UnixReview.com
March 2006

sh_screen

 
#!/bin/ksh
#
# sh_screen - launches screen setuid and 
#             then switches it back
#
# path: /usr/local/bin/sh_screen
# this file should be chmod 700, owned by root

/bin/chmod +s /usr/bin/screen      # adjust paths to fit your system

# the message in a bottle
(/bin/sleep 1;/bin/chmod -s /usr/bin/screen) &

#while the message floats, launch screen as the login user

/usr/bin/sudo -u $(/usr/bin/logname) /usr/bin/screen $*

# save the return code
screen_return=$?

# be sure the background job has run
wait

# return screen's return code
return $screen_return

# end sh_screen



#!/bin/ksh
#
# sscreen - wrapper script for sudo'ing sh_screen
# 
# path: /usr/local/bin/sscreen
# this file should be chmod 755, owned by root

/usr/bin/sudo /usr/local/bin/sh_screen $*

# end sscreen



#!/bin/ksh
#
# ss_addviewer - grant a user read-only access to an
#                sscreen session from within that session
#
# path: /usr/local/bin/ss_addviewer
# this file should be chmod 700, owned by root

SSCREEN=/usr/local/bin/sscreen

if [[ "${STY}" = "" ]]
then
    # we're not in an sscreen session
    echo 'This script is only meant to run from' 
    echo 'within an existing sscreen session' 
    exit
fi

read "username?User to add: " 

# make sure we're in multiuser mode
${SSCREEN} -X multiuser on

# screen makes you add a full privileged user, then subtract
# privileges
${SSCREEN} -X acladd ${username}

# take away the ability to type in the session
# and to execute screen commands
${SSCREEN} -X aclchg ${username} -w-x '#?' 

# give them the right to detach (Ctrl-A, d)
${SSCREEN} -X aclchg ${username} +x detach

# end ss_addviewer


#!/bin/ksh
#
# ssallow - sudo wrapper for ss_adduser
#
# path: /usr/local/bin/ssallow
# this file should be chmod 755, owned by root

/usr/bin/sudo /usr/local/bin/ss_addviewer

# end ssallow


#!/bin/ksh
#
# ss_listsessions - list established sscreen sessions
#
# path: /usr/local/bin/ss_listsessions
# this file should be chmod 700, owned by root

/usr/bin/find /tmp/screens -type p \
  | /bin/sed 's/^.*screens\/S-//;s/\/.*\./\//'

# end ss_listsessions


#!/bin/ksh
#
# ssls - sudo wrapper for ss_listsessions
#
# path: /usr/local/bin/ssls
# this file should be chmod 755, owned by root

/usr/bin/sudo /usr/local/bin/ss_listsessions

# end ssls


#!/bin/ksh
#
# shared_screen - safely share screen sessions
#
# path: /usr/local/bin/shared_screen 
# this file should be chmod 755

screen_name=${1:-share_screen}

if ! /usr/local/bin/sscreen -x "${screen_name}" then
   /usr/local/bin/sscreen -S ${screen_name##*/}
fi
# end shared_screen