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import { marshaller, Web3Wrapper } from '@0x/web3-wrapper';
import { JSONRPCRequestPayload, Provider } from 'ethereum-types';
import * as ethUtil from 'ethereumjs-util';
import { Callback, ErrorCallback } from '../types';
import { Subprovider } from './subprovider';
/**
* This class implements the [web3-provider-engine](https://github.com/MetaMask/provider-engine)
* subprovider interface and the provider sendAsync interface.
* It handles inconsistencies with Metamask implementations of various JSON RPC methods.
* It forwards JSON RPC requests involving the domain of a signer (getAccounts,
* sendTransaction, signMessage etc...) to the provider instance supplied at instantiation. All other requests
* are passed onwards for subsequent subproviders to handle.
*/
export class MetamaskSubprovider extends Subprovider {
private readonly _web3Wrapper: Web3Wrapper;
private readonly _provider: Provider;
/**
* Instantiates a new MetamaskSubprovider
* @param provider Web3 provider that should handle all user account related requests
*/
constructor(provider: Provider) {
super();
this._web3Wrapper = new Web3Wrapper(provider);
this._provider = provider;
}
/**
* This method conforms to the web3-provider-engine interface.
* It is called internally by the ProviderEngine when it is this subproviders
* turn to handle a JSON RPC request.
* @param payload JSON RPC payload
* @param next Callback to call if this subprovider decides not to handle the request
* @param end Callback to call if subprovider handled the request and wants to pass back the request.
*/
// tslint:disable-next-line:prefer-function-over-method async-suffix
public async handleRequest(payload: JSONRPCRequestPayload, next: Callback, end: ErrorCallback): Promise<void> {
let message;
let address;
switch (payload.method) {
case 'web3_clientVersion':
try {
const nodeVersion = await this._web3Wrapper.getNodeVersionAsync();
end(null, nodeVersion);
} catch (err) {
end(err);
}
return;
case 'eth_accounts':
try {
const accounts = await this._web3Wrapper.getAvailableAddressesAsync();
end(null, accounts);
} catch (err) {
end(err);
}
return;
case 'eth_sendTransaction':
const [txParams] = payload.params;
try {
const txData = marshaller.unmarshalTxData(txParams);
const txHash = await this._web3Wrapper.sendTransactionAsync(txData);
end(null, txHash);
} catch (err) {
end(err);
}
return;
case 'eth_sign':
[address, message] = payload.params;
try {
// Metamask incorrectly implements eth_sign and does not prefix the message as per the spec
// Source: https://github.com/MetaMask/metamask-extension/commit/a9d36860bec424dcee8db043d3e7da6a5ff5672e
const msgBuff = ethUtil.toBuffer(message);
const prefixedMsgBuff = ethUtil.hashPersonalMessage(msgBuff);
const prefixedMsgHex = ethUtil.bufferToHex(prefixedMsgBuff);
const signature = await this._web3Wrapper.signMessageAsync(address, prefixedMsgHex);
signature ? end(null, signature) : end(new Error('Error performing eth_sign'), null);
} catch (err) {
end(err);
}
return;
case 'eth_signTypedData':
case 'eth_signTypedData_v3':
[address, message] = payload.params;
try {
// Metamask supports multiple versions and has namespaced signTypedData to v3 for an indeterminate period of time.
// eth_signTypedData is mapped to an older implementation before the spec was finalized.
// Source: https://github.com/MetaMask/metamask-extension/blob/c49d854b55b3efd34c7fd0414b76f7feaa2eec7c/app/scripts/metamask-controller.js#L1262
// and expects message to be serialised as JSON
const messageJSON = JSON.stringify(message);
const signature = await this._web3Wrapper.sendRawPayloadAsync<string>({
method: 'eth_signTypedData_v3',
params: [address, messageJSON],
});
signature ? end(null, signature) : end(new Error('Error performing eth_signTypedData'), null);
} catch (err) {
end(err);
}
return;
default:
next();
return;
}
}
/**
* This method conforms to the provider sendAsync interface.
* Allowing the MetamaskSubprovider to be used as a generic provider (outside of Web3ProviderEngine) with the
* addition of wrapping the inconsistent Metamask behaviour
* @param payload JSON RPC payload
* @return The contents nested under the result key of the response body
*/
public sendAsync(payload: JSONRPCRequestPayload, callback: ErrorCallback): void {
void this.handleRequest(
payload,
// handleRequest has decided to not handle this, so fall through to the provider
() => {
const sendAsync = this._provider.sendAsync.bind(this._provider);
sendAsync(payload, callback);
},
// handleRequest has called end and will handle this
(err, data) => {
err ? callback(err) : callback(null, { ...payload, result: data });
},
);
}
}
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