Rebuilding an Admin Workstation USB

Note

These instructions refer to a SecureDrop instance using v2 onion services. If your instance uses v3 onion services and you need to rebuild your Admin Workstation, please contact FPF through the SecureDrop Support Portal.

In cases where an Admin Workstation USB stick has been lost or destroyed, and no backup exists, it is possible to rebuild one. In order to do so, you’ll need

  • physical access to the SecureDrop servers
  • 2 USB sticks:
    • Tails Master USB
    • 1 replacement Admin Workstation USB (USB3 and 16GB or better recommended)

The process requires experience with the Linux command line and Tails, and can take up to 3 hours. If a backup of the SecureDrop application server is available, reinstalling the instance may be simpler. An outline of the steps involved in rebuilding an Admin Workstation is as follows:

  1. Prepare the USB sticks.
  2. (Optional) Boot the Application and Monitor Server in single user mode and reset the shell admin account password.
  3. Set up SSH access for the new Admin Workstation.
  4. Retrieve SecureDrop configuration settings from the Application and Monitor Server.
  5. Back up and configure the SecureDrop application.
  6. Run the ./securedrop-admin tailsconfig and ./securedrop-admin install commands from the new Admin Workstation.
  7. Complete post-rebuild tasks.

Important

The rebuild process involves temporarily removing iptables rules on the Application and Monitor Servers, weakening their security. Because of this, it’s important to complete the rebuild process promptly, to avoid leaving the servers in an insecure state.

Step 1: Prepare the USB sticks

First, create a new Admin Workstation USB and set up a persistent volume with a strong passphrase.

Once persistence has been set up, start up the Admin Workstation with persistence enabled, install the SecureDrop application code, and set up the KeePassXC database.

The Admin Workstation uses SSH with key authentication to connect to the servers, so you’ll need to create a new SSH keypair for your SecureDrop instance. To do so, open a terminal by navigating to Applications ▸ System Tools ▸ Terminal, and run the following command:

ssh-keygen -t rsa -b 4096

When prompted to Enter file in which to save the key, Press Enter to use the default location. When prompted for a passphrase, it’s safe to leave it blank.

Step 2: (Optional) Boot the servers in single-user mode

If you do not have the original password for the shell admin account on the Application and Monitor Servers, you’ll need to reset the password on each server by booting in single user mode. In order to do so, you’ll need physical access to the server, a keyboard, and a monitor.

First, connect a monitor and keyboard to the Monitor Server. Then reboot the server. When the GRUB menu appears, make sure the Ubuntu entry is highlighted, and press e to edit boot options. In the boot options for Ubuntu, find the line that starts with linux and ends with ro. Add single after ro, separated by a space, and press F10 to boot in single user mode.

Reset the SecureDrop admin user’s password

Once the root prompt appears, you’ll need to reset the password for the SecureDrop admin user. By default this user is named sdadmin and has UID 1000. However it may have been named differently during the installation of your instance. You can use the command getent passwd 1000 to check the username corresponding to UID 1000. Once you have the correct username, reset its password using the passwd command, for example:

passwd sdadmin

Important

Make sure to select a strong password, and record it in the Admin Workstation’s KeePassXC database.

Finally, reboot the Monitor Server and verify that you can log in at the console using the new password.

Repeat the process for the Application Server. Use the same username and password as for the Monitor Server - this is required in order for the ./securedrop-admin install command to work correctly.

Step 3: Set up Admin Workstation access

Next, you’ll configure the servers to allow temporary SSH access from the new Admin Workstation.

First, start the new Admin Workstation with persistence enabled and an administration password set.

Next, connect the new Admin Workstation to the Hardware Firewall via the appropriate Ethernet port, and set up its static IP address. For more information on how to do so, see this section in the firewall setup documentation. If you do not know the correct static IP address for the Admin Workstation, and you are using a recommended pfSense-based Hardware Firewall, you can retrieve the address by loggging into its admin interface and checking the settings under Firewall ▸ Aliases.

Note

If you do not have login credentials for your pfSense firewall, check its user manual for instructions on resetting the administration password.

Next, determine whether your instance was set up to allow adminstrative access via SSH over Tor, or via SSH over LAN. If you don’t know which option was originally chosen, you can check as follows:

  1. Log in to the Application Server via the console using the adminstration username and password.
  2. Check to see if an SSH hidden proxy service exists, using the command sudo cat /var/lib/tor/services/ssh/hostname. If this file exists and includes an Onion URL and authorization token, your instance is set up to use SSH over Tor and you should configure temporary SSH access using these instructions. If not, your instance is set up to use SSH over LAN, and you should follow these instructions instead.

