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+>LanMan and NT Password Encryption in Samba</TITLE
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+CLASS="CHAPTER"
+><H1
+><A
+NAME="PWENCRYPT">Chapter 4. LanMan and NT Password Encryption in Samba</H1
+><DIV
+CLASS="SECT1"
+><H1
+CLASS="SECT1"
+><A
+NAME="AEN457">4.1. Introduction</H1
+><P
+>Newer windows clients send encrypted passwords over
+ the wire, instead of plain text passwords. The newest clients
+ will only send encrypted passwords and refuse to send plain text
+ passwords, unless their registry is tweaked.</P
+><P
+>These passwords can't be converted to unix style encrypted
+ passwords. Because of that you can't use the standard unix
+ user database, and you have to store the Lanman and NT hashes
+ somewhere else. For more information, see the documentation
+ about the <B
+CLASS="COMMAND"
+>passdb backend = </B
+> parameter.
+ </P
+></DIV
+><DIV
+CLASS="SECT1"
+><H1
+CLASS="SECT1"
+><A
+NAME="AEN462">4.2. Important Notes About Security</H1
+><P
+>The unix and SMB password encryption techniques seem similar
+ on the surface. This similarity is, however, only skin deep. The unix
+ scheme typically sends clear text passwords over the network when
+ logging in. This is bad. The SMB encryption scheme never sends the
+ cleartext password over the network but it does store the 16 byte
+ hashed values on disk. This is also bad. Why? Because the 16 byte hashed
+ values are a "password equivalent". You cannot derive the user's
+ password from them, but they could potentially be used in a modified
+ client to gain access to a server. This would require considerable
+ technical knowledge on behalf of the attacker but is perfectly possible.
+ You should thus treat the smbpasswd file as though it contained the
+ cleartext passwords of all your users. Its contents must be kept
+ secret, and the file should be protected accordingly.</P
+><P
+>Ideally we would like a password scheme which neither requires
+ plain text passwords on the net or on disk. Unfortunately this
+ is not available as Samba is stuck with being compatible with
+ other SMB systems (WinNT, WfWg, Win95 etc). </P
+><DIV
+CLASS="WARNING"
+><P
+></P
+><TABLE
+CLASS="WARNING"
+WIDTH="100%"
+BORDER="0"
+><TR
+><TD
+WIDTH="25"
+ALIGN="CENTER"
+VALIGN="TOP"
+><IMG
+SRC="../images/warning.gif"
+HSPACE="5"
+ALT="Warning"></TD
+><TD
+ALIGN="LEFT"
+VALIGN="TOP"
+><P
+>Note that Windows NT 4.0 Service pack 3 changed the
+ default for permissible authentication so that plaintext
+ passwords are <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>never</I
+></SPAN
+> sent over the wire.
+ The solution to this is either to switch to encrypted passwords
+ with Samba or edit the Windows NT registry to re-enable plaintext
+ passwords. See the document WinNT.txt for details on how to do
+ this.</P
+><P
+>Other Microsoft operating systems which also exhibit
+ this behavior includes</P
+><P
+></P
+><UL
+><LI
+><P
+>MS DOS Network client 3.0 with
+ the basic network redirector installed</P
+></LI
+><LI
+><P
+>Windows 95 with the network redirector
+ update installed</P
+></LI
+><LI
+><P
+>Windows 98 [se]</P
+></LI
+><LI
+><P
+>Windows 2000</P
+></LI
+></UL
+><P
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>Note :</I
+></SPAN
+>All current release of
+ Microsoft SMB/CIFS clients support authentication via the
+ SMB Challenge/Response mechanism described here. Enabling
+ clear text authentication does not disable the ability
+ of the client to participate in encrypted authentication.</P
+></TD
+></TR
+></TABLE
+></DIV
+><DIV
+CLASS="SECT2"
+><H2
+CLASS="SECT2"
+><A
+NAME="AEN481">4.2.1. Advantages of SMB Encryption</H2
+><P
+></P
+><UL
+><LI
+><P
+>plain text passwords are not passed across
+ the network. Someone using a network sniffer cannot just
+ record passwords going to the SMB server.</P
+></LI
+><LI
+><P
+>WinNT doesn't like talking to a server
+ that isn't using SMB encrypted passwords. It will refuse
+ to browse the server if the server is also in user level
+ security mode. It will insist on prompting the user for the
+ password on each connection, which is very annoying. The
+ only things you can do to stop this is to use SMB encryption.
+ </P
+></LI
+></UL
+></DIV
+><DIV
+CLASS="SECT2"
+><H2
+CLASS="SECT2"
+><A
+NAME="AEN488">4.2.2. Advantages of non-encrypted passwords</H2
+><P
+></P
+><UL
+><LI
+><P
+>plain text passwords are not kept
+ on disk. </P
+></LI
+><LI
+><P
+>uses same password file as other unix
+ services such as login and ftp</P
+></LI
+><LI
+><P
+>you are probably already using other
+ services (such as telnet and ftp) which send plain text
+ passwords over the net, so sending them for SMB isn't
+ such a big deal.</P
+></LI
+></UL
+></DIV
+></DIV
+><DIV
+CLASS="SECT1"
+><H1
+CLASS="SECT1"
+><A
+NAME="AEN497">4.3. The smbpasswd Command</H1
+><P
+>The smbpasswd command maintains the two 32 byte password fields
+ in the smbpasswd file. If you wish to make it similar to the unix
+ <B
+CLASS="COMMAND"
+>passwd</B
+> or <B
+CLASS="COMMAND"
+>yppasswd</B
+> programs,
+ install it in <TT
+CLASS="FILENAME"
+>/usr/local/samba/bin/</TT
+> (or your
+ main Samba binary directory).</P
+><P
+><B
+CLASS="COMMAND"
+>smbpasswd</B
+> now works in a client-server mode
+ where it contacts the local smbd to change the user's password on its
+ behalf. This has enormous benefits - as follows.</P
+><P
+><B
+CLASS="COMMAND"
+>smbpasswd</B
+> now has the capability
+ to change passwords on Windows NT servers (this only works when
+ the request is sent to the NT Primary Domain Controller if you
+ are changing an NT Domain user's password).</P
+><P
+>To run smbpasswd as a normal user just type :</P
+><P
+><TT
+CLASS="PROMPT"
+>$ </TT
+><TT
+CLASS="USERINPUT"
+><B
+>smbpasswd</B
+></TT
+></P
+><P
+><TT
+CLASS="PROMPT"
+>Old SMB password: </TT
+><TT
+CLASS="USERINPUT"
+><B
+>&lt;type old value here -
+ or hit return if there was no old password&gt;</B
+></TT
+></P
+><P
+><TT
+CLASS="PROMPT"
+>New SMB Password: </TT
+><TT
+CLASS="USERINPUT"
+><B
+>&lt;type new value&gt;
+ </B
+></TT
+></P
+><P
+><TT
+CLASS="PROMPT"
+>Repeat New SMB Password: </TT
+><TT
+CLASS="USERINPUT"
+><B
+>&lt;re-type new value
+ </B
+></TT
+></P
+><P
+>If the old value does not match the current value stored for
+ that user, or the two new values do not match each other, then the
+ password will not be changed.</P
+><P
+>If invoked by an ordinary user it will only allow the user
+ to change his or her own Samba password.</P
+><P
+>If run by the root user smbpasswd may take an optional
+ argument, specifying the user name whose SMB password you wish to
+ change. Note that when run as root smbpasswd does not prompt for
+ or check the old password value, thus allowing root to set passwords
+ for users who have forgotten their passwords.</P
+><P
+><B
+CLASS="COMMAND"
+>smbpasswd</B
+> is designed to work in the same way
+ and be familiar to UNIX users who use the <B
+CLASS="COMMAND"
+>passwd</B
+> or
+ <B
+CLASS="COMMAND"
+>yppasswd</B
+> commands.</P
+><P
+>For more details on using <B
+CLASS="COMMAND"
+>smbpasswd</B
+> refer
+ to the man page which will always be the definitive reference.</P
+></DIV
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