der: support negative integers

indutny · Jul 24, 2019 · e5a10a3 · e5a10a3
1 parent 48811c6
commit e5a10a3
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Showing 2 changed files with 10 additions and 14 deletions.
diff --git 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
@@ -199,22 +199,18 @@ 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);
+    if (num.isZero()) {
+      num = Buffer.from([0]);
+    } else {
+      const numArray = num.toTwos(num.byteLength() * 8).toArray();
+      if (num.isNeg() != Boolean(numArray[0] & 0x80)) {
+        numArray.unshift(num.isNeg() ? 0xff : 0);
+      }
+      num = Buffer.from(numArray);
     }
-    num = new Buffer(numArray);
   }
 
-  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);
+  return this._createEncoderBuffer(num);
 };
 
 DERNode.prototype._encodeBool = function encodeBool(value) {