RemoteShell-Protector.doc

 INTRODUCTION
As a sysop or networking-fan you are lucky if the following never
happened to you:
Some Cosys logs in, enters the shell to search a file and
accidentially starts a GUI-driven program that's not
self-detaching. POOF! Your BBS hangs! If you are at home - fine.
If you aren't, your system will be down for a long time.
Ever tried the same thing with X-Windows? If you start a
GUI-driven program from a local shell - no problem. If you try
it via a telnet link (and don't specify any "-display"
parameters) it just says "Can't open display!" and exits.
This is what RShell-Protector achieves on the Amiga.

 REQUIREMENTS
RShell-Protector makes use of environment variables and therefore
requires OS2.04. 

 INSTALLATION/USAGE
The "rshell-protector" executable is intended to be run as a
background task in the user-startup script. The install-script
included in this archive should perform all necessary changes for
you. The program patches intuition.library and then hangs in the
background, waiting for a Ctrl-C signal. If you ever want to
remove the patches, just use "break <processnumber> c". No fancy
(and illegal) patching routines are used so RShell-Protector will
work fine with SaferPatches.
To actually protect a shell, you have to set the local variable
"RSHELL-PROTECTOR". E.g. in the shell-startup script use:
 set RSHELL-PROTECTOR 1
Programs started from this shell (and its childred which inherit
local variables) will fail to open any window or screen. Using
the "set" and "unset" commands you can switch between "protected"
and "unprotected" while the shell is running.
There might be programs which don't care if Intuition returns
NULL on an OpenScreen()/OpenWindow() call. They will render into
an invalid rastport and crash. The best place for such programs
is your trashcan.

 CNET BBS INSTALLATION
When running some network with remote-logins you will most likely
have some kind of rlogin-startup script, which you don't have for
the BBS shell in CNet. Let's change that:
Load CNet's "bbstext" file into your favourite editor and move to
line #632 where you will find a newshell-command and some options
for the FIFO: handler. Just change the end of the line from
"from S:shell-startup" to something like
"from s:CNetShell-Startup" and save the file.
Create a file called "CNetShell-Startup (or however you called
it) in your s: directory. It sould contain at least:
 execute s:shell-startup
 set RSHELL-PROTECTOR 1
and maybe some other tools/patches that you want to use from the
BBS shell only. Now select "text/menu reload" from CNet's menu
and you're done.

 INSTALLATION ON OTHER BBS-PROGRAMS
Sorry, can't tell you much about this - you have to find out
yourself. Using SnoopDos will help! For DLG the installation
should be similar to CNet, AFAIK the command to call when opening
a shell is also configurable through a textfile.

 TECHNICAL INFO/COMPATIBILITY
RShell-Protector patches the following intuition-functions:
 OpenScreen()
 OpenWindow()
 OpenScreenTagList()
 OpenWindowTagList()
On every call to these functions it checks for the environment
variable called "RSHELL-PROTECTOR". If there is no such variable
the original function is called. Otherwise an error-message is
printed on stdout and zero returned, which means "failure" to the
calling program.
As the ones with good RKM-knowledge will have noticed, this
method is not 100% system friendly. If a TASK (not a PROCESS)
calls one of the above functions, there will be trouble. Only
processes are allowed to call dos.library, tasks aren't. But no
need to ban this patch from your HD forever! We know of only ONE
task that ever calls OpenWindow(), which is the Fastlane's
"z3scsi.device" - and this is only to display errors on very
early system startup.

RShell-Protector has been tested on:
A4000/040, OS3.0, 12MB RAM, Fastlane, Merlin
A4000/030, OS3.0, 22MB RAM, GVP-II, Merlin, MFC-2, CNet/3
A2000, A2630, OS3.1, 7MB RAM, Mastercard, MFC-2, CNet/3
No 68030 or OS3.0+ specific features are used so it should also
run on the 68000 and with OS2.04.

 BUGS
Returncode is always 0, no matter if the patching succeeded or
not. If this annoys you, fix it.

 COPYLEFT
RShell-Protector is copylefted software. Do with it whatever you
like. The sourcecode in asm is included so you can hack around
with it - we used AsmOne V1.50 to write it. The only thing you
must not do is redistribute hacked-up versions with our names in
them - or thou shalt be marked a lamer forever!
If you implement any improvements, please let us know. See below
for addresses.

 AUTHORS
If you can't find us on IRC, send comments, flames etc. to:
Usenet:   hg6202@sun0.mni.fh-giessen.de
AmigaNet: Lunkwill@39:176/208.0
          Skywalker@39:176/208.3

Call these BBSs:
Sweet Dreams - +49-6404-61539 (Line 1, ZyXEL 19k2, 24h)
               +49-6404-65106 (Line 2, ZyXEL 16k8, 22-13h)
Thunder Dome - +49-6408-3249  (Line 1, ZyXEL 19k2, 24h)
               +49-6408-3779  (Line 2, ZyXEL 19k2, 22-13h)


 HISTORY
V37.1, 23-10-94, initial release

 FUTURE
Maybe a WB emulation using RIP-term...? :^)