Identification Failures in Gorilla Mux with Cockroachdb

Identification failures occur when an API cannot reliably distinguish one user or tenant from another. In a setup using Gorilla Mux as the router and CockroachDB as the backend, this typically manifests as IDOR or BOLA (Broken Level of Authorization) due to mismatched handling of identifiers between routing layers and SQL queries.

Gorilla Mux provides route variables (e.g., /users/{userID}/profile), but if application code does not consistently enforce that the authenticated subject maps to the requested userID, an attacker can change the path parameter to access another user’s data. CockroachDB, while PostgreSQL-wire compatible, stores identifiers in columns with specific types (e.g., UUID or BIGINT). If the application reads route variables as strings and uses them directly in SQL without type-safe parameterization or ownership checks, the unauthenticated attack surface expands. For example, a handler that does vars["userID"] and interpolates it into a string-based query may inadvertently expose rows because CockroachDB returns results based on SQL equality, not application-level context, and missing tenant or ownership predicates allow cross-user reads.

Another vector is insufficient verification of resource ownership at the database level. Suppose a request arrives with userID=123 and an API key that belongs to userID=456. If the handler issues a query like SELECT * FROM profiles WHERE id = $1 using only the route parameter and lacks a join or filter on the authenticated subject (e.g., via a session-derived tenant ID), the system performs an identification failure. Cockroachdb’s serializable isolation does not prevent this class of logical flaw; it only guarantees consistency, not authorization. Compounded by potential index usage that makes lookup efficient for attacker-supplied IDs, the API returns data without confirming that the requester is allowed to view it, resulting in a BOLA/IDOR finding in the security scan.

Additionally, route definitions that do not enforce strict parameter typing can amplify risk. Mux permits flexible patterns, but if numeric IDs are accepted as strings and later cast, malformed or unexpected inputs may bypass application guards. When such inputs reach Cockroachdb, implicit type conversions might still succeed, returning unintended rows. For instance, passing userID=123abc might be coerced or truncated, causing the query to match a different record. This mismatch between router-level variable extraction and DB-level type handling creates an exploitable gap that middleBrick’s Authentication and BOLA/IDOR checks are designed to surface.

Remediation centers on ensuring that every data access includes the authenticated subject as an invariant filter and that identifiers are handled with type safety. Below are concrete, realistic examples using CockroachDB with Go (using pgx) and Gorilla Mux.

1. Enforce ownership in the handler

Always bind the route variable to a typed parameter and include it in a WHERE clause alongside the authenticated subject. Do not rely on the route alone.

// Example: Gorilla Mux handler with ownership check
package handlers

import (
    "context"
    "net/http"
    "github.com/gorilla/mux"
    "github.com/jackc/pgx/v5/pgxpool"
)

type ProfileHandler struct {
    db  *pgxpool.Pool
    getSubject func(*http.Request) string // returns userID from auth context
}

func (h *ProfileHandler) GetProfile(w http.ResponseWriter, r *http.Request) {
    vars := mux.Vars(r)
    routeUserID := vars["userID"] // e.g., "123"
    subjectID := h.getSubject(r)  // e.g., "456" from JWT/session

    var profile Profile
    // Use parameterized query; include subjectID to enforce ownership
    const q = `SELECT id, display_name FROM profiles WHERE id = $1 AND owner_id = $2`
    err := h.db.QueryRow(r.Context(), q, routeUserID, subjectID).Scan(&profile.ID, &profile.DisplayName)
    if err != nil {
        http.Error(w, "not found", http.StatusNotFound)
        return
    }
    // respond with profile
}

2. Use UUID type-safe handling

Avoid string concatenation; parse route variables into the correct CockroachDB-supported type and use placeholders to prevent injection and type confusion.

import (
    "github.com/google/uuid"
    "github.com/jackc/pgx/v5"
)

func GetDocumentHandler(db *pgxpool.Pool, getSubject func(*http.Request) uuid.UUID) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        vars := mux.Vars(r)
        docID, err := uuid.Parse(vars["docID"])
        if err != nil {
            http.Error(w, "invalid id", http.StatusBadRequest)
            return
        }
        subject := getSubject(r)

        var doc Document
        const q = `SELECT id, content FROM documents WHERE id = $1 AND owner_id = $2`
        err = db.QueryRow(r.Context(), q, docID, subject).Scan(&doc.ID, &doc.Content)
        if err != nil {
            if err == pgx.ErrNoRows {
                http.Error(w, "forbidden or not found", http.StatusNotFound)
                return
            }
            http.Error(w, "server error", http.StatusInternalServerError)
            return
        }
        // return doc
    }
}

3. Apply tenant or scope filters at the route and DB level

If your data is partitioned by tenant, ensure the route variable and the authenticated scope are both used in the query. CockroachDB benefits from explicit equality predicates on indexed columns.

const tenantQuery = `
    SELECT report_id, title 
    FROM reports 
    WHERE tenant_id = $1 AND report_id = $2`

type Report struct{ ID string; Title string }

func ListReports(db *pgxpool.Pool, getTenantID func(*http.Request) string) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        vars := mux.Vars(r)
        reportID := vars["reportID"]
        tenantID := getTenantID(r)

        rows, err := db.Query(r.Context(), tenantQuery, tenantID, reportID)
        if err != nil {
            http.Error(w, "server error", http.StatusInternalServerError)
            return
        }
        defer rows.Close()
        var reports []Report
        for rows.Next() {
            var r Report
            rows.Scan(&r.ID, &r.Title)
            reports = append(reports, r)
        }
        // respond
    }
}

4. Validate and coerce identifiers consistently

Define a small validation layer so route variables conform to expected formats before reaching the database. This prevents malformed inputs from causing unexpected matches or errors in Cockroachdb.

import "regexp"

var userIDRegex = regexp.MustCompile(`^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$`)

func validateUserID(v string) bool {
    return userIDRegex.MatchString(v)
}

// In handler:
if !validateUserID(routeUserID) {
    http.Error(w, "bad request", http.StatusBadRequest)
    return
}