(Delphi DLL) Create XML Digital Signature using a DSA Key

Demonstrates how to create an XML digital signature using a DSA 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, PrivateKey, XmlDSigGen, XmlDSig;

...

procedure TForm1.Button1Click(Sender: TObject);
var
url: PWideChar;
http: HCkHttp;
sbXml: HCkStringBuilder;
success: Boolean;
dsaKey: HCkPrivateKey;
xmlSigGen: HCkXmlDSigGen;
verifier: HCkXmlDSig;
bVerified: Boolean;

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

// The XML to be signed in this example contains the following:

// <?xml version="1.0" encoding="UTF-8" standalone="no"?>
// <Envelope>
//   <Header>
//     <Security>
//     </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/xmlToSign.xml
// Fetch the XML and then sign it..

url := 'https://www.chilkatsoft.com/exampleData/xmlToSign.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;

// This example uses a DSA private key for signing.  
// There are many ways of getting an DSA private key using Chilkat.  This example
// will load it from an encrypted PEM file.

// In case you would like to use it, I put the DSA private key PEM file here:
// https://www.chilkatsoft.com/exampleData/dsa1024_secret.zip
// The password is "secret".
dsaKey := CkPrivateKey_Create();
success := CkPrivateKey_LoadEncryptedPemFile(dsaKey,'qa_data/dsa/dsa1024_secret.pem','secret');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(dsaKey));
    Exit;
  end;

// To create the XML digital signature (i.e. embed the signature within
// the XML), first specify what is desired, then call the method to 
// create the XML signature.
// 
// For example, the application must provide the following:
//     - Where to put the signature.
//     - What to sign.
//     - The algorithms to be used.
//     - The key to be used for signing.
// 

xmlSigGen := CkXmlDSigGen_Create();

// In this example, we're going to put the signature within the Security element.
// To specify the location, set the SigLocation property to the XML path to this element,
// using vertical bar characters to separate tags.
CkXmlDSigGen_putSigLocation(xmlSigGen,'Envelope|Header|Security');

// An XML digital signature contains one or more references.  These can be references to the parts
// of the XML document to be signed (a same document reference), or can be external references.
// This example will add a single same-document reference.  We'll add a reference to the XML fragment
// at Body, which is indicated by providing the value of the "ID" attribute (where "ID" is case
// insensitive).  In this case, we specify "abc" because Body has an Id="abc".
// This causes the <Body> ... </Body> XML fragment to be signed.
// 
// For each same-document reference, we must also indicate the hash algorithm and XML canonicalization
// algorithm to be used.  For this example we'll choose SHA1 and Exclusive XML Canonicalization.
CkXmlDSigGen_AddSameDocRef(xmlSigGen,'abc','sha1','EXCL_C14N','','');

// Provide the DSA key to be used for signing:
CkXmlDSigGen_SetPrivateKey(xmlSigGen,dsaKey);

// We're leaving the following properties at their default values:
// 
//    - SigNamespacePrefix (default is "ds")
//    - SignedInfoCanonAlg  (default is EXCL_C14N)
//    - KeyInfoType (default is "KeyValue", where the DSA public key is included in the Signature)

// Note: Each Reference has it's own specified algorithms for XML canonicalization and hashing,
// and the actual signature part (the SignedInfo) has it's own hash/canonicalization algorithm.
// They may or may not be the same.  In this example, we use Exclusive XML Canonicalization and SHA1 throughout.

// The default SignedInfoDigestMethod is sha256, which is a good choice.  This example will
// change it to sha1.
CkXmlDSigGen_putSignedInfoDigestMethod(xmlSigGen,'sha1');

// OK, everything's specified, so let's create the XML digital signature:
// This in-place signs the XML.  If successful, sbXml will contain the 
// XML with the digital signature at the specified location.
success := CkXmlDSigGen_CreateXmlDSigSb(xmlSigGen,sbXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkXmlDSigGen__lastErrorText(xmlSigGen));
    Exit;
  end;

// Examine the signed XML:
Memo1.Lines.Add(CkStringBuilder__getAsString(sbXml));

// Below is the signed XML that is produced.
// Chilkat emits the Signature in compact form on a single line.  Whitespace in XML signatures
// matters.  Chilkat's opinion is that writing the Signature without whitespace minimizes the chance
// for problems with whatever software might be verifying the signature.

// <?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/2000/09/xmldsig#dsa-sha1"/><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/2000/09/xmldsig#sha1"/><ds:DigestValue>77X3L6odxTBow1W1dIiqZW1foow=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>Ci/KiAqoQLvNyK94n8TJwdJ6dVpIIy8tJg+9s8utmB92cW8lTd+U7g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:DSAKeyValue><ds:P>AN+Af9FvnqYl84Own8m/MHza9vVFEbpySOiWyeIM8diDjaES9i+UykaX9BGc0oaRJHtrHhe+gboMBGHfP+gYcgbqzeyVCi2kHghRD/TK7uI4jN8Yv8tfM6AO0QrDFfxFq4IV+qTZbSoCkbWaopQ+kEOY6B4btFxJ1YuE48mExMZ3</ds:P><ds:Q>AOCv5pwf4kvMW37Yzt0iH6URKOlD</ds:Q><ds:G>FO3eoDcpuU9Z25OQGFtC+M2ifczcKyRkFwTauGR3mIw0wePPiu3Ocr7A81SA8GQ9x3hWO5jyP//jL3jxYy8fgBg2RXwiic3nwT2rZfu50g6tPUpz1stKz/+Mxjulo6XuaMSOWwjU021IxVMzxQ1/L8QiwiIrwxvfQOaMY8HJgvw=</ds:G><ds:Y>JJmZQvWtrZ+Nb2YV47SfGAave8uOIedGlmg+CseoqKZC2aFcWM6kR0giUwQx834dhxQScRhqzxFxQPk/x+5hyG8LQbXW+BELmT1BiyodobYUAet4rSIt4EU4KU0iYw1drpcWT1jqI07l5xNi28heYSfSF5Odv2qwXxVKDSEeEkM=</ds:Y></ds:DSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></Security>
//   </Header>
//   <Body Id="abc">
//     <z:FooBar xmlns:z="https://www.example-code.com"/>
//   </Body>
// </Envelope>

// The above signed XML contains the DSA public key in the DSAKeyValue fragment (within the ds:KeyInfo).
// The signature can easily be verified like this:

verifier := CkXmlDSig_Create();

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

bVerified := CkXmlDSig_VerifySignature(verifier,True);
if (bVerified <> True) then
  begin
    Memo1.Lines.Add(CkXmlDSig__lastErrorText(verifier));
  end;
Memo1.Lines.Add('Signature verified = ' + IntToStr(Ord(bVerified)));

CkHttp_Dispose(http);
CkStringBuilder_Dispose(sbXml);
CkPrivateKey_Dispose(dsaKey);
CkXmlDSigGen_Dispose(xmlSigGen);
CkXmlDSig_Dispose(verifier);

end;