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diff --git a/docs/htmldocs/NT_Security.html b/docs/htmldocs/NT_Security.html new file mode 100644 index 0000000000..eb4d3a2355 --- /dev/null +++ b/docs/htmldocs/NT_Security.html @@ -0,0 +1,254 @@ + + + + + + +<html><head><title>Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4</title> + +<link rev="made" href="mailto:samba@samba.org"> +</head> +<body> + +<hr> + +<h1>Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4</h1> +<h2>Jeremy Allison, Samba Team</h2> +<h2>12th April 1999</h2> + +<h1>Table of Contents </h1><p></p> + +<p><hr><p><br> +<p><center><strong>Viewing and changing UNIX permissions using the NT security dialogs</strong> </center><br> +<center><strong>-------------------------------------------------------------------</strong> </center> +<p>New in the <strong>Samba 2.0.4</strong> release is the +ability for Windows NT clients to use their native security +settings dialog box to view and modify the underlying UNIX +permissions. +<p>Note that this ability is careful not to compromise the security +of the UNIX host Samba is running on, and still obeys all the +file permission rules that a Samba administrator can set. +<p>In Samba 2.0.4 and above the default value of the parameter +<a href="smb.conf.5.html#ntaclsupport"><strong>"nt acl support"</strong></a> has been +changed from "false" to "true", so manipulation of permissions is +turned on by default. +<p><strong>How to view file security on a Samba share</strong><br> +<strong>------------------------------------------</strong> +<p>From an NT 4.0 client, single-click with the right mouse button on +any file or directory in a Samba mounted drive letter or UNC path. +When the menu pops-up, click on the <code>Properties</code> entry at the +bottom of the menu. This brings up the normal file properties dialog +box, but with Samba 2.0.4 this will have a new tab along the top +marked <code>Security</code>. Click on this tab and you will see three buttons, +<em>Permissions</em>, <em>Auditing</em>, and <em>Ownership</em>. The <em>Auditing</em> +button will cause either an error message <code>"A requested privilege is +not held by the client"</code> to appear if the user is not the NT Administrator, +or a dialog which is intended to allow an Administrator to add +auditing requirements to a file if the user is logged on as the +NT Administrator. This dialog is non-functional with a Samba +share at this time, as the only useful button, the <code>Add</code> button +will not currently allow a list of users to be seen. +<p><strong>Viewing file ownership</strong><br> +<strong>----------------------</strong> +<p>Clicking on the <code>"Ownership"</code> button brings up a dialog box telling +you who owns the given file. The owner name will be of the form : +<p><code>"SERVER\user (Long name)"</code> +<p>Where <code>SERVER</code> is the NetBIOS name of the Samba server, <code>user</code> +is the user name of the UNIX user who owns the file, and <code>(Long name)</code> +is the discriptive string identifying the user (normally found in the +GECOS field of the UNIX password database). Click on the <code>Close</code> +button to remove this dialog. +<p>If the parameter <a href="smb.conf.5.html#ntaclsupport"><strong>"nt acl support"</strong></a> +is set to "false" then the file owner will be shown as the NT user +<code>"Everyone"</code>. +<p>The <code>Take Ownership</code> button will not allow you to change the +ownership of this file to yourself (clicking on it will display a +dialog box complaining that the user you are currently logged onto +the NT client cannot be found). The reason for this is that changing +the ownership of a file is a privilaged operation in UNIX, available +only to the <em>root</em> user. As clicking on this button causes NT to +attempt to change the ownership of a file to the current user logged +into the NT client this will not work with Samba at this time. +<p>There is an NT chown command that will work with Samba and allow +a user with Administrator privillage connected to a Samba 2.0.4 +server as root to change the ownership of files on both a local NTFS +filesystem or remote mounted NTFS or Samba drive. This is available +as part of the <strong>Seclib</strong> NT security library written by Jeremy +Allison of the Samba Team, available from the main Samba ftp site. +<p><strong>Viewing file or directory permissions</strong><br> +<strong>-------------------------------------</strong> +<p>The third button is the <code>"Permissions"</code> button. Clicking on this +brings up a dialog box that shows both the permissions and the UNIX +owner of the file or directory. The owner is displayed in the form : +<p><code>"SERVER\user (Long name)"</code> +<p>Where <code>SERVER</code> is the NetBIOS name of the Samba server, <code>user</code> +is the user name of the UNIX user who owns the file, and <code>(Long name)</code> +is the discriptive string identifying the user (normally found in the +GECOS field of the UNIX password database). +<p>If the parameter <a href="smb.conf.5.html#ntaclsupport"><strong>"nt acl support"</strong></a> +is set to "false" then the file owner will be shown as the NT user +<code>"Everyone"</code> and the permissions will be shown as NT <code>"Full Control"</code>. +<p>The permissions field is displayed differently for files and directories, +so I'll describe the way file permissions are displayed first. +<p><strong>File Permissions</strong><br> +<strong>----------------</strong> +<p>The