Unable to start migration in Plesk: Failed to connect to the source server ‘source’ (203.0.113.2) by SSH: encountered RSA key, expected OPENSSH key

Symptoms

• Migration via SSH key fails with one of the following errors in Tools & Settings > Migration and Transfer Manager:

  Failed to connect to the source server 'source' (203.0.113.2) by SSH: encountered RSA key, expected OPENSSH key

  Failed to check SSH connection to the source server 'source' (203.0.113.2): q must be exactly 160, 224, or 256 bits long

  Failed to check SSH connection to the source server 'source' (203.0.113.2): p must be exactly 1024, 2048, or 3072 bits long

• Paramiko version 2.9 or above is installed on the target server:

  Debian-based OS (Debian, Ubuntu, etc.):

  # dpkg --list | grep paramiko
  ii plesk-py27-paramiko 2.10.3-ubuntu.20.04.220330.1131 amd64 SSH2 protocol library

  RPM-based OS (CentOS, RHEL, CloudLinux, AlmaLinux, etc.):

  # rpm -qa | grep paramiko
  plesk-py27-paramiko-2.10.3-1centos.7.220330.1131.x86_64

• OpenSSH version 5.9 or lower is installed on the source server:

  # ssh -V
  OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013

Cause

Workaround

Regardless of which Linux distributive is in use, before applying the personalized steps below, add the SSH-RSA support to the SSH client's config file at /etc/ssh/ssh_config

1. Connect to the target server via SSH;

2. open the file

   # vi /etc/ssh/ssh_config

3. Add the following line

   # PubkeyAcceptedKeyTypes +ssh-rsa