Bola Idor in Buffalo with Bearer Tokens

Broken Level of Authorization (BOLA), also referred to as Insecure Direct Object References (IDOR), occurs when an API exposes internal object references and lacks sufficient authorization checks between subjects (e.g., users or services) and those objects. In Buffalo, a common Go web framework, this risk is amplified when applications use Bearer Tokens for authentication but do not enforce proper ownership or tenant checks on each request.

Consider a Buffalo application that identifies users via a Bearer Token in the Authorization header and then uses a numeric or UUID identifier from the URL to fetch a resource such as an invoice or profile. If the server simply decodes the token to obtain a user ID and then queries the database for the resource by an ID provided by the client, an attacker can modify that ID to access another user’s data. Because the API relies on the token for authentication but omits explicit authorization that ties the resource to the authenticated subject, the unauthenticated attack surface exposed by a tool like middleBrick can reveal this flaw during its parallel security checks.

For example, an API endpoint GET /api/invoices/:invoice_id may validate the Bearer Token and extract a user identifier, but then fail to verify that the invoice identified by :invoice_id belongs to that user. middleBrick’s BOLA/IDOR checks will probe such endpoints by altering object identifiers while keeping the same token, observing whether authorization is consistently enforced. This is especially relevant in Buffalo applications where developers might assume route-level parameters are safe once a token is validated, inadvertently creating horizontal privilege escalation.

Additionally, Buffalo apps that expose nested resources can unintentionally widen the attack surface. An endpoint like GET /api/users/:user_id/documents/:document_id may correctly authenticate a user with a Bearer Token, but if the handler does not ensure that the specified :user_id matches the authenticated subject, an attacker can enumerate or modify other users’ documents. The framework’s convention-based routing and parameter binding can make this oversight subtle, yet the impact is severe because sensitive records become directly accessible by manipulating identifiers.

Real-world attack patterns mirror these scenarios. For instance, an attacker might issue requests with modified IDs while monitoring responses for differences in data content or error messages, a technique that aligns with the OWASP API Top 10 A01:2023 broken object-level authorization. middleBrick’s scanning approach tests this by running sequential probes that include BOLA/IDOR among its 12 security checks, comparing runtime behavior against the OpenAPI specification if provided. When a spec is available, the tool cross-references defined parameters with runtime findings to highlight mismatches in expected authorization boundaries.

In Buffalo, developers often rely on middleware to parse tokens and set current user values in the context. However, if subsequent handlers do not re-validate resource ownership using the context subject, the authorization boundary is effectively bypassed. This creates a situation where authentication succeeds but authorization fails, a distinction that scanners like middleBrick aim to surface by testing unauthenticated endpoints and observing whether access controls depend solely on token presence rather than on correct scoping of objects.

To mitigate BOLA/IDOR in Buffalo applications using Bearer Tokens, you must enforce strict ownership and tenant checks on every request that accesses a specific resource. This means validating that the authenticated subject (extracted from the token) has the right to access the requested object, rather than trusting client-supplied identifiers alone.

Below are concrete code examples that demonstrate secure patterns. First, a safe handler that decodes the Bearer Token, retrieves the authenticated user ID, and ensures the requested invoice belongs to that user:

// handlers/invoices.go
package handlers

import (
    "net/http"
    "strconv"

    "github.com/gobuffalo/buffalo"
    "github.com/gobuffalo/packr/v2"
    "yourproject/models"
)

func InvoiceShow(c buffalo.Context) error {
    // Assume a middleware sets current user ID into context from Bearer Token
    userID, ok := c.Value("current_user_id").(int)
    if !ok {
        return c.Error(http.StatusUnauthorized, "missing user context")
    }

    invoiceID, err := strconv.Atoi(c.Param("invoice_id"))
    if err != nil {
        return c.Error(http.StatusBadRequest, "invalid invoice id")
    }

    var invoice models.Invoice
    // Enforce ownership by querying with both IDs
    if err := models.DB.Where("id = ? AND user_id = ?", invoiceID, userID).First(&invoice).Error; err != nil {
        return c.Error(http.StatusNotFound, "invoice not found or access denied")
    }

    return c.Render(http.StatusOK, r.JSON(invoice))
}

This pattern ensures that even if an attacker modifies :invoice_id, the database query will return no rows unless the invoice both matches the ID and belongs to the authenticated user. In Buffalo, you can centralize this logic in a shared action or a custom middleware that attaches the user context, but every data-access handler should repeat the ownership check.

For nested resources, extend the check to each level of the hierarchy. For example, when documents are scoped under a user, verify both the user and document IDs:

// handlers/documents.go
package handlers

import (
    "net/http"
    "strconv"

    "github.com/gobuffalo/buffalo"
    "yourproject/models"
)

func DocumentShow(c buffalo.Context) error {
    userID, ok := c.Value("current_user_id").(int)
    if !ok {
        return c.Error(http.StatusUnauthorized, "missing user context")
    }

    userIDParam, err := strconv.Atoi(c.Param("user_id"))
    if err != nil || userID != userIDParam {
        return c.Error(http.StatusForbidden, "user id mismatch")
    }

    documentID, err := strconv.Atoi(c.Param("document_id"))
    if err != nil {
        return c.Error(http.StatusBadRequest, "invalid document id")
    }

    var doc models.Document
    if err := models.DB.Where("id = ? AND user_id = ?", documentID, userID).First(&doc).Error; err != nil {
        return c.Error(http.StatusNotFound, "document not found or access denied")
    }

    return c.Render(http.StatusOK, r.JSON(doc))
}

In addition to code-level fixes, integrate middleBrick’s CLI to regularly scan your Buffalo endpoints from the terminal. You can run middlebrick scan <url> to validate that your remediation effectively closes the BOLA/IDOR vectors. For teams using modern CI/CD, the GitHub Action can add API security checks to your pipeline, failing builds if risk scores drop below your chosen threshold. This helps catch regressions early and ensures that Bearer Token handling continues to enforce strict authorization.