Move CSP logic to new file, Fix boolean config examples

Not sure why I was quoting these in the first place

5 files changed, 91 insertions, 81 deletions

diff --git a/README.md b/README.md
index d71eb1c5..2633b3b6 100644
--- a/README.md
+++ b/README.md
@@ -171,8 +171,8 @@ Application settings `config.json`
 | port | `80` | web app port |
 | alloworigin | `['localhost']` | domain name whitelist |
 | usessl | `true` or `false` | set to use ssl server (if true will auto turn on `protocolusessl`) |
-| hsts | `{"enable": "true", "maxAgeSeconds": "31536000", "includeSubdomains": "true", "preload": "true"}` | [HSTS](https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security) options to use with HTTPS (default is the example value, max age is a year) |
-| csp | `{"enable": "true", "directives": {"scriptSrc": "trustwodthy-scripts.example.com"}, "upgradeInsecureRequests": "auto", "addDefaults": "true"}` | Configures [Content Security Policy](https://helmetjs.github.io/docs/csp/). Directives are directly passed to Helmet, so [their format](https://helmetjs.github.io/docs/csp/) applies. Further, some defaults are added so  that the application doesn't break. To disable adding these defaults, set `addDefaults` to `false`. If `usecdn` is on, default CDN locations are allowed too. By default (`auto`), insecure (HTTP) requests are upgraded to HTTPS via CSP if `usessl` is on. To change this behaviour, set `upgradeInsecureRequests` to either `true` or `false`. |
+| hsts | `{"enable": true, "maxAgeSeconds": 31536000, "includeSubdomains": true, "preload": true}` | [HSTS](https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security) options to use with HTTPS (default is the example value, max age is a year) |
+| csp | `{"enable": true, "directives": {"scriptSrc": "trustworthy-scripts.example.com"}, "upgradeInsecureRequests": "auto", "addDefaults": true}` | Configures [Content Security Policy](https://helmetjs.github.io/docs/csp/). Directives are passed to Helmet - see [their documentation](https://helmetjs.github.io/docs/csp/) for more information on the format. Some defaults are added to the configured values so that the application doesn't break. To disable this behaviour, set `addDefaults` to `false`. Further, if `usecdn` is on, some CDN locations are allowed too. By default (`auto`), insecure (HTTP) requests are upgraded to HTTPS via CSP if `usessl` is on. To change this behaviour, set `upgradeInsecureRequests` to either `true` or `false`. |
 | protocolusessl | `true` or `false` | set to use ssl protocol for resources path (only applied when domain is set) |
 | urladdport | `true` or `false` | set to add port on callback url (port 80 or 443 won't applied) (only applied when domain is set) |
 | usecdn | `true` or `false` | set to use CDN resources or not (default is `true`) |
diff --git a/app.js b/app.js
index cdabc7d7..055b8f4c 100644
--- a/app.js
+++ b/app.js
@@ -12,7 +12,6 @@ var session = require('express-session')
 var SequelizeStore = require('connect-session-sequelize')(session.Store)
 var fs = require('fs')
 var path = require('path')
-var uuid = require('uuid')
 
 var morgan = require('morgan')
 var passportSocketIo = require('passport.socketio')
@@ -25,6 +24,7 @@ var config = require('./lib/config')
 var logger = require('./lib/logger')
 var response = require('./lib/response')
 var models = require('./lib/models')
+var csp = require('./lib/csp')
 
 // generate front-end constants by template
 var constpath = path.join(__dirname, './public/js/lib/common/constant.ejs')
@@ -109,83 +109,14 @@ if (config.hsts.enable) {
   logger.info('https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security')
 }
 
-app.use((req, res, next) => {
-  res.locals.nonce = uuid.v4()
-  next()
-})
+// Generate a random nonce per request, for CSP with inline scripts
+app.use(csp.addNonceToLocals)
 
 // use Content-Security-Policy to limit XSS, dangerous plugins, etc.
 // https://helmetjs.github.io/docs/csp/
-function getCspNonce (req, res) {
-  return "'nonce-" + res.locals.nonce + "'"
-}
-
-function getCspWebSocketUrl (req, res) {
-  // wss: is included in 'self', but 'ws:' is not
-  return (req.protocol === 'http' ? 'ws:' : 'wss:') + config.serverurl.replace(/https?:/, "")
-}
-
-function mergeWithDefaults(configured, defaultDirective, cdnDirective) {
-  var directive = [].concat(configured)
-  if (config.csp.addDefaults && defaultDirective) {
-    directive = directive.concat(defaultDirective)
-  }
-  if (config.usecdn && cdnDirective) {
-    directive = directive.concat(cdnDirective)
-  }
-  return directive
-}
-
 if (config.csp.enable) {
-  var defaultDirectives = {
-    defaultSrc: ['\'self\''],
-    scriptSrc: ['\'self\'', 'vimeo.com', 'https://gist.github.com', 'www.slideshare.net', 'https://query.yahooapis.com', 'https://*.disqus.com', '\'unsafe-eval\''], // TODO: Remove unsafe-eval - webpack script-loader issues
-    imgSrc: ['*'],
-    styleSrc: ['\'self\'', '\'unsafe-inline\'', 'https://assets-cdn.github.com'], // unsafe-inline is required for some libs, plus used in views
-    fontSrc: ['\'self\'', 'https://public.slidesharecdn.com'],
-    objectSrc: ['*'], // Chrome PDF viewer treats PDFs as objects :/
-    childSrc: ['*'],
-    connectSrc: ['*']
-  };
-  var cdnDirectives = {
-    scriptSrc: ['https://cdnjs.cloudflare.com', 'https://cdn.mathjax.org'],
-    styleSrc: ['https://cdnjs.cloudflare.com', 'https://fonts.googleapis.com'],
-    fontSrc: ['https://cdnjs.cloudflare.com', 'https://fonts.gstatic.com']
-  }
-  var directives = {}
-  for (var propertyName in config.csp.directives) {
-    if (config.csp.directives.hasOwnProperty(propertyName)) {
-      directives[propertyName] = mergeWithDefaults(
-        config.csp.directives[propertyName],
-        defaultDirectives[propertyName],
-        cdnDirectives[propertyName]
-      )
-    }
-  }
-  for (var propertyName in defaultDirectives) {
-    if (!directives[propertyName]) {
-      directives[propertyName] = mergeWithDefaults(
-        [],
-        defaultDirectives[propertyName],
-        cdnDirectives[propertyName]
-      )
-    }
-  }
-  if (directives.scriptSrc.indexOf('\'unsafe-inline\'') === -1) {
-    directives.scriptSrc.push(getCspNonce)
-    // TODO: This is the SHA-256 hash of the inline script in
-    // build/reveal.js/plugins/notes/notes.html . Any cleaner
-    // solution appreciated.
-    directives.scriptSrc.push('\'sha256-EtvSSxRwce5cLeFBZbvZvDrTiRoyoXbWWwvEVciM5Ag=\'')
-  }
-  directives.connectSrc.push(getCspWebSocketUrl)
-  if (config.csp.upgradeInsecureRequests === 'auto') {
-    directives.upgradeInsecureRequests = config.usessl === 'true'
-  } else {
-    directives.upgradeInsecureRequests = config.csp.upgradeInsecureRequests === 'true'
-  }
   app.use(helmet.contentSecurityPolicy({
-    directives: directives
+    directives: csp.computeDirectives()
   }))
 } else {
   logger.info('Content-Security-Policy is disabled. This may be a security risk.')
diff --git a/config.json.example b/config.json.example
index 7e4394b0..98658770 100644
--- a/config.json.example
+++ b/config.json.example
@@ -17,17 +17,17 @@
     "production": {
         "domain": "localhost",
         "hsts": {
-            "enable": "true",
+            "enable": true,
             "maxAgeSeconds": "31536000",
-            "includeSubdomains": "true",
-            "preload": "true"
+            "includeSubdomains": true,
+            "preload": true
         },
         csp: {
-	    "enable": "true",
