Since a few days I get an error message when I try to establish an ssh connection to my compute instance "linux4" from the cloud shell or a remote shell. The error message is: "Permission denied (publickey,gssapi-keyex,gssapi-with-mic)".
Until a few days ago (or weeks - I don't know exactly when I last connected successfully), ssh worked fine. While analyzing it, I came across the keyword "FIPS". A new security mechanism that seems to have been introduced on the compute instances and requires the public key to be regenerated (see "https://community.oracle.com/customerconnect/discussion/684402/ssh-fails-with-error-fips-mode-initialized-fips-mode-initialized-ssh-connect-to-host"). For crosschecking I created a new compute instance "linux2" and put the same public key there and ssh works!
My question is now, if FIPS is the cause for the failure, how can I regenerate the key on "linux4" if I can't connect to the machine at all?
# ssh to the elder instance "linux4" fails with "permission denied"
harrdie@cloudshell:~ (eu-frankfurt-1)$ ssh -i .ssh/oracle_cloud_key opc@130.61.61.231
FIPS mode initialized
Enter passphrase for key '.ssh/oracle_cloud_key':
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
harrdie@cloudshell:~ (eu-frankfurt-1)$
# ssh to new instance "linux2" works
harrdie@cloudshell:~ (eu-frankfurt-1)$ ssh -i .ssh/oracle_cloud_key opc@130.61.111.207
FIPS mode initialized
Enter passphrase for key '.ssh/oracle_cloud_key':
Activate the web console with: systemctl enable --now cockpit.socket
Last login: Sat Sep 2 09:16:35 2023 from 132.145.236.16
[opc@linux2 ~]$ exit
logout
Connection to 130.61.111.207 closed.