Pascal (Lazarus/Delphi)

Create/Verify XML Signature with External Text Reference

See more XML Digital Signatures Examples

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is a text file located at the following URL: https://www.chilkatsoft.com/helloWorld.txt Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.XmlDSigGen,
  Chilkat.StringBuilder,
  Chilkat.XmlDSig,
  Chilkat.Cert,
  Chilkat.Http,
  Chilkat.Xml;

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

procedure RunDemo;
var
  success: Boolean;
  xml: TXml;
  cert: TCert;
  gen: TXmlDSigGen;
  http: THttp;
  sbExternalTxt: TStringBuilder;
  bUsePrivateKey: Boolean;
  sbXml: TStringBuilder;
  verifier: TXmlDSig;
  sbExternalData: TStringBuilder;
  numRefs: Integer;
  i: Integer;
  bExternal: Boolean;
  uri: string;
  bVerified: Boolean;

begin
  success := False;

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

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

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

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

  cert := TCert.Create;

  success := cert.LoadPfxFile('qa_data/pfx/test_secret.pfx','secret');
  if (success = False) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  gen := TXmlDSigGen.Create;

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

  //  Get the content of the text data to be referenced.
  http := THttp.Create;
  sbExternalTxt := TStringBuilder.Create;
  success := http.QuickGetSb('https://www.chilkatsoft.com/helloWorld.txt',sbExternalTxt);
  if (success = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  success := gen.AddExternalTextRef('https://www.chilkatsoft.com/helloWorld.txt',sbExternalTxt,'utf-8',False,'sha256','');
  if (success = False) then
    begin
      WriteLn(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 := True;
  success := gen.SetX509Cert(cert,bUsePrivateKey);
  if (success <> True) then
    begin
      WriteLn(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 := TStringBuilder.Create;
  xml.GetXmlSb(sbXml);
  success := gen.CreateXmlDSigSb(sbXml);
  if (success <> True) then
    begin
      WriteLn(gen.LastErrorText);
      Exit;
    end;

  //  Examine the XML with the digital signature inserted
  WriteLn(sbXml.GetAsString());

  //  Here is the output:

  //  <?xml version="1.0" encoding="utf-8"?>
  //  <abc>
  //      <xyz>
  //          <name>helloWorld.txt</name>
  //          <url>https://www.chilkatsoft.com/helloWorld.txt</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/helloWorld.txt">
  //        <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
  //        <ds:DigestValue>f4OxZX/x/FO5LcGBSKHWXfwtSx+j1ncoSt3SABJtkGk=</ds:DigestValue>
  //      </ds:Reference>
  //    </ds:SignedInfo>
  //    <ds:SignatureValue>syFSl...pZDiFQ==</ds:SignatureValue>
  //    <ds:KeyInfo>
  //      <ds:X509Data>
  //        <ds:X509Certificate>MIIHAz...GwnUZWCaDE=</ds:X509Certificate>
  //      </ds:X509Data>
  //    </ds:KeyInfo>
  //  </ds:Signature></xyz>
  //  </abc>

  //  Let's verify the signature...
  verifier := TXmlDSig.Create;
  success := verifier.LoadSignatureSb(sbXml);
  if (success <> True) then
    begin
      WriteLn(verifier.LastErrorText);
      Exit;
    end;

  //  Let's examine the external references, and fetch the data for each..
  sbExternalData := TStringBuilder.Create;
  numRefs := verifier.NumReferences;
  i := 0;
  while i < numRefs do
    begin
      bExternal := verifier.IsReferenceExternal(i);
      if (bExternal = True) 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);
          if (success = False) then
            begin
              WriteLn(http.LastErrorText);
              Exit;
            end;

          success := verifier.SetRefDataSb(i,sbExternalData,'utf-8');
          if (success = False) then
            begin
              WriteLn(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(True);
  if (bVerified <> True) then
    begin
      WriteLn(verifier.LastErrorText);
      Exit;
    end;

  WriteLn('Signature verified!');


  xml.Free;
  cert.Free;
  gen.Free;
  http.Free;
  sbExternalTxt.Free;
  sbXml.Free;
  verifier.Free;
  sbExternalData.Free;

end;

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

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.