!== !== Recent-FAQs.txt for Samba release 2.0.4 18 May 1999 !== Contributor: Samba-bugs@samba.org Date: July 5, 1998 Status: Current ============================================================================= Subject: Recent FAQ answers to common questions / problems ============================================================================= Contents: NetWkstaUserLogon Not listening for calling name System Error 1240 Trapdoor UID User Access Control Using NT to Browse Samba Shares setup.exe and 16 bit programs smbclient -N NetWkstaUserLogon ================= FAQ answer about the new password server code: In 1.9.18 you can disable the NetWkstaUserLogon call at compile time in local.h and from 1.9.18p3 you can now disable it from an option in your smb.conf. The password server behaviour changed because we discovered that bugs in some NT servers allowed anyone to login with no password if they chose an account name that did not exist on the password server. The NT password server was saying "yes, it's OK to login" even when the account didn't exist at all! Adding the NetWkstaUserLogon call fixed the problem, and follows the "recommended" method that MS have recently documented for pass through authentication. The problem now is that some NT servers (in particular NT workstation?) don't support the NetWkstaUserLogon call. The call also doesn't work for accounts in trust relationships. The eventual solution for this will be to replace the password server code in Samba with NT domain code as that is developed. For now you have the choice of compiling Samba either with or without the NetWkstaUserLogon call in the password server code. In 1.9.18p3 the following was added (copied from the 1.9.18p3 release notes): In the [global] section of smb.conf : networkstation user login This code (submitted by Rob Nielsen) allows the code many people were having problems with that queries an NT password server to be turned off at runtime rather than compile time. Please see the documentation in the smb.conf manual page for details. This is a security option - it must only be turned off after checks have been made to ensure that your NT password server does not suffer from the bug this code was meant to protect against ! In 1.9.18 you can enable/disable this call in local.h. In 1.9.17p5 you could apply the following patch. Applying this patch will make the password server code behave like the code in earlier versions of Samba. If you do this then please ensure that you test to see that users are prevented from logging in if they give a bogus username/password. You may have a NT server that is affected by the bug that this code is designed to avoid. --- password.c 1997/10/21 10:09:28 1.25.2.4 +++ password.c 1997/12/31 06:43:06 @@ -1619,6 +1619,7 @@ } +#if 0 if (!cli_NetWkstaUserLogon(&cli,user,local_machine)) { DEBUG(1,("password server %s failed NetWkstaUserLogon\n", cli.desthost)); cli_tdis(&cli); @@ -1638,6 +1639,7 @@ cli_tdis(&cli); return False; } +#endif DEBUG(3,("password server %s accepted the password\n", cli.desthost)); =============================================================================== Not listening for calling name ============================== > Session request failed (131,129) with myname=HOBBES destname=CALVIN > Not listening for calling name If you get this when talking to a Samba box then it means that your global "hosts allow" or "hosts deny" settings are causing the Samba server to refuse the connection. Look carefully at your "hosts allow" and "hosts deny" lines in the global section of smb.conf. It can also be a problem with reverse DNS lookups not functioning correctly, leading to the remote host identity not being able to be confirmed, but that is less likely. =============================================================================== System Error 1240 ================= System error 1240 means that the client is refusing to talk to a non-encrypting server. Microsoft changed WinNT in service pack 3 to refuse to connect to servers that do not support SMB password encryption. There are two main solutions: 1) enable SMB password encryption in Samba. See ENCRYPTION.txt in the Samba docs 2) disable this new behaviour in NT. See WinNT.txt in the Samba docs =============================================================================== Trapdoor UID ============ > Log message "you appear to have a trapdoor uid system" This can have several causes. It might be because you are using a uid or gid of 65535 or -1. This is a VERY bad idea, and is a big security hole. Check carefully in your /etc/passwd file and make sure that no user has uid 65535 or -1. Especially check the "nobody" user, as many broken systems are shipped with nobody setup with a uid of 65535. It might also mean that your OS has a trapdoor uid/gid system :-) This means that once a process changes effective uid from root to another user it can't go back to root. Unfortunately Samba relies on being able to change effective uid from root to non-root and back again to implement its security policy. If your OS has a trapdoor uid system this won't work, and several things in Samba may break. Less things will break if you use user or server level security instead of the default share level security, but you may still strike problems. The problems don't give rise to any security holes, so don't panic, but it does mean some of Samba's capabilities will be unavailable. In particular you will not be able to connect to the Samba server as two different uids at once. This may happen if you try to print as a "guest" while accessing a share as a normal user. It may also affect your ability to list the available shares as this is normally done as the guest user. Complain to your OS vendor and ask them to fix their system. Note: the reason why 65535 is a VERY bad choice of uid and gid is that