MetaMask/zero-client

https://github.com/MetaMask/zero-client

MetaMask ZeroClient and backing iframe service

architecture

here is a comparison of the extension-based and iframe-based architecture

metamask extension:

dapp inpage.js <-> forwarder contentscript.js <-> extension background.js
ui popup.js <-> extension background.js

就是当用户通过浏览器通过web3去调用json rpc时，即通过dapp inpage.js，再传给metamask contentscript，再传给metamask background,background将会将要进行的操作传给UI，使其能够在与rpc进行交互之前再一次得到用户的确认，用户确认后就会返回background去与rpc进行交互，然后再将得到的数据通过metamask contentscript-dapp inpage.js传给浏览器

current metamask iframe:

dapp inpage.js <-> iframe background.js
ui app.metamask.io <-> iframe background.js

ideal metamask iframe:

dapp inpage.js <-> iframe forwarder <-> sharedworker background.js
ui app.metamask.io <-> iframe forwarder <-> sharedworker background.js

ideal unified metamask extension+iframe:

dapp inpage.js <-> iframe forwarder <-> sharedworker background.js
ui popup.js <-> iframe forwarder <-> sharedworker background.js

example

npm start

运行：

首先：

userdeMacBook-Pro:zero-client user$ npm install

然后运行npm start:

userdeMacBook-Pro:zero-client user$ npm start

> metamask-zeroclient@2.0. start /Users/user/zero-client
> ./example.sh

./example.sh: line : beefy: command not found
./example.sh: line : beefy: command not found
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! metamask-zeroclient@2.0. start: `./example.sh`
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the metamask-zeroclient@2.0. start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/user/.npm/_logs/--12T09_26_56_269Z-debug.log

出错，没有安装模块beefy:

什么是beefy及其使用

userdeMacBook-Pro:zero-client user$ npm install beefy --save

再运行又出错：

userdeMacBook-Pro:zero-client user$ npm start

> metamask-zeroclient@2.0. start /Users/user/zero-client
> ./example.sh

beefy (v2.1.8) is listening on http://127.0.0.1:9001
beefy (v2.1.8) is listening on http://127.0.0.1:9002
   58ms       261B  /
   70ms     .95KB  /bundle.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/.index.js -d
Error: Cannot find module 'metamask-crx/app/scripts/lib/inpage-provider.js' from '/Users/user/zero-client/lib'
    at /Users/user/zero-client/node_modules/browser-resolve/node_modules/resolve/lib/async.js::
    at process (/Users/user/zero-client/node_modules/browser-resolve/node_modules/resolve/lib/async.js::)
    at ondir (/Users/user/zero-client/node_modules/browser-resolve/node_modules/resolve/lib/async.js::)
    at load (/Users/user/zero-client/node_modules/browser-resolve/node_modules/resolve/lib/async.js::)
    at onex (/Users/user/zero-client/node_modules/browser-resolve/node_modules/resolve/lib/async.js::)
    at /Users/user/zero-client/node_modules/browser-resolve/node_modules/resolve/lib/async.js::
    at FSReqCallback.oncomplete (fs.js::)

发现是在lib/setup-provider.js中调用了metamask-crx模块(metamask chrome extension)，但node_modules中没有

从该网址下载https://github.com/ATNIO/metamask-crx：

const MetamaskInpageProvider = require('metamask-crx/app/scripts/lib/inpage-provider.js')

再运行，还是报错:

Error: Cannot find module 'brfs' from '/Users/user/zero-client/node_modules/metamask-crx'
    at /Users/user/zero-client/node_modules/resolve/lib/async.js::
    at processDirs (/Users/user/zero-client/node_modules/resolve/lib/async.js::)
    at ondir (/Users/user/zero-client/node_modules/resolve/lib/async.js::)
    at load (/Users/user/zero-client/node_modules/resolve/lib/async.js::)
    at onex (/Users/user/zero-client/node_modules/resolve/lib/async.js::)
    at /Users/user/zero-client/node_modules/resolve/lib/async.js::
    at FSReqCallback.oncomplete (fs.js::)