standard UNIX user/group/world triple and the correspinding +"read", "write", "execute" permissions triples are mapped by Samba +into a three element NT ACL with the 'r', 'w', and 'x' bits mapped +into the corresponding NT permissions. The UNIX world permissions are mapped +into the global NT group <code>Everyone</code>, followed by the list of permissions +allowed for UNIX world. The UNIX owner and group permissions +are displayed as an NT <code>user</code> icon and an NT <code>local group</code> icon +respectively followed by the list of permissions allowed for the +UNIX user and group. +<p>As many UNIX permission sets don't map into common NT names such as +<code>"read"</code>, <code>"change"</code> or <code>"full control"</code> then usually the permissions +will be prefixed by the words <code>"Special Access"</code> in the NT display +list. +<p>But what happens if the file has no permissions allowed for a +particular UNIX user group or world component ? In order to +allow "no permissions" to be seen and modified then Samba overloads +the NT <code>"Take Ownership"</code> ACL attribute (which has no meaning in +UNIX) and reports a component with no permissions as having the NT +<code>"O"</code> bit set. This was chosen of course to make it look like a +zero, meaning zero permissions. More details on the decision behind +this will be given below. +<p><strong>Directory Permissions</strong><br> +<strong>---------------------</strong> +<p>Directories on an NT NTFS file system have two different sets of +permissions. The first set of permissions is the ACL set on the +directory itself, this is usually displayed in the first set of +parentheses in the normal <code>"RW"</code> NT style. This first set of +permissions is created by Samba in exactly the same way as normal +file permissions are, described above, and is displayed in the +same way. +<p>The second set of directory permissions has no real meaning in the +UNIX permissions world and represents the <code>"inherited"</code> permissions +that any file created within this directory would inherit. +<p>Samba synthesises these inherited permissions for NT by returning as +an NT ACL the UNIX permission mode that a new file created by Samba +on this share would receive. +<p><strong>Modifying file or directory permissions</strong><br> +<strong>---------------------------------------</strong> +<p>Modifying file and directory permissions is as simple as changing +the displayed permissions in the dialog box, and clicking the <code>OK</code> +button. However, there are limitations that a user needs to be aware +of, and also interactions with the standard Samba permission masks +and mapping of DOS attributes that need to also be taken into account. +<p>If the parameter <a href="smb.conf.5.html#ntaclsupport"><strong>"nt acl support"</strong></a> +is set to "false" then any attempt to set security permissions will +fail with an <code>"Access Denied"</code> message. +<p>The first thing to note is that the <code>"Add"</code> button will not return +a list of users in Samba 2.0.4 (it will give an error message of +<code>"The remote proceedure call failed and did not execute"</code>). This +means that you can only manipulate the current user/group/world +permissions listed in the dialog box. This actually works quite well +as these are the only permissions that UNIX actually has. +<p>If a permission triple (either user, group, or world) is removed from +the list of permissions in the NT dialog box, then when the <code>"OK"</code> +button is pressed it will be applied as "no permissions" on the UNIX +side. If you then view the permissions again the "no permissions" entry +will appear as the NT <code>"O"</code> flag, as described above. This allows you +to add permissions back to a file or directory once you have removed +them from a triple component. +<p>As UNIX supports only the "r", "w" and "x" bits of an NT ACL +then if other NT security attributes such as "Delete access" +are selected then they will be ignored when applied on the +Samba server. +<p>When setting permissions on a directory the second set of permissions +(in the second set of parentheses) is by default applied to all +files within that directory. If this is not what you want you +must uncheck the <code>"Replace permissions on existing files"</code> checkbox +in the NT dialog before clicking <code>"OK"</code>. +<p>If you wish to remove all permissions from a user/group/world +component then you may either highlight the component and click +the <code>"Remove"</code> button, or set the component to only have the special +<code>"Take Ownership"</code> permission (dsplayed as <code>"O"</code>) highlighted. +<p><strong>Interaction with the standard Samba create mask parameters</strong><br> +<strong>----------------------------------------------------------</strong> +<p>Note that with Samba 2.0.5 there are four new parameters to +control this interaction. +<p>These are : +<p><code>security mask</code> +<code>force security mode</code> +<code>directory security mask</code> +<code>force directory security mode</code> +<p>Once a user clicks <code>"OK"</code> to apply the permissions Samba maps +the given permissions into a user/group/world r/w/x triple set, +and then will check the changed permissions for a file against +the bits set in the <a href="smb.conf.5.html#securitymask"><strong>"security mask"</strong></a> +parameter. Any bits that were changed that are not set to '1' +in this