Skip to content


Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Local fork of the official mod_auth_cas SVN repository
Shell C
branch: master

This branch is 2 commits ahead of acdha:master

Fetching latest commit…

Cannot retrieve the latest commit at this time

Failed to load latest commit information.


Apache CAS Authentication Module

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   See the License for the specific language governing permissions and
   limitations under the License.

The purpose of this module is to allow an Apache web server to interact
with an authentication server that conforms to the CAS version 1 or 2
protocol as specified by Yale/JA-SIG.  At the time of this writing, the CAS
protocol specification is here:

* mod_auth_cas 1.0.9 is now licensed under the Apache 2 License.
  All future versions will be released under this license until
  further notice.

* mod_auth_cas 1.0.8 and prior should be considered as available
  under the Apache 2 License or the GPLv3 license.

* Included a patch by Chris Adams of Yale University to prevent
  segfaults when parsing a corrupted XML cache file.

These limitations are known to exists in this release of the software:

* CAS Proxy Validation is not implemented in this version.

* CAS Ticket Validation can only be performed over an SSL connection.
  The CAS protocol does not explicitly require this, but to not do so
  leaves this system open to a man-in-the-middle attack.

* CAS single sign out is currently not functional and disabled.  It
  is only safe to use in the case where all requests are GET and not
  POST (the module inadvertently 'eats' some content of the POST
  request while determining if it should process it as a SAML logout

* Reports of slow performance on some systems (particularly
  virtual machines) have been reported.  This is related to the
  entropy that is gathered when creating a session cookie for
  the end user.  To combat this, there are 3 solutions.  The
  first is to upgrade the version of the Apache Portable Runtime
  on your system to >= 1.3.0.  In that version, entropy is gathered
  from a nonblocking source.  The second method would be to install
  a package such as rng-tools and feed random data from /dev/urandom
  to /dev/random("-r /dev/urandom").  The  last way is to reduce
  the size of the CASCookieEntropy setting, reducing the demand on
  the pool.


The module was built and tested on the following libraries/versions:

OpenSSL - 0.9.8c
Apache Portable Runtime - 1.2.8
Apache Portable Runtime Utilities - 1.2.7
Apache Web Server - 2.2.3

Additionally, GNU Make and the auto* tools are necessary for building

Compatibility with other versions will depend on those other libraries.

Ensure that the follow files are in the working directory:

Use the APache eXtenSion tool (APXS) to compile and install this 
object as a dynamically shared object (DSO), by either:

apxs -i -c mod_auth_cas.c
apxs2 -i -c mod_auth_cas.c

depending on your Linux distribution.

This release of mod_auth_cas includes support for autoconf.  Note that
you must use GNU Make - other Make implementations may work, but are
untested and not recommended.  Use the standard commands below to
compile and install:

./configure; make; make install

configure can take an optional --with-apxs=/path/to/apxs argument to
specify the path to your APXS binary.

First, you must tell Apache to load the module.  In your httpd.conf,

LoadModule auth_cas_module /path/to/

Then, in the location(s) you want to protect, use the following

AuthType CAS

Be sure to set authorization parameters in the locations you
are protecting(e.g. 'require valid-user', 'require group foo')

The following are valid configuration options and their default:

Valid Server/VirtualHost Directives
Directive: 	CASVersion
Default:	2
Description:	The version of the CAS protocol to adhere to (1 or 2).
		This affects whether Gateway mode is available and how
		the CAS validation response is parsed.

Directive: 	CASDebug
Default:	Off
Description:	Enable or disable debugging mode for troubleshooting.

Directive: 	CASValidateServer
Default:	On
Description:	If set to 'On', mod_auth_cas will validate that the certificate
		presented by the server specified in CASLoginURL is both
		signed by the Certificate Authority specified in CASCertificatePath
		and that the hostname matches the Common Name of the certificate.

Directive:	CASValidateDepth
Default:	9
Description:	This directive will set the maximum depth for chained certificate
		validation.  The default (according to OpenSSL documentation) is 9.

Directive:	CASAllowWildcardCert
Default:	Off
Description:	This directive determines whether a wildcard certificate can be trusted
		to verify the CAS server.  For instance, if the CAS server presents a
		certificate for * and the hostname portion of the CASValidateURL
		is '', this directive (if enabled) will accept that

Directive: 	CASCertificatePath
Default:	/etc/ssl/certs/
Description:	The path to the X509 certificate of the Certificate Authority for
		the server in CASLoginURL and CASValidateURL.  This may be either
		a file, or a directory containing the certificate files linked to
		by their hashed names.

Directive: 	CASLoginURL
Default:	NULL
Description:	The URL to redirect users to when they attempt to access a CAS
		protected resource and do not have an existing session.  The
		'service', 'renew', and 'gateway' parameters will be appended to
		this by mod_auth_cas if necessary.  Include 'http[s]://...'

Directive: 	CASValidateURL
Default:	NULL
Description:	The URL to use when validating a ticket presented by a client in
		the HTTP query string (ticket=...).  Must include 'https://' and
		must be an HTTPS URL.

Directive: 	CASProxyValidateURL
Default:	NULL
Description:	The URL to use when performing a proxy validation.  This is currently
		an unimplemented feature, so setting this will have no effect.

