Windows Certificates to OpenSSL X509_STORE

load_system_certificates.cpp

/// @see https://stackoverflow.com/a/40046425
#include <memory>

#include <WinSock2.h>
#include <Windows.h>
#include <cryptuiapi.h>
#include <wincrypt.h>

/**
 * @see https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certopensystemstorew
 * @see https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certenumcertificatesinstore
 * 
 * @code
 * #include <openssl/ssl.h>
 * 
 * uint32_t load_system_certificates(SSL_CTX* ssl) noexcept {
 *   X509_STORE* store = SSL_CTX_get_cert_store(ssl);
 *   return load_system_certificates(store);
 * }
 * @endcode
 */
uint32_t load_system_certificates(X509_STORE* store) noexcept {
    HCERTSTORE certs = CertOpenSystemStoreW(0, L"CA");
    if (certs == nullptr)
        return GetLastError();
    PCCERT_CONTEXT context = CertEnumCertificatesInStore(certs, nullptr);
    for (; context; context = CertEnumCertificatesInStore(certs, context)) {
        const auto* cert = reinterpret_cast<unsigned char*>(context->pbCertEncoded);
        const auto certlen = context->cbCertEncoded;
        auto x509 = std::unique_ptr<X509, void (*)(X509*)>{d2i_X509(nullptr, &cert, certlen), &X509_free};
        if (x509 == nullptr)
            continue;
        X509_STORE_add_cert(store, x509.get());
    }
    if (context)
        CertFreeCertificateContext(context);
    return CertCloseStore(certs, 0) == FALSE ? GetLastError() : S_OK;
}