parameter are left alone in the file permissions. +<p>Essentially, zero bits in the <a href="smb.conf.5.html#securitymask"><strong>"security mask"</strong></a> +mask may be treated as a set of bits the user is <em>not</em> allowed to change, +and one bits are those the user is allowed to change. +<p>If not set explicitly this parameter is set to the same value as the +<a href="smb.conf.5.html#createmask"><strong>"create mask"</strong></a> parameter to provide compatibility +with Samba 2.0.4 where this permission change facility was introduced. +To allow a user to modify all the user/group/world permissions on a file, +set this parameter to 0777. +<p>Next Samba checks the changed permissions for a file against the +bits set in the <a href="smb.conf.5.html#forcesecuritymode"><strong>"force security mode"</strong></a> +parameter. Any bits that were changed that correspond to bits set +to '1' in this parameter are forced to be set. +<p>Essentially, bits set in the <a href="smb.conf.5.html#forcesecuritymode"><strong>"force security mode"</strong></a> +parameter may be treated as a set of bits that, when modifying security on a file, the +user has always set to be 'on'. +<p>If not set explicitly this parameter is set to the same value as the +<a href="smb.conf.5.html#forcecreatemode"><strong>"force create mode"</strong></a> parameter to provide compatibility +with Samba 2.0.4 where the permission change facility was introduced. +To allow a user to modify all the user/group/world permissions on a file, +with no restrictions set this parameter to 000. +<p>The <a href="smb.conf.5.html#securitymask"><strong>"security mask"</strong></a> and +<a href="smb.conf.5.html#forcesecuritymode"><strong>"force security mode"</strong></a> parameters +are applied to the change request in that order. +<p>For a directory Samba will perform the same operations as described above +for a file except using the parameter <a href="smb.conf.5.html#directorysecuritymask"><strong>"directory security mask"</strong></a> +instead of <a href="smb.conf.5.html#securitymask"><strong>"security mask"</strong></a>, and +<a href="smb.conf.5.html#forcedirectorysecuritymode"><strong>"force directory security mode"</strong></a> parameter instead +of <a href="smb.conf.5.html#forcesecuritymode"><strong>"force security mode"</strong></a>. +<p>The <a href="smb.conf.5.html#directorysecuritymask"><strong>"directory security mask"</strong></a> +parameter by default is set to the same value as the <a href="smb.conf.5.html#directorymask"><strong>"directory mask"</strong></a> +parameter and the <a href="smb.conf.5.html#forcedirectorysecuritymode"><strong>"force directory security mode"</strong></a> +parameter by default is set to the same value as the +iurl(<strong>"force directory mode"</strong>)(smb.conf.5.html#forcedirectorymode) parameter +to provide compatibility with Samba 2.0.4 where the permission change facility was introduced. +<p>In this way Samba enforces the permission restrictions that an administrator +can set on a Samba share, whilst still allowing users to modify the +permission bits within that restriction. +<p>If you want to set up a share that allows users full control +in modifying the permission bits on their files and directories and +doesn't force any particular bits to be set 'on', then set the following +parameters in the <a href="smb.conf.5.html"><strong>smb.conf.5</strong></a> file in +that share specific section : +<p><code>security mask = 0777</code> +<code>force security mode = 0</code> +<code>directory security mask = 0777</code> +<code>force directory security mode = 0</code> +<p>As described, in Samba 2.0.4 the parameters : +<p><code>create mask</code> +<code>force create mode</code> +<code>directory mask</code> +<code>force directory mode</code> +<p>were used instead of the parameters discussed here. +<p><strong>Interaction with the standard Samba file attribute mapping</strong><br> +<strong>----------------------------------------------------------</strong> +<p>Samba maps some of the DOS attribute bits (such as "read only") +into the UNIX permissions of a file. This means there can be a +conflict between the permission bits set via the security dialog +and the permission bits set by the file attribute mapping. +<p>One way this can show up is if a file has no UNIX read access +for the owner it will show up as "read only" in the standard +file attributes tabbed dialog. Unfortunately this dialog is +the same one that contains the security info in another tab. +<p>What this can mean is that if the owner changes the permissions +to allow themselves read access using the security dialog, clicks +<code>"OK"</code> to get back to the standard attributes tab dialog, and +then clicks <code>"OK"</code> on that dialog, then NT will set the file +permissions back to read-only (as that is what the attributes +still say in the dialog). This means that after setting permissions +and clicking <code>"OK"</code> to get back to the attributes dialog you +should always hit <code>"Cancel"</code> rather than <code>"OK"</code> to ensure +that your changes are not overridden. +</body> +</html> diff --git a/docs/textdocs/NT_Security.txt b/docs/textdocs/NT_Security.txt new file mode 100644 index 0000000000..4620dd8408 --- /dev/null +++ b/docs/textdocs/NT_Security.txt @@ -0,0 +1,304 @@ + +TITLE INFORMATION: Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4 +AUTHOR INFORMATION: Jeremy Allison, Samba Team +DATE INFORMATION: 12th April 1999 + +Table