Directive: 	CASCookiePath
Default:	/dev/null
Description:	When users first authenticate to mod_auth_cas with a valid service ticket,
		a local session is established.  Information about this session (the
		username, time of creation, last activity time, the resource initially
		requested, and whether or not the credentials were renewed) is stored
		in this directory.  This location should be writable by the web server ONLY.
		Any user that can write to this location can falsify authentication information
		by creating a fake data file.
		NOTE : Some distributions purge the contents of /tmp/ on a reboot, including
		user created directories.  This will prevent mod_auth_cas from storing
		cookie information until that directory is created.  To avoid this, try
		using a different location, such as /var/cache/apache2/mod_auth_cas/

Directive: 	CASCookieEntropy
Default:	32
Description:	When creating a local session, this many random bytes are used to
		create a unique session identifier.  Using large values for this
		field may result in delays when generating session IDs if not
		enough entropy is available.

Directive: 	CASTimeout
Default:	7200 (2 hours)
Description:	This is the hard limit, in seconds, for a mod_auth_cas session (whether
		it is idle or not).  When a session has reached this age and a new
		request is made, the user is redirected to the CASLoginURL to
		obtain a new service ticket.  When this new ticket is validated,
		they will be assigned a new mod_auth_cas session.

Directive: 	CASIdleTimeout
Default:	3600 (1 hour)
Description:	This is a limit, in seconds, of how long a mod_auth_cas session can be idle.
		When a request comes in, if it has been inactive for CASIdleTimeout
		seconds, the user is redirected to the CASLoginURL to obtain a new
		service ticket.

Directive: 	CASCacheCleanInterval
Default:	1800 (30 minutes)
Description:	This is the minimum amount of time that must pass inbetween cache
		cleanings.  When a new ticket is issued, or when an expired session
		is presented, the time of the last cache clean is compared against
		this value.  If CASCacheCleanInterval seconds have passed since the
		last cleaning, then all files in CASCookiePath are examined and if
		they have expired, they are removed.  This is merely to prevent the
		file system from becoming excessively cluttered.

Directive:	CASCookieDomain
Default:	NULL
Description:	Specify the value for the 'Domain=' parameter in the Set-Cookie header.

Directive:	CASCookieHttpOnly
Default:	Off
Description:	Set the optional 'HttpOnly' flag for cookies issues by mod_auth_cas.
		This parameter may break RFC compliance since HttpOnly is not defined
		in RFC 2109.  See
		for more information.  Please note this feature is not honored by all

Valid Directory/.htaccess Directives
Directive:	CASScope
Default:	Off	
Description:	Use this directive with an argument as a relative path (e.g. /application/) to specify
		the scope for which a mod_auth_cas cookie is valid.  This is beneficial to prevent
		additional round trips to the CAS server.  Assume someone authenticates to /application/subdir/
		and then browses to /application/ - without CASScope set, each request would result in
		a round trip to the CAS server and a new cookie being created (one for each directory).
		CASScope would set one cookie, which will be presented on access to both directories.
		Note that if someone accessed /application/ and then /application/subdir/ this would not
		be an issue, but that order of access can not be guaranteed.  To disable this feature,
		the special argument 'Off' will return to per-directory cookie paths for this directory
		and subdirectories.

Directive: 	CASRenew
Default:	Off
Description:	Use this directive with an argument as a relative path (e.g. /application/secure/
		for*) to force a user to renew their
		credentials when accessing that directory.  The argument MUST be a relative path.
		To disable this requirement, the special argument 'Off' will disable this requirement
		for this directory and subdirectories.

Directive: 	CASGateway
Default:	Off
Description:	Use this directive with an argument as a relative path (e.g. /application/insecure/
		for*) to allow anonymous access to that directory.
		The argument MUST be a relative path. To disable this feature, the special argument 'Off'
		will reinstate the requirement for authentication.

Directive: 	CASCookie
Description:	The name of the cookie used to store the session ID over HTTP connections.
		It should be changed if it will interfere with the application protected
		by mod_auth_cas.

Directive: 	CASSecureCookie
Description:	The name of the cookie used to store the session ID over HTTPS connections.
		It should be changed if it will interfere with the application protected
		by mod_auth_cas.

Directive: 	CASGatewayCookie
Description:	The name of the cookie used to store whether or not the user has attempted
		to access this resource before.  It should be changed if it will interfere
		with the application protected by mod_auth_cas.

Directive:	CASAuthNHeader
Default:	None
Description:	If enabled, this will store the user returned by CAS in an HTTP header
		accessible to your web applications.

Directive:	CASSSOEnabled
Default:	Off
Description:	If enabled, this activates support for Single Sign Out within the CAS
		protocol.  Please note that this feature is currently experimental and
		may mangle POST data.

Phil Ames 	<modauthcas [at] gmail [dot] com>

Phil Ames 	<modauthcas [at] gmail [dot] com>
Matt Smith 	<matt [dot] smith [at] uconn [dot] edu>

Portions of this module are based on code from a CAS module by Yale.
See comments in mod_auth_cas.c

We welcome your feedback, suggestions and contributions. Contact us
via email if you have questions, feedback, code submissions, 
and bug reports.

Something went wrong with that request. Please try again.