How to convert .ppk key to OpenSSH key under Linux?

Question

I know that is possible to convert .ppk under puttygen in Windows, but how to do that on Linux? Is this possible ?

Answer 1

Do it with Putty.

• Linux: with your package manager, install PuTTY (or the more minimal PuTTY-tools):

• Ubuntu: sudo apt-get install putty-tools
• Debian-like: apt-get install putty-tools
• RPM based: dnf install putty or yum install putty
• Gentoo: emerge putty
• Archlinux: sudo pacman -S putty
• etc.

• OS X: Install Homebrew, then run brew install putty

Place your keys in some directory, e.g. your home folder. Now convert the PPK keys to SSH keypairs:cache search

To generate the private key:

cd ~
puttygen id_dsa.ppk -O private-openssh -o id_dsa

and to generate the public key:

puttygen id_dsa.ppk -O public-openssh -o id_dsa.pub

Move these keys to ~/.ssh and make sure the permissions are set to private for your private key:

mkdir -p ~/.ssh
mv -i ~/id_dsa* ~/.ssh
chmod 600 ~/.ssh/id_dsa
chmod 666 ~/.ssh/id_dsa.pub

If you have already tried to perform a 'git clone' operation you might need to do this also

chmod 666 ~/.ssh/known_hosts

Answer 2

ssh-keygen -i -f id_dsa_1024_a.pub > id_dsa_1024_a_openssh.pub

• -i flag is import from other than openssh format
• -f flag means read from input file

Source: a blogpost at burnz.wordpress.com

Answer 3

Get the private key:

open the .ppk file in puttygen:

puttygen ~/.ssh/id_dsa.ppk

export as openssh:

Conversions → Export OpenSSH key

Get the public key:

open like before the private key with puttygen, the public key is under public key for pasting into OpenSSH authorized_keys file

Answer 4

I prepared a Docker container to make life simpler:

docker run --rm \
           --network=none \
           --volume=/path/to/file.ppk:/tmp/id_dsa.ppk \
           --volume=/path/to/output:/tmp/out/ \
           czerasz/putty-tools

Where:

• /path/to/file.ppk - local path to your ppk file
• /path/to/output - local path to where the private and public key should be placed