Re: WWW-safe Forth?

Newsgroups	comp.lang.forth
Date	2013-07-06 12:03 -0700
References	<kr76h9$dqd$1@odin.sdf-eu.org>
Message-ID	<0897f137-9711-4eb8-b43b-41f99bc07f11@googlegroups.com> (permalink)
Subject	Re: WWW-safe Forth?
From	Howerd <howerdo@yahoo.co.uk>

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On Friday, July 5, 2013 9:24:26 PM UTC+2, David Meyer wrote:
> I am thinking about making a CGI script available on the WWW that feeds 
> 
> user input to a Forth interpreter and displays the results. It will be a 
> 
> web-based Forth calculator. (Dictionary and stack persistence between 
> 
> queries will be considered for future implementation.)
> 
> 
> 
> The CGI script will be run with suEXEC, so security is of special concern.
> 
> 
> 
> I am assuming that as with all CGI scripts, the biggest vulnerabilities 
> 
> are with passing user-supplied strings to the operating system (for 
> 
> example, with Gforth's SYSTEM command) and file I/O.
> 
> 
> 
> One partial solution is to use a Forth interpreter that doesn't support 
> 
> the dangerous commands. However, although I have found some Forth 
> 
> interpreters that don't have the equivalent of SYSTEM, it's harder to find 
> 
> ones that have no file I/O facility and still support a large enough 
> 
> subset of standard words to be useful.
> 
> 
> 
> I have thought of redefining all dangerous words to do something harmless 
> 
> before processing the user's query string. Can this not be undone by a 
> 
> user? Is there a better way to block access to particular words?
> 
> 
> 
> Are there any other security issues I haven't thought of?
> 
> 
> 
> 
> 
> 
> 
> -- 
> 
> p...@sdf.lonestar.org
> 
> SDF Public Access UNIX System - http://sdf.lonestar.org

Hi David,

I would say that it is very easy to create a safe Forth - you need to do four things :
1. use a sealed vocabulary ( AKA wordlist ) for the application.
2. redefine @ ! and anything else that accesses memory to be limited to a safe memory area.
3. define a pseudo return stack for >r r@ and r> (if you want to include these at all).
4. Do not include  execute and dangerous sys-call words in the sealed vocabulary.

Am I missing something here? Because this sounds so much simpler than the other suggestions...

Best regards,
Howerd

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Thread

WWW-safe Forth? papa@sdf.lNoOnSePsAtMar.org (David Meyer) - 2013-07-05 19:24 +0000
  Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-05 13:37 -0700
    Re: WWW-safe Forth? papa@sdf.lNoOnSePsAtMar.org (David Meyer) - 2013-07-05 21:17 +0000
      Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-05 15:22 -0700
        Re: WWW-safe Forth? papa@sdf.lNoOnSePsAtMar.org (David Meyer) - 2013-07-06 01:56 +0000
      Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-06 14:42 +0200
        Re: WWW-safe Forth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-07-06 07:56 -0500
          Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-07 01:11 +0200
            Re: WWW-safe Forth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-07-07 02:44 -0500
              Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-07 10:28 +0000
        Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-06 13:42 +0000
          Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-07 01:40 +0200
  Re: WWW-safe Forth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-07-05 20:20 +0000
  Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-06 12:41 -0400
  Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-06 12:03 -0700
    Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-06 12:41 -0700
      Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-06 14:01 -0700
        Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-06 14:26 -0700
          Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-06 12:32 -1000
            Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-06 19:58 -0700
              Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-06 18:14 -1000
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-06 21:51 -0700
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-06 21:01 -1000
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 00:36 -0700
              Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-07 01:25 -0700
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 01:56 -0700
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-07 08:34 -1000
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-07 07:08 -0400
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-07 08:41 -1000
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 12:59 -0700
                Re: WWW-safe Forth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-07-07 20:18 +0000
                Re: WWW-safe Forth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-07-09 01:09 +0000
                Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-08 00:09 +0200
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 18:15 -0700
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-07 17:22 -1000
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-07 17:20 -1000
                Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-07 13:13 -0700
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 14:02 -0700
                Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-08 01:25 +0200
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 18:26 -0700
                Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-09 19:21 +0200
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-10 01:55 -0700
                Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-10 23:51 +0200
                Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-07 21:10 -0700
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 22:03 -0700
                Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-07 22:27 -0700
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-08 00:30 -0700
                Re: WWW-safe Forth? Hannu Vuolasaho <hannu.vuolasaho@nospam.tut.fi.invalid> - 2013-07-08 13:08 +0000
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-08 09:18 -0400
                Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-08 07:02 -0700
                Re: WWW-safe Forth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-07-08 09:46 -0500
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-08 11:04 -0700
                Re: WWW-safe Forth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-07-08 12:49 -0500
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-08 11:26 -0700
                Re: WWW-safe Forth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-07-08 16:28 -0500
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-08 11:15 -1000
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-09 17:09 -0400
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-09 12:02 -1000
                Re: WWW-safe Forth? Hans Bezemer <the.beez.speaks@gmail.com> - 2013-07-10 23:52 +0200
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-12 03:04 -0400
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-12 03:31 -0400
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-11 23:03 -1000
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-14 18:15 -0400
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-14 13:50 -1000
                Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-15 14:12 +0000
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-15 10:22 -0700
                Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-15 17:07 +0000
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-17 01:12 -0700
                Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-17 09:43 +0000
                Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-17 15:04 +0200
                Re: WWW-safe Forth? albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-07-17 13:50 +0000
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-15 07:57 -1000
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-15 22:45 -0400
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-15 18:21 -1000
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-15 07:52 -1000
                Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-16 16:15 +0000
                Re: WWW-safe Forth? "Elizabeth D. Rather" <erather@forth.com> - 2013-07-16 08:17 -1000
                Re: WWW-safe Forth? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-07-17 09:33 +0000
                Re: WWW-safe Forth? "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-07-15 22:40 -0400
                Re: WWW-safe Forth? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-07-10 03:26 -0500
              Re: WWW-safe Forth? Howerd <howerdo@yahoo.co.uk> - 2013-07-07 01:46 -0700
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 02:39 -0700
                Re: WWW-safe Forth? AKK <akk@nospam.org> - 2013-07-07 11:56 +0200
                Re: WWW-safe Forth? Paul Rubin <no.email@nospam.invalid> - 2013-07-07 03:20 -0700
      Re: WWW-safe Forth? Bernd Paysan <bernd.paysan@gmx.de> - 2013-07-07 01:21 +0200
  Re: WWW-safe Forth? Hans Bezemer <the.beez.speaks@gmail.com> - 2013-07-09 23:22 +0200

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