr/local/apache/htdocs</code>, you

might want to put the password file(s) in

<code>/usr/local/apache/passwd</code>.</p>

<p>To create the file, use the <program>htpasswd</program> utility that

came with Apache. This will be located in the <code>bin</code> directory

of wherever you installed Apache. If you have installed Apache from

a third-party package, it may be in your execution path.</p>

<p>To create the file, type:</p>

<example>

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

</example>

<p><program>htpasswd</program> will ask you for the password, and

then ask you to type it again to confirm it:</p>

<example>

# htpasswd -c /usr/local/apache/passwd/passwords rbowen<br />

New password: mypassword<br />

Re-type new password: mypassword<br />

Adding password for user rbowen

</example>

<p>If <program>htpasswd</program> 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

<code>/usr/local/apache2/bin/htpasswd</code></p>

<p>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 <code>httpd.conf</code>

file or using an <code>.htaccess</code> file. For example, if

you wish to protect the directory

<code>/usr/local/apache/htdocs/secret</code>, you can use the

following directives, either placed in the file

<code>/usr/local/apache/htdocs/secret/.htaccess</code>, or

placed in <code>httpd.conf</code> inside a &lt;Directory

"/usr/local/apache/htdocs/secret"&gt; section.</p>

<highlight language="config">

AuthType Basic

AuthName "Restricted Files"

# (Following line optional)

AuthBasicProvider file

AuthUserFile "/usr/local/apache/passwd/passwords"

Require user rbowen

</highlight>

<p>Let's examine each of those directives individually. The <directive

module="mod_authn_core">AuthType</directive> directive selects

that method that is used to authenticate the user. The most

common method is <code>Basic</code>, and this is the method

implemented by <module>mod_auth_basic</module>. 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 <module>mod_ssl</module>.

Apache supports one other authentication method:

<code>AuthType Digest</code>. This method is implemented by <module

>mod_auth_digest</module> and was intended to be more secure. This is no

longer the case and the connection should be encrypted with <module

>mod_ssl</module> instead.</p>

<p>The <directive module="mod_authn_core">AuthName</directive> directive sets

the <dfn>Realm</dfn> 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.</p>

<p>So, for example, once a client has authenticated in the

<code>"Restricted Files"</code> area, it will automatically

retry the same password for any area on the same server that is

marked with the <code>"Restricted Files"</code> 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.</p>

<p>The <directive

module="mod_auth_basic">AuthBasicProvider</directive> is,

in this case, optional, since <code>file</code> 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

<module>mod_authn_dbm</module> or <module>mod_authn_dbd</module>.</p>

<p>The <directive module="mod_authn_file">AuthUserFile</directive>

directive sets the path to the password file that we just

created with <program>htpasswd</program>. 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 <module>mod_authn_dbm</module> module provides the <directive

module="mod_authn_dbm">AuthDBMUserFile</directive> directive. These

files can be created and manipulated with the <program>

dbmmanage</program> and <program>htdbm</program> programs. Many

other types of authentication options are available from third

party modules in the <a

href="http://modules.apache.org/">Apache Modules

Database</a>.</p>

<p>Finally, the <directive module="mod_authz_core">Require</directive>

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

<directive module="mod_authz_core">Require</directive> directive.</p>

</section>

<section id="lettingmorethanonepersonin"><title>Letting more than one

person in</title>

<p>The directives above only let one person (specifically

someone with a username of <code>rbowen</code>) into the

directory. In most cases, you'll want to let more than one

person in. This is where the <directive module="mod_authz_groupfile"

>AuthGroupFile</directive> comes in.</p>

<p>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:</p>

<example>

GroupName: rbowen dpitts sungo rshersey

</example>

<p>That's just a list of the members of the group in a long

line separated by spaces.</p>

<p>To add a user to your already existing password file,

type:</p>

<example>

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

</example>

<p>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 <code>-c</code> that makes it create a new password