it casts to -1 as a uid, and the setreuid() system call ignores (with no error) uid changes to -1. This means any daemon attempting to run as uid 65535 will actually run as root. This is not good! =============================================================================== User Access Control =================== > In windows when i set up a share in "user mode" i get the message: > "You cannot view the list of users at this time. Please try again later." > > I know you have lists of users for access and aliasing purposes, but i > have read nothing to support the idea that these lists control the Domain > Users List... Samba does NOT at this time support user mode access control for Window 9x of for NT. This is a priority item and requires full implementation of the NT SMB protocol calls. Samba-1.9.19 will go into alpha in about 2 months time and will have a more full implementation of the NT SMB protocols to support Domain Client interoperability. When we can see that this has been succesful we wil then implement the NT SMB Server components. This will probably be released as Samba-2.0 Samba-1.9.18p5 is scheduled to go out within 14 days. This will close off the 1.9.18 branch and then opens the way to progress 1.9.19. I hope this answers your concerns adequately. =============================================================================== Using NT to Browse Samba Shares =============================== > WIN-NT workstations (nt4.0, service pack 3) > samba with > security = user > encrypt passwords = yes > guest account = guest > > start the explorer on a win-nt workstation and select network. I find > my unix server running samba, but I can not see the list of shares > unless I am a user, who is known in the smbpasswd of the unix machine. > The guest account "guest" exists on my unix machine. For testing I even > made him a regular user with a password. > > With my network monitor I can see, that the win-nt workstation uses the > current login, to connect to IPC$ on the samba server > (for example "administrator"), not the guest account. This is exactly how Windows NT works. You MUST have a valid account on the Windows NT box you are trying to see the resource list on. If your currently logged in account details do NOT match an account on the NT machine you are trying to access then you will be presented with a logon box for that machine. When you enter the name of an account on that machine / domain, together with a valid password then the resource list is made available. If the account details are not correct then no resource list is shown. Samba follows the behaviour of Windows NT exactly. Warning:Warning:Warning: ======================== Samba can be compiled with the GUEST_SESSION_SETUP option at 0,1 or 2. The default is 0. If this is set to 1 or 2 then Windows NT machines that DO NOT have an account on the Samba server will see the resource list. The down side of this is that legitimate users may then be refused access to their legitimate resources. Setting this option creates serious security holes. DO NOT DO IT. Samba has the value of this option set at 0 - NOT WITHOUT REASON!!!! ******> Warning:Warning:Warning: ****> Do not tamper with this setting!!! =============================================================================== setup.exe and 16 bit programs ============================= Running 16 bit programs from Windows NT on a Samba mapped drive --------------------------------------------------------------- The Windows NT redirector has a bug when running against a Samba or Windows 95 mapped drive and attempting to run a 16 bit executable. The problem occurs when the pathname to a 16 bit executable contains a non 8.3 filename complient directory component, Windows NT will fail to load the program and complain it cannot find the path to the program. It can be verified that this is a bug in Windows NT and not Samba as the same problem can be reproduced exactly when attempting to run the same program with the same pathname from a Windows 95 server (ie. the problem still exists even with no Samba server involved). Microsoft have been made aware of this problem, it is unknown if they regard it as serious enough to provide a fix for this. One of the reasons this problem is reported frequently is that InstallShield setup.exe executables are frequently written as 16 bit programs, and so hit this problem. As a workaround, you may create (on a Samba server at least) a symbolic link with an 8.3 complient name to the non 8.3 complient directory name, and then the 16 bit program will run. Alternatively, use the 8.3 complient mangled name to specify the path to run the binary. This will be fixed when Samba adds the NT-specific SMB calls (currently targeted for the next major Samba release), as once the NT SMB calls are used this problem no longer occurs (which is why the problem doesn't occur when running against a drive mapped to a Windows NT server). Regards, Jeremy Allison. Samba Team. =============================================================================== smbclient -N ============ > When getting the list of shares available on a host using the command > smbclient -N -L > the program always prompts for the password if the server is a Samba server. > It also ignores the "-N" argument when querying some (but not all) of our > NT servers. No, it does not ignore -N, it is just that your server rejected the null password in the connection, so smbclient prompts for a password to try again. To get the behaviour that you probably want use smbclient -L host -U% this will set both the username and password to null, which is an anonymous login for SMB. Using -N would only set the password to null, and this is not accepted as an anonymous login for most SMB servers. ===============================================================================