How to disabel TLS Version 1.0 Protocol on Exchange and OWA

jdff
jdff used Ask the Experts™
on
I need to patch an Exchange 2010/OWA server to pass a PCI compliance scan and they are asking to use TLS 1.1 or higher, so I found a script to disable TLS 1.0 and to enable TLS 1.1, however once I've disabled the TLS 1.0 many thing stooped working. Clients that were connecting via phone and using outlook anywhere from remote stoped working immediately. I have posted the script used below, but Am I missing anything here to make this work right? As you can see I've disabled only the TLS 1.0 server, because of some recommendations found online.

REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\SSL 2.0\Server" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\SSL 2.0\Client" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\SSL 3.0\Server" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\SSL 3.0\Client" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.0\Server" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.0\Client" /v Enabled /t REG_DWORD /d 1 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.0\Server" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.1\Client" /v Enabled /t REG_DWORD /d 1 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.1\Server" /v Enabled /t REG_DWORD /d 1 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.2\Client" /v Enabled /t REG_DWORD /d 1 /f
 
REG ADD "HKLM\System\CurrentControlSet\Control\SecurityProviders\SChannel\Protocols\TLS 1.2\Server" /v Enabled /t REG_DWORD /d 1 /f
 
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 128/128" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 40/128" /v Enabled /t REG_DWORD /d 0 /f
 
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\RC4 56/128" /v Enabled /t REG_DWORD /d 0 /f
Comment
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
You can have TLS 1.0, 1.1, and 1.2 all enabled at the same time. Can you live with that approach?  This will enable legacy devices and services.
Brian MurphySenior Information Technology Consultant

Commented:
Jdff-
I provide instructions, step-by-step, to do this:
http://www.experts-exchange.com/articles/25021/Citrix-SSL-TLS-Vulnerabilities-and-Operating-System-Hardening.html

I wrote this for Citrix servers and workstation but the tool, technique is Windows Operating system and anything running on Windows Operating System.

Take a read.  This is the process I use to harden the Windows OS relative to SSL/TLS protocols.

Author

Commented:
John, the PCI scan won't pass if TLS 1.0 I enabled, so I need to figure a way for this to work with TLS 1.1 or higher.
Ensure you’re charging the right price for your IT

Do you wonder if your IT business is truly profitable or if you should raise your prices? Learn how to calculate your overhead burden using our free interactive tool and use it to determine the right price for your IT services. Start calculating Now!

Author

Commented:
Brian,
My problem is that once TLS 1.0 was disabled, clients could not talk to the exchange server anymore, any  ideas?
Brian MurphySenior Information Technology Consultant

Commented:
Well, let me look through your script again but one point is the "tool" I recommend has a best practice option.  I'm wondering if you disabled more than just TLS 1.  Technically you need to disable SSL 2.0, 3.0, and TLS 1.0.  

I see where you disabled the RC4 ciphers as well and there is no reason to have those enabled.

At first glance it looks like you disabled all the right protocols and enabled TLS 1.1 and 1.2.

I don't see anything at 2nd glance that would cause your issue unless the firmware requires upgrading on your phones.

In the article I discuss how older versions of Internet browser or operating system is still a problem despite what you might do server side.

Can you share the phone information?

What I mean is the type of phone and OS.  Android? etc.
Senior Information Technology Consultant
Commented:
You might want to provide this link to your compliance team.

http://blogs.technet.com/b/exchange/archive/2015/07/27/exchange-tls-amp-ssl-best-practices.aspx

Get a short-term exception.

Quote
While we believe the intentions of both proposals are good and will promote adoption of TLS 1.1 & 1.2, at this time, we do not yet recommend disabling TLS 1.0 on your Exchange Server(s).
Brian MurphySenior Information Technology Consultant

Commented:
Basically MS is stating not to disable TLS 1.0 at this time.

With that said, hardening is more than TLS protocol.  Take a look at my article on hardening.

