From 55e0505d840eaf17bc85bd12af9a42a9c0d23f05 Mon Sep 17 00:00:00 2001 From: Tim Potter Date: Mon, 5 Jun 2000 11:35:26 +0000 Subject: Copied across NT_Security documentation from 2.0 (This used to be commit 6f07da3b9146e880df3290e664a28f904ac252eb) --- docs/htmldocs/NT_Security.html | 254 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 254 insertions(+) create mode 100644 docs/htmldocs/NT_Security.html (limited to 'docs/htmldocs') 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 @@ + + + + + + +Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4 + + + + + +

+ +

Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4

Jeremy Allison, Samba Team

12th April 1999

+ +

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)" +

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. + + -- cgit

Viewing and changing UNIX permissions using the NT security dialogs in Samba 2.0.4

Jeremy Allison, Samba Team

12th April 1999

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