Nosql Injection in Echo Go with Api Keys

NoSQL injection is a class of injection that targets databases such as MongoDB, CouchDB, or DynamoDB by manipulating query structures through untrusted input. When an Echo Go service uses API keys for identification but does not properly validate or separate the key from data access logic, the combination can expose endpoints to injection. For example, if an API key is accepted as a user-controlled header and directly concatenated into a NoSQL query, an attacker may inject operators that change query semantics.

Consider an Echo Go endpoint that retrieves user data based on an API key passed via header. If the handler decodes the key and uses it to build a MongoDB selector without validation, the key value may contain characters or structures that alter the query. A crafted key like {"$ne": "valid"} could cause the query to match unexpected documents, bypassing intended isolation between tenants. This occurs because the application treats the API key as trusted input rather than a controlled credential, allowing injection to affect query logic.

Another scenario arises when the API key is stored as a field in a document and used in dynamic queries without escaping. If the key is embedded into a JSON-based query using string concatenation, special characters can break the structure and introduce conditions that expose other users’ data. This is especially risky when the same key is used for both authentication and query construction, conflating identity with data selection. Attack patterns such as $where injection or field manipulation may lead to data exposure or unauthorized enumeration, which NoSQL-specific checks in middleBrick can detect through runtime analysis of query behavior.

Echo Go applications that rely on API keys for routing or tenant isolation must ensure the key is never interpreted as part of the query language. MiddleBrick’s LLM/AI Security and Property Authorization checks help identify whether API key values reach data access layers and whether they are properly constrained. By correlating spec definitions with runtime findings, middleBrick highlights scenarios where an API key influences NoSQL query construction, providing prioritized findings and remediation guidance to prevent injection and over-fetching.

Remediation focuses on strict separation between authentication and query building, canonicalization of the API key, and using parameterized or structured queries that do not concatenate raw key values. API keys should be treated as opaque identifiers, validated against a trusted source, and mapped to internal tenant or user identifiers before any database interaction.

Example of vulnerable code that directly uses an API key in a MongoDB selector:

c := eqlib.NewEcho()
c.GET("/data/:id", func(c echo.Context) error {
    apiKey := c.Request().Header.Get("X-API-Key")
    // Unsafe: directly using apiKey in a NoSQL query
    query := bson.D{{"apiKey", apiKey}, {"deleted", false}}
    var result Document
    if err := collection.FindOne(c.Request().Context(), query).Decode(&result); err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError)
    }
    return c.JSON(http.StatusOK, result)
})

The above allows injection if apiKey contains structured content. A safer approach treats the key as an authentication token, validates it, and uses a mapped identifier for queries:

c := echo.New()
c.GET("/data/:id", func(c echo.Context) error {
    apiKey := c.Request().Header.Get("X-API-Key")
    // Validate format to mitigate injection surface
    if !isValidKeyFormat(apiKey) {
        return echo.NewHTTPError(http.StatusBadRequest, "invalid key")
    }
    tenantID, err := resolveTenant(apiKey) // maps key to internal ID securely
    if err != nil || tenantID == "" {
        return echo.NewHTTPError(http.StatusUnauthorized)
    }
    // Use parameterized or structured queries, not string-built keys
    filter := bson.M{"tenant_id": tenantID, "active": true}
    var doc Document
    if err := collection.FindOne(c.Request().Context(), filter).Decode(&doc); err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError)
    }
    return c.JSON(http.StatusOK, doc)
})

func isValidKeyFormat(k string) bool {
    // Example: enforce hex or UUID-like patterns
    matched, _ := regexp.MatchString(`^[A-Fa-f0-9-]+$`, k)
    return matched
}

func resolveTenant(key string) (string, error) {
    // Lookup key in a secure store, return mapped tenant identifier
    // This is a placeholder for secure lookup logic
    if key == "trusted-key-123" {
        return "tenant-abc", nil
    }
    return "", errors.New("not found")
}

Additional hardening steps include rate limiting per key, logging suspicious key patterns, and ensuring that the API key never reaches downstream services as a query parameter. middleBrick’s Authentication and BOLA/IDOR checks validate that keys are scoped correctly and that access controls remain intact across endpoints. With the Pro plan, continuous monitoring can alert on repeated injection-like patterns in key usage, helping teams detect emerging attack vectors before exploitation.