This file is indexed.

/usr/bin/autossh is in autossh 1.4c-1.

This file is owned by root:root, with mode 0o755.

The actual contents of the file can be viewed below.

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#!/bin/sh
# little wrapper to choose a random port for autossh, falling back to $fallback_port

fallback_port="21021"
tcpstat="/proc/net/tcp" 

# take an hex port and check whether it is in use (i.e. locally bound) in
# $tcpstat
# unix command semantics: if in use return 0 else return 1
port_in_use() {
	if egrep -q "^[0-9 ]+: [0-9A-F]{8}:$1" $tcpstat ; then
		return 0
	else
		return 1
	fi
}
	
echo "$@" | egrep -q -- '-f?M ?[0-9]+' # backward compatibility, skip guess if -M is passed

if [ $? -gt 0 ] && [ -z "$AUTOSSH_PORT" ]; then 
	portguess=""
	if [ -r "/dev/urandom" ] && [ -r "$tcpstat" ]; then
		for t in $(seq 1 42); do
			# get a random hex
			randport=$( od -x -N2 -An /dev/urandom | tr -d ' ' )
			
			# increase it a little "bit"
			randport=$( /usr/bin/printf "%04x" $(( 0x$randport | 0x8000 )) )
			randport_1=$( /usr/bin/printf "%04x" $(( 0x$randport + 1 )) )

			# check if port is in use, possibile race condition between here
			# and the exec 
			if ! port_in_use $randport && ! port_in_use $randport_1; then
				portguess=$(( 0x$randport ))
				break	
			fi
		done
	fi

	if [ -z "$portguess" ]; then
		fallback=$( /usr/bin/printf "%04x" $fallback_port )
		fallback_1=$( /usr/bin/printf "%04x" $(( 0x$fallback + 1 )) )
		if ! port_in_use $fallback && ! port_in_use $fallback_1; then
			portguess=$fallback_port
		else
			echo "unable to find a suitable tunnel port"
			exit 1
		fi
	fi

	export AUTOSSH_PORT="$portguess"
fi

exec /usr/lib/autossh/autossh "$@"