diff options
author | Andrew Bartlett <abartlet@samba.org> | 2014-06-03 20:20:08 +1200 |
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committer | Jeremy Allison <jra@samba.org> | 2014-06-03 21:24:45 +0200 |
commit | f9a9e18f15717e089e59cec86384a6fb9ecf1989 (patch) | |
tree | 018823ff24802b60db8a5aa7d056c76f9f3c8581 /docs-xml/Samba3-ByExample | |
parent | 05d78aa2058e6b62e7b27218a8ddea1f2c6b26dd (diff) | |
download | samba-f9a9e18f15717e089e59cec86384a6fb9ecf1989.tar.gz |
docs: Remove out of date Kerberos and security chapter
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Jun 3 21:24:45 CEST 2014 on sn-devel-104
Diffstat (limited to 'docs-xml/Samba3-ByExample')
-rw-r--r-- | docs-xml/Samba3-ByExample/SBE-KerberosFastStart.xml | 2073 | ||||
-rw-r--r-- | docs-xml/Samba3-ByExample/index.xml | 14 |
2 files changed, 6 insertions, 2081 deletions
diff --git a/docs-xml/Samba3-ByExample/SBE-KerberosFastStart.xml b/docs-xml/Samba3-ByExample/SBE-KerberosFastStart.xml deleted file mode 100644 index 3bc301c96dc..00000000000 --- a/docs-xml/Samba3-ByExample/SBE-KerberosFastStart.xml +++ /dev/null @@ -1,2073 +0,0 @@ -<?xml version="1.0" encoding="iso-8859-1"?> -<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc"> -<chapter id="kerberos"> - <title>Active Directory, Kerberos, and Security</title> - - <para><indexterm> - <primary>experiment</primary> - </indexterm> - By this point in the book, you have been exposed to many Samba features and capabilities. - More importantly, if you have implemented the examples given, you are well on your way to becoming - a Samba networking guru who knows a lot about Microsoft Windows. If you have taken the time to - practice, you likely have thought of improvements and scenarios with which you can experiment. You - are rather well plugged in to the many flexible ways Samba can be used. - </para> - - <para><indexterm> - <primary>criticism</primary> - </indexterm> - This is a book about Samba. Understandably, its intent is to present it in a positive light. - The casual observer might conclude that this book is one-eyed about Samba. It is &smbmdash; what - would you expect? This chapter exposes some criticisms that have been raised concerning - the use of Samba. For each criticism, there are good answers and appropriate solutions. - </para> - - <para> - Some criticism always comes from deep inside ranks that one would expect to be supportive of a particular - decision. Criticism can be expected from the outside. Let's see how the interesting dynamic of - criticism develops with respect to Abmas. - </para> - - <para><indexterm> - <primary>straw-man</primary> - </indexterm> - This chapter provides a shameless self-promotion of Samba. The objections raised were not pulled - out of thin air. They were drawn from comments made by Samba users and from criticism during - discussions with Windows network administrators. The tone of the objections reflects as closely - as possible that of the original. The case presented is a straw-man example that is designed to - permit each objection to be answered as it might occur in real life. - </para> - -<sect1> - <title>Introduction</title> - - <para><indexterm> - <primary>acquisitions</primary> - </indexterm><indexterm> - <primary>risk</primary> - </indexterm><indexterm> - <primary>assessment</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>Windows 2003 Serve</primary> - </indexterm> - Abmas is continuing its meteoric growth with yet further acquisitions. The investment community took - note of the spectacular projection of Abmas onto the global business stage. Abmas is building an - interesting portfolio of companies that includes accounting services, financial advice, investment - portfolio management, property insurance, risk assessment, and the recent addition of a a video rental - business. The pieces do not always appear to fit together, but Mr. Meany is certainly executing an - interesting business growth and development plan. Abmas Video Rentals was recently acquired. - During the time that the acquisition was closing, the Video Rentals business upgraded its Windows - NT4-based network to Windows 2003 Server and Active Directory. - </para> - - <para><indexterm> - <primary>Active Directory</primary> - </indexterm> - You have accepted the fact that Abmas Video Rentals will use Microsoft Active Directory. - The IT team, led by Stan Soroka, is committed to Samba and to maintaining a uniform technology platform. - Stan Soroka's team voiced its disapproval over the decision to permit this business to continue to - operate with a solution that is viewed by Christine and her group as <quote>an island of broken - technologies.</quote> This comment was made by one of Christine's staff as they were installing a new - Samba server at the new business. - </para> - - - <para><indexterm> - <primary>consultant</primary> - </indexterm><indexterm> - <primary>hypothetical</primary> - </indexterm> - Abmas Video Rentals' head of IT heard of this criticism. He was offended that a junior engineer - should make such a comment. He felt that he had to prepare in case he might be criticized for his - decision to use Active Directory. He decided he would defend his decision by hiring the services - of an outside security systems consultant to report<footnote><para>This report is entirely fictitious. - Any resemblance to a factual report is purely coincidental.</para></footnote> on his unit's operations - and to investigate the role of Samba at his site. Here are key extracts from this hypothetical - report: - </para> - - <blockquote><para><indexterm> - <primary>vulnerabilities</primary> - </indexterm><indexterm> - <primary>integrity</primary> - </indexterm><indexterm> - <primary>practices</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm> - ... the implementation of Microsoft Active Directory at the Abmas Video Rentals, Bamingsham site, - has been examined. We find no evidence to support a notion that vulnerabilities exist at your site. - ... we took additional steps to validate the integrity of the installation and operation of Active - Directory and are pleased that your staff are following sound practices. - </para> - - <para> - ... - </para> - - <para><indexterm> - <primary>accounts</primary> - <secondary>user</secondary> - </indexterm><indexterm> - <primary>accounts</primary> - <secondary>group</secondary> - </indexterm><indexterm> - <primary>Backup</primary> - </indexterm><indexterm> - <primary>disaster recovery</primary> - </indexterm><indexterm> - <primary>validated</primary> - </indexterm><indexterm> - <primary>off-site storage</primary> - </indexterm> - User and group accounts, and respective privileges, have been well thought out. File system shares are - appropriately secured. Backup and disaster recovery plans are well managed and validated regularly, and - effective off-site storage practices are considered to exceed industry norms. - </para> - - <para><indexterm> - <primary>compromise</primary> - </indexterm><indexterm> - <primary>secure</primary> - </indexterm><indexterm> - <primary>network</primary> - <secondary>secure</secondary> - </indexterm> - Your staff are justifiably concerned that the use of Samba may compromise their good efforts to maintain - a secure network. - </para> - - <para><indexterm> - <primary>winbind</primary> - </indexterm><indexterm> - <primary>security</primary> - </indexterm><indexterm> - <primary>secure</primary> - </indexterm><indexterm> - <primary>network</primary> - <secondary>management</secondary> - </indexterm> - The recently installed Linux file and application server uses a tool called <command>winbind</command> - that is indiscriminate about security. All user accounts in Active Directory can be used to access data - stored on the Linux system. We are alarmed that secure information is accessible to staff who should - not even be aware that it exists. We share the concerns of your network management staff who have gone - to great lengths to set fine-grained controls that limit information access to those who need access. - It seems incongruous to us that Samba winbind should be permitted to be used considering that it voids this fine work. - </para> - - <para><indexterm> - <primary>isolated</primary> - </indexterm><indexterm> - <primary>firewall</primary> - </indexterm><indexterm> - <primary>best practices</primary> - </indexterm> - Graham Judd [head of network administration] has locked down the security of all systems and is following - the latest Microsoft guidelines. ... null session connections have been disabled ... the internal network - is isolated from the outside world, the [product name removed] firewall is under current contract - maintenance support from [the manufacturer]. ... our attempts to penetrate security of your systems - failed to find problems common to Windows networking sites. We commend your staff on their attention to - detail and for following Microsoft recommended best practices. - </para> - - <para> - ... - </para> - - <para><indexterm> - <primary>security</primary> - </indexterm><indexterm> - <primary>disable</primary> - </indexterm><indexterm> - <primary>essential</primary> - </indexterm><indexterm> - <primary>trusted computing</primary> - </indexterm> - Regarding the use of Samba, we offer the following comments: Samba is in use in nearly half of - all sites we have surveyed. ... It is our opinion that Samba offers no better security than Microsoft - ... what worries us regarding Samba is the need to disable essential Windows security features such as - secure channel support, digital sign'n'seal on all communication traffic, and running Active Directory in - mixed mode so that Samba clients and servers can authenticate all of it. Additionally, we are concerned that - Samba is not at the full capabilities of Microsoft Windows NT4 server. Microsoft has moved well beyond that - with trusted computing initiatives that the Samba developers do not participate in. - </para> - - <para><indexterm> - <primary>integrity</primary> - </indexterm><indexterm> - <primary>hackers</primary> - </indexterm><indexterm> - <primary>accountable</primary> - </indexterm><indexterm> - <primary>flaws</primary> - </indexterm><indexterm> - <primary>updates</primary> - </indexterm><indexterm> - <primary>bug