Validating user's API credentials - Rails, ActiveMerchant, and PayPal Express Gateway

Question

I'm building a marketplace application that uses PayPal Express. I've got a form for sellers to input their PayPal API credentials, but I need a way to validate them by making some sort of call to PayPal.

I'm using the PaypalExpressGateway in ActiveMerchant, and I don't see anything other than the standard purchase controls. Is there any sort of null-operation that can be used?

Any help would be greatly appreciated!

Answer 1

For security reasons there isn't a way to check if the email is a valid paypal account. You can always make a small transaction and then void it if account validity is really required.

Answer 2

I am using the TransactionSearch operation for this purpose. By specifying STARTDATE=2100-01-01 00:00:00 it basically results in a no-op.

It will validate the credentials for you, without requiring any additional input from the seller.

Answer 3

I don't have the answer personally. But I know Ryan Bates of Railscasts.com has recently devoted six (!) episodes to ActiveMerchant and Paypal in particular. Check out episodes #141 through #146 at railscasts.com.

Answer 4

Ok, after 4 hours...

module ActiveMerchant #:nodoc:
  module Billing #:nodoc:
    class PaypalExpressGateway < Gateway

      def get_balance(options = {})
        commit 'GetBalance', build_get_balance_request(options)
      end

    private
      def build_get_balance_request(options)
        xml = Builder::XmlMarkup.new :indent => 2
        xml.tag! 'GetBalanceReq', 'xmlns' => PAYPAL_NAMESPACE do
          xml.tag! 'GetBalanceRequest', 'xmlns:n2' => EBAY_NAMESPACE do
            xml.tag! 'n2:Version', API_VERSION
            xml.tag! 'n2:ReturnAllCurrencies', '1'
          end
        end

        xml.target!
      end
    end
  end
end

class SellerMerchantValidator < ActiveModel::Validator
  def validate(record)
    paypal_attrs = ['paypal_api_username', 'paypal_api_password', 'paypal_api_signature']
    if record.paypal_merchant? && (record.changed - paypal_attrs).size < record.changed.size # one of paypal_attrs changed
      response = record.gateway.get_balance
      unless response.params['balance'].present?
        record.errors[:base] << "Please check the PayPal details and make sure all three are entered correctly."
      end
    end
  end
end

Thanks to Neils for the idea to check the TransactionSearch.

Please let me know if there is a better way to check if any of the api field changed.

Answer 5

There is also a call for GetBalance in the API. Some sample code

Looks like the simplest (and quickest?) way.

Answer 6

PayPal does have an AddressVerify API. It confirms whether a postal address and postal code match those of the specified PayPal account holder. I'm in the process of implementing it on our website right now, in fact.

You can read more about it here:
https://www.x.com/docs/DOC-1162#id0862M0QH02L

and here:
https://cms.paypal.com/us/cgi-bin/?&cmd=_render-content&content_ID=developer/e_howto_api_nvp_r_AddressVerify

Answer 7

Right, so if you want to test a user's credentials using ActiveMerchant, use the transaction_search method on the gateway

https://github.com/Shopify/active_merchant/blob/cb72e0f9c58f57b1293e6e976229b26cfbfee6a8/lib/active_merchant/billing/gateways/paypal/paypal_common_api.rb

This example will return a success (make sure to fill in your test credentials)

@username = ''
@password = ''
@signature = ''
gateway = ActiveMerchant::Billing::PaypalExpressGateway.new(
  login:      @username,
  password:   @password,
  signature:  @signature,
  test:       true
)

gateway.transaction_search({start_date: DateTime.now})