fix: prevent data loss on interrupt by implementing graceful shutdown

Author: Adel Assakaf

cmd/httpx/httpx.go

@@ -73,21 +73,26 @@ func main() {
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, os.Interrupt)
 	go func() {
-		for range c {
-			gologger.Info().Msgf("CTRL+C pressed: Exiting\n")
-			httpxRunner.Close()
-			if options.ShouldSaveResume() {
-				gologger.Info().Msgf("Creating resume file: %s\n", runner.DefaultResumeFile)
-				err := httpxRunner.SaveResumeConfig()
-				if err != nil {
-					gologger.Error().Msgf("Couldn't create resume file: %s\n", err)
-				}
-			}
-			os.Exit(1)
-		}
+		// First Ctrl+C: stop dispatching, let in-flight requests finish
+		<-c
+		gologger.Info().Msgf("CTRL+C pressed: Exiting\n")
+		httpxRunner.Interrupt()
+		// Second Ctrl+C: force exit
+		<-c
+		gologger.Info().Msgf("Forcing exit\n")
+		os.Exit(1)
 	}()
 
 	httpxRunner.RunEnumeration()
+
+	if httpxRunner.IsInterrupted() && options.ShouldSaveResume() {
+		gologger.Info().Msgf("Creating resume file: %s\n", runner.DefaultResumeFile)
+		err := httpxRunner.SaveResumeConfig()
+		if err != nil {
+			gologger.Error().Msgf("Couldn't create resume file: %s\n", err)
+		}
+	}
+
 	httpxRunner.Close()
 }
 

runner/runner.go

@@ -97,12 +97,32 @@ type Runner struct {
 	simHashes          gcache.Cache[uint64, struct{}] // Include simHashes for efficient duplicate detection
 	httpApiEndpoint    *Server
 	authProvider       authprovider.AuthProvider
+	interruptCh        chan struct{}
 }
 
 func (r *Runner) HTTPX() *httpx.HTTPX {
 	return r.hp
 }
 
+// Interrupt signals the runner to stop dispatching new items.
+func (r *Runner) Interrupt() {
+	select {
+	case <-r.interruptCh:
+	default:
+		close(r.interruptCh)
+	}
+}
+
+// IsInterrupted returns true if the runner was interrupted.
+func (r *Runner) IsInterrupted() bool {
+	select {
+	case <-r.interruptCh:
+		return true
+	default:
+		return false
+	}
+}
+
 // picked based on try-fail but it seems to close to one it's used https://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html#c1992
 var hammingDistanceThreshold int = 22
 
@@ -121,7 +141,8 @@ type pHashUrl struct {
 // New creates a new client for running enumeration process.
 func New(options *Options) (*Runner, error) {
 	runner := &Runner{
-		options: options,
+		options:     options,
+		interruptCh: make(chan struct{}),
 	}
 	var err error
 	if options.Wappalyzer != nil {
@@ -1402,6 +1423,12 @@ func (r *Runner) RunEnumeration() {
 	wg, _ := syncutil.New(syncutil.WithSize(r.options.Threads))
 
 	processItem := func(k string) error {
+		select {
+		case <-r.interruptCh:
+			return nil
+		default:
+		}
+
 		if r.options.resumeCfg != nil {
 			r.options.resumeCfg.current = k
 			r.options.resumeCfg.currentIndex++
@@ -1447,6 +1474,9 @@ func (r *Runner) RunEnumeration() {
 
 	if r.options.Stream {
 		for item := range streamChan {
+			if r.IsInterrupted() {
+				break
+			}
 			_ = processItem(item)
 		}
 	} else {

runner/runner_test.go

@@ -15,6 +15,74 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestRunner_resumeAfterInterrupt(t *testing.T) {
+	domains := []string{"a.com", "b.com", "c.com", "d.com", "e.com", "f.com", "g.com", "h.com", "i.com", "j.com"}
+	interruptAfter := 4
+
+	// --- Full scan (reference): process all domains without interrupt ---
+	rFull, err := New(&Options{})
+	require.Nil(t, err, "could not create httpx runner")
+	rFull.options.resumeCfg = &ResumeCfg{}
+	var fullOutput []string
+	for _, d := range domains {
+		rFull.options.resumeCfg.current = d
+		rFull.options.resumeCfg.currentIndex++
+		fullOutput = append(fullOutput, d)
+	}
+
+	// --- Interrupted scan: process items, interrupt after interruptAfter ---
+	rInt, err := New(&Options{})
+	require.Nil(t, err, "could not create httpx runner")
+	rInt.options.resumeCfg = &ResumeCfg{}
+	var interruptedOutput []string
+	for _, d := range domains {
+		// same check as processItem: bail out if interrupted
+		select {
+		case <-rInt.interruptCh:
+			continue
+		default:
+		}
+
+		rInt.options.resumeCfg.current = d
+		rInt.options.resumeCfg.currentIndex++
+		interruptedOutput = append(interruptedOutput, d)
+
+		if len(interruptedOutput) == interruptAfter {
+			rInt.Interrupt()
+		}
+	}
+
+	// simulate SaveResumeConfig: save the index after interrupt
+	savedIndex := rInt.options.resumeCfg.currentIndex
+
+	// the saved index must equal exactly the number of items that were processed
+	require.Equal(t, interruptAfter, savedIndex, "resume index should equal number of completed items")
+	// every domain before the index must be in the interrupted output
+	require.Equal(t, domains[:interruptAfter], interruptedOutput, "interrupted output should contain exactly the first N domains")
+
+	// --- Resumed scan: load saved index, skip already-processed items ---
+	rRes, err := New(&Options{})
+	require.Nil(t, err, "could not create httpx runner")
+	rRes.options.resumeCfg = &ResumeCfg{Index: savedIndex}
+	var resumedOutput []string
+	for _, d := range domains {
+		// same resume-skip logic as processItem
+		rRes.options.resumeCfg.current = d
+		rRes.options.resumeCfg.currentIndex++
+		if rRes.options.resumeCfg.currentIndex <= rRes.options.resumeCfg.Index {
+			continue
+		}
+		resumedOutput = append(resumedOutput, d)
+	}
+
+	// every domain after the index must be in the resumed output
+	require.Equal(t, domains[interruptAfter:], resumedOutput, "resumed output should contain exactly the remaining domains")
+
+	// union of interrupted + resumed must equal the full scan
+	combined := append(interruptedOutput, resumedOutput...)
+	require.Equal(t, fullOutput, combined, "interrupted + resumed should equal full scan")
+}
+
 func TestRunner_domain_targets(t *testing.T) {
 	options := &Options{}
 	r, err := New(options)