fixes</primary> - </indexterm><indexterm> - <primary>alarm</primary> - </indexterm> - One wonders about the integrity of an open source program that is developed by a team of hackers - who cannot be held accountable for the flaws in their code. The sheer number of updates and bug - fixes they have released should ring alarm bells in any business. - </para> - - <para><indexterm> - <primary>employment</primary> - </indexterm><indexterm> - <primary>jobs</primary> - </indexterm><indexterm> - <primary>risk</primary> - </indexterm> - Another factor that should be considered is that buying Microsoft products and services helps to - provide employment in the IT industry. Samba and Open Source software place those jobs at risk. - </para></blockquote> - - <para><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>independent expert</primary> - </indexterm> - This is also a challenge to rise above the trouble spot. You call Stan's team together for a simple - discussion, but it gets further out of hand. When you return to your office, you find the following - email in your in-box: - </para> - - <para> - Good afternoon, - </para> - - <blockquote><attribution>Stan</attribution><para> - I apologize for the leak of internal discussions to the new business. It reflects poorly on our - professionalism and has put you in an unpleasant position. I regret the incident. - </para> - - <para> - I also wish to advise that two of the recent recruits want to implement Kerberos authentication - across all systems. I concur with the desire to improve security. One of the new guys who is championing - the move to Kerberos was responsible for the comment that caused the embarrassment. - </para> - - <para><indexterm> - <primary>Kerberos</primary> - </indexterm><indexterm> - <primary>OpenLDAP</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>consultant</primary> - </indexterm> - I am experiencing difficulty in handling the sharp push for Kerberos. He claims that Kerberos, OpenLDAP, - plus Samba will seamlessly replace Microsoft Active Directory. I am a little out of my depth with respect - to the feasibility of such a move, but have taken steps to pull both of them into line. With your consent, - I would like to hire the services of a well-known Samba consultant to set the record straight. - </para> - - <para><indexterm> - <primary>criticism</primary> - </indexterm><indexterm> - <primary>policy</primary> - </indexterm><indexterm> - <primary>Windows Servers</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>budgetted</primary> - </indexterm><indexterm> - <primary>financial responsibility</primary> - </indexterm> - I intend to use this report to answer the criticism raised and would like to establish a policy that we - will approve the use of Microsoft Windows Servers (and Active Directory) subject to all costs being covered - out of the budget of the division that wishes to go its own way. I propose that dissenters will still remain - responsible to meet the budgeted contribution to IT operations as a whole. I believe we should not coerce - use of any centrally proposed standards, but make all noncompliance the financial responsibility of the - out-of-step division. Hopefully, this will encourage all divisions to walk with us and not alone. - </para></blockquote> - - <sect2> - <title>Assignment Tasks</title> - - <para> - You agreed with Stan's recommendations and hired a consultant to help defuse the powder - keg. The consultant's task is to provide a tractable answer to each of the issues raised. The consultant must be able - to support his or her claims, keep emotions to the side, and answer technically. - </para> - - </sect2> -</sect1> - -<sect1> - <title>Dissection and Discussion</title> - - <para><indexterm> - <primary>tool</primary> - </indexterm><indexterm> - <primary>benefit</primary> - </indexterm><indexterm> - <primary>choice</primary> - </indexterm><indexterm> - <primary>consultant</primary> - </indexterm><indexterm> - <primary>installation</primary> - </indexterm><indexterm> - <primary>income</primary> - </indexterm><indexterm> - <primary>employment</primary> - </indexterm> - Samba is a tool. No one is pounding your door to make you use Samba. That is a choice that you are free to - make or reject. It is likely that your decision to use Samba can greatly benefit your company. - The Samba Team obviously believes that the Samba software is a worthy choice. - If you hire a consultant to assist with the installation and/or deployment of Samba, or if you hire - someone to help manage your Samba installation, you can create income and employment. Alternately, - money saved by not spending in the IT area can be spent elsewhere in the business. All money saved - or spent creates employment. - </para> - - <para><indexterm> - <primary>economically sustainable</primary> - </indexterm><indexterm> - <primary>inter-operability</primary> - </indexterm><indexterm> - <primary>file and print service</primary> - </indexterm><indexterm> - <primary>cost</primary> - </indexterm><indexterm> - <primary>alternative</primary> - </indexterm> - In the long term, the use of Samba must be economically sustainable. In some situations, Samba is adopted - purely to provide file and print service interoperability on platforms that otherwise cannot provide - access to data and to printers for Microsoft Windows clients. Samba is used by some businesses to - effect a reduction in the cost of providing IT services. Obviously, it is also used by some as an - alternative to the use of a Microsoft file and print serving platforms with no consideration of costs. - </para> - - <para><indexterm> - <primary>documentation</primary> - </indexterm><indexterm> - <primary>responsibility</primary> - </indexterm><indexterm> - <primary>fix</primary> - </indexterm><indexterm> - <primary>broken</primary> - </indexterm> - It would be foolish to adopt a technology that might put any data or users at risk. Security affects - everyone. The Samba-Team is fully cognizant of the responsibility they have to their users. - The Samba documentation clearly reveals that full responsibility is accepted to fix anything - that is broken. - </para> - - <para><indexterm> - <primary>commercial</primary> - </indexterm><indexterm> - <primary>software</primary> - </indexterm><indexterm> - <primary>commercial software</primary> - </indexterm><indexterm> - <primary>End User License Agreement</primary> - <see>EULA</see> - </indexterm><indexterm> - <primary>accountable</primary> - </indexterm><indexterm> - <secondary>liability</secondary> - </indexterm><indexterm> - <primary>accepts liability</primary> - </indexterm><indexterm> - <primary>price paid</primary> - </indexterm><indexterm> - <primary>product defects</primary> - </indexterm><indexterm> - <primary>reimburse</primary> - </indexterm><indexterm> - <primary>extent</primary> - </indexterm> - There is a mistaken perception in the IT industry that commercial software providers are fully - accountable for the defects in products. Open Source software comes with no warranty, so it is - often assumed that its use confers a higher degree of risk. Everyone should read commercial software - End User License Agreements (EULAs). You should determine what real warranty is offered and the - extent of liability that is accepted. Doing so soon dispels the popular notion that - commercial software vendors are willingly accountable for product defects. In many cases, the - commercial vendor accepts liability only to reimburse the price paid for the software. - </para> - - <para><indexterm> - <primary>consumer</primary> - </indexterm><indexterm> - <primary>EULA</primary> - </indexterm><indexterm> - <primary>track record</primary> - </indexterm><indexterm> - <primary>commercial software</primary> - </indexterm><indexterm> - <primary>support</primary> - </indexterm><indexterm> - <primary>vendor</primary> - </indexterm> - The real issues that a consumer (like you) needs answered are What is the way of escape from technical - problems, and how long will it take? The average problem turnaround time in the Open Source community is - approximately 48 hours. What does the EULA offer? What is the track record in the commercial software - industry? What happens when your commercial vendor decides to cease providing support? - </para> - - <para><indexterm> - <primary>source code</primary> - </indexterm><indexterm> - <primary>Open Source</primary> - </indexterm><indexterm> - <primary>hire</primary> - </indexterm><indexterm> - <primary>programmer</primary> - </indexterm><indexterm> - <primary>solve</primary> - </indexterm><indexterm> - <primary>fix</primary> - </indexterm><indexterm> - <secondary>problem</secondary> - </indexterm> - Open Source software at least puts you in possession of the source code. This means that when - all else fails, you can hire a programmer to solve the problem. - </para> - - <sect2> - <title>Technical Issues</title> - - <para> - Each issue is now discussed and, where appropriate, example implementation steps are - provided. - </para> - - <variablelist> - <varlistentry> - <term>Winbind and Security</term> - <listitem><para><indexterm> - <primary>Winbind</primary> - </indexterm><indexterm> - <primary>Security</primary> - </indexterm><indexterm> - <primary>network</primary> - <secondary>administrators</secondary> - </indexterm><indexterm> - <primary>Domain users</primary> - </indexterm><indexterm> - <secondary>Domain account</secondary> - </indexterm><indexterm> - <primary>credentials</primary> - </indexterm><indexterm> - <primary>Network Neighborhood</primary> - </indexterm><indexterm> - <primary>UNIX/Linux server</primary> - </indexterm><indexterm> - <primary>browse</primary> - </indexterm><indexterm> - <primary>shares</primary> - </indexterm> - Windows network administrators may be dismayed to find that <command>winbind</command> - exposes all domain users so that they may use their domain account credentials to - log on to a UNIX/Linux system. The fact that all users in the domain can see the - UNIX/Linux server in their Network Neighborhood and can browse the shares on the - server seems to excite them further. - </para> - - <para><indexterm> - <primary>Domain Member server</primary> - </indexterm><indexterm> - <primary>familiar</primary> - </indexterm><indexterm> - <primary>fear</primary> - </indexterm><indexterm> - <primary>unknown</primary> - </indexterm> - <command>winbind</command> provides for the UNIX/Linux domain member server or - client, the same as one would obtain by adding a Microsoft Windows server or - client to the domain. The real objection is the fact that Samba is not MS Windows - and therefore requires handling a little differently from the familiar Windows systems. - One must recognize fear of the unknown. - </para> - - <para><indexterm> - <primary>network administrators</primary> - </indexterm><indexterm> - <primary>recognize</primary> - </indexterm><indexterm> - <primary>winbind</primary> - </indexterm><indexterm> - <primary>over-ride</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - <secondary>management tools</secondary> - </indexterm><indexterm> - <primary>fears</primary> - </indexterm> - Windows network administrators need to recognize that <command>winbind</command> does - not, and cannot, override account controls set using the Active Directory management - tools. The control is the same. Have no fear. - </para> - - <para><indexterm> - <primary>ADS Domain</primary> - </indexterm><indexterm> - <primary>account</primary> - <secondary>ADS Domain</secondary> - </indexterm><indexterm> - <primary>winbind</primary> - </indexterm><indexterm> - <primary>browsing</primary> - </indexterm><indexterm> - <primary>permits</primary> - </indexterm><indexterm> - <primary>access</primary> - </indexterm><indexterm> - <primary>drive mapping</primary> - </indexterm><indexterm> - <primary>protected</primary> - </indexterm><indexterm> - <primary>security controls</primary> - </indexterm><indexterm> - <primary>access controls</primary> - </indexterm> - Where Samba and the ADS domain account information obtained through the use of - <command>winbind</command> permits access, by browsing or by the drive mapping to - a share, to data that should be better protected. This can only happen when security - controls have not been properly implemented. Samba permits access controls to be set - on: - </para> - - <itemizedlist> - <listitem><para>Shares themselves (i.e., the logical share itself)</para></listitem> - <listitem><para>The share definition in &smb.conf;</para></listitem> - <listitem><para>The shared directories and files using UNIX permissions</para></listitem> - <listitem><para>Using Windows 2000 ACLs &smbmdash; if the file system is POSIX enabled</para></listitem> - </itemizedlist> - - <para> - Examples of each are given in <link linkend="ch10expl"/>. - </para> - </listitem> - </varlistentry> - - <varlistentry> - <term>User and Group Controls</term> - <listitem><para><indexterm> - <primary>User and Group Controls</primary> - </indexterm><indexterm> - <primary>management</primary> - <secondary>User</secondary> - </indexterm><indexterm> - <primary>management</primary> - <secondary>group</secondary> - </indexterm><indexterm> - <primary>ADS</primary> - </indexterm><indexterm> - <primary>permissions</primary> - </indexterm><indexterm> - <primary>privileges</primary> - </indexterm><indexterm> - <primary>flexibility</primary> - </indexterm><indexterm> - <primary>access controls</primary> - </indexterm><indexterm> - <primary>share definition</primary> - </indexterm> - User and group management facilities as known in the Windows ADS environment may be - used to provide equivalent access control constraints or to provide equivalent - permissions and privileges on Samba servers. Samba offers greater flexibility in the - use of user and group controls because it has additional layers of control compared to - Windows 200x/XP. For example, access controls on a Samba server may be set within - the share definition in a manner for which Windows has no equivalent. - </para> - - <para><indexterm> - <primary>analysis</primary> - </indexterm><indexterm> - <primary>system security</primary> - </indexterm><indexterm> - <primary>safe-guards</primary> - </indexterm><indexterm> - <primary>permissions</primary> - <secondary>excessive</secondary> - </indexterm><indexterm> - <primary>file system</primary> - </indexterm><indexterm> - <primary>shared resource</primary> - </indexterm><indexterm> - <primary>share definition</primary> - </indexterm> - In any serious analysis of system security, it is important to examine the safeguards - that remain when all other protective measures fail. An administrator may inadvertently - set excessive permissions on the file system of a shared resource, or he may set excessive - privileges on the share itself. If that were to happen in a Windows 2003 Server environment, - the data would indeed be laid bare to abuse. Yet, within a Samba share definition, it is - possible to guard against that by enforcing controls on the share definition itself. You - see a practical example of this a little later in this chapter. - </para> - - <para><indexterm> - <primary>diligence</primary> - </indexterm><indexterm> - <primary>weakness</primary> - </indexterm> - The report that is critical of Samba really ought to have exercised greater due - diligence: the real weakness is on the side of a Microsoft Windows environment. - </para></listitem> - </varlistentry> - - <varlistentry> - <term>Security Overall</term> - <listitem><para><indexterm> - <primary>defects</primary> - </indexterm> - Samba is designed in such a manner that weaknesses inherent in the design of - Microsoft Windows networking ought not to expose the underlying UNIX/Linux file - system in any way. All software has potential defects, and Samba is no exception. - What matters more is how defects that are discovered get dealt with. - </para> - - <para><indexterm> - <primary>security</primary> - </indexterm><indexterm> - <primary>protection</primary> - </indexterm><indexterm> - <primary>compromise</primary> - </indexterm><indexterm> - <primary>consequential risk</primary> - </indexterm> - The Samba Team totally agrees with the necessity to observe and fully implement - every security facility to provide a level of protection and security that is necessary - and that the end user (or network administrator) needs. Never would the Samba Team - recommend a compromise to system security, nor would deliberate defoliation of - security be publicly condoned; yet this is the practice by many Windows network - administrators just to make happy users who have no notion of consequential risk. - </para> - - <para><indexterm> - <primary>condemns</primary> - </indexterm><indexterm> - <primary>security fixes</primary> - </indexterm><indexterm> - <primary>updates</primary> - </indexterm><indexterm> - <primary>development</primary> - </indexterm><indexterm> - <primary>documentation</primary> - </indexterm><indexterm> - <primary>security updates</primary> - </indexterm><indexterm> - <primary>turn-around time</primary> - </indexterm> - The report condemns Samba for releasing updates and security fixes, yet Microsoft - online updates need to be applied almost weekly. The answer to the criticism - lies in the fact that Samba development is continuing, documentation is improving, - user needs are being increasingly met or exceeded, and security updates are issued - with a short turnaround time. - </para> - - <para><indexterm> - <primary>modularization</primary> - </indexterm><indexterm> - <primary>next generation</primary> - </indexterm><indexterm> - <primary>responsible</primary> - </indexterm><indexterm> - <primary>dependability</primary> - </indexterm><indexterm> - <primary>road-map</primary> - <secondary>published</secondary> - </indexterm> - The release of Samba-4 is expected around late 2004 to early 2005 and involves a near - complete rewrite to permit extensive modularization and to prepare Samba for new - functionality planned for addition during the next-generation series. The Samba Team - is responsible and can be depended upon; the history to date suggests a high - degree of dependability and on charter development consistent with published - roadmap projections. - </para> - - <para><indexterm> - <primary>foundation members</primary> - </indexterm><indexterm> - <primary>Common Internet File System</primary> - <see>CIFS</see> - </indexterm><indexterm> - <primary>network attached storage</primary> - <see>NAS</see> - </indexterm><indexterm> - <primary>conferences</primary> - </indexterm><indexterm> - <primary>presence and leadership</primary> - </indexterm><indexterm> - <primary>leadership</primary> - </indexterm><indexterm> - <primary>inter-operability</primary> - </indexterm> - Not well published is the fact that Microsoft was a foundation member of - the Common Internet File System (CIFS) initiative, together with the participation - of the network attached storage (NAS) industry. Unfortunately, for the past few years, - Microsoft has been absent from active involvement at CIFS conferences and has - not exercised the leadership expected of a major force in the networking technology - space. The Samba Team has maintained consistent presence and leadership at all - CIFS conferences and at the interoperability laboratories run concurrently with - them. - </para></listitem> - </varlistentry> - - <varlistentry> - <term>Cryptographic Controls (schannel, sign'n'seal)</term> - <listitem><para><indexterm> - <primary>Cryptographic</primary> - </indexterm><indexterm> - <primary>schannel</primary> - </indexterm><indexterm> - <primary>digital sign'n'seal</primary> - </indexterm> - The report correctly mentions that Samba did not support the most recent - <constant>schannel</constant> and <constant>digital sign'n'seal</constant> features - of Microsoft Windows NT/200x/XPPro products. This is one of the key features - of the Samba release. Market research reports take so long to generate that they are - seldom a reflection of current practice, and in many respects reports are like a - pathology report &smbmdash; they reflect accurately (at best) status at a snapshot in time. - Meanwhile, the world moves on. - </para> - - <para><indexterm> - <primary>public specifications</primary> - </indexterm><indexterm> - <primary>protocols</primary> - </indexterm><indexterm> - <primary>algorithm</primary> - </indexterm><indexterm> - <primary>compatible</primary> - </indexterm><indexterm> - <primary>network</primary> - <secondary>traffic</secondary> - <tertiary>observation</tertiary> - </indexterm><indexterm> - <primary>defensible standards</primary> - </indexterm><indexterm> - <primary>secure networking</primary> - </indexterm> - It should be pointed out that had clear public specifications for the protocols - been published, it would have been much easier to implement these features and would have - taken less time to do. The sole mechanism used to find an algorithm that is compatible - with the methods used by Microsoft has been based on observation of network traffic - and trial-and-error implementation of potential techniques. The real value of public - and defensible standards is obvious to all and would have enabled more secure networking - for everyone. - </para> - - <para><indexterm> - <primary>Critics</primary> - </indexterm><indexterm> - <primary>digital sign'n'seal</primary> - </indexterm> - Critics of Samba often ignore fundamental problems that may plague (or may have plagued) - the users of Microsoft's products also. Those who are first to criticize Samba - for not rushing into release of <constant>digital sign'n'seal</constant> support - often dismiss the problems that Microsoft has - <ulink url="http://support.microsoft.com/default.aspx?kbid=321733">acknowledged</ulink> - and for which a fix was provided. In fact, - <ulink url="http://www.tangent-systems.com/support/delayedwrite.html">Tangent Systems</ulink> - have documented a significant problem with delays writes that can be connected with the - implementation of sign'n'seal. They provide a work-around that is not trivial for many - Windows networking sites. From notes such as this it is clear that there are benefits - from not rushing new technology out of the door too soon. - </para> - - <para><indexterm> - <primary>secure networking protocols</primary> - </indexterm><indexterm> - <primary>refereed standards</primary> - </indexterm><indexterm> - <primary>proprietary</primary> - </indexterm><indexterm> - <primary>digital rights</primary> - </indexterm><indexterm> - <primary>protection</primary> - </indexterm><indexterm> - <primary>networking protocols</primary> - </indexterm><indexterm> - <primary>diffusion</primary> - </indexterm><indexterm> - <primary>consumer</primary> - </indexterm><indexterm> - <primary>choice</primary> - </indexterm> - One final comment is warranted. If companies want more secure networking protocols, - the most effective method by which this can be achieved is by users seeking - and working together to help define open and publicly refereed standards. The - development of closed source, proprietary methods that are developed in a - clandestine framework of secrecy, under claims of digital rights protection, does - not favor the diffusion of safe networking protocols and certainly does not - help the consumer to make a better choice. - </para></listitem> - </varlistentry> - - <varlistentry> - <term>Active Directory Replacement with Kerberos, LDAP, and Samba - <indexterm> - <primary>Active Directory</primary> - <secondary>Replacement</secondary> - </indexterm><indexterm> - <primary>Kerberos</primary> - </indexterm><indexterm> - <primary>LDAP</primary> - </indexterm><indexterm> - <primary>remote procedure call</primary> - <see>RPC</see> - </indexterm> - - </term> - <listitem><para> - <literallayout> </literallayout> - The Microsoft networking protocols extensively make use of remote procedure call (RPC) - technology. Active Directory is not a simple mixture of LDAP and Kerberos together - with file and print services, but rather is a complex, intertwined implementation - of them that uses RPCs that are not supported by any of these component technologies - and yet by which they are made to interoperate in ways that the components do not - support. - </para> - - <para><indexterm> - <primary>Active Directory</primary> - <secondary>Server</secondary> - </indexterm><indexterm> - <primary>OpenLDAP</primary> - </indexterm><indexterm> - <primary>Kerberos</primary> - </indexterm><indexterm> - <primary>project maintainers</primary> - </indexterm><indexterm> - <primary>LDAP</primary> - </indexterm> - In order to make the popular request for Samba to be an Active Directory Server a - reality, it is necessary to add to OpenLDAP, Kerberos, as well as Samba, RPC calls - that are not presently supported. The Samba Team has not been able to gain critical - overall support for all project maintainers to work together on the complex - challenge of developing and integrating the necessary technologies. Therefore, if - the Samba Team does not make it a priority to absorb Kerberos and LDAP functionality - into the Samba project, this dream request cannot become a reality. - </para> - - <para><indexterm> - <primary>missing RPC's</primary> - </indexterm><indexterm> - <primary>road-map</primary> - </indexterm><indexterm> - <primary>ADS</primary> - <secondary>server</secondary> - </indexterm><indexterm> - <primary>MMC</primary> - </indexterm><indexterm> - <primary>managed</primary> - </indexterm> - At this time, the integration of LDAP, Kerberos, and the missing RPCs is not on the - Samba development roadmap. If it is not on the published roadmap, it cannot be delivered - anytime soon. Ergo, ADS server support is not a current goal for Samba development. - The Samba Team is most committed to permitting Samba to be a full ADS domain member - that is increasingly capable of being managed using Microsoft Windows MMC tools. - </para></listitem> - </varlistentry> - </variablelist> - - <sect3> - <title>Kerberos Exposed</title> - - <para><indexterm> - <primary>kerberos</primary> - </indexterm><indexterm> - <primary>unauthorized activities</primary> - </indexterm><indexterm> - <primary>authorized location</primary> - </indexterm> - Kerberos is a network authentication protocol that provides secure authentication for - client-server applications by using secret-key cryptography. Firewalls are an insufficient - barrier mechanism in today's networking world; at best they only restrict incoming network - traffic but cannot prevent network traffic that comes from authorized locations from - performing unauthorized activities. - </para> - - <para><indexterm> - <primary>strong cryptography</primary> - </indexterm><indexterm> - <primary>identity</primary> - </indexterm><indexterm> - <primary>integrity</primary> - </indexterm> - Kerberos was created by MIT as a solution to network security problems. The Kerberos protocol uses - strong cryptography so that a client can prove its identity to a server (and vice versa) across an - insecure network connection. After a client and server has used Kerberos to prove their identity, - they can also encrypt all of their communications to assure privacy and data integrity as they go - about their business. - </para> - - <para><indexterm> - <primary>trusted third-party</primary> - </indexterm><indexterm> - <primary>principals</primary> - </indexterm><indexterm> - <primary>trusting</primary> - </indexterm><indexterm> - <primary>kerberos</primary> - <secondary>server</secondary> - </indexterm><indexterm> - <primary>secret</primary> - </indexterm> - Kerberos is a trusted third-party service. That means that there is a third party (the kerberos - server) that is trusted by all the entities on the network (users and services, usually called - principals). All principals share a secret password (or key) with the kerberos server and this - enables principals to verify that the messages from the kerberos server are authentic. Therefore, - trusting the kerberos server, users and services can authenticate each other. - </para> - - <para> - <indexterm><primary>restricted export</primary></indexterm> - <indexterm><primary>MIT Kerberos</primary></indexterm> - <indexterm><primary>Heimdal Kerberos</primary></indexterm> - Kerberos was, until recently, a technology that was restricted from being exported from the United States. - For many years that hindered global adoption of more secure networking technologies both within the United States - and abroad. A free and unencumbered implementation of MIT Kerberos has been produced in Europe - and is available from the <ulink url="http://www.pdc.kth.se/heimdal/">Royal Institute</ulink> of - Technology (KTH), Sweden. It is known as the Heimdal Kerberos project. In recent times the U.S. government - has removed sanctions affecting the global distribution of MIT Kerberos. It is likely that there will be a - significant surge forward in the development of Kerberos-enabled applications and in the general deployment - and use of Kerberos across the spectrum of the information technology industry. - </para> - - <para> - <indexterm><primary>Kerberos</primary><secondary>interoperability</secondary></indexterm> - A storm has broken out concerning interoperability between MIT Kerberos and Microsofts' implementation - of it. For example, a 2002 - <ulink url="http://www.idg.com.sg/idgwww.nsf/0/5DDA8D153A7505A748256BAB000D992A?OpenDocument">IDG</ulink> - report<footnote><para>Note: This link is no longer active. The same article is still - available from <ulink url="http://199.105.191.226/Man/2699/020430msdoj/">ITWorld.com</ulink> (July 5, 2005)</para></footnote> by - states: - </para> - - <blockquote><para> - A Microsoft Corp. executive testified at the software giant's remedy hearing that the company goes to - great lengths to disclose interfaces and protocols that allow third-party software products to interact - with Windows. But a lawyer with the states suing Microsoft pointed out that when it comes to the company's - use of the Kerberos authentication specification, not everyone agrees. - </para> - - <para> - <indexterm><primary>Kerberos</primary><secondary>unspecified