samba - Apr 2005 - IE improperly prompts for credentials; ntlm_auth with Samba 3.0.13, Squid 2.5.STABLE7, RedHat Linux 9.0, SmartFilter 4.01

This turned into the mother of all system integration exercises and I
**almost**  have it working.  
I am trying to set up proxy authorization using:  

	RedHat Linux 9.0, 
	MIT Kerberos 1.4 built from source, 
	Samba 3.0.13 built from source, 
	Squid 2.5.STABLE7 built from source
	SmartFilter 4.01.  
	Active Directory with Windows 2003

Why not use RPMs?  Well - ADS support for Windows 2003 needs Kerberos
1.3 or newer.  But RedHat 9.0 has Kerberos 1.2.7 and zillions of RedHat
packages depend on it.  So I need krb5 1.4 in another tree and
everything pretty much flows from that.  

See below for details on how I built all this, with attributions to
everyone who has helped so far.   Once this is up and running, I'll
update my step by step instructions and post them.  So below is a
snapshot as of right now and will likely change in a few hours.

Here is, I think, my last remaining problem getting this into
production. 

Whenever I launch IE on a client PC, IE prompts the user for
credentials.  IE is supposed to just pass the credentials to Squid
without annoying the user for this, but it doesn't and this is making me
nuts.  If the user enters 

	domain\username
	password

s(he) gets to the desired website via Squid/SmartFilter and I assume I
can set appropriate SmartFilter policies to regulate usage.  But it is
not acceptable for a user to always enter credentials and this
combination of software is supposed to eliminate that hassle.  

I must be missing something...
>From Windows, I can browse to the Linux box via My Network Places and
view its Samba shares.
>From Linux, getent passwd returns all the A/D usernames and getent group
returns all the A/D groups.
>From Linux, /usr/local/samba/bin/wbinfo -g, /usr/local/samba/bin/wbinfo
-u, and /usr/local/samba/bin/wbinfo -t work as advertised and return my
A/D groups, users, and verify the trust relationship.

/usr/local/samba/bin/ntlm_auth --username=[USERNAME] works as advertised
- success if a good username/password, failure otherwise.  Similarly, 

/usr/local/samba/bin/ntlm_auth --helper-protocol=squid-2.5-basic works
as advertised and returns OK if a good username/password, ERR otherwise.


Running /usr/local/samba/bin/ntlm_auth
--helper-protocol=squid-2.5-ntlmssp returns output I don't understand,
but the Squid FAQ says you can't really test this one by hand anyway.  

This all suggests Samba is good. 

Here are the relevant lines from /usr/local/etc/squid.conf
.
.
.
#  TAG: auth_param
#       This is used to define parameters for the various authentication

#       schemes supported by Squid.
#       
#       format: auth_param scheme parameter [setting]
#       
#       The order in which authentication schemes are presented to the
client is
.
.
.
auth_param basic children 5
#auth_param basic realm Squid proxy-caching web server
#auth_param basic credentialsttl 2 hours
auth_param basic casesensitive off

# Site specific configs

auth_param ntlm program /usr/local/samba/bin/ntlm_auth
--helper-protocol=squid-2.5-ntlmssp
auth_param ntlm children 30
auth_param ntlm max_challenge_reuses 0
auth_param ntlm max_challenge_lifetime 2 minutes

auth_param basic program /usr/local/samba/bin/ntlm_auth
--helper-protocol=squid-2.5-basic
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours
.
.
.
#
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS

# Example rule allowing access from your local networks. Adapt
# to list your (internal) IP networks from where browsing should
# be allowed
#acl our_networks src 192.168.1.0/24 192.168.2.0/24
#http_access allow our_networks

##acl my_network src 175.10.0.0/16
##http_access allow my_network

acl AuthorizedUsers proxy_auth REQUIRED
http_access allow all AuthorizedUsers

##acl password proxy_auth REQUIRED
##http_access allow password

# And finally deny all other access to this proxy
http_access deny all
.
.
.

This spawns another question - why do I need an auth_param for both ntlm
and basic authentication?  What's the difference?  Lots of documentation
all over the place says I need both and in this order but I haven't
found anything that says why.  Could this be a key to my problem?

Thanks

- Greg Scott
  GregScott@InfraSupportEtc.com




Here are the build notes - remember, this is a snapshot in time, useful
right now for debugging.  Below is a work in progress.


For Squid authentication with an Active Directory domain, we need Samba,
set
up with Kerberos.  

Redhat Linux 9.0 ships with Kerberos version 5, revision 1.2.7-10.
Unfortunately, 
we need at least rev 1.3 to work with Windows 2003.  See this URL for a
discussion:
http://lists.samba.org/archive/samba/2004-July/090137.html

The fc3 RPM directory has rev 1.3 RPMs.  Unfortunately, several dozen
components in RedHat 9.0 depend on the 1.2.7 RPMs installed, especially
the Kerberos libraries.  

So we need to build a copy of Kerberos from source and put it in an
alternate 
directory.  Then we'll build a copy of Samba using this Kerberos build.


We get the latest and greatest Kerberos from MIT.

