SME Server:Documentation:User Manual:Chapter1

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Revision as of 03:35, 28 September 2007 by Snoble (talk | contribs) (→‎Shell Access: info for users only)
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Chapter 1 - Access

Passwords

The user's password gives access to server login, file storage, email accounts and the like. If a user's password is lost the administrator can reset to a new value, but not retrieve the old one. Passwords must be sufficiently complex, with the rules controlled by the server administrator.

Users can reset their passwords at www.yourserver.net/user-password

For windows clients, If the server is the domain PDC the user can reset his password after issuing a Ctrl+Alt+Del, Note that windows error messages may not explain clearly enough that the user password isn't sufficiently complex.

VPN Access

To configure VPN access the administrator must configure PPTP.

  • First Admin must enable PPTP connections globally in the "Remote access" panel. Enter the number of concurrent PPTP connections that will be established. To disable all PPTP connections enter "0" (default).
  • Then Admin must enable VPN access for each user that will be allowed to connect via VPN to your SME Server. Use the "Users" panel to configure each user that requires VPN access.

To configure your VPN client, in Win XP, go to Networking in Control Panel. (New Connection Wizard)

  • Establish the connection from XP by double clicking the VPN icon for your connection & entering a valid SME user/password combination. Your connection to the Internet needs to be established first before you initiate the PPTP connection
  • It is suggested/advised you to use the same login name on your Windows PC as you use on sme, it's easier (& seamless) to deal with permissions for ibays etc that way.
  • When you then open up your Network Neighborhood window, you should see your server workgroup listed there. Alternatively, map a drive as required like:
net use M: \\192.168.1.1\ibayname

Template:DrawBoxNote

Shell Access

This is the preferred method of connecting to SME, as you can connect from any machine with an SSH Client. SSH is similar in function to Telnet, with the main difference being that it is heavily encrypted. It has many other very useful features, such as tunneling, which are outside the scope of this section of the manual.

Before a user can have shell access Admin must:

  • enable ssh access at server-manager -> Security -> Remote Access
  • then grant each user shell access:
chsh -s /bin/bash jim


SSH With Passwords

If your admin allows it you can connect with just a username and password.

Securing SSH With Public / Private Keys

If you need to get SSH access to your server from outside the LAN (e.g. you want to get to your work server from home) then the advised method is to use Public / Private Keys.

The Private Key is a file that sits on your client PC, and is sent by the SSH Client.
The Public Key sits on the SME server.

During Logon, the server runs a check to see if your Private Key corresponds to its stored Public key for the user that you are trying to log on as. If they don't match then the server simply drops the TCP session. There is no opportunity for a cracker to try brute forcing your root password.

Below are instructions on how to create the Public / Private key pair using windows and putty.

  • Create the Keys

Log onto the server, cd to ~/.ssh and enter the following command: 

cd ~/.ssh
ssh-keygen -t dsa

When asked if you want a passphrase, this is up to you. If you set one, then you will still be asked for a password after the key exchange. This is an extra level of security, just incase your private key falls into unwelcome hands. I Recommend that you set a strong password. Hit Enter when asked where to save the keys to.

You will now have two new files in the current Directory: id_dsa & id_dsa.pub

  • Activate the Public Key

Enter the following command to add the Public key to the list of allowed keys for root: 

cat id_dsa.pub >> authorized_keys
  • Get the Private Key

Now all we need to do is get the Private Key onto your client. If you are connected using ssh, then you can simply 

cat id_dsa

then copy & paste the output into a notepad file. Failing that, you can use SCP to get the file off, or move the file into an iBay and copy it out using SMB.

  • Convert the Private Key

Once you have the file on your windows machine, you need to convert it from OpenSSH Format to PPK (Putty Private Key) format. To do this you need PuttyGen. This is part of the Windows installation of Putty, but if you just downloaded the Putty.exe executable then you will need to visit http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html and download the PuttyGen executable. Run PuttyGen, select Conversions -> Import Key & open your OpenSSH PrivateKey. If you set a PassPhrase, you will be asked for it now. Once the Key is Imported, Click "Save Private Key" and save your new ppk file somewhere safe.

  • Use the Key & Test

Now when you use Putty, you just have to tell it to use the Private Key Put your Server IP address / FQDN in the main screen as normal, then go to //Connection -> SSH -> Auth// from the menu, and browse for the PPK file you created earlier. If you want, you can go back to Session, and save these settings.

Hit Login, and if your Keypair is working, you will see the following: 

Using username "root".
Authenticating with public key "imported-openssh-key"
Passphrase for key "imported-openssh-key":


  • As long as the above worked, the server Admin can now disable logging in using passwords.

Go to the Server-manager, and switch Off 'Allow secure shell access using standard passwords'

Further information at http://wiki.contribs.org/SSH_Public-Private_Keys

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