[Fix] Buffer.concat looses taint nodejs#20

lib/_taint_buffer_util.js

@@ -284,6 +284,20 @@ exports.applyTaintToBuffer = (buffer, string, encoding,
   return buffer;
 };
 
+exports.concatBufferArrayTaint = (list) => {
+  return list.reduce((acc, val) => {
+    if (typeof val === 'object' && val.taint) {
+      val.taint.forEach((range) => {
+        acc.taint.push({'begin': range.begin + acc.len,
+                        'end': range.end + acc.len,
+                        'flow': range.flow
+        });
+      });
+    }
+    acc.len += val.len;
+    return acc;
+  }, {'len': 0, 'taint': []}).taint;
+};
 
 exports.applyArrayTaintToBuffer = (array) => {
   const newTaint = [];

lib/buffer.js

@@ -511,7 +511,7 @@ Buffer.concat = function concat(list, length) {
   }
 
   // TaintV8
-  buffer.taint = TaintBuffer.subtaint(buffer, 0, length);
+  buffer.taint = TaintBuffer.concatBufferArrayTaint(list);
 
   // Note: `length` is always equal to `buffer.length` at this point
   if (pos < length) {