Not able to retrieve private key

Hi,

I am building VPN client with Packet Tunnel Provider for macOS. The VPN profile configured by Apple Configurator 2 uses certificate p12 file as user authentication for connection, the profile installed on my Mac as well as the certificate was imported to keychain.

The VPN extension is called once I try to connect the vpn, but I am not able to retrieve the private key with persistent reference of my VPN keychain item which comes within NETunnelProviderProtocol object. Below are things I did.

1. Generate p12 file with certificate and RSA private key.

openssl pkcs12 -export -out client.p12 -inkey privateKey.key -in certificate.crt -certfile CACert.crt

2. Try to retrieve the private key with persistent reference in NETunnelProviderProtocol object in Packet Tunnel Provider extension.

SecIdentityRef identity_ref = NULL;

const void *keys[] = { kSecClass, kSecReturnRef, kSecValuePersistentRef };

const void *values[] = { kSecClassIdentity, kCFBooleanTrue, persistent_ref };

CFDictionaryRef dict = CFDictionaryCreate(NULL, keys, values, 3, NULL, NULL);

if ( SecItemCopyMatching(dict, &identity_ref) == errSecSuccess)

{

SecItemImportExportKeyParameters params = {};

params.version = SEC_KEY_IMPORT_EXPORT_PARAMS_VERSION;

params.flags = kSecKeySecurePassphrase;

params.passphrase = CFStringCreateWithCString(kCFAllocatorDefault, "", kCFStringEncodingASCII);

status = SecItemExport(identity, kSecFormatPKCS12,0, &params, &exportResult);// error, not able to get the private key

}

Addictionly I try to use SecItemCopyMatching to retrieve the private key, I can get just only 96 bytes back, obviously, it is not correct.

There should be something wrong with my code, please give me help.

Thanks!