Configuring access for an SSH-over-Tor instance

Direct SSH access is disabled when the SSH-over-Tor option is selected during installation. To temporarily re-enable it, you’ll need to update iptables rules and change the sshd daemon’s configuration.

First, log on to the Application Server via the console, and run the following commands, substituting the Admin Workstation’s static IP for <admin_static_ip>:

sudo iptables -I INPUT -p tcp --dport 22 -s <admin_static_ip> \
  -m state --state NEW,ESTABLISHED -j ACCEPT
sudo iptables -I OUTPUT -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT

Next, edit the file /etc/ssh/sshd_config, changing the line:

ListenAddress 127.0.0.1:22

to:

ListenAddress 0.0.0.0:22

and deleting the line:

PasswordAuthentication no

Then, restart sshd using the command sudo service sshd restart.

Finally, check the file /etc/network/interfaces, and note down the network settings for the default Ethernet interface. You’ll need them in the next step.

Repeat the process above for the Monitor Server, making sure to note down its network settings as well.

Once the Monitor Server has been configured, proceed to enable access from the new Admin Workstation.

Configuring access for an SSH-over-LAN instance

First, log on to the Application Server via the console and edit the file /etc/ssh/sshd_config, deleting the line:

PasswordAuthentication no

Then, restart sshd using the command sudo service sshd restart.

Finally, check the file /etc/network/interfaces, and note down the network settings for the default Ethernet interface. You’ll need them in the next step.

Repeat the process above for the Monitor Server, making sure to note down its network settings as well.

Enabling access from the new Admin Workstation

From the Admin Workstation, open a terminal and copy the Admin Workstation’s SSH public key to the servers, substituting the values for the server administration username and server IP addresses in the commands below and entering the admin account’s password when prompted:

ssh-copy-id <admin-username>@<application-server-ip>
ssh-copy-id <admin-username>@<monitor-server-ip>

Next, create a file ~/.ssh/config with contents as below, again substituting the appropriate values for your servers:

Host app
  User <admin-username>
  Hostname <application-server-ip>
  ProxyCommand none

Host mon
  User <admin-username>
  Hostname <monitor-server-ip>
  ProxyCommand none

Finally, test direct SSH access from the terminal, using the commands ssh app and ssh mon. It should be possible to connect without entering a password.

Step 4: Retrieve SecureDrop configuration info from the servers

In addition to the account and networking information retrieved from the servers so far, you’ll need to retrieve the following files and info:

  • Tor Onion Service URLs and tokens
  • GPG Submission Public Key and OSSEC public key
  • OSSEC alert configuration details
  • (Optional) HTTPS configuration details

Retrieve Onion Service info

In order to connect to the onion services used by your instance, you will need to copy their details to the Admin Workstation. To do so, run the following commands from a Terminal window:

cd ~/Persistent/securedrop/install_files/ansible-base
echo "HidServAuth $(ssh app sudo cat /var/lib/tor/services/journalist/hostname)" \
   > app-journalist-aths
echo "$(ssh app sudo cat /var/lib/tor/services/source/hostname)" > app-source-ths

If your instance was set up to use SSH over TOR, you’ll also need to copy over the details of the SSH proxy onion services, by running the following commands:

echo "HidServAuth $(ssh app sudo cat /var/lib/tor/services/ssh/hostname)" > app-ssh-aths
echo "HidServAuth $(ssh mon sudo cat /var/lib/tor/services/ssh/hostname)" > mon-ssh-aths

Retrieve GPG Public Keys

There are 2 GPG public keys required by the instance configuration, that you will need to copy to the new Admin Workstation.

