(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.

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 C/C++ Library Downloads
MS Visual C/C++ Linux/CentOS C/C++ Alpine Linux C/C++ MAC OS X C/C++	armhf/aarch64 C/C++ C++ Builder iOS C/C++ Android C/C++	Solaris C/C++ MinGW C/C++

#include <CkJsonObject.h>
#include <CkStringBuilder.h>
#include <CkHttp.h>
#include <CkHttpResponse.h>
#include <CkCert.h>
#include <CkRsa.h>

void ChilkatSample(void)
    {
    // 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.

    bool success;

    // Provide information needed for Chilkat to automatically get an OAuth2 access token as needed.
    CkJsonObject json;
    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"
    CkStringBuilder sb;
    const char *signedString = "This is a test";
    sb.Append(signedString);
    const char *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..

    CkJsonObject jsonBody;
    jsonBody.UpdateString("alg","RS256");
    jsonBody.UpdateString("value",hash_base64url);

    CkHttp 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.put_AuthToken(json.emit());

    http.SetUrlVar("certName","importCert01");
    http.SetUrlVar("certVersion","7140c8755ed14839b5d86a9f7e7f0497");
    // Note: Replace "VAULT_NAME" with the name of your Azure key vault.
    const char *url = "https://VAULT_NAME.vault.azure.net/keys/{$certName}/{$certVersion}/sign?api-version=7.4";
    CkHttpResponse *resp = http.PostJson3(url,"application/json",jsonBody);
    if (http.get_LastMethodSuccess() == false) {
        // This means something failed before we got a response.
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    int statusCode = resp->get_StatusCode();

    CkJsonObject jsonResp;
    resp->GetBodyJson(jsonResp);
    delete resp;

    jsonResp.put_EmitCompact(false);
    std::cout << jsonResp.emit() << "\r\n";

    if (statusCode != 200) {
        std::cout << "Failed." << "\r\n";
        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.
    // 
    CkCert cert;
    success = cert.LoadFromFile("qa_data/certs/chilkat_code_signing_2024.cer");
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    CkRsa rsa;
    // Tell the RSA object to use the cert's public key.
    success = rsa.SetX509Cert(cert,false);
    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    // Verify the signature using the cert's public key against the original string.
    rsa.put_EncodingMode("base64url");
    bool valid = rsa.VerifyStringENC(signedString,"sha-256",jsonResp.stringOf("value"));
    std::cout << "signature valid = " << valid << "\r\n";
    }