Verify IAP receipt from Windows Store using Ruby

Question

I am trying to verify receipt from Windows Store using Ruby. I'am using the xmldsig gem as follows:

certificate = OpenSSL::X509::Certificate.new(cert)
signed_document = Xmldsig::SignedDocument.new(xml)
signed_document.validate(certificate)

but it fails using the data taken from MS example (which is working in C#). Anyone had luck on using xmldsig to validate a Windows Store receipt?

Just for reference, these are the initialization for cert and xml vars:

xml = <<-XML
<?xml version="1.0"?>
<Receipt Version="1.0" CertificateId="A656B9B1B3AA509EEA30222E6D5E7DBDA9822DCD" xmlns="http://schemas.microsoft.com/windows/2012/store/receipt">
  <ProductReceipt PurchasePrice="$20.89" PurchaseDate="2012-11-30T21:32:07.096Z" Id="2f9c5c8f-3e1d-4fc7-a871-ac58f7e78053" AppId="3ec6cd9a-ca82-4d38-bfdf-ecafdb35a738" ProductId="Test" ProductType="Consumable" PublisherDeviceId="Test" MicrosoftProductId="59ef70aa-7099-4679-889e-f21919bfd2c6" />
  <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
    <SignedInfo>
      <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315" />
      <SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256" />
      <Reference URI="">
        <Transforms>
          <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
        </Transforms>
        <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256" />
        <DigestValue>FyFb1HGm+yeOIjt18M6TPD4Qzeu469vwDbQs7w72mdA=</DigestValue>
      </Reference>
    </SignedInfo>
    <SignatureValue>noct5CYBtRwBxVxkUeZIzeDyruLGVBqBMuFuBytpouPLACnQ5dbzdRvWX4XN67IUo0J2FW8DoYcMbf3sAS+PeKKV8SLnU+l8K1hWEbbbugHZezStTzwwkYcZuCTnAk7BYO0aiZWuXm9GiZGT9iyXsYtU1/u87L+llnVibU/m7gV8tD3vG0tVkjzV20C8666mHUsY/jxeq3ed7YY9CT0SDrh5PeL4ESaopBLcncHo/e6lcjyoKbO3e6YuIpsi8DVueeKNhpTlwa5yc0O3qzc5SGnT4Kbhj9NBEXf15/oTaLlg7lJhnQZ0mY+yR8vc4D0SkqD6e5Uc4u64hnu+g3Hphg==</SignatureValue>
  </Signature>
</Receipt>
XML

cert = <<-CERT
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
CERT

Answer 1

I can see that the digest value and signature are incorrect.

This is usually because of incorrect whitespace or the canonicalisation method.

The example code only verifies the signature. I'm convinced this includes the verification digest value. These are 2 separate steps.

I don't have a C# environment so I cannot verify the actual input of the validation.

I'm interested in the input for this statement:

signer.LoadXml((XmlElement)nodeList[0]);