Bash should reset OLDPWD upon login, *only*.

[L A Walsh]

Mikulas Patocka wrote:
> The problem occurs even in non-login shells -

>  the chrome browser is 
> started from a bash script, on some distributions firefox is also started 
> from a bash script, mail daemon may start a script specified in user's 
> ".forward" file. And these scripts also poke $OLDPWD and delay startup.
>   
---
   It **seemed** to me that the main complaint was when a new shell was 
started
and OLDPWD was reset.  I really doubt that people are relying on the 
value of
OLDPWD when a browser or deamon is launched. However -- whatever 
launches the
background process (chrome or the daemon) SHOULD take responsibility for 
setting
the environment correctly for the new process (i.e. bash try to correct 
anything
that the launch processes (the ones that launch chrome or the daemon) 
are not
correcting.  Only the launching process will know that OLDPWD won't make 
a difference for new program.  So in those cases, the launcher should be 
fixed --
not bash.

In the case of a user starting a new shell -- OLDPWD has to remain 
whatever the
user set it to before they launched a new shell.  If the OLDPWD points to
/hang, the user should clear out OLDPWD before they launch a new shell.

Only in the case of login -- they user CAN'T set it before they login, but
someone **could** have changed the system /etc/profile script to set OLDPWD
to /hang (i.e. someone is behaving "maliciously").  In the case of 
login, bash is the first point-of-contact for the user and it should be 
started in a "SAFE"
manner.  Suppose you had a file-system that controlled system operations 
(like
"/sys or /proc), where reading from a directory or file might influence 
the state of the system.  I can show an example of this by doing a 
'find' command
through /proc/sys in cygwin on a Win machine (as an admin).  It will cause
my win machine to blue-screen and reboot.

That would be *bad*.

So that's why I say that bash should create a safe-"environment" to log 
in with.
If bash doesn't do it, someone could set OLDPWD to whatever file is read 
by 'find' that causes the reboot and the person could be locked out of 
their system.

Yes it needs console access, so likelihood is small, but consequences 
are "troublesome".  So it should be prevented if possible.


>