Re: unshar is unsafe

[Bruce Korb]

On Saturday 30 July 2005 07:51 am, John Cowan wrote:

> If shars really matter,

Once upon a time, long ago, anonymous ftp sites were rare and folks
shared software via email.  In those dark days, it was mighty convenient
to be able to roll up files into a shell archive file that could
readily be unrolled at the other end.  We didn't have to worry constantly
about malicious archives.  Now that we must worry, we have anonymous ftp
and mime email formats.  So, how does one protect current naive users from
malware shar archives?  By telling the naive to use anonymous ftp and mime
email and making it clear to the rest that they are about to execute
a shell script that could contain most anything.  Do you trust the source?
Yes, you could:

> ... a plausible approach would be 
> to write an unshar that is not a mere shell for the shell,
> but actually interprets shar format.

But really, why bother:

> Alternatively, just let the poor thing die.  I think
> I've processed a single shar (other than those snarfed from
> old archives) in the last ten years.

If you-all think it really important to be assured that the unshar
user is informed, we can add a "Do you really, really want to do this?"
prompt to unshar.  :)  I'd rather not bother....

 - Bruce
-- 
'bkorb at veritas' is being retired in favor of the Symantec address.