Re: Terminal Emulator Security Issues

From: Michael Jennings (mejat_private)
Date: Sun Mar 02 2003 - 13:37:12 PST

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    > > Would stripping escape sequences from the window title work? Do you
    > > know of any applications that actually use this feature?
    > 
    > ...snip...
    >
    > (Incidentally, I was unable to embed any such sequences in the
    > title/icon name in 0.9.2 anyway...but I didn't try for very long, so
    > I may have missed something.)
    
    After further investigation, I'd like to point out the following:
    
    Eterm has *never* allowed any control characters in its title/icon
    name sequences.  The following bit of code has existed at least since
    Eterm was first committed to CVS:
    
                    else if (ch < ' ')
                        return;     /* control character - exit */
    
    in term.c::process_xterm_seq(), line 1270 or so.
    
    So there was never any way to get escape sequences in the title to
    begin with, meaning that the command cannot be hidden using any
    character attributes or background/foreground color matching.
    
    Furthermore, the title which is printed via the \e[21t sequence is
    limited to just under 1024 characters, which is not enough to cause
    the command to scroll off the screen on any but the smallest of
    terminals.
    
    Thus, the following footnote from the original report applies to Eterm
    as well:
    
        [1] Although putty would place the title onto the command-line, we
        were not able to find a method of hiding the command, since
        neither the "invisible" character attribute nor the foreground
        color could be set. Putty has a relatively low limit to the number
        of characters that can be placed into the window title, so it is
        not possible to simply flood the screen with garbage and hope the
        command rolls past the current view.
    
    Having said all that, it would seem that Eterm 0.9.2 is not vulnerable
    to ANY of the issues mentioned in this report.  As such, all
    distributions shipping older versions of Eterm should be safe after
    upgrading to 0.9.2.  To that end, Eterm source and RPM packages are
    available for download at http://www.eterm.org/download/ for any
    vendor/user with 0.9.1 or earlier.
    
    Hope that clears everything up. :-)
    
    Regards,
    Michael
    
    -- 
    Michael Jennings (a.k.a. KainX)  http://www.kainx.org/  <mejat_private>
    n + 1, Inc., http://www.nplus1.net/       Author, Eterm (www.eterm.org)
    -----------------------------------------------------------------------
     "By the time they had diminished from 50 to 8, the other dwarves 
      began to suspect 'Hungry' ..."        -- Gary Larson, "The Far Side"
    



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