Carrier-tx extension

package.json

@@ -31,6 +31,8 @@
     "ethers": "^5.4.2"
   },
   "dependencies": {
+    "@ethersproject/rlp": "^5.4.0",
+    "eciesjs": "^0.3.11",
     "ts-node": "^9.1.0",
     "typescript": "^4.1.2"
   }

src/index.ts

@@ -1,9 +1,11 @@
 import { BlockTag, TransactionReceipt, TransactionRequest } from '@ethersproject/abstract-provider'
 import { Networkish } from '@ethersproject/networks'
-import { BaseProvider } from '@ethersproject/providers'
+import { BaseProvider, TransactionResponse } from '@ethersproject/providers'
 import { ConnectionInfo, fetchJson } from '@ethersproject/web'
 import { BigNumber, ethers, providers, Signer } from 'ethers'
 import { id } from 'ethers/lib/utils'
+import { encode } from '@ethersproject/rlp'
+import { encrypt } from 'eciesjs'
 
 export const DEFAULT_FLASHBOTS_RELAY = 'https://relay.flashbots.net'
 
@@ -28,6 +30,12 @@ export interface FlashbotsOptions {
   revertingTxHashes?: Array<string>
 }
 
+export interface FlashbotsBundle {
+  signedBundledTransactions: Array<string>
+  blockTarget: number
+  options?: FlashbotsOptions
+}
+
 export interface TransactionAccountNonce {
   hash: string
   signedTransaction: string
@@ -352,7 +360,7 @@ export class FlashbotsBundleProvider extends providers.JsonRpcProvider {
   public async getBundleStats(bundleHash: string, blockNumber: number): Promise<GetBundleStatsResponse> {
     const evmBlockNumber = `0x${blockNumber.toString(16)}`
 
-    const params = [{bundleHash, blockNumber: evmBlockNumber}]
+    const params = [{ bundleHash, blockNumber: evmBlockNumber }]
     const request = JSON.stringify(this.prepareBundleRequest('flashbots_getBundleStats', params))
     const response = await this.request(request)
     if (response.error !== undefined && response.error !== null) {
@@ -415,6 +423,112 @@ export class FlashbotsBundleProvider extends providers.JsonRpcProvider {
     }
   }
 
