From 48811c64e485fadb74ecf654606a31bf1f984e4b Mon Sep 17 00:00:00 2001
From: Jack Bates <jack@nottheoilrig.com>
Date: Wed, 24 Jul 2019 15:16:08 -0700
Subject: [PATCH 1/2] der: encode integers > 4294967295 and BigInts

---
 lib/asn1/encoders/der.js | 43 +++++++++++-----------------------------
 1 file changed, 12 insertions(+), 31 deletions(-)

diff --git a/lib/asn1/encoders/der.js b/lib/asn1/encoders/der.js
index 7fc89f8..45a5a61 100644
--- a/lib/asn1/encoders/der.js
+++ b/lib/asn1/encoders/der.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const inherits = require('inherits');
+const BN = require('bn.js');
 const Buffer = require('buffer').Buffer;
 const Node = require('../base/node');
 
@@ -194,7 +195,10 @@ DERNode.prototype._encodeInt = function encodeInt(num, values) {
   }
 
   // Bignum, assume big endian
-  if (typeof num !== 'number' && !Buffer.isBuffer(num)) {
+  if (!Buffer.isBuffer(num)) {
+    if (!BN.isBN(num)) {
+      num = new BN(num);
+    }
     const numArray = num.toArray();
     if (!num.sign && numArray[0] & 0x80) {
       numArray.unshift(0);
@@ -202,38 +206,15 @@ DERNode.prototype._encodeInt = function encodeInt(num, values) {
     num = new Buffer(numArray);
   }
 
-  if (Buffer.isBuffer(num)) {
-    let size = num.length;
-    if (num.length === 0)
-      size++;
-
-    const out = new Buffer(size);
-    num.copy(out);
-    if (num.length === 0)
-      out[0] = 0;
-    return this._createEncoderBuffer(out);
-  }
-
-  if (num < 0x80)
-    return this._createEncoderBuffer(num);
-
-  if (num < 0x100)
-    return this._createEncoderBuffer([0, num]);
-
-  let size = 1;
-  for (let i = num; i >= 0x100; i >>= 8)
+  let size = num.length;
+  if (num.length === 0)
     size++;
 
-  const out = new Array(size);
-  for (let i = out.length - 1; i >= 0; i--) {
-    out[i] = num & 0xff;
-    num >>= 8;
-  }
-  if(out[0] & 0x80) {
-    out.unshift(0);
-  }
-
-  return this._createEncoderBuffer(new Buffer(out));
+  const out = new Buffer(size);
+  num.copy(out);
+  if (num.length === 0)
+    out[0] = 0;
+  return this._createEncoderBuffer(out);
 };
 
 DERNode.prototype._encodeBool = function encodeBool(value) {

From 4e61ada60efebd8da61701afee0f379b3141930e Mon Sep 17 00:00:00 2001
From: Jack Bates <jack@nottheoilrig.com>
Date: Wed, 24 Jul 2019 15:24:06 -0700
Subject: [PATCH 2/2] der: support negative integers

---
 lib/asn1/decoders/der.js | 2 +-
 lib/asn1/encoders/der.js | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/asn1/decoders/der.js b/lib/asn1/decoders/der.js
index c5b0515..f76fea8 100644
--- a/lib/asn1/decoders/der.js
+++ b/lib/asn1/decoders/der.js
@@ -253,7 +253,7 @@ DERNode.prototype._decodeBool = function decodeBool(buffer) {
 DERNode.prototype._decodeInt = function decodeInt(buffer, values) {
   // Bigint, return as it is (assume big endian)
   const raw = buffer.raw();
-  let res = new bignum(raw);
+  let res = new bignum(raw).fromTwos(raw.length * 8);
 
   if (values)
     res = values[res.toString(10)] || res;
diff --git a/lib/asn1/encoders/der.js b/lib/asn1/encoders/der.js
index 45a5a61..153bfe8 100644
--- a/lib/asn1/encoders/der.js
+++ b/lib/asn1/encoders/der.js
@@ -199,9 +199,9 @@ DERNode.prototype._encodeInt = function encodeInt(num, values) {
     if (!BN.isBN(num)) {
       num = new BN(num);
     }
-    const numArray = num.toArray();
-    if (!num.sign && numArray[0] & 0x80) {
-      numArray.unshift(0);
+    const numArray = num.toTwos(num.byteLength() * 8).toArray();
+    if (num.isNeg() !== Boolean(numArray[0] & 0x80)) {
+      numArray.unshift(num.isNeg() ? 0xff : 0);
     }
     num = new Buffer(numArray);
   }