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1995-10-24 - Re: Does your software?

Header Data

From: fc@all.net (Dr. Frederick B. Cohen)
To: rjc@clark.net (Ray Cromwell)
Message Hash: 1194dd1a301a450f7b327418ca6bf1455bc2a12400a807ccd1e8364b81954b56
Message ID: <9510242251.AA05075@all.net>
Reply To: <199510242238.SAA19929@clark.net>
UTC Datetime: 1995-10-24 22:54:11 UTC
Raw Date: Tue, 24 Oct 95 15:54:11 PDT

Raw message

From: fc@all.net (Dr. Frederick B. Cohen)
Date: Tue, 24 Oct 95 15:54:11 PDT
To: rjc@clark.net (Ray Cromwell)
Subject: Re: Does your software?
In-Reply-To: <199510242238.SAA19929@clark.net>
Message-ID: <9510242251.AA05075@all.net>
MIME-Version: 1.0
Content-Type: text


>   Umm, your get only server sounds like it is secure, but what is the
> point advertising it to this list?

I wasn't advertising.  I was simply answering questions brought up about
my secure W3 server by another person who posted to the list.  For some
reason they thought that they should bring it into the discussion, so I
responded. 

> I could program a GET only
> server in far fewer than 80 lines in just a few hours.

As I have said many times to many others, please go ahead and do it.  I
only wrote the secure server to demonstrate that it was no big deal to
have a secure server and to ease my own fears about protecting all.net
from outside attacks like the ones with buffer overflows.  The source is
on-line and available to anyone, and I only ask a fee if you decide to
use it for commercial purposes.  Nobody has paid me yet, and I assume
they never will.

> You could
> do it in even fewer lines of perl, or /bin/sh.

But how would you demonstrate the security properties?

> A real HTTP server
> must support all of HTTP/1.0 however for it to be considered a server.

It's a secure get-only server.  It only handles 99+% of the real uses of
web servers.

> Since yours doesn't, it isn't, it's just a toy. a better project would be
> to make HTTP requests under CERN more secure.

I agree, but rather than redesign their server, I wrote my own in a few
hours and made it available as an example.  I think that CERN should
make their server secure.

>  In fact, if you don't
> handle CGI, you can't handle forms, which means you can't handle
> commerce securely.

I now do handle forms (another separate 100 line server not yet released).
Please see the experimental version on-line at all.net.

> secure perl "get only" server server
> copy perl to a secure filesystem
> have a chroot c-wrapper there
> the wrapper chroot's to this directory and runs the perl script
> perl is effectively boxed in

My secure server includes the chroot  and setUID code in it.  Your C-wrapper
would be part of your code - that adds several lines.  And I don't need Perl
which I think makes it much more secure.  (There I go casting doubts on Perl
security!)

> #!/securedir/perl
> 
> $line = <STDIN>;
> ($method, $url, $protocol)=split(/\s+/, $line);
> $url =~ s/[^a-zA-Z0-9_]/g;
> if($method =~ /^GET/i)
> {
>    open(FILE, "$url");
>    print "HTTP/1.0 200 OK\nContent-Type: text/html\n\n";
>    print <FILE>;
>    close(FILE);
> }
> 
> exit 0;

Pretty close, but you don't provide any protection against denial of
services (e.g.  by openning up 1024 simultaneous sessions and leaving
them open indefinately) against accessing files that aren't there (you
need an error message of some sort - mine does a redirect to the home
page), you don't enforce access controls on the host machine, there may
be buffer overflows associated with long requests, you don't handle some
possible URLs, you don't seem to handle the default URL, you don't
identify the kind of error that caused the failed access, and you don't
provide an audit trail.  Add those and I'll look again to see if there
are other possible problems.

-- 
-> See: Info-Sec Heaven at URL http://all.net
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