For the MIT Kerberos download, see:
http://web.mit.edu/kerberos/www/

FOr release notes, see:
http://web.mit.edu/kerberos/www/krb5-1.4/README-1.4.txt

FOr the Installation Guide see:
http://web.mit.edu/kerberos/www/krb5-1.4/krb5-1.4/doc/krb5-install.html#
Building%20Kerberos%20V5

First, put a copy of the download into /usr/src
cp krb5-1.4-signed.tar /usr/src

Do this to unpack the download.
cd /usr/src
tar -xvf krb5-1.4-signed.tar

This extracts these two files:
krb5-1.4.tar.gz - the actual software
krb5-1.4.tar.gz.asc - a signature

Now do this to unpack the Kerberos software:
tar -xvzf krb5-1.4.tar.gz

Now build it.  By default, Kerberos will install the package's files
rooted 
at `/usr/local' as in `/usr/local/bin', `/usr/local/sbin', etc. 
(Pasted
from
the Installation Guide).  We will need this later on when we build
Samba.

cd /usr/src/krb5-1.4
cd src
./configure
make
make install

Some notes:

Make sure /etc/hosts has the FQDN of this system in place, similar to
below:

[root@infra-fw src]# more /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1               squidtest.infrasupportetc.com
localhost.localdomain localhost
10.10.10.2              squidtest.infrasupportetc.com

Test the build like this:

cd /usr/src/krb5-1.4/src
make check

Fix any problems it calls out and keep running until it finishes
cleanly.


************************************************************************
***************************
Now to build Samba from source to take advantage of the newest Kerberos

Download samba-3.0.13.tar.gz from here:
http://us4.samba.org/samba/

Put the saveset in the source directory:
cp samba-3.0.13.tar.gz /usr/src

Unpack it
cd /usr/src
tar -xvzf samba-3.0.13.tar.gz

Now build it with the Kerberos flavor installed earlier
cd /usr/src/samba-3.0.13/source
./configure --with-ads --with-krb5=/usr/local
make
make install


************************************************************************
**************************
Configure Samba to work with Kerberos

Set up smb.conf and krb5.conf.
(The paths are /usr/local/samba/lib/smb.conf and /etc/krb5.conf.)

(Extracted from the email Chris Cinnamo from Secure Computing sent.)

Edit the smb.conf 
---------------------------

smb.conf

realm = <YOUR DOMAIN> ex. support.com
workgroup = <DOMAIN> ex. support
security = ADS
encrypt passwords = yes
password server = 192.168.100.12



# idmap uid and idmap gid are aliases for
# winbind uid and winbid gid, respectively
idmap uid = 10000-20000
idmap gid = 10000-20000
winbind enum users = yes
winbind enum groups = yes



[test]
comment = Samba functionality test directory
path = /home/ryan/
read only = no
browsable = yes
writable = yes
guest ok = yes
valid users = @SUPPORT\"Domain Users"

-------------------------

krb5.conf
(Note that Kerberos uses realms named the same as the A/D domain name.
BUt --IMPORTANT--  the realm name must be in all UPPER CASE.  So
infrasupportetc.com becomes INFRASUPPORTETC.COM)

[logging]
 default = FILE:/var/log/krb5libs.log
 kdc = FILE:/var/log/krb5kdc.log
 admin_server = FILE:/var/log/kadmind.log

[libdefaults]
 default_realm = SUPPORT.COM
 dns_lookup_realm = false
 dns_lookup_kdc = false

[realms]
 SUPPORT.COM = {
  kdc = 192.168.100.12:88
  admin_server = 192.168.100.12:749
  default_domain = SUPPORT.com
 }

[domain_realm]
 .centralpower.com = SUPPORT.COM
 centralpower.com = SUPPORT.COM

#[kdc]
# profile = /var/kerberos/krb5kdc/kdc.conf

[appdefaults]
 pam = {
   debug = false
   ticket_lifetime = 36000
   renew_lifetime = 36000
   forwardable = true
   krb4_convert = false
 }


Add following entries in nssswitch.conf:

  passwd:        files winbind
  group:         files winbind

Samba uses a daemon called winbindd that handles the authentication
between Windows and Linux.
When a Windows system tries to look at a share on the Samba server, it
passes credentials.  
The Samba server needs to know where to look to validate the
credentials.  The above entries
tell the Samba server to first check the local passwd file and if not
there, then have Winbindd
look back in the Windows AD.  It turns out, there is more to the story.
In order for the Samba
server to have a clue how to tell winbindd what to do, we need to put
some Samba libraries in 
the right place.  As of 4/3/2005, the documentation in the
Samba-HOWTO-Collection is wrong.  
Use this script provided by Doug VanLeuven to set up the libraries:


#!/bin/sh

# Save this script in /home/gregs or someplace convenient.
# cd /usr/src/samba-3.0.13/source and run this script from there.

echo "Copying nsswitch modules to system library"

