/usr/share/doc/socat/examples/socks4a-echo.sh is in socat 1.7.3.2-2ubuntu2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 | #! /bin/bash
# source: socks4a-echo.sh
#set -vx
# Copyright Gerhard Rieger and contributors (see file CHANGES)
# Published under the GNU General Public License V.2, see file COPYING
# perform primitive simulation of a socks4a server with echo function via stdio.
# accepts and answers correct SOCKS4a requests, but then just echoes data.
# it is required for test.sh
# for TCP, use this script as:
# socat tcp-l:1080,reuseaddr,crlf system:"socks4a-echo.sh"
# older bash and ksh do not have -n option to read command; we try dd then
#if echo a |read -n 1 null >/dev/null 2>&1; then
# HAVE_READ_N=1
#else
# and newer bash (4.3) has some other problem with read -n
HAVE_READ_N=
#fi
if type socat >/dev/null 2>&1; then
SOCAT=socat
else
SOCAT=./socat
fi
case `uname` in
HP-UX|OSF1)
CAT="$SOCAT -u stdin stdout"
;;
*)
CAT=cat
;;
esac
if [ $(echo "x\c") = "x" ]; then E=""
elif [ $(echo -e "x\c") = "x" ]; then E="-e"
else
echo "cannot suppress trailing newline on echo" >&2
exit 1
fi
ECHO="echo $E"
if [ $($ECHO "\0101") = "A" ]; then
SOCKSREPLY_FAILED="\0\0133\0\0\0\0\0\0\c"
SOCKSREPLY_OK="\0\0132\0\0\0\0\0\0\c"
else
SOCKSREPLY_FAILED="\0\133\0\0\0\0\0\0\c"
SOCKSREPLY_OK="\0\132\0\0\0\0\0\0\c"
fi
# read and parse SOCKS4a header
if [ "$HAVE_READ_N" ]; then
read -r -n 1 vn # bash 2.0.3 does not support -n
else
vn=$(dd bs=1 count=1 2>/dev/null)
fi
if [ "$vn" != $($ECHO "\04") ]; then
$ECHO "$SOCKSREPLY_FAILED"
echo "invalid socks version requested" >&2
exit
fi
if [ "$HAVE_READ_N" ]; then
read -r -n 1 cd
else
cd=$(dd bs=1 count=1 2>/dev/null)
fi
if [ "$cd" != $($ECHO "\01") ]; then
$ECHO "$SOCKSREPLY_FAILED"
echo "invalid socks operation requested" >&2
exit
fi
a=$(dd bs=1 count=6 2>/dev/null)
#echo a a a >/dev/tty
#echo "$a" |od -c >/dev/tty
#$ECHO "$a" |od -c >/dev/tty
#echo>/dev/tty
#echo a a a >/dev/tty
if [ "$a" != "$($ECHO "}m\0\0\0\01")" ]; then
sleep 1
$ECHO "$SOCKSREPLY_FAILED"
echo "wrong socks address or port requested" >&2
exit
fi
if [ "$HAVE_READ_N" ]; then
read -r -n 7 u
else
u=$(dd bs=1 count=7 2>/dev/null)
fi
if [ "$u" != "nobody" ]; then
$ECHO "$SOCKSREPLY_FAILED"
echo "wrong socks user requested" >&2
exit
fi
if [ "$HAVE_READ_N" ]; then
read -r -n 10 h
else
h=$(dd bs=1 count=10 2>/dev/null)
fi
if [ "$h" != "localhost" ]; then
$ECHO "$SOCKSREPLY_FAILED"
echo "wrong socks address requested" >&2
exit
fi
# send ok status
$ECHO "$SOCKSREPLY_OK"
# perform echo function
$CAT
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