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README
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====================================================================
MOD_AUTH_CAS 1.0.9 README
====================================================================
Apache CAS Authentication Module
====================================================================
LICENSE
====================================================================
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
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
====================================================================
INTRODUCTION
====================================================================
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:
http://www.ja-sig.org/products/cas/overview/protocol/index.html
====================================================================
NEW FEATURES AND FUNCTIONS IN THIS RELEASE
====================================================================
* 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.
====================================================================
BUG FIXES
====================================================================
* Included a patch by Chris Adams of Yale University to prevent
segfaults when parsing a corrupted XML cache file.
====================================================================
KNOWN LIMITATIONS
====================================================================
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
request).
* 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.
====================================================================
GETTING STARTED
====================================================================
SOFTWARE DEPENDENCIES
--------------------------------------------------------------------
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
mod_auth_cas.
Compatibility with other versions will depend on those other libraries.
INSTALLATION INSTRUCTIONS
--------------------------------------------------------------------
Ensure that the follow files are in the working directory:
mod_auth_cas.c
mod_auth_cas.h
COMPILE INSTRUCTIONS
--------------------------------------------------------------------
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
or
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.
CONFIGURING THE SOFTWARE
--------------------------------------------------------------------
First, you must tell Apache to load the module. In your httpd.conf,
add:
LoadModule auth_cas_module /path/to/mod_auth_cas.so
Then, in the location(s) you want to protect, use the following
directive:
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 *.example.com and the hostname portion of the CASValidateURL
is 'cas.login.example.com', this directive (if enabled) will accept that
certificate.
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 http://msdn2.microsoft.com/en-us/library/ms533046.aspx
for more information. Please note this feature is not honored by all
browsers.
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 http://www.example.com/application/secure/*) 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 http://www.example.com/application/insecure/*) 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
Default: MOD_AUTH_CAS
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
Default: MOD_AUTH_CAS_S
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
Default: MOD_AUTH_CAS_G
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.
====================================================================
CONTRIBUTORS
====================================================================
Author:
Phil Ames <modauthcas [at] gmail [dot] com>
Designers:
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
====================================================================
CONTACT INFORMATION AND WEBSITE
====================================================================
We welcome your feedback, suggestions and contributions. Contact us
via email if you have questions, feedback, code submissions,
and bug reports.
====================================================================