file).</p>

<p>Now, you need to modify your <code>.htaccess</code> file to

look like the following:</p>

<highlight language="config">

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

</highlight>

<p>Now, anyone that is listed in the group <code>GroupName</code>,

and has an entry in the <code>password</code> file, will be let in, if

they type the correct password.</p>

<p>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:</p>

<highlight language="config">

Require valid-user

</highlight>

<p>Using that rather than the <code>Require user rbowen</code>

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 the right one in the

<directive module="mod_authn_file">AuthUserFile</directive> directive.</p>

</section>

<section id="possibleproblems"><title>Possible problems</title>

<p>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

reloading the same page, and for every image on the page (if

they come from a protected directory). As you can imagine, this

slows things down a little. The amount that it slows things

down is proportional to the size of the password file, because

it has to open up that file, and go down the list of users

until it gets to your name. And it has to do this every time a

page is loaded.</p>

<p>A consequence of this is that there's a practical limit to

how many users you can put in one password file. This limit

will vary depending on the performance of your particular

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.</p>

</section>

<section id="dbmdbd"><title>Alternate password storage</title>

<p>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.</p>

<p><module>mod_authn_dbm</module> and <module>mod_authn_dbd</module> are two

modules which make this possible. Rather than selecting <code><directive

module="mod_auth_basic">AuthBasicProvider</directive> file</code>, instead

you can choose <code>dbm</code> or <code>dbd</code> as your storage

format.</p>

<p>To select a dbm file rather than a text file, for example:</p>

<highlight language="config">

&lt;Directory "/www/docs/private"&gt;

AuthName "Private"

AuthType Basic

AuthBasicProvider dbm

AuthDBMUserFile "/www/passwords/passwd.dbm"

Require valid-user

&lt;/Directory&gt;

</highlight>

<p>Other options are available. Consult the

<module>mod_authn_dbm</module> documentation for more details.</p>

</section>

<section id="multprovider"><title>Using multiple providers</title>

<p>With the introduction of the new provider based authentication and

authorization architecture, you are no longer locked into a single

authentication or authorization method. In fact any number of the

providers can be mixed and matched to provide you with exactly the

scheme that meets your needs. In the following example, both the

file and LDAP based authentication providers are being used.</p>

<highlight language="config">

&lt;Directory "/www/docs/private"&gt;

AuthName "Private"

AuthType Basic

AuthBasicProvider file ldap

AuthUserFile "/usr/local/apache/passwd/passwords"

AuthLDAPURL ldap://ldaphost/o=yourorg

Require valid-user

&lt;/Directory&gt;

</highlight>

<p>In this example the file provider will attempt to authenticate

the user first. If it is unable to authenticate the user, the LDAP

provider will be called. This allows the scope of authentication

to be broadened if your organization implements more than

one type of authentication store. Other authentication and authorization

scenarios may include mixing one type of authentication with a

different type of authorization. For example, authenticating against

a password file yet authorizing against an LDAP directory.</p>

<p>Just as multiple authentication providers can be implemented, multiple

authorization methods can also be used. In this example both file group

authorization as well as LDAP group authorization is being used.</p>

<highlight language="config">

&lt;Directory "/www/docs/private"&gt;

AuthName "Private"

AuthType Basic

AuthBasicProvider file

AuthUserFile "/usr/local/apache/passwd/passwords"

AuthLDAPURL ldap://ldaphost/o=yourorg

AuthGroupFile "/usr/local/apache/passwd/groups"

Require group GroupName

Require ldap-group cn=mygroup,o=yourorg

&lt;/Directory&gt;

</highlight>

<p>To take authorization a little further, authorization container

directives such as

<directive module="mod_authz_core" type="section">RequireAll</directive>

and

<directive module="mod_authz_core" type="section">RequireAny</directive>

allow logic to be applied so that the order in which authorization

is handled can be completely controlled through the configuration.

See <a href="/mod/mod_authz_core.html#logic">Authorization

Containers</a> for an example of how they may be applied.</p>

</section>

<section id="beyond"><title>Beyond just authorization</title>

<p>The way that authorization can be applied is now much more flexible

than just a single check against a single data store. Ordering, logic

and choosing how authorization will be done is now possible.</p>

<section id="authandororder"><title>Applying logic and ordering</title>

<p>Controlling how and in what order authorization will be applied

has been a bit of a mystery in the past. In Apache 2.2 a provider-based

authentication mechanism was introduced to decouple the actual

authentication process from authorization and supporting functionality.

