op-geth/cmd/faucet

Faucet

The faucet is a simplistic web application with the goal of distributing small amounts of Ether in private and test networks.

Users need to post their Ethereum addresses to fund in a Twitter status update or public Facebook post and share the link to the faucet. The faucet will in turn deduplicate user requests and send the Ether. After a funding round, the faucet prevents the same user from requesting again for a pre-configured amount of time, proportional to the amount of Ether requested.

Operation

The faucet is a single binary app (everything included) with all configurations set via command line flags and a few files.

First things first, the faucet needs to connect to an Ethereum network, for which it needs the necessary genesis and network infos. Each of the following flags must be set:

• -genesis is a path to a file containing the network genesis.json. or using:
  • -goerli with the faucet with Görli network config
  • -rinkeby with the faucet with Rinkeby network config
  • -sepolia with the faucet with Sepolia network config
• -network is the devp2p network id used during connection
• -bootnodes is a list of enode:// ids to join the network through

The faucet will use the les protocol to join the configured Ethereum network and will store its data in $HOME/.faucet (currently not configurable).

Funding

To be able to distribute funds, the faucet needs access to an already funded Ethereum account. This can be configured via:

• -account.json is a path to the Ethereum account's JSON key file
• -account.pass is a path to a text file with the decryption passphrase

The faucet is able to distribute various amounts of Ether in exchange for various timeouts. These can be configured via:

• -faucet.amount is the number of Ethers to send by default
• -faucet.minutes is the time to wait before allowing a rerequest
• -faucet.tiers is the funding tiers to support (x3 time, x2.5 funds)

Sybil protection

To prevent the same user from exhausting funds in a loop, the faucet ties requests to social networks and captcha resolvers.

Captcha protection uses Google's invisible ReCaptcha, thus the faucet needs to run on a live domain. The domain needs to be registered in Google's systems to retrieve the captcha API token and secrets. After doing so, captcha protection may be enabled via:

• -captcha.token is the API token for ReCaptcha
• -captcha.secret is the API secret for ReCaptcha

Sybil protection via Twitter requires an API key as of 15th December, 2020. To obtain it, a Twitter user must be upgraded to developer status and a new Twitter App deployed with it. The app's Bearer token is required by the faucet to retrieve tweet data:

• -twitter.token is the Bearer token for v2 API access
• -twitter.token.v1 is the Bearer token for v1 API access

Sybil protection via Facebook uses the website to directly download post data thus does not currently require an API configuration.

Miscellaneous

Beside the above - mostly essential - CLI flags, there are a number that can be used to fine-tune the faucet's operation. Please see faucet --help for a full list.