Bug 991970 - Part 3: add permission check. r=smaug

From 6462cdf51f04b81479932f1b7b1d809970820620 Mon Sep 17 00:00:00 2001
---
 dom/nfc/nsNfc.js         | 23 +++++++++++++++++++++++
 dom/webidl/MozNFC.webidl |  1 +
 2 files changed, 24 insertions(+)

dom/nfc/nsNfc.js

@@ -224,6 +224,10 @@ mozNfc.prototype = {
       return;
     }
 
+    if (!this.checkPermissions(["nfc-read", "nfc-write"])) {
+      return;
+    }
+
     let tag = new MozNFCTag(this._window, sessionToken);
     let tagContentObj = this._window.MozNFCTag._create(this._window, tag);
 
@@ -253,6 +257,10 @@ mozNfc.prototype = {
       return;
     }
 
+    if (!this.checkPermissions(["nfc-read", "nfc-write"])) {
+      return;
+    }
+
     debug("fire ontaglost " + sessionToken);
     let event = new this._window.Event("taglost");
     this.__DOM_IMPL__.dispatchEvent(event);
@@ -297,6 +305,21 @@ mozNfc.prototype = {
     this.__DOM_IMPL__.dispatchEvent(event);
   },
 
+  checkPermissions: function checkPermissions(perms) {
+    let principal = this._window.document.nodePrincipal;
+    for (let perm of perms) {
+      let permValue =
+        Services.perms.testExactPermissionFromPrincipal(principal, perm);
+      if (permValue == Ci.nsIPermissionManager.ALLOW_ACTION) {
+        return true;
+      } else {
+        debug("doesn't have " + perm + " permission.");
+      }
+    }
+
+    return false;
+  },
+
   hasDeadWrapper: function hasDeadWrapper() {
     return Cu.isDeadWrapper(this._window) || Cu.isDeadWrapper(this.__DOM_IMPL__);
   },

dom/webidl/MozNFC.webidl

@@ -82,6 +82,7 @@ interface MozNFC : EventTarget {
   /**
    * This event will be fired if the tag detected in ontagfound has been removed.
    */
+  [CheckPermissions="nfc-read nfc-write"]
   attribute EventHandler ontaglost;
 };