CWD=`pwd`

cd /lib
rm -f libnss_winbind.so libnss_winbind.so.1 libnss_winbind.so.2
rm -f libnss_wins.so libnss_wins.so.1 libnss_wins.so.2
cd /usr/lib
rm -f libnss_winbind.so libnss_wins.so

cd $CWD
cp -f nsswitch/libnss_winbind.so /lib
cp -f nsswitch/libnss_wins.so /lib

cd /lib
ln -sf libnss_winbind.so libnss_winbind.so.1
ln -sf libnss_winbind.so libnss_winbind.so.2
ln -sf libnss_wins.so libnss_wins.so.1
ln -sf libnss_wins.so libnss_wins.so.2

cd /usr/lib
ln -sf ../../lib/libnss_winbind.so libnss_winbind.so
ln -sf ../../lib/libnss_wins.so libnss_wins.so

/sbin/ldconfig



We need a place for log files.  The smb.conf template points here:
mkdir /var/log/samba

(Also look in the already existing directory, /usr/local/samba/var for
logfiles.)

Since we are building from source, we need a script to fire up the
daemons, like this:

#!/bin/sh
/usr/local/samba/sbin/nmbd
/usr/local/samba/sbin/smbd
/usr/local/samba/sbin/winbindd

Save this script someplace convenient, perhaps /firewall-scripts.

Now join this system to the Win2003 domain.  Here is an extract:

[root@infra-fw gregs]# /usr/local/samba/bin/net ads join -S 10.10.10.100
-U administrator
administrator's password: 
Using short domain name -- INFRASUPPORTETC
Joined 'SQUIDTEST' to realm 'INFRASUPPORTETC.COM'

Here are a few useful commands for testing:

kinit username@DOMAIN.SUFFIX	Use Kerberos to get a ticket (prompts
for password)
klist -e			Lists cached kerberos tickets

/usr/local/samba/bin/wbinfo -t	Check the trust relationship
/usr/local/samba/bin/wbinfo -g	Enumerate groups in the AD domain
/usr/local/samba/bin/wbinfo -u	Enumerate users in the AD domain

/usr/bin/ntlm_auth --username=[username]

This example will be useful later.  Squid will use this Samba program as
an authentication
helper.

[root@Stylmark-fw etc]# /usr/local/samba/bin/ntlm_auth --username=gregs
password: 
NT_STATUS_WRONG_PASSWORD: Wrong Password (0xc000006a)
[root@Stylmark-fw etc]# 
[root@Stylmark-fw etc]# 
[root@Stylmark-fw etc]# /usr/local/samba/bin/ntlm_auth --username=gregs
password: 
NT_STATUS_OK: Success (0x0)



************************************************************************
***************************
Now rebuild Squid
(The following modified from the explanation from Secure Computing Tech
Support)

cd /usr/local/squid/src/squid-2.5.STABLE7
./configure \
	--enable-smartfilter \
	--enable-async-io \
	--enable-linux-netfilter \
	--enable-underscores \
	--prefix=/usr/local/squid \
        --enable-auth="ntlm,basic" \
        --enable-external-acl-helpers="wbinfo_group" \
	--with-samba-sources=/usr/src/samba-3.0.13

make clean
make all
make install

For Samba 3.n, Squid will use the authentication helpers with Samba.  No
need to build any Squid
authentication helpers.  In fact, the squid FAQ says it won't work with
Samba 3.0.  See:
http://www.squid-cache.org/Doc/FAQ/FAQ-23.html#winbind

Put the following changes into /usr/local/squid/etc/squid.conf:

auth_param ntlm program /usr/local/samba/bin/ntlm_auth
--helper-protocol=squid-2.5-ntlmssp
auth_param ntlm children 30
auth_param ntlm max_challenge_reuses 0
auth_param ntlm max_challenge_lifetime 2 minutes

auth_param basic program /usr/local/samba/bin/ntlm_auth
--helper-protocol=squid-2.5-basic
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours

acl AuthorizedUsers proxy_auth REQUIRED
http_access allow all AuthorizedUsers


change group ownership for the Samba winbindd files:
chgrp squid /usr/local/samba/var/locks/winbindd_privileged -R

change file ownership on squid files:
cd /usr/local/squid
chown squid.squid * -R

create cache dirs and then start squid:
su squid

/usr/local/squid/sbin/squid -z

killall -name squid -9

/usr/local/squid/sbin/squid

-----------------------------------

from a pc logged into AD you should now be able to point ie to your
squid proxy
and NOT be prompted for username and password

-----------------------------------

On Mon, 2005-04-04 at 02:24 -0500, Greg Scott wrote:
> This turned into the mother of all system integration exercises and I
> **almost**  have it working.  
> I am trying to set up proxy authorization using:  
Your description of the IE login appears to be of a single dialog
'username' and 'password'.  You are only using NTLM if you have
a 3-
field dialog.

Look (using ethereal) and see if NTLM is offered - if not, then you have
a squid configuration problem.  Your squid config looks correct - ntlm
and basic (plaintext) auth must be configured separately, as they take
different helpers (or in the ntlm_auth case, different modes of the same
helper).

Andrew Bartlett

-- 
Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org
Student Network Administrator, Hawker College  http://hawkerc.net
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