Pascal (Lazarus/Delphi)

Azure Key Vault Sign with a Certificate's Private Key

See more Azure Key Vault Examples

Signs a hash using the private key of a certificate previously imported to an Azure Key Vault. 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.HttpResponse,
  Chilkat.StringBuilder,
  Chilkat.JsonObject,
  Chilkat.Rsa,
  Chilkat.Cert,
  Chilkat.Http;

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

procedure RunDemo;
var
  success: Boolean;
  json: TJsonObject;
  sb: TStringBuilder;
  signedString: string;
  hash_base64url: string;
  jsonBody: TJsonObject;
  http: THttp;
  url: string;
  resp: THttpResponse;
  statusCode: Integer;
  jsonResp: TJsonObject;
  cert: TCert;
  rsa: TRsa;
  valid: Boolean;

begin
  success := False;

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

  //  See Azure Key Vault Get Certificates for a more detailed explanation
  //  for how Chilkat is automatically getting the OAuth2 access token for your application.

  //  Provide information needed for Chilkat to automatically get an OAuth2 access token as needed.
  json := TJsonObject.Create;
  json.UpdateString('client_id','APP_ID');
  json.UpdateString('client_secret','APP_PASSWORD');
  json.UpdateString('resource','https://vault.azure.net');
  json.UpdateString('token_endpoint','https://login.microsoftonline.com/TENANT_ID/oauth2/token');

  //  In this example, we'll sign the SHA256 hash of the string "This is a test"
  sb := TStringBuilder.Create;
  signedString := 'This is a test';
  sb.Append(signedString);
  hash_base64url := sb.GetHash('sha256','base64url','utf-8');

  //  We're going to send a POST to the following URL:
  //  POST {vaultBaseUrl}/keys/{key-or-cert-name}/{key-or-cert-version}/sign?api-version=7.4

  //  For example:

  //  POST https://VAULT_NAME.vault.azure.net/keys/CERT_NAME/CERT_VERSION/sign?api-version=7.4
  //  
  //  {
  //    "alg": "RS512",
  //    "value": "RUE3Nzg4NTQ4QjQ5RjFFN0U2NzAyQzhDNEMwMkJDOTA1MTYyOTUzNjI5NDhBNzZDQTlFOTM1NDA2M0ZGMjk2Mg"
  //  }

  //  The alg can be one of the following
  //  ES256  ECDSA using P-256 and SHA-256
  //  ES256K ECDSA using P-256K and SHA-256
  //  ES384  ECDSA using P-384 and SHA-384
  //  ES512  ECDSA using P-521 and SHA-512
  //  PS256  RSASSA-PSS using SHA-256 and MGF1 with SHA-256
  //  PS384  RSASSA-PSS using SHA-384 and MGF1 with SHA-384
  //  PS512  RSASSA-PSS using SHA-512 and MGF1 with SHA-512
  //  RS256  RSASSA-PKCS1-v1_5 using SHA-256
  //  RS384  RSASSA-PKCS1-v1_5 using SHA-384
  //  RS512  RSASSA-PKCS1-v1_5 using SHA-512

  //  The sample POST above uses SHA512.  We'll instead sign a SHA256 hash..

  jsonBody := TJsonObject.Create;
  jsonBody.UpdateString('alg','RS256');
  jsonBody.UpdateString('value',hash_base64url);

  http := THttp.Create;

  //  Instead of providing an actual access token, we give Chilkat the information that allows it to 
  //  automatically fetch the access token using the OAuth2 client credentials flow.
  http.AuthToken := json.Emit();

  http.SetUrlVar('certName','importCert01');
  http.SetUrlVar('certVersion','7140c8755ed14839b5d86a9f7e7f0497');
  //  Note: Replace "VAULT_NAME" with the name of your Azure key vault.
  url := 'https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4';
  resp := THttpResponse.Create;
  success := http.HttpJson('POST',url,jsonBody,'application/json',resp);
  if (success = False) then
    begin
      WriteLn(http.LastErrorText);
      Exit;
    end;

  statusCode := resp.StatusCode;

  jsonResp := TJsonObject.Create;
  resp.GetBodyJson(jsonResp);

  jsonResp.EmitCompact := False;
  WriteLn(jsonResp.Emit());

  if (statusCode <> 200) then
    begin
      WriteLn('Failed.');
      Exit;
    end;

  //  A successful response body contains JSON like this:
  //  Note: Azure's documentation is not very clear, but base64url is the encoding, not "base64".
  //  {
  //    "kid": "https://kvchilkat.vault.azure.net/keys/importCert01/7140c8755ed14839b5d86a9f7e7f0497",
  //    "value": "JzWd2YF21gjtW ... Em37hKOQ"
  //  }

  //  Let's validate the signature using the cert's public key.
  //  This example will load the corresponding certificate from a local file and will verify the signature against the original data.
  //  
  cert := TCert.Create;
  success := cert.LoadFromFile('qa_data/certs/chilkat_code_signing_2024.cer');
  if (success = False) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  rsa := TRsa.Create;
  //  Tell the RSA object to use the cert's public key.
  success := rsa.SetX509Cert(cert,False);
  if (success = False) then
    begin
      WriteLn(rsa.LastErrorText);
      Exit;
    end;

  //  Verify the signature using the cert's public key against the original string.
  rsa.EncodingMode := 'base64url';
  valid := rsa.VerifyStringENC(signedString,'sha-256',jsonResp.StringOf('value'));
  WriteLn('signature valid = ' + valid);


  json.Free;
  sb.Free;
  jsonBody.Free;
  http.Free;
  resp.Free;
  jsonResp.Free;
  cert.Free;
  rsa.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.