Issue 4878 - Start using ESLint for adblockpluscore

lib/rsa.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+/* globals atob, console */
+
+"use strict";
+
 /**
  * This is a specialized RSA library meant only to verify SHA1-based signatures.
  */
 
 let {BigInteger} = require("jsbn");
 let Rusha = require("rusha");
 
 let rusha = new Rusha();
 
 // Define ASN.1 templates for the data structures used
-function seq()
+function seq(...args)
 {
-  return {type: 0x30, children: Array.prototype.slice.call(arguments)};
+  return {type: 0x30, children: args};
 }
 function obj(id)
 {
   return {type: 0x06, content: id};
 }
 function bitStr(contents)
 {
   return {type: 0x03, encapsulates: contents};
 }
 function intResult(id)
 {
   return {type: 0x02, out: id};
 }
 function octetResult(id)
 {
   return {type: 0x04, out: id};
 }
 
 // See http://www.cryptopp.com/wiki/Keys_and_Formats#RSA_PublicKey
 // 2A 86 48 86 F7 0D 01 01 01 means 1.2.840.113549.1.1.1
-var publicKeyTemplate = seq(seq(obj("\x2A\x86\x48\x86\xF7\x0D\x01\x01\x01"), {}), bitStr(seq(intResult("n"), intResult("e"))));
+let publicKeyTemplate = seq(
+  seq(obj("\x2A\x86\x48\x86\xF7\x0D\x01\x01\x01"), {}),
+  bitStr(seq(intResult("n"), intResult("e")))
+);
 
 // See http://tools.ietf.org/html/rfc3447#section-9.2 step 2
 // 2B 0E 03 02 1A means 1.3.14.3.2.26
-var signatureTemplate = seq(seq(obj("\x2B\x0E\x03\x02\x1A"), {}), octetResult("sha1"));
+let signatureTemplate = seq(
+  seq(obj("\x2B\x0E\x03\x02\x1A"), {}),
+  octetResult("sha1")
+);
 
 /**
  * Reads ASN.1 data matching the template passed in. This will throw an
  * exception if the data format doesn't match the template. On success an
  * object containing result properties is returned.
- *
- * See http://luca.ntop.org/Teaching/Appunti/asn1.html for info on the format.
+ * @see http://luca.ntop.org/Teaching/Appunti/asn1.html for info on the format.
+ * @param {String} data
+ * @param {Object} templ
+ * @returns {Object}
  */
 function readASN1(data, templ)
 {
-  var pos = 0;
+  let pos = 0;
   function next()
   {
     return data.charCodeAt(pos++);
   }
 
   function readLength()
   {
-    var len = next();
+    let len = next();
     if (len & 0x80)
     {
-      var cnt = len & 0x7F;
+      let cnt = len & 0x7F;
       if (cnt > 2 || cnt == 0)
         throw "Unsupported length";
 
       len = 0;
-      for (var i = 0; i < cnt; i++)
+      for (let i = 0; i < cnt; i++)
         len += next() << (cnt - 1 - i) * 8;
       return len;
     }
-    else
-      return len;
+    return len;
   }
 
   function readNode(curTempl)
   {
-    var type = next();
-    var len = readLength();
+    let type = next();
+    let len = readLength();
     if ("type" in curTempl && curTempl.type != type)
       throw "Unexpected type";
     if ("content" in curTempl && curTempl.content != data.substr(pos, len))
       throw "Unexpected content";
     if ("out" in curTempl)
       out[curTempl.out] = new BigInteger(data.substr(pos, len), 256);
     if ("children" in curTempl)
     {
-      var i, end;
+      let i;
+      let end;
       for (i = 0, end = pos + len; pos < end; i++)
       {
         if (i >= curTempl.children.length)
           throw "Too many children";
         readNode(curTempl.children[i]);
       }
       if (i < curTempl.children.length)
         throw "Too few children";
       if (pos > end)
         throw "Children too large";
     }
     else if ("encapsulates" in curTempl)
     {
       if (next() != 0)
         throw "Encapsulation expected";
       readNode(curTempl.encapsulates);
     }
     else
       pos += len;
   }
 
-  var out = {};
+  let out = {};
   readNode(templ);
   if (pos != data.length)
     throw "Too much data";
   return out;
 }
 
 /**
  * Reads a BER-encoded RSA public key. On success returns an object with the
  * properties n and e (the components of the key), otherwise null.
+ * @param {String} key
+ * @return {Object|null}
  */
 function readPublicKey(key)
 {
   try
   {
     return readASN1(atob(key), publicKeyTemplate);
   }
   catch (e)
   {
-    console.log("Invalid RSA public key: " + e);
+    console.warn("Invalid RSA public key: " + e);
     return null;
   }
 }
 
 /**
  * Checks whether the signature is valid for the given public key and data.
+ * @param {String} key
+ * @param {String} signature
+ * @param {String} data
+ * @return {Boolean}
  */
 function verifySignature(key, signature, data)
 {
-  var keyData = readPublicKey(key);
+  let keyData = readPublicKey(key);
   if (!keyData)
     return false;
 
   // We need the exponent as regular number
   keyData.e = parseInt(keyData.e.toString(16), 16);
 
   // Decrypt signature data using RSA algorithm
-  var sigInt = new BigInteger(atob(signature), 256);
-  var digest = sigInt.modPowInt(keyData.e, keyData.n).toString(256);
+  let sigInt = new BigInteger(atob(signature), 256);
+  let digest = sigInt.modPowInt(keyData.e, keyData.n).toString(256);
 
   try
   {
-    var pos = 0;
-    function next()
-    {
-      return digest.charCodeAt(pos++);
-    }
+    let pos = 0;
+    let next = () => digest.charCodeAt(pos++);
 
     // Skip padding, see http://tools.ietf.org/html/rfc3447#section-9.2 step 5
     if (next() != 1)
       throw "Wrong padding in signature digest";
-    while (next() == 255) {}
+    while (next() == 255)
+    {
+      // Empty
+    }
     if (digest.charCodeAt(pos - 1) != 0)
       throw "Wrong padding in signature digest";
 
     // Rest is an ASN.1 structure, get the SHA1 hash from it and compare to
     // the real one
-    var sha1 = readASN1(digest.substr(pos), signatureTemplate).sha1;
-    var expected = new BigInteger(rusha.digest(data), 16);
+    let {sha1} = readASN1(digest.substr(pos), signatureTemplate);
+    let expected = new BigInteger(rusha.digest(data), 16);
     return (sha1.compareTo(expected) == 0);
   }
   catch (e)
   {
-    console.log("Invalid encrypted signature: " + e);
+    console.warn("Invalid encrypted signature: " + e);
     return false;
   }
 }
 exports.verifySignature = verifySignature;