feat: Faucet (#2856)

This PR creates a small faucet application for retrieving eth.

# Checklist:
Remove the checklist to signal you've completed it. Enable auto-merge if
the PR is ready to merge.
- [ ] If the pull request requires a cryptography review (e.g.
cryptographic algorithm implementations) I have added the 'crypto' tag.
- [ ] I have reviewed my diff in github, line by line and removed
unexpected formatting changes, testing logs, or commented-out code.
- [ ] Every change is related to the PR description.
- [ ] I have
[linked](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue)
this pull request to relevant issues (if any exist).

.circleci/config.yml

@@ -465,6 +465,17 @@ jobs:
           name: "Build and test"
           command: build aztec-node | add_timestamps
 
+  aztec-faucet:
+    machine:
+      image: ubuntu-2204:2023.07.2
+    resource_class: large
+    steps:
+      - *checkout
+      - *setup_env
+      - run:
+          name: "Build and test"
+          command: build aztec-faucet | add_timestamps
+
   pxe-x86_64:
     machine:
       image: ubuntu-2204:2023.07.2
@@ -1263,6 +1274,11 @@ workflows:
             - yarn-project
           <<: *defaults
 
+      - aztec-faucet:
+          requires:
+            - yarn-project
+          <<: *defaults
+
       - pxe-x86_64:
           requires:
             - yarn-project

build_manifest.yml

@@ -113,6 +113,12 @@ aztec-sandbox:
   dependencies:
     - yarn-project
 
+aztec-faucet:
+  buildDir: yarn-project
+  projectDir: yarn-project/aztec-faucet
+  dependencies:
+    - yarn-project
+
 pxe:
   buildDir: yarn-project
   projectDir: yarn-project/pxe

yarn-project/aztec-faucet/.dockerignore

@@ -0,0 +1,4 @@
+data
+dest
+node_modules
+Dockerfile

yarn-project/aztec-faucet/.eslintrc.cjs

@@ -0,0 +1 @@
+module.exports = require('@aztec/foundation/eslint');

yarn-project/aztec-faucet/.gitignore

@@ -0,0 +1 @@
+/data*

yarn-project/aztec-faucet/Dockerfile

@@ -0,0 +1,14 @@
+FROM 278380418400.dkr.ecr.eu-west-2.amazonaws.com/yarn-project AS builder
+
+WORKDIR /usr/src/yarn-project/aztec-faucet
+
+# Productionify. See comment in yarn-project-base/Dockerfile.
+RUN yarn cache clean && yarn workspaces focus --production
+
+# Create final, minimal size image.
+FROM node:18-alpine
+COPY --from=builder /usr/src/ /usr/src/
+WORKDIR /usr/src/yarn-project/aztec-faucet
+ENTRYPOINT ["yarn"]
+CMD [ "start" ]
+EXPOSE 8080

yarn-project/aztec-faucet/README.md

@@ -0,0 +1,3 @@
+# Aztec Faucet
+
+This application allows someone to obtain a small amount of eth via a http endpoint.

yarn-project/aztec-faucet/package.json

@@ -0,0 +1,61 @@
+{
+  "name": "@aztec/aztec-faucet",
+  "version": "0.1.0",
+  "main": "dest/bin/index.js",
+  "type": "module",
+  "bin": "./dest/bin/index.js",
+  "typedocOptions": {
+    "entryPoints": [
+      "./src/bin/index.ts"
+    ],
+    "name": "Aztec Faucet",
+    "tsconfig": "./tsconfig.json"
+  },
+  "scripts": {
+    "start": "node --no-warnings ./dest/bin",
+    "build": "yarn clean && tsc -b",
+    "build:dev": "tsc -b --watch",
+    "clean": "rm -rf ./dest .tsbuildinfo",
+    "formatting": "run -T prettier --check ./src && run -T eslint ./src",
+    "formatting:fix": "run -T prettier -w ./src",
+    "test": "NODE_NO_WARNINGS=1 node --experimental-vm-modules $(yarn bin jest) --passWithNoTests"
+  },
+  "inherits": [
+    "../package.common.json"
+  ],
+  "jest": {
+    "preset": "ts-jest/presets/default-esm",
+    "moduleNameMapper": {
+      "^(\\.{1,2}/.*)\\.m?js$": "$1"
+    },
+    "testRegex": "./src/.*\\.test\\.(js|mjs|ts)$",
+    "rootDir": "./src"
+  },
+  "dependencies": {
+    "@aztec/ethereum": "workspace:^",
+    "@aztec/foundation": "workspace:^",
+    "koa": "^2.14.2",
+    "koa-cors": "^0.0.16",
+    "koa-router": "^12.0.0",
+    "viem": "^1.2.5"
+  },
+  "devDependencies": {
+    "@jest/globals": "^29.5.0",
+    "@rushstack/eslint-patch": "^1.1.4",
+    "@types/jest": "^29.5.0",
+    "@types/node": "^18.7.23",
+    "jest": "^29.5.0",
+    "ts-jest": "^29.1.0",
+    "ts-node": "^10.9.1",
+    "typescript": "^5.0.4"
+  },
+  "files": [
+    "dest",
+    "src",
+    "!*.test.*"
+  ],
+  "types": "./dest/index.d.ts",
+  "engines": {
+    "node": ">=18"
+  }
+}

