Fix Improper Error Handling in Ktor
Improper error handling in Ktor is a goldmine for recon. Default behaviors or lazy try-catch blocks often leak stack traces, internal file paths, and dependency versions, providing attackers with a roadmap of your backend architecture. To harden a Ktor service, you must implement a centralized exception handling strategy that sanitizes all outgoing error responses while maintaining detailed internal logs.
The Vulnerable Pattern
routing {
get("/api/data") {
try {
val result = queryDatabase(call.parameters["id"]!!)
call.respond(result)
} catch (e: Exception) {
// VULNERABILITY: Leaking raw exception details and stack traces to the client
call.respondText(e.stackTraceToString(), status = HttpStatusCode.InternalServerError)
}
}
}The Secure Implementation
The secure implementation utilizes Ktor's 'StatusPages' plugin to intercept exceptions before they reach the default handler. By defining an exception
install(StatusPages) { // Catch specific business/validation exceptions exception{ call, cause -> call.respond(HttpStatusCode.BadRequest, mapOf("status" to "error", "message" to "Invalid request parameters")) } // Generic catch-all to prevent stack trace leakage exception<Throwable> { call, cause -> // Log the actual trace internally for debugging application.log.error("Unhandled exception occurred: ${cause.message}", cause) // Return an opaque, sanitized JSON response call.respond( HttpStatusCode.InternalServerError, mapOf("status" to "error", "message" to "An unexpected error occurred. Please contact support.") ) }
}
Your Ktor API
might be exposed to Improper Error Handling
74% of Ktor apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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