convert-putty-ppk-to-openssh.md

Convert Putty (PPK) SSH key file to OpenSSH key file

See the quick tutorial on SuperUser.

Step One: Install Putty

You need putty, or at least the tools that come with it.

$ brew install putty 
$ # OR
$ sudo apt install putty

Step Two: Generate OpenSSH Key Files

Generate the private key from the PPK file:

$ puttygen mborn.ppk -O private-openssh -o ~/.ssh/myKey

Generate the public key from the PPK file:

$ puttygen mborn.ppk -O public-openssh -o ~/.ssh/myKey.pub

Step Three: Allow ssh-dss Key Format

For whatever reason, Putty seems to only support generating a key file in DSS format. This causes an error something like this (use the -v flag to display verbose errors in ssh):

Skipping ssh-dss key /Users/me/.ssh/myKey - not in PubkeyAcceptedKeyTypes

This is because the ssh-dss key format was disabled in OpenSSH 7.0. To re-enable ssh-dss, add the following to your ~/.ssh/config file OR your global /etc/ssh/ssh_config file. (Thanks to gryphonitsolutions for the tip.)

PubkeyAcceptedKeyTypes=+ssh-dss

(ps. I would love pointers on how to convert a PPK to RSA instead of DSS! This would save us from any issues with this step.)

Step Four: Reload SSH Service

You may need to restart the SSH service if you made config updates in /etc/ssh/ssh_config instead of your local config file:

$ sudo launchctl stop com.openssh.sshd
$ sudo launchctl start com.openssh.sshd