/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "tcn.h"

#include "apr_thread_rwlock.h"
#include "apr_atomic.h"

#include "ssl_private.h"
#include <stdint.h>

extern apr_pool_t *tcn_global_pool;

static apr_status_t ssl_context_cleanup(void *data)
{
    tcn_ssl_ctxt_t *c = (tcn_ssl_ctxt_t *)data;
    JNIEnv *e;

    if (c) {
        SSL_CTX_free(c->ctx); // this function is safe to call with NULL
        c->ctx = NULL;

        if (c->verifier != NULL) {
            tcn_get_java_env(&e);
            (*e)->DeleteGlobalRef(e, c->verifier);
            c->verifier = NULL;
        }
        c->verifier_method = NULL;

        if (c->cert_requested_callback != NULL) {
            tcn_get_java_env(&e);
            (*e)->DeleteGlobalRef(e, c->cert_requested_callback);
            c->cert_requested_callback = NULL;
        }
        c->cert_requested_callback_method = NULL;

        if (c->next_proto_data != NULL) {
            free(c->next_proto_data);
            c->next_proto_data = NULL;
        }
        c->next_proto_len = 0;

        if (c->alpn_proto_data != NULL) {
            free(c->alpn_proto_data);
            c->alpn_proto_data = NULL;
        }
        c->alpn_proto_len = 0;

        apr_thread_rwlock_destroy(c->mutex);

        if (c->ticket_keys != NULL) {
            free(c->ticket_keys);
            c->ticket_keys = NULL;
        }
        c->ticket_keys_len = 0;

        if (c->password != NULL) {
            free(c->password);
            c->password = NULL;
        }
    }
    return APR_SUCCESS;
}

/* Initialize server context */
TCN_IMPLEMENT_CALL(jlong, SSLContext, make)(TCN_STDARGS, jint protocol, jint mode)
{
    apr_pool_t *p = NULL;
    tcn_ssl_ctxt_t *c = NULL;
    SSL_CTX *ctx = NULL;

    UNREFERENCED(o);

    switch (protocol) {
    case SSL_PROTOCOL_TLS:
    case SSL_PROTOCOL_ALL:
        if (mode == SSL_MODE_CLIENT)
            ctx = SSL_CTX_new(SSLv23_client_method());
        else if (mode == SSL_MODE_SERVER)
            ctx = SSL_CTX_new(SSLv23_server_method());
        else
            ctx = SSL_CTX_new(SSLv23_method());
        break;
    case SSL_PROTOCOL_TLSV1_2:
#ifndef OPENSSL_NO_TLS1
        if (mode == SSL_MODE_CLIENT)
            ctx = SSL_CTX_new(TLSv1_2_client_method());
        else if (mode == SSL_MODE_SERVER)
            ctx = SSL_CTX_new(TLSv1_2_server_method());
        else
            ctx = SSL_CTX_new(TLSv1_2_method());
#endif
        break;
    case SSL_PROTOCOL_TLSV1_1:
#ifndef OPENSSL_NO_TLS1
        if (mode == SSL_MODE_CLIENT)
            ctx = SSL_CTX_new(TLSv1_1_client_method());
        else if (mode == SSL_MODE_SERVER)
            ctx = SSL_CTX_new(TLSv1_1_server_method());
        else
            ctx = SSL_CTX_new(TLSv1_1_method());
#endif
        break;
    case SSL_PROTOCOL_TLSV1:
#ifndef OPENSSL_NO_TLS1
        if (mode == SSL_MODE_CLIENT)
            ctx = SSL_CTX_new(TLSv1_client_method());
        else if (mode == SSL_MODE_SERVER)
            ctx = SSL_CTX_new(TLSv1_server_method());
        else
            ctx = SSL_CTX_new(TLSv1_method());
#endif
        break;
    case SSL_PROTOCOL_SSLV3:
#ifndef OPENSSL_NO_SSL3
        if (mode == SSL_MODE_CLIENT)
            ctx = SSL_CTX_new(SSLv3_client_method());
        else if (mode == SSL_MODE_SERVER)
            ctx = SSL_CTX_new(SSLv3_server_method());
        else
            ctx = SSL_CTX_new(SSLv3_method());
#endif
        break;
    case SSL_PROTOCOL_SSLV2:
#if (OPENSSL_VERSION_NUMBER < 0x10100000L) && !defined(OPENSSL_NO_SSL2)
        if (mode == SSL_MODE_CLIENT)
            ctx = SSL_CTX_new(SSLv2_client_method());
        else if (mode == SSL_MODE_SERVER)
            ctx = SSL_CTX_new(SSLv2_server_method());
        else
            ctx = SSL_CTX_new(SSLv2_method());
#endif
        break;
    default:
        // Try to give the user the highest supported protocol.
#ifndef OPENSSL_NO_TLS1
        if (protocol & SSL_PROTOCOL_TLSV1_2) {
            if (mode == SSL_MODE_CLIENT)
                ctx = SSL_CTX_new(TLSv1_2_client_method());
            else if (mode == SSL_MODE_SERVER)
                ctx = SSL_CTX_new(TLSv1_2_server_method());
            else
                ctx = SSL_CTX_new(TLSv1_2_method());
            break;
        } else if (protocol & SSL_PROTOCOL_TLSV1_1) {
            if (mode == SSL_MODE_CLIENT)
                ctx = SSL_CTX_new(TLSv1_1_client_method());
            else if (mode == SSL_MODE_SERVER)
                ctx = SSL_CTX_new(TLSv1_1_server_method());
            else
                ctx = SSL_CTX_new(TLSv1_1_method());
            break;
        } else if (protocol & SSL_PROTOCOL_TLSV1) {
            if (mode == SSL_MODE_CLIENT)
                ctx = SSL_CTX_new(TLSv1_client_method());
            else if (mode == SSL_MODE_SERVER)
                ctx = SSL_CTX_new(TLSv1_server_method());
            else
                ctx = SSL_CTX_new(TLSv1_method());
            break;
        }
#endif
#ifndef OPENSSL_NO_SSL3
        if (protocol & SSL_PROTOCOL_SSLV3) {
            if (mode == SSL_MODE_CLIENT)
                ctx = SSL_CTX_new(SSLv3_client_method());
            else if (mode == SSL_MODE_SERVER)
                ctx = SSL_CTX_new(SSLv3_server_method());
            else
                ctx = SSL_CTX_new(SSLv3_method());
            break;
        }
#endif
#if (OPENSSL_VERSION_NUMBER < 0x10100000L) && !defined(OPENSSL_NO_SSL2)
        if (protocol & SSL_PROTOCOL_SSLV2) {
            if (mode == SSL_MODE_CLIENT)
                ctx = SSL_CTX_new(SSLv2_client_method());
            else if (mode == SSL_MODE_SERVER)
                ctx = SSL_CTX_new(SSLv2_server_method());
            else
                ctx = SSL_CTX_new(SSLv2_method());
            break;
        }
#endif
        tcn_Throw(e, "Unsupported SSL protocol (%d)", protocol);
        goto cleanup;
    }

    if (ctx == NULL) {
        char err[256];
        ERR_error_string(ERR_get_error(), err);
        tcn_Throw(e, "Failed to initialize SSL_CTX (%s)", err);
        goto cleanup;
    }

    TCN_THROW_IF_ERR(apr_pool_create(&p, tcn_global_pool), p);

    if ((c = apr_pcalloc(p, sizeof(tcn_ssl_ctxt_t))) == NULL) {
        tcn_ThrowAPRException(e, apr_get_os_error());
        goto cleanup;
    }

    c->protocol = protocol;
    c->mode     = mode;
    c->ctx      = ctx;
    c->pool     = p;
    if (!(protocol & SSL_PROTOCOL_SSLV2))
        SSL_CTX_set_options(c->ctx, SSL_OP_NO_SSLv2);
    if (!(protocol & SSL_PROTOCOL_SSLV3))
        SSL_CTX_set_options(c->ctx, SSL_OP_NO_SSLv3);
    if (!(protocol & SSL_PROTOCOL_TLSV1))
        SSL_CTX_set_options(c->ctx, SSL_OP_NO_TLSv1);
#ifdef SSL_OP_NO_TLSv1_1
    if (!(protocol & SSL_PROTOCOL_TLSV1_1))
        SSL_CTX_set_options(c->ctx, SSL_OP_NO_TLSv1_1);
#endif
#ifdef SSL_OP_NO_TLSv1_2
    if (!(protocol & SSL_PROTOCOL_TLSV1_2))
        SSL_CTX_set_options(c->ctx, SSL_OP_NO_TLSv1_2);
#endif
    /*
     * Configure additional context ingredients
     */
    SSL_CTX_set_options(c->ctx, SSL_OP_SINGLE_DH_USE);
#ifdef HAVE_ECC
    SSL_CTX_set_options(c->ctx, SSL_OP_SINGLE_ECDH_USE);
#endif

    SSL_CTX_set_options(c->ctx, SSL_OP_NO_COMPRESSION);

    /*
     * Disallow a session from being resumed during a renegotiation,
     * so that an acceptable cipher suite can be negotiated.
     */
    SSL_CTX_set_options(c->ctx, SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION);
    /**
     * These options may be set by default but can be dangerous in practice [1].
     * [1] https://www.openssl.org/docs/man1.0.1/ssl/SSL_CTX_set_options.html
     */
    SSL_CTX_clear_options(c->ctx, SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION | SSL_OP_LEGACY_SERVER_CONNECT);

    /* Release idle buffers to the SSL_CTX free list */
    SSL_CTX_set_mode(c->ctx, SSL_MODE_RELEASE_BUFFERS);

    /* Default session context id and cache size */
    SSL_CTX_sess_set_cache_size(c->ctx, SSL_DEFAULT_CACHE_SIZE);

    /* Session cache is disabled by default */
    SSL_CTX_set_session_cache_mode(c->ctx, SSL_SESS_CACHE_OFF);
    /* Longer session timeout */
    SSL_CTX_set_timeout(c->ctx, 14400);
    EVP_Digest((const unsigned char *)SSL_DEFAULT_VHOST_NAME,
               (unsigned long)((sizeof SSL_DEFAULT_VHOST_NAME) - 1),
               &(c->context_id[0]), NULL, EVP_sha1(), NULL);
    if (mode) {
#ifdef HAVE_ECC
        /* Set default (nistp256) elliptic curve for ephemeral ECDH keys */
        EC_KEY *ecdh = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
        SSL_CTX_set_tmp_ecdh(c->ctx, ecdh);
        EC_KEY_free(ecdh);
#endif

        SSL_CTX_set_tmp_dh_callback(c->ctx,  SSL_callback_tmp_DH);
    }

    // Default depth is 100 and disabled according to https://www.openssl.org/docs/man1.0.2/ssl/SSL_set_verify.html.
    c->verify_config.verify_depth  = 100;
    c->verify_config.verify_mode   = SSL_CVERIFY_NONE;

    /* Set default password callback */
    SSL_CTX_set_default_passwd_cb(c->ctx, (pem_password_cb *)SSL_password_callback);
    SSL_CTX_set_default_passwd_cb_userdata(c->ctx, (void *) c->password);

    apr_thread_rwlock_create(&c->mutex, p);
    /*
     * Let us cleanup the ssl context when the pool is destroyed
     */
    apr_pool_cleanup_register(p, (const void *)c,
                              ssl_context_cleanup,
                              apr_pool_cleanup_null);

    return P2J(c);
cleanup:
    if (p != NULL) {
        apr_pool_destroy(p);
    }
    SSL_CTX_free(ctx); // this function is safe to call with NULL.
    return 0;
}

