What is “Auth MemCookie”?

Auth MemCookie is an Apache v2 Authentication and authorization modules are based on cookie Authentication mechanism.

The module doesn’t make Authentication by it self, but verify if Authentication the cookie is valid for each url protected by the module. The module validate also if the authenticated user have authorization to access url.

Authentication is made externally by an Authentication html form page and all Authentication information necessary to the module a stored in memcached identified by the cookie value Authentication session id by this login page.

How it Works

Phase 1 : The login Form

Authentication is made by a login form page.

This login page must authenticate the user with any authenticate source (ldap, /etc/password, file, database….) accessible to language of the page (php, perl, java… an ldap login page sample in php are in samples directory).

Then this page must set cookie that contains only a key the Authentication unique id of the Authentication session.

The login page must store authorization and user information of the authenticated user in memcached identified by the cookie key Authentication unique id.

The login page can be developed in any language you want, but must be capable to use memcached (they must have memcache client api for us)

Phase 2 : The Apache v2 Module

After the user is logged, the Auth MemCookie module check on each protected page by apache ACL is the user is authenticated.

When authenticating a request Auth MemCookie module walks through the following steps:

1. Get the session id. The session id is stored in a cookie (by default named AuthMemCookie).

2. Get the session data. Auth MemCookie module fetches session data by looking up the session id on the memcached server.

3. Verify the remote ip. Auth MemCookie module checks the ip address stored in the session data against the ip address of the current request. This step is optional, and can be disabled by setting the Auth_memCookie_MatchIP option to no.

4. Get username and groups from session data. The username is stored in the UserName field in the session data and the groups the user is a member of is stored in the Groups field.

5. Check username and groups against Require configuration directives.

If any of the steps 1-4 fails, then Auth MemCookie will return a HTTP_UNAUTHORIZED (401) Authorization Required error. A HTTP_FORBIDDEN (403) Forbidden error will be returned if the last step fails.

When a user is successfully authenticated, Auth MemCookie will store all the fields from the session data in environment variables accessible to the web page. Every field of the session data will be send http header MCAC_<field-name> to the value of the field.

“Session data” format stored in memcached

The session data stored in memcached are composed with multiple line in form of name equal value ended by \r\n. some are mandatory, other are optional and the rest are information only (all this field are transmitted to the script language protect the module).

Session data format:

UserName=<user name>\r\n Groups=<group name1>:<group name2>:...\r\n RemoteIP=<remote ip>\r\n Password=<password>\r\n Expiration=<expiration time>\r\n Email=<email>\r\n Name=<name>\r\n GivenName=<given name>\r\n 

• Username: are mandatory.
• Groups: are mandatory, are used to check group in apache acl. if no group are know for the user, must be blank (Groups=\r\n)
• RemoteIP: are mandatory, used by remote ip check function in apache module.
• Password: are not mandatory, and is not recommended to store in memcached for security reson, but if stored, is sent to the script language protected by the module.
• The other fields are information only, but they are sent to the langage that are behind the module (via environement variable or http header).

The session field size is for the moment limited to 10 fields by default.

Build dependency

You must have compiled and installed:

• Apache HTTPD Apache HTTPD server (Requires v2.0+).

• libevent use by memcached.

• memcached the cache daemon it self.

• libmemcached the C client API needed to compile the Apache Module (require v1.0+).

• autoconf the gnu autotool to rebuild configure script from autoconf.ac and m4 files.

Compilation

# autoconf -f # ./configure --with-apxs=/path/to/apache/httpd/bin/apxs --with-libmemcached=/path/to/libmemcached_install_dir/ # make # make install 

• where –with-libmemcached is the installation directory of libmemcached (require v1.0+) library.

  Generaly with libmemcached os package you need simply to specify –with-libmemcached=/usr. They require generaly to install libmemcached developper package.

  • debian version wheezy, jessie, stretch, buster, sid have v1.0 packaged.
  • centos/rhel you need v7 to have libmemcached v1.0 packaged
  • fedora v25+ have v1.0 packaged
  • ubuntu trusty, xenial, yakkety, zesty, artful have v1.0 packaged.

• where –with-apxs= is the path of apache apxs2 build script (require apache v2.0+).

  Generaly with apache httpd os package you simply need to specify –with-apxs=/usr/bin/apxs or –with-apxs=/usr/sbin/apxs (the default path depend on the distribution, you can find it with type apxs shell command). They require generaly to install apache developper package.

