Getting an iPhone UDID from Mobile Safari

Getting your app into beta tester’s hands is a pain. Even with new services like Test Flight the process is confusing and clunky for testers because the user has to login & it’s not entirely clear to the user what is going on.

The problem is, you need the person’s UDID & they have no idea what it is or how to find it.

Overview of Getting a UDID through Mobile Safari

Apple allows developers to get a person’s UDID (& do many other things) through a special interaction between the phone and your web server. Here’s an overview:

1. They click a link to a .mobileconfig XML file on your website
2. This pulls up their provisioning settings on their phone & offers them an ‘Install’ button (which they must press)
3. The phone sends the data you requested in encrypted XML to the URL you set in your .mobileconfig
4. You process the resulting data & show them a “thank you” web page

1) Your .mobileconifg

In this article I’m focused on getting a UDID. You can do many other things, but here is an example configuration for getting the UDID.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
    <dict>
        <key>PayloadContent</key>
        <dict>
            <key>URL</key>
            <string>http://yourwebsite.com/retrieve.php</string>
            <key>DeviceAttributes</key>
            <array>
                <string>UDID</string>
                <string>IMEI</string>
                <string>ICCID</string>
                <string>VERSION</string>
                <string>PRODUCT</string>
            </array>
        </dict>
        <key>PayloadOrganization</key>
        <string>yourwebsite.com</string>
        <key>PayloadDisplayName</key>
        <string>Profile Service</string>
        <key>PayloadVersion</key>
        <integer>1</integer>
        <key>PayloadUUID</key>
        <string>9CF421B3-9853-4454-BC8A-982CBD3C907C</string>
        <key>PayloadIdentifier</key>
        <string>com.yourwebsite.profile-service</string>
        <key>PayloadDescription</key>
        <string>This temporary profile will be used to find and display your current device's UDID.</string>
        <key>PayloadType</key>
        <string>Profile Service</string>
    </dict>
</plist>

You’ll need to fill in your own URL and PayloadUUID. The PayloadUUID doesn’t have to be generated in a special way – just make sure it is unique to your app.

Also make sure to register a file handler for .mobileconfig (content type application/x-apple-aspen-config).

2) The User Views Your Provision Profile

PayloadOrganization and PayloadDescription are shown to the user when they see the profile. In my description, I said something like “Press Install to continue…” since they may be confused on this screen.

You don’t have to sign your .mobileconfig, but if you don’t then they will see a warning that it is not signed (see below).

3) Receiving the Requested Data

QUIRK WARNING: For whatever reason, the process is EXTREMELY particulary about how your server responds when it sends the user to your preset URL. After many tries, I believe that your receiving url MUST be a .php file. This sounds nuts but I’m serious.

PHP was about the last language I wanted to work in, so I chose to redirect to a page that could handle it better.

<?php
  $data = file_get_contents('php://input');
  header("Location: http://www.mysite.com/Results?data=".rawurlencode($data));
?>

QUIRK WARNING:: The only way I (& others) have got it working is to redirect to a directory. I’ve tried to redirect to a .aspx page and it failed. If you do not get this right, then a vague error message will be shown to the user & they will be stuck. If you have a better explaination for this, please leave a comment below.

The page that you redirect to is the page that is shown to the user to end the process.

In my example, that page would receive a ‘data’ query string parameter containing the xml response from the phone.

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>IMEI</key>
    <string>12 123456 123456 7</string>
    <key>PRODUCT</key>
    <string>iPhone4,1</string>
    <key>UDID</key>
    <string>b59769e6c28b73b1195009d4b21cXXXXXXXXXXXX</string>
    <key>VERSION</key>
    <string>9B206</string>
  </dict>
</plist>

Other Helpful Links

Parsing the Response

Redirecting to a Directory