TCN_IMPLEMENT_CALL(jint, SSLContext, free)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    UNREFERENCED_STDARGS;
    TCN_ASSERT(ctx != 0);
    /* Run and destroy the cleanup callback */
    int result = apr_pool_cleanup_run(c->pool, c, ssl_context_cleanup);
    apr_pool_destroy(c->pool);
    return result;
}

TCN_IMPLEMENT_CALL(void, SSLContext, setContextId)(TCN_STDARGS, jlong ctx,
                                                   jstring id)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    TCN_ALLOC_CSTRING(id);

    TCN_ASSERT(ctx != 0);
    UNREFERENCED(o);
    if (J2S(id)) {
        EVP_Digest((const unsigned char *)J2S(id),
                   (unsigned long)strlen(J2S(id)),
                   &(c->context_id[0]), NULL, EVP_sha1(), NULL);
    }
    TCN_FREE_CSTRING(id);
}

TCN_IMPLEMENT_CALL(void, SSLContext, setOptions)(TCN_STDARGS, jlong ctx,
                                                 jint opt)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED_STDARGS;
    TCN_ASSERT(ctx != 0);

    SSL_CTX_set_options(c->ctx, opt);
}

TCN_IMPLEMENT_CALL(jint, SSLContext, getOptions)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED_STDARGS;
    TCN_ASSERT(ctx != 0);

    return SSL_CTX_get_options(c->ctx);
}

TCN_IMPLEMENT_CALL(void, SSLContext, clearOptions)(TCN_STDARGS, jlong ctx,
                                                   jint opt)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED_STDARGS;
    TCN_ASSERT(ctx != 0);
    SSL_CTX_clear_options(c->ctx, opt);
}

TCN_IMPLEMENT_CALL(jboolean, SSLContext, setCipherSuite)(TCN_STDARGS, jlong ctx,
                                                         jstring ciphers)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    TCN_ALLOC_CSTRING(ciphers);
    jboolean rv = JNI_TRUE;

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);
    if (!J2S(ciphers))
        return JNI_FALSE;

    if (!SSL_CTX_set_cipher_list(c->ctx, J2S(ciphers))) {
        char err[256];
        ERR_error_string(ERR_get_error(), err);
        tcn_Throw(e, "Unable to configure permitted SSL ciphers (%s)", err);
        rv = JNI_FALSE;
    }
    TCN_FREE_CSTRING(ciphers);
    return rv;
}

TCN_IMPLEMENT_CALL(jboolean, SSLContext, setCertificateChainFile)(TCN_STDARGS, jlong ctx,
                                                                  jstring file,
                                                                  jboolean skipfirst)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jboolean rv = JNI_FALSE;
    TCN_ALLOC_CSTRING(file);

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);
    if (!J2S(file))
        return JNI_FALSE;
    if (SSL_CTX_use_certificate_chain(c->ctx, J2S(file), skipfirst) > 0)
        rv = JNI_TRUE;
    TCN_FREE_CSTRING(file);
    return rv;
}

TCN_IMPLEMENT_CALL(jboolean, SSLContext, setCertificateChainBio)(TCN_STDARGS, jlong ctx,
                                                                  jlong chain,
                                                                  jboolean skipfirst)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    BIO *b = J2P(chain, BIO *);

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);
    if (b == NULL)
        return JNI_FALSE;
    if (SSL_CTX_use_certificate_chain_bio(c->ctx, b, skipfirst) > 0)  {
        return JNI_TRUE;
    }
    return JNI_FALSE;
}

TCN_IMPLEMENT_CALL(jboolean, SSLContext, setCACertificateBio)(TCN_STDARGS, jlong ctx, jlong certs)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    BIO *b = J2P(certs, BIO *);

    UNREFERENCED(o);
    TCN_ASSERT(c != NULL);

    return b != NULL && c->mode != SSL_MODE_CLIENT && SSL_CTX_use_client_CA_bio(c->ctx, b) > 0 ? JNI_TRUE : JNI_FALSE;
}

