One Question about security Post: 302074189

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Special Forums Cybersecurity One Question about security Post 302074189 by hegemaro on Sunday 21st of May 2006 08:23:27 AM

05-21-2006

Registered User

I have been supporting a dialup BBS -- yes they still exist -- for five years now. Telnet itself is not an inherently insecure protocol nor are most daemon implementations any more buggy than, say, FTP. Stay current with patches and you'll be fine on that point. There are two issues that you must consider:

1 ) Transmission of account and password information in plain text

Since the server is Internet facing, it is quite possible that someone could intercept a valid user's account/password information and use it for nefarious activities. Depending on your server configuration, that account may also grant the intruder access to through other services such as FTP or mail.

2 ) Shell access to the server.

Unlike HTTP which can more readily be limited to specific areas of the system, shell access throws open the floodgates to your system and any weaknesses in configuration. Using restricted shells does little as there are numerous ways to bypass that limited security.

Here are some ideas:

As System Shock suggested, Secure Shell can completely address Issue #1 by encrypting not only the data stream once logged in but also the account information as the user logs in. It is freely available from http://www.openssh.org/. It is moderately complex to compile and configure but it will integerate seamlessly with your existing application; it is simply a replacement for Telnet not the application already running on the system.

The down-side is that it requires your users to use an SSH client to connect to your server. Telnet and Hyperterminal will no longer work. This can be a deal-breaker.

The second issue can be addressed with a "change root" jail in which the user is locked into a subdirectory structure of the entire file system. I have no direct experience myself but the http://www.jmcresearch.com/projects/jail/ reference has been suggested. There may be issues integrating with your application but I can not say what they would be.

So, what to do?

The most important thing is to harden your server to the point of paranoia. There are many documents on how this can be achieved but here are a few general suggestions.

Disable ALL unnecessary network services ideally leaving Telnet only.
Lock all system accounts except root, of course, restricting root access to the console only.
Enforce a strict password policy with an 8-character minimum length and frequent password changes.
Isolate your server from the rest of your network. Firewalls work fine but physical isolation is not susceptible to configuration errors. To simplify periodic access to the server, a second interface can be added with a cross-over connection to another server. On your Internet facing system, the interface can be left up while on the cross-over server, bring down the interface when not in use.
PATCHES!! Stay on top of all security patches for your environment. This is most important and most overlooked.

hegemaro

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LEARN ABOUT SUNOS

ftpconfig

ftpconfig(1M)						  System Administration Commands					     ftpconfig(1M)

NAME

       ftpconfig - set up anonymous FTP

SYNOPSIS

       ftpconfig [ftpdir]

       ftpconfig -d ftpdir

DESCRIPTION

       The ftpconfig script is executed by the super user to set up anonymous FTP. Anonymous FTP allows users to remotely log on to the FTP server
       by specifying the user name  ftp or anonymous and the user's email  address as password. The anonymous users  are  logged  on  to  the  FTP
       Server  and  given  access to a restricted file area with its own file system root. See chroot(2). The FTP area has  its own minimal system
       files.

       This command will copy and set up all the components needed to operate an anonymous FTP server, including creating the  ftp  user  account,
       creating  device  nodes,  copying  /usr/lib files, and copying timezone data.  The passwd and group files set up have been stripped down to
       prevent malicious users from finding login names on the server.	The anonymous file area will be placed	under  ftpdir.	If  the  ftp  user
       account already exists, then the current FTP area is used, and the system files in it are updated. All other files are left untouched. This
       command should be run to update the anonymous FTP area's configuration whenever a system patch is installed, or the system is upgraded.

OPTIONS

       -d	Create a new or update an existing ftpdir without creating or updating the ftp user account. Use this option when  creating  guest
		FTP user accounts.

OPERANDS

       The following operands are supported:

       ftpdir	The absolute pathname of the directory under which the anonymous FTP area is set up.

EXIT STATUS

       The following exit values are returned:

       0	Successful completion

       1	Improper usage of the command

       2	Command failed

ATTRIBUTES

       See attributes(5)  for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWftpu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ftpaddhost(1M), in.ftpd(1M), useradd(1M), chroot(2), attributes(5)

SunOS 5.10							    1 May 2003							     ftpconfig(1M)

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