javascript

node.js

mongodb

mongoose

javascript-injection

How can I prevent JavaScript NoSQL injections into MongoDB?

I am working on a Node.js application and I am passing req.body, which is a json object, into the mongoose model's save function. I thought there were safeguards behind the scenes, but this doesn't appear to be the case.

Solution 1

Sushant's answer is not correct. You need to be aware of NoSQL injection in MongoDB.

Example (taken from here)

User.findOne({
    "name" : req.params.name, 
    "password" : req.params.password
}, callback); 

If req.params.password is { $ne: 1 }, the user will be retrieved without knowing the password ($ne means not equals 1).

MongoDB Driver

You can use mongo-sanitize:

It will strip out any keys that start with '$' in the input, so you can pass it to MongoDB without worrying about malicious users overwriting.

var sanitize = require('mongo-sanitize');

var name = sanitize(req.params.name);
var password = sanitize(req.params.password);

User.findOne({
    "name" : name, 
    "password" : password
}, callback); 

Mongoose Driver

As it follows a schema, if the password is a string field, it will convert the object { $ne: 1 } to string and no damage will be done. In this case, you don't need to sanitize, just remember to set a proper schema.

Solution 2

Although the post is obsolete, I'm answering.

I know three ways.

First: There is a multipurpose content-filter. Also provides MongoDB injection protection by filtering way.

Second: mongo-sanitize, Helper to sanitize mongodb queries against query selector injections.

Third: I'd seen over here this solution which can be applied for MongoDB too. It's really simple to implement. Only use built-in escape() function of JavaScript.

escape() converts the string into ascii code. $ne is converted into %24ne.

var privateKey = escape(req.params.privateKey);

App.findOne({ key: privateKey }, function (err, app) {
  //do something here
}

Solution 3

In order to guard against query selector injections from a data object with unknown structure

Use mongo-sanitize to deeply sanitize via recursion:

const deepSanitize = (value) => {
    if(Array.isArray(value)){
        value.forEach(elm=>deepSanitize(elm))
    }
    if(typeof(value) === 'object' && value !== null){
        Object.values(value).forEach((elm)=>{
            deepSanitize(elm)
        })
    }
    return sanitize(value)
}

For example with sanitize(req.query) nested query selectors will not be removed:

const req = {} 
req.query = { _id : { $ne: 1 } } 

console.log(req.query))               // { _id: { '$ne': 1 } }
console.log(sanitize(req.query))      // { _id: { '$ne': 1 } }

Using deepSanitize(req.query) sanitized objects (including nested) are mutated:

console.log(deepSanitize(req.query))       // { _id: {} }
console.log(req.query)                     // { _id: {} }

Eliminate object mutation with {...req.query}:

console.log(deepSanitize({...req.query}))  // { _id: {} }
console.log(req.query)                     // { _id: { '$ne': 1 } }

Solution 4

Note My answer is incorrect. Please refer to other answers.

--

As a client program assembles a query in MongoDB, it builds a BSON object, not a string. Thus traditional SQL injection attacks are not a problem.

For details follow the documentation

UPDATE

Avoid expression like eval which can execute arbitrary JS. If you are taking input from user and running eval like expressions without cleaning the input you can screw up. As pointed by JoBu1324, operations like where, mapReduce and group permit to execute JS expressions directly.