Systems Engineering – Page 3

like_escape() is Deprecated in WordPress 4.0

Plugin authors and website developers who work with WordPress database queries should notice an important change coming in WordPress 4.0.

The function like_escape() is no longer used in WordPress core code. It is still available as a deprecated function, so it still works in any existing plugins that rely on it. However, a new and different function is available that should be used in all new code.

Deprecated means that anyone using code that calls like_escape() with WP_DEBUG enabled will see an error message. If WP_DEBUG_LOG is also enabled, the error message will appear in the /wp-content/debug.log file.

Let’s look at an example of core code where I removed like_escape() and implemented the new function $wpdb->esc_like().

3.9 Old Style

$search_orderby_s = like_escape( esc_sql( $q['s'] ) );

$search_orderby .= "WHEN $wpdb->posts.post_title LIKE '%{$search_orderby_s}%' THEN 1 ";

What did this do? It was an old snippet from /wp-includes/query.php that set up a search for post titles. The input $q['s'] was escaped using two functions before it was added to the post_title LIKE expression. Now let’s see how I replaced that snippet in the next version.

4.0 New Style

$like = '%' . $wpdb->esc_like( $q['s'] ) . '%';

$search_orderby .= $wpdb->prepare( "WHEN $wpdb->posts.post_title LIKE %s THEN 1 ", $like );

Continue reading like_escape() is Deprecated in WordPress 4.0

Folder Redirection Broken After GPO Changes

I am learning quite a bit about the Windows 2012 environment thanks to a recent server migration. The biggest lesson so far deals with Folder Redirection, and the effects of repeated adjustments to the GPO settings.

Under certain circumstances, folder redirection seems to get “stuck” showing either an old folder path or none at all when the user goes looking for their documents. The Group Policy Results tool seems to confirm that the Folder Redirection settings are not being applied at all for the user/computer profile that is stuck. Frustratingly, I couldn’t find any problem with my Group Policy configuration.

No amount of logging off and on, adjusting permissions, or messing with Group Policy seems to have any effect.

In the end, I was able to clear up the problem by running this command:

gpupdate /Target:User /Force /Logoff

The key here is the Force option, which successfully resets the folder redirection policy for that user profile, and perhaps all the profiles on that particular computer. Problem solved! Windows 8.1, Windows 2012, and possibly other versions are affected.

16-bit Color Limitation in RDP

GPO Editor showing the path to the color policy. — This Policy Needs to be Enabled

If you’ve ever been under the mistaken impression that the RDP client controls the color settings for remote connections, then you came to the right place for help.

Windows XP and Windows 2003 servers won’t show more than 16-bit color depth to RDP clients requesting 24-bit or better color. You can confirm this by looking at the display settings in the control panel of the remote server. As a result, black text looks like funny shades of purple, photos look slightly posterized, and any color-critical tasks may be impossible to accomplish by remote control.

To fix this problem, you must enable the following policy:

Computer Configuration > Administrative Templates > Windows Components > Terminal Services > Limit maximum color depth

Set the Color Depth field to 24 bit and click OK.

I can’t explain why Windows would be limited in this way by default, but it is.

Microsoft Updates Crippling Windows 2003 Servers

The updates bug I described in Windows XP back in October is now also locking up server computers.

I’ve had it with this. Microsoft has clearly lost control of its security patches.

As of today, I am disabling Automatic Updates across the board; all devices and all versions. Up-time is more important to me than monthly patches.

Microsoft Updates Crippling Windows XP

Screen shot of the related Neowin article — Check out the comments on this website.

As reported at Neowin, your Windows XP computer may be locked up due to bad updates being sent by Microsoft. Two of mine were 🙁

The solution, which I found in the comments section of that article, tested, and confirmed on my own computers:

Disable the Automatic Updates service.
Stop the Automatic Updates service (reboot if necessary but do not kill svchost.exe)
Install the correct update from Microsoft. That link is for computers with IE8 only. For older versions, check the article I mentioned above.
Reboot the computer.
Reset the Automatic Updates service to automatic and start it. (If you want more updates.)

This is a truly shameful problem for Microsoft’s reputation.

December 7, December 11, More Problems

The subsequent updates released by Microsoft have caused the same problem to occur again. I’ve updated the link above with the newer patches.

To find newer patches, you have to do a complicated search at the Microsoft Download Center.

Per my latest article about Windows servers, I am now recommending everyone disable the Automatic Updates service on all Windows-based computers.

