Client Authentication:Ubuntu

	Warning:
	This is based upon limited testing and a small number of users via a VirtualBox virtual machine installation of Ubuntu 9.10, and subsequently a VMWare virtual machine installation with Ubuntu 10.04 LTS. YMMV

Authors

Original howto by Nash Consultancy

Revised by David Harper

Ubuntu 10.04 Authentication

Introduction

The following details the setup of Ubuntu 10.04 Lucid Lynx as a desktop to authenticate users against SME 7.5.1 using Samba and Winbind. The method has been tested using Ubuntu installed in a VMware virtual machine on a Windows 7 host. It assumes login is via Ubuntu's standard GDM login screen.

Ubuntu 10.04 is a long term service release, and will be supported on the desktop until April 2013.

Install Ubuntu

• Download the Ubuntu .iso and install.

	Tip:
	When prompted for a user name to log in with, give a non-SME user such as 'localuser', as this first user effectively becomes a local user with sudo root access. Make sure you set the 'Name of this Computer' to something less than 15 characters.

• Complete install, login and apply all updates.

Additional Packages

Use the 'System - Administration - Synaptic Package Manager' to install additional packages

auth-client-config
winbind
libpam-mount
smbfs

Optionally, you can use the command line:

sudo aptitude install auth-client-config winbind libpam-mount smbfs

Samba Modifications

• Open an 'Applications - Accessories - Terminal' cli and change to root privileges

sudo su

• Open and edit /etc/samba/smb.conf. Find the relevant lines and alter them or uncomment them as below. Some lines may not exist and may need to be added.

Replace <WORKGROUP> below with the 'Windows workgroup' name of your SME server. Replace <ip of sme server> below with the internal network ip address of your SME server.

workgroup = <WORKGROUP>
wins server = <ip of sme server>
name resolve order = wins host lmhosts bcast
security = domain
password server = <ip of sme server>
socket options = TCP_NODELAY
idmap uid = 5000-20000
idmap gid = 5000-20000
template shell = /bin/bash
template homedir = /home/%D/%U
winbind enum users = yes
winbind enum groups = yes
winbind cache time = 10
winbind use default domain = yes

• To check validation of smb.conf, run

testparm

• If all OK, then run

net rpc join -D <WORKGROUP> -U admin

Enter the admin password for the SME server when prompted and you should get a message,

Joined domain <WORKGROUP>

• Restart the machine to apply the changes.

	Note:
	You could miss out this restart step and carry on with the modifications below, but the following commands and the full join to SME didn't seem to work until the machine had been restarted and reconnected to the server. This may be a timing/delay issue similar to the volume mount (see below) due to NAT traversal. The restart may be unnecessary - can anyone confirm??

• Login as the local user, open a Terminal cli and 'sudo su' again
• The following commands should now list users, groups and available shares respectively from the SME server

wbinfo -u
wbinfo -g
smbtree

Authentication Modifications

	Warning:
	Altering the pam system authentication files can seriously effect your ability to login in to the system. Take a backup of the /etc/pam.d directory and /etc/nsswitch.conf. Have a live CD available to give access and re-apply the backup files if you make a mistake and/or get locked out

• Open and edit /etc/nsswitch.conf and find the hosts: line. Change it to

hosts: files wins dns

• Change to the auth-client-config tool profile directory

cd /etc/auth-client-config/profile.d

• Create and edit a new file called acc-sme, and enter

[sme]
nss_group=group:        compat winbind
nss_netgroup=netgroup:  nis
nss_passwd=passwd:      compat winbind
nss_shadow=shadow:      compat
pam_account=account  [success=2 new_authtok_reqd=done default=ignore]  pam_winbind.so
            account  [success=1 default=ignore]                        pam_unix.so	use_first_pass	use_authtok
            account  requisite                                         pam_deny.so
            account  required                                          pam_permit.so
pam_auth=auth	[success=2 default=ignore]  pam_winbind.so	
         auth	[success=1 default=ignore]  pam_unix.so       nullok_secure  use_first_pass  use_authtok
         auth	requisite	            pam_deny.so
         auth	required		    pam_permit.so
         auth	required		    pam_securetty.so
         auth	optional		    pam_mount.so      enable_pam_password
pam_password=password	[success=2 default=ignore]  pam_unix.so     obscure sha512
             password	[success=1 default=ignore]  pam_winbind.so  use_first_pass  md5  use_authtok
             password	requisite		    pam_deny.so
             password	required		    pam_permit.so
             password	optional	            pam_gnome_keyring.so
pam_session=session  [default=1]  pam_permit.so
            session  requisite    pam_deny.so
            session  required     pam_permit.so
            session  optional     pam_winbind.so
            session  required     pam_unix.so 
            session  required     pam_mkhomedir.so	skel=/etc/skel	umask=0022
            session  optional     pam_mount.so	        enable_pam_password
            session  optional     pam_ck_connector.so  nox11

