From 545649a05f4d634bb93471bd946a92b1c5644684 Mon Sep 17 00:00:00 2001 From: Gerald Carter Date: Tue, 27 Feb 2001 22:09:24 +0000 Subject: more updates and autogen (This used to be commit 2d3429cfe2d19b667400e408a4947efd160d99c0) --- docs/docbook/howto/NT_Security.sgml | 342 ++++++++++++++++++++++++++++++++++++ 1 file changed, 342 insertions(+) create mode 100644 docs/docbook/howto/NT_Security.sgml (limited to 'docs/docbook/howto/NT_Security.sgml') diff --git a/docs/docbook/howto/NT_Security.sgml b/docs/docbook/howto/NT_Security.sgml new file mode 100644 index 0000000000..62550bfaa6 --- /dev/null +++ b/docs/docbook/howto/NT_Security.sgml @@ -0,0 +1,342 @@ + + +
+ + + + 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 force directory mode 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. + + +
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