Skip to main content

Perform executions on a MetaMask user's behalf

The Delegation Toolkit supports ERC-7715, which lets you request fine-grained permissions from a MetaMask user to execute transactions on their behalf. For example, a user can grant your dapp permission to spend 10 USDC per day to buy ETH over the course of a month. Once the permission is granted, your dapp can use the allocated 10 USDC each day to purchase ETH directly from the MetaMask user's account.

In this guide, you'll request an ERC-20 periodic transfer permission from a MetaMask user to transfer 1 USDC every day on their behalf.

Prerequisites​

1. Set up a Wallet Client​

Set up a Viem Wallet Client using Viem's createWalletClient function. This client will help you interact with MetaMask Flask.

Then, extend the Wallet Client functionality using erc7715ProviderActions. These actions enable you to request ERC-7715 permissions from the user.

import { createWalletClient, custom } from "viem";
import { erc7715ProviderActions } from "@metamask/delegation-toolkit/experimental";

const walletClient = createWalletClient({
  transport: custom(window.ethereum),
}).extend(erc7715ProviderActions());

2. Set up a Public Client​

Set up a Viem Public Client using Viem's createPublicClient function. This client will help you query the account state and interact with blockchain network.

import { createPublicClient, http } from "viem";
import { sepolia as chain } from "viem/chains";
 
const publicClient = createPublicClient({
  chain,
  transport: http(),
});

3. Set up a session account​

Set up a session account which can either be a smart account or an externally owned account (EOA) to request ERC-7715 permissions. This account is responsible for executing transactions on behalf of the user.

import { privateKeyToAccount } from "viem/accounts";
import { 
  toMetaMaskSmartAccount, 
  Implementation 
} from "@metamask/delegation-toolkit";

const privateKey = "0x...";
const account = privateKeyToAccount(privateKey);

const sessionAccount = await toMetaMaskSmartAccount({
  client: publicClient,
  implementation: Implementation.Hybrid,
  deployParams: [account.address, [], [], []],
  deploySalt: "0x",
  signer: { account },
});

4. Request ERC-7715 permissions​

Request ERC-7715 permissions from the user. In this example, you'll request an ERC-20 periodic permission using the grantPermissions method.

import { sepolia as chain } from "viem/chains";

// Since current time is in seconds, we need to convert milliseconds to seconds.
const currentTime = Math.floor(Date.now() / 1000);
// 1 week from now.
const expiry = currentTime + 604800;

// USDC address on Ethereum Sepolia.
const tokenAddress = "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238";

const grantedPermissions = await walletClient.grantPermissions([{
  chainId: chain.id,
  expiry,
  signer: {
    type: "account",
    data: {
      address: sessionAccount.address,
    },
  },
  permission: {
    type: "erc20-token-periodic",
    data: {
      tokenAddress,
      // 1 USDC in WEI format. Since USDC has 6 decimals, 10 * 10^6
      periodAmount: 1000000n,
      // 1 day in seconds
      periodDuration: 86400,
      justification?: "Permission to transfer 1 USDC every day",
    },
  },
}]);

5. Set up a Viem client​

Set up a Viem client depending on your session account type.

For a smart account, set up a Viem Bundler Client using Viem's createBundlerClient function. This lets you use the bundler service to estimate gas for user operations and submit transactions to the network.

For an EOA, set up a Viem Wallet Client using Viem's createWalletClient function. This lets you send transactions directly to the network.

The toolkit provides public actions for both of the clients which can be used to redeem ERC-7715 permissions, and execute transactions on a user's behalf.

import { createBundlerClient } from "viem/account-abstraction";
import { erc7710BundlerActions } from "@metamask/delegation-toolkit/experimental";

const bundlerClient = createBundlerClient({
  client: publicClient,
  transport: http("https://your-bundler-rpc.com"),
  // Allows you to use the same Bundler Client as paymaster.
  paymaster: true
}).extend(erc7710BundlerActions());

6. Redeem ERC-7715 permissions​

The session account can now redeem the delegation. The redeem transaction is sent to the DelegationManager contract, which validates the delegation and executes actions on the user's behalf.

To redeem the permissions, use the appropriate client action based on your session account type:

import { calldata } from "./config.ts";

// These properties must be extracted from the permission response.
const permissionsContext = grantedPermissions[0].context;
const delegationManager = grantedPermissions[0].signerMeta.delegationManager;
const accountMetadata = grantedPermissions[0].accountMeta;

// USDC address on Ethereum Sepolia.
const tokenAddress = "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238";

// Calls without permissionsContext and delegationManager will be executed 
// as a normal user operation.
const userOperationHash = await bundlerClient.sendUserOperationWithDelegation({
  publicClient,
  account: sessionAccount,
  calls: [
    {
      to: tokenAddress,
      data: calldata,
      permissionsContext,
      delegationManager,
    },
  ],
  // Appropriate values must be used for fee-per-gas. 
  maxFeePerGas: 1n,
  maxPriorityFeePerGas: 1n,
  accountMetadata,
});
On this page