socks4echo.sh

   1 #! /usr/bin/env bash
   2 # source: socks4echo.sh
   3
   4 # Copyright Gerhard Rieger and contributors (see file CHANGES)
   5 # Published under the GNU General Public License V.2, see file COPYING
   6
   7 # perform primitive simulation of a socks4 server with echo function via stdio.
   8 # accepts and answers correct SOCKS4 requests, but then just echoes data.
   9 # it is required for test.sh
  10 # for TCP, use this script as:
  11 # socat tcp-l:1080,reuseaddr,crlf system:"socks4echo.sh"
  12
  13 # older bash and ksh do not have -n option to read command; we try dd then
  14 #if echo a |read -n 1 null >/dev/null 2>&1; then
  15 #    HAVE_READ_N=1
  16 #else
  17     # and newer bash (4.3) has some other problem with read -n
  18     HAVE_READ_N=
  19 #fi
  20
  21 if type socat >/dev/null 2>&1; then
  22     SOCAT=socat
  23 else
  24     SOCAT=./socat
  25 fi
  26
  27 case `uname` in
  28 HP-UX|OSF1)
  29     CAT="$SOCAT -u stdin stdout"
  30     ;;
  31 *)
  32     CAT=cat
  33     ;;
  34 esac
  35
  36 if   [ $(echo "x\c") = "x" ]; then E=""
  37 elif [ $(echo -e "x\c") = "x" ]; then E="-e"
  38 else
  39     echo "cannot suppress trailing newline on echo" >&2
  40     exit 1
  41 fi
  42 ECHO="echo $E"
  43
  44 if [ $($ECHO "\0101") = "A" ]; then
  45     SOCKSREPLY_FAILED="\0\0133\0\0\0\0\0\0\c"
  46     SOCKSREPLY_OK="\0\0132\0\0\0\0\0\0\c"
  47 else
  48     SOCKSREPLY_FAILED="\0\133\0\0\0\0\0\0\c"
  49     SOCKSREPLY_OK="\0\132\0\0\0\0\0\0\c"
  50 fi
  51
  52 # read and parse SOCKS4 header
  53 if [ "$HAVE_READ_N" ]; then
  54     read -r -n 1 vn     # bash 2.0.3 does not support -n
  55 else
  56     vn=$(dd bs=1 count=1 2>/dev/null)
  57 fi
  58 if [ "$vn" != $($ECHO "\04") ]; then
  59     $ECHO "$SOCKSREPLY_FAILED"
  60     echo "invalid socks version requested" >&2
  61     exit
  62 fi
  63
  64 if [ "$HAVE_READ_N" ]; then
  65     read -r -n 1 cd
  66 else
  67     cd=$(dd bs=1 count=1 2>/dev/null)
  68 fi
  69 if [ "$cd" != $($ECHO "\01") ]; then
  70     $ECHO "$SOCKSREPLY_FAILED"
  71     echo "invalid socks operation requested" >&2
  72     exit
  73 fi
  74
  75 if [ "$HAVE_READ_N" ]; then
  76     read -r -n 6 a
  77 else
  78     a=$(dd bs=1 count=6 2>/dev/null)
  79 fi
  80 if [ "$a" != "$($ECHO "}m bL6")" ]; then
  81     $ECHO "$SOCKSREPLY_FAILED"
  82     echo "$0: wrong socks address or port requested" >&2
  83     echo "$0: expected $($ECHO "}m bL6"|od -t x1), received $($ECHO "$a"|od -t x1)" >&2
  84     exit
  85 fi
  86
  87 if [ "$HAVE_READ_N" ]; then
  88     read -r -n 7 u
  89 else
  90     u=$(dd bs=1 count=7 2>/dev/null)
  91 fi
  92 if [ "$u" != "nobody" ]; then
  93     $ECHO "$SOCKSREPLY_FAILED"
  94     echo "wrong socks user requested (expected \"nobody\")" >&2
  95     exit
  96 fi
  97
  98 # send ok status
  99 $ECHO "$SOCKSREPLY_OK"
 100
 101 # perform echo function
 102 $CAT