From 6ab1613157a6a5d3eabf9d2fe2adf4699d29a5ba Mon Sep 17 00:00:00 2001
From: Marin Ivanov <dev@metala.org>
Date: Sun, 24 Mar 2019 21:45:18 +0200
Subject: Make TCP connection tarpit

This first version of the command has support for SSH protocol tarpit.
---
 go.mod    |  5 +++++
 go.sum    |  2 ++
 handle.go | 31 +++++++++++++++++++++++++++++++
 main.go   | 45 +++++++++++++++++++++++++++++++++++++++++++++
 ssh.go    | 33 +++++++++++++++++++++++++++++++++
 5 files changed, 116 insertions(+)
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 handle.go
 create mode 100644 main.go
 create mode 100644 ssh.go

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..124f5c7
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module metala.org/pkg/tarpit
+
+go 1.12
+
+require github.com/spf13/pflag v1.0.3
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..edd0bcf
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
+github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
diff --git a/handle.go b/handle.go
new file mode 100644
index 0000000..622b68e
--- /dev/null
+++ b/handle.go
@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"time"
+)
+
+type protoHandler func(net.Conn)
+
+func protocolHandler(proto string) (protoHandler, error) {
+	switch proto {
+	case "ssh":
+		return sshHandler, nil
+	default:
+		return nil, fmt.Errorf("unknown protocol '%s'", proto)
+	}
+}
+
+func logConn(conn net.Conn, msg string) {
+	now := time.Now().UTC()
+	fmt.Printf("%s, %s, %s\n", now.String(), conn.RemoteAddr().String(), msg)
+}
+
+func connHandler(handler protoHandler, conn net.Conn) {
+	defer conn.Close()
+
+	logConn(conn, "handling")
+	handler(conn)
+	logConn(conn, "closing")
+}
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..8de0a5c
--- /dev/null
+++ b/main.go
@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"net"
+	"os"
+	"time"
+
+	flag "github.com/spf13/pflag"
+)
+
+func main() {
+	var protocol string
+	var bindAddr string
+	var port int
+
+	flag.StringVarP(&protocol, "proto", "P", "ssh", "protocol to trap")
+	flag.StringVarP(&bindAddr, "bind-address", "b", "", "address to bind the socket to")
+	flag.IntVarP(&port, "port", "p", 22, "TCP port")
+	flag.Parse()
+
+	handler, err := protocolHandler(protocol)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Error: protocol handler;", err.Error())
+		os.Exit(1)
+	}
+
+	rand.Seed(time.Now().UnixNano())
+	bind := fmt.Sprintf("%s:%d", bindAddr, port)
+	ln, err := net.Listen("tcp", bind)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Error: server listen;", err.Error())
+		os.Exit(1)
+	}
+	fmt.Fprintf(os.Stderr, "** Server listening on %s\n", bind)
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			// handle error
+			continue
+		}
+		go connHandler(handler, conn)
+	}
+}
diff --git a/ssh.go b/ssh.go
new file mode 100644
index 0000000..3d43a6c
--- /dev/null
+++ b/ssh.go
@@ -0,0 +1,33 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math/rand"
+	"net"
+	"time"
+)
+
+type empty struct{}
+
+func sshHandler(conn net.Conn) {
+	eof := make(chan empty)
+	go func() {
+		io.Copy(ioutil.Discard, conn)
+		eof <- empty{}
+	}()
+
+	tick := time.Tick(10 * time.Second)
+	for {
+		select {
+		case <-eof:
+			return
+		case <-tick:
+			_, err := fmt.Fprintf(conn, "%x\r\n", rand.Uint32())
+			if err != nil {
+				return
+			}
+		}
+	}
+}
-- 
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