C#

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. C#

bool 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.
Chilkat.JsonObject json = new Chilkat.JsonObject();
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"
Chilkat.StringBuilder sb = new Chilkat.StringBuilder();
string signedString = "This is a test";
sb.Append(signedString);
string 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..

Chilkat.JsonObject jsonBody = new Chilkat.JsonObject();
jsonBody.UpdateString("alg","RS256");
jsonBody.UpdateString("value",hash_base64url);

Chilkat.Http http = new Chilkat.Http();

//  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.
string url = "https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4";
Chilkat.HttpResponse resp = new Chilkat.HttpResponse();
success = http.HttpJson("POST",url,jsonBody,"application/json",resp);
if (success == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

int statusCode = resp.StatusCode;

Chilkat.JsonObject jsonResp = new Chilkat.JsonObject();
resp.GetBodyJson(jsonResp);

jsonResp.EmitCompact = false;
Debug.WriteLine(jsonResp.Emit());

if (statusCode != 200) {
    Debug.WriteLine("Failed.");
    return;
}

//  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.
//  
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadFromFile("qa_data/certs/chilkat_code_signing_2024.cer");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Chilkat.Rsa rsa = new Chilkat.Rsa();
//  Tell the RSA object to use the cert's public key.
success = rsa.SetX509Cert(cert,false);
if (success == false) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

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