	Tip:
	You can use auth-client-config -S > acc-sme to create the file first, containing the current pam files configuration, and then just modify

• Save the file. Apply the pam authorisation changes

auth-client-config -a -p sme

Automount User Home Directories at Login

cd /etc/security

• Open and edit pam_mount.conf.xml file. Find the 'Volume Definitions' section. Add a volume line below the header

<!-- Volume Definitions --> 
<volume fstype="cifs" server="<SMESERVER>" path="homes" mountpoint="~/nethome" options="nosuid,nodev" />

• Replace <SMESERVER> above with the samba name of your SME server. This will mount the users 'home' directory from SME into a directory called 'nethome' in their local home directory.

Automount Ibays at Login

• Edit /etc/security/pam_mount.conf.xml and add a line below the header

<!-- Volume Definitions --> 
<volume sgrp="<GROUPNAME>" fstype="cifs" server="<SMESERVER>" path="<IBAYNAME>" mountpoint="~/<IBAYNAME>" options="user=%(DOMAIN_USER),setuids,acl" />

• Replace <SMESERVER> with the samba name of your SME server, <IBAYNAME> with the ibay name, <GROUPNAME> with the description of the ibay owner group. The description can be recovered with

wbinfo -g

	Note:
	The sgrp param is optional. If used, ibay will be mounted only if %(DOMAIN_USER) is a member of ibay's owner group

Give Domain Admins local admin rights

• Edit /etc/sudoers and add the following line:

# Allow "Domain Admins" from the SME domain to run all commands
%<WORKGROUP>\\Domain\ Admins  ALL=(ALL) ALL

• Replace <WORKGROUP> with your SME server's Windows workgroup name.

Login and Test

• Exit the Terminal cli
• Reboot the machine.
• Login as a valid SME server user on your system, just giving username and password. No need for DOMAIN\user as samba configured above to use the default Windows Workgroup
• Authentication against SME should proceed and the user log in. A home directory on the local machine should be created as /home/DOMAIN/user, and a sub directory to that called 'nethome' mounted to the users home directory on the SME server. The mount point should also appear on the desktop.

Login screen security

Once you have confirmed that everything is working, you can optionally configure the graphical login screen to hide the names of both local users and SME users who have recently logged in. This won't stop any serious attempt to break into a machine but is roughly equivalent to similar options available with the Windows XP login screen.

Simply open a terminal and run:

sudo gconftool-2 --direct --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory --type Boolean --set /apps/gdm/simple-greeter/disable_user_list True

Issues / ToDo

This howto has only been tested in virtual non-production environments. Here are some issues you may encounter:

• If your SME Server is on a different subnet to the Ubuntu client, the login may stall after the username and password entered. This is due to the mount of the home directory, and although it does take a few moments it does eventually complete. The cause appears to be slow NAT traversal during the WINS lookup.
• If you do not reboot the Ubuntu client after running auth-client-config, you will be able to log in via GDM but no session will start.
• There is presently no way to emulate Windows' roaming profile feature. This issue should be solved when SME Server 8 is released, thanks to its LDAP authentication feature.
• The standard Ubuntu "Change Password" GUI program does not work. It gets stuck when trying to authenticate the current password. Similarly, the passwd CLI utility produces a segmentation fault. As a workaround, you can open a web browser and go to http://servername/user-password/ to change your password.
• The list of available users shown at the login screen is cleared after each reboot.

Ubuntu 9.10 Authentication

General information

The above howto was original written for Ubuntu 9.10, and was tested in a VirtualBox virtual machine. It should work with this older version of Ubuntu with the following caveats.

Memory leak bug

There is a bug in the version of Samba that ships with Ubuntu 9.10 (Karmic Koala) which causes an 'out of memory' error in winbindd. If you experience problems logging in, you can verify if this is the cause by searching for that phrase:

grep -i memory /var/log/samba/log.winbindd

A fix has been released in package samba-3.4.0-3ubuntu5.5, which was subsequently packaged as part of Ubuntu 10.04 (Lucid Lynx). It is also available in the karmic-proposed repository.

WARNING: Enabling the karmic-proposed repository on a production machine could cause instability. It is recommended that, in addition to adding the repository to /etc/apt/sources.list, you also create a file named /etc/apt/preferences.d/karmic-proposed, with the following contents:

Package: *
Pin: release a=karmic-security
Pin-Priority: 990

Package: *
Pin: release a=karmic-updates
Pin-Priority: 900

Package: *
Pin: release a=karmic-proposed
Pin-Priority: 400

Use aptitude to select only the packages that you need and install them:

sudo aptitude install samba/karmic-proposed
sudo aptitude install samba-common-bin/karmic-proposed

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