fields</secondary></indexterm> - Robert Short, vice president of Windows core technology at Microsoft, wrote in his direct testimony prepared - before his appearance that non-Microsoft operating systems can disregard the portion of the Kerberos version - 5 specification that Windows clients use for proprietary purposes and still achieve interoperability with - the Microsoft OS. Microsoft takes advantage of unspecified fields in the Kerberos specification for storing - Windows-specific authorization data, Short wrote. The designers of Kerberos left these fields undefined so - that software developers could add their own authorization information, he said. - </para></blockquote> - - <para> - <indexterm><primary>DCE</primary></indexterm> - <indexterm><primary>RPC</primary></indexterm> - It so happens that Microsoft Windows clients depend on and expect the contents of the <emphasis>unspecified - fields</emphasis> in the Kerberos 5 communications data stream for their Windows interoperability, - particularly when Samba is expected to emulate a Windows Server 200x domain controller. But the interoperability - issue goes far deeper than this. In the domain control protocols that are used by MS Windows XP Professional, - there is a tight interdependency between the Kerberos protocols and the Microsoft distributed computing environment - (DCE) RPCs that themselves are an integral part of the SMB/CIFS protocols as used by - Microsoft. - </para> - - <para> - Microsoft makes the following comment in a reference in a - <ulink url="http://www.microsoft.com/technet/itsolutions/interop/mgmt/kerberos.asp"> - technet</ulink> article: - </para> - - <blockquote><para><indexterm> - <primary>Privilege Attribute Certificates</primary> - <see>PAC</see> - </indexterm><indexterm> - <primary>access control</primary> - </indexterm> - The DCE Security Services are also layered on the Kerberos protocol. DCE authentication services use RPC - representation of Kerberos protocol messages. In addition, DCE uses the authorization data field in Kerberos - tickets to convey Privilege Attribute Certificates (PACs) that define user identity and group membership. - The DCE PAC is used in a similar manner as Windows NT Security IDs for user authorization and access control. - Windows NT services will not be able to translate DCE PACs into Windows NT user and group identifiers. This - is not an issue with Kerberos interoperability, but rather an issue of interoperability between DCE and - Windows NT access control information. - </para></blockquote> - - </sect3> - - </sect2> - -</sect1> - -<sect1 id="ch10expl"> - <title>Implementation</title> - - <para> - The following procedures outline the implementation of the security measures discussed so far. - </para> - - <sect2> - <title>Share Access Controls</title> - - <para><indexterm> - <primary>Share Access Controls</primary> - </indexterm><indexterm> - <primary>filter</primary> - </indexterm><indexterm> - <primary>connection</primary> - </indexterm> - Access control entries placed on the share itself act as a filter at the time a when CIFS/SMB client (such as - Windows XP Pro) attempts to make a connection to the Samba server. - </para> - - <procedure> - <title>Create/Edit/Delete Share ACLs</title> - <step><para><indexterm> - <primary>Domain Administrator</primary> - </indexterm><indexterm> - <primary>account</primary> - </indexterm> - From a Windows 200x/XP Professional workstation, log on to the domain using the Domain Administrator - account (on Samba domains, this is usually the account called <constant>root</constant>). - </para></step> - - <step><para> - Click - <menuchoice> - <guimenu>Start</guimenu> - <guimenuitem>Settings</guimenuitem> - <guimenuitem>Control Panel</guimenuitem> - <guimenuitem>Administrative Tools</guimenuitem> - <guimenuitem>Computer Management</guimenuitem> - </menuchoice>. - </para></step> - - <step><para> - In the left panel, - <menuchoice> - <guimenu>[Right mouse menu item] Computer Management (Local)</guimenu> - <guimenuitem>Connect to another computer ...</guimenuitem> - <guimenuitem>Browse...</guimenuitem> - <guimenuitem>Advanced</guimenuitem> - <guimenuitem>Find Now</guimenuitem> - </menuchoice>. In the lower panel, click on the name of the server you wish to - administer. Click <menuchoice> - <guimenu>OK</guimenu> - <guimenuitem>OK</guimenuitem> - <guimenuitem>OK</guimenuitem> - </menuchoice>.<indexterm> - <primary>Computer Management</primary> - </indexterm> - In the left panel, the entry <guimenu>Computer Management (Local)</guimenu> should now reflect - the change made. For example, if the server you are administering is called <constant>FRODO</constant>, - the Computer Management entry should now say <guimenu>Computer Management (FRODO)</guimenu>. - </para></step> - - <step><para> - In the left panel, click <menuchoice> - <guimenu>Computer Management (FRODO)</guimenu> - <guimenuitem>[+] Shared Folders</guimenuitem> - <guimenuitem>Shares</guimenuitem> - </menuchoice>. - </para></step> - - <step><para><indexterm> - <primary>ACLs</primary> - </indexterm><indexterm> - <primary>Share Permissions</primary> - </indexterm> - In the right panel, double-click on the share on which you wish to set/edit ACLs. This - will bring up the Properties panel. Click the <guimenu>Share Permissions</guimenu> tab. - </para></step> - - <step><para><indexterm> - <primary>access control settings</primary> - </indexterm><indexterm> - <primary>Everyone</primary> - </indexterm><indexterm> - <primary>full control</primary> - </indexterm><indexterm> - <primary>over-rule</primary> - </indexterm><indexterm> - <primary>permissions</primary> - </indexterm><indexterm> - <primary>rejected</primary> - </indexterm> - You may now edit/add/remove access control settings. Be very careful. Many problems have been - created by people who decided that everyone should be rejected but one particular group should - have full control. This is a catch-22 situation because members of that particular group also - belong to the group <constant>Everyone</constant>, which therefore overrules any permissions - set for the permitted group. - </para></step> - - <step><para> - When you are done with editing, close all panels by clicking through the <guimenu>OK</guimenu> - buttons. - </para></step> - </procedure> - - </sect2> - - <sect2> - <title>Share Definition Controls</title> - - <para><indexterm> - <primary>Share Definition</primary> - <secondary>Controls</secondary> - </indexterm><indexterm> - <primary>check-point</primary> - </indexterm><indexterm> - <primary>pile-driver</primary> - </indexterm><indexterm> - <primary>credential</primary> - </indexterm><indexterm> - <primary>powers</primary> - </indexterm><indexterm> - <primary>privileges</primary> - </indexterm> - Share-definition-based access controls can be used like a checkpoint or like a pile-driver. Just as a - checkpoint can be used to require someone who wants to get through to meet certain requirements, so - it is possible to require the user (or group the user belongs to) to meet specified credential-related - objectives. It can be likened to a pile-driver by overriding default controls in that having met the - credential-related objectives, the user can be granted powers and privileges that would not normally be - available under default settings. - </para> - - <para><indexterm> - <primary>access controls</primary> - </indexterm><indexterm> - <primary>ACLs</primary> - </indexterm><indexterm> - <primary>share definition controls</primary> - </indexterm><indexterm> - <primary>hierarchy of control</primary> - </indexterm> - It must be emphasized that the controls discussed here can act as a filter or give rights of passage - that act as a superstructure over normal directory and file access controls. However, share-level - ACLs act at a higher level than do share definition controls because the user must filter through the - share-level controls to get to the share-definition controls. The proper hierarchy of controls implemented - by Samba and Windows networking consists of: - </para> - - <orderedlist> - <listitem><para>Share-level ACLs</para></listitem> - <listitem><para>Share-definition controls</para></listitem> - <listitem><para>Directory and file permissions</para></listitem> - <listitem><para>Directory and file POSIX ACLs</para></listitem> - </orderedlist> - - <sect3> - <title>Checkpoint Controls</title> - - <para><indexterm> - <primary>Checkpoint Controls</primary> - </indexterm> - Consider the following extract from a &smb.conf; file defining the share called <constant>Apps</constant>: -<screen> -[Apps] - comment = Application Share - path = /data/apps - read only = Yes - valid users = @Employees -</screen> - This definition permits only those who are members of the group called <constant>Employees</constant> to - access the share. - </para> - - <note><para><indexterm> - <primary>Domain Member</primary> - <secondary>servers</secondary> - </indexterm><indexterm> - <primary>winbind use default domain</primary> - </indexterm><indexterm> - <primary>fully qualified</primary> - </indexterm><indexterm> - <primary>valid users</primary> - </indexterm><indexterm> - <primary>delimiter</primary> - </indexterm> - On domain member servers and clients, even when the <parameter>winbind use default domain</parameter> has - been specified, the use of domain accounts in security controls requires fully qualified domain specification, - for example, <smbconfoption name="valid users">@"MEGANET\Northern Engineers"</smbconfoption>. - Note the necessity to use the double quotes to avoid having the space in the Windows group name interpreted as a - delimiter. - </para></note> - - <para><indexterm> - <primary>ACL</primary> - </indexterm><indexterm> - <primary>access</primary> - </indexterm><indexterm> - <primary>validate</primary> - </indexterm> - If there is an ACL on the share itself to permit read/write access for all <constant>Employees</constant> - as well as read/write for the group <constant>Doctors</constant>, both groups are permitted through - to the share. However, at the moment an attempt is made to set up a connection to the share, a member of - the