sshpass-p4k is modified version of sshpass for handling also ssh key authentication with passphrases, e.g. when ssh client prompts passphrase for key. Passphrase is supplied like password to sshpass via command line parameters (-p), environment variable (-e), line from file (-f) or file descriptor (-d). See sshpass man page for more details.
P4K suffix is abbreviation from passphrase-for-key = pass4key = P4K
There are no other modifications to sshpass except providing passphrase on ssh prompt "passphrase for key".
ssh-agent offers the same functionality, but the passphrase has to be entered in advance so decrypted private key could be kept in memory. Therefore on logout, reboot etc the decrypted memory key is lost and has to be again entered interactively by the user.
See ssh-agent man page for more details.
The main motivation behind sshpass-p4k is ability to execute non-interactive ssh key authenticated batch/cron jobs in QA environment for automation testing. Ssh-agent due to security concerns should not be used in production environment (use ssh-agent), please se cons bellow.
There are security implications from storing password or/and passphrase on the system, see sshpass man page for more details. Never store passwords or passphrases on production systems. You have been warned.
Cron jobs, batch jobs which cannot for whatever reason use ssh-agent would benefit from sshpass-p4k. If you don't need key based authentication with passphrases stay with original sshpass, you will not benefit from using sshpass-p4k. However, even in this case by using sshpass-p4k you will not loose anything and you can easily switch to hey based authentication in the future.
no key based authentication -> stay with sshpass
key based authentication -> consider ssh-agent, if cannot -> use sshpass-p4k
Hope this helps,
keywords: sshpass, passphrase, key, authentication, ssh-agent, QA