Samba FAQ
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Chapter 6. Features

Table of Contents

6.1. How can I prevent my samba server from being used to distribute the Nimda worm?

6.2. How can I use samba as a fax server?

6.2.1. Tools for printing faxes
6.2.2. Making the fax-server
6.2.3. Installing the client drivers
6.2.4. Example smb.conf

6.3. Samba doesn't work well together with DHCP!

6.4. How can I assign NetBIOS names to clients with DHCP?

6.5. How do I convert between unix and dos text formats?

6.6. Does samba have wins replication support?

6.1. How can I prevent my samba server from being used to distribute the Nimda worm?

Author: HASEGAWA Yosuke (translated by TAKAHASHI Motonobu)

Nimba Worm is infected through shared disks on a network, as well as through -Microsoft IIS, Internet Explorer and mailer of Outlook series.

At this time, the worm copies itself by the name *.nws and *.eml on -the shared disk, moreover, by the name of Riched20.dll in the folder -where *.doc file is included.

To prevent infection through the shared disk offered by Samba, set -up as follows:

[global]
-  ...
-  # This can break Administration installations of Office2k.
-  # in that case, don't veto the riched20.dll
-  veto files = /*.eml/*.nws/riched20.dll/

By setting the "veto files" parameter, matched files on the Samba -server are completely hidden from the clients and making it impossible -to access them at all.

In addition to it, the following setting is also pointed out by the -samba-jp:09448 thread: when the -"readme.txt.{3050F4D8-98B5-11CF-BB82-00AA00BDCE0B}" file exists on -a Samba server, it is visible only as "readme.txt" and dangerous -code may be executed if this file is double-clicked.

Setting the following, -

  veto files = /*.{*}/

-any files having CLSID in its file extension will be inaccessible from any -clients.

This technical article is created based on the discussion of -samba-jp:09448 and samba-jp:10900 threads.

6.2. How can I use samba as a fax server?

Contributor: Gerhard Zuber

Requirements: -

UNIX box (Linux preferred) with SAMBA and a faxmodem

ghostscript package

mgetty+sendfax package

pbm package (portable bitmap tools)

First, install and configure the required packages. Be sure to read the mgetty+sendfax -manual carefully.

6.2.1. Tools for printing faxes

Your incomed faxes are in: -/var/spool/fax/incoming. Print it with:

for i in *
-do
-g3cat $i | g3tolj | lpr -P hp
-done

g3cat is in the tools-section, g3tolj is in the contrib-section -for printing to HP lasers.

If you want to produce files for displaying and printing with Windows, use -some tools from the pbm-package like the following command: g3cat $i | g3topbm - | ppmtopcx - >$i.pcx -and view it with your favourite Windows tool (maybe paintbrush)

6.2.2. Making the fax-server

fetch the file mgetty+sendfax/frontends/winword/faxfilter and place it in /usr/local/etc/mgetty+sendfax/(replace /usr/local/ with whatever place you installed mgetty+sendfax)

prepare your faxspool file as mentioned in this file -edit fax/faxspool.in and reinstall or change the final -/usr/local/bin/faxspool too.

if [ "$user" = "root" -o "$user" = "fax" -o \
-     "$user" = "lp" -o "$user" = "daemon" -o "$user" = "bin" ]

find the first line and change it to the second.

make sure you have pbmtext (from the pbm-package). This is -needed for creating the small header line on each page.

Prepare your faxheader /usr/local/etc/mgetty+sendfax/faxheader

Edit your /etc/printcap file: -

# FAX 
-lp3|fax:\
-        :lp=/dev/null:\
-        :sd=/usr/spool/lp3:\
-        :if=/usr/local/etc/mgetty+sendfax/faxfilter:sh:sf:mx#0:\
-        :lf=/usr/spool/lp3/fax-log:

Now, edit your smb.conf so you have a smb based printer named "fax"

6.2.3. Installing the client drivers

Now you have a printer called "fax" which can be used via -TCP/IP-printing (lpd-system) or via SAMBA (windows printing).

On every system you are able to produce postscript-files you -are ready to fax.

On Windows 3.1 95 and NT:

Install a printer wich produces postscript output, - e.g. apple laserwriter

Connect the "fax" to your printer.

Now write your first fax. Use your favourite wordprocessor, -write, winword, notepad or whatever you want, and start -with the headerpage.

Usually each fax has a header page. It carries your name, -your address, your phone/fax-number.

It carries also the recipient, his address and his *** fax -number ***. Now here is the trick:

Use the text: -

Fax-Nr: 123456789

-as the recipients fax-number. Make sure this text does not -occur in regular text ! Make sure this text is not broken -by formatting information, e.g. format it as a single entity. -(Windows Write and Win95 Wordpad are functional, maybe newer - versions of Winword are breaking formatting information).

The trick is that postscript output is human readable and -the faxfilter program scans the text for this pattern and -uses the found number as the fax-destination-number.

