Disable weak CBC and MD5 MAC algorithms in SFTP backup interface

Detail name	Value
Changelog Number	10883
Type	Bug
Status	Resolved
Affected Versions	Exasol 6.1.0, Exasol 6.2.0, Exasol 7.0.0
Fix Versions	Exasol 7.0.3, Exasol 6.2.11, Exasol 6.1.13
Resolution Date	2020-10-14

Background

ExaOperation offers an interface to access backups via SFTP and https. This can be controlled by the option "Disable Backup Download Interfaces" in ExaOperation. By default, the interface is disabled. 
The ssh server used for SFTP was configured to support several algorithms that are considered weak. These findings are considered to have low severity:

• https://www.tenable.com/plugins/nessus/70658
• https://www.tenable.com/plugins/nessus/71049

Fix

• CBC mode cipher encryption has been disabled.
• MD5 MAC algorithms has been disabled. 
• CTR cipher mode encryption has been enabled.

Changed behavior

Weak CBC and MD5 MAC algorithms were deactivated in SFTP backup interface (see issue description for more detail)