of Contents + +Viewing and changing UNIX permissions using the NT security dialogs + +------------------------------------------------------------------- + +New in the Samba 2.0.4 release is the +ability for Windows NT clients to use their native security +settings dialog box to view and modify the underlying UNIX +permissions. + +Note that this ability is careful not to compromise the security +of the UNIX host Samba is running on, and still obeys all the +file permission rules that a Samba administrator can set. + +In Samba 2.0.4 and above the default value of the parameter +"nt acl support" has been +changed from "false" to "true", so manipulation of permissions is +turned on by default. + +How to view file security on a Samba share + +------------------------------------------ + +From an NT 4.0 client, single-click with the right mouse button on +any file or directory in a Samba mounted drive letter or UNC path. +When the menu pops-up, click on the Properties entry at the +bottom of the menu. This brings up the normal file properties dialog +box, but with Samba 2.0.4 this will have a new tab along the top +marked Security. Click on this tab and you will see three buttons, +Permissions, Auditing, and Ownership. The Auditing +button will cause either an error message "A requested privilege is +not held by the client" to appear if the user is not the NT Administrator, +or a dialog which is intended to allow an Administrator to add +auditing requirements to a file if the user is logged on as the +NT Administrator. This dialog is non-functional with a Samba +share at this time, as the only useful button, the Add button +will not currently allow a list of users to be seen. + +Viewing file ownership + +---------------------- + +Clicking on the "Ownership" button brings up a dialog box telling +you who owns the given file. The owner name will be of the form : + +"SERVER\user (Long name)" + +Where SERVER is the NetBIOS name of the Samba server, user +is the user name of the UNIX user who owns the file, and (Long name) +is the discriptive string identifying the user (normally found in the +GECOS field of the UNIX password database). Click on the Close +button to remove this dialog. + +If the parameter "nt acl support" +is set to "false" then the file owner will be shown as the NT user +"Everyone". + +The Take Ownership button will not allow you to change the +ownership of this file to yourself (clicking on it will display a +dialog box complaining that the user you are currently logged onto +the NT client cannot be found). The reason for this is that changing +the ownership of a file is a privilaged operation in UNIX, available +only to the root user. As clicking on this button causes NT to +attempt to change the ownership of a file to the current user logged +into the NT client this will not work with Samba at this time. + +There is an NT chown command that will work with Samba and allow +a user with Administrator privillage connected to a Samba 2.0.4 +server as root to change the ownership of files on both a local NTFS +filesystem or remote mounted NTFS or Samba drive. This is available +as part of the Seclib NT security library written by Jeremy +Allison of the Samba Team, available from the main Samba ftp site. + +Viewing file or directory permissions + +------------------------------------- + +The third button is the "Permissions" button. Clicking on this +brings up a dialog box that shows both the permissions and the UNIX +owner of the file or directory. The owner is displayed in the form : + +"SERVER\user (Long name)" + +Where SERVER is the NetBIOS name of the Samba server, user +is the user name of the UNIX user who owns the file, and (Long name) +is the discriptive string identifying the user (normally found in the +GECOS field of the UNIX password database). + +If the parameter "nt acl support" +is set to "false" then the file owner will be shown as the NT user +"Everyone" and the permissions will be shown as NT "Full Control". + +The permissions field is displayed differently for files and directories, +so I'll describe the way file permissions are displayed first. + +File Permissions + +---------------- + +The standard UNIX user/group/world triple and the correspinding +"read", "write", "execute" permissions triples are mapped by Samba +into a three element NT ACL with the 'r', 'w', and 'x' bits mapped +into the corresponding NT permissions. The UNIX world permissions are mapped +into the global NT group Everyone, followed by the list of permissions +allowed for UNIX world. The UNIX owner and group permissions +are displayed as an NT user icon and an NT local group icon +respectively followed by the list of permissions allowed for the +UNIX user and group. + +As many UNIX permission sets don't map into common NT names such as +"read", "change" or "full control" then usually the permissions +will be prefixed by the words "Special Access" in the NT display +list. + +But what happens if the file has no permissions allowed for a +particular UNIX user group or world component ? In order to +allow "no permissions" to be seen and modified then Samba overloads +the NT "Take Ownership" ACL attribute (which has no meaning in +UNIX) and reports a component with no permissions as having the NT +"O" bit set. This was chosen of course to make it look like a +zero, meaning zero permissions. More details on the decision behind +this will be given below. + +Directory Permissions + +--------------------- + +Directories