Pascal (Lazarus/Delphi)

Verify XML Signature with External Data Reference

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

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.Http,
  Chilkat.StringBuilder,
  Chilkat.BinData,
  Chilkat.XmlDSig;

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

procedure RunDemo;
var
  success: Boolean;
  url: string;
  http: THttp;
  sbXml: TStringBuilder;
  verifier: TXmlDSig;
  refUri: string;
  jpgData: TBinData;
  bVerified: Boolean;

begin
  success := False;

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

  //  The XML containing the Signature to be verified contains the following:
  //  <?xml version="1.0" encoding="UTF-8" standalone="no"?>
  //  <abc>
  //    <xyz>
  //      <jpg>
  //          <name>starfish.jpg</name>
  //          <url>https://www.chilkatsoft.com/images/starfish.jpg</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/images/starfish.jpg"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>MbHOti6nOh9DJP/u7u1+a1u0wRYIGEdaAVk5ehxqeBhcR4qvGvCQ7wLxcfDuwFG2grSg43ANxDYngLqZTeFb5nCfywcuNBQI8FrNRVY5hkyv6kDW1BVN8ot9qPYX9oHxJp1e+nMszIiSxqHX3XDI7YnvFt/0CyeO5JaQQEzXzIwqqb8iUNcH/bJzR6CrTf1hGuQ5MPorG0bRwbYPPHHzipUqHBinK8VbHobnxL7GQHAhR8k9gDD35kZcMxf/74U7pGO19ZzTbdJW5S7q4bVVxvsuU3itTbhHI60pOE14ibrjZtIrPZLVUD3TQqIIF04TChW2NXdYOo3+ij4ZnP8x+g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
  //    </xyz>
  //  </abc>

  //  The above XML is available at https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml
  //  First fetch the XML..

  url := 'https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml';
  http := THttp.Create;
  sbXml := TStringBuilder.Create;
  success := http.QuickGetSb(url,sbXml);
  if (success <> True) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  verifier := TXmlDSig.Create;

  //  Load the XML containing the signatures to be verified.
  //  Note that this particular Signature already contains the RSA public key that will be used
  //  for verification.
  success := verifier.LoadSignatureSb(sbXml);
  if (success <> True) then
    begin
      WriteLn(verifier.LastErrorText);
      Exit;
    end;

  //  Get the Reference URI, which in this case is the URL to the binary data that was hashed.
  //  This fetchs the URI attribute value from:  <ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg">
  refUri := verifier.ReferenceUri(0);
  if (verifier.LastMethodSuccess <> True) then
    begin
      WriteLn('No reference URI found.');
      Exit;
    end;

  //  Download the JPG data to be verified.
  jpgData := TBinData.Create;
  success := http.QuickGetBd(refUri,jpgData);
  if (success <> True) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  //  Provide the JPG data to the verifier
  verifier.SetRefDataBd(0,jpgData);

  //  Verify the signature
  bVerified := verifier.VerifySignature(True);
  WriteLn('Signature verified = ' + bVerified);


  http.Free;
  sbXml.Free;
  verifier.Free;
  jpgData.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.