fix(dbref): only upgrade objects with allowed $keys to DBRefs

Author: kmahar

Diff for: lib/bson/parser/deserializer.js

@@ -404,6 +404,7 @@ var deserializeObject = function(buffer, index, options, isArray) {
         (buffer[index++] << 8) |
         (buffer[index++] << 16) |
         (buffer[index++] << 24);
+
       object[name] = new Timestamp(lowBits, highBits);
     } else if (elementType === BSON.BSON_DATA_MIN_KEY) {
       object[name] = new MinKey();
@@ -570,10 +571,23 @@ var deserializeObject = function(buffer, index, options, isArray) {
     throw new Error('corrupt object bson');
   }
 
-  // Check if we have a db ref object
-  // this breaks one of the spec tests. should only become a dbref if it's explicitly
-  // wrapped, like a {dbref: {$ref: ...}}
-  // if (object['$id'] != null) object = new DBRef(object['$ref'], object['$id'], object['$db']);
+  // check if object's $ keys are those of a DBRef
+  var dollarKeys = Object.keys(object).filter(k => k.startsWith('$'));
+  var valid = true;
+  dollarKeys.forEach(k => {
+    if (['$ref', '$id', '$db'].indexOf(k) === -1) valid = false;
+  });
+
+  // if a $key not in "$ref", "$id", "$db", don't make a DBRef
+  if (!valid) return object;
+
+  if (object['$id'] != null && object['$ref'] != null) {
+    let copy = Object.assign({}, object);
+    delete copy.$ref;
+    delete copy.$id;
+    delete copy.$db;
+    return new DBRef(object.$ref, object.$id, object.$db || null, copy);
+  }
 
   return object;
 };

Diff for: test/node/bson_test.js

@@ -1111,8 +1111,8 @@ describe('BSON', function() {
     expect(serialized_data).to.deep.equal(serialized_data2);
 
     var doc2 = b.deserialize(serialized_data);
-    expect('namespace').to.equal(doc2.dbref.$ref);
-    expect(doc2.dbref.$id.toHexString()).to.deep.equal(oid.toHexString());
+    expect(doc).to.deep.equal(doc2);
+    expect(doc2.dbref.oid.toHexString()).to.deep.equal(oid.toHexString());
     done();
   });
 
@@ -1131,8 +1131,8 @@ describe('BSON', function() {
 
     var doc2 = b.deserialize(serialized_data);
     expect('something').to.equal(doc2.name);
-    expect('username').to.equal(doc2.user.$ref);
-    expect(id.toString()).to.equal(doc2.user.$id.toString());
+    expect('username').to.equal(doc2.user.collection);
+    expect(id.toString()).to.equal(doc2.user.oid.toString());
     done();
   });