on an NT NTFS file system have two different sets of +permissions. The first set of permissions is the ACL set on the +directory itself, this is usually displayed in the first set of +parentheses in the normal "RW" NT style. This first set of +permissions is created by Samba in exactly the same way as normal +file permissions are, described above, and is displayed in the +same way. + +The second set of directory permissions has no real meaning in the +UNIX permissions world and represents the "inherited" permissions +that any file created within this directory would inherit. + +Samba synthesises these inherited permissions for NT by returning as +an NT ACL the UNIX permission mode that a new file created by Samba +on this share would receive. + +Modifying file or directory permissions + +--------------------------------------- + +Modifying file and directory permissions is as simple as changing +the displayed permissions in the dialog box, and clicking the OK +button. However, there are limitations that a user needs to be aware +of, and also interactions with the standard Samba permission masks +and mapping of DOS attributes that need to also be taken into account. + +If the parameter "nt acl support" +is set to "false" then any attempt to set security permissions will +fail with an "Access Denied" message. + +The first thing to note is that the "Add" button will not return +a list of users in Samba 2.0.4 (it will give an error message of +"The remote proceedure call failed and did not execute"). This +means that you can only manipulate the current user/group/world +permissions listed in the dialog box. This actually works quite well +as these are the only permissions that UNIX actually has. + +If a permission triple (either user, group, or world) is removed from +the list of permissions in the NT dialog box, then when the "OK" +button is pressed it will be applied as "no permissions" on the UNIX +side. If you then view the permissions again the "no permissions" entry +will appear as the NT "O" flag, as described above. This allows you +to add permissions back to a file or directory once you have removed +them from a triple component. + +As UNIX supports only the "r", "w" and "x" bits of an NT ACL +then if other NT security attributes such as "Delete access" +are selected then they will be ignored when applied on the +Samba server. + +When setting permissions on a directory the second set of permissions +(in the second set of parentheses) is by default applied to all +files within that directory. If this is not what you want you +must uncheck the "Replace permissions on existing files" checkbox +in the NT dialog before clicking "OK". + +If you wish to remove all permissions from a user/group/world +component then you may either highlight the component and click +the "Remove" button, or set the component to only have the special +"Take Ownership" permission (dsplayed as "O") highlighted. + +Interaction with the standard Samba create mask parameters + +---------------------------------------------------------- + +Note that with Samba 2.0.5 there are four new parameters to +control this interaction. + +These are : + +security mask +force security mode +directory security mask +force directory security mode + +Once a user clicks "OK" to apply the permissions Samba maps +the given permissions into a user/group/world r/w/x triple set, +and then will check the changed permissions for a file against +the bits set in the "security mask" +parameter. Any bits that were changed that are not set to '1' +in this parameter are left alone in the file permissions. + +Essentially, zero bits in the "security mask" +mask may be treated as a set of bits the user is not allowed to change, +and one bits are those the user is allowed to change. + +If not set explicitly this parameter is set to the same value as the +"create mask" parameter to provide compatibility +with Samba 2.0.4 where this permission change facility was introduced. +To allow a user to modify all the user/group/world permissions on a file, +set this parameter to 0777. + +Next Samba checks the changed permissions for a file against the +bits set in the "force security mode" +parameter. Any bits that were changed that correspond to bits set +to '1' in this parameter are forced to be set. + +Essentially, bits set in the "force security mode" +parameter may be treated as a set of bits that, when modifying security on a file, the +user has always set to be 'on'. + +If not set explicitly this parameter is set to the same value as the +"force create mode" parameter to provide compatibility +with Samba 2.0.4 where the permission change facility was introduced. +To allow a user to modify all the user/group/world permissions on a file, +with no restrictions set this parameter to 000. + +The "security mask" and +"force security mode" parameters +are applied to the change request in that order. + +For a directory Samba will perform the same operations as described above +for a file except using the parameter "directory security mask" +instead of "security mask", and +"force directory security mode" parameter instead +of "force security mode". + +The "directory security mask" +parameter by default is set to the same value as the "directory mask" +parameter and the "force directory security mode" +parameter by default is set to the same value as the +iurl("force directory mode")(smb.conf.5.html#forcedirectorymode) parameter +to provide compatibility with Samba 