是因为下载下来的metamask-crx模块忘记运行npm install

然后再运行就成功了：

userdeMacBook-Pro:zero-client user$ npm start

> metamask-zeroclient@2.0. start /Users/user/zero-client
> ./example.sh

beefy (v2.1.8) is listening on http://127.0.0.1:9001
beefy (v2.1.8) is listening on http://127.0.0.1:9002
   50ms       261B  /
   63ms     .95KB  /bundle.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/.index.js -d
 2422ms     .12MB  /zero.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/index.js -d
   32ms       427B  /
    1ms        12B  /background.js
 1497ms     .33MB  /bundle.js ➞ ./node_modules/browserify ./frame.js -d
   25ms       261B  /
  116ms     .95KB  /bundle.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/.index.js -d
 1720ms     .12MB  /zero.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/index.js -d
    1ms       189B  /favicon.ico (generated)
   13ms       261B  /
   12ms     .95KB  /bundle.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/.index.js -d
 1377ms     .12MB  /zero.js ➞ /Users/user/zero-client/node_modules/browserify /Users/user/zero-client/index.js -d
   16ms       427B  /

在没有安装metamask插件的浏览器上的结果是：

在安装了metamask插件的浏览器上的结果是：

看到这个运行的结果后，我们可以看看其的代码：

他的代码与之前的mascara的差不多，如果想要看更详细的解释，可看mascara-2(MetaMask/mascara本地实现)-连接线上钱包

index.js

const Web3 = require('web3')
const setupProvider = require('./lib/setup-provider.js')

//
// setup web3
//

var provider = setupProvider()//1 设置provider
var web3 = new Web3(provider)
web3.currentProvider = provider
web3.setProvider = function(){
  console.log('MetaMask - overrode web3.setProvider')
}

//
// export web3
//
console.log(web3.currentProvider)
// console.log(web3.version.network)
// console.log(web3.eth.blockNumber)
global.web3 = web3

zero-client/lib/setup-provider.js

const setupIframe = require('./setup-iframe.js')
const MetamaskInpageProvider = require('metamask-crx/app/scripts/lib/inpage-provider.js')

module.exports = getProvider

function getProvider(){//1

  if (global.web3) {//2如果有安装插件，那么就使用插件的web3
    console.log('MetaMask ZeroClient - using environmental web3 provider')
    return global.web3.currentProvider
  }
  //3如果没有就自己设置
  console.log('MetaMask ZeroClient - injecting zero-client iframe!')
  var iframeStream = setupIframe({ //4设置iframe
    zeroClientProvider: 'http://localhost:9001', //4服务器端为9001
    sandboxAttributes: ['allow-scripts', 'allow-popups', 'allow-same-origin'],
  })

  var inpageProvider = new MetamaskInpageProvider(iframeStream) //6根据iframe流去设置MetamaskInpageProvider
  return inpageProvider

}

zero-client/lib/setup-iframe.js

const Iframe = require('iframe')
const IframeStream = require('iframe-stream').IframeStream

module.exports = setupIframe

function setupIframe(opts) {//4
  opts = opts || {}
  var frame = Iframe({
    src: opts.zeroClientProvider || 'https://zero.metamask.io/', //5就是如果没有设置服务器，那么就连接zero.metamask.io（docker设置，下面有讲）
    container: document.head,
    sandboxAttributes: opts.sandboxAttributes || ['allow-scripts', 'allow-popups'],
  })
  var iframe = frame.iframe
  var iframeStream = new IframeStream(iframe)//5 然后创建iframe流

  return iframeStream
}

metamask-crx/app/scripts/lib/inpage-provider.js

const pipe = require('pump')
const StreamProvider = require('web3-stream-provider')
const LocalStorageStore = require('obs-store')
const ObjectMultiplex = require('./obj-multiplex')
const createRandomId = require('./random-id')

module.exports = MetamaskInpageProvider

function MetamaskInpageProvider (connectionStream) {//7
  const self = this

  // setup connectionStream multiplexing
  var multiStream = self.multiStream = ObjectMultiplex()//8生成多路复用流
  pipe(//8将多路复用流与iframe流连接
    connectionStream,
    multiStream,
    connectionStream,
    (err) => logStreamDisconnectWarning('MetaMask', err)
  )

  // subscribe to metamask public config (one-way)
  self.publicConfigStore = new LocalStorageStore({ storageKey: 'MetaMask-Config' })//8设置本地存储
  pipe(//8在多路复用流中添加publicConfig流用以接收本地存储信息
    multiStream.createStream('publicConfig'),
    self.publicConfigStore,
    (err) => logStreamDisconnectWarning('MetaMask PublicConfigStore', err)
  )