group <constant>Doctors</constant>, who is not also a member of the group <constant>Employees</constant>, - would immediately fail to validate. - </para> - - <para><indexterm> - <primary>share definition controls</primary> - </indexterm> - Consider another example. In this case, you want to permit all members of the group <constant>Employees</constant> - except the user <constant>patrickj</constant> to access the <constant>Apps</constant> share. This can be - easily achieved by setting a share-level ACL permitting only <constant>Employees</constant> to access the share, - and then in the share definition controls excluding just <constant>patrickj</constant>. Here is how that might - be done: -<screen> -[Apps] - comment = Application Share - path = /data/apps - read only = Yes - invalid users = patrickj -</screen> - <indexterm> - <primary>permissions</primary> - </indexterm> - Let us assume that you want to permit the user <constant>gbshaw</constant> to manage any file in the - UNIX/Linux file system directory <filename>/data/apps</filename>, but you do not want to grant any write - permissions beyond that directory tree. Here is one way this can be done: -<screen> -[Apps] - comment = Application Share - path = /data/apps - read only = Yes - invalid users = patrickj - admin users = gbshaw -</screen> - <indexterm> - <primary>administrative rights</primary> - </indexterm> - Now we have a set of controls that permits only <constant>Employees</constant> who are also members of - the group <constant>Doctors</constant>, excluding the user <constant>patrickj</constant>, to have - read-only privilege, but the user <constant>gbshaw</constant> is granted administrative rights. - The administrative rights conferred upon the user <constant>gbshaw</constant> permit operation as - if that user has logged in as the user <constant>root</constant> on the UNIX/Linux system and thus, - for access to the directory tree that has been shared (exported), permit the user to override controls - that apply to all other users on that resource. - </para> - - <para> - There are additional checkpoint controls that may be used. For example, if for the same share we now - want to provide the user <constant>peters</constant> with the ability to write to one directory to - which he has write privilege in the UNIX file system, you can specifically permit that with the - following settings: -<screen> -[Apps] - comment = Application Share - path = /data/apps - read only = Yes - invalid users = patrickj - admin users = gbshaw - write list = peters -</screen> - <indexterm> - <primary>check-point controls</primary> - </indexterm> - This is a particularly complex example at this point, but it begins to demonstrate the possibilities. - You should refer to the online manual page for the &smb.conf; file for more information regarding - the checkpoint controls that Samba implements. - </para> - - </sect3> - - <sect3> - <title>Override Controls</title> - - <para><indexterm> - <primary>over-ride controls</primary> - </indexterm> - Override controls implemented by Samba permit actions like the adoption of a different identity - during file system operations, the forced overwriting of normal file and directory permissions, - and so on. You should refer to the online manual page for the &smb.conf; file for more information regarding - the override controls that Samba implements. - </para> - - <para> - In the following example, you want to create a Windows networking share that any user can access. - However, you want all read and write operations to be performed as if the user <constant>billc</constant> - and member of the group <constant>Mentors</constant> read/write the files. Here is one way this - can be done: -<screen> -[someshare] - comment = Some Files Everyone May Overwrite - path = /data/somestuff - read only = No - force user = billc - force group = Mentors -</screen> - <indexterm> - <primary>forced settings</primary> - </indexterm><indexterm> - <primary>overheads</primary> - </indexterm> - That is all there is to it. Well, it is almost that simple. The downside of this method is that - users are logged onto the Windows client as themselves, and then immediately before accessing the - file, Samba makes system calls to change the effective user and group to the forced settings - specified, completes the file transaction, and then reverts to the actually logged-on identity. - This imposes significant overhead on Samba. The alternative way to effectively achieve the same result - (but with lower system CPU overheads) is described next. - </para> - - <para><indexterm> - <primary>force user</primary> - </indexterm><indexterm> - <primary>force group</primary> - </indexterm><indexterm> - <primary>opportunistic</primary> - <secondary>locking</secondary> - </indexterm><indexterm> - <primary>oplock break</primary> - </indexterm><indexterm> - <primary>performance degradation</primary> - </indexterm> - The use of the <parameter>force user</parameter> or the <parameter>force group</parameter> may - also have a severe impact on system (particularly on Windows client) performance. If opportunistic - locking is enabled on the share (the default), it causes an <constant>oplock break</constant> to be - sent to the client even if the client has not opened the file. On networks that have high traffic - density, or on links that are routed to a remote network segment, <constant>oplock breaks</constant> - can be lost. This results in possible retransmission of the request, or the client may time-out while - waiting for the file system transaction (read or write) to complete. The result can be a profound - apparent performance degradation as the client continually attempts to reconnect to overcome the - effect of the lost <constant>oplock break</constant>, or time-out. - </para> - - </sect3> - - </sect2> - - <sect2> - <title>Share Point Directory and File Permissions</title> - - <para><indexterm> - <primary>security</primary> - </indexterm><indexterm> - <primary>privilege controls</primary> - </indexterm><indexterm> - <primary>permission</primary> - </indexterm><indexterm> - <primary>share definition controls</primary> - </indexterm> - Samba has been designed and implemented so that it respects as far as is feasible the security and - user privilege controls that are built into the UNIX/Linux operating system. Samba does nothing - with respect to file system access that violates file system permission settings, unless it is - explicitly instructed to do otherwise through share definition controls. Given that Samba obeys - UNIX file system controls, this chapter does not document simple information that can be obtained - from a basic UNIX training guide. Instead, one common example of a typical problem is used - to demonstrate the most effective solution referred to in the immediately preceding paragraph. - </para> - - <para><indexterm> - <primary>Microsoft Office</primary> - </indexterm><indexterm> - <primary>Word</primary> - </indexterm><indexterm> - <primary>Excel</primary> - </indexterm> - One of the common issues that repeatedly pops up on the Samba mailing lists involves the saving of - Microsoft Office files (Word and Excel) to a network drive. Here is the typical sequence: - </para> - - <orderedlist> - <listitem><para> - A user opens a Word document from a network drive. The file was owned by user <constant>janetp</constant> - and <constant>users</constant>, and was set read/write-enabled for everyone. - </para></listitem> - - <listitem><para> - File changes and edits are made. - </para></listitem> - - <listitem><para> - The file is saved, and MS Word is closed. - </para></listitem> - - <listitem><para> - The file is now owned by the user <constant>billc</constant> and group <constant>doctors</constant>, - and is set read/write by <constant>billc</constant>, read-only by <constant>doctors</constant>, and - no access by everyone. - </para></listitem> - - <listitem><para> - The original owner cannot now access her own file and is <quote>justifiably</quote> upset. - </para></listitem> - </orderedlist> - - <para> - There have been many postings over the years that report the same basic problem. Frequently Samba users - want to know when this <quote>bug</quote> will be fixed. The fact is, this is not a bug in Samba at all. - Here is the real sequence of what happens in this case. - </para> - - <para><indexterm> - <primary>MS Word</primary> - </indexterm><indexterm> - <primary>ownership</primary> - </indexterm><indexterm> - <primary>permissions</primary> - </indexterm> - When the user saves a file, MS Word creates a new (temporary) file. This file is naturally owned - by the user who creates the file (<constant>billc</constant>) and has the permissions that follow - that user's default settings within the operating system (UNIX/Linux). When MS Word has finished writing - the file to disk, it then renames the new (temporary) file to the name of the old one. MS Word does not - change the ownership or permissions to what they were on the original file. The file is thus a totally - new file, and the old one has been deleted in the process. - </para> - - <para> - Samba received a request to create a new file, and then to rename the file to a new name. The old file that - has the same name is now automatically deleted. Samba has no way of knowing that the new file should - perhaps have the same ownership and permissions as the old file. To Samba, these are entirely independent - operations. - </para> - - <para> - The question is, <quote>How can we solve the problem?