Bola Idor in Gorilla Mux with Cockroachdb

BOLA (Broken Object Level Authorization) / IDOR occurs when an API exposes internal object identifiers without verifying that the requesting user has permission to access the specific resource. Using Gorilla Mux for routing together with CockroachDB as the backend can inadvertently create this condition when route parameters such as userID or recordID are directly used to construct CockroachDB queries without an ownership or tenant check.

Consider a REST endpoint defined with Gorilla Mux that fetches a user profile by ID:

router.HandleFunc("/api/users/{userID}", getUserProfile).Methods("GET")

If the handler extracts the parameter and passes it straight into a CockroachDB query like the following, the endpoint trusts the client-supplied userID:

func getUserProfile(w http.ResponseWriter, r *http.Request) {
    vars := mux.Vars(r)
    userID := vars["userID"]
    row := db.QueryRow(context.Background(), "SELECT email, name FROM users WHERE id = $1", userID)
    // ... return response
}

An attacker can change the userID in the URL to access another user’s data. Because CockroachDB enforces SQL semantics strictly, a direct string or integer substitution without an access control check returns the row if it exists, leading to unauthorized data exposure. The risk is especially pronounced when the identifier is predictable (e.g., sequential integers or UUIDs without access boundaries) and when the API does not enforce a tenant or subject ownership model. In multi-tenant applications, failing to scope queries by tenant further amplifies the exposure, allowing cross-tenant IDOR across organizations stored in the same CockroachDB cluster.

Another common pattern involves related resources, such as a user’s documents:

router.HandleFunc("/api/users/{userID}/documents/{documentID}", getDocument).Methods("GET")

If the handler queries CockroachDB using both userID and documentID without confirming that the document belongs to the user, an attacker can modify either path segment to traverse relationships and access documents belonging to other users. Cockroachdb’s strong consistency means that once the correct row is located, the data is returned regardless of how the request originated, making proper authorization at the object level essential.

Logging and error messages from CockroachDB can also leak information that aids an attacker in refining guesses, especially when error responses differ between missing rows and forbidden rows. The combination of a predictable routing pattern in Gorilla Mux and a direct SQL query in CockroachDB without an explicit authorization step creates a BOLA/IDOR vulnerability that must be addressed at the handler level rather than the database layer alone.

Remediation centers on ensuring that every data access includes an authorization check that ties the requested object to the requesting user or tenant. This means validating ownership or scope before forming the SQL statement sent to CockroachDB.

1. Enforce user ownership check before querying:

func getUserProfile(w http.ResponseWriter, r *http.Request) {
    vars := mux.Vars(r)
    userID := vars["userID"]
    // Assume getAuthenticatedUserID returns the user ID from a valid session or token
    requesterID := getAuthenticatedUserID(r)
    if requesterID != userID {
        http.Error(w, "forbidden", http.StatusForbidden)
        return
    }
    row := db.QueryRow(context.Background(), "SELECT email, name FROM users WHERE id = $1", userID)
    // ... process row
}

2. For nested resources, validate the relationship explicitly:

func getDocument(w http.ResponseWriter, r *http.Request) {
    vars := mux.Vars(r)
    userID := vars["userID"]
    documentID := vars["documentID"]
    requesterID := getAuthenticatedUserID(r)
    var ownerID string
    err := db.QueryRow(context.Background(), "SELECT user_id FROM documents WHERE id = $1", documentID).Scan(&ownerID)
    if err != nil {
        http.Error(w, "not found", http.StatusNotFound)
        return
    }
    if requesterID != ownerID {
        http.Error(w, "forbidden", http.StatusForbidden)
        return
    }
    // Safe to proceed with document retrieval
    var content string
    db.QueryRow(context.Background(), "SELECT content FROM documents WHERE id = $1", documentID).Scan(&content)
    // ... return content
}

3. Apply tenant scoping if using multi-tenancy:

func listRecords(w http.ResponseWriter, r *http.Request) {
    tenantID := getTenantID(r) // derived from subdomain or auth context
    rows, err := db.Query(context.Background(), "SELECT id, name FROM records WHERE tenant_id = $1", tenantID)
    if err != nil {
        http.Error(w, "server error", http.StatusInternalServerError)
        return
    }
    defer rows.Close()
    // ... encode response
}

4. Use prepared statements with parameterized queries to avoid SQL injection while maintaining clear ownership semantics. Never concatenate path parameters directly into SQL strings.

These patterns ensure that even though Gorilla Mux routes parameters and CockroachDB executes the query, the application layer explicitly enforces who can read or modify each object, effectively mitigating BOLA/IDOR.