Now print your fax through the fax-printer and it will be -queued for later transmission. Use faxrunq for sending the -queue out.

6.2.4. Example smb.conf

[global]
- printcap name = /etc/printcap
- print command = /usr/bin/lpr -r -P %p %s
- lpq command = /usr/bin/lpq -P %p
- lprm command = /usr/bin/lprm -P %p %j
-
-[fax]
-    comment = FAX (mgetty+sendfax)
-    path = /tmp
-    printable = yes
-    public = yes
-    writable = no
-    create mode = 0700
-    browseable = yes
-    guest ok = no

6.3. Samba doesn't work well together with DHCP!

We wish to help those folks who wish to use the ISC DHCP Server and provide -sample configuration settings. Most operating systems today come ship with -the ISC DHCP Server. ISC DHCP is available from: -ftp://ftp.isc.org/isc/dhcp

Incorrect configuration of MS Windows clients (Windows9X, Windows ME, Windows -NT/2000) will lead to problems with browsing and with general network -operation. Windows 9X/ME users often report problems where the TCP/IP and related -network settings will inadvertantly become reset at machine start-up resulting -in loss of configuration settings. This results in increased maintenance -overheads as well as serious user frustration.

In recent times users on one mailing list incorrectly attributed the cause of -network operating problems to incorrect configuration of Samba.

One user insisted that the only way to provent Windows95 from periodically -performing a full system reset and hardware detection process on start-up was -to install the NetBEUI protocol in addition to TCP/IP. This assertion is not -correct.

In the first place, there is NO need for NetBEUI. All Microsoft Windows clients -natively run NetBIOS over TCP/IP, and that is the only protocol that is -recognised by Samba. Installation of NetBEUI and/or NetBIOS over IPX will -cause problems with browse list operation on most networks. Even Windows NT -networks experience these problems when incorrectly configured Windows95 -systems share the same name space. It is important that only those protocols -that are strictly needed for site specific reasons should EVER be installed.

Secondly, and totally against common opinion, DHCP is NOT an evil design but is -an extension of the BOOTP protocol that has been in use in Unix environments -for many years without any of the melt-down problems that some sensationalists -would have us believe can be experienced with DHCP. In fact, DHCP in covered by -rfc1541 and is a very safe method of keeping an MS Windows desktop environment -under control and for ensuring stable network operation.

Please note that MS Windows systems as of MS Windows NT 3.1 and MS Windows 95 -store all network configuration settings a registry. There are a few reports -from MS Windows network administrators that warrant mention here. It would appear -that when one sets certain MS TCP/IP protocol settings (either directly or via -DHCP) that these do get written to the registry. Even though a subsequent -change of setting may occur the old value may persist in the registry. This -has been known to create serious networking problems.

An example of this occurs when a manual TCP/IP environment is configured to -include a NetBIOS Scope. In this event, when the administrator then changes the -configuration of the MS TCP/IP protocol stack, without first deleting the -current settings, by simply checking the box to configure the MS TCP/IP stack -via DHCP then the NetBIOS Scope that is still persistent in the registry WILL be -applied to the resulting DHCP offered settings UNLESS the DHCP server also sets -a NetBIOS Scope. It may therefore be prudent to forcibly apply a NULL NetBIOS -Scope from your DHCP server. The can be done in the dhcpd.conf file with the -parameter: -option netbios-scope "";

While it is true that the Microsoft DHCP server that comes with Windows NT -Server provides only a sub-set of rfc1533 functionality this is hardly an issue -in those sites that already have a large investment and commitment to Unix -systems and technologies. The current state of the art of the DHCP Server -specification in covered in rfc2132.

6.4. How can I assign NetBIOS names to clients with DHCP?

SMB network clients need to be configured so that all standard TCP/IP name to -address resolution works correctly. Once this has been achieved the SMB -environment provides additional tools and services that act as helper agents in -the translation of SMB (NetBIOS) names to their appropriate IP Addresses. One -such helper agent is the NetBIOS Name Server (NBNS) or as Microsoft called it -in their Windows NT Server implementation WINS (Windows Internet Name Server).

A client needs to be configured so that it has a unique Machine (Computer) -Name.

This can be done, but needs a few NT registry hacks and you need to be able to -speak UNICODE, which is of course no problem for a True Wizzard(tm) :) -Instructions on how to do this (including a small util for less capable -Wizzards) can be found at

http://www.unixtools.org/~nneul/sw/nt/dhcp-netbios-hostname.html

6.5. How do I convert between unix and dos text formats?

Jim barry has written an excellent drag-and-drop cr/lf converter for -windows. Just drag your file onto the icon and it converts the file.

The utilities unix2dos and dos2unix(in the mtools package) should do -the job under unix.

6.6. Does samba have wins replication support?

At the time of writing there is currently being worked on a wins replication implementation(wrepld).

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