+  /**
+   * Method to send a carrier tx into the public mempool
+   *
+   * @param bundle  FlashbotsBundle with AT LEAST signed bundled transactions in signedBundledTransactions field obtained
+   *  from {@link signBundle} method, and blockTarget.
+   * @param validatorPublicKey  The public key of the validator that will be able to decrypt the bundle and include it
+   *  into the bundle pool.
+   * @param signer  Signer who will sign the carrier transaction.
+   * @param carrierTx TransactionRequest whose data field will carry the encrypted bundle : MAY be an incomplete
+   *  object which will be populated with default values.
+   *
+   * @return Promise<TransactionResponse> Promise containing the response for the carrier tx
+   * */
+
+  public async sendCarrierTransaction(
+    bundle: FlashbotsBundle,
+    validatorPublicKey: string,
+    signer: Signer,
+    carrierTx: TransactionRequest
+  ): Promise<TransactionResponse> {
+    //RLP-serialize the given bundle
+    const serializedBundle = this.rlpSerializeBundle(bundle)
+
+    //Encrypt the encoded bundle with the passed validator pub_key
+    const encryptedBundle = encrypt(validatorPublicKey, Buffer.from(serializedBundle))
+
+    //Populate carrier_tx.data as : carrier_tx.data = MEV_Prefix | validator pub_key | Encrypt(validator pub_key, serialized bundle)
+    const mevPrefix = `0123` //this is a placeholder!
+
+    let payload = `0x`
+    payload += mevPrefix
+    payload += validatorPublicKey
+    payload += encryptedBundle.toString('hex')
+
+    carrierTx.data = payload
+
+    //Check if carrier_tx has minimum params, populate with defaults if not
+    /*
+     The following statement is intended to be used in order to support any type of incomplete TransactionRequest
+     received, populating it with default values if any one is missing
+     */
+    await this.populateCarrierTransaction(carrierTx, signer)
+
+    //Sign the transaction received as param with passed signer
+    const signedTx = await signer.signTransaction(carrierTx)
+
+    //Propagate carrier_tx into the public mempool and return Promise<TransactionResponse> for the carrier_tx
+    return this.genericProvider.sendTransaction(signedTx)
+  }
+
+  /**
+   * A private method to encode a FlashbotsBundle following the RLP serialization standard
+   * @param bundle the FlashbotsBundle instance to be serialized
+   * @return string the rlp encoded bundle
+   * @private
+   */
+  private rlpSerializeBundle(bundle: FlashbotsBundle): string {
+    if (bundle.signedBundledTransactions === undefined || bundle.signedBundledTransactions.length === 0)
+      throw Error('Bundle has no transactions')
+    if (bundle.options === undefined) bundle.options = {}
+
+    const fields = [
+      bundle.signedBundledTransactions,
+      this.formatNumber(bundle.blockTarget || 0),
+      this.formatNumber(bundle.options.minTimestamp || 0),
+      this.formatNumber(bundle.options.maxTimestamp || 0),
+      bundle.options.revertingTxHashes || []
+    ]
+    return encode(fields)
+  }
+
+  private formatNumber(num: number): string {
+    const hexNum = num.toString(16)
+    return hexNum.length % 2 === 0 ? `0x${hexNum}` : `0x0${hexNum}`
+  }
+
+  /**
+   * A private method to populate {@param carrier}'s missing fields with default values
+   * @param carrier an instance of TransactionRequest which will be the tx containing the full payload in its data field
+   * @param signer the signer Object which will send the carrier tx
+   * @private
+   */
+  private async populateCarrierTransaction(carrier: TransactionRequest, signer: Signer) {
+    if (!('to' in carrier)) throw Error('carrier.to field is missing')
+
+    if (carrier.gasPrice != null) {
+      const gasPrice = BigNumber.from(carrier.gasPrice)
+      const maxFeePerGas = BigNumber.from(carrier.maxFeePerGas || 0)
+      if (!gasPrice.eq(maxFeePerGas)) {
+        throw Error('carrier tx EIP-1559 mismatch: gasPrice != maxFeePerGas')
+      }
+    }
+    const latestBlock = await this.genericProvider.getBlock('latest')
+    const blocksInFuture = 5
+    const maxBaseFeeInFuture = FlashbotsBundleProvider.getMaxBaseFeeInFutureBlock(<BigNumber>latestBlock.baseFeePerGas, blocksInFuture)
+
+    carrier.type = 2
+    carrier.chainId = carrier.chainId || 1
+    carrier.nonce = carrier.nonce || (await this.genericProvider.getTransactionCount(signer.getAddress()))
+    carrier.maxPriorityFeePerGas = carrier.maxPriorityFeePerGas || ethers.utils.parseUnits('1.5', 'gwei')
+    carrier.maxFeePerGas = carrier.maxFeePerGas || maxBaseFeeInFuture.add(carrier.maxPriorityFeePerGas)
+    carrier.gasLimit = carrier.gasLimit || (await this.genericProvider.estimateGas(carrier))
+    carrier.value = carrier.value || 0
+    carrier.accessList = carrier.accessList || []
+  }
+
   private async request(request: string) {
     const connectionInfo = { ...this.connectionInfo }
     connectionInfo.headers = {
@@ -428,7 +542,10 @@ export class FlashbotsBundleProvider extends providers.JsonRpcProvider {
     return Promise.all(bundledTransactions.map((bundledTransaction) => this.genericProvider.getTransactionReceipt(bundledTransaction.hash)))
   }
 
-  private prepareBundleRequest(method: 'eth_callBundle' | 'eth_sendBundle' | 'flashbots_getUserStats' | 'flashbots_getBundleStats', params: RpcParams) {
+  private prepareBundleRequest(
+    method: 'eth_callBundle' | 'eth_sendBundle' | 'flashbots_getUserStats' | 'flashbots_getBundleStats',
+    params: RpcParams
+  ) {
     return {
       method: method,
       params: params,