2.0.4 where the permission change facility was introduced. + +In this way Samba enforces the permission restrictions that an administrator +can set on a Samba share, whilst still allowing users to modify the +permission bits within that restriction. + +If you want to set up a share that allows users full control +in modifying the permission bits on their files and directories and +doesn't force any particular bits to be set 'on', then set the following +parameters in the smb.conf.5 file in +that share specific section : + +security mask = 0777 +force security mode = 0 +directory security mask = 0777 +force directory security mode = 0 + +As described, in Samba 2.0.4 the parameters : + +create mask +force create mode +directory mask +force directory mode + +were used instead of the parameters discussed here. + +Interaction with the standard Samba file attribute mapping + +---------------------------------------------------------- + +Samba maps some of the DOS attribute bits (such as "read only") +into the UNIX permissions of a file. This means there can be a +conflict between the permission bits set via the security dialog +and the permission bits set by the file attribute mapping. + +One way this can show up is if a file has no UNIX read access +for the owner it will show up as "read only" in the standard +file attributes tabbed dialog. Unfortunately this dialog is +the same one that contains the security info in another tab. + +What this can mean is that if the owner changes the permissions +to allow themselves read access using the security dialog, clicks +"OK" to get back to the standard attributes tab dialog, and +then clicks "OK" on that dialog, then NT will set the file +permissions back to read-only (as that is what the attributes +still say in the dialog). This means that after setting permissions +and clicking "OK" to get back to the attributes dialog you +should always hit "Cancel" rather than "OK" to ensure +that your changes are not overridden. diff --git a/docs/yodldocs/NT_Security.yo b/docs/yodldocs/NT_Security.yo new file mode 100644 index 0000000000..ab9f29f0dd --- /dev/null +++ b/docs/yodldocs/NT_Security.yo @@ -0,0 +1,292 @@ +mailto(samba@samba.org) + +article(Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4)(Jeremy Allison, Samba Team)(12th April 1999) + +center(bf(Viewing and changing UNIX permissions using the NT security dialogs))nl() +center(bf(-------------------------------------------------------------------)) + +New in the bf(Samba 2.0.4) release is the +ability for Windows NT clients to use their native security +settings dialog box to view and modify the underlying UNIX +permissions. + +Note that this ability is careful not to compromise the security +of the UNIX host Samba is running on, and still obeys all the +file permission rules that a Samba administrator can set. + +In Samba 2.0.4 and above the default value of the parameter +url(bf("nt acl support"))(smb.conf.5.html#ntaclsupport) has been +changed from "false" to "true", so manipulation of permissions is +turned on by default. + +bf(How to view file security on a Samba share)nl() +bf(------------------------------------------) + +From an NT 4.0 client, single-click with the right mouse button on +any file or directory in a Samba mounted drive letter or UNC path. +When the menu pops-up, click on the tt(Properties) entry at the +bottom of the menu. This brings up the normal file properties dialog +box, but with Samba 2.0.4 this will have a new tab along the top +marked tt(Security). Click on this tab and you will see three buttons, +em(Permissions), em(Auditing), and em(Ownership). The em(Auditing) +button will cause either an error message tt("A requested privilege is +not held by the client") to appear if the user is not the NT Administrator, +or a dialog which is intended to allow an Administrator to add +auditing requirements to a file if the user is logged on as the +NT Administrator. This dialog is non-functional with a Samba +share at this time, as the only useful button, the tt(Add) button +will not currently allow a list of users to be seen. + +bf(Viewing file ownership)nl() +bf(----------------------) + +Clicking on the tt("Ownership") button brings up a dialog box telling +you who owns the given file. The owner name will be of the form : + +tt("SERVER\user (Long name)") + +Where tt(SERVER) is the NetBIOS name of the Samba server, tt(user) +is the user name of the UNIX user who owns the file, and tt((Long name)) +is the discriptive string identifying the user (normally found in the +GECOS field of the UNIX password database). Click on the tt(Close) +button to remove this dialog. + +If the parameter url(bf("nt acl support"))(smb.conf.5.html#ntaclsupport) +is set to "false" then the file owner will be shown as the NT user +tt("Everyone"). + +The tt(Take Ownership) button will not allow you to change the +ownership of this file to yourself (clicking on it will display a +dialog box complaining that the user you are currently logged onto +the NT client cannot be found). The reason for this is that changing +the ownership of a file is a privilaged operation in UNIX, available +only to the em(root) user. As clicking on this button causes NT to +attempt to change the ownership of a file to the current user logged +into the NT client this will not work with Samba at this time. + +There is an NT chown command that will work with Samba and allow +a user with Administrator privillage connected to a Samba 2.0.4 +server