ECSignature: add missing tests for R,S length

src/ecsignature.js

@@ -42,7 +42,7 @@ ECSignature.fromDER = function(buffer) {
   assert.equal(buffer.readUInt8(offset), 0x02, 'Expected a DER integer (2)')
 
   var sLen = buffer.readUInt8(offset + 1)
-  assert(sLen > 0, 'R length is zero')
+  assert(sLen > 0, 'S length is zero')
 
   var rB = buffer.slice(4, offset)
   var sB = buffer.slice(offset + 2)

test/fixtures/ecsignature.json

@@ -149,6 +149,14 @@
         "exception": "Invalid DER encoding",
         "hex": "300c020400ffffff020200ffffff"
       },
+      {
+        "exception": "R length is zero",
+        "hex": "30080200020400ffffff"
+      },
+      {
+        "exception": "S length is zero",
+        "hex": "3008020400ffffff0200"
+      },
       {
         "exception": "R value is negative",
         "hex": "300c0204ffffffff020400ffffff"