Allow replacement of prohibited characters, instead of removing data

README.md

@@ -21,19 +21,33 @@ var app = express();
 
 app.use(bodyParser.urlencoded({extended: true}));
 app.use(bodyParser.json());
+
+// To remove data, use:
 app.use(mongoSanitize());
 
+// Or, to replace prohibited characters with _, use:
+app.use(mongoSanitize({
+  replaceWith: '_'
+}))
+
 ```
 
 ## What?
 
-This module removes any keys in objects that begin with a `$` sign from `req.body`, `req.query` or `req.params`.
+This module searches for any keys in objects that begin with a `$` sign or contain a `.`, from `req.body`, `req.query` or `req.params`. It can then either:
+
+- completely remove these keys and associated data from the object, or
+- replace the prohibited characters with another allowed character.
+
+The behaviour is governed by the passed option, `replaceWith`. Set this option to have the sanitizer replace the prohibited characters with the character passed in.
+
+See the spec file for more examples.
 
 ## Why?
 
-Object keys starting with a `$` are _reserved_ for use by MongoDB as operators. Without this sanitization,  malicious users could send an object containing a `$` operator, which could change the context of a database operation. Most notorious is the `$where` operator, which can execute arbitrary JavaScript on the database.
+Object keys starting with a `$` or containing a `.` are _reserved_ for use by MongoDB as operators. Without this sanitization,  malicious users could send an object containing a `$` operator, or including a `.`, which could change the context of a database operation. Most notorious is the `$where` operator, which can execute arbitrary JavaScript on the database.
 
-The best way to prevent this is to sanitize the received data, and remove any offending keys.
+The best way to prevent this is to sanitize the received data, and remove any offending keys, or replace the characters with a 'safe' one.
 
 ## Credits
 

index.js

@@ -1,29 +1,52 @@
 'use strict';
 
-var sanitize = function(val) {
-  if(Array.isArray(val)) {
-    val.forEach(sanitize);
-
-  } else if(val instanceof Object) {
-    Object.keys(val).forEach(function(key) {
-      if (/^\$|\./.test(key)) {
-        delete val[key];
-      } else {
-        sanitize(val[key]);
-      }
-    });
+var TEST_REGEX = /^\$|\./,
+    REPLACE_REGEX = /^\$|\./g;
+
+var sanitize = function(val, options) {
+  options = options || {};
+
+  var replaceWith = null;
+  if(!(TEST_REGEX.test(options.replaceWith))) {
+    replaceWith = options.replaceWith;
   }
 
-  return val;
+  var act = function(val) {
+    if(Array.isArray(val)) {
+      val.forEach(act);
+
+    } else if(val instanceof Object) {
+      Object.keys(val).forEach(function(key) {
+        var v = val[key];
+        var noRecurse = false;
+
+        if(TEST_REGEX.test(key)) {
+          delete val[key];
+          if(replaceWith) {
+            val[key.replace(REPLACE_REGEX, replaceWith)] = v;
+          } else {
+            noRecurse = true;
+          }
+        }
+
+        if(!noRecurse) {
+          act(v);
+        }
+
+      });
+    }
+
+    return val;
+  };
+
+  return act(val);
 };
 
 var middleware = function(options) {
-  options = options || {};
-
   return function(req, res, next) {
     ['body', 'params', 'query'].forEach(function(k) {
       if(req[k]) {
-        req[k] = sanitize(req[k]);
+        req[k] = sanitize(req[k], options);
       }
     });
     next();