(Delphi ActiveX) Create XML Signature with External XML Reference

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is an XML file located at the following URL: https://www.chilkatsoft.com/data/helloWorld.xml

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
xml: TChilkatXml;
cert: TChilkatCert;
success: Integer;
gen: TChilkatXmlDSigGen;
http: TChilkatHttp;
sbExternalXml: TChilkatStringBuilder;
bUsePrivateKey: Integer;
sbXml: TChilkatStringBuilder;
verifier: TChilkatXmlDSig;
sbExternalData: TChilkatStringBuilder;
numRefs: Integer;
i: Integer;
bExternal: Integer;
uri: WideString;
canonXml: WideString;
bVerified: Integer;

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

// This example inserts an XML signature in the following XML:

// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <abc>
//   <xyz>
// 	<name>helloWorld.xml</name>
// 	<url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
//   </xyz>
// </abc>

// Build the above XML to be signed.
xml := TChilkatXml.Create(Self);
xml.Tag := 'abc';
xml.UpdateChildContent('xyz|name','helloWorld.xml');
xml.UpdateChildContent('xyz|url','https://www.chilkatsoft.com/data/helloWorld.xml');

cert := TChilkatCert.Create(Self);

success := cert.LoadPfxFile('qa_data/pfx/test_secret.pfx','secret');
if (success = 0) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

gen := TChilkatXmlDSigGen.Create(Self);

// Indicate the location within the XML the Signature will be inserted.
gen.SigLocation := 'abc|xyz';

// Get the content of the XML data to be referenced.
http := TChilkatHttp.Create(Self);
sbExternalXml := TChilkatStringBuilder.Create(Self);
success := http.QuickGetSb('https://www.chilkatsoft.com/data/helloWorld.xml',sbExternalXml.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

success := gen.AddExternalXmlRef('https://www.chilkatsoft.com/data/helloWorld.xml',sbExternalXml.ControlInterface,'sha256','EXCL_C14N','');
if (success = 0) then
  begin
    Memo1.Lines.Add(gen.LastErrorText);
    Exit;
  end;

// Provide the private key for signing via the certificate, and indicate that
// we want the base64 of the certificate embedded in the KeyInfo.
gen.KeyInfoType := 'X509Data';
gen.X509Type := 'Certificate';

bUsePrivateKey := 1;
success := gen.SetX509Cert(cert.ControlInterface,bUsePrivateKey);
if (success <> 1) then
  begin
    Memo1.Lines.Add(gen.LastErrorText);
    Exit;
  end;

// Indicate we want an indented signature for readability.
// This can be removed after debugging is finished..
gen.Behaviors := 'IndentedSignature';

// Now create and insert the Signature
sbXml := TChilkatStringBuilder.Create(Self);
xml.GetXmlSb(sbXml.ControlInterface);
success := gen.CreateXmlDSigSb(sbXml.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(gen.LastErrorText);
    Exit;
  end;

// Examine the XML with the digital signature inserted
Memo1.Lines.Add(sbXml.GetAsString());

// Here is the output:

// <?xml version="1.0" encoding="utf-8"?>
// <abc>
//     <xyz>
//         <name>helloWorld.xml</name>
//         <url>https://www.chilkatsoft.com/data/helloWorld.xml</url>
//     <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
//   <ds:SignedInfo>
//     <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
//     <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
//     <ds:Reference URI="https://www.chilkatsoft.com/data/helloWorld.xml">
//       <ds:Transforms>
//         <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
//       </ds:Transforms>
//       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
//       <ds:DigestValue>H/s775OZhel6wdBhe02l4LK6m0lkplOisKxAbVwWxp0=</ds:DigestValue>
//     </ds:Reference>
//   </ds:SignedInfo>
//   <ds:SignatureValue>UruwnBqh..Ll4IzUA==</ds:SignatureValue>
//   <ds:KeyInfo>
//     <ds:X509Data>
//       <ds:X509Certificate>MIIHAz...nUZWCaDE=</ds:X509Certificate>
//     </ds:X509Data>
//   </ds:KeyInfo>
// </ds:Signature></xyz>
// </abc>

// Let's verify the signature...
verifier := TChilkatXmlDSig.Create(Self);
success := verifier.LoadSignatureSb(sbXml.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(verifier.LastErrorText);
    Exit;
  end;

// Let's examine the external references, and fetch the data for each..
sbExternalData := TChilkatStringBuilder.Create(Self);
numRefs := verifier.NumReferences;
i := 0;
while i < numRefs do
  begin
    bExternal := verifier.IsReferenceExternal(i);
    if (bExternal = 1) then
      begin
        uri := verifier.ReferenceUri(i);

        // We're assuming the URI is an https:// or http:// URL...
        // Let's also assume we know that the referenced data is text and we want the utf-8 byte representation.
        sbExternalData.Clear();
        success := http.QuickGetSb(uri,sbExternalData.ControlInterface);
        if (success = 0) then
          begin
            Memo1.Lines.Add(http.LastErrorText);
            Exit;
          end;

        // Because the referenced external data was explicitly XML, it was the canonicalized XML that was digested.
        // We need to canonicalize the XML in the same way as when signed.
        canonXml := verifier.CanonicalizeXml(sbExternalData.GetAsString(),'EXCL_C14N',0);
        sbExternalData.SetString(canonXml);

        success := verifier.SetRefDataSb(i,sbExternalData.ControlInterface,'utf-8');
        if (success = 0) then
          begin
            Memo1.Lines.Add(verifier.LastErrorText);
            Exit;
          end;
      end;
    i := i + 1;
  end;

// Now that we have the external data available, we can verify the reference digest(s) and the signature.
bVerified := verifier.VerifySignature(1);
if (bVerified <> 1) then
  begin
    Memo1.Lines.Add(verifier.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Signature verified!');
end;