Troubleshooting Guide

Application X “redirected you too many times”

“Too many redirect” errors are usually cause by service ticket validation failure events, generally caused by application misconfiguration. Ticket validation failure may be caused by expired or unrecognized tickets, SSL-related issues and such. Examine your CAS logs and you will find the cause.

Not Receiving Attributes

If your client application is not receiving attributes, you will need to make sure:

  1. The client is using a version of CAS protocol that is able to release attributes.
  2. The client, predicated on #1, is hitting the appropriate endpoint for service ticket validation.
  3. The CAS server itself is resolving and retrieving attributes correctly.
  4. The CAS server is authorize to release attributes to that particular client application inside its service registry.

Please review this guide to better understand the CAS service registry.

Login Form Clearing Credentials

You may encounter an issue where upon submission of credentials on the login form, the screen clears the input data and asks the user again to repopulate the form. The CAS Server log may also indicate the received login ticket is invalid and therefore unable to accept the authentication request.

The CAS server itself initiates a web session upon authentication requests that by default is configured to last for 5 minutes. The state of the session is managed at server-side and thus, once the session expires any authentication activity on the client side such as submission of the login form is disregarded until a new session a regenerated. Another possible cause may be related to a clustered CAS environment where CAS nodes are protected by a load balancer whose “timeout” is configured less than the default session expiration timeout of CAS. Thus, once the authentication form is submitted and the request is routed to the load balancer, it is seen as a new request and is redirected back to a CAS node for authentication.

To remedy the problem, the suggestion is to configure the default CAS session timeout to be an appropriate value that matches the time a given user is expected to stay on the login screen. Similarly, the same change may be applied to the load balancer to treat authentication requests within a longer time span. In web.xml, adjust the session-timeout attribute to extend the session expiration time.

Application Not Authorized

You may encounter this error, when the requesting application/service url cannot be found in your CAS service registry. When an authentication request is submitted to the CAS login endpoint, the destination application is indicated as a url parameter which will be checked against the CAS service registry to determine if the application is allowed to use CAS. If the url is not found, this message will be displayed back. Since service definitions in the registry have the ability to be defined by a url pattern, it is entirely possible that the pattern in the registry for the service definition is misconfigured and does not produce a successful match for the requested application url.

Please review this guide to better understand the CAS service registry.

Invalid/Expired CAS Tickets

You may experience INVAILD_TICKET related errors when attempting to use a CAS ticet whose expiration policy dictates that the ticket has expired. The CAS log should further explain in more detail if the ticket is considered expired, but for diagnostic purposes, you may want to adjust the ticket expiration policy configuration to remove and troubleshoot this error.

Furthermore, if the ticket itself cannot be located in the CAS ticket registry the ticket is also considered invalid. You will need to observe the ticket used and compare it with the value that exists in the ticket registry to ensure that the ticket id provided is valid.

Out of Heap Memory Error

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java.lang.OutOfMemoryError: GC overhead limit exceeded
        at java.util.Arrays.copyOfRange(Arrays.java:3658)
        at java.lang.StringBuffer.toString(StringBuffer.java:671)
        at 

You may encounter this error, when in all likelihood, a cache-based ticket registry such as EhCache is used whose eviction policy is not correctly configured. Objects and tickets are cached inside the registry storage back-end tend to linger around longer than they should or the eviction policy is not doing a good enough job to clean unused tickets that may be marked as expired by CAS.

To troubleshoot, you can configure the JVM to perform a heap dump prior to exiting, which you should set up immediately so you have some additional information if/when it happens next time. The follow system properties should do the trick:

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-XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath="/path/to/jvm-dump.hprof" 

Also ensure that your container is configured to have enough memory available. For Apache Tomcat, the following setting as an environment variable may be configured:

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CATALINA_OPTS=-Xms1000m -Xmx2000m

You will want to profile your server with something like JVisualVM which should be bundled with the JDK. This will help you see what is actually going on with your memory.

You might also consider taking periodic heap dumps using the JMap tool or YourKit Java profiler and analyzing offline using some analysis tool.

Finally, review the eviction policy of your ticket registry and ensure the values that determine object lifetime are appropriate for your environment.

PKIX Path Building Failed

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Sep 28, 2009 4:13:26 PM org.jasig.cas.client.validation.AbstractCasProtocolUrlBasedTicketValidator retrieveResponseFromServer
SEVERE: javax.net.ssl.SSLHandshakeException:
sun.security.validator.ValidatorException: PKIX path building failed:
sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
javax.net.ssl.SSLHandshakeException:
sun.security.validator.ValidatorException: PKIX path building failed:
sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
      at com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Unknown Source)
      at com.sun.net.ssl.internal.ssl.SSLSocketImpl.fatal(Unknown Source)
      at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Unknown Source)
      at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Unknown Source)
      at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(Unknown Source)

PKIX path building errors are the most common SSL errors. The problem here is that the CAS client does not trust the certificate presented by the CAS server; most often this occurs because of using a self-signed certificate on the CAS server. To resolve this error, import the CAS server certificate into the system truststore of the CAS client. If the certificate is issued by your own PKI, it is better to import the root certificate of your PKI into the CAS client truststore.

