Security Bulletin: Vulnerability in Diffie-Hellman ciphers affects Rational DOORS Web Access (CVE-2015-4000)

Summary

The Logjam Attack on TLS connections using the Diffie-Hellman (DH) key exchange protocol affects IBM Rational DOORS Web Access.

Vulnerability Details

Rational DOORS Web Access is affected by the following vulnerability:

CVEID: CVE-2015-4000** **

DESCRIPTION: The TLS protocol could allow a remote attacker to obtain sensitive information, caused by the failure to properly convey a DHE_EXPORT ciphersuite choice. An attacker could exploit this vulnerability using man-in-the-middle techniques to force a downgrade to 512-bit export-grade cipher. Successful exploitation could allow an attacker to recover the session key as well as modify the contents of the traffic. This vulnerability is commonly referred to as “Logjam”.

CVSS Base Score: 4.3 **CVSS Temporal Score:**See https://exchange.xforce.ibmcloud.com/vulnerabilities/103294 for the current score *CVSS Environmental Score:**Undefined CVSS Vector: (AV:N/AC:M/Au:N/C:P/I:N/A:N)

Affected Products and Versions

Rational DOORS Web Access version 9.6.1.3, 9.6.1.2, 9.6.1.1, 9.6.1.0, 9.6.0.x, 9.5.2.x, 9.5.1.x, 9.5.0.x, 1.5.0.x, 1.4.0.x.

Remediation/Fixes

Prior to the upgrade described below, there is no mitigation if any of the EXPORT ciphers have been enabled. EXPORT cipher suites are vulnerable to the FREAK and LOGJAM vulnerabilities with no mitigation possible. Do not enable these ciphers without complete understanding of the environment.

For all others, consider implementing one of the mitigation methods described below.
**
Java 6 Mitigation:**

For Rational DOORS Web Access installations that include JRE version 6, upgrade the JRE as noted in the table below. You can upgrade the JRE after Rational DOORS Web Access is installed.

To obtain the updated version of the IBM JRE, contact IBM Support. Support can help identify the latest JRE that is compatible with your operating system and platform. Publicly available versions of the Oracle JRE are not supported with Rational DOORS Web Access.

The following table presents Rational DOORS Web Access versions and the compatible versions of IBM JRE.

To install the updated JRE in Rational DOORS Web Access, see this help topic:
Upgrading the Rational DOORS Web Access JRE

You should verify that applying this configuration change does not cause any compatibility issues. If you change the default setting after applying the fix, you will expose yourself to the attack described above. IBM recommends that you review your entire environment to identify other areas where you have enabled the Diffie-Hellman key-exchange protocol used in TLS and take appropriate mitigation and remediation actions.

Workarounds and Mitigations

Java 7 and Java 8 Mitigation:

For Rational DOORS Web Access installations that include JRE version 7 or 8, perform the following mitigations.

• Disable DH and DHE cipher suites. The can be achieved by adding the DH and DHE cipher suites to the list of disabled algorithms defined by the jdk.tls.disabledAlgorithms security property in java.security file.
• Do not explicitly enable the DH or DHE cipher suite(s) via setEnabledCipherSuites() method.
• For HttpsURLConnection, set https.cipherSuites system property to not include DH or DHE cipher suites.
• Configure SP800-131a strict compliance or any Suite B configuration.
• For those which use JVM defaults or the default list of ciphers provided by the JVM, apply the iFix which will enforce a minimum 768 bit prime size for DH and DHE cipher suites and resolve the problem.

For Java the DH server keysize is 1024 unless SP800-131a strict compliance or Suite B compliance is configured. For those configurations, the server keysize is 2048. On Java 8 this is configurable. At this time, this is not configurable for Java 5, 6, and 7.

As the length of the server key size are increased, the amount of CPU required for full TLS/SSL handshake can significantly increase. Please carefully test and assess the impact to your CPU requirements to ensure sufficient CPU resources, otherwise the system availability may be impacted.

You should verify that applying this configuration change does not cause any compatibility issues. If you change the default setting after applying the fix, you will expose yourself to the attack described above. IBM recommends that you review your entire environment to identify other areas where you have enabled the Diffie-Hellman key-exchange protocol used in TLS and take appropriate mitigation and remediation actions.