Use of SSH Steps plugin on RHEL 9

Using Jenkins
1

I am using the SSH Pipeline Steps plugin within a Jenkins pipeline. Here is an example of my code:

def appServer1 = [name: “DEV”, host:“xxxxxx”, allowAnyHosts: true]

pipeline {
 agent any
 stages {
  stage (“Which OS release?”) {
   steps {
    script {
     withCredentials(credentialsId:“CRED”, keyFileVariable:“sshKey”, usernameVariable:“sshUser”) {
      appServer1.user = sshUser
      sh "cp " + sshKey + “${WORKSPACE}/private_key”
      appServer1.identityFile = “${WORKSPACE}/private_key”
     }
    }
    sshCommand(remote: appServer1, command: “cat /etc/os-release”)
   }
  }
 }
}

where CRED is a set of credentials created in the Dashboard containing the private part of the SSH key

This setup works perfectly when the ‘appServer’ OS is RHEL 8 but recently I updated the OS to RHEL 9 and it only works when I invoke SSH directly from the command line, i.e. not through Jenkins. Now the sshCommand line results in an error of:

com.jcraft.jsch.JSchException: Auth Fail
  at com.jcraft.jsch.Session.connect(Session.java:519)
  …

I think the RSA encryption is the issue as the /var/log/secure log on ‘appServer1’ reports

key type ssh-rsa not in PubkeyAcceptedAlgorithms

I have therefore tried using public-private SSH key pairs generated using all the other forms of encryption (DSA, ECDSA, ED25519, etc) but they result in an error message of:

com.jcraft.jsch.JSchException: invalid privatekey: [B@Sffa0e74
  at com.jcraft.jsch.KeyPair.load(KeyPair.java:664)
  …

Any ideas how to change the encryption method that the SSH Pipeline Steps plugin uses?? Or if there is some other reason why this solution does not work on RHEL 9 when it was fine on RHEL 8???

2

Do you have latest versions of SSH Pipeline Steps and JSch dependency plugins installed?


PS: These 2 lines are a security issue. They make the private key accessible from the workspace browser and the file will not be deleted once the withCredentials block is left.

sh "cp " + sshKey + “${WORKSPACE}/private_key”
appServer1.identityFile = “${WORKSPACE}/private_key”

Better to just use

appServer1.identityFile = sshKey
3

I did not have the latest versions of the plugins installed but I have installed them now and unfortunately, there is no change, still the same error message.

The way that I solved / bypassed this problem in the end was to simply not use the plugins at all.
I used the following code (incorporating your suggestion) inside the withCredentials block:

sh "ssh appServer1 -l " + sshUser + " -i " + sshKey + " ‘cat /etc/os-release’