The SSH daemon must be configured to not use CBC ciphers.

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The SSH daemon must be configured to not use CBC ciphers.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-22459	GEN005506 M6	SV-39364r1_rule	ECSC-1	Medium

Description
The Cipher-Block Chaining (CBC) mode of encryption as implemented in the SSHv2 protocol is vulnerable to chosen plaintext attacks and must not be used.

STIG	Date
MAC OSX 10.6 Workstation Security Technical Implementation Guide Draft	2013-01-10

Details

Check Text ( C-38312r1_chk )
Open a terminal session and enter the following command. grep ciphers /etc/sshd_config If no lines are returned, or the returned ciphers list contains any cipher ending with CBC, this is a finding.

Fix Text (F-33601r1_fix)
Open a terminal session and edit the SSH daemon configuration file "/etc/sshd_config" and remove any ciphers ending with "CBC". If necessary, add a Ciphers line.