To copy the Submission Public Key, download it from the Source Interface and import it locally using the following commands:

cd ~/Persistent/securedrop/install_files/ansible-base
curl http://$(cat app-source-ths)/public-key > SecureDrop.asc
gpg --import SecureDrop.asc

Validate that the imported key’s fingerprint matches the one on your SecureDrop install. You can do this by first running the command:

gpg --with-fingerprint --import-options import-show --dry-run --import SecureDrop.asc

Then, compare the returned fingerprint value with that advertised by your Source Interface, using the command:

curl http://$(cat app-source-ths)/metadata

To copy the OSSEC Alert Public Key, first list available keys on the monitor server:

ssh mon sudo gpg --homedir=/var/ossec/.gnupg  -k

Look for the key corresponding to the destination email address for OSSEC alerts. Then, import it locally using the following commands (substituting the appropriate email address for alerts@example.com):

ssh mon sudo gpg --homedir=/var/ossec/.gnupg --export --armor alerts@example.com > ossec.pub
gpg --import ossec.pub

You will be prompted for the fingerprints for both keys during the next step. To view their fingerprints, use the command:

gpg -k --fingerprint

Retrieve OSSEC alert configuration details

In addition to the OSSEC alert GPG key you retrieved above, you’ll also need the following configuration information:

  • SMTP server
  • SMTP port
  • SASL username
  • SASL domain
  • SASL password

To retrieve these values, use the following command in the terminal:

ssh mon sudo cat /etc/postfix/sasl_passwd

This will return a line like:

[smtp.gmail.com]:587 testossec@gmail.com:AwfulPassword

In this example, smtp.gmail.com is the SMTP server, 587 is the SMTP port, testossec is the SASL username, gmail.com is the SASL domain, and AwfulPassword is the SASL password.

(Optional) Retrieve HTTPS certificate files

If your Source Interface was configured to use HTTPS, you will need to copy three related files from the Application Server to the Admin Workstation.

To retrieve these files, use the commands:

cd ~/Persistent/securedrop/install_files/ansible-base
ssh app sudo tar -c -C /var/lib ssl/  | tar xvf -

These commands will create a directory named ~/Persistent/securedrop/install_files/ansible-base/ssl on the Admin Workstation, containing your instance’s SSL certificate, certificate key, and chain file. When prompted for the names of these files during the next step, you should specify them relative to the install_files/ansible-base directory, i.e. as ssl/mydomain.crt.

Step 5: Configure and back up the application

Next, configure the application using the files and info retrieved in the previous steps. To do so, connect to the Tor network on the Admin Workstation, open a Terminal and run the following commands:

cd ~/Persistent/securedrop
./securedrop-admin setup
./securedrop-admin sdconfig

Note

The ./securedrop-admin setup command may take several minutes to complete, and may fail due to network issues. If it fails, it’s safe to run again.

When prompted, fill in the values retrieved in the previous steps.

Once complete, configure the Admin Workstation using the command:

./securedrop-admin tailsconfig

This will set up desktop shortcuts for the Source and Journalist Interfaces, and configure adminstrative access to the servers.

Once the ./securedrop-admin tailsconfig command is complete:
  • verify that the Hostname references in ~/.ssh/config have been updated to refer to Onion URLs instead of direct IP addresses,
  • verify that you can connect to the servers using ssh app and ssh mon, accepting the host verification prompt if necessary,
  • and verify that the desktop shortcuts for the Source and Journalist Interfaces work correctly, opening their respective homepages in Tor Browser.

Next, back up the servers by running the following command in the terminal:

./securedrop-admin backup

Step 6: Run the ./securedrop-admin install command

After the ./securedrop-admin backup command completes successfully, you should undo the changes made to enable temporary local SSH access, by running the following command:

./securedrop-admin install

Once the command completes successfully, your new Admin Workstation is ready for use. To revert the changes made to enable temporary local SSH access, you should reboot the servers, by issuing the following commands in a terminal:

ssh app sudo reboot
ssh mon sudo reboot

Step 7: Post-rebuild tasks

We recommend completing the following tasks after the rebuild:

  • Set up a new administration account on the Journalist Interface, by following these instructions

  • Verify that submissions can be decrypted, by going through the decryption workflow with a new submission.

  • Back up your Admin Workstation using the process documented here.

  • Delete invalid admin accounts in the Journalist Interface.

  • Restrict SSH access to the Application and Monitor Servers to valid Admin Workstions. If your new Admin Workstation USB stick is the only one that should have SSH access to the servers, you can remove access for any previous Admin Workstations from the terminal, using the commands:

    cd ~/Persistent/securedrop
./securedrop-admin reset_admin_access

    You can also selectively remove invalid keys by logging on to the Application and Monitor Servers and editing the file ~/.ssh/authorized_keys, making sure not to remove the public key belonging to your new Admin Workstation.

  • Optionally, set up daily journalist alerts, by running ./securedrop-admin sdconfig and providing a valid GPG key and fingerprint, along with the corresponding destination email address, then running ./securedrop-admin install again to update the server configuration.