Apple Push Notifications

posted 7 years ago

So your app needs push notifications? Book a day, invest in a stress ball. Shoutout to Anthony Guay (@anthoprotic) for spending all morning on Xcode with me getting it to work!

Certificate Request

There's stuff online about this part, so just quickly:

  1. Open Keychain

  2. In the menu "Keychain Access" > "Certificate Assistant" > "Request A Certificate From A Certificate Authority"

  3. Enter email address & common name, click save to disk.

  4. In Keychain, select the private key under "keys" menu. Double-click export as a P12.

Convert And Submit

The certificate needs to be in plain-text (aka PEM) form.

Note: replace aps_development_4.cer with your certificate filename.

$ openssl x509 -in aps_development_4.cer -inform der -out cert.pem

Check it worked.

$ cat cert.pem
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----

Next convert the private key to plain-text as well. You need to specify a password. If you want, the password can be stripped later.

Note: replace appname.pk with your private key filename.

$ openssl pkcs12 -nocerts -in appname.pk -out key.pem
Enter Import Password: 
MAC verified OK

If you get the wrong password, just try again.

Mac verify error: invalid password?

You'll be prompted for the PEM pass phrase (password). Remember it.

Enter PEM pass phrase: ******
Verifying - Enter PEM pass phrase: ******

Register the key and cert with Apple's servers. It's a different url for production, this one is development.

$ openssl s_client -connect gateway.sandbox.push.apple.come:2195 \
       -cert cert.pem -key key.pem
Enter pass phrase for key.pem:
CONNECTED(00000003)
...
---

Type some chars and press enter, you'll exit from the command.

Prepare The App

  1. Open up Xcode and navigate to the project.

  2. Navigate to: "Provisioning Profiles" > "+ (new)" > "Development" > "Select App" > "Select Certificate" > "Select Device" > "Name Profile" > "Download"

  3. Open the .mobileprovision file in the downloads folder. Confirm add to library.

  4. Navigate to: "Project Navigator" > "Target" > "Build Settings" > "Code Signing" > "Provisioning Profile"

  5. Clean, Build, and Run

  6. Get your device token with the following code:

// AppDelegate.m

- (void)applicationDidFinishLaunching:(UIApplication *)application {
  // ...

  [[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound)];
}

- (void)application:(UIApplication *)application
didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken
{
    NSLog(@"application:didRegisterForRemoteNotificationsWithDeviceToken: %@", deviceToken);

    // Register the device token with a webservice
}

- (void)application:(UIApplication *)application
didFailToRegisterForRemoteNotificationsWithError:(NSError *)error
{
    NSLog(@"Error: %@", error);
}

The token should look like:

<6e9ea4cd ca021711 957b3bed 8cb3f1a7 243ce86f 4eb9e40b 847b775a ********>

Push With Houston

Combine the cert and key. Order is important.

$ cat cert.pem key.pem > appname.pem

Install the rubygem houston, which installs a command line tool apn.

$ gem install houston

Check out the options and usage.

$ apn push -h

Then push a notification!

$ token="<token here>"
$ apn push "$token" -c appname.pem -m "testing testing" -p
Password: *****
1 push notification sent successfully

If you get the following error, your password is wrong.

Exception sending notification: Neither PUB key nor PRIV key:: nested asn1 error

If you get the following error, you messed up the certificate and key process.

Exception: nested asn1 error

To strip the passphrase from the key:

$ mv key.pem key.bak.pem
$ openssl rsa -in key.bak.pem -out key.pem
Enter pass phrase for key.bak.pem:

Now you wont need to deal with the password aspect. Inspecting the source, the passphrase can also be set with the environment variable APN_CERTIFICATE_PASSPHRASE.

That should be it! Tweet @aj0strow if you run into trouble; hopefully I can help.