After that the mod_auth_memcookie.so is generated in apache modules installation directory.

How to configure Apache Module

Module configuration option:

This option can be used in location or directory apache context.

• Auth_memCookie_Memcached_Configuration

  This configuration directive permit to configure libmemcached initialisation. The syntax of this directive value are defined her: http://docs.libmemcached.org/libmemcached_configuration.html

  With that directive you can specify a liste of ip or host adresse(s) and port : separed of memcache(s) daemon to be used.

  For exemple:

   Auth_memCookie_Memcached_Configuration "--SERVER=host10.example.com:port1 --SERVER=host11.example.com:port2 --SERVER=host10.example.com:port3" 

  To use consistant distribution of hash on multiple memcached server add --DISTRIBUTION=consistent and for replication --NUMBER-OF-REPLICAS=2. But your login page must use the same algorithm than libmemcached library that by default use the ketama distribution algorithm with md5 hash.

  For example with php you can use PECL Memcached extension that are also based on libmemcached library that support the same consistant distribution algorithm before add server list.

  Sample:

   $memcached=new Memcached(); $memcached->setOption( Memcached::OPT_DISTRIBUTION,Memcached::DISTRIBUTION_CONSISTENT); 

• Auth_memCookie_Memcached_SessionObject_ExpireTime

  Session object stored in memcached expiry time, in secondes.

  Used only if Auth_memCookie_Memcached_SessionObject_ExpiryReset is set to on.

  Set to 3600 seconds by default.

• Auth_memCookie_Memcached_SessionObject_ExpiryReset

  Set to off to not reset object expiry time in memcache on each url, is set to on by default.

  By default on each request authenticated by the module, the object expiry in memcached of the session data are reset to make expiry base on inactivity, if set to off the expiry are based on session time length.

• Auth_memCookie_SessionTableSize

  Max number of element in session information table, is set to 10 by default.

• Auth_memCookie_SetSessionHTTPHeader

  Set to on to set session information to http header of the authenticated users, is set to off by default. Each session field are sended to backend. Each session field name are prefixed by Auth_memCookie_SetSessionHTTPHeaderPrefix changed to uppercase.

• Auth_memCookie_SetSessionHTTPHeaderEncode

  Set to on to mime64 encode session information to http header, is set to off by default.

• Auth_memCookie_SetSessionHTTPHeaderPrefix

  Set HTTP header prefix, is set to MCAC_ by default.

• Auth_memCookie_CookieName

  Name of the cookie to used for check authentification, is set to AuthMemCookie by default.

• Auth_memCookie_MatchIP_Mode

  To check cookie ip adresse, Set to 1 to use X-Forwarded-For http header, to 2 to use Via http header, and to 3 to use apache remote_ip, is set to 0 by default to desactivate the ip check.

• Auth_memCookie_GroupAuthoritative (only on apache <2.4)

  Set to off to allow access control to be passed along to lower modules, for group acl check, is set to on by default.

• Auth_memCookie_Authoritative

  Set to off to allow access control to be passed along to lower modules, is set to on by default.

• Auth_memCookie_SilmulateAuthBasic

  Set to off to not fix http header and auth_type for simulating auth basic for scripting language like php authentication framework work, is set to on by default.

  with this option this $_SERVER variable are normaly set on php:

   AUTH_TYPE = "basic" PHP_AUTH_USER = "user" PHP_AUTH_PW = "password" 

• Auth_memCookie_DisableNoStore

  Set to on to stop the sending of a Cache-Control header set to no-store with the login screen. This allows the browser to cache the credentials, but at the risk of it being possible for the login form to be resubmitted and revealed to the backend server through XSS. Use at own risk.

• Auth_memCookie_SASLAuth

  Set to on to enable SASL authentication. If this is set, Auth_memCookie_SASLUsername and Auth_memcookie_SASLPassword should also be set. Defaults to off.

• Auth_memCookie_SASLUsername

  Username to use when authenticating to memcached if Auth_memCookie_SASLAuth is on. Defaults to user.

• Auth_memCookie_SASLPassword

  Password to use when authenticating to memcached if Auth_memCookie_SASLAuth is on. Defaults to pass.

