Bridge v2

Bridge v2 is the second version of bridge which is used for validators and relayers to listen to events triggered from Ronin or other chains connected to Ronin (eg: Ethereum). There are two mains features:

• Voting and relaying bridge operators (it currently changes in every period - 1 day).
• Listen to deposit and withdraw request on Ronin/Ethereum and relay it to the others.

How to run

Requirements

• Ronin RPC URL is used to listen/trigger events from Ronin chain
• Ethereum RPC URL (Alchemy, Infura, etc.) is used to listen/trigger events from Ethereum
• Postgres DB to store events and tasks

Install and run

Using docker

There is a docker-compose.yaml file in docker directory. Modify .env file and run bridge with the following command

docker-compose -f docker/docker-compose.yaml --env-file .env up -d

Manually

Install PostgreSQL database, create bridge database

build and install bridge

make bridge

then run Bridge with

bridge --config <path-to-config>

Configuration

The config file can be found in the config directory. There are 2 main components in the configuration: listeners and database

listeners (object)

List all chains that Bridge is listening to. Each name reflects a specific function defined here.

For example Ronin reflects with function InitRonin

Therefore, do not change the name, otherwise, the program cannot run properly.

1. chainId:

• type: hex string

Chain's identity (ronin: 0x7e4, ethereum: 0x1)

2. rpcUrl:

• type: string

RPC URL of chain which is used to query new events or submit transactions to.

3. blockTime:

• type: number
• unit: seconds

The time of a new block is generated which is used periodically to listen to new events from the new block,

4. safeBlockRange:

• type: number
• unit: blocks

Safe block range which guarantees that reorg cannot happen.

5. maxTasksQuery:

• type: number

Maximum number of pending/processing tasks queried from the database

6. transactionCheckPeriod:

• type: number
• unit: seconds

Period of checking whether a transaction is mined or not by querying its transaction's receipt. If a receipt is found, it will try 3 more times to ensure the transaction is not replaced because of reorg.

7. secret:

• type: object

Stores private key of validator and relayer. These fields can be empty and passed via environment variables through 2 variables: RONIN_VALIDATOR_KEY, RONIN_RELAYER_KEY and Ethereum are: ETHEREUM_VALIDATOR_KEY, ETHEREUM_RELAYER_KEY

syntax: <key>

example: xxxx4563e6591c1eba4b932a3513006cb5bcd1a6f69c32295dxxxx

If KMS is used, set these environments

• RONIN_VALIDATOR_KMS_KEY_TOKEN_PATH
• RONIN_VALIDATOR_KMS_SSL_CERT_PATH
• RONIN_VALIDATOR_KMS_SERVER_ADDR
• RONIN_VALIDATOR_KMS_SOURCE_ADDR
• RONIN_VALIDATOR_KMS_SIGN_TIMEOUT

Replace RONIN with ETHEREUM, VALIDATOR with RELAYER when needed

This is the sample secret's config

{
  "secret": {
    "validator": {
      "kmsConfig": {
        "keyTokenPath": "./key",
        "sslCertPath": "./ssl.crt",
        "kmsServerAddr": "127.0.0.1:1234",
        "kmsSourceAddr": ":5000",
        "signTimeout": 3000
      }
    },
    "relayer": {
      "plainPrivateKey": "" // Raw private key
    }
  }
}

8. fromHeight:

• type: number
• unit: blocks

Initially, Bridge uses this property to load data from this block. After that, Bridge will store the latest processed block in processed_block table and use the value from this table to continue.

9. processWithinBlocks:

• type: number
• unit: blocks

This property guarantees that Bridge does not process too far. Specifically, when latestBlock - processWithinBlocks > fromHeight, bridge latestBlock - processWithinBlocks instead of fromHeight to process.

10. contracts

• type: record<string, address>

Stores a map (pair) of names and contact addresses, which can be used during processing tasks or jobs of a listener. For example, in Ronin listener, 2 contracts which are Ronin Gateway contract (at Gateway) and Ethereum Gateway contract (at EthGateway) are used:

{
  "Gateway": "0x03d1F13c7391F6B5A651143a31034cf728A93694",
  "EthGateway": "0x3b6371EB912bFd5C0E249A16000ffbC6B881555A"
}

11. subscriptions

• type: object

Includes all subscriptions bridge is observing in a listener. Each subscription contains the subscription name and subscription config.

