Many Concurrent SSH/SFTP sessions are failing for AD Users

Issue

• Many Concurrent SFTP Jobs are being triggered using domain user (AD/SSSD user) and few of them fails.

• MaxStartup issue from sshd end was fixed which allowed multiple SSH connections to authenticate simultaneously.

• After fixing MaxStartup below errors were seen at the time of issue.

  Jan 23 05:55:26 localhost sshd[10081]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:28 localhost sshd[10091]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:34 localhost sshd[10109]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:34 localhost sshd[10123]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:34 localhost sshd[10122]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:35 localhost sshd[10126]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:55 localhost sshd[10201]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:56 localhost sshd[10210]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:58 localhost sshd[10222]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:59 localhost sshd[10219]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:56:03 localhost sshd[10237]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  

• Below were details of single failure

  Jan 23 05:53:54 localhost sshd[10081]: debug3: PAM: sshpam_passwd_conv called with 1 messages
  Jan 23 05:55:26 localhost sshd[10081]: debug1: PAM: password authentication failed for domain_user: Authentication failure
  Jan 23 05:55:26 localhost sshd[10081]: debug3: mm_answer_authpassword: sending result 0
  Jan 23 05:55:26 localhost sshd[10081]: debug3: mm_request_send entering: type 13
  Jan 23 05:55:26 localhost sshd[10081]: Failed password for domain_user from 10.54.159.59 port 58829 ssh2
  Jan 23 05:55:26 localhost sshd[10081]: Excess permission or bad ownership on file /var/log/btmp