</quote> - </para> - - <para> - The solution is simple. Use UNIX file system permissions and controls to your advantage. Follow these - simple steps to create a share in which all files will consistently be owned by the same user and the - same group: - </para> - - - <procedure> - <title>Using Directory Permissions to Force File User and Group Ownership</title> - <step><para> - Change your share definition so that it matches this pattern: -<screen> -[finance] - path = /usr/data/finance - browseable = Yes - read only = No -</screen> - </para></step> - - <step><para><indexterm> - <primary>permissions</primary> - <secondary>user</secondary> - </indexterm><indexterm> - <primary>permissions</primary> - <secondary>group</secondary> - </indexterm> - Set consistent user and group permissions recursively down the directory tree as shown here: -<screen> -&rootprompt; chown -R janetp.users /usr/data/finance -</screen> - </para></step> - - <step><para><indexterm> - <primary>accessible</primary> - </indexterm> - Set the files and directory permissions to be read/write for owner and group, and not accessible - to others (everyone), using the following command: -<screen> -&rootprompt; chmod ug+rwx,o-rwx /usr/data/finance -</screen> - </para></step> - - <step><para><indexterm> - <primary>SGID</primary> - </indexterm> - Set the SGID (supergroup) bit on all directories from the top down. This means all files - can be created with the permissions of the group set on the directory. It means all users - who are members of the group <constant>finance</constant> can read and write all files in - the directory. The directory is not readable or writable by anyone who is not in the - <constant>finance</constant> group. Simply follow this example: -<screen> -&rootprompt; find /usr/data/finance -type d -exec chmod ug+s {}\; -</screen> - - </para></step> - - <step><para><indexterm> - <primary>group membership</primary> - </indexterm><indexterm> - <primary>primary group</primary> - </indexterm><indexterm> - <primary>/etc/passwd</primary> - </indexterm> - Make sure all users that must have read/write access to the directory have - <constant>finance</constant> group membership as their primary group, - for example, the group they belong to in <filename>/etc/passwd</filename>. - </para></step> - </procedure> - - </sect2> - - <sect2> - <title>Managing Windows 200x ACLs</title> - - <para><indexterm> - <primary>translate</primary> - </indexterm><indexterm> - <primary>Windows 2000 ACLs</primary> - </indexterm><indexterm> - <primary>Posix ACLs</primary> - </indexterm><indexterm> - <primary>side effects</primary> - </indexterm> - Samba must translate Windows 2000 ACLs to UNIX POSIX ACLs. This has some interesting side effects because - there is not a one-to-one equivalence between them. The as-close-as-possible ACLs match means - that some transactions are not possible from MS Windows clients. One of these is to reset the ownership - of directories and files. If you want to reset ownership, this must be done from a UNIX/Linux login. - </para> - - <para> - There are two possible ways to set ACLs on UNIX/Linux file systems from a Windows network workstation, - either via File Manager or via the Microsoft Management Console (MMC) Computer Management interface. - </para> - - <sect3> - <title>Using the MMC Computer Management Interface</title> - - <procedure> - <step><para> - From a Windows 200x/XP Professional workstation, log on to the domain using the Domain Administrator - account (on Samba domains, this is usually the account called <constant>root</constant>). - </para></step> - - <step><para> - Click - <menuchoice> - <guimenu>Start</guimenu> - <guimenuitem>Settings</guimenuitem> - <guimenuitem>Control Panel</guimenuitem> - <guimenuitem>Administrative Tools</guimenuitem> - <guimenuitem>Computer Management</guimenuitem> - </menuchoice>. - </para></step> - - <step><para> - In the left panel, - <menuchoice> - <guimenu>[Right mouse menu item] Computer Management (Local)</guimenu> - <guimenuitem>Connect to another computer ...</guimenuitem> - <guimenuitem>Browse...</guimenuitem> - <guimenuitem>Advanced</guimenuitem> - <guimenuitem>Find Now</guimenuitem> - </menuchoice>. In the lower panel, click on the name of the server you wish to - administer. Click <menuchoice> - <guimenu>OK</guimenu> - <guimenuitem>OK</guimenuitem> - <guimenuitem>OK</guimenuitem> - </menuchoice>. - In the left panel, the entry <guimenu>Computer Management (Local)</guimenu> should now reflect - the change made. For example, if the server you are administering is called <constant>FRODO</constant>, - the Computer Management entry should now say: <guimenu>Computer Management (FRODO)</guimenu>. - </para></step> - - <step><para> - In the left panel, click <menuchoice> - <guimenu>Computer Management (FRODO)</guimenu> - <guimenuitem>[+] Shared Folders</guimenuitem> - <guimenuitem>Shares</guimenuitem> - </menuchoice>. - </para></step> - - <step><para><indexterm> - <primary>Security</primary> - </indexterm><indexterm> - <primary>Properties</primary> - </indexterm><indexterm> - <primary>Permissions</primary> - </indexterm><indexterm> - <primary>Samba Domain server</primary> - </indexterm> - In the right panel, double-click on the share on which you wish to set/edit ACLs. This - brings up the Properties panel. Click the <guimenu>Security</guimenu> tab. It is best - to edit ACLs using the <constant>Advanced</constant> editing features. Click the - <guimenu>Advanced</guimenu> button. This opens a panel that has four tabs. Only the - functionality under the <constant>Permissions</constant> tab can be utilized with respect - to a Samba domain server. - </para></step> - - <step><para><indexterm> - <primary>access control</primary> - </indexterm><indexterm> - <primary>permitted group</primary> - </indexterm> - You may now edit/add/remove access control settings. Be very careful. Many problems have been - created by people who decided that everyone should be rejected but one particular group should - have full control. This is a catch-22 situation because members of that particular group also - belong to the group <constant>Everyone</constant>, which therefore overrules any permissions - set for the permitted group. - </para></step> - - <step><para> - When you are done with editing, close all panels by clicking through the <guimenu>OK</guimenu> - buttons until the last panel closes. - </para></step> - </procedure> - - </sect3> - - <sect3> - <title>Using MS Windows Explorer (File Manager)</title> - - <para> - The following alternative method may be used from a Windows workstation. In this example we work - with a domain called <constant>MEGANET</constant>, a server called <constant>MASSIVE</constant>, and a - share called <constant>Apps</constant>. The underlying UNIX/Linux share point for this share is - <filename>/data/apps</filename>. - </para> - - <procedure> - <step><para> - Click <menuchoice> - <guimenu>Start</guimenu> - <guimenuitem>[right-click] My Computer</guimenuitem> - <guimenuitem>Explore</guimenuitem> - <guimenuitem>[left panel] [+] My Network Places</guimenuitem> - <guimenuitem>[+] Entire Network</guimenuitem> - <guimenuitem>[+] Microsoft Windows Network</guimenuitem> - <guimenuitem>[+] Meganet</guimenuitem> - <guimenuitem>[+] Massive</guimenuitem> - <guimenuitem>[right-click] Apps</guimenuitem> - <guimenuitem>Properties</guimenuitem> - <guimenuitem>Security</guimenuitem> - <guimenuitem>Advanced</guimenuitem> - </menuchoice>. This opens a panel that has four tabs. Only the functionality under the - <constant>Permissions</constant> tab can be utilized for a Samba domain server. - </para></step> - - <step><para><indexterm> - <primary>full control</primary> - </indexterm><indexterm> - <primary>over-rule</primary> - </indexterm> - You may now edit/add/remove access control settings. Be very careful. Many problems have been - created by people who decided that everyone should be rejected but one particular group should - have full control. This is a catch-22 situation because members of that particular group also - belong to the group <constant>Everyone</constant>, which therefore overrules any permissions - set for the permitted group. - </para></step> - - <step><para> - When you are done with editing, close all panels by clicking through the <guimenu>OK</guimenu> - buttons until the last panel closes. - </para></step> - </procedure> - - </sect3> - - <sect3> - <title>Setting Posix ACLs in UNIX/Linux</title> - - <para><indexterm> - <primary>desired security setting</primary> - </indexterm><indexterm> - <primary>shared resource</primary> - </indexterm> - Yet another alternative method for setting desired security settings on the shared resource files and - directories can be achieved by logging into UNIX/Linux and setting POSIX ACLs directly using command-line - tools. Here is an example session on the same resource as in the immediately preceding example on a SUSE 9 - Linux system: - </para> - - <procedure> - <step><para> - Log into the Linux system as the user <constant>root</constant>. - </para></step> - - <step><para> - Change directory to the location of the exported (shared) Windows file share (Apps), which is in - the directory <filename>/data</filename>. Execute the following: -<screen> -&rootprompt; cd /data -</screen> - Retrieve the existing POSIX ACLs entry by executing: -<screen> -&rootprompt; getfacl apps -# file: apps -# owner: root -# group: root -user::rwx -group::rwx -other::r-x -</screen> - </para></step> - - <step><para><indexterm> - <primary>recursively</primary> - </indexterm> - You want to add permission for <constant>AppsMgrs</constant> to enable them to - manage the applications (apps) share. It is important to set the ACL recursively - so that the AppsMgrs have this capability throughout the directory tree that is - being shared. This is done using the <constant>-R</constant> option as shown. - Execute the following: -<screen> -&rootprompt; setfacl -m -R group:AppsMgrs:rwx /data/apps -</screen> - Because setting an ACL does not provide a response, you immediately validate the command executed - as follows: -<screen> -&rootprompt; getfacl /data/apps -# file: apps -# owner: root -# group: root -user::rwx -group::rwx -group:AppsMgrs:rwx -mask::rwx -other::r-x -</screen> - This confirms that the change of POSIX ACL permissions has been effective. - </para></step> - - <step><para><indexterm> - <primary>setfacl</primary> - </indexterm><indexterm> - <primary>getfacl</primary> - </indexterm><indexterm> - <primary>directory tree</primary> - </indexterm><indexterm> - <primary>Windows ACLs</primary> - </indexterm><indexterm> - <primary>inheritance</primary> - </indexterm> - It is highly recommended that you read the online