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- In current stable and testing, verifying SSH remote hosts using RSA is not working. After selecting the verified RSA fingerprint, paramiko fails to connect - A change introduced in paramiko 2.9 lead to failures when connecting to hosts that have a verified RSA host key[1][2][3]. To fix the issue, disabled_algorithms must be used to drop some of the other algorithms supported by the server to force paramiko behavior. A better solution to the problem was introduced in paramiko 3.2. Both these solutions require careful update to the code. Considering the utility paramiko provides, the regression annoyance, effort required for this fix, and the security implications (it is an completely independent SSH implementation), the library does not seem to be worth the effort in our case. - Switch to using sshpass command line utility instead of paramiko library. The only reason to use paramiko seems that 'ssh' command by default does not allow us to input password easily while paramiko does. - Another place where paramiko is being used is to check if a host is already verified in the known_hosts file. This has been trivially replaced with 'ssh-keygen -F'. - Exit codes provided by sshpass can replace the specific exception raised by paramiko. Links: 1) https://www.paramiko.org/changelog.html 2) https://github.com/paramiko/paramiko/issues/2017 3) https://github.com/paramiko/paramiko/issues/1984 Tests: - Add a remote backup repository with and without encryption. - Add remote backup repository with all three types of algorithms. - Add a remote repository again with wrong password. Authentication error is properly shown. - Add a remote backup repository and remove it. Host remains verified. Add a repository again. - Add a remote backup repository and remove it. Host remains verified. Change the fingerprint the /var/lib/plinth/.ssh/known_hosts file. Add a repository again. A proper error is shown that remote host could not be verified. - Add a remote backup repository and remove it. Host remains verified. Stop SSH server on the remote host. A generic error is shown that ssh command on remote host failed. Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org> Reviewed-by: James Valleroy <jvalleroy@mailbox.org>