Chapter 6. Features

Chapter 6. Features
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How can I prevent my samba server from being used to distribute the Nimda worm?

How can I use samba as a fax server?

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

Samba doesn't work well together with DHCP!

How can I assign NetBIOS names to clients with DHCP?

How do I convert between unix and dos text formats?

Does samba have wins replication support?

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. +

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.

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) +

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"

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. +

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
+

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. +

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

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. +

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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