• to: Indicates receiver/contract address that bridge uses as one of conditions to trigger a subscription
• type: There are 2 types, 0 is transaction event and 1 is log's event
• handler: Define contract and event that we want to listen
  • contract: Contract name. This must be defined on repo Bridge Contracts
  • name: The event name
• callbacks: List all callbacks function when data is decoded. This is a map (pair) where the key is listener's name and value is the function that is called in that listener. For example:

{
  "to": "0xA8D61A5427a778be28Bd9bb5990956b33385c738",
  "type": 1, // Listen log's event
  "handler": {
    "contract": "RoninGateway",
    "name": "MainchainWithdrew"
  },
  "callbacks": {
    "Ronin": "StoreMainchainWithdrawCallback"
  }
}

Bridge will trigger the function StoreMainchainWithdrawCallback in RoninListener

Example

For example, Bridge will listen to event Welcomed which is defined on contract Hello and submit the data to HelloEth contract via method SubmitFromRonin

{
  "MainchainWithdrewSubscription": {
    "to": "0xA8D61A5427a778be28Bd9bb5990956b33385c738",
    "type": 1,
    "handler": {
      "contract": "RoninGateway", // The contract name, it must be defined on [Bridge Contracts](https://github.com/axieinfinity/bridge-contracts/blob/master/main.go#L13-L20) first.
      "name": "Welcome" // The event is listening
    },
    "callbacks": {
      "Ronin": "WelcomeCallback" // Execute the callback on Ronin chain
    }
  },
}

On litenser/ronin.go add the following method

package listener

func (l *RoninListener) WelcomeCallback(fromChainId *big.Int, tx bridgeCore.Transaction, data []byte) error {
	// Unpack event data
	roninEvent := new(hello.WelcomeEvent)
	roninGatewayAbi, err := hello.GatewayMetaData.GetAbi()

	// Since the data argument was the log's marshalled in bytes, so it must be unmarshalled
	// before being use
	if err = l.utilsWrapper.UnpackLog(*roninGatewayAbi, roninEvent, "Welcome", data); err != nil {
		return err
	}

    chainId, err := l.GetChainID()
  
	// Create a new task
    t := &models.Task{
        ChainId:         hexutil.EncodeBig(chainId),
        FromChainId:     hexutil.EncodeBig(fromChainId),
        FromTransaction: tx.GetHash().Hex(),
        Type:            task.WELCOME_TASK, // defined in task/main.go
        Data:            common.Bytes2Hex(data),
        Retries:         0,
        Status:          task.STATUS_PENDING,
        LastError:       "",
        CreatedAt:       time.Now().Unix(),
    }
	
	// Get the store API to save the task to database
	return l.bridgeStore.GetTaskStore().Save(withdrawalTask)
}

Then create a method welcomeTask in task/task.go

package task

func (r *task) welcomeTask(task *models.Task) (doneTasks, processingTasks, failedTasks []*models.Task, tx *ethtypes.Transaction) {
	// create caller
	transactor, err := helloEth.NewHelloEth(common.HexToAddress(r.contracts[HELLO_ETH_CONTRACT]), r.ethClient)
	
    tx, err = r.util.SendContractTransaction(r.listener.GetValidatorSign(), r.chainId, func(opts *bind.TransactOpts) (*ethtypes.Transaction, error) {
      return transactor.SubmitFromRonin(opts)
    })
	doneTasks = append(doneTasks, task)
	return
}

Finally, add it to send method:

package task

func (r *task) send() {
	log.Info("[task] Sending transaction", "type", r.taskType)
	switch r.taskType {
	case VOTE_BRIDGE_OPERATORS_TASK:
		r.sendTransaction(r.voteBridgeOperatorsBySignature)
	case RELAY_BRIDGE_OPERATORS_TASK:
		r.sendTransaction(r.relayBridgeOperators)
	}
}

Subscriptions

MainchainWithdrewSubscription

graph TD
  tryBulkAcknowledgeMainchainWithdrew --> |Emit| MainchainWithdrew
  Bridge --> |Listen| MainchainWithdrew
  Bridge --> A{Got event?}
  A --> |No| Bridge
  A --> |Yes| B[Store Receipt To Database]

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WithdrawalRequestedSubscription

Request validators sign withdrawal transaction

graph TD
  bulkRequestWithdrawalFor --> |Emit| WithdrawalRequested
  Bridge --> |Listen| WithdrawalRequested
  Bridge --> A{Got Event?}
  A --> |No| Bridge
  A --> |Yes| signWithdrawalSignatures
  signWithdrawalSignatures --> BulkSubmitWithdrawalSignatures

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WithdrawalSignaturesRequestedSubscription

