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10
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1 // OK : windows -> osx
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2 // Not OK : osx -> windows
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3 // OK : osx, win <-> yahoo.com
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4 /*
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5 Netcat
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6
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7 -v verbose
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8 -vv very verbose
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9 -w timeout [ -w 2 2seconds ]
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10 -i interval
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11 -s local source address
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12 -z zero-I/O mode ( for portscan )
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13 -u with UDP ( default use TCP )
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14 -n don't resolve name/address
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15 -d stealth mode ( don't read from stdin )
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16 -l listen mode ( once )
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17 -L listen mode ( continuous )
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18
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19 Portscan
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20 $ nc -v -z -w 1 192.168.1.1 1-140
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21 $ nc -u -v -z -w 1 192.168.1.1 1-140
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22
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23 Web-client
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24 $ nc -v www.yahoo.com 80
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25
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26 File transfer
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27 $ nc -l 1234 > file
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28 % nc hoge.com 1234 < file
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29
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30 Backdoor
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31 C:\> nc -L -d -e cmd.exe -p 8080
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32
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33 */
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34 package main
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35
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36 import (
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37 "flag"
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38 "fmt"
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39 "io"
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40 "log"
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41 "net"
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42 "os"
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43 )
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44
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45 func main() {
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46
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47 verbose := flag.Bool( "v", false, "verbose" )
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48 vverbose := flag.Bool( "vv", false, "very verbose" )
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49 udp := flag.Bool( "u", false, "with udp" )
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50 // interval := flag.Int( "i", 0, "interval for lines sent, port scanned" )
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51 // timeout := flag.Int( "w", 7, "timeout for connects and final net reads" )
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52 listen := flag.Bool( "l", false, "listen mode" )
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53 zmode := flag.Bool( "z", false, "zero-I/O mode" )
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54 laddr := flag.String( "s", "", "local source address" )
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55 example := flag.Bool( "e", false, "print examples" )
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56
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57 flag.Parse()
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58
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59 if *example {
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60 printExample()
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61 os.Exit( 0 )
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62 }
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63
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64 if flag.NArg() == 0 {
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65 fmt.Fprintf( os.Stderr, "netcat v0.1 (20170604)\n" )
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66 fmt.Fprintf( os.Stderr, " -h or --help option\n" )
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67 os.Exit( 0 )
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68 }
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69
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70 p := "tcp"
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71 if *udp {
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72 p = "udp"
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73 }
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74
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75 if *listen {
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76
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77 if flag.NArg() != 1 {
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78 flag.PrintDefaults()
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79 os.Exit( 1 )
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80 }
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81
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82 port := flag.Arg( 0 )
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83
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84 addr := getLocalIP()
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85 if *laddr == "" {
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86 addr = *laddr
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87 }
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88
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89 if *verbose || *vverbose {
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90 msg := fmt.Sprintf( "listening... %s:%s[%s]", addr, port, p )
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91 printVerbose( msg, "" )
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92 }
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93
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94 l, err := net.Listen( p, net.JoinHostPort( addr, port ) )
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95 if err != nil {
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96 log.Fatal( err )
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97 }
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98 defer l.Close()
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99
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100 conn, err := l.Accept()
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101 if err != nil {
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102 log.Fatal( err )
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103 }
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104 io.Copy( os.Stdout, conn )
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105 conn.Close()
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106
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107 } else {
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108
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109 if flag.NArg() != 2 {
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110 flag.PrintDefaults()
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111 os.Exit( 1 )
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112 }
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113
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114 addr := flag.Arg( 0 )
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115 port := flag.Arg( 1 )
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116
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117 conn, err := net.Dial( p, net.JoinHostPort( addr, port ) )
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118 if err != nil {
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119 log.Fatal( err )
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120 }
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121 defer conn.Close()
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122 go mustCopy( os.Stdout, conn )
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123 mustCopy( conn, os.Stdin )
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124 }
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125
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126 if *zmode {
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127 /*
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128 address := "" // for me.
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129 port := "1-1024"
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130 server := address + ":" + port
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131 */
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132 }
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133 }
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134
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135 func mustCopy( dst io.Writer, src io.Reader ) {
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136 if _, err := io.Copy( dst, src ); err != nil {
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137 log.Fatal( err )
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138 }
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139 }
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140
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141 func printVerbose( vmsg, vvmsg string ) {
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142 fmt.Fprintln( os.Stderr, vmsg, vvmsg )
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143 }
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144
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145 func printExample() {
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146 fmt.Fprintln( os.Stderr, "\n[Exaples]" )
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147 fmt.Fprintln( os.Stderr, " Portscan" )
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148 fmt.Fprintln( os.Stderr, " $ nc -v -z -w 1 192.168.1.1 1-140" )
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149 fmt.Fprintln( os.Stderr, " $ nc -u -v -z -w 1 192.168.1.1 1-140\n" )
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150 fmt.Fprintln( os.Stderr, " Web-client" )
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151 fmt.Fprintln( os.Stderr, " $ nc -v www.yahoo.com 80" )
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152 fmt.Fprintln( os.Stderr, " GET / HTTP/1.0[Enter]" )
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153 fmt.Fprintln( os.Stderr, " [ENTER]\n" )
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154 fmt.Fprintln( os.Stderr, " File transfer" )
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155 fmt.Fprintln( os.Stderr, " $ nc -l 1234 > file" )
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156 fmt.Fprintln( os.Stderr, " % nc hoge.com 1234 < file\n" )
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157 fmt.Fprintln( os.Stderr, " Backdoor" )
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158 fmt.Fprintln( os.Stderr, " C:\\> nc -L -d -e cmd.exe -p 8080" )
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159 }
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160
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161 func getLocalIP() string {
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162 addrs, err := net.InterfaceAddrs()
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163 if err != nil {
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164 log.Fatal( err )
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165 }
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166 for _, addr := range addrs {
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167 if ipnet, ok := addr.(*net.IPNet); ok && !ipnet.IP.IsLoopback() {
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168 if ipnet.IP.To4() != nil {
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169 return ipnet.IP.String()
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170 }
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171 }
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172 }
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173 return "127.0.0.1"
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174 }
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175
|
