Crossposted from binarypatrick.dev
Introduction
The purpose of this backup process arose from a moment when I broke my phone. My phone was my lone source of MFA/2FA codes via the authenticator app, and I genuinely felt terror that I would be locked out of my Bitwarden account. After getting the phone working enough to log in and transfer my 2FA seed to another device, I decided to create this script to have a backup of my passwords locally.
Key requirements for this script are:
| Key | Reasoning |
|---|---|
| Secure | The script must run securely and its resulting output must also be secure |
| Testable | An untested backup is not a backup |
| Automatic | It should ideally run without human intervention, rain or shine |
Prerequisites
You will need unzip and cron simply to install the Bitwarden CLI.
sudo apt install unzip cron -y
Installing the Bitwarden CLI
Unfortunately it does not exist in the distro repo or flatpak. Though it is in snap, if you are interested in such things. I installed it manually through a handy script I wrote. It will make updating it manually later a bit easier it at least. Either way the CLI binary will need to be somewhere we can run it.
curl -L -o bw.zip "https://vault.bitwarden.com/download/?platform=linux&app=cli"
unzip bw.zip
sudo mv ./bw /usr/local/bin
rm bw.zip
Bitwarden User
Before we begin we will need to create a new user for running the script. This user will securely store the environment variables as well. Unfortunately even though we have the API key, Bitwarden still requires your vault password. I assume this is for actually decrypting the vault. To store them securely, I put them in the service user's ~/.bash_profile. This way only that user, and sudoers/root will have access and the job won't need to run as root. Obviously plaintext isn't ideal, but for the script to use it, it must be read somewhere. No amount of encryption would change that. Also note this machine should be isolated on your network from other services.
To create your user run the following:
sudo adduser \
--system \
--shell /bin/bash \
--group \
--disabled-password \
--home /home/bitwarden \
bitwarden
Bitwarden API Credentials
To get your API key log into your Bitwarden web vault. From the user menu in the upper right, go to Account Settings. Then on the left hand menu go to Security, then Keys in the top menu. This should bring you to Encryption Key Settings and at the bottom of the page API Key. Your account will only have one set of client ID/secret. Click View API Key to retrieve it. You'll need these values to add to the .bash_profile along with your vault password.
sudo touch /home/bitwarden/.bash_profile
sudo chmod 600 /home/bitwarden/.bash_profile
sudo nano /home/bitwarden/.bash_profile
export BW_CLIENTID="<your_client_id>"
export BW_CLIENTSECRET="<your_client_secret>"
export BW_PASSWORD="<your_vault_password"
export BW_NOTIFICATION_EMAIL="<your_notification_email_address>"
Setting up the Script
The script needs to be put somewhere the Bitwarden user can read it, and it needs to be set as executable.
REPO_BACKUP_SCRIPT=https://raw.githubusercontent.com/BinaryPatrick/BitwardenBackup/main/backup.sh
sudo curl -L -o /home/bitwarden/backup.sh $REPO_BACKUP_SCRIPT
sudo chown bitwarden /home/bitwarden/backup.sh
sudo chgrp bitwarden /home/bitwarden/backup.sh
sudo chmod 744 /home/bitwarden/backup.sh
The script also includes an email notification if the vault fails to unlock or authentication fails. You'll need to set up postfix to send email.
Adding to crontab
Now that the script is in place, we can add it to crontab. We need to do a little hand holding to make sure the crontab environment can see the bw binary, and will use the environment variables we configured. Also notice, our script requires an output directory to run. We'll set this to /home/bitwarden. Feel free to configure this to use a mounted share or something though. Remember the output is encrypted using the vault password so it is relatively safe to have on a restricted file share.
sudo su bitwarden
crontab -e
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
0 0 * * * BASH_ENV=/home/bitwarden/.bash_profile /bin/bash /home/bitwarden/backup.sh /home/bitwarden
Validate Decryption
An untested backup is no backup at all. Make sure to try and decrypt the file that is created using the decryption script once you have a backup. It should create a json file.
REPO_DECRYPTION_SCRIPT=https://raw.githubusercontent.com/BinaryPatrick/BitwardenBackup/main/decrypt.sh
sudo curl -L -o decrypt.sh $REPO_DECRYPTION_SCRIPT
sudo chmod +x decrypt.sh
When you run the script, pass the filename of the file you want to decrypt and you will be prompted for your vault password.
./decrypt.sh bw_export_xxxxxxxxxxxxxxx.enc
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