(Delphi DLL) 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.

Note: This example requires Chilkat v9.5.0.96 or later.

For more information, see https://learn.microsoft.com/en-us/rest/api/keyvault/certificates/import-certificate/import-certificate?tabs=HTTP

Chilkat for Delphi Downloads 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, HttpResponse, StringBuilder, JsonObject, Rsa, Cert, Http;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
json: HCkJsonObject;
sb: HCkStringBuilder;
signedString: PWideChar;
hash_base64url: PWideChar;
jsonBody: HCkJsonObject;
http: HCkHttp;
url: PWideChar;
resp: HCkHttpResponse;
statusCode: Integer;
jsonResp: HCkJsonObject;
cert: HCkCert;
rsa: HCkRsa;
valid: Boolean;

begin
// 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 := CkJsonObject_Create();
CkJsonObject_UpdateString(json,'client_id','APP_ID');
CkJsonObject_UpdateString(json,'client_secret','APP_PASSWORD');
CkJsonObject_UpdateString(json,'resource','https://vault.azure.net');
CkJsonObject_UpdateString(json,'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 := CkStringBuilder_Create();
signedString := 'This is a test';
CkStringBuilder_Append(sb,signedString);
hash_base64url := CkStringBuilder__getHash(sb,'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 := CkJsonObject_Create();
CkJsonObject_UpdateString(jsonBody,'alg','RS256');
CkJsonObject_UpdateString(jsonBody,'value',hash_base64url);

http := CkHttp_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.
CkHttp_putAuthToken(http,CkJsonObject__emit(json));

CkHttp_SetUrlVar(http,'certName','importCert01');
CkHttp_SetUrlVar(http,'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 := CkHttp_PostJson3(http,url,'application/json',jsonBody);
if (CkHttp_getLastMethodSuccess(http) = False) then
  begin
    // This means something failed before we got a response.
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

statusCode := CkHttpResponse_getStatusCode(resp);

jsonResp := CkJsonObject_Create();
CkHttpResponse_GetBodyJson(resp,jsonResp);
CkHttpResponse_Dispose(resp);

CkJsonObject_putEmitCompact(jsonResp,False);
Memo1.Lines.Add(CkJsonObject__emit(jsonResp));

if (statusCode <> 200) then
  begin
    Memo1.Lines.Add('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 := CkCert_Create();
success := CkCert_LoadFromFile(cert,'qa_data/certs/chilkat_code_signing_2024.cer');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

rsa := CkRsa_Create();
// Tell the RSA object to use the cert's public key.
success := CkRsa_SetX509Cert(rsa,cert,False);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// Verify the signature using the cert's public key against the original string.
CkRsa_putEncodingMode(rsa,'base64url');
valid := CkRsa_VerifyStringENC(rsa,signedString,'sha-256',CkJsonObject__stringOf(jsonResp,'value'));
Memo1.Lines.Add('signature valid = ' + IntToStr(Ord(valid)));

CkJsonObject_Dispose(json);
CkStringBuilder_Dispose(sb);
CkJsonObject_Dispose(jsonBody);
CkHttp_Dispose(http);
CkJsonObject_Dispose(jsonResp);
CkCert_Dispose(cert);
CkRsa_Dispose(rsa);

end;