Self-hosted open-source multi-user multi-platform secret management

TLDR: Syncthing, KeePassXC, Keepass2Android, AuthPass, and WebDAV via Apache HTTP Server allow for self-hosted open-source multi-user multi-platform secret management.

This article describes the secrets management setup used by me and my family. This is not a tutorial, but rather an overview of the possibilities and what works for us.

The setup:

• is fully open source with Open Source Initiative-approved licenses
• is multi-platform, it supports macOS, Linux, Windows, iPhone, and Android
• is multi-user, you can share secrets
• is self-hosted with low maintenance
• supports passwords, TOTP, SSH keys and any other secret
• has browser support
• does not require tech-savvy family members (one is enough)

The tools

• KeePassXC for macOS, Linux, and Windows
• Keepass2Android for Android
• AuthPass for iPhone
• Syncthing and Syncthing on Android
• Apache HTTP Server with WebDAV

KeePassXC, Keepass2Android and AuthPass

These are three nice and complete apps that all support secret databases in the KeePass format. Although some variations exist, I have never experienced interoperability issues with these tools.

To use KeePassXC in the browser, you need a browser add-on. Many browsers are supported. Keepass2Android and AuthPass integrate well with the Android and iOS environments and don't require additional software.

Bonus features

Bonus feature 1: KeePassXC can also be used as an SSH-agent. This allows you to use SSH-keys as long as the KeePass database is unlocked. The SSH keys are synced along with all the other secrets. No more private key files on disk!

Bonus feature 2: if you ever lost a phone with Google Authenticator installed, you know how painful it is to set up 2FA with TOTP again. Configure TOTP in these apps instead, and that worry is gone.

Syncthing

Syncthing is an amazing program. It just continues to work with very little maintenance. It can synchronize multiple folders between multiple devices. Once a device is connected to another device, they automatically find each other over the internet.

Each person stores their main secrets database in a 'small' folder containing only the files they want to sync to their phone. This small folder is not shared between people. Then there are 'larger' folders that are optionally shared between multiple people. These larger folders are only synchronized between desktops and laptops and are a good place to store shared KeePass databases.

To ensure that all devices with Syncthing always stay in sync, it is a good idea to share all folders with a machine that is always on. Ideally the Syncthing port (22000) would be exposed directly to the internet. This reduces sync conflicts because it is more likely that all devices see the changes from the other devices.

Since you're going to create many folders, think about a naming convention. Our folders start with the name of the owner. The Syncthing folder name can be different from the directory in the file system. For example, the Syncthing folder could be named erik-documents while on my device the directory is called documents.

Even though there is a very nice Android application, Google has made it maddeningly difficult to publish to the Play store. So difficult even, that the maintainers have given up. Fortunately, you can still get a maintained fork via F-Droid or use one of the other install options.

Bonus features and tips

Bonus feature 1: Store all your documents in a Syncthing folder so that you can access them from multiple devices.

Bonus feature 2: Configure a Syncthing instance to keep older file versions. Now you have a backup too!

Bonus feature 3: Sync the camera folder on your Android phone.

Tip 1: Using Homebrew? The most convenient way to install Syncthing is with the command brew install --cask syncthing-app.

Tip 2: When starting a new Syncthing device, remove the default folder shared from directory ~/Sync. Instead, put the folders you're sharing below the ~/Sync directory.

Tip 3: Before you create any folder in Syncthing, change the folder default configuration to have the following ignore pattern. This is especially important when you use Apple devices.

(?d)**/.DS_Store
(?d).DS_Store
#include .syncthing-patterns.txt

Tip 4: All the GUIs of the locally running Syncthing instances have the same 'localhost' URL. Since the URL is the same, you should also use the same password. Otherwise, storing the password in KeepassXC becomes difficult.

Support iPhone with Apache HTTP Server and WebDAV

Due to limitations imposed by iOS (no background threads unless you are paid by Apple), Syncthing does not run on iPhones. Fortunately, we found AuthPass which supports reading from and writing to a WebDAV folder. AuthPass does this really well; if you make changes while being offline, it automatically merges those changes into the latest version of the remote database once you go online again!

Fortunately, we already have a Linux server running Apache HTTP Server that is always on. (The websites there are also synced with Syncthing.) By configuring a WebDAV folder in Apache HTTP Server (protected by a username/password), we can share a Syncthing folder with AuthPass. Each person with an iPhone will need their own WebDAV folder.

Sharing secrets with KeeShare

KeeShare is a KeePassXC feature that allows you to synchronize a shared KeePass database with your main database. Since the main database contains a complete copy of the shared database, you only need to set up KeeShare on one device. Other devices, including your mobile phone, do not require direct access to the shared database.

Since KeeShare is only supported in KeePassXC, you must periodically open KeePassXC. Otherwise, you will miss changes in the shared databases. Shared databases won't sync if you only use the KeePass database on your mobile phone.

Tip: Sharing secrets is limited; you can only share entire databases. Therefore, plan ahead and decide how you want to organize secrets. We settled on a shared database for the whole family, and another shared database for just me and my partner.
Since each shared KeePass database is password-protected, you can store them all in the same shared Syncthing folder. However, if you are sharing other things as well, you may want to create multiple Syncthing folders.

Maintenance

Sometimes two offline devices modify the same KeePass file. Later, Syncthing detects the conflict and stores multiple files, one for each conflicting edit. You can merge all the conflict files using the database merge feature in KeePassXC. After merging them into the main database, you can delete the conflict files. Unfortunately, there is no default way to detect the presence of these conflict files. I manually check the synced folders once every few months (or when I miss a secret!). If you build a detection script, please share!

Since Syncthing runs so quietly in the background, you won't notice when things go wrong. To prevent this, check the Syncthing UI every few months.

Not explored options

KeePassXC has a command-line interface. This could be useful for Linux servers or scripts.

Conclusion

We have used this setup for over four years and have found it to be user-friendly and low-maintenance. Even my teenager kids are fervent users. Despite losing several devices, our secrets have never been lost.