Bola Idor in Buffalo with Api Keys

BOLA (Broken Level Access Control), commonly referred to as IDOR, occurs when an API exposes sensitive resources through predictable or user-supplied identifiers without enforcing proper authorization. In Buffalo, a Go web framework often used to build RESTful services, this risk is heightened when API keys are used for authentication but not complemented by robust access controls. An API key may identify the calling client, but if the endpoint uses an object-level identifier (e.g., a numeric record ID) that is not validated against the authenticated client’s scope, attackers can modify that identifier to access or manipulate other users’ data.

Consider a Buffalo application that manages user profiles and exposes an endpoint like /v1/users/{userID}. The service authenticates requests using an API key passed in a header (X-API-Key), but then directly uses the userID parameter to query the database. If the API key belongs to Alice but the userID is changed to Bob’s ID, the API may return Bob’s private information because the server never confirms that Alice is allowed to view that record. This is a classic IDOR flaw, and the presence of API keys alone does not prevent it—authentication and authorization are conflated but not properly coupled.

In Buffalo, developers might rely on middleware that sets the current user or organization based on the API key, but if subsequent authorization checks are omitted or incorrectly scoped, the vulnerability persists. For instance, a handler might fetch a company record by ID without verifying that the company is associated with the authenticated API key’s owner. Attackers can automate enumeration by iterating over IDs and observing differences in responses or timing, leading to mass data exposure. The risk is particularly acute in Buffalo applications that expose nested resources (e.g., /v1/organizations/{orgID}/projects/{projectID}) where both organization and project IDs must be validated against the API key’s permissions.

Real-world parallels include findings in which IDOR allowed viewing of other patients’ records in healthcare APIs, or modification of other users’ configuration settings in SaaS platforms. Because Buffalo encourages rapid development with convention-over-configuration, it is easy to omit explicit ownership checks. API keys help identify the client but do not encode relationships such as "belongs-to" or "has-access-to," making it essential to explicitly enforce these rules in each handler. Without such enforcement, an API key becomes a weak gatekeeper that identifies but does not protect.

Remediation centers on ensuring that every resource access is validated against the identity or affiliations encoded by the API key, not just the presence of the key. In Buffalo, this typically means extending the authentication middleware to resolve ownership or membership and then enforcing those constraints in each relevant handler.

Example: API key authentication with ownership validation

Assume API keys are stored in a keys table and linked to an owner (user or organization). The following snippets illustrate a secure pattern.

// middleware/api_key_auth.go
package middleware

import (
    "net/http"
    "github.com/gobuffalo/buffalo"
    "github.com/gobuffalo/pop/v6"
)

type APIKeyContextKey string

const CurrentAPIKeyOwnerID = APIKeyContextKey("current_api_key_owner_id")

func APIKeyAuth(tx *pop.Connection) buffalo.MiddlewareFunc {
    return func(next buffalo.Handler) buffalo.Handler {
        return func(c buffalo.Context) error {
            key := c.Request().Header.Get("X-API-Key")
            if key == "" {
                return c.Render(http.StatusUnauthorized, r.JSON(map[string]string{"error": "missing api key"}))
            }

            var apiKey struct {
                ID      int
                OwnerID int `json:"owner_id"`
                Scope   string
            }
            // pseudo query: SELECT id, owner_id, scope FROM api_keys WHERE key = $1 AND active = true
            if err := tx.Where("key = ?", key).Where("active = ?", true).First(&apiKey); err != nil {
                return c.Render(http.StatusUnauthorized, r.JSON(map[string]string{"error": "invalid api key"}))
            }

            // Attach owner context for later authorization checks
            c.Set(CurrentAPIKeyOwnerID, apiKey.OwnerID)
            return next(c)
        }
    }
}

With the owner ID in context, handlers can enforce ownership explicitly. Below is a secure user profile handler in Buffalo that ensures the requested user ID matches the authenticated API key’s owner.

// handlers/user_handler.go
package handlers

import (
    "net/http"
    "strconv"
    "github.com/gobuffalo/buffalo"
)

func ShowUser(c buffalo.Context) error {
    ownerID, ok := c.Get(middleware.CurrentAPIKeyOwnerID)
    if !ok {
        return c.Render(http.StatusInternalServerError, r.JSON(map[string]string{"error": "misconfigured middleware"}))
    }

    userID, err := strconv.Atoi(c.Param("userID"))
    if err != nil {
        return c.Render(http.StatusBadRequest, r.JSON(map[string]string{"error": "invalid user id"}))
    }

    var user struct {
        ID       int
        OwnerID  int
        Username string
    }
    // Enforce ownership: user must belong to the authenticated API key owner
    if err := tx.Where("id = ? AND owner_id = ?", userID, ownerID).First(&user); err != nil {
        return c.Render(http.StatusNotFound, r.JSON(map[string]string{"error": "not found"}))
    }

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

For nested resources, such as organizations and projects, extend the validation to include hierarchical checks. For example, ensure the project’s organization matches the API key’s organization scope.

// handlers/project_handler.go
package handlers

import (
    "net/http"
    "strconv"
    "github.com/gobuffalo/buffalo"
)

func ShowProject(c buffalo.Context) error {
    ownerID, _ := c.Get(middleware.CurrentAPIKeyOwnerID)
    orgID, _ := strconv.Atoi(c.Param("orgID"))
    projectID, _ := strconv.Atoi(c.Param("projectID"))

    var project struct {
        ID          int
        OrganizationID int
        Name        string
    }
    // Ensure the project belongs to the organization owned by the API key holder
    if err := tx.Where("id = ? AND organization_id = ?", projectID, orgID).First(&project); err != nil {
        return c.Render(http.StatusNotFound, r.JSON(map[string]string{"error": "not found"}))
    }

    var org struct {
        ID      int
        OwnerID int
    }
    if err := tx.Where("id = ? AND owner_id = ?", orgID, ownerID).First(&org); err != nil {
        return c.Render(http.StatusForbidden, r.JSON(map[string]string{"error": "access denied"}))
    }

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

These examples demonstrate that API keys in Buffalo must be paired with explicit ownership checks at the data-access layer. Relying solely on key validation leaves endpoints vulnerable to IDOR. By resolving the owner from the key and validating it against resource ownership (or through policy checks for more complex scopes), you mitigate BOLA/IDOR risks effectively.