Authentication and Authorization - Apache HTTP Server Version 2.4








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Apache > HTTP Server > Documentation > Version 2.4 > How-To / TutorialsAuthentication and Authorization

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    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.

    For general access control, see the Access
    Control How-To.

 Related Modules and Directives
 Introduction
 The Prerequisites
 Getting it working
 Letting more than one
person in
 Possible problems
 Alternate password storage
 Using multiple providers
 Beyond just authorization
 Authentication Caching
 More information
See alsoComments


Related Modules and Directives

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.


  Authentication type (see the
      AuthType directive)
    
      mod_auth_basic
      mod_auth_digest
    
  
  Authentication provider (see the
  AuthBasicProvider and
  AuthDigestProvider directives)

    
      mod_authn_anon
      mod_authn_dbd
      mod_authn_dbm
      mod_authn_file
      mod_authnz_ldap
      mod_authn_socache
    
  
  Authorization (see the
      Require directive)
    
      mod_authnz_ldap
      mod_authz_dbd
      mod_authz_dbm
      mod_authz_groupfile
      mod_authz_host
      mod_authz_owner
      mod_authz_user
    
  


  In addition to these modules, there are also
  mod_authn_core and
  mod_authz_core.  These modules implement core
  directives that are core to all auth modules.

  The module mod_authnz_ldap is both an
  authentication and authorization provider.  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. For backwards compatibility with the mod_access, there is
  a new module mod_access_compat.

  You probably also want to take a look at the Access Control howto, which discusses the
  various ways to control access to your server.



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
    those pages are the people that you wanted to see them.

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

    Note:
    If your data really needs to be secure, consider using
    mod_ssl in addition to any authentication.
    


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).

    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.

    Since we're talking here about authentication, you will need
    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
    have write permission to that file.

    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.

    You will also need to make sure that the modules
    mod_authn_core and mod_authz_core
    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.


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

    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/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
    the 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 was intended to be more secure. This is no
    longer the case and the connection should be encrypted with mod_ssl instead.

    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 and htdbm programs. Many
    other types of authentication options are available from third
    party modules.

    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
    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.


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
    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.

    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.


Alternate password storage

    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 dbm 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.


Using multiple providers

    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.

    <Directory "/www/docs/private">
    AuthName "Private"
    AuthType Basic
    AuthBasicProvider file ldap
    AuthUserFile "/usr/local/apache/passwd/passwords"
    AuthLDAPURL ldap://ldaphost/o=yourorg
    Require valid-user
</Directory>


    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.

    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.

    <Directory "/www/docs/private">
    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
</Directory>


    To take authorization a little further, authorization container
    directives such as
    <RequireAll>
    and
    <RequireAny>
    allow logic to be applied so that the order in which authorization
    is handled can be completely controlled through the configuration.
    See Authorization
    Containers for an example of how they may be applied.



Beyond just authorization

    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.

    Applying logic and ordering
        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 Require 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
        Require directives
        appear in the configuration.

        With the introduction of authorization container directives
        such as
        <RequireAll>
        and
        <RequireAny>,
        the configuration also has control over when the
        authorization methods are called and what criteria determines when
        access is granted.  See
        Authorization Containers
        for an example of how they may be used to express complex
        authorization logic.

        By default all
        Require
        directives are handled as though contained within a
        <RequireAny>
        container directive.  In other words, if
        any of the specified authorization methods succeed, then authorization
        is granted.

    

    Using authorization providers for access control
        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 authorization providers all,
        env, host and ip 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.

        The usage of these providers is specified through the
        Require directive.
        This directive registers the authorization providers
        that will be called during the authorization stage of the request
        processing. For example:

        Require ip address
        


        where address is an IP address (or a partial IP
        address) or:

        Require host domain_name
        


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

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

        <RequireAll>
    Require all granted
    Require not ip 10.252.46.165
</RequireAll>


        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.

        <RequireAll>
    Require all granted
    Require not host host.example.com
</RequireAll>


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

        <RequireAll>
    Require all granted
    Require not ip 192.168.205
    Require not host phishers.example.com moreidiots.example
    Require not host ke
</RequireAll>


        Using <RequireAll>
        with multiple <Require> directives, each negated with not,
        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.

    

    Access Control backwards compatibility
        One of the side effects of adopting a provider based mechanism for
        authentication is that the previous access control directives
        Order,
        Allow,
        Deny and
        Satisfy are no longer needed.
        However to provide backwards compatibility for older configurations, these
        directives have been moved to the mod_access_compat module.

        Note
        The directives provided by mod_access_compat have
        been deprecated by mod_authz_host.
        Mixing old directives like Order, Allow or Deny with new ones like
        Require is technically possible
        but discouraged. The mod_access_compat module was created to support
        configurations containing only old directives to facilitate the 2.4 upgrade.
        Please check the upgrading guide for more
        information.
        
        
    



Authentication Caching
    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 mod_authn_dbd (or third-party/custom providers).
    To deal with this, HTTPD 2.3/2.4 introduces a new caching provider
    mod_authn_socache to cache credentials and reduce
    the load on the origin provider(s).
    This may offer a substantial performance boost to some users.


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.  The
    directive <AuthnProviderAlias> can also help
    in simplifying certain authentication configurations.

    The various ciphers supported by Apache for authentication data are
    explained in Password
    Encryptions.

    And you may want to look at the Access
    Control howto, which discusses a number of related topics.



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