diff options
| -rw-r--r-- | docs/docbook/projdoc/Integrating-with-Windows.xml | 98 | ||||
| -rw-r--r-- | docs/docbook/projdoc/InterdomainTrusts.xml | 30 | ||||
| -rw-r--r-- | docs/docbook/projdoc/securing-samba.xml | 399 |
3 files changed, 355 insertions, 172 deletions
diff --git a/docs/docbook/projdoc/Integrating-with-Windows.xml b/docs/docbook/projdoc/Integrating-with-Windows.xml index 9c397172dd..eae51295df 100644 --- a/docs/docbook/projdoc/Integrating-with-Windows.xml +++ b/docs/docbook/projdoc/Integrating-with-Windows.xml @@ -24,6 +24,26 @@ NetBIOS over TCP/IP then this section may help you to resolve networking problem </para> </note> +<sect1> +<title>Features and Benefits</title> + +<para> +Many MS Windows network administrators have never been exposed to basic TCP/IP +networking as it is implemented in a Unix/Linux operating system. Likewise, many Unix and +Linux adminsitrators have not been exposed to the intricacies of MS Windows TCP/IP based +networking (and may have no desire to be either). +</para> + +<para> +This chapter gives a short introduction to the basics of how a name can be resolved to +it's IP address for each operating system environment. +</para> + +</sect1> + +<sect1> +<title>Background Information</title> + <para> Since the introduction of MS Windows 2000 it is possible to run MS Windows networking without the use of NetBIOS over TCP/IP. NetBIOS over TCP/IP uses UDP port 137 for NetBIOS @@ -48,6 +68,7 @@ Use of DHCP with ADS is recommended as a further means of maintaining central co over client workstation network configuration. </para> +</sect1> <sect1> <title>Name Resolution in a pure Unix/Linux world</title> @@ -70,10 +91,10 @@ The key configuration files covered in this section are: Contains a static list of IP Addresses and names. eg: </para> -<para><programlisting> +<para><screen> 127.0.0.1 localhost localhost.localdomain 192.168.1.1 bigbox.caldera.com bigbox alias4box -</programlisting></para> +</screen></para> <para> The purpose of <filename>/etc/hosts</filename> is to provide a @@ -181,10 +202,10 @@ critical configuration file. This file controls the order by which name resolution may procede. The typical structure is: </para> -<para><programlisting> +<para><screen> order hosts,bind multi on -</programlisting></para> +</screen></para> <para> then both addresses should be returned. Please refer to the @@ -205,7 +226,7 @@ file typically has resolver object specifications as follows: </para> -<para><programlisting> +<para><screen> # /etc/nsswitch.conf # # Name Service Switch configuration file. @@ -226,7 +247,7 @@ file typically has resolver object specifications as follows: protocols: nis files rpc: nis files services: nis files -</programlisting></para> +</screen></para> <para> Of course, each of these mechanisms requires that the appropriate @@ -280,7 +301,7 @@ the client/server. The following are typical NetBIOS name/service type registrations: </para> -<para><programlisting> +<para><screen> Unique NetBIOS Names: MACHINENAME<00> = Server Service is running on MACHINENAME MACHINENAME<03> = Generic Machine Name (NetBIOS name) @@ -292,7 +313,7 @@ The following are typical NetBIOS name/service type registrations: WORKGROUP<1c> = Domain Controllers / Netlogon Servers WORKGROUP<1d> = Local Master Browsers WORKGROUP<1e> = Internet Name Resolvers -</programlisting></para> +</screen></para> <para> It should be noted that all NetBIOS machines register their own @@ -392,7 +413,7 @@ to IP address mapping. It typically looks like: </para> -<para><programlisting> +<para><screen> # Copyright (c) 1998 Microsoft Corp. # # This is a sample LMHOSTS file used by the Microsoft Wins Client (NetBIOS @@ -469,7 +490,7 @@ It typically looks like: # so keeping the number of comments to a minimum will improve performance. # Therefore it is not advisable to simply add lmhosts file entries onto the # end of this file. -</programlisting></para> +</screen></para> </sect2> @@ -520,19 +541,19 @@ To configure Samba to be a WINS server the following parameter needs to be added to the &smb.conf; file: </para> -<para><programlisting> +<para><screen> wins support = Yes -</programlisting></para> +</screen></para> <para> To configure Samba to use a WINS server the following parameters are needed in the &smb.conf; file: </para> -<para><programlisting> +<para><screen> wins support = No wins server = xxx.xxx.xxx.xxx -</programlisting></para> +</screen></para> <para> where <replaceable>xxx.xxx.xxx.xxx</replaceable> is the IP address @@ -542,4 +563,53 @@ of the WINS server. </sect2> </sect1> +<sect1> +<title>Common Errors</title> + +<para> +TCP/IP network configuration problems find every network administrator sooner or later. +The cause can be anything from keybaord mishaps, forgetfulness, simple mistakes, and +carelessness. Of course, noone is every deliberately careless! +</para> + + <sect2> + <title>My Boomerang Won't Come Back<title> + + <para> + Well, the real complaint said, "I can ping my samba server from Windows, but I can + not ping my Windows machine from the samba server." + </para> + + <para> + The Windows machine was at IP Address 192.168.1.2 with netmask 255.255.255.0, the + Samba server (Linux) was at IP Address 192.168.1.130 with netmast 255.255.255.128. + The machines were on a local network with no external connections. + <para> + + <para> + Due to inconsistent netmasks, the Windows machine was on network 192.168.1.0/24, while + the Samba server was on network 192.168.1.128/25 - logically a different network. + </para> + + </sect2> + + <sect2> + <title>Very Slow Network Connections</title> + + <para> + A common causes of slow network response includes: + </para> + + <itemizedlist> + <listitem><para>Client is configured to use DNS and DNS server is down</para></listitem> + <listitem><para>Client is configured to use remote DNS server, but remote connection is down</para></listitem> + <listitem><para>Client is configured to use a WINS server, but there is no WINS server</para></listitem> + <listitem><para>Client is NOT configured to use a WINS server, but there is a WINS server</para></listitem> + <listitem><para>Firewall is filtering our DNS or WINS traffic</para></listitem> + </itemizedlist> + + </sect2> + +</sect1> + </chapter> diff --git a/docs/docbook/projdoc/InterdomainTrusts.xml b/docs/docbook/projdoc/InterdomainTrusts.xml index 2c492d4ac0..ae780a4b61 100644 --- a/docs/docbook/projdoc/InterdomainTrusts.xml +++ b/docs/docbook/projdoc/InterdomainTrusts.xml @@ -16,6 +16,25 @@ possible for Samba-3 to NT4 trust (and vice versa), as well as Samba3 to Samba3 </para> <sect1> +<title>Features and Benefits</title> + +<para> +Samba-3 can participate in Samba-to-Samba as well as in Samba-to-MS Windows NT4 style +trust relationships. This imparts to Samba similar scalability as is possible with +MS Windows NT4. +</para> + +<para> +Given that Samba-3 has the capability to function with a scalable backend authentication +database such as LDAP, and given it's ability to run in Primary as well as Backup Domain control +modes, the administrator would be well advised to consider alternatives to the use of +Interdomain trusts simplt because by the very nature of how this works it is fragile. +That was after all a key reason for the development and adoption of Microsoft Active Directory. +</para> + +</sect1> + +<sect1> <title>Trust Relationship Background</title> <para> @@ -219,4 +238,15 @@ the <filename>secrets.tdb</filename> file. </sect2> </sect1> +<sect1> +<title>Common Errors</title> + +<para> +Interdomain trust relationships should NOT be attempted on networks that are unstable +or that suffer regular outages. Network stability and integrity are key concerns with +distributed trusted domains. +</para> + +</sect1> + </chapter> diff --git a/docs/docbook/projdoc/securing-samba.xml b/docs/docbook/projdoc/securing-samba.xml index 204fceeb4a..58634fba35 100644 --- a/docs/docbook/projdoc/securing-samba.xml +++ b/docs/docbook/projdoc/securing-samba.xml @@ -3,7 +3,7 @@ <chapterinfo> &author.tridge; &author.jht; - <pubdate>17 March 2003</pubdate> + <pubdate>May 26, 2003</pubdate> </chapterinfo> <title>Securing Samba</title> @@ -16,209 +16,292 @@ important security fix. The information contained here applies to Samba installations in general. </para> -</sect1> - -<sect1> -<title>Using host based protection</title> - -<para> -In many installations of Samba the greatest threat comes for outside -your immediate network. By default Samba will accept connections from -any host, which means that if you run an insecure version of Samba on -a host that is directly connected to the Internet you can be -especially vulnerable. -</para> - -<para> -One of the simplest fixes in this case is to use the <command>hosts allow</command> and -<command>hosts deny</command> options in the Samba &smb.conf; configuration file to only -allow access to your server from a specific range of hosts. An example -might be: -</para> - -<para><programlisting> - hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24 - hosts deny = 0.0.0.0/0 -</programlisting></para> - -<para> -The above will only allow SMB connections from 'localhost' (your own -computer) and from the two private networks 192.168.2 and -192.168.3. All other connections will be refused as soon -as the client sends its first packet. The refusal will be marked as a -'not listening on called name' error. -</para> - -</sect1> - -<sect1> -<title>User based protection</title> - <para> -If you want to restrict access to your server to valid users only then the following -method may be of use. In the smb.conf [globals] section put: +A new apprentice reported for duty to the Chief Engineer of a boiler house. He said, "Here I am, +if you will show me the boiler I'll start working on it." Then engineer replied, "You're leaning +on it!" </para> -<para><programlisting> - valid users = @smbusers, jacko -</programlisting></para> - <para> -What this does is, it restricts all server access to either the user <emphasis>jacko</emphasis> -or to members of the system group <emphasis>smbusers</emphasis>. +Security concerns are just like that: You need to know a little about the subject to appreciate +how obvious most of it really is. The challenge for most of us is to discover that first morsel +of knowledge with which we may unlock the secrets of the masters. </para> </sect1> <sect1> - -<title>Using interface protection</title> +<title>Features and Benefits</title> <para> -By default Samba will accept connections on any network interface that -it finds on your system. That means if you have a ISDN line or a PPP -connection to the Internet then Samba will accept connections on those -links. This may not be what you want. +There are three level at which security principals must be observed in order to render a site +at least moderately secure. These are: the perimeter firewall, the configuration of the host +server that is running Samba, and Samba itself. </para> <para> -You can change this behaviour using options like the following: +Samba permits a most flexible approach to network security. As far as possible Samba implements +the latest protocols to permit more secure MS Windows file and print operations. </para> -<para><programlisting> - interfaces = eth* lo - bind interfaces only = yes -</programlisting></para> - <para> -This tells Samba to only listen for connections on interfaces with a -name starting with 'eth' such as eth0, eth1, plus on the loopback -interface called 'lo'. The name you will need to use depends on what -OS you are using, in the above I used the common name for Ethernet -adapters on Linux. +Samba may be secured from connections that originate from outside the local network. This may be +done using <emphasis>host based protection</emphasis> (using samba's implementation of a technology +known as "tcpwrappers", or it may be done be using <emphasis>interface based exclusion</emphasis> +so that <command>smbd</command> will bind only to specifically permitted interfaces. It is also +possible to set specific share or resource based exclusions, eg: on the <parameter>IPC$</parameter> +auto-share. The <parameter>IPC$</parameter> share is used for browsing purposes as well as to establish +TCP/IP connections. </para> <para> -If you use the above and someone tries to make a SMB connection to -your host over a PPP interface called 'ppp0' then they will get a TCP -connection refused reply. In that case no Samba code is run at all as -the operating system has been told not to pass connections from that -interface to any samba process. +Another method by which Samba may be secured is by way of setting Access Control Entries in an Access +Control List on the shares themselves. This is discussed in the chapter on File, Directory and Share Access +Control. </para> </sect1> <sect1> -<title>Using a firewall</title> +<title>Technical Discussion of Protective Measures and Issues</title> <para> -Many people use a firewall to deny access to services that they don't -want exposed outside their network. This can be a very good idea, -although I would recommend using it in conjunction with the above -methods so that you are protected even if your firewall is not active -for some reason. -</para> - -<para> -If you are setting up a firewall then you need to know what TCP and -UDP ports to allow and block. Samba uses the following: -</para> - -<para><programlisting> - UDP/137 - used by nmbd - UDP/138 - used by nmbd - TCP/139 - used by smbd - TCP/445 - used by smbd -</programlisting></para> - -<para> -The last one is important as many older firewall setups may not be -aware of it, given that this port was only added to the protocol in -recent years. +The key challenge of security is the fact that protective measures suffice at best +only to close the door on known exploits and breach techniques. Never assume that +because you have followed these few measures that the Samba server is now an impenetrable +fortress! Given the history of information systems so far, it is only a matter of time +before someone will find yet another vulnerability. </para> + <sect2> + <title>Using host based protection</title> + + <para> + In many installations of Samba the greatest threat comes for outside + your immediate network. By default Samba will accept connections from + any host, which means that if you run an insecure version of Samba on + a host that is directly connected to the Internet you can be + especially vulnerable. + </para> + + <para> + One of the simplest fixes in this case is to use the <command>hosts allow</command> and + <command>hosts deny</command> options in the Samba &smb.conf; configuration file to only + allow access to your server from a specific range of hosts. An example + might be: + </para> + + <para><screen> + hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24 + hosts deny = 0.0.0.0/0 + </screen></para> + + <para> + The above will only allow SMB connections from 'localhost' (your own + computer) and from the two private networks 192.168.2 and + 192.168.3. All other connections will be refused as soon + as the client sends its first packet. The refusal will be marked as a + 'not listening on called name' error. + </para> + + </sect2> + + <sect2> + <title>User based protection</title> + + <para> + If you want to restrict access to your server to valid users only then the following + method may be of use. In the smb.conf [globals] section put: + </para> + + <para><screen> + valid users = @smbusers, jacko + </screen></para> + + <para> + What this does is, it restricts all server access to either the user <emphasis>jacko</emphasis> + or to members of the system group <emphasis>smbusers</emphasis>. + </para> + + </sect2> + + <sect2> + + <title>Using interface protection</title> + + <para> + By default Samba will accept connections on any network interface that + it finds on your system. That means if you have a ISDN line or a PPP + connection to the Internet then Samba will accept connections on those + links. This may not be what you want. + </para> + + <para> + You can change this behaviour using options like the following: + </para> + + <para><screen> + interfaces = eth* lo + bind interfaces only = yes + </screen></para> + + <para> + This tells Samba to only listen for connections on interfaces with a + name starting with 'eth' such as eth0, eth1, plus on the loopback + interface called 'lo'. The name you will need to use depends on what + OS you are using, in the above I used the common name for Ethernet + adapters on Linux. + </para> + + <para> + If you use the above and someone tries to make a SMB connection to + your host over a PPP interface called 'ppp0' then they will get a TCP + connection refused reply. In that case no Samba code is run at all as + the operating system has been told not to pass connections from that + interface to any samba process. + </para> + + </sect2> + + <sect2> + <title>Using a firewall</title> + + <para> + Many people use a firewall to deny access to services that they don't + want exposed outside their network. This can be a very good idea, + although I would recommend using it in conjunction with the above + methods so that you are protected even if your firewall is not active + for some reason. + </para> + + <para> + If you are setting up a firewall then you need to know what TCP and + UDP ports to allow and block. Samba uses the following: + </para> + + <para><screen> + UDP/137 - used by nmbd + UDP/138 - used by nmbd + TCP/139 - used by smbd + TCP/445 - used by smbd + </screen></para> + + <para> + The last one is important as many older firewall setups may not be + aware of it, given that this port was only added to the protocol in + recent years. + </para> + + </sect2> + + <sect2> + <title>Using a IPC$ share deny</title> + + <para> + If the above methods are not suitable, then you could also place a + more specific deny on the IPC$ share that is used in the recently + discovered security hole. This allows you to offer access to other + shares while denying access to IPC$ from potentially untrustworthy + hosts. + </para> + + <para> + To do that you could use: + </para> + + <para><screen> + [ipc$] + hosts allow = 192.168.115.0/24 127.0.0.1 + hosts deny = 0.0.0.0/0 + </screen></para> + + <para> + this would tell Samba that IPC$ connections are not allowed from + anywhere but the two listed places (localhost and a local + subnet). Connections to other shares would still be allowed. As the + IPC$ share is the only share that is always accessible anonymously + this provides some level of protection against attackers that do not + know a username/password for your host. + </para> + + <para> + If you use this method then clients will be given a 'access denied' + reply when they try to access the IPC$ share. That means that those + clients will not be able to browse shares, and may also be unable to + access some other resources. + </para> + + <para> + This is not recommended unless you cannot use one of the other + methods listed above for some reason. + </para> + + </sect2> + + <sect2> + <title>NTLMv2 Security</title> + + <para> + To configure NTLMv2 authentication the following registry keys are worth knowing about: + </para> + + <para> + <screen> + [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa] + "lmcompatibilitylevel"=dword:00000003 + + 0x3 - Send NTLMv2 response only. Clients will use NTLMv2 authentication, + use NTLMv2 session security if the server supports it. Domain + controllers accept LM, NTLM and NTLMv2 authentication. + + [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0] + "NtlmMinClientSec"=dword:00080000 + + 0x80000 - NTLMv2 session security. If either NtlmMinClientSec or + NtlmMinServerSec is set to 0x80000, the connection will fail if NTLMv2 + session security is not negotiated. + </screen> + </para> + </sect2> </sect1> <sect1> -<title>Using a IPC$ share deny</title> - -<para> -If the above methods are not suitable, then you could also place a -more specific deny on the IPC$ share that is used in the recently -discovered security hole. This allows you to offer access to other -shares while denying access to IPC$ from potentially untrustworthy -hosts. -</para> - -<para> -To do that you could use: -</para> - -<para><programlisting> - [ipc$] - hosts allow = 192.168.115.0/24 127.0.0.1 - hosts deny = 0.0.0.0/0 -</programlisting></para> - -<para> -this would tell Samba that IPC$ connections are not allowed from -anywhere but the two listed places (localhost and a local -subnet). Connections to other shares would still be allowed. As the -IPC$ share is the only share that is always accessible anonymously -this provides some level of protection against attackers that do not -know a username/password for your host. -</para> - -<para> -If you use this method then clients will be given a 'access denied' -reply when they try to access the IPC$ share. That means that those -clients will not be able to browse shares, and may also be unable to -access some other resources. -</para> +<title>Upgrading Samba</title> <para> -This is not recommended unless you cannot use one of the other -methods listed above for some reason. +Please check regularly on <ulink url="http://www.samba.org/">http://www.samba.org/</ulink> for updates and +important announcements. Occasionally security releases are made and +it is highly recommended to upgrade Samba when a security vulnerability +is discovered. </para> </sect1> <sect1> -<title>NTLMv2 Security</title> +<title>Common Errors</title> <para> -To configure NTLMv2 authentication the following registry keys are worth knowing about: +If all of samba and host platform configuration were really as intuitive as one might like then this +section would not be necessary. Security issues are often vexing for a support person to resolve, not +because of the complexity of the problem, but for reason that most admininstrators who post what turns +out to be a security problem request are totally convinced that the problem is with Samba. </para> -<para> -<programlisting> - [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa] - "lmcompatibilitylevel"=dword:00000003 - - 0x3 - Send NTLMv2 response only. Clients will use NTLMv2 authentication, - use NTLMv2 session security if the server supports it. Domain - controllers accept LM, NTLM and NTLMv2 authentication. + <sect2> + <title>Smbclient works on localhost, but the network is dead</title> - [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0] - "NtlmMinClientSec"=dword:00080000 + <para> + This is a very common problem. Red Hat Linux (as do others) will install a default firewall. + With the default firewall in place only traffic on the loopback adapter (IP address 127.0.0.1) + will be allowed through the firewall. + </para> - 0x80000 - NTLMv2 session security. If either NtlmMinClientSec or - NtlmMinServerSec is set to 0x80000, the connection will fail if NTLMv2 - session security is not negotiated. -</programlisting> -</para> -</sect1> + <para> + The solution is either to remove the firewall (stop it) or to modify the firewall script to + allow SMB networking traffic through. See section above in this chapter. + </para> -<sect1> -<title>Upgrading Samba</title> - -<para> -Please check regularly on <ulink url="http://www.samba.org/">http://www.samba.org/</ulink> for updates and -important announcements. Occasionally security releases are made and -it is highly recommended to upgrade Samba when a security vulnerability -is discovered. -</para> + </sect2> </sect1> - </chapter> |