If you can go back with specific statements that you disabled the "bad ciphers" but need an exception for TLS 1.0 at this time you might get it between this MS article and the one I wrote on best practices.

http://blogs.technet.com/b/exchange/archive/2015/07/27/exchange-tls-amp-ssl-best-practices.aspx

http://www.experts-exchange.com/articles/25021/Citrix-SSL-TLS-Vulnerabilities-and-Operating-System-Hardening.html

Author

Commented:
Brian, this is the report form the PCI scan.

Port 443

CVSS 5.00 FAIL

Protocol TCP

Service www

Title

TLS Version 1.0 Protocol Detection (PCI DSS)

Synopsis:

The remote service encrypts traffic using a protocol with known weaknesses.

Impact:

The remote service accepts connections encrypted using TLS 1.0. These versions

of TLS reportedly suffer from several cryptographic flaws. An attacker may be able

to exploit these flaws to conduct man-in-the-middle attacks or to decrypt

communications between the affected service and clients. As per PCI Security

Standards Council April 1, 2015 document `Migrating from SSL and Early TLS` all

TLS 1.0 encryption usage must include a Mitigation and Migration plan detailing

current risk management plus migration strategy off early TLS to secure TLS

versions such as TLS 1.1 or 1.2 on or before June 30, 2016. Consult the

application's documentation for information on how to upgrade TLS to version 1.1

or greater (TLS 1.2 strongly recommended) or upgrade the application to a version

that uses TLS version 1.1 or greater.

Resolution:

Consult the application's documentation to disable TLS 1.0. Use TLS 1.1 or higher

instead. If you are using TLS 1.0 with a mitigation and migration plan in place, you

may contact support@securitymetrics.com to see if you are eligible to mark this

vulnerability as a false positive. For more information, see

https://www.pcisecuritystandards.org/documents/Migrating_from_SSL_Early_TLS_In

formation%20Supplement_v1.pdf
Brian MurphySenior Information Technology Consultant

Commented:
I understand.  Secure protocols like TLS generally use TCP 443.  However, per the Microsoft Exchange article:

You can do this with confidence because TLS 1.0 will be the minimum which you support. Exchange and Windows have both supported TLS 1.0 for over a decade. TLS 1.0 itself is not considered vulnerable when SSL 3.0 is disabled on clients and servers. In fact, most Exchange sessions already have been using TLS 1.0 or even later, for years. You are simply disabling the ability for the session to be downgraded to SSL 3.0. Disabling SSL 3.0 is typically not too impactful except for clients and devices that are older than (roughly) 10 years old.

http://blogs.technet.com/b/exchange/archive/2015/07/27/exchange-tls-amp-ssl-best-practices.aspx

I'm not convinced that upgrading or modifying your clients will solve this problem.

You have it in writing that Microsoft does not believe this to be an issue when you disable SSL.

If you monitor your traffic on the OWA server or a client device you will notice with Wireshark or other utilities they are using TLS 1.0.

A lot of the TLS 1.0 attacks are based on negotiation of "low ciphers" which you disabled.

You disabled RC4.  Those are the streaming ciphers mentioned in my article and referenced in Microsoft Article for TLS best practice.

Author

Commented:
Brian, I understand where are you coming from, however I was asked to make exchange and owa not to use TLS 1.0, so I have to keep on the search for answers, but thanks for your time.
Commented:
jdff -
You have done the correct configuration for the server.  The problem now lies with the many clients that do not support TLS1.1 and TLS1.2.  Those issues have to be managed on a client-by-client basis depending on platform, OS, and software being used.  You now have a properly configured server per PCI, and you are correct that most ASVs will NOT give you a pass on TLS1.0 unless you write a full mitigation plan, so you can't allow TLS1.0.  With your properly configured server you will see many failures that are due to client-side inability to use TLS1.1 or TLS1.2.

Author

Commented:
An exception was granted after an upgrade plan was submitted to Security Metrics.

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial