Restrict access based on Referer

2 files changed, 59 insertions, 1 deletions

diff --git a/lib/app.js b/lib/app.js
index d4f0c98..d779b12 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -25,6 +25,7 @@ var fs = require('fs')
 var mkdirp = require('mkdirp')
 var Base64URL = require('base64-url')
 var ssbKeys = require('ssb-keys')
+var Url = require('url')
 
 var zeros = new Buffer(24); zeros.fill(0)
 
@@ -81,6 +82,27 @@ function App(sbot, config) {
     }
   }).filter(Boolean)
 
+  this.trustedReferers = u.toArray(conf.trustedReferers || ['http://localhost:/', 'http://127.0.0.1:/', 'http://[::1]:/', 'http://' + this.hostname + '/'])
+  this.trustedReferersParsed = this.trustedReferers.indexOf('*') > -1 ? [{
+    subdomains: true,
+    host: '',
+    port: '*',
+  }] : this.trustedReferers.map(function (pattern) {
+    var m = /^([a-z0-9\-+]+:)?\/\/+(\.)?(?:\[([0-9a-f:]*)\]|([^:/]*))(:([0-9]*?|\*))?(\/.*?)?$/.exec(pattern)
+    if (!m) return void console.trace('Unable to parse URL pattern "'+pattern+'"')
+    var port = !m[5] ? 80 :
+               !m[6] ? Number(self.port) :
+        '*' === m[6] ? '*' : Number(m[6])
+    if (port !== '*' && isNaN(port)) return void console.trace('Unable to parse port in URL pattern "'+pattern+'". Default port: "'+self.port+'"')
+    return {
+      protocol: m[1],
+      subdomains: !!m[2],
+      hostname: m[3] || m[4],
+      port: port,
+      path: m[7]
+    }
+  }).filter(Boolean)
+
   var base = conf.base || '/'
   this.opts = {
     base: base,
@@ -152,6 +174,22 @@ App.prototype.isAllowedHostHeader = function (hostname) {
   return false
 }
 
+App.prototype.getRefererPath = function (referer) {
+  if (!referer) return
+  var url = Url.parse(referer)
+  var port = Number(url.port || 80)
+  for (var i = 0; i < this.trustedReferersParsed.length; i++) {
+    var allow = this.trustedReferersParsed[i]
+    if ((!allow.protocol || allow.protocol === url.protocol)
+      && (allow.port === '*' || allow.port === port)
+      && (allow.hostname === '' || allow.hostname === url.hostname ||
+        (allow.subdomains && host.endsWith('.'+allow.hostname)))
+      && (!allow.path || url.pathname.startsWith(allow.path))
+    ) return allow.path ? url.pathname.substr(allow.path.length) : url.pathname
+  }
+  return null
+}
+
 App.prototype.go = function () {
   var self = this
   var server = http.createServer(function (req, res) {
diff --git a/lib/serve.js b/lib/serve.js
index fdf24f7..414cef5 100644
--- a/lib/serve.js
+++ b/lib/serve.js
@@ -122,6 +122,19 @@ Serve.prototype.go = function () {
     Boolean(conf.replyMentionFeeds)
 
   if (this.req.method === 'POST' || this.req.method === 'PUT') {
+    var referer = this.req.headers.referer
+    var refererPath = this.app.getRefererPath(referer)
+    if (!refererPath) {
+      if (!referer) console.error('Missing referer')
+      else console.error('Referer not allowed: "' + referer + '"')
+      this.res.writeHead(403)
+      return this.res.end('Forbidden')
+    }
+    if (this.isUnsafePath(refererPath)) {
+      console.error('Unsafe referer path not allowed: "' + refererPath + '"')
+      this.res.writeHead(403)
+      return this.res.end('Forbidden')
+    }
     if (/^multipart\/form-data/.test(this.req.headers['content-type'])) {
       var data = {}
       var erred
@@ -213,6 +226,14 @@ Serve.prototype.go = function () {
   }
 }
 
+Serve.prototype.isUnsafePath = function (path) {
+  return typeof path !== 'string'
+    || /^&|^%26/.test(path)
+    || path.indexOf('../') !== -1
+    || path.startsWith('/web/')
+    || path.startsWith('/npm-readme/')
+}
+
 Serve.prototype.saveDraft = function (content, cb) {
   var self = this
   var data = self.data
@@ -2426,7 +2447,6 @@ Serve.prototype.wrapPage = function (title, searchQ) {
       var done = multicb({pluck: 1, spread: true})
       done()(null, h('html', h('head',
         h('meta', {charset: 'utf-8'}),
-        h('meta', {name: 'referrer', content: 'no-referrer'}),
         h('title', title),
         h('meta', {name: 'viewport', content: 'width=device-width,initial-scale=1'}),
         h('link', {rel: 'icon', href: render.toUrl('/static/hermie.ico'), type: 'image/x-icon'}),