  // connect to async provider
  const asyncProvider = self.asyncProvider = new StreamProvider()//8设置rpc provider流
  pipe(
    asyncProvider,
    multiStream.createStream('provider'),
    asyncProvider,
    (err) => logStreamDisconnectWarning('MetaMask RpcProvider', err)
  )

  self.idMap = {}
  // handle sendAsync requests via asyncProvider
  self.sendAsync = function (payload, cb) {
    // rewrite request ids
    var request = eachJsonMessage(payload, (message) => {//9 10 transformFn即这里的回调参数，payload为message
      var newId = createRandomId()//11这里是将json rpc中的id随机生成一个更复杂的id值去指明该笔request
      self.idMap[newId] = message.id //11保留旧的id，因为之后返回时返回的还是旧ID，新id只在过程中使用
      message.id = newId
      return message
    })
    // forward to asyncProvider
    asyncProvider.sendAsync(request, function (err, res) {
      if (err) return cb(err)
      // transform messages to original ids
      eachJsonMessage(res, (message) => {
        var oldId = self.idMap[message.id]
        delete self.idMap[message.id]
        message.id = oldId
        return message
      })
      cb(null, res)
    })
  }
}

MetamaskInpageProvider.prototype.send = function (payload) {
  const self = this

  let selectedAddress
  let result = null
  switch (payload.method) {

    case 'eth_accounts':
      // read from localStorage
      selectedAddress = self.publicConfigStore.getState().selectedAddress
      result = selectedAddress ? [selectedAddress] : []
      break

    case 'eth_coinbase':
      // read from localStorage
      selectedAddress = self.publicConfigStore.getState().selectedAddress
      result = selectedAddress
      break

    case 'eth_uninstallFilter':
      self.sendAsync(payload, noop)
      result = true
      break

    case 'net_version':
      let networkVersion = self.publicConfigStore.getState().networkVersion
      result = networkVersion
      break

    // throw not-supported Error
    default:
      var link = 'https://github.com/MetaMask/faq/blob/master/DEVELOPERS.md#dizzy-all-async---think-of-metamask-as-a-light-client'
      var message = `The MetaMask Web3 object does not support synchronous methods like ${payload.method} without a callback parameter. See ${link} for details.`
      throw new Error(message)

  }

  // return the result
  return {
    id: payload.id,
    jsonrpc: payload.jsonrpc,
    result: result,
  }
}

MetamaskInpageProvider.prototype.sendAsync = function () {
  throw new Error('MetamaskInpageProvider - sendAsync not overwritten')
}

MetamaskInpageProvider.prototype.isConnected = function () {
  return true
}

MetamaskInpageProvider.prototype.isMetaMask = true

// util

function eachJsonMessage (payload, transformFn) {//9
  if (Array.isArray(payload)) {//9如果是数组，说明一次要执行多个request
    return payload.map(transformFn)//9所以将数组中的request一个个传入transformFn，最后传出结果的数组
  } else {
    return transformFn(payload)//9如果不是，则说明是一个request，直接做transformFn的参数即可
  }
}

function logStreamDisconnectWarning(remoteLabel, err){
  let warningMsg = `MetamaskInpageProvider - lost connection to ${remoteLabel}`
  if (err) warningMsg += '\n' + err.stack
  console.warn(warningMsg)
}

function noop () {}

从上面的代码中我们可以看见，如果没有设置provider的话（zeroClientProvider: 'http://localhost:9001'），那么就会默认为https://zero.metamask.io/

这是通过docker进行设置的，如下：

Dockerfile

FROM node:0.12
MAINTAINER kumavis

# setup app dir
RUN mkdir -p /www/
WORKDIR /www/

# install dependencies
COPY ./package.json /www/package.json
RUN npm install

# copy over app dir
COPY ./ /www/

# run tests
RUN npm test

# start server
CMD npm start

# expose server
EXPOSE 

从这里我们可以看出基本上就是本文档的复制粘贴，部署了一个服务器，并提供了9000作为端口

docker-compose.yml

zeroClient:
  image: kumavis/zeroclient
  restart: always
  environment:
    VIRTUAL_HOST: "zero.metamask.io"
    VIRTUAL_PORT: ""
    PORT: ""
  ports:
    - ""

