Add proxy example (#225)

* Add proxy example

* Updated after review comments

proxy-blocker/README.md

@@ -0,0 +1,22 @@
+# proxy-filter
+
+## What it does
+
+This add-on registers a [PAC script](https://developer.mozilla.org/en-US/docs/Web/HTTP/Proxy_servers_and_tunneling/Proxy_Auto-Configuration_%28PAC%29_file) using the proxy API.
+
+The PAC script is initialized with a list of hostnames: it blocks requests to any hosts that are in the list.
+
+The list is given the following default values: `["example.com", "example.org"]`, but the user can add and remove hosts using the add-on's options page.
+
+Note that the hostname-matching is very simple: hostnames must exactly match an entry in the list if they are to be blocked. So with the default settings, "example.org" would be blocked but "www.example.org" would be permitted.
+
+To try it out:
+* install it
+* try visiting `http://example.com`, and see it is blocked
+* visit `about:addons`, open the add-on's preferences, and try changing the hostnames in the text box
+* try visiting some different pages, to see the effect of your changes.
+
+## What it shows
+
+* How to implement a simple PAC script, and register it using the proxy API.
+* How to exchange messages between a PAC script and a background script.

proxy-blocker/background/proxy-handler.js

@@ -0,0 +1,55 @@
+// Location of the proxy script, relative to manifest.json
+const proxyScriptURL = "proxy/proxy-script.js";
+
+// Default settings. If there is nothing in storage, use these values.
+const defaultSettings = {
+   blockedHosts: ["example.com", "example.org"]
+ }
+
+// Register the proxy script
+browser.proxy.registerProxyScript(proxyScriptURL);
+
+// Log any errors from the proxy script
+browser.proxy.onProxyError.addListener(error => {
+  console.error(`Proxy error: ${error.message}`);
+});
+
+// Initialize the proxy
+function handleInit(message) {
+  // update the proxy whenever stored settings change
+  browser.storage.onChanged.addListener((newSettings) => {
+    browser.runtime.sendMessage(newSettings.blockedHosts.newValue, {toProxyScript: true});
+  });
+
+  // get the current settings, then...
+  browser.storage.local.get()
+    .then((storedSettings) => {
+      // if there are stored settings, update the proxy with them...
+      if (storedSettings.blockedHosts) {
+        browser.runtime.sendMessage(storedSettings.blockedHosts, {toProxyScript: true});
+      // ...otherwise, initialize storage with the default values
+      } else {
+        browser.storage.local.set(defaultSettings);
+      }
+
+    })
+    .catch(()=> {
+      console.log("Error retrieving stored settings");
+    });
+}
+
+function handleMessage(message, sender) {
+  // only handle messages from the proxy script
+  if (sender.url !=  browser.extension.getURL(proxyScriptURL)) {
+    return;
+  }
+
+  if (message === "init") {
+    handleInit(message);
+  } else {
+    // after the init message the only other messages are status messages
+    console.log(message);
+  }
+}
+
+browser.runtime.onMessage.addListener(handleMessage);

proxy-blocker/icons/LICENSE

@@ -0,0 +1 @@
+The "lock".svg" icon is taken from the Material Core iconset and is used under the terms of its license: https://www.iconfinder.com/iconsets/material-core.

