metatx-server
v1.0.12
Published
Meta Tx for the backend server
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metatx-server
This package is for serverside processing of ethereum meta transactions. It is the server side component of metatx-client, but it can also be used on it's own.
Exposes a class MetaTxHandler that should be instantiated like this:
const metaTxHandler = new MetaTxHandler(
relayerPrivKey, // required arg. The private key that will relay transactions
provider, // required arg. Your web3 provider
txRelayAddress, // required arg. The address of your relayer contract
txRelayABI, // required arg. The abi of your relayer contract
logger // optional arg. Your logger, if you use one. Should have levels info and error
)
Methods:
getRelayerAddress
=> returns the given relayer address
getRelayNonce (address)
=> returns the nonce held in the relayer contract of the given address. A relayer nonce is required to prevent replay attacks.
initSimpleSigner
=> generates an eth-signer signer from the relayer private key given in the contructor
getSenderKeyPair (senderPrivKey)
=> generates a keypair from any given private key
initTxRelaySigner (senderPrivKey, _whitelist)
=> generates an eth-signer signer for the given sender private key. senderPrivKey
is required, whitelist
is optional.
estimateGas (tx, txSender)
=> estimates gas cost of a transaction, formatted in rlp.
isMetaSignatureValid (metaSignedTx, metaNonce)
=> verified that a meta signature is valid. metaSignedTx
is a signed meta transaction and metaNonce
is the nonce of the sender as of the relayer contract.
signMetaTx (txParams, senderPrivKey, relayNonce, whitelist)
=> prepares a signed meta transaction. txParams
is an object that can be constructed like this:
const tx = {
from: address,
to: contractAddress,
value: 0,
data: Contract.methods.methodName(methodArgs).encodeABI()
};
senderPrivKey
is the private key of the from address is txParams
. relayNonce
is optional, and will default to the relayer address set in the constructor. whitelist
is also optional.
signRelayerTx (txHex)
=> Signs a meta transaction for forwarding to the relayer contract. txHex
should be the signed meta tx in rlp encoding. Also estimates the gas price needed to execute the transaction.
sendRawTransaction (signedRawTx)
=> signes and sends a raw transaction to provider
handle (req)
=> Fully handles a request to the server to process a meta transaction. Can be used like this:
const relay = async (req, res) => {
try {
const result = await MetaTxHandler.handle(req)
return res.status(200).json({ result })
} catch (err) {
return res.status(error.code).json({ error: error.message })
}