#include <dlfcn.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <openssl/provider.h>

#if defined(OPENSSL_VERSION_MAJOR) && (OPENSSL_VERSION_MAJOR >= 3)
#define CRYPTO_LIBRARY "/lib/libcrypto.so.35"
static void fbsd_ossl_provider_unload(void);
static void print_dlerror(char *);
static OSSL_PROVIDER *deflt;
static int providers_loaded = 0;
static OSSL_PROVIDER * (*ossl_provider_load)(OSSL_LIB_CTX *, const char*) = NULL;
static int (*ossl_provider_unload)(OSSL_PROVIDER *) = NULL;
static void *crypto_lib_handle = NULL;

static void
fbsd_ossl_provider_unload(void)
{
        if (ossl_provider_unload == NULL) {
                if (!(ossl_provider_unload = (int (*)(OSSL_PROVIDER*)) dlsym(crypto_lib_handle, "OSSL_PROVIDER_unload"))) {
                        print_dlerror("Unable to link OSSL_PROVIDER_unload");
                        return;
                }
        }
        if (providers_loaded == 1) {
                (*ossl_provider_unload)(deflt);
                providers_loaded = 0;
        }
}

static void
print_dlerror(char *message)
{
        char *errstr;

        if ((errstr = dlerror()) != NULL)
                fprintf(stderr, "%s: %s\n",
                        message, errstr);
}
#endif

int
fbsd_ossl_provider_load(void)
{
#if defined(OPENSSL_VERSION_MAJOR) && (OPENSSL_VERSION_MAJOR >= 3)
        if (crypto_lib_handle == NULL) {
                if (!(crypto_lib_handle = dlopen(CRYPTO_LIBRARY,
                    RTLD_LAZY|RTLD_GLOBAL))) {
                        print_dlerror("Unable to load libcrypto.so");
                        return (EINVAL);
                }
        }
        if (ossl_provider_load == NULL) {
                if (!(ossl_provider_load = (OSSL_PROVIDER * (*)(OSSL_LIB_CTX*, const char *)) dlsym(crypto_lib_handle, "OSSL_PROVIDER_load"))) {
                        print_dlerror("Unable to link OSSL_PROVIDER_load");
                        return(ENOENT);
                }
        }

        if (providers_loaded == 0) {
                if ((deflt = (*ossl_provider_load)(NULL, "default")) == NULL) {
                        return (EINVAL);
                }
                if (atexit(fbsd_ossl_provider_unload)) {
                        fbsd_ossl_provider_unload();
                        return (errno);
                }
                providers_loaded = 1;
        }
#endif
        return (0);
}