yarn-project/aztec-faucet/src/bin/index.ts

@@ -0,0 +1,153 @@
+#!/usr/bin/env -S node --no-warnings
+import { NULL_KEY, createEthereumChain } from '@aztec/ethereum';
+import { EthAddress } from '@aztec/foundation/eth-address';
+import { createDebugLogger } from '@aztec/foundation/log';
+
+import http from 'http';
+import Koa from 'koa';
+import cors from 'koa-cors';
+import Router from 'koa-router';
+import { Hex, http as ViemHttp, createWalletClient, parseEther } from 'viem';
+import { privateKeyToAccount } from 'viem/accounts';
+
+const {
+  FAUCET_PORT = 8082,
+  API_PREFIX = '',
+  API_KEY = '',
+  RPC_URL = '',
+  CHAIN_ID = '',
+  PRIVATE_KEY = '',
+  INTERVAL = '',
+  ETH_AMOUNT = '',
+} = process.env;
+
+const logger = createDebugLogger('aztec:faucet');
+
+const rpcUrl = RPC_URL;
+const apiKey = API_KEY;
+const chainId = +CHAIN_ID;
+const privateKey: Hex = PRIVATE_KEY ? createHex(PRIVATE_KEY) : NULL_KEY;
+const interval = +INTERVAL;
+const mapping: { [key: Hex]: Date } = {};
+
+/**
+ * Helper function to convert a string to a Hex value
+ * @param hex - The string to convert
+ * @returns The converted value
+ */
+function createHex(hex: string) {
+  return `0x${hex.replace('0x', '')}` as Hex;
+}
+
+/**
+ * Function to throttle drips on a per address basis
+ * @param address - Address requesting some ETH
+ */
+function checkThrottle(address: Hex) {
+  if (mapping[address] === undefined) {
+    return;
+  }
+  const last = mapping[address];
+  const current = new Date();
+  const diff = (current.getTime() - last.getTime()) / 1000;
+  if (diff < interval) {
+    throw new Error(`Not funding address ${address}, please try again later`);
+  }
+}
+
+/**
+ * Helper function to send some ETH to the given address
+ * @param address - Address to receive some ETH
+ */
+async function transferEth(address: string) {
+  const chain = createEthereumChain(rpcUrl, apiKey);
+
+  const account = privateKeyToAccount(privateKey);
+  const walletClient = createWalletClient({
+    account: account,
+    chain: chain.chainInfo,
+    transport: ViemHttp(chain.rpcUrl),
+  });
+  const hexAddress = createHex(address);
+  checkThrottle(hexAddress);
+  try {
+    const hash = await walletClient.sendTransaction({
+      account,
+      to: hexAddress,
+      value: parseEther(ETH_AMOUNT),
+    });
+    mapping[hexAddress] = new Date();
+    logger.info(`Sent ${ETH_AMOUNT} ETH to ${hexAddress} in tx ${hash}`);
+  } catch (error) {
+    logger.error(`Failed to send eth to ${hexAddress}`);
+    throw error;
+  }
+}
+
+/**
+ * Creates a router for the faucet.
+ * @param apiPrefix - The prefix to use for all api requests
+ * @returns - The router for handling status requests.
+ */
+function createRouter(apiPrefix: string) {
+  logger.info(`Creating router with prefix ${apiPrefix}`);
+  const router = new Router({ prefix: `${apiPrefix}` });
+  router.get('/status', (ctx: Koa.Context) => {
+    ctx.status = 200;
+  });
+  router.get('/drip/:address', async (ctx: Koa.Context) => {
+    const { address } = ctx.params;
+    await transferEth(EthAddress.fromString(address).toChecksumString());
+    ctx.status = 200;
+  });
+  return router;
+}
+
+/**
+ * Create and start a new Aztec Node HTTP Server
+ */
+async function main() {
+  logger.info(`Setting up Aztec Faucet...`);
+
+  const chain = createEthereumChain(rpcUrl, apiKey);
+  if (chain.chainInfo.id !== chainId) {
+    throw new Error(`Incorrect chain id, expected ${chain.chainInfo.id}`);
+  }
+
+  const shutdown = () => {
+    logger.info('Shutting down...');
+    process.exit(0);
+  };
+
+  process.once('SIGINT', shutdown);
+  process.once('SIGTERM', shutdown);
+
+  const app = new Koa();
+  app.on('error', error => {
+    logger.error(`Error on API handler: ${error}`);
+  });
+  const exceptionHandler = async (ctx: Koa.Context, next: () => Promise<void>) => {
+    try {
+      await next();
+    } catch (err: any) {
+      logger.error(err);
+      ctx.status = 400;
+      ctx.body = { error: err.message };
+    }
+  };
+  app.use(exceptionHandler);
+  app.use(cors());
+  const apiRouter = createRouter(API_PREFIX);
+  app.use(apiRouter.routes());
+  app.use(apiRouter.allowedMethods());
+
+  const httpServer = http.createServer(app.callback());
+  httpServer.listen(+FAUCET_PORT);
+  logger.info(`Aztec Faucet listening on port ${FAUCET_PORT}`);
+  await Promise.resolve();
+}
+
+main().catch(err => {
+  logger.error(err);
+  process.exit(1);
+});