applepay-php

applepay-php is a PHP extension that verifies and decrypts Apple Pay payment tokens according to Apple's spec[1]. It relies on OpenSSL for all crypto operations. Currently, it serves as the backbone for Etsy's PHP-based Apple Pay token handling endpoint.

Build

$ # Clone repo
$ git clone https://github.com/etsy/applepay-php.git
$ cd applepay-php
$
$ # Install OpenSSL development files (>= 1.0.2 required)
$ sudo yum install openssl-devel
$ # -or- sudo apt-get install libssl-dev
$ # etc...
$
$ # Build extension
$ phpize && ./configure && make
$
$ # Optionally install
$ sudo make install
$ echo 'extension=applepay.so' | sudo tee /etc/php.d/applepay.ini
$ # -or- echo 'extension=applepay.so' | sudo tee -a /etc/php.ini
$ # etc...

Pre-reqs

Before running the demo, you'll need a 'Payment Processing Certificate' and a private key from Apple (referred to as merch.cer and priv.p12 below). You can generate these at Apple's Dev Center. You'll also need an example payment token generated on an end-user device and the timestamp at which it was generated. An RSA-encrypted token should look like this:

{
    "data": "<base64>",
    "header": {
        "applicationData": "<hex_optional>"
        "wrappedKey": "<base64>",
        "publicKeyHash": "<base64>",
        "transactionId": "<hex>"
    },
    "signature": "<base64>",
    "version": "RSA_v1"
}

An ECC-encrypted token should look like this:

{
    "data": "<base64>",
    "header": {
        "applicationData": "<hex_optional>"
        "ephemeralPublicKey": "<base64>",
        "publicKeyHash": "<base64>",
        "transactionId": "<hex>"
    },
    "signature": "<base64>",
    "version": "EC_v1"
}

For more info check out the Apple Pay Programming Guide[2].

Demo

$ # Copy in your payment processing cert and test token
$ cd examples
$ cp /secret/place/merch.cer .
$ cp /secret/place/token.json .
$
$ # Extract private key from cert
$ openssl pkcs12 -export -nocerts -inkey merch.key -out priv.p12 -password 'pass:'
$
$ # Get intermediate and root certs from Apple
$ wget -O int.cer 'https://www.apple.com/certificateauthority/AppleAAICAG3.cer'
$ wget -O root.cer 'https://www.apple.com/certificateauthority/AppleRootCA-G3.cer'
$
$ # Verify chain of trust
$ openssl x509 -inform DER -in merch.cer -pubkey > pub.pem
$ openssl x509 -inform DER -in root.cer > root.pem
$ openssl x509 -inform DER -in int.cer > int_merch.pem
$ openssl x509 -inform DER -in merch.cer >> int_merch.pem
$ openssl verify -verbose -CAfile root.pem int_merch.pem # should output OK
$
$ # Run demo
$ cd ..
$ php -denable_dl=on -dextension=`pwd`/modules/applepay.so examples/decrypt.php -p <privkey_pass> -c examples/token.json -t <time_of_transaction>

If everything goes well you should see decrypted payment data.

Future work

• Split up library into libapplepay and a PHP wrapper
• HHVM port

[1] https://developer.apple.com/library/prerelease/ios/documentation/PassKit/Reference/PaymentTokenJSON/PaymentTokenJSON.html

[2] https://developer.apple.com/library/ios/ApplePay_Guide/