By default the Java system truststore is at $JAVA_HOME/jre/lib/security/cacerts. The certificate to be imported MUST be a DER-encoded file. If the contents of the certificate file are binary, it’s likely DER-encoded; if the file begins with the text ---BEGIN CERTIFICATE---, it is PEM-encoded and needs to be converted to DER encoding.

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keytool -import -keystore $JAVA_HOME/jre/lib/security/cacerts -file tmp/cert.der -alias certName

If you have multiple java editions installed on your machine, make sure that the app / web server is pointing to the correct JDK/JRE version (The one to which the certificate has been exported correctly) One common mistake that occurs while generating self-validated certificates is that the JAVA_HOME might be different than that used by the server.

No subject alternative names

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javax.net.ssl.SSLHandshakeException: java.security.cert.CertificateException: No subject alternative names present

This is a hostname/SSL certificate CN mismatch. This commonly happens when a self-signed certificate issued to localhost is placed on a machine that is accessed by IP address. It should be noted that generating a certificate with an IP address for a common name, e.g. CN=192.168.1.1,OU=Middleware,dc=vt,dc=edu, will not work in most cases where the client making the connection is Java.

HTTPS hostname wrong

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java.lang.RuntimeException: java.io.IOException: HTTPS hostname wrong:  should be <eiger.iad.vt.edu>
    org.jasig.cas.client.validation.Saml11TicketValidator.retrieveResponseFromServer(Saml11TicketValidator.java:203)
    org.jasig.cas.client.validation.AbstractUrlBasedTicketValidator.validate(AbstractUrlBasedTicketValidator.java:185)
    org.jasig.cas.client.validation.AbstractTicketValidationFilter.doFilter

The above error occurs most commonly when the CAS client ticket validator attempts to contact the CAS server and is presented a certificate whose CN does not match the fully-qualified host name of the CAS server. There are a few common root causes of this mismatch:

  • CAS client misconfiguration
  • Complex multi-tier server environment (e.g. clustered CAS server)
  • Host name too broad for scope of wildcard certificate

It is also worth checking that the certificate your CAS server is using for SSL encryption matches the one the client is checking against.

Wildcard Certificates

Java support for wildcard certificates is limited to hosts strictly in the same domain as the wildcard. For example, a certificate with CN=.vt.edu matches hosts a.vt.edu and b.vt.edu, but not a.b.vt.edu.

unrecognized_name Error

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javax.net.ssl.SSLProtocolException: handshake alert: unrecognized_name

The above error occurs mainly in Oracle JDK 7 CAS Server installations. In JDK7, SNI (Server Name Indication) is enabled by default. When the HTTPD Server does not send the correct Server Name back, the JDK HTTP Connection refuses to connect and the exception stated above is thrown.

You must ensure your HTTPD Server is sending back the correct hostname. E.g. in Apache HTTPD, you must set the ServerAlias in the SSL vhost:

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ServerName your.ssl-server.name
ServerAlias your.ssl-server.name

Alternatively, you can disable the SNI detection in JDK7, by adding this flag to the Java options of your CAS Servers’ application server configuration:

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-Djsse.enableSNIExtension=false

When All Else Fails

If you have read, understood, and tried all the troubleshooting tips on this page and continue to have problems, please perform an SSL trace and attach it to a posting to the CAS mailing list. An SSL trace is written to STDOUT when the following system property is set, javax.net.debug=ssl. An example follows of how to do this in the Tomcat servlet container.

Sample setenv.sh Tomcat Script follows:

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# Uncomment the next 4 lines for custom SSL keystore
# used by all deployed applications
# KEYSTORE="$HOME/path/to/custom.keystore"
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.ssl.keyStore=$KEYSTORE"
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.ssl.keyStoreType=BKS"
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.ssl.keyStorePassword=changeit"
 
# Uncomment the next 4 lines to allow custom SSL trust store
# used by all deployed applications
# TRUSTSTORE="$HOME/path/to/custom.truststore"
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.ssl.trustStore=$TRUSTSTORE"
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.ssl.trustStoreType=BKS"
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.ssl.trustStorePassword=changeit"
 
# Uncomment the next line to print SSL debug trace in catalina.out
# CATALINA_OPTS=$CATALINA_OPTS" -Djavax.net.debug=ssl"
 
export CATALINA_OPTS

Review logs

CAS server logs are the best resource for determining the root cause of the problem, provided you have configured the appropriate log levels. Specifically you want to make sure DEBUG levels are turned on the org.jasig package in the log configuration:

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<AsyncLogger  name="org.jasig" level="debug" additivity="false" includeLocation="true">
    <AppenderRef ref="console"/>
    <AppenderRef ref="file"/>
</AsyncLogger>

When changes are applied, restart the server environment and observe the log files to get a better understanding of CAS behavior. For more info, please review the this guide on how to configure logs with CAS.