Caravan - Stateless Multisig Coordinator

Caravan is making bitcoin multisig custody easier and safer through transparency and standards.

Caravan is a coordination software. It connects to a source of consensus and your keys to build and interact with multisig bitcoin addresses.

Caravan is also stateless. It does not itself store any data. You must safekeep the addresses (and redeem scripts & BIP32 paths) you create.

Try Caravan now!

Installation

Caravan is a stateless pure HTML & JavaScript web application. It can be run in any web browser from a local or remote installation.

Unchained Capital GitHub

The simplest way to use Caravan is to visit https://unchained-capital.github.io/caravan, a copy of Caravan hosted on GitHub by Unchained Capital.

Your Own GitHub

If you would prefer to host your own copy of Caravan on GitHub, you can do so by first forking the Caravan repository into your own GitHub organization. You should see a copy of the Caravan web application at https://YOUR_GITHUB_USERNAME.github.io/caravan.

If not, go to the (newly forked) repository's "Settings" page and scroll down to the "GitHub Pages" section. Ensure you see a message saying "Your site is published at ...".

Host Locally

You can always clone the source code of Caravan to your local machine and run it from there. You will require a recent npm installation.

$ git clone https://github.com/unchained-capital/caravan
...
$ cd caravan
$ npm install
...
$ npm start
...

Now visit https://localhost:3000 to interact with your local copy of Caravan.

Host Remotely

Once you have downloaded the source code and used npm to install dependences (see section above), you can pre-build the React application for a production deployment and then host the contents of the resulting build directory via a webserver such as nginx.

$ npm run build
...

Usage

If you can access the Caravan web application in your browser, you are ready to start using Caravan.

Click the Create or Interact links in the navbar to get started.

See our YouTube playlist for some tutorial videos.

Keys

Caravan can connect to several different hardware wallets and key management software.

• Trezor One (installing the Trezor Bridge is required to interact with a Trezor device)

• Ledger Nano S

• Hermit

Caravan also accepts public keys and signatures as text so any wallet which can export these data can be made to work with Caravan.

Consensus

By default, Caravan uses a free API provided by blockstream.info whenever it needs information about the bitcoin blockchain or to broadcast transactions.

You can ask Caravan to use your own private bitcoind full node.

Adding CORS Headers

When asking Caravan to use a private bitcoind node you may run into CORS issues. This is because bitcoin-core does not natively support CORS headers. Because of how caravan is designed, CORS headers are essential to protecting the security of your coins and you will need to add the appropriate headers.

To correct this problem, you must add appropriate access control headers to your node's HTTP responses. When running Caravan on your local machine, for example, you may need to set Access-Control-Allow-Origin: https://localhost:3000.

This can be done using a webserver such as nginx or Apache, a proxy tool such as mitmproxy, or even just a script.

A particularly simple way to proxy requests to a private bitcoind node is to make use of nginx. Instructions to install and run the program are on its download page.

Explicitly, install nginx with

# MacOS
brew install nginx

# Debian Linux
sudo apt install nginx

Copy the server conifiguration file, bitcoind.proxy, to the appropriate location with the following commands. Note, these commands assume that you are in the base caravan directory. An example configuration file is included with the caravan source code called bitcoind.proxy which will, by defualt, enable a mainnet proxy. The testnet proxy is included, but is commented out.

# MacOS
mkdir -p /usr/local/etc/nginx/sites-available
cp bitcoind.proxy /usr/local/etc/nginx/sites-available/
ln -s /usr/local/etc/nginx/sites-available/bitcoind.proxy /usr/local/etc/nginx/servers/bitcoind.proxy

# Debain Linux
sudo mkdir -p /etc/nginx/sites-available
sudo cp bitcoind.proxy /etc/nginx/sites-available/
sudo ln -s /etc/nginx/sites-available/bitcoind.proxy /etc/nginx/sites-enabled/bitcoind.proxy

Different linux distributions follow different conventions for the /etc/nginx/ directory structure. As an example, MacOS uses etc/nginx/servers and Debian distributions use /etc/nginx/sites-enabled/ for the website configuration files. You will need to check the /etc/nginx/nginx.conf file to see what the convention is. This snipet is from a machine using Ubuntu 18.04 LTS. Note the two directories that are included. Whereas on MacOS there is only one include directory, include servers/*;.

