(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

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#include <C_CkJsonObject.h>
#include <C_CkStringBuilder.h>
#include <C_CkHttp.h>
#include <C_CkHttpResponse.h>
#include <C_CkCert.h>
#include <C_CkRsa.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkJsonObject json;
    HCkStringBuilder sb;
    const char *signedString;
    const char *hash_base64url;
    HCkJsonObject jsonBody;
    HCkHttp http;
    const char *url;
    HCkHttpResponse resp;
    int statusCode;
    HCkJsonObject jsonResp;
    HCkCert cert;
    HCkRsa rsa;
    BOOL valid;

    // 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) {
        // This means something failed before we got a response.
        printf("%s\n",CkHttp_lastErrorText(http));
        CkJsonObject_Dispose(json);
        CkStringBuilder_Dispose(sb);
        CkJsonObject_Dispose(jsonBody);
        CkHttp_Dispose(http);
        return;
    }

    statusCode = CkHttpResponse_getStatusCode(resp);

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

    CkJsonObject_putEmitCompact(jsonResp,FALSE);
    printf("%s\n",CkJsonObject_emit(jsonResp));

    if (statusCode != 200) {
        printf("Failed.\n");
        CkJsonObject_Dispose(json);
        CkStringBuilder_Dispose(sb);
        CkJsonObject_Dispose(jsonBody);
        CkHttp_Dispose(http);
        CkJsonObject_Dispose(jsonResp);
        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.
    // 
    cert = CkCert_Create();
    success = CkCert_LoadFromFile(cert,"qa_data/certs/chilkat_code_signing_2024.cer");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkJsonObject_Dispose(json);
        CkStringBuilder_Dispose(sb);
        CkJsonObject_Dispose(jsonBody);
        CkHttp_Dispose(http);
        CkJsonObject_Dispose(jsonResp);
        CkCert_Dispose(cert);
        return;
    }

    rsa = CkRsa_Create();
    // Tell the RSA object to use the cert's public key.
    success = CkRsa_SetX509Cert(rsa,cert,FALSE);
    if (success == FALSE) {
        printf("%s\n",CkRsa_lastErrorText(rsa));
        CkJsonObject_Dispose(json);
        CkStringBuilder_Dispose(sb);
        CkJsonObject_Dispose(jsonBody);
        CkHttp_Dispose(http);
        CkJsonObject_Dispose(jsonResp);
        CkCert_Dispose(cert);
        CkRsa_Dispose(rsa);
        return;
    }

    // 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"));
    printf("signature valid = %d\n",valid);


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

    }