This article applies to:

• WebDefend - All Versions

Question:

• How do I disable Diffie-Hellman on Apache web servers?
• Diffie-Hellman key exchange is not supported by WebDefend

Procedure:

To disable Diffie-Hellman key exchange, edit the SSL configuration file.

The location of the SSL configs depends on the version of Apache and the customer installation. For example, some Apache 2.2.3 installations have the SSL data in the file /usr/local/apache/conf/extra/httpd-ssl.conf 

A possible SSL cipher configuration (with explanatory comments) is given below. You should confirm the applicability of this configuration for your environment before applying it.

# Disallow ciphers that are weak (obsolete or
# known to be flawed in some way). The use of
# an exclamation mark in front of a cipher code
# tells Apache never to use it. EXP refers to 40-bit
# and 56-bit ciphers, NULL ciphers offer no encryption.
# DH refers to Diffie-Hellman key exchange,
# and LOW refers to other low strength ciphers.

SSLCipherSuite ALL:!EXP:!NULL:!DH:!LOW