as root to change the ownership of files on both a local NTFS +filesystem or remote mounted NTFS or Samba drive. This is available +as part of the bf(Seclib) NT security library written by Jeremy +Allison of the Samba Team, available from the main Samba ftp site. + +bf(Viewing file or directory permissions)nl() +bf(-------------------------------------) + +The third button is the tt("Permissions") button. Clicking on this +brings up a dialog box that shows both the permissions and the UNIX +owner of the file or directory. The owner is displayed in the form : + +tt("SERVER\user (Long name)") + +Where tt(SERVER) is the NetBIOS name of the Samba server, tt(user) +is the user name of the UNIX user who owns the file, and tt((Long name)) +is the discriptive string identifying the user (normally found in the +GECOS field of the UNIX password database). + +If the parameter url(bf("nt acl support"))(smb.conf.5.html#ntaclsupport) +is set to "false" then the file owner will be shown as the NT user +tt("Everyone") and the permissions will be shown as NT tt("Full Control"). + +The permissions field is displayed differently for files and directories, +so I'll describe the way file permissions are displayed first. + +bf(File Permissions)nl() +bf(----------------) + +The standard UNIX user/group/world triple and the correspinding +"read", "write", "execute" permissions triples are mapped by Samba +into a three element NT ACL with the 'r', 'w', and 'x' bits mapped +into the corresponding NT permissions. The UNIX world permissions are mapped +into the global NT group tt(Everyone), followed by the list of permissions +allowed for UNIX world. The UNIX owner and group permissions +are displayed as an NT tt(user) icon and an NT tt(local group) icon +respectively followed by the list of permissions allowed for the +UNIX user and group. + +As many UNIX permission sets don't map into common NT names such as +tt("read"), tt("change") or tt("full control") then usually the permissions +will be prefixed by the words tt("Special Access") in the NT display +list. + +But what happens if the file has no permissions allowed for a +particular UNIX user group or world component ? In order to +allow "no permissions" to be seen and modified then Samba overloads +the NT tt("Take Ownership") ACL attribute (which has no meaning in +UNIX) and reports a component with no permissions as having the NT +tt("O") bit set. This was chosen of course to make it look like a +zero, meaning zero permissions. More details on the decision behind +this will be given below. + +bf(Directory Permissions)nl() +bf(---------------------) + +Directories on an NT NTFS file system have two different sets of +permissions. The first set of permissions is the ACL set on the +directory itself, this is usually displayed in the first set of +parentheses in the normal tt("RW") NT style. This first set of +permissions is created by Samba in exactly the same way as normal +file permissions are, described above, and is displayed in the +same way. + +The second set of directory permissions has no real meaning in the +UNIX permissions world and represents the tt("inherited") permissions +that any file created within this directory would inherit. + +Samba synthesises these inherited permissions for NT by returning as +an NT ACL the UNIX permission mode that a new file created by Samba +on this share would receive. + +bf(Modifying file or directory permissions)nl() +bf(---------------------------------------) + +Modifying file and directory permissions is as simple as changing +the displayed permissions in the dialog box, and clicking the tt(OK) +button. However, there are limitations that a user needs to be aware +of, and also interactions with the standard Samba permission masks +and mapping of DOS attributes that need to also be taken into account. + +If the parameter url(bf("nt acl support"))(smb.conf.5.html#ntaclsupport) +is set to "false" then any attempt to set security permissions will +fail with an tt("Access Denied") message. + +The first thing to note is that the tt("Add") button will not return +a list of users in Samba 2.0.4 (it will give an error message of +tt("The remote proceedure call failed and did not execute")). This +means that you can only manipulate the current user/group/world +permissions listed in the dialog box. This actually works quite well +as these are the only permissions that UNIX actually has. + +If a permission triple (either user, group, or world) is removed from +the list of permissions in the NT dialog box, then when the tt("OK") +button is pressed it will be applied as "no permissions" on the UNIX +side. If you then view the permissions again the "no permissions" entry +will appear as the NT tt("O") flag, as described above. This allows you +to add permissions back to a file or directory once you have removed +them from a triple component. + +As UNIX supports only the "r", "w" and "x" bits of an NT ACL +then if other NT security attributes such as "Delete access" +are selected then they will be ignored when applied on the +Samba server. + +When setting permissions on a directory the second set of permissions +(in the second set of parentheses) is by default applied to all +files within that directory. If this is not what you want you +must uncheck the tt("Replace permissions on existing files") checkbox +in the NT dialog before clicking tt("OK"). + +If you wish to remove all permissions from a user/group/world +component then you may