Bola Idor in Fiber (Go)

Broken Object Level Authorization (BOLA) occurs when an API fails to enforce proper ownership or authorization checks between a client-supplied identifier and the data the client is attempting to access. In a Fiber application written in Go, this commonly arises when route parameters that reference a resource (e.g., a user ID, record ID, or tenant ID) are used directly to fetch or modify data without validating that the authenticated subject has permission to operate on that specific object.

Consider a typical Fiber endpoint that retrieves a user profile by ID:

// Example: Insecure BOLA in Fiber (Go)
app.Get("/users/:id", func(c *fiber.Ctx) error {
    userID := c.Params("id")
    var user User
    // Direct lookup using user-supplied ID without ownership/authorization check
    if err := db.Where("id = ?", userID).First(&user).Error; err != nil {
        return c.Status(fiber.StatusNotFound).JSON(fiber.Map{"error": "user not found"})
    }
    return c.JSON(user)
})

In this pattern, an attacker can change the :id path parameter to access another user’s data. Because the code trusts the client-supplied identifier and does not compare it to the requesting user’s identity, this is a classic BOLA. The vulnerability is not in Fiber or Go themselves, but in the application logic that skips authorization checks. Similar issues can affect endpoints that reference other sensitive resources such as documents, payments, or administrative records.

When using OpenAPI specifications, BOLA risks can be harder to detect if the spec describes the endpoint as accepting an ID but does not explicitly document the authorization requirement linking that ID to the requester. middleBrick’s OpenAPI/Swagger analysis resolves $ref definitions and cross-references spec definitions with runtime findings; this helps highlight endpoints where an ID parameter is present but where authorization checks may be missing in the implementation.

BOLA is often part of the OWASP API Security Top 10 (e.g., under Broken Object Level Authorization) and can map to compliance frameworks such as PCI-DSS and SOC2. Because BOLA exploits are straightforward ID manipulation, they are common and can lead to unauthorized data access or tampering if left unchecked.

To fix BOLA in Fiber (Go), ensure that every access to a user-specific or tenant-specific resource validates that the resource belongs to the requesting subject. This typically involves decoding the identity of the requester (from session, JWT claims, or API key) and comparing it to the resource identifier before performing any database operation.

Here is a secure version of the earlier example, using JWT claims to ensure the requested user ID matches the authenticated user:

// Secure: BOLA protection in Fiber (Go)
app.Get("/users/:id", func(c *fiber.Ctx) error {
    // Assume JWT middleware has already set user claims in context
    claims := c.Locals("claims").(jwt.MapClaims)
    requesterID := claims["sub"] // subject: user identifier
    requestedID := c.Params("id")

    // Enforce BOLA: requester can only access their own resource
    if requesterID != requestedID {
        return c.Status(fiber.StatusForbidden).JSON(fiber.Map{"error": "access denied"})
    }

    var user User
    if err := db.Where("id = ?", requestedID).First(&user).Error; err != nil {
        return c.Status(fiber.StatusNotFound).JSON(fiber.Map{"error": "user not found"})
    }
    return c.JSON(user)
})

For tenant-based scenarios (e.g., multi-tenant SaaS), compare the resource’s tenant ID with the requester’s tenant ID instead of user ID:

// Secure: BOLA protection for tenant-scoped resources
app.Get("/documents/:docID", func(c *fiber.Ctx) error {
    claims := c.Locals("claims").(jwt.MapClaims)
    requesterTenant := claims["tenant_id"]
    docID := c.Params("docID")

    var doc Document
    // Fetch document with tenant scope
    if err := db.Where("id = ? AND tenant_id = ?", docID, requesterTenant).First(&doc).Error; err != nil {
        return c.Status(fiber.StatusNotFound).JSON(fiber.Map{"error": "document not found or access denied"})
    }
    return c.JSON(doc)
})

Additional Go-specific practices that reduce BOLA risk:

• Use parameterized queries (as shown) to avoid SQL injection in addition to authorization bugs.
• Validate ID formats (e.g., UUID regex) before using them in queries to prevent malformed ID attacks or IDOR via ambiguous inputs.
• Centralize authorization logic where possible (e.g., helper functions or middleware) to avoid repeating checks across many endpoints.
• Leverage middleware to attach identity to context once, then reuse that identity across handlers to keep authorization consistent.

middleBrick’s CLI (middlebrick scan <url>) and GitHub Action can help detect missing authorization patterns by correlating endpoint definitions with observed behavior; the MCP Server allows you to run scans from your IDE while developing Go services in Fiber.