Tutorial

Example of a session key with an action policy.

1 - Create a Session Key

import { generatePrivateKey, privateKeyToAccount } from "viem/accounts";
import {
    type ComethSmartAccountClient,
    type SafeSigner,
    erc7579Actions,
    smartSessionActions,
} from "@cometh/connect-sdk-4337";

export const COUNTER_CONTRACT_ADDRESS =
    "0x4FbF9EE4B2AF774D4617eAb027ac2901a41a7b5F";


const safe7559AccountClient = smartAccountClient.extend(smartSessionActions())
            .extend(erc7579Actions());

const privateKey = generatePrivateKey();
const sessionOwner = privateKeyToAccount(privateKey);

const createSessionsResponse = await safe7559AccountClient.grantPermission({
    sessionRequestedInfo: [
        {
            sessionPublicKey: sessionOwner.address,
            actionPoliciesInfo: [
                {
                    contractAddress: COUNTER_CONTRACT_ADDRESS,
                    functionSelector: toFunctionSelector(
                        "function count()"
                    ) as Hex,
                },
            ],
        },
    ],
});

await safe7559AccountClient.waitForUserOperationReceipt({
    hash: createSessionsResponse.userOpHash,
});

2 - Store the Session Key

In our example, we will store the session key details in local storage. You are free to store it wherever you want.

import { SmartSessionMode } from "@cometh/connect-sdk-4337";

const sessionData = {
    granter: smartAccountClient?.account?.address as Address,
    privateKey: privateKey,
    sessionPublicKey: sessionOwner.address,
    description: `Session to increment a counter`,
    moduleData: {
        permissionIds: createSessionsResponse.permissionIds,
        action: createSessionsResponse.action,
        mode: SmartSessionMode.USE,
        sessions: createSessionsResponse.sessions,
    },
};

// This is for example purposes.
const sessionParams = stringify(sessionData);

localStorage.setItem(
    `session-key-${smartAccountClient?.account?.address}`,
    sessionParams
);

3 - Use the Session Key

import {
    createComethPaymasterClient,
    createSafeSmartAccount,
    createSmartAccountClient,
    smartSessionActions,
    toSmartSessionsSigner
} from "@cometh/connect-sdk-4337";
import { generatePrivateKey, privateKeyToAccount } from "viem/accounts";

const apiKey = process.env.COMETH_API_KEY;
const bundlerUrl = process.env.4337_BUNDLER_URL;
const paymasterUrl = process.env.4337_PAYMASTER_URL
const publicClient = createPublicClient({
    chain,
    transport: http(),
});


const stringifiedSessionData = localStorage.getItem(
    `session-key-${WALLETADDRESS}`
);
const sessionData = parse(stringifiedSessionData);

const sessionKeySigner = await toSmartSessionsSigner(safe7559Account, 
{
    moduleData: sessionData.moduleData,
    signer: privateKeyToAccount(sessionData.privateKey),
})

const sessionKeyAccount = await createSafeSmartAccount({
    apiKey,
    chain,
    smartAccountAddress: smartAccountClient?.account?.address,
    smartSessionSigner: sessionKeySigner,
});

const paymasterClient = await createComethPaymasterClient({
    transport: http(paymasterUrl),
    chain,
});

const sessionKeyClient = createSmartAccountClient({
    account: sessionKeyAccount,
    chain,
    bundlerTransport: http(bundlerUrl),
    paymaster: paymasterClient,
    userOperation: {
        estimateFeesPerGas: async () => {
            return await paymasterClient.getUserOperationGasPrice();
        },
    },
}).extend(smartSessionActions());

const callData = encodeFunctionData({
    abi: countContractAbi,
    functionName: "count",
});

const hash = await sessionKeyClient.usePermission({
    actions: [
        {
            target: COUNTER_CONTRACT_ADDRESS,
            callData: callData,
            value: BigInt(0),
        },
    ],
});