PayPal encrypted buttons (EWP)

impiastro · December 17, 2009, 11:25:19 am

I would like to share with you my experience of PayPal form data encryption.

In our new ecommerce website we are using the PayPal Payment module.
We were able to configure this module and use it in our orders management but we would like to secure the connection between our ecommerce and PayPal (PP) website.

We read about this possibility in the PP website, reading this document https://www.paypal.com/en_US/ebook/PP_WebsitePaymentsStandard_IntegrationGuide/encryptedwebpayments.html and also this one https://cms.paypal.com/us/cgi-bin/?&cmd=_render-content&content_ID=developer/e_howto_html_encryptedwebpayments#id08A3I0QC0X4__id08A3IL00L2L .

At the beginning it seems really simple but I was facing many problems during the entire process, so I decided to write some lines just to help anyone needs to encrypt his PP button using Java.

Download the bouncycastle distribution called crypto-144.zip from http://www.bouncycastle.org/latest_releases.html

Extract the files bcmail-jdk16-144.jar , bcpg-jdk16-144.jar , bcprov-jdk16-144.jar , bctest-jdk16-144.jar and putting them inside the web application classpath

Check if you are using a JRE JVM and not a JDK, we need in fact a directory called security inside the lib directory of the $JAVA_HOME path

Download the file jce_policy-6.zip from the Java download repository and extract its jar inside the directory security inside the lib directory of the $JAVA_HOME path

Generate the public/private key and the export certificate using the command "openssl"

Code Select



openssl genrsa -passout stdin -out my-prvkey.pem  1024 # write the password and press the enter key
openssl req -new -key my-prvkey.pem -x509 -days 365 -out my‑pubcert.pem
openssl pkcs12 -export -inkey my-prvkey.pem -in my‑pubcert.pem -out my-prvkey.p12

Upload the file my-pubcert.pem to https://www.paypal.com/us/cgi-bin/webscr?cmd=_profile-website-cert (you need an account to PayPal) and save the certificate ID

Download the file java.zip from https://www.paypal.com/us/cgi-bin/webscr?cmd=p/xcl/rec/ewp-code (you need an account to PayPal) and extract the file ClientSide.java putting it inside your application (or inside a jar in your application).

Generate the encrypted button string using the following code

Code Select

 
                ... 
                String buttonString = null;

		if (pDetails != null) {
			NameValue[] parameters = pDetails.getParameters();

			if (parameters != null) {
				String data = "";
				int i = 0;
				for (NameValue parameter : parameters) {
					if (i > 0) {
						data += ",";
					}

					String value = parameter.getValue();
				
					data += parameter.getName() + "=" + value;

					i++;
				}
				data += ",cert_id=" + certId;

				try {
					Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

					String keyPath = privateCertPkcs12Path;
					String certPath = publicCertPath;
					String paypalCertPath = paypalPublicCertPath;
					String keyPass = privateCertPass;

					buttonString = ClientSide.getButtonEncryptionValue(data, keyPath, certPath, paypalCertPath, keyPass);
				} catch (Exception ppe) {
					ppe.printStackTrace();
				}
			}
		}

Where pDetails is the PaymentDetails object from your order, certId is the certificate ID of your public certificate generated by PayPal and privateCertPkcs12Path , publicCertPath , paypalPublicCertPath are the path to your private and public certificate and the paypal public certificate and privateCertPass is your private certificate password.

Create a form using this syntax (velocity)

Code Select


                <form action="$order.getPaymentDetails().requestUrl" method="$order.getPaymentDetails().postOrGet">

			<input type="hidden" name="cmd" value="_s-xclick">
			<input type="hidden" name="encrypted" value="$buttonString">

			<input type="image" src="https://www.paypal.com/en_US/i/btn/x-click-but23.gif" border="0" name="submit" style="width: 68px; border-width: 0px;">
		</form>

Remember that a certificate lasts for a year, so you must repeat the certificate generation steps before this deadline.

Now you can see something like this:

Code Select



<form method="post" action="https://www.sandbox.paypal.com/cgi-bin/webscr">

			<input type="hidden" value="_s-xclick" name="cmd"/>
			<input type="hidden" value="-----BEGIN PKCS7-----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25uerqrzISm5gC1fylpmuzEyXcrvzmckWWf4RMicNPfo0/D4HAboSFA74ll95AOa
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ddqwaZ2FOFWfahCz6r1wi+MInPqBHAnURViZlrGs6QGDAk9acJhyn7//4UI7LJi1
Y2Y+N/dGzgRQteGJk60l74y+AXYP1JjuUsvAltd3H1XsySe0uPa932l1R189TSK5
HDh1P7AVNY3bnbGXwmPGNSP5/8zEY9eT5TbeuI9pIaDTFHLD5AXxjMfWJWbC/WYz
t314uZRCNL8WPyV3WIYvUBqFTYPNiLFTPvefqvgbvb2UGYVHZVE5/9pxE9Sn26sQ
n/pSnIe+dZbSEx0IReSbTwIGiY5fcNlbjzRTsLYvAAAAAAAAAAAAAAA=
-----END PKCS7-----
" name="encrypted"/>

			<input type="image" border="0" style="border-width: 0px; width: 68px;" name="submit" src="https://www.paypal.com/en_US/i/btn/x-click-but23.gif"/>
					</form>

If everything is ok PayPal should decrypt your "encrypted" variable and show the correct infos to the purchaser.

KonaKart Community Forum

PayPal encrypted buttons (EWP)

impiastro

December 17, 2009, 11:25:19 am