Configuring MacPorts Kerberos for Duo Authentication

Below are some helpful guidelines for configuring MacPorts Kerberos for Duo authentication on a Mac OS 10.8 or later...

Also see How do I login to MIT services that leverage Duo two-factor authentication?

Installing MacPorts Kerberos and OpenSSH on Mac OS 10.8+

Step 1:  Install Xcode command line tools

• Launch Terminal.app
• In Terminal, type:

  xcode-select --install

• In the pop-up window, click on Install
• Once complete, verify that you have installed the needed components by typing:

  gcc --version

  Output should look something like this, depending on OS version:

  placebo@B12H87RFNE5L ~ % gcc --version
  Apple clang version 14.0.0 (clang-1400.0.29.202)
  Target: x86_64-apple-darwin22.1.0
  Thread model: posix
  InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Step 2:  Install MacPorts

• Visit The MacPorts Project.
• Download the package corresponding to your OS release and install it.
• Once installed, open a new Terminal and type:

  type port

  You will see:

  placebo@B12H87RFNE5L ~ % type port
  port is hashed

Step 3:  Install necessary ports

• From Terminal.app, open a privileged shell by typing the command below in Terminal and providing the admin password for the logged in user:

  sudo -s

• Your prompt should change from...

  placebo@B12H87RFNE5L ~ % sudo -s

  to

  root@B12H87RFNE5L ~ #

• Type the following:

  port selfupdate

  Let it run. It will take a few minutes.

• Then type:

  port install kerberos5 +universal

• Then type:

  port install openssh +kerberos5

  This may take a half-hour to run.

• Then type:

  exit

• Close and re-open your Terminal, then type:

  which kinit; which ssh

  This should report both commands in /opt/local/bin/.

Step 4:  Install MIT Kerberos Extras for Macintosh package if not already installed

• Available from the IS&T Software Grid

Step 5:  Configure OpenSSH

• Create ssh directory: mkdir ~/.ssh/
• Execute the following command to add "GSSAPIAuthentication yes" to ~/.ssh/config for the user:

Step 6:  Test!

On MacOS Big Sur and later, you need to explicitly configure where the ticket cache is; in .bashrc, either export KRB5CCNAME=KCM:uid (to use the built in ticket cache) or export KRB5CCNAME=/tmp/tkt_username (a valid file name)

• User should now be able to kinit username/root at Terminal prompt and be prompted for both password
  and Duo authentication

If your root instance is not working after following these steps, please move the directories for MacPorts (/opt/local/bin and /opt/local/sbin) to the front of your PATH so that they are evaluated first.

If it's still not working after moving the directories for MacPorts, please add 'Host *' above 'GSSAPIAuthentication yes' in the ~/.ssh/config file.