On the backend application

The application recieve this information:

• REMOTE_USER are set to the user logged name
• AUTHMEMCOOKIE_PREFIX are set to value of Auth_memCookie_SetSessionHTTPHeaderPrefix
• AUTHMEMCOOKIE_AUTH are set to yes when protected, no when in public zone.

And all session field (prefixed by Auth_memCookie_SetSessionHTTPHeaderPrefix/AUTHMEMCOOKIE_PREFIX) if Auth_memCookie_SetSessionHTTPHeader is on.

And if Auth_memCookie_SilmulateAuthBasic is set, they recieve also this $_SERVER variable :

 AUTH_TYPE = "basic" PHP_AUTH_USER = "user" PHP_AUTH_PW = "password" 

Apache 2.3/2.4 authn/authz model

The module add some Require/authz provider:

• Require mcac-group

  To limit access to groups specified in session (groups session field) by the login script. Use the same syntax than Require group. But Require group on apache 2.3/2.4 work only with mod_authz_groupfile.

  They also support multiple groups like that:

   Require mcac-group group1 group2 group3 

  If one match on group of the groups session field they are granted.

• Require mcac-public

  They make possible to specify public access zone.

  In that zone authenticated or not are granted but authenticated can send session information to backend depend on Auth_memCookie_SetSessionHTTPHeader flag.

   <Location /publiczone> Require mcac-public </Location> 

• Require valid-user and Require user

  All the two a provided by mod_authz_user core apache module.

Sample to configure Apache v2.4 Module:

Configuration sample for using Auth_memcookie apache V2.4 module:

LoadModule mod_auth_memcookie_module modules/mod_auth_memcookie.so <IfModule mod_auth_memcookie.c> <Location /> Auth_memCookie_CookieName myauthcookie Auth_memCookie_Memcached_Configuration --SERVER=127.0.0.1:11000 # to redirect unauthorized user to the login page ErrorDocument 401 "/gestionuser/login.php" # to specify if the module are autoritative in this directory Auth_memCookie_Authoritative on # must be set without that the refuse authentification AuthType Cookie # must be set (apache mandatory) but not used by the module AuthName "My Login" require mcac-public </Location> </IfModule> # to protect juste user authentification <Location "/myprotectedurl"> require valid-user </Location> # to protect acces to user in group1 <Location "/myprotectedurlgroup1"> require mcac-group group1 </Location> 

Apache 2.0/2.2 authn/authz model

• Require group groupname [groupname]…

  Only users with the specified groups can access the resource.

• Require valid-user

  Any valid user can access the resource.

• Require user user_id [user_id]…

  Only specified users can access the resource.

  all this directive are from mod_auth_basic module.

Sample to configure Apache v2.0 Module:

Configuration sample for using Auth_memcookie apache V2.0 module:

LoadModule mod_auth_memcookie_module modules/mod_auth_memcookie.so <IfModule mod_auth_memcookie.c> <Location /> Auth_memCookie_CookieName myauthcookie Auth_memCookie_Memcached_Configuration --SERVER=127.0.0.1:11000 # to redirect unauthorized user to the login page ErrorDocument 401 "/gestionuser/login.php" # to specify if the module are autoritative in this directory Auth_memCookie_Authoritative on # must be set without that the refuse authentification AuthType Cookie # must be set (apache mandatory) but not used by the module AuthName "My Login" </Location> </IfModule> # to protect juste user authentification <Location "/myprotectedurl"> require valid-user </Location> # to protect acces to user in group1 <Location "/myprotectedurlgroup1"> require group group1 </Location> 

Releases notes

News in v2.0

• Full support for apache 2.3/2.4 authz/authn model support
• Fix HTTP header not sending to backend
• Add support for setting prefix HTTP header other than "MCAC_"
• Add public zone support (Require mcac-public only in apache 2.3/2.4)
• HTTP header name sended to backend in uppercase

News in v1.2

• Migration from old libmemcache (Sean Chittenden) to modern libmemcached (Brian Aker)

News in v1.1.1

• Correct handling of “=” in value of the memcache session (E. Dumas).
• Don’t breaks basic authentication (Steve Gaarder)
• Multi users/groups require support
• Fix memory leak when mc_aget2 return NULL
• Apache 2.4 partial support (no use the new security model)
• Fix somme portability issue (apr_strtok in place of strtok, and variable definition in front of function)