MySQL Password Errors

Since August 12 (about two weeks now), I was getting this error from the MySQL program mysqldump:

Warning: Using unique option prefix pass instead of password is deprecated and will be removed in a future release. Please use the full name instead.

I’m not sure what changed or what got upgraded, but I was able to track down the problem. It has nothing to do with command syntax.

In the account directory, which is the one with the account name, one level above public_html, or just “~” on the command line, I found a file named “.my.cnf” with the “pass=” option in it.

To fix the problem, find that file and change “pass=” to “password=”.

I have also forwarded this information to the BlueHost help desk.

Client Certificate Authentication in IIS 6

Client certificates are a cool technology that, once setup, eliminate the need to use your password on your own website from your own devices.

This article wont run through the entire procedure for setting up a web server, Windows domain, file permissions, server certificates, or a certificate authority. I just want to convey some of the configuration pitfalls that exist in IIS 6.

Step 1: Enable Client Certificate Mapping

The IIS Secure Communciations dialog box — Start with these settings.

Continue reading Client Certificate Authentication in IIS 6

PHP Array Assignment and References

This is a quick explanation of some more referencing quirks in PHP.

Let’s say you need to store an array in a specific variable so that another variable can be freed up and overwritten with different information. [To clarify, this array may be very large and copying it would be detrimental to performance in this particular application. For small arrays, copying and not referencing may be preferable.]

The operation for referencing the array with a new variable is quite simple:

$array_goes_here =& $need_to_free_up_this_var;

The code above will reference the array to prevent PHP from making an unnecessary copy of the whole thing.

Now here’s what you have to avoid:

$need_to_free_up_this_var = array(); /* wrong! */

Continue reading PHP Array Assignment and References

How to Secure iPad VPN with Windows L2TP

VPN diagram showing both Windows and iPad remote clients. — Different protocols for different clients.

Back in August, I mentioned the importance of disabling most versions of PPTP for security reasons, and included my own tutorial for How to Secure a Windows VPN with PEAP. That solution works great for Windows, but is not compatible with iPads.

Now I will offer a solution that works great for iPad, but may not work on Windows computers. In addition, I will explain how to get the two solutions to work together securely so that both Windows and iPad computers will be able to connect to a Windows VPN simultaneously without using the insecure versions of PPTP.

The Layer 2 Tunneling Protocol (L2TP) is an obvious choice for the iPad because it is the only supported protocol other than the insecure PPTP option. On the server side, however, there are some implementation nuances that could easily discourage the use of L2TP. I took the time to research L2TP in more depth before writing this article, because I felt that a generic recommendation could leave readers totally confused about the security issues involved. So before delving into a new tutorial, I want to explain two new concepts: L2TP Pre-Shared Key, and L2TP NAT Traversal.

NAT Traversal could be a major concern for any L2TP implementation, because Microsoft wrote a very technical and rather intimidating knowledge base article called IPSec NAT-T is not recommended for Windows Server 2003 computers that are behind network address translators. If you’ve seen that article, I want to assure you that the Microsoft recommendation is not relevant here.

A careful reading of the Microsoft recommendation against NAT-T will reveal that the underlying security problem with NAT-T is not a server problem but a client problem. In other words, Microsoft recommends that Windows XP computers not attempt to use NAT-T to connect to privately-addressed servers. The Windows 2003 server itself fully supports NAT-T out of the box and doesn’t even need to be configured to use it. This is perfect for iPad users, because iPad also supports NAT-T out of the box, and this almost eliminates the address translation challenges of using L2TP.

Continue reading How to Secure iPad VPN with Windows L2TP

UPS Replacement and APCUPSD for Windows

After replacing a UPS device, Windows may automatically delete the APCUPSD USB driver. When the computer boots up, the tray icon status will say “Network Error” and three errors will be logged in the Windows Event Viewer.

To restore APCUPSD to online status, simply re-install the USB driver by following the manual installation instructions. That information can be found in the program directory. For example, C:\Program Files\apcupsd\driver\install.txt In a nutshell, you need to look in the system’s Device Manager. If there is an item in the Human Interface Devices group named “American Power Conversion USB UPS” then the desired driver is missing. Right click that item, click “Update driver” and then pick the correct driver.

After restoring the driver, restart the APCUPSD service by using the “Start Apcupsd” shortcut in the Start menu, or by using the Services administrative tool.

Continue reading UPS Replacement and APCUPSD for Windows