TCN_IMPLEMENT_CALL(void, SSLContext, setTmpDHLength)(TCN_STDARGS, jlong ctx, jint length)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);
    switch (length) {
        case 512:
            SSL_CTX_set_tmp_dh_callback(c->ctx,  SSL_callback_tmp_DH_512);
            return;
        case 1024:
            SSL_CTX_set_tmp_dh_callback(c->ctx,  SSL_callback_tmp_DH_1024);
            return;
        case 2048:
            SSL_CTX_set_tmp_dh_callback(c->ctx,  SSL_callback_tmp_DH_2048);
            return;
        case 4096:
            SSL_CTX_set_tmp_dh_callback(c->ctx,  SSL_callback_tmp_DH_4096);
            return;
        default:
            tcn_Throw(e, "Unsupported length %s", length);
            return;
    }
}

TCN_IMPLEMENT_CALL(void, SSLContext, setVerify)(TCN_STDARGS, jlong ctx, jint level, jint depth)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED(o);
    TCN_ASSERT(c != NULL);

    // No need to set the callback for SSL_CTX_set_verify because we override the default certificate verification via SSL_CTX_set_cert_verify_callback.
    SSL_CTX_set_verify(c->ctx, tcn_set_verify_config(&c->verify_config, level, depth), NULL);
    SSL_CTX_set_verify_depth(c->ctx, c->verify_config.verify_depth);
}

static EVP_PKEY *load_pem_key(tcn_ssl_ctxt_t *c, const char *file)
{
    BIO *bio = NULL;
    EVP_PKEY *key = NULL;

    if ((bio = BIO_new(BIO_s_file())) == NULL) {
        return NULL;
    }
    if (BIO_read_filename(bio, file) <= 0) {
        BIO_free(bio);
        return NULL;
    }

    key = PEM_read_bio_PrivateKey(bio, NULL, (pem_password_cb *)SSL_password_callback, (void *)c->password);

    BIO_free(bio);
    return key;
}

static X509 *load_pem_cert(tcn_ssl_ctxt_t *c, const char *file)
{
    BIO *bio = NULL;
    X509 *cert = NULL;

    if ((bio = BIO_new(BIO_s_file())) == NULL) {
        return NULL;
    }
    if (BIO_read_filename(bio, file) <= 0) {
        BIO_free(bio);
        return NULL;
    }
    cert = PEM_read_bio_X509_AUX(bio, NULL,
                (pem_password_cb *)SSL_password_callback,
                (void *)c->password);
    if (cert == NULL &&
       (ERR_GET_REASON(ERR_peek_last_error()) == PEM_R_NO_START_LINE)) {
        ERR_clear_error();
        BIO_ctrl(bio, BIO_CTRL_RESET, 0, NULL);
        cert = d2i_X509_bio(bio, NULL);
    }
    BIO_free(bio);
    return cert;
}

static int ssl_load_pkcs12(tcn_ssl_ctxt_t *c, const char *file,
                           EVP_PKEY **pkey, X509 **cert, STACK_OF(X509) **ca)
{
    const char *pass;
    char        buff[PEM_BUFSIZE];
    int         len, rc = 0;
    PKCS12     *p12;
    BIO        *in;

    if ((in = BIO_new(BIO_s_file())) == 0)
        return 0;
    if (BIO_read_filename(in, file) <= 0) {
        BIO_free(in);
        return 0;
    }
    p12 = d2i_PKCS12_bio(in, 0);
    if (p12 == 0) {
        /* Error loading PKCS12 file */
        goto cleanup;
    }
    /* See if an empty password will do */
    if (PKCS12_verify_mac(p12, "", 0) || PKCS12_verify_mac(p12, 0, 0)) {
        pass = "";
    }
    else {
        len = SSL_password_callback(buff, PEM_BUFSIZE, 0, (void *) c->password);
        if (len < 0) {
            /* Passpharse callback error */
            goto cleanup;
        }
        if (!PKCS12_verify_mac(p12, buff, len)) {
            /* Mac verify error (wrong password?) in PKCS12 file */
            goto cleanup;
        }
        pass = buff;
    }
    rc = PKCS12_parse(p12, pass, pkey, cert, ca);
cleanup:
    if (p12 != 0)
        PKCS12_free(p12);
    BIO_free(in);
    return rc;
}

