Bug 714693

+++ This bug was initially created as a clone of Bug #683733 +++

+++ This bug was initially created as a clone of Bug #681600 +++

Description of problem:
There is a requirement for "clearing or overwriting TSF controlled display devices, making the current contents unreadable".

Screen only clears the display up to its dimensions, but not the content above it. By scrolling up with Shift+PgUp anything above those blanked dimensions is still visible. This behaviour does not seem to be desired and this should be fixed. One option/workaround could be to use no-scroll kernel boot argument.

Version-Release number of selected component (if applicable):
screen-4.0.3-15.el6.x86_64 (rhel6.0)
screen-4.0.3-16.el6.x86_64 (rhel6.1)

How reproducible:
always

Steps to Reproduce:
1. Update /etc/profile: 
cat >> /etc/profile << EOT
####
SCREENEXEC="screen"
export SCREENDIR=$HOME/.screen
if [ -w $(tty) ] ; then
        trap "exec $SCREENEXEC" 1 2 3 15
        echo -n 'Starting session in 2 seconds'
        sleep 2
        exec $SCREENEXEC
fi
EOT
2. Log into the system at runlevel 3 as any correct user
3. Work with some super secret information, e.g.:
for i in `seq 1 100` ; do cat /etc/profile ; done
4. Lock the screen session with "Ctrl+a x"
5. "scroll up" using "Shift+PgUp"
  
Actual results:
Everything that was above dimensions of cleared display is still visible.

Expected results:
When screen session is locked no other content than password prompt is visible, to meet requirement for "clearing or overwriting TSF controlled display devices, making the current contents unreadable".

Additional info:
This is not a regression against RHEL 6.0, David is checking RHEL 5.6 now ...

[...]
--- Additional comment from ppisar on 2011-06-10 13:08:43 GMT ---

FYI, F16 delivers kernel supporting "\E[3;J" sequence to clear scroll-back buffer.
-----

Based on discussion with Steve Grubb, I propose this feature for RHEL-6.2 as an
alternative to disabled scroll-back buffer.