I am getting an “Invalid Host header” message when connecting to webpack-dev-server remotely

Question

I am using as an environment, a Cloud9.io ubuntu VM Online IDE and I have reduced by troubleshooting this error to just running the app with Webpack dev server.

I launch it with:

webpack-dev-server -d --watch --history-api-fallback --host $IP --port $PORT

$IP is a variable that has the host address $PORT has the port number.

I am instructed to use these vars when deploying an app in Cloud 9, as they have the default IP and PORT info.

The server boots up and compiles the code, no problem, it is not showing me the index file though. Only a blank screen with "Invalid Host header" as text.

This is the Request:

GET / HTTP/1.1
Host: store-client-nestroia1.c9users.io
Connection: keep-alive
Pragma: no-cache
Cache-Control: no-cache
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 
(KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36
Accept: 
text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
DNT: 1
Accept-Encoding: gzip, deflate, sdch, br
Accept-Language: en-US,en;q=0.8

This is my package.json:

{
  "name": "workspace",
  "version": "0.0.0",
  "scripts": {
    "dev": "webpack -d --watch",
    "server": "webpack-dev-server -d --watch --history-api-fallback --host $IP --port $PORT",
    "build": "webpack --config webpack.config.js"
  },
  "author": "Artur Vieira",
  "license": "ISC",
  "dependencies": {
    "babel-core": "^6.18.2",
    "babel-loader": "^6.2.8",
    "babel-preset-es2015": "^6.18.0",
    "babel-preset-react": "^6.16.0",
    "babel-preset-stage-0": "^6.24.1",
    "file-loader": "^0.11.1",
    "node-fetch": "^1.6.3",
    "react": "^15.5.4",
    "react-bootstrap": "^0.30.9",
    "react-dom": "^15.5.4",
    "react-router": "^4.1.1",
    "react-router-dom": "^4.1.1",
    "url-loader": "^0.5.8",
    "webpack": "^2.4.1",
    "webpack-dev-server": "^2.4.4",
    "whatwg-fetch": "^2.0.3"
  }
}

This is the webpack.config.js:

const path = require('path');

module.exports = {

  entry: ['whatwg-fetch', "./app/_app.jsx"], // string | object | array
  // Here the application starts executing
  // and webpack starts bundling
  output: {
    // options related to how webpack emits results

    path: path.resolve(__dirname, "./public"), // string
    // the target directory for all output files
    // must be an absolute path (use the Node.js path module)

    filename: "bundle.js", // string
    // the filename template for entry chunks

    publicPath: "/public/", // string
    // the url to the output directory resolved relative to the HTML page
  },

  module: {
    // configuration regarding modules

    rules: [
      // rules for modules (configure loaders, parser options, etc.)
      {
        test: /\.jsx?$/,
        include: [
          path.resolve(__dirname, "./app")
        ],
        exclude: [
          path.resolve(__dirname, "./node_modules")
        ],
        loader: "babel-loader?presets[]=react,presets[]=es2015,presets[]=stage-0",
        // the loader which should be applied, it'll be resolved relative to the context
        // -loader suffix is no longer optional in webpack2 for clarity reasons
        // see webpack 1 upgrade guide
      },
      {
        test: /\.css$/,
        use: [ 'style-loader', 'css-loader' ]
      },
      {
        test: /\.(png|jpg|jpeg|gif|svg|eot|ttf|woff|woff2)$/,
        loader: 'url-loader',
        options: {
          limit: 10000
        }
      }
    ]
  },

  devServer: {
    compress: true
  }
}

Webpack dev server is returning this because of my host setup. In webpack-dev-server/lib/Server.js line 60. From https://github.com/webpack/webpack-dev-server

My question is how do I setup to correctly pass this check. Any help would be greatly appreciated.

Answer 1

The problem occurs because webpack-dev-server 2.4.4 adds a host check. You can disable it by adding this to your webpack config:

 devServer: {
    compress: true,
    disableHostCheck: true,   // That solved it

 }      

EDIT: Please note, this fix is insecure.

Please see the following answer for a secure solution: https://stackoverflow.com/a/43621275/5425585

Answer 2

I found out, that I need to set the public property of devServer, to my request's host value. Being that it will be displayed at that external address.

