I can't SSH (Huntress CTF 2024)

Author: @JohnHammond

I’ve got this private key… but why can’t I SSH?

The password is given when starting the container server. Trying to connect results in failure, with ssh telling us the public key is invalid. It also scolds us for using an insecure private key file. Anyways, opening this file shows that it is a OPENSSH PRIVATE KEY. We need to convert this into a rsa key:

puttygen id_rsa -O private-sshcom -o newkey
ssh-keygen -i -f newkey > newkey_in_right_format

However, when trying, it still fails:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for 'newkey_in_right_format' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.

Notice the This private key will be ignored. So we need to change the permission.

chmod 400 newkey_in_right_format

SSH in and enter the password, and we get in. Flag is stored in a text file in the home directory.