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Friday, October 17, 2014

POODLE Attack and Disabling SSL V3 in Apache Tomcat

Early this week Google researchers announced that they have found a bug in the SSL 3.0 protocol. The exploit could be used to intercept critical data that’s supposed to be encrypted between clients and servers.

The exploit first allows attackers to initiate a “downgrade dance” that tells the client that the server doesn’t support the more secure TLS (Transport Layer Security) protocol and forces it to connect via SSL 3.0.

From there a man-in-the-middle attack can decrypt secure HTTP cookies.

POODLE

Google calls this the POODLE (Padding Oracle On Downgraded Legacy Encryption) attack.

This means, even both your server and the client support TLS, still due to the downgrade attack, both the parties can be forced to use SSL 3.0. If any one of the party disables its support for SSL 3.0 - that will help to mitigate the attack.

Both Chrome and Firefox already announced that they are going to disable the SSL 3.0 support by default. Firefox 34, with SSL 3.0 disabled,  will be released on 25th November. If you want to disable SSL 3.0 on firefox now, you can use the plugin SSL Version Control.

Chrome has already issued a patch to disable SSL 3.0.

Disable SSL V3 on Apache Tomcat

Following explains how to disable SSL 3.0 support on Apache Tomcat 7.x.x.
  1. Open [tomcat_home]/conf/server.xml
  2. Find the Connector configuration corresponding to TLS - usually this is having the port as 8443 and sslProtocol as TLS.
  3. If you are using JDK 1.6 then remove the attribute sslProtocol="TLS" from the above configuration and replace it with:  sslEnabledProtocols="TLSv1"
  4.  If you are using JDK 1.7 then remove the attribute sslProtocol="TLS" from the above configuration and replace it with:  sslEnabledProtocols="TLSv1,TLSv1.1,TLSv1.2"
Following explains how to validate the fix. You can download TestSSLServer.jar from here.

$ java -jar TestSSLServer.jar localhost 8443 

Output before the fix

Supported versions: SSLv3 TLSv1.0 TLSv1.1 TLSv1.2
Deflate compression: no
Supported cipher suites (ORDER IS NOT SIGNIFICANT):
  SSLv3
     RSA_WITH_RC4_128_MD5
     RSA_WITH_RC4_128_SHA
     RSA_WITH_3DES_EDE_CBC_SHA
     DHE_RSA_WITH_3DES_EDE_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA
     TLS_ECDHE_RSA_WITH_RC4_128_SHA
     TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
     TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
  (TLSv1.0: idem)
  (TLSv1.1: idem)
  TLSv1.2
     RSA_WITH_RC4_128_MD5
     RSA_WITH_RC4_128_SHA
     RSA_WITH_3DES_EDE_CBC_SHA
     DHE_RSA_WITH_3DES_EDE_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA256
     DHE_RSA_WITH_AES_128_CBC_SHA256
     TLS_ECDHE_RSA_WITH_RC4_128_SHA
     TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
     TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
     TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256

Output after the fix

Supported versions: TLSv1.0 TLSv1.1 TLSv1.2
Deflate compression: no
Supported cipher suites (ORDER IS NOT SIGNIFICANT):
  TLSv1.0
     RSA_WITH_RC4_128_MD5
     RSA_WITH_RC4_128_SHA
     RSA_WITH_3DES_EDE_CBC_SHA
     DHE_RSA_WITH_3DES_EDE_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA
     TLS_ECDHE_RSA_WITH_RC4_128_SHA
     TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
     TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
  (TLSv1.1: idem)
  TLSv1.2
     RSA_WITH_RC4_128_MD5
     RSA_WITH_RC4_128_SHA
     RSA_WITH_3DES_EDE_CBC_SHA
     DHE_RSA_WITH_3DES_EDE_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA256
     DHE_RSA_WITH_AES_128_CBC_SHA256
     TLS_ECDHE_RSA_WITH_RC4_128_SHA
     TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
     TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
     TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256

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