Request validators sign withdrawal transaction again

graph TD
  requestWithdrawalSignatures --> |Emit| WithdrawalSignaturesRequested
  Bridge --> |Listen| WithdrawalRequested
  Bridge --> A{Got Event?}
  A --> |No| Bridge
  A --> |Yes| signWithdrawalSignatures
  signWithdrawalSignatures --> BulkSubmitWithdrawalSignatures

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DepositRequestedSubscription

When a user deposit ETH on Ethereum to contract. Bridge will listen this event and send it to Ronin

graph TD
  requestDepositFor --> |Emit| DepositRequested
  Bridge --> |Listen| DepositRequested
  Bridge --> A{Got event?}
  A --> |No| Bridge
  A --> |Yes| sendDepositTransaction
  sendDepositTransaction --> B{Is Voted?}
  B --> |Yes| Done
  B --> |No| StoreProcessedReceipt
  StoreProcessedReceipt --> TryBulkDepositFor

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WithdrewSubscription

When a user withdraw ETH from contract. Bridge will listen this event and send it to Ronin

graph TD
  unlockWithdrawal --> |Emit| Withdrew
  submitWithdrawal --> |Emit| Withdrew
  Bridge --> |Listen| Withdrew
  Bridge --> A{Got event?}
  A --> |No| Bridge
  A --> |Yes| MainchainWithdrewVoted
  MainchainWithdrewVoted --> B{Is Voted?}
  B --> |Yes| Done
  B --> |No| TryBulkAcknowledgeMainchainWithdrew

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BridgeOperatorSetUpdatedSubscription

At the end of each period, validators call wrapUpEpoch of ValidatorSet contract to update list validator set. It emits an event BridgeOperatorSetUpdated(uint256 period, []address operators). All trusted nodes must listen this event, vote by signing typed data and submit it to RoninGovernanceAdmin contract.

graph TD
  Validator -->|Call| WrapUpEpoch
  WrapUpEpoch -->|Emit| BridgeOperatorSetUpdated
  Bridge --> |Listen| BridgeOperatorSetUpdated
  Bridge --> E{Got an event}
  E --> |Yes| BridgeOperatorsVoted
  E --> |No| Bridge
  BridgeOperatorsVoted --> A{Submitted}
  A --> |No| VoteBridgeOperatorsBySignatures
  A --> |Yes| Done

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BridgeOperatorsApprovedSubscription

After trusted nodes submitted vote's signature to RoninGovernanceAdmin. Relayer needs to call GetAllTrustedOrganizations to get all trusted nodes, sort it as ascending. Then call GetBridgeOperatorVotingSignatures to get a list signatures that submitted on Ronin. Finally, relayer submits these signatures to MainchainGovernanceAdmin through RelayBridgeOperators method.

graph TD
  VoteBridgeOperatorsBySignatures --> |Emit| BridgeOperatorsApproved
  Bridge --> |Listen| BridgeOperatorsApproved
  Bridge --> A{Got event}
  A --> |Yes| GetAllTrustedOrganizations
  A --> |No| Bridge
  GetAllTrustedOrganizations --> GetBridgeOperatorVotingSignatures
  GetBridgeOperatorVotingSignatures --> RelayBridgeOperators

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Database

Database configuration is defined within the key database. Basic properties include host, port, user, password and dbName.

{
  "database": {
    "host": "localhost", // Database host name
    "user": "postgres", // Database username
    "password": "example", // Database password
    "dbName": "bridge", // Database name
    "port": 5432 // Database port
  }
}

Contribution

Thank you for considering helping out with the source code! We welcome contributions from anyone on the internet, and are grateful for even the smallest of fixes!

If you'd like to contribute to Bridge, please fork, fix, commit and send a pull request for the maintainers to review and merge into the main code base. If you wish to submit more complex changes though, please check up with the core devs first issues on Github to ensure those changes are in line with the general philosophy of the project and/or get some early feedback which can make both your efforts much lighter as well as our review and merge procedures quick and simple.

Please make sure your contributions adhere to our coding guidelines:

• Code must adhere to the official Go formatting guidelines (i.e. uses gofmt).
• Code must be documented adhering to the official Go commentary guidelines.
• Pull requests need to be based on and opened against the master branch.
• Commit messages should be prefixed with the package(s) they modify.
  • E.g. "fix: make trace configs optional"

Please see the Developers' Guide for more details on configuring your environment, managing project dependencies, and testing procedures.

License

Bridge library and binaries (i.e. all code outside and inside of the cmd directory) is licensed under the Apache License 2.0, also included in our repository in the COPYING file.