+            "enable": true,
             "directives": {
             },
             "upgradeInsecureRequests": "auto"
-            "addDefaults": "true"
+            "addDefaults": true
         },
         "db": {
             "username": "",
diff --git a/lib/csp.js b/lib/csp.js
new file mode 100644
index 00000000..509bc530
--- /dev/null
+++ b/lib/csp.js
@@ -0,0 +1,80 @@
+var config = require('./config')
+var uuid = require('uuid')
+
+var CspStrategy = {}
+
+var defaultDirectives = {
+  defaultSrc: ['\'self\''],
+  scriptSrc: ['\'self\'', 'vimeo.com', 'https://gist.github.com', 'www.slideshare.net', 'https://query.yahooapis.com', 'https://*.disqus.com', '\'unsafe-eval\''],
+  // ^ TODO: Remove unsafe-eval - webpack script-loader issues https://github.com/hackmdio/hackmd/issues/594
+  imgSrc: ['*'],
+  styleSrc: ['\'self\'', '\'unsafe-inline\'', 'https://assets-cdn.github.com'], // unsafe-inline is required for some libs, plus used in views
+  fontSrc: ['\'self\'', 'https://public.slidesharecdn.com'],
+  objectSrc: ['*'], // Chrome PDF viewer treats PDFs as objects :/
+  childSrc: ['*'],
+  connectSrc: ['*']
+}
+
+var cdnDirectives = {
+  scriptSrc: ['https://cdnjs.cloudflare.com', 'https://cdn.mathjax.org'],
+  styleSrc: ['https://cdnjs.cloudflare.com', 'https://fonts.googleapis.com'],
+  fontSrc: ['https://cdnjs.cloudflare.com', 'https://fonts.gstatic.com']
+}
+
+CspStrategy.computeDirectives = function () {
+  var directives = {}
+  mergeDirectives(directives, config.csp.directives)
+  mergeDirectivesIf(config.csp.addDefaults, directives, defaultDirectives)
+  mergeDirectivesIf(config.usecdn, directives, cdnDirectives)
+  if (!areAllInlineScriptsAllowed(directives)) {
+    addInlineScriptExceptions(directives)
+  }
+  addUpgradeUnsafeRequestsOptionTo(directives)
+  return directives
+}
+
+function mergeDirectives (existingDirectives, newDirectives) {
+  for (var propertyName in newDirectives) {
+    var newDirective = newDirectives[propertyName]
+    if (newDirective) {
+      var existingDirective = existingDirectives[propertyName] || []
+      existingDirectives[propertyName] = existingDirective.concat(newDirective)
+    }
+  }
+}
+
+function mergeDirectivesIf (condition, existingDirectives, newDirectives) {
+  if (condition) {
+    mergeDirectives(existingDirectives, newDirectives)
+  }
+}
+
+function areAllInlineScriptsAllowed (directives) {
+  return directives.scriptSrc.indexOf('\'unsafe-inline\'') !== -1
+}
+
+function addInlineScriptExceptions (directives) {
+  directives.scriptSrc.push(getCspNonce)
+  // TODO: This is the SHA-256 hash of the inline script in build/reveal.js/plugins/notes/notes.html
+  // Any more clean solution appreciated.
+  directives.scriptSrc.push('\'sha256-EtvSSxRwce5cLeFBZbvZvDrTiRoyoXbWWwvEVciM5Ag=\'')
+}
+
+function getCspNonce (req, res) {
+  return "'nonce-" + res.locals.nonce + "'"
+}
+
+function addUpgradeUnsafeRequestsOptionTo (directives) {
+  if (config.csp.upgradeInsecureRequests === 'auto' && config.usessl) {
+    directives.upgradeInsecureRequests = true
+  } else if (config.csp.upgradeInsecureRequests === true) {
+    directives.upgradeInsecureRequests = true
+  }
+}
+
+CspStrategy.addNonceToLocals = function (req, res, next) {
+  res.locals.nonce = uuid.v4()
+  next()
+}
+
+module.exports = CspStrategy
diff --git a/public/js/index.js b/public/js/index.js
index 25bd1c36..56522e9c 100644
--- a/public/js/index.js
+++ b/public/js/index.js
@@ -3,7 +3,6 @@
    modeType, Idle, serverurl, key, gapi, Dropbox, FilePicker
    ot, MediaUploader, hex2rgb, num_loaded, Visibility */
 
-
 require('../vendor/showup/showup')
 
 require('../css/index.css')