Zip Slip in Chi with Cockroachdb

Zip Slip is a path traversal vulnerability that occurs when an application constructs file paths using user-supplied input without proper validation. In a Chi-based Go service that interacts with CockroachDB, this typically arises when request parameters or headers are used to build filesystem paths for backups, exports, or log storage. Because CockroachDB operations often rely on filesystem-level interactions—such as reading certificate files, storing auxiliary data, or logging—improper path handling can expose the database or application to traversal attacks.

Consider a handler that uses a tenant ID from the URL to locate a CockroachDB backup directory:

func backupHandler(baseBackupDir string) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        tenantID := chi.URLParam(r, "tenant")
        targetPath := filepath.Join(baseBackupDir, tenantID)
        os.MkdirAll(targetPath, 0755)
        // Trigger a CockroachDB backup to targetPath
    }
}

If tenantID contains sequences like ../../etc/cockroach-data, filepath.Join may produce a path outside the intended backup directory. While Go’s filepath.Join cleans the path, it does not prevent all traversal patterns when absolute paths are embedded in segments. An attacker could potentially read or overwrite sensitive CockroachDB files such as certificates or configuration, especially if the application runs with database privileges.

The risk is compounded when the application uses unchecked input to form CockroachDB connection arguments or log paths. For example, a dynamic log directory derived from user input could allow an attacker to write arbitrary files on the host filesystem, potentially interfering with CockroachDB’s file-based operations. Because middleBrick scans unauthenticated attack surfaces and tests inputs across security checks including Input Validation and Property Authorization, such misconfigurations are detectable through controlled probe requests that simulate traversal attempts without requiring credentials.

Even when CockroachDB is not directly compromised, Zip Slip can undermine integrity controls by manipulating auxiliary storage used alongside the database. This aligns with broader OWASP API Top 10 risks around broken object level authorization, where traversal vectors bypass intended access boundaries. middleBrick’s cross-reference between OpenAPI spec definitions and runtime findings helps highlight mismatches between documented paths and actual behavior in Chi routes.

Remediation centers on strict input validation, canonical path resolution, and isolating filesystem operations from database logic. The following Chi handler demonstrates a secure approach when working with Cockroachdb-related paths:

func safeBackupHandler(baseBackupDir string) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        tenantID := chi.URLParam(r, "tenant")
        if !isValidTenantID(tenantID) {
            http.Error(w, "invalid tenant identifier", http.StatusBadRequest)
            return
        }
        // Use a clean base and resolve to absolute canonical path
        base, err := filepath.Abs(baseBackupDir)
        if err != nil {
            http.Error(w, "server configuration error", http.StatusInternalServerError)
            return
        }
        targetDir := filepath.Join(base, tenantID)
        // Ensure the resolved path remains within base
        if !strings.HasPrefix(targetDir, filepath.Clean(base)+string(os.PathSeparator)) {
            http.Error(w, "path traversal attempt detected", http.StatusBadRequest)
            return
        }
        os.MkdirAll(targetDir, 0750)
        // Proceed with CockroachDB backup commands using tenant-specific secure credentials
    }
}

func isValidTenantID(id string) bool {
    // Allow only alphanumeric and limited safe characters
    matched, _ := regexp.MatchString(`^[a-zA-Z0-9_-]{1,64}$`, id)
    return matched
}

In this pattern, isValidTenantID enforces a strict allowlist, preventing traversal sequences and shell metacharacters. The prefix check after resolution guarantees that targetDir cannot escape baseBackupDir, even if future Go updates change filepath.Join behavior. This is particularly important for Cockroachdb operations where supplementary files may reside near data directories.

Additionally, avoid using user input directly in CockroachDB command arguments that influence file locations. Prefer environment variables or configuration maps for paths, and validate any dynamic strings used in logging or export routines. middleBrick’s continuous monitoring under the Pro plan can alert you when new endpoints or parameters introduce traversal risks, while the GitHub Action integration can block deployments that fail path validation checks.

When scanning Chi services with middleBrick, ensure that OpenAPI specs accurately reflect route parameters and that path templates are constrained. The scanner’s cross-reference between spec definitions and runtime findings helps surface inconsistencies that could otherwise lead to insecure path handling around Cockroachdb integrations.