Sublime Text with SFTP: SSH key file is ignored (Windows)

Question

I am using Sublime Text with the SFTP plugin. For my project I have set up a sftp-config.json file specifying the details necessary for the FTP connection. As long as I use a normal user/password login everything works fine and I can establish a connection.

However, I then tried to use an ssh key instead. My ssh key file is C:/Users/<username>/.ssh/id_rsa. When I manually run sftp on the power shell, a connection is successfully established.

PS C:\> sftp -i C:/Users/<username>/.ssh/id_rsa <username>@<host>
Connected to <username>@<host>.

Of course, username and host are replaced with my actual credentials.

Now, when trying to do the same using Sublime Text with the SFTP plugin, it does not work. Instead, when connecting I am prompted to enter my password like when not using an ssh key. I also made sure that it's not the password of the key it is asking (the key currently does not have a password) and just hitting enter without entering a password does not lead to success. It seems to me like the plugin simply ignored the fact that I have supplied an SSH key: If I enter my password for the FTP server, it does connect successfully, but of course that's not what I want.

I was thinking that I must have made a mistake in the configuration file, but I can not figure out what it should be. I also read the documentation online and it does not mention any additional steps that should be necessary. Here is my configuration file (with certain replacements of course):

{
    "type": "sftp",

    "save_before_upload": true,
    "upload_on_save": false,
    "sync_down_on_open": false,
    "sync_skip_deletes": false,
    "sync_same_age": true,
    "confirm_downloads": false,
    "confirm_sync": true,
    "confirm_overwrite_newer": false,

    "host": "<host>",
    "user": "<username>",
    "remote_path": "<remotepath>",
    "ignore_regexes": [
        "\\.sublime-(project|workspace)", "sftp-config(-alt\\d?)?\\.json",
        "sftp-settings\\.json", "/venv/", "\\.svn/", "\\.hg/", "\\.git/",
        "\\.bzr", "_darcs", "CVS", "\\.DS_Store", "Thumbs\\.db", "desktop\\.ini"
    ],
    "connect_timeout": 30,
    "ssh_key_file": "C:/Users/<username>/.ssh/id_rsa"
}

As an alternative approach I also tried specifying "sftp_flags": ["-i", "C:/Users/<username>/.ssh/id_rsa"] instead of using the ssh_key_file setting, but to no avail.

Has anyone got this to work and can give me a tip on what I am doing wrong?

Answer 1

I was able to identify the problem: The SFTP plugin for Sublime Text uses psftp (Putty sftp client) on Windows. Psftp doesn't work with OpenSSH keys because it uses a different format for the key file. Therefore, I had to convert my OpenSSH key to a PPK key using Puttygen (the Putty key generator). Using this tool I was able to load my key and convert it to a PPK file (choose Conversions > Import key from the menu and then then select Save private key). This key would then work with the Sublime Text plugin.