proxy-blocker/icons/block.svg

@@ -0,0 +1 @@
+<?xml version="1.0" ?><svg height="20px" version="1.1" viewBox="0 0 20 20" width="20px" xmlns="http://www.w3.org/2000/svg" xmlns:sketch="http://www.bohemiancoding.com/sketch/ns" xmlns:xlink="http://www.w3.org/1999/xlink"><title/><desc/><defs/><g fill="none" fill-rule="evenodd" id="Page-1" stroke="none" stroke-width="1"><g fill="#000000" id="Core" transform="translate(-170.000000, -44.000000)"><g id="block" transform="translate(170.000000, 44.000000)"><path d="M10,0 C4.5,0 0,4.5 0,10 C0,15.5 4.5,20 10,20 C15.5,20 20,15.5 20,10 C20,4.5 15.5,0 10,0 L10,0 Z M2,10 C2,5.6 5.6,2 10,2 C11.8,2 13.5,2.6 14.9,3.7 L3.7,14.9 C2.6,13.5 2,11.8 2,10 L2,10 Z M10,18 C8.2,18 6.5,17.4 5.1,16.3 L16.3,5.1 C17.4,6.5 18,8.2 18,10 C18,14.4 14.4,18 10,18 L10,18 Z" id="Shape"/></g></g></g></svg>

proxy-blocker/manifest.json

@@ -0,0 +1,31 @@
+{
+
+  "manifest_version": 2,
+  "name": "Proxy-blocker",
+  "description": "Uses the proxy API to block requests to specific hosts.",
+  "version": "1.0",
+
+  "icons": {
+    "48": "icons/block.svg",
+    "96": "icons/block.svg"
+  },
+
+  "applications": {
+    "gecko": {
+      "strict_min_version": "55.0a1"
+    }
+  },
+
+  "background": {
+    "scripts": [
+      "background/proxy-handler.js"
+    ]
+  },
+
+  "options_ui": {
+    "page": "options/options.html"
+  },
+
+  "permissions": ["proxy", "storage"]
+
+}

proxy-blocker/options/options.css

@@ -0,0 +1,14 @@
+body {
+  width: 25em;
+  font-family: "Open Sans Light", sans-serif;
+  font-size: 0.9em;
+  font-weight: 300;
+}
+
+.title, #blocked-hosts {
+  margin: 1em;
+}
+
+.title {
+  font-size: 1.2em;
+}

proxy-blocker/options/options.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+
+<html>
+  <head>
+    <meta charset="utf-8">
+    <link rel="stylesheet" href="options.css"/>
+  </head>
+
+  <body>
+
+    <section>
+      <span class="title">Hosts to block:</span>
+      <textarea id="blocked-hosts" rows="10" cols="50"></textarea>
+    </section>
+
+    <script src="options.js"></script>
+  </body>
+
+</html>

proxy-blocker/options/options.js

@@ -0,0 +1,25 @@
+const blockedHostsTextArea = document.querySelector("#blocked-hosts");
+
+// Store the currently selected settings using browser.storage.local.
+function storeSettings() {
+  let blockedHosts = blockedHostsTextArea.value.split("\n");
+  browser.storage.local.set({
+    blockedHosts
+  });
+}
+
+// Update the options UI with the settings values retrieved from storage,
+// or the default settings if the stored settings are empty.
+function updateUI(restoredSettings) {
+  blockedHostsTextArea.value = restoredSettings.blockedHosts.join("\n");
+}
+
+function onError(e) {
+  console.error(e);
+}
+
+// On opening the options page, fetch stored settings and update the UI with them.
+browser.storage.local.get().then(updateUI, onError);
+
+// Whenever the contents of the textarea changes, save the new values
+blockedHostsTextArea.addEventListener("change", storeSettings);

proxy-blocker/proxy/proxy-script.js

@@ -0,0 +1,21 @@
+var blockedHosts = [];
+const allow = "DIRECT 1234";
+const deny = "PROXY 127.0.0.1:65535";
+
+// tell the background script that we are ready
+browser.runtime.sendMessage("init");
+
+// listen for updates to the blocked host list
+browser.runtime.onMessage.addListener((message) => {
+  blockedHosts = message;
+});
+
+// required PAC function that will be called to determine
+// if a proxy should be used.
+function FindProxyForURL(url, host) {
+  if (blockedHosts.indexOf(host) != -1) {
+    browser.runtime.sendMessage(`Proxy-blocker: blocked ${url}`);
+    return deny;
+  }
+  return allow;
+}