(Go) Signed Zip as Base64 with XAdES-BES

This example is to help companies implement a solution for sending XAdES-BES to the Polish government for reporting purposes. Specifically:

Przed podpisaniem deklaracja zbiorcza (PIT-11Z, PIT-8CZ, PIT-40Z, PIT-RZ) musi zostać
umieszczona w archiwum ZIP. W tym przypadku, podpisywany jest plik archiwum ZIP,
przyjmujący w podpisie XAdES-BES formę zakodowaną base64.

The example demonstrates the following:

Zip an XML file (PIT-11Z.xml is zipped to PIT-11Z.zip)
Create XML to be signed, where the XML contains the base64 encoded content of the PIT-11Z.zip archive.
XAdES-BES sign the XML containing the base64 zip.

This example will also show the reverse:

Verify the signed XML.
Extract the PIT-11z.zip from the signed XML.
Unzip the PIT-11Z.zip to get the original PIT-11Z.xml

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    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Zip the PIT-11Z.xml to create PIT-11Z.zip (not as a .zip file, but in-memory).
    sbXmlToZip := chilkat.NewStringBuilder()
    success := sbXmlToZip.LoadFile("qa_data/xml/PIT-11Z.xml","utf-8")
    if success != true {
        fmt.Println("Failed to load the XML to be zipped.")
        sbXmlToZip.DisposeStringBuilder()
        return
    }

    zip := chilkat.NewZip()

    // Initialize the zip object. No file is created in this call.
    // It should always return true.
    success = zip.NewZip("PIT-11Z.zip")

    // Add the XML to be zipped.
    entry := zip.AppendString("PIT-11Z.xml",*sbXmlToZip.GetAsString())
    entry.DisposeZipEntry()

    // Write the zip to a BinData object.
    bdZip := chilkat.NewBinData()
    zip.WriteBd(bdZip)
    // The contents of the bdZip will be retrieved in base64 format when needed below..

    gen := chilkat.NewXmlDSigGen()

    gen.SetSigLocation("")
    gen.SetSigLocationMod(0)

    gen.SetSigId("Signature_2a8df7f8-b958-40cc-83f6-edb53b837347_19")
    gen.SetSigNamespacePrefix("ds")
    gen.SetSigNamespaceUri("http://www.w3.org/2000/09/xmldsig#")
    gen.SetSigValueId("SignatureValue_2a8df7f8-b958-40cc-83f6-edb53b837347_52")
    gen.SetSignedInfoId("SignedInfo_2a8df7f8-b958-40cc-83f6-edb53b837347_41")
    gen.SetSignedInfoCanonAlg("C14N")
    gen.SetSignedInfoDigestMethod("sha1")

    // Set the KeyInfoId before adding references..
    gen.SetKeyInfoId("KeyInfo_2a8df7f8-b958-40cc-83f6-edb53b837347_24")

    // Create an Object to be added to the Signature.
    object1 := chilkat.NewXml()
    object1.SetTag("xades:QualifyingProperties")
    object1.AddAttribute("xmlns:xades","http://uri.etsi.org/01903/v1.3.2#")
    object1.AddAttribute("Id","QualifyingProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_43")
    object1.AddAttribute("Target","#Signature_2a8df7f8-b958-40cc-83f6-edb53b837347_19")
    object1.UpdateAttrAt("xades:SignedProperties",true,"Id","SignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4e")
    object1.UpdateAttrAt("xades:SignedProperties|xades:SignedSignatureProperties",true,"Id","SignedSignatureProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_0a")
    // Chilkat will replace the strings "TO BE GENERATED BY CHILKAT" with actual values when the signature is created.
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningTime","TO BE GENERATED BY CHILKAT")
    // Note: It may be that http://www.w3.org/2001/04/xmlenc#sha256 is needed in the following line instead of http://www.w3.org/2000/09/xmldsig#sha1
    object1.UpdateAttrAt("xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningCertificateV2|xades:Cert|xades:CertDigest|ds:DigestMethod",true,"Algorithm","http://www.w3.org/2000/09/xmldsig#sha1")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningCertificateV2|xades:Cert|xades:CertDigest|ds:DigestValue","TO BE GENERATED BY CHILKAT")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedSignatureProperties|xades:SigningCertificateV2|xades:Cert|xades:IssuerSerialV2","TO BE GENERATED BY CHILKAT")
    object1.UpdateAttrAt("xades:SignedProperties|xades:SignedDataObjectProperties",true,"Id","SignedDataObjectProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4b")
    object1.UpdateAttrAt("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat",true,"ObjectReference","#Reference1_2a8df7f8-b958-40cc-83f6-edb53b837347_27")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:Description","MIME-Version: 1.0\r\nContent-Type: application/zip\r\nContent-Transfer-Encoding: binary\r\nContent-Disposition: filename=&quot;PIT-11Z.zip&quot;")
    object1.UpdateAttrAt("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:Identifier",true,"Qualifier","OIDAsURI")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:Identifier","http://www.certum.pl/OIDAsURI/signedFile/1.2.616.1.113527.3.1.1.3.1")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:Description","Opis formatu dokumentu oraz jego pelna nazwa")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:ObjectIdentifier|xades:DocumentationReferences|xades:DocumentationReference","http://www.certum.pl/OIDAsURI/signedFile.pdf")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:DataObjectFormat|xades:MimeType","application/zip")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:CommitmentTypeIndication|xades:CommitmentTypeId|xades:Identifier","http://uri.etsi.org/01903/v1.2.2#ProofOfApproval")
    object1.UpdateChildContent("xades:SignedProperties|xades:SignedDataObjectProperties|xades:CommitmentTypeIndication|xades:AllSignedDataObjects","")
    object1.UpdateAttrAt("xades:UnsignedProperties",true,"Id","UnsignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_55")