因为该项目的作者已经将该镜像上传，所以我们可以根据 docker-compose.yml的设置直接拉取镜像进行使用：

userdeMBP:zero-client user$ docker-compose up
Pulling zeroClient (kumavis/zeroclient:)...
latest: Pulling from kumavis/zeroclient
d4bce7fd68df: Pull complete
a3ed95caeb02: Pull complete
: Pull complete
5dcab2c7e430: Pull complete
dc54ada22a60: Pull complete
f4dbf915606d: Pull complete
2e6a016344c7: Pull complete
310ce789aae0: Pull complete
d9f04797303f: Pull complete
e69d1d8ba6cd: Pull complete
508a0e5f7217: Pull complete
Digest: sha256:6a7936b08541ced92fc35f63033046942df09e6a48a56f199de315eac002be51
Status: Downloaded newer image for kumavis/zeroclient:latest
Creating zero-client_zeroClient_1 ... done
Attaching to zero-client_zeroClient_1
zeroClient_1  |
zeroClient_1  | > metamask-zeroclient@1.0. start /www
zeroClient_1  | > node server.js
zeroClient_1  |
zeroClient_1  | MetaMask ZeroClient iframe server listening on 

然后这时候将zero-client/lib/setup-provider.js中的http://localhost:9001去掉，让其连接https://zero.metamask.io/：

得到结果：

然后在shared-worker文件夹中我们能够看到有：

zero-client/shared-worker/client.js

var worker = new SharedWorker("worker.js");

var id = Number.MAX_SAFE_INTEGER*Math.random()//3 随机生成id值

worker.port.addEventListener("message", function(e) {
  console.log(e)
  console.log(id)
  console.log("message")
  console.log(e.data);
}, false);

worker.port.start();//1 激活端口

// post a message to the shared web worker
worker.port.postMessage(id)//3 发送id,触发server.js的"message"事件

扩展，参考https://www.jb51.net/html5/551063.html：

SharedWorker类（html5）

　　SharedWorker的实质在于share，不同的线程可以共享一个线程，他们的数据也是共享的。

本例子是通过addEventListener()方法监听message事件，需要worker.port.start()方法激活端口。

也有下面这样的写法：

worker.port.onmessage = function(e) {
  console.log(e)
  console.log(id)
  console.log("message")
  console.log(e.data);
}

使用事件句柄的方式将听message事件，不需要调用worker.port.start()

不同于worker，当有人和他通信时触发connect事件（如下），然后他的message事件是绑定在messagePort对象上的

zero-client/shared-worker/server.js

var connections =  // count active connections

self.addEventListener("connect", function (e) {//2 进行连接var port = e.ports[]
  connections++

  port.addEventListener("message", function (e) {//4 收到消息id = e.data
    port.postMessage("Hello " + e.data + " (port #" + connections + ")")//5 post回消息，然后触发client.js的"message"事件
  }, false)

  port.start()//2 打开端口

}, false)

run example

beefy client.js:index.js server.js:worker.js --live --open 

然后我们为了将这个例子运行起来，需要对package.json进行更改，添加"example"：

  "scripts": {
    "test": "echo \"Error: no tests yet\" && exit 0",
    "start": "./example.sh",
    "example": "beefy shared-worker/client.js:index.js shared-worker/server.js:worker.js 9003 --live --open "
  },

这里没有设置端口，会随机使用一个端口，但是你也可以自己设置，这里我们设置为9003，然后运行：

userdeMacBook-Pro:zero-client user$ npm run example

> metamask-zeroclient@2.0. example /Users/user/zero-client
> beefy shared-worker/client.js:index.js shared-worker/server.js:worker.js  --live --open 

beefy (v2.1.8) is listening on http://127.0.0.1:9003
   70ms       552B  /
  793ms     .36KB  /index.js ➞ ./node_modules/browserify ./shared-worker/client.js -d
   30ms       552B  /
   17ms     .36KB  /index.js ➞ ./node_modules/browserify ./shared-worker/client.js -d
   36ms       552B  /
   10ms     .36KB  /index.js ➞ ./node_modules/browserify ./shared-worker/client.js -d
   19ms       552B  /
    8ms     .36KB  /index.js ➞ ./node_modules/browserify ./shared-worker/client.js -d

并且将index.html上的bundle.js改为index.js:

<!doctype html>

<html lang="en">
<head>
  <meta charset="utf-8">

  <title>MetaMask ZeroClient Iframe</title>
  <span style="white-space:pre"></span>
  <link href="http://www.lituanmin.com/favicon.ico" rel="icon" type="image/x-icon" />
  <meta name="description" content="MetaMask ZeroClient">
  <meta name="author" content="MetaMask">

  <!--[if lt IE ]>
  <script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
  <![endif]-->
</head>

<body>
  Hello! I am the MetaMask iframe.
  <script src="/index.js"></script>
</body>
</html>

返回：

刷新一次可以看见port 4变成了port 5，是第五次访问