socks4a-echo.sh

   1 #! /usr/bin/env bash
   2 # source: socks4a-echo.sh
   3 #set -vx
   4
   5 # Copyright Gerhard Rieger and contributors (see file CHANGES)
   6 # Published under the GNU General Public License V.2, see file COPYING
   7
   8 # perform primitive simulation of a socks4a server with echo function via stdio.
   9 # accepts and answers correct SOCKS4a requests, but then just echoes data.
  10 # it is required for test.sh
  11 # for TCP, use this script as:
  12 # socat tcp-l:1080,reuseaddr,crlf system:"socks4a-echo.sh"
  13
  14 # older bash and ksh do not have -n option to read command; we try dd then
  15 #if echo a |read -n 1 null >/dev/null 2>&1; then
  16 #    HAVE_READ_N=1
  17 #else
  18     # and newer bash (4.3) has some other problem with read -n
  19     HAVE_READ_N=
  20 #fi
  21
  22 if type socat >/dev/null 2>&1; then
  23     SOCAT=socat
  24 else
  25     SOCAT=./socat
  26 fi
  27
  28 case `uname` in
  29 HP-UX|OSF1)
  30     CAT="$SOCAT -u stdin stdout"
  31     ;;
  32 *)
  33     CAT=cat
  34     ;;
  35 esac
  36
  37 if   [ $(echo "x\c") = "x" ]; then E=""
  38 elif [ $(echo -e "x\c") = "x" ]; then E="-e"
  39 else
  40     echo "cannot suppress trailing newline on echo" >&2
  41     exit 1
  42 fi
  43 ECHO="echo $E"
  44
  45 if [ $($ECHO "\0101") = "A" ]; then
  46     SOCKSREPLY_FAILED="\0\0133\0\0\0\0\0\0\c"
  47     SOCKSREPLY_OK="\0\0132\0\0\0\0\0\0\c"
  48 else
  49     SOCKSREPLY_FAILED="\0\133\0\0\0\0\0\0\c"
  50     SOCKSREPLY_OK="\0\132\0\0\0\0\0\0\c"
  51 fi
  52
  53 # read and parse SOCKS4a header
  54 if [ "$HAVE_READ_N" ]; then
  55     read -r -n 1 vn     # bash 2.0.3 does not support -n
  56 else
  57     vn=$(dd bs=1 count=1 2>/dev/null)
  58 fi
  59 if [ "$vn" != $($ECHO "\04") ]; then
  60     $ECHO "$SOCKSREPLY_FAILED"
  61     echo "invalid socks version requested" >&2
  62     exit
  63 fi
  64
  65 if [ "$HAVE_READ_N" ]; then
  66     read -r -n 1 cd
  67 else
  68     cd=$(dd bs=1 count=1 2>/dev/null)
  69 fi
  70 if [ "$cd" != $($ECHO "\01") ]; then
  71     $ECHO "$SOCKSREPLY_FAILED"
  72     echo "invalid socks operation requested" >&2
  73     exit
  74 fi
  75
  76 a=$(dd bs=1 count=6 2>/dev/null)
  77 #echo a a a >/dev/tty
  78 #echo "$a" |od -c >/dev/tty
  79 #$ECHO "$a" |od -c >/dev/tty
  80 #echo>/dev/tty
  81 #echo a a a >/dev/tty
  82 if [ "$a" != "$($ECHO "}m\0\0\0\01")" ]; then
  83     sleep 1
  84     $ECHO "$SOCKSREPLY_FAILED"
  85     echo "wrong socks address or port requested" >&2
  86     exit
  87 fi
  88
  89 if [ "$HAVE_READ_N" ]; then
  90     read -r -n 7 u
  91 else
  92     u=$(dd bs=1 count=7 2>/dev/null)
  93 fi
  94 if [ "$u" != "nobody" ]; then
  95     $ECHO "$SOCKSREPLY_FAILED"
  96     echo "wrong socks user requested" >&2
  97     exit
  98 fi
  99
 100 if [ "$HAVE_READ_N" ]; then
 101     read -r -n 10 h
 102 else
 103     h=$(dd bs=1 count=10 2>/dev/null)
 104 fi
 105 if [ "$h" != "localhost" ]; then
 106     $ECHO "$SOCKSREPLY_FAILED"
 107     echo "wrong socks address requested" >&2
 108     exit
 109 fi
 110
 111 # send ok status
 112 $ECHO "$SOCKSREPLY_OK"
 113
 114 # perform echo function
 115 $CAT