Fix for Connecting to OS X SMB Shares from Windows 10 – Updated

Please scroll to the bottom for the latest update on 18/3/2016.

Some people have run into difficulties connecting to SMB shares served by OS X servers running Open Directory.  I saw this phenomenon myself with a clients’ machine that was able to connect to the SMB share using a Local User account on the server, but when attempting the same connection with an OD Local Network User account the logs returned errors akin to not logging in to the correct domain.

After searching various online communities I found that a small group of people had run into this problem but no-one had sussed out a solution yet.  I banged my head against the wall for a while with this on the machine that was causing the problem without making any headway and then set up a new fresh VM of Windows 10 to test in my home lab setup.  To my surprise, the machine logged in to the SMB shares on my OS X Server machine without issue.

Comparing the fresh VM to the machine that failed to authenticate, I noticed some differences in Security Policy settings.  Many OS X admins who had Windows 7/8 machines that exhibited issues authenticating on earlier versions of OS X Server (10.7 mainly) used a set of “tweaks” to the Windows security policy to overcome these problems, and the client machine I was working with I suspect had these adjustments at an earlier point in it’s life.

The main “tweaks” were setting:

Network Security: LAN Manager Authentication Level to Send LM & NTLM -use NTLMv2 session if negotiated.

Network Security: Minimum session security for NTLM SSP Based (including secure RPC) Clients to unchecked (No Minimum).

I was re-pointed back to these settings via this site.

When examining the Local Security Policy on the fresh VM, I noticed that the first item, Network Security: LAN Manager Authentication Level, was set to Not Defined.

Returning to the problem machine, setting this item to Not Defined was not an available option but changing it to Send NTMLv2 response only did the trick.  The machine now authenticates to the SMB Share with OD Local Network User accounts without issue.

Step-by-Step Instructions

Press the Windows key and “R” together on the keyboard and enter secpol.msc in the run dialogue.

Navigate to Security Settings / Local Policies / Security Options.

Find Network Security: LAN Manager Authentication Level, and set it to Send NTLMv2 response only.

Finally, ensure that Network Security: Minimum session security for NTLM SSP Based (including secure RPC) Clients is set to Require 128-bit encryption.

These settings got my problem machine singing the right tune, hopefully it will help yours as well!

UPDATE – 18/3/2016

A few people have contacted me to say that this process is no longer working, and I have seen myself on the Home version of Win10 that you cannot access the secpol.msc applet to edit security policies.  Obviously, there have been many patches to both Windows 10 and OSX Server since this post was written back when 10 was first released.  Having just worked with an end user on this issue I thought I’d post an update with what worked for us on this Win10 Home machine.

Watching the log from the server I saw this on failed authentication:

Mar 18 11:39:10 digest-service[61066]: digest-request: user=MicrosoftAccount\\username
Mar 18 11:39:10 digest-service[61066]: digest-request: kdc failed with 36150275 proto=unknown
Mar 18 11:39:10 digest-service[61066]: digest-request: guest failed with -1561745590 proto=ntlmv2

So the Windows 10 client was forcing the OSX server to find the user’s account in an unknown domain called MicrosoftAccount.  Let’s say that the OSX server’s Open Directory domain is “OD-DOMAIN”.  I was able to get the user to authenticate correctly after clicking Use Another Account and entering “OD-DOMAIN\username” in the username field and then supplying the user’s password.

Mar 18 11:51:34 digest-service[61678]: digest-request od: ok user=OD-DOMAIN\\username proto=ntlmv2 flags: ENC_128, NEG_VERSION, NEG_TARGET_INFO, NEG_NTLM, NEG_SIGN, NEG_TARGET, NEG_UNICODE

I hope this helps somebody!


How to Create an Encrypted Disk Image on a Mac

Sometimes you share your Mac with other people without using separate user accounts, or sometimes you just need an extra secure place to keep some valuable information.  This guide will show you how to create a password-protected disk image file to keep your data in that is protected with encryption.

1. In your Applications folder find the Utilities folder and open Disk Utility

2. On the top of the Disk Utility window, click New Image.

Disk Utility

3. Name the image and choose the location you would like to save it, then set the image size (there are predefined sizes and you set any size at the bottom of the drop menu under Custom…).  Make sure you make your disk a size that is large enough to hold all the files you want to keep plus any anticipated expansion.

Create Image

4. Select the level of encryption you’d like to use.  128bit is generally a good compromise for security and quick access.  If you require the highest grade security, select 256bit.  256bit encryption will slow down read/write access to the files within your image.

5. For an image that will contain files you wish to edit you want to partition the disk formatted as a Hard Drive and keep the Format as read/write disk image.

6. Click Create and enter the password for the disk image in the following screen.

Password Dialogue

7. Now you will see the new image listed in the left pane of Disk Utility and also a removable disk icon on your desktop.  Double click on the disk and move any files you want to secure inside of it.


When finished, simply eject the disk to close and secure it.  When you want to access it again find the file where you saved it, double click it and enter your password.  The removable disk will now be loaded in your finder and you can access all your protected files again.