CCUM 15.0.1 DRS backups stoped working all of sudden with QNAP SFTP

[AdamG73545]

They stopped working all of a sudden. The only thing is firmware on QNAP could auto-update. So probably a new SSH RSA key was generated. I deleted the backup device, and now I can not set it up from scratch. It says invalid user - login which is not true. I can access the device and path with any other clients using Linux, windows, etc. but not CCUM DRS. 

I know I am using the right QNAP user and password + valid path. I have created another user on QNAP and same thing. It has to be the problem with CCUM DRS. I have restarted Backup and Restore Services under Unified servicibility but no luck. 

[marce1000]

 - Checkout : https://www.reddit.com/r/Cisco/comments/3m6efo/cisco_drs_and_qnap_sftp/

  M.

[Paul Alfonso · Accepted solution]

I have the same issue possibly after a Tomcat Certificate update. Running System version: 14.0.1.13900-155.

Backups to my main server works fine, TAC ran pcaps and found the QNAP is using an unsupported encryption.

From the Win-SFTP device the SSH handshake is taking place using SSH Cipher “aes256-ctr”.

From the QNAP-SFTP device the SSH handshake is using SSH KEX method “ecdh-sha2-nistp256”.

[+] As per documentation, when the cipher “ecdh-sha2-nistp256” is configured under the “SSH KEX” ciphers string, it will break the DRS functionality. Refer to: Recommended Ciphers. 

[AdamG73545]

Thank you, seem slike this is the problem. 

[AdamG73545]

Also, not every QNAP is affected. Older QNAP works fine.