Nosql Injection in Buffalo
How NoSQL Injection Manifests in Buffalo
NoSQL injection in Buffalo applications occurs when untrusted input influences MongoDB query construction without proper validation. Buffalo's default ORM (pop) targets SQL databases, but many Buffalo applications integrate MongoDB via the official Go driver. The vulnerability typically appears in two patterns:
- Direct query document injection: Using
bson.Morbson.Dbuilt from request parameters without operator restrictions. - JavaScript
$whereinjection: Including user input in$whereclauses that execute arbitrary JavaScript.
Consider this vulnerable Buffalo controller action that searches items by arbitrary criteria:
package controllers
import (
"context"
"go.mongodb.org/mongo-driver/bson"
"github.com/gobuffalo/buffalo"
)
type SearchRequest struct {
Query bson.M `json:"query"`
}
func (c *ItemsController) Search(c buffalo.Context) error {
req := &SearchRequest{}
if err := c.Bind(req); err != nil {
return err
}
// VULNERABLE: req.Query is user-controlled bson.M
cursor, err := database.Collection("items").Find(
context.TODO(),
req.Query,
)
if err != nil {
return err
}
// ... process results
return c.Render(200, r.JSON(Items))
}An attacker can send {"query": {"$gt": ""}} to return all documents, or {"query": {"$where": "this.password.length > 0"}} to enumerate documents by password length. This mirrors CVE-2021-27928 (MongoDB Node.js driver injection) but in Go/Buffalo contexts.
Buffalo-Specific Detection
Detect NoSQL injection in Buffalo by identifying these code patterns:
- Unsafe binding: Request structs containing
bson.M,map[string]interface{}, orinterface{}fields that flow directly into MongoDB query methods (Find,FindOne,UpdateOne, etc.). - Route param misuse: Using
c.Param("id")without validating as a MongoDB ObjectID before query construction. - String concatenation: Building query strings or
$whereclauses via+orfmt.Sprintfwith user input.
Dynamic testing with middleBrick automates detection. Submit your Buffalo API endpoint to middleBrick, which sends payloads like:
| Payload | Purpose |
|---|---|
{"$ne": null} | Test for operator injection returning all documents |
{"$where": "this.username == 'admin'"} | Test for JavaScript execution |
{"email": {"$regex": ".*@.*"}} | Test for regex-based enumeration |
middleBrick analyzes response differences (status codes, response lengths, error messages) to identify vulnerabilities. For Buffalo APIs, it also checks for missing ObjectID validation on c.Param("id") endpoints—common in generated Show and Update actions.
Buffalo-Specific Remediation
Remediate NoSQL injection in Buffalo using these patterns:
- Replace
bson.Mfields with typed structs. Define request structs with concrete fields, not maps:
type SearchRequest struct {
Name string `json:"name"`
MinPrice float64 `json:"min_price"`
MaxPrice float64 `json:"max_price"`
}- Construct queries programmatically. Build
bson.Monly from validated struct fields:
func (c *ItemsController) Search(c buffalo.Context) error {
req := &SearchRequest{}
if err := c.Bind(req); err != nil {
return err
}
filter := bson.M{}
if req.Name != "" {
filter["name"] = req.Name
}
if req.MinPrice > 0 {
filter["price"] = bson.M{"$gte": req.MinPrice}
}
if req.MaxPrice > 0 {
if _, ok := filter["price"].(bson.M); ok {
filter["price"].(bson.M)["$lte"] = req.MaxPrice
} else {
filter["price"] = bson.M{"$lte": req.MaxPrice}
}
}
cursor, err := database.Collection("items").Find(context.TODO(), filter)
// ...
}- Validate ObjectIDs. In generated
Show/Updateactions, add ObjectID validation:
func (c *ItemsController) Show(c buffalo.Context) error {
id := c.Param("id")
if !primitive.IsValidObjectID(id) {
return c.Error(404, errors.New("invalid ID format"))
}
objID, _ := primitive.ObjectIDFromHex(id)
item := &model.Item{}
err := database.Collection("items").FindOne(
context.TODO(),
bson.M{"_id": objID},
).Decode(item)
// ...
}- Avoid
$whereentirely. Replace with structured queries. If regex is needed, escape user input:
import "regexp"
userInput := c.Query("name")
escaped := regexp.QuoteMeta(userInput)
filter := bson.M{"name": bson.RegEx{Pattern: escaped, Options: "i"}}These fixes align with OWASP's NoSQL injection prevention cheat sheet and are compatible with Buffalo's MVC structure. middleBrick's remediation guidance maps these patterns to your specific findings.
Frequently Asked Questions
Can middleBrick detect NoSQL injection in Buffalo APIs that use MongoDB?
{"$gt": ""}), $where JavaScript execution, and regex-based enumeration. It analyzes response anomalies to identify vulnerable endpoints, including Buffalo routes that use c.Param or c.Bind with MongoDB queries.