Re: Internal IP Exposed

Karl Denninger <karl@xxxxxxxxxxxxx> · Sun, 24 Mar 2019 19:46:56 -0500



    On 3/24/2019 19:33, Abdul Qoyyuum
      wrote:

    
        Hi all,
        

        New to the mailing list and a complete newbie to openssl
          and the likes. There's a ticket by a client that I'm new at
          and he claims that there's a security problem with the openssl
          command to his servers.
        
          Internal IP exposed after running a openssl (version
            1.1.0j) connect command:
          openssl s_client -connect 103.XX.XXX.XX:10443 -quiet

          Where 103.XX.XXX.XX is a Public IP. And after it shows the
            certificates, typed the following:
          GET /images HTTP/1.0

          And hit enter twice, the following gets displayed:
          HTTP/1.0 301 Moved Permanently
Date: Mon, 25 Mar 2019 00:10:13 GMT
Server: xxxxxxxx-xxxxx
Location: https://10.240.123.1:10443/images/
Connection: close
Content-Type: text/html; charset=utf-8
X-Frame-Options: SAMEORIGIN
Content-Security-Policy: frame-ancestors 'self'
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Strict-Transport-Security: max-age=28800

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML><HEAD>
<TITLE>301 Moved Permanently</TITLE>
</HEAD><BODY>
<H1>Moved Permanently</H1>
The document has moved <A HREF=""https://10.240.123.1:10443/images/" moz-do-not-send="true">https://10.240.123.1:10443/images/">here</A>.<P>
</BODY></HTML>
read:errno=0

          The 10.240.123.1 is an internal IP and it is exposed by
            this little method. Although not shown when using curl
              -kv -O command.
          Is there a way to cover up the "Location" or at least the
            internal IP from being exposed? Thanks.
        
        Sorry if this isn't clear or if this is the wrong place to
          ask this.
        

    OpenSSL is not involved in that in any way so the fix and issue
      is not there.
    I am assuming that the original connection is to a "tunnel" on
      the internal/external gateway.  That is, connect to
      <a.b.c.d:10443> and the gateway "twists" that to the
      internal address on port 443, which is the usual HTTPS port (this
      assumption is due to that looking like an HTTPS server from what
      it returns.)  This is a very common firewall/gateway function.

    
    The issue is that OpenSSL just created and maintained the SSL
      connection and data transport.  The offending information isn't
      emitted by OpenSSL; it's emitted by the remote server code itself
      and OpenSSL simply transports it from one end to the other,
      encrypted.  It thus must (and does) transport exactly,
      byte-by-byte, whatever it gets (in both directions.)
    The server code on the remote end could be programmed to not
      issue the header and body text, but if it generates a 301 the HTML
      header "Location:" MUST be returned with the new location by the
      HTML specifications so the application that connected (typically a
      browser) can issue a new request to the correct, redirected
      place.  However it doesn't have to return an IP number and most
      servers do not because there frequently is more than one host
      and/or domain on a given IP number -- it could and should instead
      return a domain name (e.g. "https://www.example.com/images") --
      but that header has to be there.  The body text actually does not;
      it can be void and it's ok (that's not used by browsers, but is
      useful for humans if/when troubleshooting.)
    The issue is LIKELY that the host in question doesn't have a
      reverse IP mapped for itself but that's web server and OS
      dependent.  It may also be that the hostname is not defined in the
      server's configuration file.  Without knowing what the web server
      in question is all I can do there is guess as to exactly what is
      missing, but in any event the issue is in the web server
      application configuration and not OpenSSL.

    
    -- 

      Karl Denninger

      karl@xxxxxxxxxxxxx

      The Market Ticker

      [S/MIME encrypted email preferred]
    
  
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