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Department of Computer Science

Technical Services and Support

Setting up Kerberos Support for your Home or Office Machine

This section may be of little interest to most people. It gives instructions on setting up Kerberos support for your home or office machine.

You can use Kerberos at home to let you SSH to our systems without typing a password. It’s for people who use our services and are willing to do some work configuring their home systems. 

Setting up Kerberos on Mac or Linux

There are a few steps to follow to set up Kerberos properly.

Note to Mac OSX users: You must use the MacPorts version of the MIT Kerberos utilities and OpenSSH + kerberos5. MacOSX, by default, is using Heimdal Kerberos, which is incompatible with our system.

These steps are as follows:

B. Set up Kerberos config file

The main config file for Kerberos is /etc/krb5.conf  [There is also a /opt/local/etc/krb5.conf on the Mac. The contents of the two files are merged with /etc/krb5.conf, which is coming first. Check both to make sure that you don’t have contradictory values.]

For Home Machine

For home use, where your IP address probably isn’t real because you’re behind an address translator run by your ISP or your home router. We have to use the https with kdcproxy to access Kerberos. So your krb5.conf should look like this:

[libdefaults]
default_realm = CS.RUTGERS.EDU
noaddresses = true
forwardable = true
renew_lifetime = 365d
default_ccache_name = /tmp/krb5cc_%{uid}

[realms]
CS.RUTGERS.EDU = {
kdc = https://services.cs.rutgers.edu/KdcProxy
http_anchors = FILE:/opt/local/etc/letsencrypt.pem
}
For Office Machine on CS Network

For machines on the CS network with a permanent address within Computer Science. A few things need to be done.

1. You’ll need to notify us to get your system registered. (Please see more detailed info about Integrating your system with LCSR Kerberos)

2. Tell us if you want to do NFS mounts of home directories,  /common/users, /common/home, and other NFS volumes.

Once staff have set you up, your krb5.conf should be set up as follows:

[libdefaults] 
  default_realm = CS.RUTGERS.EDU 
  noaddresses = true 
  forwardable = true 
  renew_lifetime = 365d 
  default_ccache_name = /tmp/krb5cc_%{uid} 
# following only for Macs in the office
  default_cc_name = /tmp/krb5cc_%{uid} 
[realms]
  CS.RUTGERS.EDU = {     
    kdc = krb1.cs.rutgers.edu:88     
    kdc = krb2.cs.rutgers.edu:88     
    kdc = krb4.cs.rutgers.edu:88 
}
C. Setup SSH client config to work with Kerberos Ticket

Ensure the following lines are present and not commented in /etc/ssh/ssh_config.  (On the Mac, using Macports version of OpenSSH +kerberos5, this will be in /opt/local/etc/ssh/ssh_config)  If the lines don’t exist, add them.

GSSAPIAuthentication yes
GSSAPIDelegateCredentials yes
D. Testing Your Kerberos setup

Once this is set up, you can use Kerberos commands:

    • kinit netid
      Sets up your Kerberos credentials. If your username at home is the same as your Rutgers netid, you can omit the netid
    • skinit netid
      if you have 2FA enabled on your account. skinit is a special script you need to create. Here are the skinit scripts.
      [Linux Version]
      #!/bin/bash
export PATH=/usr/bin:/bin
ANONCC=/tmp/anoncc$
curl -o $ANONCC https://services.cs.rutgers.edu/cgi-bin/anonticket.pl >/dev/null 2>&1
trap 'kdestroy -c "$ANONCC"' 2
kinit -T "$ANONCC" "$@"
STAT=$?
kdestroy -c "$ANONCC"
exit $STAT
[Mac version] 
#!/bin/bash
export PATH=/opt/local/bin:/usr/bin:/bin
ANONCC=/tmp/anoncc$ 
curl -o $ANONCC https://services.cs.rutgers.edu/cgi-bin/anonticket.pl >/dev/null 2>&1
trap 'kdestroy -c "$ANONCC"' 2 
kinit -T "$ANONCC" "$@"
STAT=$?
kdestroy -c "$ANONCC"
exit $STAT
    • klist
      Shows you your credentials. They will last for 24 hours. After that, you need to kinit again. Or you can do kinit -R before they expire to renew them for another day.
    • ssh hostname
      should work without asking you for a password as long as the host is in the computer science department. Note to Mac users: You must use the MacPorts version of the Kerberos utilities and OpenSSH +kerberos5.
    • If you asked staff to authorize you to mount directories for the machine on CS Network, do the following command to tell MacOS about our Kerberos domain. This only needs to be done once.

      sudo dscl . -create Config/NFSv4Domain RealName cs.rutgers.edu

      You can then mount the file systems you’re authorized to use, e.g.,

      sudo mount koko.lcsr.rutgers.edu:/vol/vol12/common/users /mnt

Setting up Kerberos on Windows 10.

On Windows 10, I recommend installing the Ubuntu application and setting up Kerberos within it, as with Linux. There is Kerberos for Windows, but it doesn’t support the proxy, so you can’t use it at home. Consider using MIT’s Kerberos for Windows if your PC is on a computer science department network with a permanent hostname and IP address.  To set up Ubuntu

  • Install WSL2 on Windows 10 OS Build 2004 or later by opening command.exe  (with Administrator permissions) and typing in the following command:

wsl.exe --install

Alternatively, you can also install  WSL using PowerShell as follows:

    • Find PowerShell (e.g., type PowerShell into the Contana box), right-click on it, and select “run as administrator.”
    • In the PowerShell windows, type Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux
  • Reboot
  • Go to the Windows store and install Ubuntu. (Other distributions will probably work, but I’ve tried Ubuntu.)
  • Now follow the Linux instructions above for Ubuntu.
  • You can open multiple Ubuntu windows. If you do kinit to get a ticket in one window, it will also apply to different windows.

For help with our systems or immediate assistance, visit LCSR Operator at CoRE 235 or call 848-445-2443. Otherwise, see CS HelpDesk. Don’t forget to include your NetID along with descriptions of your problem.