Nosql Injection in Chi with Basic Auth

Nosql Injection occurs when attacker-controlled input is interpreted as part of a NoSQL query rather than as data. In Chi, a common pattern is to bind request parameters directly into a MongoDB or similar query without validation. When endpoints are protected only by HTTP Basic Auth, authentication is handled at the transport layer and does not reduce injection risk; the application still parses user input and uses it to construct queries. This means an authenticated request can still carry malicious payloads that the backend treats as operators or field names.

Consider a Chi route that retrieves a user document by username:

// Chi route with potential Nosql Injection
var client = getMongoClient();
var userCollection = client.GetDatabase("test").GetCollection("users");
var handler = func(w http.ResponseWriter, r *http.Request) {
    username := chi.URLParam(r, "username")
    filter := bson.D{{"username", username}}
    var result bson.M
    err := userCollection.FindOne(r.Context(), filter).Decode(&result)
    // handle response
}
router.Get("/users/{username}", handler)

If the username parameter is user-supplied and not sanitized, an attacker could supply a value such as { "$ne": "" }. The resulting BSON filter becomes {"username": {"$ne": ""}}, which matches all users, potentially bypassing intended access controls. Even with Basic Auth present, the query interprets attacker input as structure rather than data, leading to authentication bypass or information disclosure.

Basic Auth headers are base64-encoded but not encrypted; they are easily decoded and do not prevent tampering of request parameters. The combination of NoSQL query construction from user input and reliance on Basic Auth for authorization creates a scenario where authentication does not mitigate injection. Attackers can probe endpoints using curl or automated tools, sending crafted JSON or form data that manipulates query operators such as $in, $regex, or $where.

middleBrick detects this by analyzing the OpenAPI/Swagger spec (including $ref resolution) and correlating runtime behavior with the unauthenticated attack surface. It flags findings such as missing input validation, improper query construction, and lack of schema enforcement. These findings map to OWASP API Top 10 A03:2023 — Injection, and align with common attack patterns involving NoSQL operators. The scanner does not fix the query, but it provides prioritized findings with severity, reproduction steps, and remediation guidance to help developers address the root cause.

To remediate Nosql Injection in Chi when using Basic Auth, treat all user input as untrusted and avoid direct inclusion in NoSQL queries. Basic Auth should be used for transport-level identification, but it must not substitute for proper query parameter validation and encoding. Use explicit schema validation and parameterized queries to ensure input cannot alter query structure.

Below is a secure Chi route example that combines Basic Auth parsing with strict input validation:

// Secure Chi route with Basic Auth and validated input
var client = getMongoClient();
var userCollection = client.GetDatabase("test").GetCollection("users");

var handler = func(w http.ResponseWriter, r *http.Request) {
    // Parse Basic Auth credentials
    user, pass, ok := r.BasicAuth()
    if !ok || !isValidUser(user, pass) {
        http.Error(w, "Unauthorized", http.StatusUnauthorized)
        return
    }

    // Validate and sanitize username from URL parameter
    username := chi.URLParam(r, "username")
    if !isValidUsername(username) {
        http.Error(w, "Bad Request", http.StatusBadRequest)
        return
    }

    // Use a literal value in the filter, not raw user input
    filter := bson.D{{"username", username}}
    var result bson.M
    err := userCollection.FindOne(r.Context(), filter).Decode(&result)
    if err != nil {
        http.Error(w, "Not Found", http.StatusNotFound)
        return
    }
    // Safe response handling
}

// Simple validation helper
func isValidUsername(s string) bool {
    return regexp.MustCompile(`^[a-zA-Z0-9_]{3,32}$`).MatchString(s)
}

Key practices include:

• Always parse and verify credentials via r.BasicAuth() before processing business logic.
• Validate input against a strict allowlist using regular expressions or dedicated validation libraries.
• Never concatenate or interpolate user input into query structures; use literal values in filters.
• If dynamic queries are required, use well-defined builder APIs that treat input strictly as data, not operators.

middleBrick supports this workflow via its CLI tool (middlebrick scan <url>) and GitHub Action, which can enforce a minimum security score in CI/CD pipelines. Teams on the Pro plan gain continuous monitoring and Slack/Teams alerts when changes introduce new injection risks. These integrations help maintain secure coding practices without relying on Basic Auth alone to prevent injection.