http {
  ...
  ##
  # Virtual Host Configs
  ##

  include /etc/nginx/conf.d/*.conf;
  include /etc/nginx/sites-enabled/*;
}

Arch Linux provides more details on how to configure nginx for that distribution. It may be as simple as adding include /etc/nginx/sites-enabled/*; in the http block of /etc/nginx/nginx.conf and then:

sudo mkdir -p /etc/nginx/sites-enabled
sudo ln -s /etc/nginx/sites-available/bitcoind.proxy /etc/nginx/sites-enabled/bitcoind.proxy

Check that everything is copied correctly, properly configured, and that there are no errors in the syntax:

$ nginx -t
nginx: the configuration file /usr/local/etc/nginx/nginx.conf syntax is ok
nginx: configuration file /usr/local/etc/nginx/nginx.conf test is successful

Start nginx

# MacOS
brew services start nginx
# or if nginx is already running
brew services reload nginx

# Debain Linux
sudo systemctl start nginx
# or if nginx is already running
sudo systemctl restart nginx

On MacOS, starting the nginx daemon will prompt a popup window asking if you want ngingx to allow incoming network connections, which you will want to allow.

Test the different ports where my_uname is the user specified in the bitcoin.conf line rpcauth=my_uname: (Don't use this username!):

# Test that bitcoin rpc is functioning correctly
curl --user my_uname --data-binary \
'{"jsonrpc": "1.0", "id":"curltest", "method": "getblockcount", "params": [] }' \
-H 'content-type: text/plain;' http://127.0.0.1:8332
# Test the nginx reverse proxy
curl --user my_uname --data-binary \
'{"jsonrpc": "1.0", "id":"curltest", "method": "getblockcount", "params": [] }' \
-H 'content-type: text/plain;' --resolve bitcoind.localhost:8080:127.0.0.1 http://bitcoind.localhost:8080

Both tests should result in the same output with the current block height, e.g.

{"result":668255,"error":null,"id":"curltest"}

If you are running a bitcoind node on the same machine as Caravan, on port 8332, and you run nginx with the default settings, you should be able to point Caravan at 'http://bitcoind.localhost:8080' to communicate with your node. If you have bitcoind running on a different machine, you will need to adjust the upstream block in bitcoind.proxy for the correct network address:port. Don't forget to add the the correct rpcallowip=LOCAL_MACHINE_IP to the remote machine's bitcoin.conf.

Because the nginx configuration depends entirely on what is specified in the upstream block it is STRONGLY reccommended to keep bitcoind reserved for the mainnet and testnet for the testnet. In this way, nginx could be configured to simultaneously provide a reverse proxy to the mainnet via 'http://bitcoind.localhost:8080' and to the testnet via 'http://testnet.localhost:8080'.

mainnet nginx template

upstream bitcoind {
  server 127.0.0.1:8332;
}

server {
  listen 8080;
  server_name bitcoind.localhost;

  location / {
    ...
    proxy_pass http://bitcoind;
    ...
  }
}

testnet nginx template

upstream testnet {
  server 127.0.0.1:18332;
}

server {
  listen 8080;
  server_name testnet.localhost;

  location / {
    ...
    proxy_pass http://testnet;
    ...
  }
}

Adding CORS Headers (Deprecated)

A particularly simple way to proxy requests to a private bitcoind node is to make use of the corsproxy npm module. Instructions to install and run the module are on its home page. corsproxy has not been updated in a number of years and will require an earlier version of node to function properly.

Explicitly, install corsproxy with

npm install -g corsproxy

and then launch corsproxy

$ corsproxy
[log,info], data: CORS Proxy running at: http://localhost:1337
...

If you are running a bitcoind node on the same machine as Caravan, on port 8332, and you run corsproxy with the default settings, you should be able to point Caravan at 'http://localhost:1337/localhost:8332' to communicate with your node. A testnet node would be running on a different port, for example: http://localhost:1337/localhost:18332, and you would need to point Caravan to that URL instead.

Finally, a testnet/regtest node running on a different machine but still on the same network might be accessible to you via http://localhost:1337/192.168.0.22:18332, but you need to make sure the ports are open and accessible. It should be clear at this point that if corsproxy is running, paste your node's IP:port on the end of the corsproxy URL: http://localhost:1337/

Contributing

Please see the CONTRIBUTING.md and the open GitHub Issues