[squid-users] Squid/NTLM Auth

[Keith White]

I was able to confirm that ntlm_auth worked for the squid user.  We currently use BlueCoat proxies so IE is definitely configured to use integrated authentication. No cache_effective* in the config.  I will enable debugging and see what is happening as well as enable Kerberos.

Thanks,

Keith

-----Original Message-----
From: squid-users [mailto:squid-users-bounces at lists.squid-cache.org] On Behalf Of Amos Jeffries
Sent: Thursday, October 22, 2015 4:53 AM
To: squid-users at lists.squid-cache.org
Subject: Re: [squid-users] Squid/NTLM Auth

On 22/10/2015 8:21 a.m., Keith White wrote:
>
> I have squid running on Centos 7 and am trying to setup AD
> authentication. I have samba/winbindd installed and the system was
> added to the domain with authconfig. I have tested authentication with
> auth_ntlm and that works. I have also tested group membership with
> auth_ntlm and that works as well. When attempting to access squid with
> either IE or Firefox I am presented with the authentication dialog box.


If you have cache_effective_user or cache_effective_group directives in your config file remove them. They break the Winbind helpers group permissions.


Were your successful tests made using the Squid low-privileged user account ?
 If no, then your test results are not relevant. Re-test as the Squid user. Which will need membership of the winbindd_priv group.

What Windows version are the IE and Firefox being run on?
If it is newer than Windows 2000, then you should be moving to Negotiate/Kerberos authentication instead of NTLM.

Does the client machine have Windows Integrated Authentication enabled?
and is it on-domain?
 Off-domain machines have no chance of NTLM working. Disable their integrated authentication settings.
Note that without the integrated auth Firefox has no access to NTLM credentials and MSIE has a tendency to use the machine credentials instead of the users.



> Manually entering credentials does not work. What debugging can I
> enable to see what is going on? Squid is built with the following

<http://wiki.squid-cache.org/KnowledgeBase/DebugSections>

At least these:
  debug_options ALL,0 11,2 28,5 29,5


>
> Squid Cache: Version 3.5.9-20150917-r13917 Service Name: squid
> configure options:  '--prefix=/usr' '--includedir=/usr/include' '--datadir=/usr/share' '--bindir=/usr/sbin' '--libexecdir=/usr/lib/squid' '--localstatedir=/varsquid' '--sysconfdir=/etc/squid' '--enable-auth' '--enable-auth-ntlm' '--enable-external-acl-helpers' '--enable-auth-negotiate' '--enable-auth-basic' '--enable-auth-digest'
>
>
> relevant section from squid.conf
>
> auth_param ntlm program /usr/bin/ntlm_auth --diagnostics
> --helper-protocol=squid-2.5-ntlmssp
> auth_param ntlm children 5
> auth_param ntlm keep_alive on
> auth_param basic program /usr/bin/ntlm_auth --diagnostics
> --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

You should list Basic as first choice since it is the more secure of those two protocols.

Sounds like a joke, but it is true NTLM is less secure these days than Basic auth. Namely because clients that accept NTLM can be auto-downgraded by attackers to using LanMan protocols that broadcast the username and password just like Basic - BUT most network software treats Basic auth as the insecure one and do a lot more to protect its weak credentials.


>
> acl AuthorizedUsers proxy_auth REQUIRED http_access allow localnet
> http_access allow AuthorizedUsers http_access allow localhost

The above implies that the authenticated users will be outside the LAN (localnet). The 'L' in NTLM is "LAN" and old 1980-1990's style flat LAN networks are where it was designed for use. It does *not* work properly over Internet connections or even in many of todays complex LAN environments.

You need Negotiate/Kerberos auth for Internet clients to even have half a chance of authenticating securely. Then you also need to get the whole on/off domain thing sorted out and working.


PS. you will probably need a few hundred helpers for NTLM. It is an
*extremely* inefficient protocol. I've not seen even a home network operate with less than 50, usual minimum is 100.

Amos
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