So I needed this in my webpack.config.js

devServer: {
  compress: true,
  public: 'store-client-nestroia1.c9users.io' // That solved it
}

Another solution is using it on the CLI:

webpack-dev-server --public $C9_HOSTNAME   <-- var for Cloud9 external IP

Answer 3

This is what worked for me:

Add allowedHosts under devServer in your webpack.config.js:

devServer: {
  compress: true,
  inline: true,
  port: '8080',
  allowedHosts: [
      '.amazonaws.com'
  ]
},

I did not need to use the --host or --public params.

Answer 4

Add this config to your webpack config file when using webpack-dev-server (you can still specify the host as 0.0.0.0).

devServer: {
    disableHostCheck: true,
    host: '0.0.0.0',
    port: 3000
}

Answer 5

The more secure option would be to add allowedHosts to your Webpack config like this:

module.exports = {
devServer: {
 allowedHosts: [
  'host.com',
  'subdomain.host.com',
  'subdomain2.host.com',
  'host2.com'
   ]
  }
};

The array contains all allowed host, you can also specify subdomians. check out more here

Answer 6

Rather than editing the webpack config file, the easier way to disable the host check is by adding a .env file to your root folder and putting this:

DANGEROUSLY_DISABLE_HOST_CHECK=true

As the variable name implies, disabling it is insecure and is only advisable to use only in dev environment.

Answer 7

If you have not ejected from CRA yet, you can't easily modify your webpack config. The config file is hidden in node_modules/react_scripts/config/webpackDevServer.config.js. You are discouraged to change that config.

Instead, you can just set the environment variable DANGEROUSLY_DISABLE_HOST_CHECK to true to disable the host check:

DANGEROUSLY_DISABLE_HOST_CHECK=true yarn start  
# or the equivalent npm command

Answer 8

If you are running webpack-dev-server in a container and are sending requests to it via its container name, you will get this error. To allow requests from other containers on the same network, simply provide the container name (or whatever name is used to resolve the container) using the --public option. This is better than disabling the security check entirely.

In my case, I was running webpack-dev-server in a container named assets with docker-compose. I changed the start command to this:

webpack-dev-server --mode development --host 0.0.0.0 --public assets

And the other container was now able to make requests via http://assets:5000.

Answer 9

If you are using create-react-app on C9 just run this command to start

npm run start --public $C9_HOSTNAME

And access the app from whatever your hostname is (eg type $C_HOSTNAME in the terminal to get the hostname)

Answer 10

Hello React Developers,

Instead of doing this disableHostCheck: true, in webpackDevServer.config.js. You can easily solve 'invalid host headers' error by adding a .env file to you project, add the variables HOST=0.0.0.0 and DANGEROUSLY_DISABLE_HOST_CHECK=true in .env file. If you want to make changes in webpackDevServer.config.js, you need to extract the react-scripts by using 'npm run eject' which is not recommended to do it. So the better solution is adding above mentioned variables in .env file of your project.

Happy Coding :)

Answer 11

I just experienced this issue while using the Windows Subsystem for Linux (WSL2), so I will also share this solution.

My objective was to render the output from webpack both at wsl:3000 and localhost:3000, thereby creating an alternate local endpoint.

As you might expect, this initially caused the "Invalid Host header" error to arise. Nothing seemed to help until I added the devServer config option shown below.

---

module.exports = {
  //...
  devServer: {
    proxy: [
      {
        context: ['http://wsl:3000'],
        target: 'http://localhost:3000',
      },
    ],
  },
}

---

This fixed the "bug" without introducing any security risks.

