Stellar Turing Signing Server Reference Implementation

This TSS reference implementation employs two serverless services. Cloudflare workers and an AWS lambda function. The reason for this is that txFunctions are by their nature unsafe arbitrary Javascript functions. Cloudflare doesn't allow the execution of such functions thus we're splitting the workload between the much more performant and affordable Cloudflare workers and an AWS lambda function which will serve as our txFunction execution environment.

See below for specific instructions for setting up and running both services.

Wrangler (Cloudflare)

If you haven't already go ahead and signup for Cloudflare workers. You can attempt to run on their free tier but I highly suggest just biting the very affordable bullet and upgrading to their $5/mo plan which will allow you to scale much more nicely.

Next you should modify the wrangler.toml file to update my hard coded values with your own.

1. For the account_id go to the workers page on dash.cloudflare.com and copy your Account ID.
2. For kv_namespaces create four new kv namespaces via the wrangler cli:

$ npx wrangler kv:namespace create "META"
$ npx wrangler kv:namespace create "TX_FUNCTIONS"
$ npx wrangler kv:namespace create "TX_FEES"
$ npx wrangler kv:namespace create "TX_SPONSORS"

Each of those commands will spit out the object you should use to replace the existing values in the wrangler.toml file.

3. Finally for vars set STELLAR_NETWORK to either TESTNET or PUBLIC to toggle this Turret between using either the Test or Public Stellar network passphrases. For HORIZON_URL place in the url for the horizon service your Turret will consume. This should match with either the Test or Public network passphrase which you just set for the STELLAR_NETWORK variable. For TURRET_ADDRESS just use any valid, funded, Stellar account you privately own. This is the account into which fees will be paid as txFunctions are uploaded and run on your Turret. Next set TURRET_RUN_URL to null for now until we've got the Serverless AWS lambda setup with it's endpoint, at which point you'll update this value to that url. Finally set the XLM_FEE_MIN, XLM_FEE_MAX, UPLOAD_DIVISOR, and RUN_DIVISOR values to reasonable defaults. (For more info on these fee variables review the Fee Wiki.)

Now that the wrangler.toml file has been updated let's move to the stellar.toml file. This file is where you'll create your Turret's stellar.toml file particularly noting the [TSS].TURRETS array. This will be an array of other Turret addresses that you trust to cohost txFunctions with in the case of txFunction healing. For now just make sure to include your own TURRET_ADDRESS which you selected in the previous steps.

Once you've got that go ahead and upload it to the META kv store you instantiated earlier.

$ npx wrangler kv:key put --binding=META "STELLAR_TOML" ./stellar.toml --path

Make sure to run these wrangler commands from the ./wrangler directory

Finally to deploy the project run:

$ npm i
$ npm run deploy

From within the ./wrangler directory.

You may have to work through a few errors to get logged into your Cloudflare account but the wrangler cli errors are typically quite helpful. Feel free to update this README with more clear instructions as it's been ages since I started from scratch on my first wrangler project.

4. Once you've successfully got your project created and running upload a TURRET_SIGNER Stellar secret key to your Cloudflare worker.

$ npx wrangler secret put TURRET_SIGNER

When the dialog asks your for a value paste in a valid Stellar secret key. Most often this will be the secret key counterpart to your TURRET_ADDRESS but this isn't a requirement. This key is used to authenticate requests between your Cloudflare and Serverless services, nothing else.

Serverless (AWS)

Next we have the Serverless lambda endpoint which is hosted with AWS but deployed using the far more sane serverless.com cli tool. If you haven't go create both an AWS console account and a serverless.com account. Once you have those setup ensure you've got the serverless cli installed.

There's only two things you'll need to update in this repo in the serverless.yml file. The provider.environment.turretBaseUrl should be replaced with the worker base url which your wrangler service is hosted on. The provider.environment.turretSigner should be replaced with your Turret's TURRET_SIGNER public key set in the Wrangler setup. This connection is what secures and protects access between the Cloudflare and Serverless APIs. Remember Cloudflare gets the private key and Serverless gets the public key.

Now it'll be the fun task of getting:

$ npm i
$ npm run deploy

To successfully run from within the ./serverless directory. Follow any errors carefully and you should be able to get successfully deployed pretty quickly. The most probable issue will be you need to manually create an app in the Serverless dashboard and attach some new IAM credentials to it manually. There's a helpful UI walk through they have so you should be able to sort it out. Again feel free to update these docs with more clear instructions as you sort out the nuances of setting the Serverless service up.

When you finally get success on this task you'll be rewarded with an endpoint where your function is hosted. Copy that base url and paste it as the value for the TURRET_RUN_URL var back in the wrangler.toml file in the ./wrangler directory. Don't forget to redeploy that project after this update.

Congrats!

Assuming both npm run deploy's are now firing off without a hitch you should have a fully functional Turing Signing Server ready to participate in the TSS network delivering decentralized smart contracting functionality to anyone and everyone who chooses to use your Turret. Nice!

API Docs

Disclaimer

This is alpha software representing a reference implementation for the TSS protocol.

For this reason I strongly suggest either:
A) Leaving your STELLAR_NETWORK set to TESTNET
or B) Encouraging users to leave themselves as a majority signer on any controlled account they're attaching Turret signers to