1 files changed, 124 insertions, 0 deletions
diff --git a/packages/subproviders/src/subproviders/metamask_subprovider.ts b/packages/subproviders/src/subproviders/metamask_subprovider.ts
new file mode 100644
index 000000000..724edd574
--- /dev/null
+++ b/packages/subproviders/src/subproviders/metamask_subprovider.ts
@@ -0,0 +1,124 @@
+import { marshaller, Web3Wrapper } from '@0xproject/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 SignerSubprovider
+     * @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 has namespaced signTypedData to v3 for an indeterminate period of time.
+                    // 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 });
+            },
+        );
+    }
+}