either highlight the component and click +the tt("Remove") button, or set the component to only have the special +tt("Take Ownership") permission (dsplayed as tt("O")) highlighted. + +bf(Interaction with the standard Samba create mask parameters)nl() +bf(----------------------------------------------------------) + +Note that with Samba 2.0.5 there are four new parameters to +control this interaction. + +These are : + +tt(security mask) +tt(force security mode) +tt(directory security mask) +tt(force directory security mode) + +Once a user clicks tt("OK") to apply the permissions Samba maps +the given permissions into a user/group/world r/w/x triple set, +and then will check the changed permissions for a file against +the bits set in the url(bf("security mask"))(smb.conf.5.html#securitymask) +parameter. Any bits that were changed that are not set to '1' +in this parameter are left alone in the file permissions. + +Essentially, zero bits in the url(bf("security mask"))(smb.conf.5.html#securitymask) +mask may be treated as a set of bits the user is em(not) allowed to change, +and one bits are those the user is allowed to change. + +If not set explicitly this parameter is set to the same value as the +url(bf("create mask"))(smb.conf.5.html#createmask) parameter to provide compatibility +with Samba 2.0.4 where this permission change facility was introduced. +To allow a user to modify all the user/group/world permissions on a file, +set this parameter to 0777. + +Next Samba checks the changed permissions for a file against the +bits set in the url(bf("force security mode"))(smb.conf.5.html#forcesecuritymode) +parameter. Any bits that were changed that correspond to bits set +to '1' in this parameter are forced to be set. + +Essentially, bits set in the url(bf("force security mode"))(smb.conf.5.html#forcesecuritymode) +parameter may be treated as a set of bits that, when modifying security on a file, the +user has always set to be 'on'. + +If not set explicitly this parameter is set to the same value as the +url(bf("force create mode"))(smb.conf.5.html#forcecreatemode) parameter to provide compatibility +with Samba 2.0.4 where the permission change facility was introduced. +To allow a user to modify all the user/group/world permissions on a file, +with no restrictions set this parameter to 000. + +The url(bf("security mask"))(smb.conf.5.html#securitymask) and +url(bf("force security mode"))(smb.conf.5.html#forcesecuritymode) parameters +are applied to the change request in that order. + +For a directory Samba will perform the same operations as described above +for a file except using the parameter url(bf("directory security mask"))(smb.conf.5.html#directorysecuritymask) +instead of url(bf("security mask"))(smb.conf.5.html#securitymask), and +url(bf("force directory security mode"))(smb.conf.5.html#forcedirectorysecuritymode) parameter instead +of url(bf("force security mode"))(smb.conf.5.html#forcesecuritymode). + +The url(bf("directory security mask"))(smb.conf.5.html#directorysecuritymask) +parameter by default is set to the same value as the url(bf("directory mask"))(smb.conf.5.html#directorymask) +parameter and the url(bf("force directory security mode"))(smb.conf.5.html#forcedirectorysecuritymode) +parameter by default is set to the same value as the +iurl(bf("force directory mode"))(smb.conf.5.html#forcedirectorymode) parameter +to provide compatibility with Samba 2.0.4 where the permission change facility was introduced. + +In this way Samba enforces the permission restrictions that an administrator +can set on a Samba share, whilst still allowing users to modify the +permission bits within that restriction. + +If you want to set up a share that allows users full control +in modifying the permission bits on their files and directories and +doesn't force any particular bits to be set 'on', then set the following +parameters in the url(bf(smb.conf.5))(smb.conf.5.html) file in +that share specific section : + +tt(security mask = 0777) +tt(force security mode = 0) +tt(directory security mask = 0777) +tt(force directory security mode = 0) + +As described, in Samba 2.0.4 the parameters : + +tt(create mask) +tt(force create mode) +tt(directory mask) +tt(force directory mode) + +were used instead of the parameters discussed here. + +bf(Interaction with the standard Samba file attribute mapping)nl() +bf(----------------------------------------------------------) + +Samba maps some of the DOS attribute bits (such as "read only") +into the UNIX permissions of a file. This means there can be a +conflict between the permission bits set via the security dialog +and the permission bits set by the file attribute mapping. + +One way this can show up is if a file has no UNIX read access +for the owner it will show up as "read only" in the standard +file attributes tabbed dialog. Unfortunately this dialog is +the same one that contains the security info in another tab. + +What this can mean is that if the owner changes the permissions +to allow themselves read access using the security dialog, clicks +tt("OK") to get back to the standard attributes tab dialog, and +then clicks tt("OK") on that dialog, then NT will set the file +permissions back to read-only (as that is what the attributes +still say in the dialog). This means that after setting permissions +and clicking tt("OK") to get back to the attributes dialog you +should always hit tt("Cancel") rather than tt("OK") to ensure +that your changes are not overridden. |