manual page for the <command>setfacl</command> - and <command>getfacl</command> commands. This provides information regarding how to set/read the default - ACLs and how that may be propagated through the directory tree. In Windows ACLs terms, this is the equivalent - of setting <constant>inheritance</constant> properties. - </para></step> - </procedure> - - </sect3> - - </sect2> - - <sect2> - <title>Key Points Learned</title> - - <para> - The mish-mash of issues were thrown together into one chapter because it seemed like a good idea. - Looking back, this chapter could be broken into two, but it's too late now. It has been done. - The highlights covered are as follows: - </para> - - <itemizedlist> - <listitem><para><indexterm> - <primary>Winbind</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>password change</primary> - </indexterm><indexterm> - <primary>logon hours</primary> - </indexterm> - Winbind honors and does not override account controls set in Active Directory. - This means that password change, logon hours, and so on, are (or soon will be) enforced - by Samba winbind. At this time, an out-of-hours login is denied and password - change is enforced. At this time, if logon hours expire, the user is not forcibly - logged off. That may be implemented at some later date. - </para></listitem> - - <listitem><para><indexterm> - <primary>Sign'n'seal</primary> - </indexterm><indexterm> - <primary>schannel</primary> - </indexterm> - Sign'n'seal (plus schannel support) has been implemented in Samba. Beware of potential - problems acknowledged by Microsoft as having been fixed but reported by some as still - possibly an open issue. - </para></listitem> - - <listitem><para><indexterm> - <primary>Kerberos</primary> - </indexterm><indexterm> - <primary>OpenLDAP</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>inter-operability</primary> - </indexterm> - The combination of Kerberos 5, plus OpenLDAP, plus Samba, cannot replace Microsoft - Active Directory. The possibility to do this is not planned in the current Samba - roadmap. Samba does aim to provide further improvements in interoperability so that - UNIX/Linux systems may be fully integrated into Active Directory domains. - </para></listitem> - - <listitem><para> - This chapter reviewed mechanisms by which Samba servers may be kept secure. Each of - the four key methodologies was reviewed with specific reference to example deployment - techniques. - </para></listitem> - </itemizedlist> - - </sect2> - -</sect1> - -<sect1> - <title>Questions and Answers</title> - - <para> - </para> - - <qandaset defaultlabel="chap10qa" type="number"> - <qandaentry> - <question> - - <para><indexterm> - <primary>Sign'n'seal</primary> - </indexterm><indexterm> - <primary>registry hacks</primary> - </indexterm> - Does Samba-3 require the <constant>Sign'n'seal</constant> registry hacks needed by Samba-2? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>schannel</primary> - </indexterm><indexterm> - <primary>Sign'n'seal</primary> - </indexterm><indexterm> - <primary>registry change</primary> - </indexterm> - No. Samba fully supports <constant>Sign'n'seal</constant> as well as <constant>schannel</constant> - operation. The registry change should not be applied when Samba is used as a domain controller. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para> - Does Samba support Active Directory? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>Active Directory</primary> - </indexterm> - Yes. Samba can be a fully participating native mode Active Directory client. Samba-3 does not - provide Active Directory services. It cannot be used to replace a Microsoft Active Directory - server implementation. Samba can function as an Active Directory client (workstation) toolkit, - and it can function as an Active Directory domain member server. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>mixed-mode</primary> - </indexterm> - When Samba is used with Active Directory, is it necessary to run mixed-mode operation, as was - necessary with Samba-2? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>native</primary> - </indexterm> - No. Samba can be used with NetBIOS over TCP/IP disabled, just as can be done with Windows 200x - Server and 200x/XPPro client products. It is no longer necessary to run mixed-mode operation, - because Samba can join a native Windows 2003 Server ADS domain. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>share level access controls</primary> - </indexterm> - Is it safe to set share-level access controls in Samba? - </para> - - </question> - <answer> - - <para> - Yes. Share-level access controls have been supported since early versions of Samba-2. This is - very mature technology. Not enough sites make use of this powerful capability, neither on - Windows server or with Samba servers. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>share ACLs</primary> - </indexterm> - Is it mandatory to set share ACLs to get a secure Samba server? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>file system security</primary> - </indexterm><indexterm> - <primary>Windows 200x ACLs</primary> - </indexterm><indexterm> - <primary>share definition controls</primary> - </indexterm><indexterm> - <primary>share level ACL</primary> - </indexterm><indexterm> - <primary>security</primary> - </indexterm> - No. Samba honors UNIX/Linux file system security, supports Windows 200x ACLs, and provides - means of securing shares through share definition controls in the &smb.conf; file. The additional - support for share-level ACLs is like frosting on the cake. It adds to security but is not essential - to it. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>valid users</primary> - </indexterm> - The <parameter>valid users</parameter> did not work on the <smbconfsection name="[homes]"/>. - Has this functionality been restored yet? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>meta-service</primary> - </indexterm> - Yes. This was fixed in Samba-3.0.2. The use of this parameter is strongly recommended as a safeguard - on the <smbconfsection name="[homes]"/> meta-service. The correct way to specify this is: - <smbconfoption name="valid users">%S</smbconfoption>. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>force user</primary> - </indexterm><indexterm> - <primary>force group</primary> - </indexterm><indexterm> - <primary>bias</primary> - </indexterm> - Is the bias against use of the <parameter>force user</parameter> and <parameter>force group</parameter> - really warranted? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>performance</primary> - </indexterm> - There is no bias. There is a determination to recommend the right tool for the task at hand. - After all, it is better than putting users through performance problems, isn't it? - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para> - The example given for file and directory access control forces all files to be owned by one - particular user. I do not like that. Is there any way I can see who created the file? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>SUID</primary> - </indexterm> - Sure. You do not have to set the SUID bit on the directory. Simply execute the following command - to permit file ownership to be retained by the user who created it: -<screen> -&rootprompt; find /usr/data/finance -type d -exec chmod g+s {}\; -</screen> - Note that this required no more than removing the <constant>u</constant> argument so that the - SUID bit is not set for the owner. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>Computer Management</primary> - </indexterm> - In the book, <quote>The Official Samba HOWTO and Reference Guide</quote>, you recommended use - of the Windows NT4 Server Manager (part of the <filename>SRVTOOLS.EXE</filename>) utility. Why - have you mentioned only the use of the Windows 200x/XP MMC Computer Management utility? - </para> - - </question> - <answer> - - <para><indexterm> - <primary>MMC</primary> - </indexterm><indexterm> - <primary>SRVTOOLS.EXE</primary> - </indexterm> - Either tool can be used with equal effect. There is no benefit of one over the other, except that - the MMC utility is present on all Windows 200x/XP systems and does not require additional software - to be downloaded and installed. Note that if you want to manage user and group accounts in your - Samba-controlled domain, the only tool that permits that is the NT4 Domain User Manager, which - is provided as part of the <filename>SRVTOOLS.EXE</filename> utility. - </para> - - </answer> - </qandaentry> - - <qandaentry> - <question> - - <para><indexterm> - <primary>valid users</primary> - </indexterm><indexterm> - <primary>Active Directory</primary> - </indexterm><indexterm> - <primary>Domain Member server</primary> - </indexterm> - I tried to set <parameter>valid users = @Engineers</parameter>, but it does not work. My Samba - server is an Active Directory domain member server. Has this been fixed now? - </para> - - </question> - <answer> - - <para> - The use of this parameter has always required the full specification of the domain account, for - example, <parameter>valid users = @"MEGANET2\Domain Admins"</parameter>. - </para> - - </answer> - </qandaentry> - - </qandaset> - -</sect1> - -</chapter> - diff --git a/docs-xml/Samba3-ByExample/index.xml b/docs-xml/Samba3-ByExample/index.xml index 7650af82dc9..6b2b6071e4c 100644 --- a/docs-xml/Samba3-ByExample/index.xml +++ b/docs-xml/Samba3-ByExample/index.xml @@ -126,14 +126,12 @@ published regarding Samba, or just to gain a more broad understanding of how Sam play in a Windows networking world.
</para>
-</partintro>
-
- <?latex \cleardoublepage ?>
- <xi:include href="SBE-KerberosFastStart.xml"/>
- <?latex \cleardoublepage ?>
- <xi:include href="SBE-DomainAppsSupport.xml"/>
- <?latex \cleardoublepage ?>
- <xi:include href="SBE-HighAvailability.xml"/>
+</partintro> + + <?latex \cleardoublepage ?> + <xi:include href="SBE-DomainAppsSupport.xml"/> + <?latex \cleardoublepage ?> + <xi:include href="SBE-HighAvailability.xml"/> <?latex \cleardoublepage ?>
<xi:include href="SBE-Support.xml"/>
<?latex \cleardoublepage ?>
|