Cory's Forums

[clievers]

Let's say you frequently connect to a remote linux box. Normally you would do something like:
ssh user@remotehost
then you enter the password.

Well wouldn't it be nice to be able to just do
ssh user@remotehost
and then be connected, without having to enter a password, or just
ssh remotehost

Why would you want to do this? Well perhaps you can't remember those stinkin' passwords, or you use programs/applications that need to remotely connect and you don't want to display your password in clear text in a conf file. Also, you may remotely connect to a number of different machines, and therefore remembering all the passwords could again pose a problem.

To be able to connect remotely like mentioned above, you just have to set up a public and private key on your local computer and then add the public key to the remote computer.

Step 1:

Generate your key on the local computer using the ssh-keygen program:

[clievers]

Passwordless Authentication from Windows

Okay, so the passwordless authentication works fine from Linux -> Linux, but when you use Putty to connect from Windows, you still gotta enter the darn password. Here's how you can get around that and utilize passwordless authentication as well.

If you go to the putty download page, you will see there are also a couple of other programs "Pageant" and "PuTTYgen". Download these as well. (The putty documentation has more information you may want to look at).

So your first step is to run the PuTTYgen program. Select your appropriate options, for example "SSH2 RSA" and "1024" for bits. Then click the "Generate" button. Move your mouse around until it says it is generating your key. Enter a passphrase (twice) for the [private] key so as to make sure it's secured. Update the comment if necessary. Save both the public key and private key (there are buttons for each) to some place on your hard drive. Copy the big string of text under where it says "Public key for pasting into OpenSSH authorized_keys2 file:"

Open up your putty and connect to your remote box using regular user/password ssh, then edit your ~/.ssh/authorized_keys file and paste the big string you just copied. Ensure it's all on one new line. Save your file and exit.

Now, your ready to use all of this together to get the passwordless authentication going.

Method 1: is in your Configuration for your Putty Connection to the remote box, there is and "Auth" tab under "SSH". They give you the ability to browse to your private key (you just created and saved above). The problem with this, is you'll then be prompted for the private key's passphrase before it will authenticate. So it's not "really" passwordless anymore. The solution around this is Method 2.

Method 2: Remember that other file you downloaded, the Pageant file? Now that comes into play. If you double-click on it, it will open into your system tray. Here you can use the "Add Key" feature, browse to and find your private key you created/saved above, and it will prompt you for the passphrase. Once this is loaded, you can connect to your remote box using putty and passwordless authentication. To get more fancy, so you don't have to open the Pageant manually and load the key file, create yourself a batch file to run on windows startup/login. So, for example, in your My Documents, create a file called "startup.bat". In it, enter the following: