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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter�2.�NetBIOS in a Unix World</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.64.1"><link rel="home" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt01.html" title="Part�I.�The protocol"><link rel="previous" href="netbios.html" title="Chapter�1.�Definition of NetBIOS Protocol and Name Resolution Modes"><link rel="next" href="ntdomain.html" title="Chapter�3.�NT Domain RPC's"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter�2.�NetBIOS in a Unix World</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="netbios.html">Prev</a>�</td><th width="60%" align="center">Part�I.�The protocol</th><td width="20%" align="right">�<a accesskey="n" href="ntdomain.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="unix-smb"></a>Chapter�2.�NetBIOS in a Unix World</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Andrew</span> <span class="surname">Tridgell</span></h3></div></div><div><p class="pubdate">April 1995</p></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="unix-smb.html#id2444583">Introduction</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2444604">Usernames</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506202">File Ownership</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506233">Passwords</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506270">Locking</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506322">Deny Modes</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506348">Trapdoor UIDs</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506368">Port numbers</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2506413">Protocol Complexity</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2444583"></a>Introduction</h2></div></div><div></div></div><p>

<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter�2.�NetBIOS in a Unix World</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.66.1"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt01.html" title="Part�I.�The protocol"><link rel="prev" href="netbios.html" title="Chapter�1.�Definition of NetBIOS Protocol and Name Resolution Modes"><link rel="next" href="ntdomain.html" title="Chapter�3.�NT Domain RPC's"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter�2.�NetBIOS in a Unix World</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="netbios.html">Prev</a>�</td><th width="60%" align="center">Part�I.�The protocol</th><td width="20%" align="right">�<a accesskey="n" href="ntdomain.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="unix-smb"></a>Chapter�2.�NetBIOS in a Unix World</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Andrew</span> <span class="surname">Tridgell</span></h3></div></div><div><p class="pubdate">April 1995</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="unix-smb.html#id2464982">Introduction</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2465002">Usernames</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2465061">File Ownership</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2465093">Passwords</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2465130">Locking</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2465183">Deny Modes</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2526290">Trapdoor UIDs</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2526311">Port numbers</a></span></dt><dt><span class="sect1"><a href="unix-smb.html#id2526356">Protocol Complexity</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2464982"></a>Introduction</h2></div></div></div><p>

This is a short document that describes some of the issues that

confront a SMB implementation on unix, and how Samba copes with

them. They may help people who are looking at unix<->PC

</p><p>

It was written to help out a person who was writing a paper on unix to

PC connectivity.

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2444604"></a>Usernames</h2></div></div><div></div></div><p>

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2465002"></a>Usernames</h2></div></div></div><p>

The SMB protocol has only a loose username concept. Early SMB

protocols (such as CORE and COREPLUS) have no username concept at

all. Even in later protocols clients often attempt operations

service%user syntax, the saving of session setup usernames for later

validation and the derivation of the username from the service name

(either directly or via the user= option).

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506202"></a>File Ownership</h2></div></div><div></div></div><p>

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2465061"></a>File Ownership</h2></div></div></div><p>

The commonly used SMB protocols have no way of saying "you can't do

that because you don't own the file". They have, in fact, no concept

of file ownership at all.

There are several possible solutions to this problem, including

username mapping, and forcing a specific username for particular

shares.

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506233"></a>Passwords</h2></div></div><div></div></div><p>

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2465093"></a>Passwords</h2></div></div></div><p>

Many SMB clients uppercase passwords before sending them. I have no

idea why they do this. Interestingly WfWg uppercases the password only

if the server is running a protocol greater than COREPLUS, so

smbpasswd file containing these password hashes is only readable

by the root user. See the documentation ENCRYPTION.txt for more

details.

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506270"></a>Locking</h2></div></div><div></div></div><p>

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2465130"></a>Locking</h2></div></div></div><p>

Since samba 2.2, samba supports other types of locking as well. This

section is outdated.

</p><p>

114

the same file, at which time the client will say if it is willing to

115

give up its lock. Unix has no simple way of implementing

116

opportunistic locking, and currently Samba has no support for it.

117

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506322"></a>Deny Modes</h2></div></div><div></div></div><p>

117

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2465183"></a>Deny Modes</h2></div></div></div><p>

118

When a SMB client opens a file it asks for a particular "deny mode" to

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be placed on the file. These modes (DENY_NONE, DENY_READ, DENY_WRITE,

120

DENY_ALL, DENY_FCB and DENY_DOS) specify what actions should be

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is clumsy and consumes processing and file resources,

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the shared memory implementation is vastly prefered and is turned on

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by default for those systems that support it.

131

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506348"></a>Trapdoor UIDs</h2></div></div><div></div></div><p>

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</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2526290"></a>Trapdoor UIDs</h2></div></div></div><p>

132

A SMB session can run with several uids on the one socket. This

133

happens when a user connects to two shares with different

134

usernames. To cope with this the unix server needs to switch uids

138

</p><p>

139

Note that you can also get the "trapdoor uid" message for other

140

reasons. Please see the FAQ for details.

141

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506368"></a>Port numbers</h2></div></div><div></div></div><p>

142

There is a convention that clients on sockets use high "unprivilaged"

143

port numbers (>1000) and connect to servers on low "privilaged" port

141

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2526311"></a>Port numbers</h2></div></div></div><p>

142

There is a convention that clients on sockets use high "unprivileged"

143

port numbers (>1000) and connect to servers on low "privilegedg" port

144

numbers. This is enforced in Unix as non-root users can't open a

145

socket for listening on port numbers less than 1000.

146

</p><p>

161

back, but it goes to port 137 which the unix user can't listen

162

on. Interestingly WinNT3.1 got this right - it sends node status

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responses back to the source port in the request.

164

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2506413"></a>Protocol Complexity</h2></div></div><div></div></div><p>

164

</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2526356"></a>Protocol Complexity</h2></div></div></div><p>

165

There are many "protocol levels" in the SMB protocol. It seems that

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each time new functionality was added to a Microsoft operating system,

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they added the equivalent functions in a new protocol level of the SMB

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