sftp fails after upgrade to SLES 12

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Environment

SUSE Linux Enterprise Server 12 Service Pack 1 (SLES 12 SP1)

SUSE Linux Enterprise Server 12 Service Pack 2 (SLES 12 SP2)

SUSE Linux Enterprise Server 12 Service Pack 3 (SLES 12 SP3)

SUSE Linux Enterprise Server 12 Service Pack 4 (SLES 12 SP4)

Open Enterprise Server 2018 (OES 2018)

Situation

A 64-bit system has been upgraded from SLES 11 to SLES 12. Afterwards, sftp sessions are disconnected after the user submits their password. An openssh sftp client simply gives the error:

Connection closed

Or in verbose mode (sftp -vvv) it shows:

debug1: Exit status 127
Connection closed

Resolution

Edit /etc/ssh/sshd_config and change the following line:

Subsystem sftp /usr/lib64/ssh/sftp-server

to:

Subsystem sftp /usr/lib/ssh/sftp-server

After saving the change, execute the following to put the change into effect:

systemctl restart sshd

Cause

The 64 bit openssh package on SLES 12 SP1 and higher no longer stores it's sftp-server binary under /usr/lib64/ssh. It now uses /usr/lib/ssh. In a fresh install, this would be set correctly, but in an upgrade situation where older configuration files are preserved, the old location might still be specified.

Disclaimer

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