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List:       busybox
Subject:    fakesshd (shell script)
From:       Harald Becker <ralda () gmx ! de>
Date:       2010-09-23 0:00:52
Message-ID: 4C9A98B4.6050505 () gmx ! de
[Download RAW message or body]

Hi!

Putting up a new server, I noticed (again) lots of syslog messages from
sshd about unknown users trying to log in. As I do not like to have the
log scattered by such messages every day over hours, I put my ssh server
on a different port. After thinking a bit about this problem, I put the
attached script together. Using netcat sitting on port 22 to build a
fake ssh server, an ssh tar pit. Trying to log in via ssh on port 22 now
hangs for hours. Happy hacking! :-)

May be anybody is interested about such an script. Any comments welcome.

--
Harald


["fakesshd" (text/plain)]

#!/lib/exec/busybox sh

# Name of pid file
pid="/var/run/${0##*/}.pid"

# Display message and exit
die() {
  echo "${0##*/}: $*" >&2
  exit 1
}

# Display a usage message and exit
usage() {
  echo -e "Usage: ${0##*/} [-p PORT]\n"
  exit 0
}

# Our fake sshd daemon process
sshd() {
  umask 0177
  echo $$ >"$pid" \
    && chown root:nogrp "$pid" \
    && chmod 0604 "$pid" \
    && exec nc -llp "${port:-ssh}" -e cat -
  exit 1
}

# Command option processing
while [ $# -gt 0 ]
  do case "$1" in
    ''			) sshd;;
    \? | -\? | --help	) usage;;
    -p | --port		) port="$2"; shift 2;;
    --			) shift; break;;
    -			) break;;
    -*			) die "Invalid option";;
    *			) break;;
  esac
done

# Check number of remaining arguments
[ $# -gt 1 ] && die "Too many arguments"

# Start daemon process in background
setsid nice -n 19 "$0" "" <>/dev/null >&0 2>&0 &

# That's it ...
exit


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