Greenfield Demo: Contract as Bucket Owner¶

BNB Greenfield provides the ability for a contract to manage buckets through greenfield cross-chain transactions, and we’ll use a demo to briefly demonstrate the process.

Source Code¶

Greenfield Demo App Contract: GreenfieldDemo
Script to Interact with Demo: Demo Script

Greenfield Demo Contract¶

The Demo includes the following parts:

greenfield contracts constant:¶

    // BSC testnet
    address public constant TOKEN_HUB = 0xED8e5C546F84442219A5a987EE1D820698528E04;
    address public constant CROSS_CHAIN = 0xa5B2c9194131A4E0BFaCbF9E5D6722c873159cb7;
    address public constant BUCKET_HUB = 0x5BB17A87D03620b313C39C24029C94cB5714814A;
    address public constant PERMISSION_HUB = 0x25E1eeDb5CaBf288210B132321FBB2d90b4174ad;
    address public constant SP_ADDRESS_TESTNET = 0x5FFf5A6c94b182fB965B40C7B9F30199b969eD2f;
    address public constant GREENFIELD_EXECUTOR = 0x3E3180883308e8B4946C9a485F8d91F8b15dC48e;

The addresses of Greenfield contracts deployed on the BSC testnet are available and configured here. You can find contracts deployed on other networks contract entrypoint

create bucket and set bucket flow rate limit¶

    function createBucket(string memory bucketName, uint256 transferOutAmount, bytes memory _executorData) external payable;

Provides the bucket name, initial BNB amount transferred to the demo contract on Greenfield and the executor data to set bucket flow rate limit.This API will create a new bucket owned by the smart contract and set the payment for it.

create policy to allow eoa account to upload files to the bucket¶

    function createPolicy(bytes memory createPolicyData) external payable;

Construct the createPolicyData parameters to grant permission to the dedicated principle for the created bucket owned by the smart contract.

Interact Script¶

Installation¶

git clone https://github.com/bnb-chain/greenfield-contracts.git
cd greenfield-contracts && git checkout develop
npm install
npx hardhat compile

cp .env.example .env
# set `DeployerPrivateKey` on .env
# make sure the tBNB balance of the account >= 0.5 BNB on BSC Testnet
npx hardhat run scripts/11-demo-contract-approve-eoa-upload.ts  --network bsc-testnet

Workflow¶

The interact script includes 4 steps as follows:

deploy demo contract¶

    const demo = (await deployContract(operator, 'GreenfieldDemo')) as GreenfieldDemo;

create bucket whose owner is the demo contract¶

set bucket flow rate limit and cross-chain transfer 0.1 BNB to demo contract

const bucketName = 'test-' + demo.address.substring(2, 6).toLowerCase();
// - transferOutAmt: 0.1 BNB to demo contract on Greenfield
// - set bucket flow rate limit to this bucket
// - create bucket: 'test-approve-eoa-upload', its owner is demo contract
const dataSetBucketFlowRateLimit = ExecutorMsg.getSetBucketFlowRateLimitParams({
    bucketName,
    bucketOwner: demo.address,
    operator: demo.address,
    paymentAddress: demo.address,
    flowRateLimit: '1000000000000000000',
});
const executorData = dataSetBucketFlowRateLimit[1];
const transferOutAmt = ethers.utils.parseEther('0.1');
const value = transferOutAmt.add(relayFee.mul(3).add(ackRelayFee.mul(2)));

log('- transfer out to demo contract on greenfield', toHuman(transferOutAmt));
log('- create bucket', bucketName);
log('send crosschain tx!');
const receipt = await waitTx(
    demo.createBucket(bucketName, transferOutAmt, executorData, { value })
);
log(`https://testnet.bscscan.com/tx/${receipt.transactionHash}`);

get bucket id by name after bucket created¶

const bucketInfo = await client.bucket.getBucketMeta({ bucketName });
const bucketId = bucketInfo.body!.GfSpGetBucketMetaResponse.Bucket.BucketInfo.Id;
log('bucket created, bucket id', bucketId);
const hexBucketId = `0x000000000000000000000000000000000000000000000000000000000000${BigInt(
    bucketId
).toString(16)}`;
log(`https://testnet.greenfieldscan.com/bucket/${hexBucketId}`);

create policy to allow EOA account upload files to the bucket through cross-chain transaction¶

const uploaderEoaAccount = operator.address; // TODO set your eoa account to upload files
log('try to set uploader(eoa account) is', uploaderEoaAccount);

const policyDataToAllowUserOperateBucket = Policy.encode({
    id: '0',
    resourceId: bucketId, // bucket id
    resourceType: ResourceType.RESOURCE_TYPE_BUCKET,
    statements: [
        {
            effect: Effect.EFFECT_ALLOW,
            actions: [ActionType.ACTION_CREATE_OBJECT], // allow upload file to the bucket
            resources: [],
        },
    ],
    principal: {
        type: PrincipalType.PRINCIPAL_TYPE_GNFD_ACCOUNT,
        value: uploaderEoaAccount,
    },
}).finish();

await waitTx(
    demo.createPolicy(policyDataToAllowUserOperateBucket, { value: relayFee.add(ackRelayFee) })
);

Now the deployer account can upload files to the bucket on Greenfield.