(Delphi DLL) Verify XML Digital Signature having KeyName

Demonstrates how to verify an XML digital signature where the KeyInfo part contains the KeyName element.
In this case, the public key is not specifically stored in the signed XML.
Rather, application specific information about the key is stored in the KeyName element.
This example uses the KeyName to find and matching public key.

This example requires Chilkat v9.5.0.69 or greater.

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Chilkat non-ActiveX DLL for Delphi

Chilkat ActiveX DLL for Delphi

* The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Http, StringBuilder, PublicKey, Xml, XmlDSig;

...

procedure TForm1.Button1Click(Sender: TObject);
var
url: PWideChar;
http: HCkHttp;
sbXml: HCkStringBuilder;
success: Boolean;
verifier: HCkXmlDSig;
xmlKeyInfo: HCkXml;
sbKeyName: HCkStringBuilder;
pubKey: HCkPublicKey;
bVerified: Boolean;

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

// The signed XML to be verified in this example contains the following:
// 
// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <Envelope>
//   <Header>
//     <Security>
//     <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/2009/xmldsig11#dsa-sha256"/><ds:Reference URI="#abc"><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>XTjDIHSEsDNTO9yn4cKtyXjRUjPFXkOQOLYI5mueZhk=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>NXOIMevGCqFl0Dwtp2KkqkT05GRV8CjmHZ9LhFpt8/d7+lkIi7mITA==</ds:SignatureValue><ds:KeyInfo><ds:KeyName>dsaKey_123</ds:KeyName></ds:KeyInfo></ds:Signature></Security>
//   </Header>
//   <Body Id="abc">
//     <z:FooBar xmlns:z="https://www.example-code.com"/>
//   </Body>
// </Envelope>
// 

// The above XML is available at https://www.chilkatsoft.com/exampleData/signedUsingKeyName.xml
// First we'll fetch the signed XML:

url := 'https://www.chilkatsoft.com/exampleData/signedUsingKeyName.xml';
http := CkHttp_Create();
sbXml := CkStringBuilder_Create();
success := CkHttp_QuickGetSb(http,url,sbXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

verifier := CkXmlDSig_Create();

// Load the XML containing the signature to be verified.
success := CkXmlDSig_LoadSignatureSb(verifier,sbXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkXmlDSig__lastErrorText(verifier));
    Exit;
  end;

// (The Chilkat XML Digital Signature API has the capability to handle XML documents with multiple signatures.
// We know in advance that this signed XML has just one Signature, so we leave the dsig.Selector property at the
// default value of 0.)

// Let's get the KeyInfo XML so we can then get the KeyName.
xmlKeyInfo := CkXmlDSig_GetKeyInfo(verifier);
if (CkXmlDSig_getLastMethodSuccess(verifier) = False) then
  begin
    Memo1.Lines.Add('There is no KeyInfo available in the Signature.');
    Exit;
  end;

// Examine the XML:
Memo1.Lines.Add(CkXml__getXml(xmlKeyInfo));

// The KeyInfo XML that is returned looks like this:
// 
// 	<ds:KeyInfo>
// 	    <ds:KeyName>dsaKey_123</ds:KeyName>
// 	</ds:KeyInfo>
// 

// Get the KeyName.
sbKeyName := CkStringBuilder_Create();
CkStringBuilder_Append(sbKeyName,CkXml__getChildContent(xmlKeyInfo,'*:KeyName'));
CkXml_Dispose(xmlKeyInfo);

// sbKeyName contains "dsaKey_123"
Memo1.Lines.Add(CkStringBuilder__getAsString(sbKeyName));

// The application now locates and loads the public key for verification
// based on the key name.  This example will do the following:
// If the key name equals "dsaKey_123", then load the DSA key from
// "qa_data/dsa/dsa1024_public.pem"
// 

if (CkStringBuilder_ContentsEqual(sbKeyName,'dsaKey_123',False) = False) then
  begin
    Memo1.Lines.Add('I don''t know this key...');
    Exit;
  end;

// The DSA public key used in this example is available at:
// https://www.chilkatsoft.com/exampleData/dsa1024_public.zip
pubKey := CkPublicKey_Create();
success := CkPublicKey_LoadFromFile(pubKey,'qa_data/dsa/dsa1024_public.pem');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
    Exit;
  end;

// Provide the DSA public key to the XML DSig verifier:
CkXmlDSig_SetPublicKey(verifier,pubKey);

// Verify the signature
bVerified := CkXmlDSig_VerifySignature(verifier,True);
Memo1.Lines.Add('Signature verified = ' + IntToStr(Ord(bVerified)));

CkHttp_Dispose(http);
CkStringBuilder_Dispose(sbXml);
CkXmlDSig_Dispose(verifier);
CkStringBuilder_Dispose(sbKeyName);
CkPublicKey_Dispose(pubKey);

end;