What is a device signature error and how can you fix it on your Jamf Pro server?

The device signature error is a problem that could occur when trying to install an app or other software that requires a certain version of iTunes to be installed on your computer. Device signature errors can be fixed by installing a compatible version of iTunes that is listed in the Apple System Requirements for the app you are trying to install.
When trying to install an app using Jamf Pro that requires a certain version of iTunes, you may receive an error message telling you that the iTunes version installed on your computer is not compatible with the app. When this happens, the Jamf Pro server will no longer communicate with the iTunes application installed on your computer. This is due to Apple signing all versions of iTunes. You will likely receive an error message such as:
“The version of iTunes you are installing is not supported by this device. Installation cannot continue.”
or
“The operating system on this computer is not supported by this version of iTunes. This version of iTunes cannot be installed.”

Why did the device signature change and what does it mean for my organization’s security posture?

As of October 2017, the Apple Volume Purchase Program requires that the device signature change. This change was put into place to help prevent malicious users from compromising a computer and then using it to push out unauthorized updates to apps or other software. A device signature is essentially a unique identifier for an Apple computer. This unique identifier can be used to tell iTunes, the software that allows us to purchase apps and other software from the App Store, what version of iTunes we have. This can help both prevent users from downloading fake versions of iTunes or changes that malicious users would make to the default Apple settings in order to circumvent such restrictions. Please note that this change is a requirement for all Apple Volume Purchase Program computers and does not apply to any other versions of iTunes or MacOS.
How do I know if I have a device signature?
If you have the latest version of iTunes and iPhone Configuration Utility, you can check to see if your device has a device signature by following these steps:
1. Start up iPhone Configuration Utility, then click the name of your computer. If your computer does not appear in the drop-down menu, this means that it is not eligible for the Apple Volume Purchase Program (i.e. it is not a retail or education computer).
2. Under the “Products” tab, look for your device in the list of devices:
3. If you see your device listed, you can then click the “Signature” button to verify this information:

How can I create a new device signature for my devices and ensure that they’re compliant with my organization’s security policies?

a. Ensure that you have the current version of iTunes installed on your computer. You can download the latest version from https://www.apple.com/itunes/download/.
b. Locate the iTunes library folder on your computer. It is typically found in C:\Users\username\My Music\.
c. Copy the iTunes directory from your computer to the USB drive with more space and replace it with the old one in the primary folder of your iTunes library, or copy it to a different location on your hard drive if you want to keep it separate from your primary iTunes library.
d. Locate the UDID for your iPad and iPhone. The UDID is typically found in Settings -> “General” -> “About”
e. Connect the main iTunes USB hard drive to your Windows PC, and drag and drop the iTunes library onto your primary drive.
f. If you have multiple computers (Mac or PC), it is recommended that you copy over the iTunes library files to a USB hard drive on a computer that you don’t use much, such as a laptop computer.