    // Emit XML in compact (single-line) format to avoid whitespace problems.
    object1.SetEmitCompact(true)
    gen.AddObject("",*object1.GetXml(),"","")

    // Create an Object to be added to the Signature.
    // This is where we add the base64 representation of the PIT-11Z.zip
    gen.AddObject("Object1_2a8df7f8-b958-40cc-83f6-edb53b837347",*bdZip.GetEncoded("base64"),"","http://www.w3.org/2000/09/xmldsig#base64")

    // -------- Reference 1 --------
    gen.AddObjectRef("Object1_2a8df7f8-b958-40cc-83f6-edb53b837347","sha1","C14N_WithComments","","")
    gen.SetRefIdAttr("Object1_2a8df7f8-b958-40cc-83f6-edb53b837347","Reference1_2a8df7f8-b958-40cc-83f6-edb53b837347_27")

    // -------- Reference 2 --------
    gen.AddObjectRef("SignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4e","sha1","","","http://uri.etsi.org/01903#SignedProperties")
    gen.SetRefIdAttr("SignedProperties_2a8df7f8-b958-40cc-83f6-edb53b837347_4e","SignedProperties-Reference_2a8df7f8-b958-40cc-83f6-edb53b837347_28")

    // Provide a certificate + private key. (PFX password is test123)
    cert := chilkat.NewCert()
    success = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
    if success != true {
        fmt.Println(cert.LastErrorText())
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        return
    }

    gen.SetX509Cert(cert,true)

    gen.SetKeyInfoType("X509Data")
    gen.SetX509Type("Certificate")

    // This will be an enveloping signature where the Signature element
    // is the XML document root, the signed data is contained within Object
    // tag(s) within the Signature.
    // Therefore, pass an empty sbXml to CreateXmlDsigSb.
    sbXml := chilkat.NewStringBuilder()

    // The Polish government's XmlDSig implementation requires that we reproduce an attribute-sorting error.
    // (This is an error in the XML canonicalization that is not noticed when both the signature-creation code and signature-verification code use
    // the same XML canonicalization implementation w/ the bug.)
    gen.SetBehaviors("AttributeSortingBug,CompactSignedXml")

    // Sign the XML...
    success = gen.CreateXmlDSigSb(sbXml)
    if success != true {
        fmt.Println(gen.LastErrorText())
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        sbXml.DisposeStringBuilder()
        return
    }

    // -----------------------------------------------

    // Save the signed XML to a file.
    success = sbXml.WriteFile("qa_output/signedXml.xml","utf-8",false)

    fmt.Println(*sbXml.GetAsString())

    // ----------------------------------------
    // Verify the signature we just produced...
    verifier := chilkat.NewXmlDSig()
    success = verifier.LoadSignatureSb(sbXml)
    if success != true {
        fmt.Println(verifier.LastErrorText())
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        sbXml.DisposeStringBuilder()
        verifier.DisposeXmlDSig()
        return
    }

    verified := verifier.VerifySignature(true)
    if verified != true {
        fmt.Println(verifier.LastErrorText())
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        sbXml.DisposeStringBuilder()
        verifier.DisposeXmlDSig()
        return
    }

    fmt.Println("This signature was successfully verified.")

    // ------------------------------------
    // Finally, let's extract the .zip from the signed XML, and then unzip the original PIT-11Z.xml from the in-memory zip.
    xml := chilkat.NewXml()
    xml.LoadSb(sbXml,true)

    // The base64 image of the PIT-11Z.zip is in the 2nd ds:Object child of the ds:Signature (the ds:Signature is the root element of the signed XML).
    // (ds:Object[0] would be the 1st ds:Object child.  Index 1 is the 2nd ds:Object child.)
    strZipBase64 := xml.GetChildContent("ds:Object[1]")

    bdZip.Clear()
    bdZip.AppendEncoded(*strZipBase64,"base64")
    if bdZip.NumBytes() == 0 {
        fmt.Println("Something went wrong.. we dont' have any data..")
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        sbXml.DisposeStringBuilder()
        verifier.DisposeXmlDSig()
        xml.DisposeXml()
        return
    }

    success = zip.OpenBd(bdZip)
    if success != true {
        fmt.Println(zip.LastErrorText())
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        sbXml.DisposeStringBuilder()
        verifier.DisposeXmlDSig()
        xml.DisposeXml()
        return
    }

    // Get the 1st file in the zip, which should be the PIT-11Z.xml
    entry = zip.GetEntryByIndex(0)
    if zip.LastMethodSuccess() != true {
        fmt.Println("Zip contains no files...")
        sbXmlToZip.DisposeStringBuilder()
        zip.DisposeZip()
        bdZip.DisposeBinData()
        gen.DisposeXmlDSigGen()
        object1.DisposeXml()
        cert.DisposeCert()
        sbXml.DisposeStringBuilder()
        verifier.DisposeXmlDSig()
        xml.DisposeXml()
        return
    }

    // Get the XML:
    origXml := entry.UnzipToString(0,"utf-8")
    fmt.Println("Original XML extracted from base64 zip:")
    fmt.Println(*origXml)

    entry.DisposeZipEntry()

    sbXmlToZip.DisposeStringBuilder()
    zip.DisposeZip()
    bdZip.DisposeBinData()
    gen.DisposeXmlDSigGen()
    object1.DisposeXml()
    cert.DisposeCert()
    sbXml.DisposeStringBuilder()
    verifier.DisposeXmlDSig()
    xml.DisposeXml()