Fixed wrongly rejected RSA signatures

lib/rsa.js

Index: lib/rsa.js
===================================================================
--- a/lib/rsa.js
+++ b/lib/rsa.js
@@ -9,183 +9,185 @@
  * 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
-      var sha1 = readASN1(digest.substr(pos), signatureTemplate).sha1;
-      return (sha1.toString(16) == SHA1(data));
-    }
-    catch (e)
-    {
-      console.log("Invalid encrypted signature: " + e);
-      return false;
-    }
-  }
-
-  // Export verifySignature function, everything else is private.
-  globalObj.verifySignature = verifySignature;
-})(this);
+
+
+/**
+ * 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
+      var sha1 = readASN1(digest.substr(pos), signatureTemplate).sha1.toString(16);
+      while (sha1.length < 40)
+        sha1 = "0" + sha1;  // Zero-pad to the right length
+      return (sha1 == SHA1(data));
+    }
+    catch (e)
+    {
+      console.log("Invalid encrypted signature: " + e);
+      return false;
+    }
+  }
+
+  // Export verifySignature function, everything else is private.
+  globalObj.verifySignature = verifySignature;
+})(this);