Configuring a Public/Private Key Pair to Log into Linstat

Configuring a key pair requires a connection to Linstat. If you will be traveling we suggest configuring it before you leave the United States; otherwise you'll need to connect using VPN or Winstat once to set up the key pair.

No matter how you connect to Linstat, the process of creating a key pair is very much the same:

1. Generate a public/private key pair on your local computer

2. Add the key to  .ssh/authorized_keys  in your Linstat home directory

3. Configure the client program to use key authentication rather than passwords

This article has instructions for  SecureCRT  ,  PuTTY  , and  Mac/Linux  . (Recall that if you're connecting remotely and not using VPN you cannot use X-Win32.  SecureCRT  and  PuTTY  are good alternatives, though neither of them can display graphics without forwarding them to a separate program like X-Win32 or  Xming  .)

SecureCRT

In SecureCRT, click  Tools  ,  Create Public Key  .

Set the  Key type  to  DSA  .

Enter a password for the key or, even better, a  passphrase  , along with a comment. The comment could be used to remind you of the password, but must not allow others to guess it.

Set the  Key length in bits  to  1024  .

Select the  OpenSSH Key  format, and then save the keys in a convenient location on your local hard drive (the default location is probably OK).

Click  Yes  when asked if you want to use this as your global public key.

Now that the key has been generated it, use Notepad, TextPad or your favorite text editor and open  Identity.pub.  (The  .pub  extension indicates that this is the  public  key, to be shared with the server, rather than the  private  key which remains on your computer.)

If you are currently on the SSCC network save the file as  z:\.ssh\authorized_keys  . The  .ssh  folder is hidden by default, so you'll need to type its name rather than clicking on it.

If not, copy the entire contents of the file, log in to Linstat, then open  .ssh/authorized_keys  using your preferred Linux text editor (  pico  ,  emacs  ,  vi  , etc.).

Paste in the contents of the key, making sure it is all on one line, and save the file.

If you haven't already, log into Linstat. Then run the following command:

chmod g-w ~/.ssh/authorized_keys

(SSCC uses "user private groups" to make it easy to share files in project directories while keeping files in home directories private. Unfortunately the program that manages key pair connections doesn't understand user private groups and insists keys must not have group write permissions for security reasons.)

Next, open the session properties for your Linstat connection.

Under  Category  on the left, click  Connection  ,  SSH2  . Then select  PublicKey  in the  Authentication  section and click the up arrow until it is the top choice.

Click  OK  , and from now on when you log in to Linstat, you'll be prompted for your key passphrase rather than your SSCC password.

PuTTY

To create a public/private key pair in PuTTY, you need to run PuTTYgen. You can find it by searching or by clicking  Start  ,  All Programs  ,  PuTTY  ,  PuTTYgen  .

Set the type to  SSH-2 DSA  and click  Generate  .

You will be asked to generate randomness by moving your mouse around. Once the generation finishes, enter a password for the key or, even better, a  passphrase  , along with a comment. The comment could be used to remind you of the password, but must not allow others to guess it. Save both the public key and the private key in a convenient location on your local hard drive by clicking  Save public key  and  Save private key  . Then copy everything contained in the box  Public key for pasting into Open SSH authorized_keys file  .

If you are on the SSCC network, open Notepad, TextPad, or your favorite text editor, paste in the key and save it as  z:\.ssh\authorized_keys  . The  .ssh  folder is hidden by default, so you'll need to type its name rather than clicking on it.

If you are not on the SSCC network, log in to Linstat, then open  .ssh/authorized_keys  using your preferred Linux text editor (  pico  ,  emacs  ,  vi  , etc.), paste in the key, and save it. Either way, make sure the entire key is pasted onto one line.

If you haven't already, log into Linstat. Then run the following command:

chmod g-w ~/.ssh/authorized_keys

(SSCC uses "user private groups" to make it easy to share files in project directories while keeping files in home directories private. Unfortunately the program that manages key pair connections doesn't understand user private groups and insists keys must not have group write permissions for security reasons.)

Run PuTTY and load your previously saved Linstat profile.

Under  Category  on the left choose  Connection  ,  SSH  ,  Auth  . Then click  Browse  and find the private key you generated and saved.

Go back to  Session  to save the profile, then click  Open  . You'll be prompted for your key passphrase rather than your SSCC password.

Mac or Linux

On a Mac or Linux computer, open a terminal and run  ssh-keygen  . When it asks where to save the file press enter for the default location. Choose a password or, even better, a  passphrase. 

Then open the file  id_dsa.pub  using your favorite text editor and copy the contents. (The  .pub  extension indicates that this is the  public  key, to be shared with the server, rather than the  private  key which remains on your computer.)

Log in to Linstat, then open  .ssh/authorized_keys  using your preferred Linux text editor (  pico  ,  emacs  ,  vi  , etc.), paste in the key, and save it. Make sure the entire key is pasted onto one line.

Next run the following command:

chmod g-w ~/.ssh/authorized_keys

(SSCC uses "user private groups" to make it easy to share files in project directories while keeping files in home directories private. Unfortunately the program that manages key pair connections doesn't understand user private groups and insists keys must not have group write permissions for security reasons.)

The next time you connect you'll be prompted for the key passphrase, not your SSCC password.