initial

Author: mateusz834

go.mod

@@ -0,0 +1,3 @@
+module github.com/mateusz834/postfix-detect-tls
+
+go 1.15

main.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"os/signal"
+	"strings"
+	"sync"
+	"syscall"
+)
+
+func main() {
+	listen := flag.String("listen", ":10000", "listen")
+	network := flag.String("network", "tcp", "")
+	notlsaction := flag.String("notlsaction", "notls", "")
+	tlsaction := flag.String("tlsaction", "dunno", "")
+	flag.Parse()
+
+	listener, err := net.Listen(*network, *listen)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%v\n", err)
+		os.Exit(1)
+	}
+	wg := sync.WaitGroup{}
+
+	done := make(chan struct{})
+
+	sig := make(chan os.Signal)
+	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		<-sig
+		fmt.Println("Terminating")
+		close(done)
+		listener.Close()
+	}()
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+	out:
+		for {
+			con, err := listener.Accept()
+			if err != nil {
+				select {
+				case <-done:
+					return
+				default:
+					fmt.Fprintf(os.Stderr, "Accept failed: %v\n", err)
+					continue out
+				}
+			}
+
+			wg.Add(1)
+
+			connEnd := make(chan struct{})
+
+			go func() {
+				select {
+				case <-connEnd:
+				case <-done:
+					con.Close()
+					<-connEnd
+				}
+				wg.Done()
+			}()
+			go func() {
+				defer func() {
+					connEnd <- struct{}{}
+				}()
+				scanner := bufio.NewScanner(con)
+				scanner.Split(bufio.ScanLines)
+
+				var tls string
+				for scanner.Scan() {
+					s := scanner.Text()
+					if strings.HasPrefix(s, "encryption_protocol=") {
+						fmt.Sscanf(s, "encryption_protocol=%s", &tls)
+					}
+
+					//empty line
+					if len(s) == 0 {
+						if len(tls) == 0 {
+							io.WriteString(con, fmt.Sprintf("action=%v\n\n", *notlsaction))
+						} else {
+							io.WriteString(con, fmt.Sprintf("action=%v\n\n", *tlsaction))
+						}
+						tls = ""
+					}
+
+				}
+				if err := scanner.Err(); err != nil {
+					select {
+					case <-done:
+					default:
+						fmt.Fprintf(os.Stderr, "%v\n", err)
+					}
+				}
+			}()
+		}
+	}()
+	wg.Wait()
+}