One of the side benefits was that authentication providers could be

configured and called in a specific order which didn't depend on the

load order of the auth module itself. This same provider based mechanism

has been brought forward into authorization as well. What this means is

that the <directive module="mod_authz_core">Require</directive> directive

not only specifies which authorization methods should be used, it also

specifies the order in which they are called. Multiple authorization

methods are called in the same order in which the

<directive module="mod_authz_core">Require</directive> directives

appear in the configuration.</p>

<p>With the introduction of authorization container directives

such as

<directive module="mod_authz_core" type="section">RequireAll</directive>

and

<directive module="mod_authz_core" type="section">RequireAny</directive>,

the configuration also has control over when the

authorization methods are called and what criteria determines when

access is granted. See

<a href="/mod/mod_authz_core.html#logic">Authorization Containers</a>

for an example of how they may be used to express complex

authorization logic.</p>

<p>By default all

<directive module="mod_authz_core">Require</directive>

directives are handled as though contained within a

<directive module="mod_authz_core" type="section">RequireAny</directive>

container directive. In other words, if

any of the specified authorization methods succeed, then authorization

is granted.</p>

</section>

<section id="reqaccessctrl"><title>Using authorization providers for access control</title>

<p>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.</p>

<p>The authorization providers <code>all</code>,

<code>env</code>, <code>host</code> and <code>ip</code> let you

allow or deny access based on other host based criteria such as

host name or ip address of the machine requesting a

document.</p>

<p>The usage of these providers is specified through the

<directive module="mod_authz_core">Require</directive> directive.

This directive registers the authorization providers

that will be called during the authorization stage of the request

processing. For example:</p>

<highlight language="config">

Require ip <var>address</var>

</highlight>

<p>where <var>address</var> is an IP address (or a partial IP

address) or:</p>

<highlight language="config">

Require host <var>domain_name</var>

</highlight>

<p>where <var>domain_name</var> is a fully qualified domain name

(or a partial domain name); you may provide multiple addresses or

domain names, if desired.</p>

<p>For example, if you have someone spamming your message

board, and you want to keep them out, you could do the

following:</p>

<highlight language="config">

&lt;RequireAll&gt;

Require all granted

Require not ip 10.252.46.165

&lt;/RequireAll&gt;

</highlight>

<p>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.</p>

<highlight language="config">

&lt;RequireAll&gt;

Require all granted

Require not host host.example.com

&lt;/RequireAll&gt;

</highlight>

<p>And, if you'd like to block access from an entire domain,

you can specify just part of an address or domain name:</p>

<highlight language="config">

&lt;RequireAll&gt;

Require all granted

Require not ip 192.168.205

Require not host phishers.example.com moreidiots.example

Require not host ke

&lt;/RequireAll&gt;

</highlight>

<p>Using <directive module="mod_authz_core" type="section">RequireAll</directive>

with multiple <directive module="mod_authz_core"

type="section">Require</directive> directives, each negated with <code>not</code>,

will only allow access, if all of negated conditions are true. In other words,

access will be blocked, if any of the negated conditions fails.</p>

</section>

<section id="filesystem"><title>Access Control backwards compatibility</title>

<p>One of the side effects of adopting a provider based mechanism for

authentication is that the previous access control directives

<directive module="mod_access_compat">Order</directive>,

<directive module="mod_access_compat">Allow</directive>,

<directive module="mod_access_compat">Deny</directive> and

<directive module="mod_access_compat">Satisfy</directive> are no longer needed.

However to provide backwards compatibility for older configurations, these

directives have been moved to the <module>mod_access_compat</module> module.</p>

</section>

</section>

<section id="socache"><title>Authentication Caching</title>

<p>There may be times when authentication puts an unacceptable load

on a provider or on your network. This is most likely to affect users

of <module>mod_authn_dbd</module> (or third-party/custom providers).

To deal with this, HTTPD 2.3/2.4 introduces a new caching provider

<module>mod_authn_socache</module> to cache credentials and reduce

the load on the origin provider(s).</p>

<p>This may offer a substantial performance boost to some users.</p>

</section>

<section id="moreinformation"><title>More information</title>

<p>You should also read the documentation for

<module>mod_auth_basic</module> and <module>mod_authz_host</module>

which contain some more information about how this all works. The

directive <directive type="section"

module="mod_authn_core">AuthnProviderAlias</directive> can also help

in simplifying certain authentication configurations.</p>

<p>The various ciphers supported by Apache for authentication data are

explained in <a href="/misc/password_encryptions.html">Password

Encryptions</a>.</p>

<p>And you may want to look at the <a href="access.html">Access

Control</a> howto, which discusses a number of related topics.</p>

</section>

</manualpage>