Possible Root Cause of "Unprotected Private Key File" Error

Answer: B.

Option A is incorrect because the IAM role assigned to the user is not related to logging into EC2 instances using SSH.

Option B is CORRECT because your private key file must be protected from read and write operations from any other users.

Option C is incorrect because the issue is with the private key.

Hence, solving permissions on the public key would not provide the solution to the error.

Option D is incorrect because KMS is not used to manage user public-key pairs for EC2 instances.

To fix the error, execute the following command and substitute the path for your private key file.

chmod 0400 .ssh/.pem.

Reference:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html#troubleshoot-unprotected-key

The most likely cause of the "Unprotected Private Key File" error is that the private key file has the wrong file permissions. SSH requires that private key files are readable only by the owner. If the permissions are too open, SSH will refuse to use the key, as it is considered unsafe.

To fix this issue, you should update the file permissions on the private key file. The correct permissions are typically 600 or 400, which means that only the owner of the file can read or write to it. You can set these permissions using the chmod command, for example:

vbnetCopy code
chmod 600 private-key.pem 

It is less likely that this error is caused by the IAM Role not having sufficient permissions. IAM Roles control access to AWS services, but they do not affect the permissions on the private key file used for SSH access.

Similarly, it is unlikely that the public key file has the wrong permissions or that the KMS CMK key policy has the wrong permissions, as these do not affect the use of the private key file for SSH access. The public key file is used to authenticate the user, while the KMS CMK key policy is used to control access to AWS Key Management Service keys.