[safari] Issue 4902 - Partially revert d5be57b68f91 for Safari compatibility

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/>.
+ */
+
+
+/**
+ * This is a specialized RSA library meant only to verify SHA1-based signatures.
+ * It requires jsbn.js and sha1.js to work.
+ */
+
+(function(globalObj)
+{
+  // Define ASN.1 templates for the data structures used
+  function seq()
+  {
+    return {type: 0x30, children: Array.prototype.slice.call(arguments)};
+  }
+  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"))));
+
+  // 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"));
+
+  /**
+   * 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.
+   */
+  function readASN1(data, templ)
+  {
+    var pos = 0;
+    function next()
+    {
+      return data.charCodeAt(pos++);
+    }
+
+    function readLength()
+    {
+      var len = next();
+      if (len & 0x80)
+      {
+        var cnt = len & 0x7F;
+        if (cnt > 2 || cnt == 0)
+          throw "Unsupported length";
+
+        len = 0;
+        for (var i = 0; i < cnt; i++)
+          len += next() << (cnt - 1 - i) * 8;
+        return len;
+      }
+      else
+        return len;
+    }
+
+    function readNode(curTempl)
+    {
+      var type = next();
+      var 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;
+        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 = {};
+    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.
+   */
+  function readPublicKey(key)
+  {
+    try
+    {
+      return readASN1(atob(key), publicKeyTemplate);
+    }
+    catch (e)
+    {
+      console.log("Invalid RSA public key: " + e);
+      return null;
+    }
+  }
+
+  /**
+   * Checks whether the signature is valid for the given public key and data.
+   */
+  function verifySignature(key, signature, data)
+  {
+    var 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);
+
+    try
+    {
+      var pos = 0;
+      function next()
+      {
+        return 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) {}
+      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(SHA1(data), 16);
+      return (sha1.compareTo(expected) == 0);
+    }
+    catch (e)
+    {
+      console.log("Invalid encrypted signature: " + e);
+      return false;
+    }
+  }
+
+  // Export verifySignature function, everything else is private.
+  globalObj.verifySignature = verifySignature;
+})(this);