$ ssh -N -L 1521:10.0.1.2:1521 -i ~/.ssh/key.pem -4 ec2-user@1.23.45.67
The authenticity of host '1.23.45.67 (1.23.45.67)' can`t be established.
ECDSA key fingerprint is SHA256:xxxxx.....
ECDSA key fingerprint is MD5:xx:xx:....
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '1.23.45.67' (ECDSA) to the list of known hosts.
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@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
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Permissions 0664 for '/home/ponsuke/.ssh/key.pem' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Load key "/home/ponsuke/.ssh/key.pem": bad permissions
Permission denied (publickey).