From: Hal <hfinney@shell.portal.com>
Date: Fri, 4 Aug 95 16:37:13 PDT
To: cypherpunks@toad.com
Subject: Re: Java and Safe-TCL security
Message-ID: <199508042336.QAA15267@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


From: Ray Cromwell <rjc@clark.net>
> Hal,
>   One of the designs I have one the drawing board is to store per-script 
> persistent data in a dbm file, and allow scripts to import/export data
> from/to a shared tuple-space. I would limit the data storage to 1024
> bytes (to make it portable, some DBM libraries have this limit)
>   Scripts could store variables via a new command added to the interpreter
> like 'SafeTcl_putvar varname value', and access valuables with
> 'SafeTcl_getvar varname', 'SafeTcl_varlist'. Also, there would be a
> 'SafeTcl_read_variables' which could be executed at the beginning of
> the script to reload all stored variables. 
>   Scripts could talk to other scripts by means of a 
> 
> 	SafeTcl_export -value value scriptname1 scriptname2 ...
>  
>   The other script(s) could check for any incoming imports and use 
> SafeTcl_import to retrieve the value. (when the last import is done,
> the data is garbage collected. Also, there would be a timestamp so that
> old data would be purged after a time limit anyway)

This sounds like an interesting approach.  I hear that Telescript uses a
remote procedure call concept for inter-script communication.  So one
script gets to call the public methods of another script.  I don't know
how it finds out what other scripts are arround for it to talk to,
though, or decides whether they have anything of interest.

The tuple space idea sounds good and is not too dissimmilar from the
get/setconfigdata in safe-tcl.  There are some problems about security
though.  Who gets to delete tuples?  How do you prevent a malicious
script from messing up the data?  Maybe it depends on the application,
what you want to use this data for.

BTW what kinds of facilities are there in Java for scripts to have access
to disk files?  I know there was some discussion of using scripts for
cryptography.  Presumably the user would want to give "read only" access
to the (public) keys he used.

And how about other forms of I/O, email and the like?  Can Java scripts
do this?  What are the restrictions to prevent abuse?  Safe-tcl has a
concept where a script can send mail, but the implementation pops up a
window and asks the user first if it is OK to send.  (Unfortunately that
doesn't work for a telescript like application where there is no user
around to vet the messages.)

>   The problem with all safe "agent" designs is that the programming language
> itself isn't enough. There needs to be a meta-agent language for 
> querying capabilities of local environments.

Yes, there was some discussion about this on the safe-tcl list.  There is
also an agents list I was on for a while but they couldn't even agree
about what an agent was so not much progress happened there!  There have
been various proposals for standard ways agent scripts could specify what
capabilities they need to run, etc.  Doing web searches on "agents" will
track a lot of these down.  However most seem concerned with traditional
issues like compute cycles, memory usage, etc., and not with the more
difficult and important issues of knowing whether there is another agent
there (or a local database) which has the specific information my agent
is after.

Hal