Reference: webpack DevServer docs

Answer 12

I solved this problem by adding proxying of the host header in the nginx configuration, like this:

server {
    listen 80;
    server_name     localhost:3000;

    location / {
        proxy_pass http://myservice:8080/;

        proxy_set_header HOST $host;
        proxy_set_header Referer $http_referer;
    }
}

I added that:

proxy_set_header HOST $host;

proxy_set_header Referer $http_referer;

Answer 13

Since webpack-dev-server 4 you need to add this to your config:

devServer: {
  firewall: false,
}

Answer 14

While using the default behavior (no config file) with webpack 5 related to this post: [https://stackoverflow.com/a/65268634/2544762`]

"scripts": {
    "dev": "webpack serve --mode development --env development --hot --port 3000"
    ...
    ...
},
"devDependencies": {
    ...
    "webpack": "^5.10.1",
    "webpack-cli": "^4.2.0"
},

With webpack 5 help webpack serve --help:

Usage: webpack serve|server|s [entries...] [options]

Run the webpack dev server.

Options:
  -c, --config <value...>     Provide path to a webpack configuration file e.g.
                              ./webpack.config.js.
  --config-name <value...>    Name of the configuration to use.
  -m, --merge                 Merge two or more configurations using
                              'webpack-merge'.
  --env <value...>            Environment passed to the configuration when it
                              is a function.
  --node-env <value>          Sets process.env.NODE_ENV to the specified value.
  --progress [value]          Print compilation progress during build.
  -j, --json [value]          Prints result as JSON or store it in a file.
  -d, --devtool <value>       Determine source maps to use.
  --no-devtool                Do not generate source maps.
  --entry <value...>          The entry point(s) of your application e.g.
                              ./src/main.js.
  --mode <value>              Defines the mode to pass to webpack.
  --name <value>              Name of the configuration. Used when loading
                              multiple configurations.
  -o, --output-path <value>   Output location of the file generated by webpack
                              e.g. ./dist/.
  --stats [value]             It instructs webpack on how to treat the stats
                              e.g. verbose.
  --no-stats                  Disable stats output.
  -t, --target <value...>     Sets the build target e.g. node.
  --no-target                 Negative 'target' option.
  --watch-options-stdin       Stop watching when stdin stream has ended.
  --no-watch-options-stdin    Do not stop watching when stdin stream has ended.
  --bonjour                   Broadcasts the server via ZeroConf networking on
                              start
  --lazy                      Lazy
  --liveReload                Enables/Disables live reloading on changing files
  --serveIndex                Enables/Disables serveIndex middleware
  --inline                    Inline mode (set to false to disable including
                              client scripts like livereload)
  --profile                   Print compilation profile data for progress steps
  --progress                  Print compilation progress in percentage
  --hot-only                  Do not refresh page if HMR fails
  --stdin                     close when stdin ends
  --open [value]              Open the default browser, or optionally specify a
                              browser name
  --useLocalIp                Open default browser with local IP
  --open-page <value>         Open default browser with the specified page
  --client-log-level <value>  Log level in the browser (trace, debug, info,
                              warn, error or silent)
  --https                     HTTPS
  --http2                     HTTP/2, must be used with HTTPS
  --key <value>               Path to a SSL key.
  --cert <value>              Path to a SSL certificate.
  --cacert <value>            Path to a SSL CA certificate.
  --pfx <value>               Path to a SSL pfx file.
  --pfx-passphrase <value>    Passphrase for pfx file.
  --content-base <value>      A directory or URL to serve HTML content from.
  --watch-content-base        Enable live-reloading of the content-base.
  --history-api-fallback      Fallback to /index.html for Single Page
                              Applications.
  --compress                  Enable gzip compression
  --port <value>              The port
  --disable-host-check        Will not check the host
  --socket <value>            Socket to listen
  --public <value>            The public hostname/ip address of the server
  --host <value>              The hostname/ip address the server will bind to
  --allowed-hosts <value...>  A list of hosts that are allowed to access the
                              dev server, separated by spaces

Global options:
  --color                     Enable colors on console.
  --no-color                  Disable colors on console.
  -v, --version               Output the version number of 'webpack',
                              'webpack-cli' and 'webpack-dev-server' and
                              commands.
  -h, --help [verbose]        Display help for commands and options.

To see list of all supported commands and options run 'webpack --help=verbose'.

Webpack documentation: https://webpack.js.org/.
CLI documentation: https://webpack.js.org/api/cli/.
Made with ♥ by the webpack team.
Done in 0.44s.

Solution

So, just add --disable-host-check with the webpack serve command do the trick.