Added experimental banner grabber implemented in Go.
(Caution: This is my first attempt at writing Go.)
This commit is contained in:
Alex Halderman
parent
853524c2ae
commit
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TCP banner grabber implemented in Go (experimental)
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======
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This program will make TCP connections to IP addresses provide on
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stdin, optionally send them a short message, and wait for their
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responses. Each response is printed to stdout, along with the
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responding host's IP address. Status messages appear on stderr.
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USING:
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-----
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go build banner.go
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zmap -p 80 -N 1000 -o - | ./banner -port 80 -concurrent 100 -data http-req > banners.out
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OPTIONS:
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-----
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-concurrent Number of connections that can be going on at once.
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This, combined with timeouts, will decide the maximum
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rate at which banners are grabbed. If this value
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is set higher than 1000, you should use
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`ulimit -SHn 1000000` and `ulimit -SSn 1000000` to
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avoid running out of file descriptors (typically capped
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at 1024). Default: 100.
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-port The port which to connect to hosts on. Default: 80.
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-timeout Connection timeout (seconds). Give up on a host if grabber
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has not completed by this time. Default: 4 seconds.
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-format Format to output banner responses. One of 'hex', 'ascii',
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or 'base64'. Default: ascii.
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-d, --data Optional data file. This data will be sent to each host
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upon successful connection. Occurrences of the
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string '%s' will be replaced with the current
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target host's address.
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/*
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TCP banner grabber, implemented in go
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This program will make TCP connections to IP addresses provide on
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stdin, optionally send them a short message, and wait for their
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responses. Each response is printed to stdout, along with the
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responding host's IP address. Status messages appear on stderr.
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*/
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package main
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/*
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* banner.go Copyright 2013 Regents of the University of Michigan
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not
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* use this file except in compliance with the License. You may obtain a copy
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* of the License at http://www.apache.org/licenses/LICENSE-2.0
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*/
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import (
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"bufio"
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"encoding/base64"
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"encoding/hex"
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"flag"
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"fmt"
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"io"
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"net"
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"os"
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"strings"
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"syscall"
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"time"
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)
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var (
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nConnectFlag = flag.Int("concurrent", 100, "Number of concurrent connections")
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portFlag = flag.String("port", "80", "Destination port")
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formatFlag = flag.String("format", "ascii", "Output format for responses ('ascii', 'hex', or 'base64')")
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timeoutFlag = flag.Int("timeout", 4, "Seconds to wait for each host to respond")
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dataFileFlag = flag.String("data", "", "File containing message to send to responsive hosts ('%s' will be replaced with host IP)")
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)
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var messageData = make([]byte, 0) // data read from file specified with dataFile flag
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// Before running main, parse flags and load message data, if applicable
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func init() {
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flag.Parse()
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if *dataFileFlag != "" {
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fi, err := os.Open(*dataFileFlag)
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if err != nil {
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panic(err)
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}
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buf := make([]byte, 1024)
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n, err := fi.Read(buf)
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messageData = buf[0:n]
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if err != nil && err != io.EOF {
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panic(err)
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}
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fi.Close()
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}
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// Increase file descriptor limit
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rlimit := syscall.Rlimit{Max: uint64(*nConnectFlag + 4), Cur: uint64(*nConnectFlag + 4)}
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if err := syscall.Setrlimit(syscall.RLIMIT_NOFILE, &rlimit); err != nil {
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fmt.Fprintf(os.Stderr, "Error setting rlimit: %s", err)
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}
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}
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type resultStruct struct {
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addr string // address of remote host
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data []byte // data returned from the host, if successful
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err error // error, if any
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}
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// Read addresses from addrChan and grab banners from these hosts.
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// Sends resultStructs to resultChan. Writes to doneChan when complete.
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func grabber(addrChan chan string, resultChan chan resultStruct, doneChan chan int) {
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for addr := range addrChan {
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deadline := time.Now().Add(time.Duration(*timeoutFlag) * time.Second)
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dialer := net.Dialer{Deadline: deadline}
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conn, err := dialer.Dial("tcp", net.JoinHostPort(addr, *portFlag))
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if err != nil {
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resultChan <- resultStruct{addr, nil, err}
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continue
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}
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conn.SetDeadline(deadline)
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if len(messageData) > 0 {
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s := strings.Replace(string(messageData), "%s", addr, -1)
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if _, err := conn.Write([]byte(s)); err != nil {
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conn.Close()
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resultChan <- resultStruct{addr, nil, err}
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continue
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}
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}
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var buf [1024]byte
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n, err := conn.Read(buf[:])
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conn.Close()
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if err != nil && (err != io.EOF || n == 0) {
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resultChan <- resultStruct{addr, nil, err}
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continue
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}
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resultChan <- resultStruct{addr, buf[0:n], nil}
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}
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doneChan <- 1
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}
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// Read resultStructs from resultChan, print output, and maintain
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// status counters. Writes to doneChan when complete.
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func output(resultChan chan resultStruct, doneChan chan int) {
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ok, timeout, error := 0, 0, 0
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for result := range resultChan {
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if result.err == nil {
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switch *formatFlag {
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case "hex":
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fmt.Printf("%s: %s\n", result.addr,
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hex.EncodeToString(result.data))
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case "base64":
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fmt.Printf("%s: %s\n", result.addr,
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base64.StdEncoding.EncodeToString(result.data))
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default:
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fmt.Printf("%s: %s\n", result.addr,
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string(result.data))
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}
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ok++
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} else if nerr, ok := result.err.(net.Error); ok && nerr.Timeout() {
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fmt.Fprintf(os.Stderr, "%s: Timeout\n", result.addr)
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timeout++
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} else {
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fmt.Fprintf(os.Stderr, "%s: Error %s\n", result.addr, result.err)
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error++
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}
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}
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fmt.Fprintf(os.Stderr, "Complete (OK=%d, timeout=%d, error=%d)\n",
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ok, timeout, error)
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doneChan <- 1
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}
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func main() {
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addrChan := make(chan string, *nConnectFlag) // pass addresses to grabbers
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resultChan := make(chan resultStruct, *nConnectFlag) // grabbers send results to output
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doneChan := make(chan int, *nConnectFlag) // let grabbers signal completion
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// Start grabbers and output thread
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go output(resultChan, doneChan)
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for i := 0; i < *nConnectFlag; i++ {
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go grabber(addrChan, resultChan, doneChan)
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}
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// Read addresses from stdin and pass to grabbers
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scanner := bufio.NewScanner(os.Stdin)
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for scanner.Scan() {
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addrChan <- scanner.Text()
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}
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close(addrChan)
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// Wait for completion
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for i := 0; i < *nConnectFlag; i++ {
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<-doneChan
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}
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close(resultChan)
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<-doneChan
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}
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@ -0,0 +1,3 @@
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GET / HTTP/1.1
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Host: %s
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