static void free_and_reset_pass(tcn_ssl_ctxt_t *c, char* old_password, const jboolean rv) {
    if (!rv) {
        if (c->password != NULL) {
            free(c->password);
            c->password = NULL;
        }
        // Restore old password
        c->password = old_password;
    } else if (old_password != NULL) {
        free(old_password);
    }
}


TCN_IMPLEMENT_CALL(jboolean, SSLContext, setCertificate)(TCN_STDARGS, jlong ctx,
                                                         jstring cert, jstring key,
                                                         jstring password)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jboolean rv = JNI_TRUE;
    TCN_ALLOC_CSTRING(cert);
    TCN_ALLOC_CSTRING(key);
    TCN_ALLOC_CSTRING(password);
    EVP_PKEY *pkey = NULL;
    X509 *xcert = NULL;
    const char *key_file, *cert_file;
    const char *p;
    char *old_password = NULL;
    char err[256];

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    if (J2S(password)) {
        old_password = c->password;

        c->password = strdup(cpassword);
        if (c->password == NULL) {
            rv = JNI_FALSE;
            goto cleanup;
        }
    }
    key_file  = J2S(key);
    cert_file = J2S(cert);
    if (!key_file)
        key_file = cert_file;
    if (!key_file || !cert_file) {
        tcn_Throw(e, "No Certificate file specified or invalid file format");
        rv = JNI_FALSE;
        goto cleanup;
    }
    if ((p = strrchr(cert_file, '.')) != NULL && strcmp(p, ".pkcs12") == 0) {
        if (!ssl_load_pkcs12(c, cert_file, &pkey, &xcert, 0)) {
            ERR_error_string(ERR_get_error(), err);
            tcn_Throw(e, "Unable to load certificate %s (%s)",
                      cert_file, err);
            rv = JNI_FALSE;
            goto cleanup;
        }
    }
    else {
        if ((pkey = load_pem_key(c, key_file)) == NULL) {
            ERR_error_string(ERR_get_error(), err);
            tcn_Throw(e, "Unable to load certificate key %s (%s)",
                      key_file, err);
            rv = JNI_FALSE;
            goto cleanup;
        }
        if ((xcert = load_pem_cert(c, cert_file)) == NULL) {
            ERR_error_string(ERR_get_error(), err);
            tcn_Throw(e, "Unable to load certificate %s (%s)",
                      cert_file, err);
            rv = JNI_FALSE;
            goto cleanup;
        }
    }
    if (SSL_CTX_use_certificate(c->ctx, xcert) <= 0) {
        ERR_error_string(ERR_get_error(), err);
        tcn_Throw(e, "Error setting certificate (%s)", err);
        rv = JNI_FALSE;
        goto cleanup;
    }
    if (SSL_CTX_use_PrivateKey(c->ctx, pkey) <= 0) {
        ERR_error_string(ERR_get_error(), err);
        tcn_Throw(e, "Error setting private key (%s)", err);
        rv = JNI_FALSE;
        goto cleanup;
    }
    if (SSL_CTX_check_private_key(c->ctx) <= 0) {
        ERR_error_string(ERR_get_error(), err);
        tcn_Throw(e, "Private key does not match the certificate public key (%s)",
                  err);
        rv = JNI_FALSE;
        goto cleanup;
    }
cleanup:
    TCN_FREE_CSTRING(cert);
    TCN_FREE_CSTRING(key);
    TCN_FREE_CSTRING(password);
    EVP_PKEY_free(pkey); // this function is safe to call with NULL
    X509_free(xcert); // this function is safe to call with NULL
    free_and_reset_pass(c, old_password, rv);
    return rv;
}

TCN_IMPLEMENT_CALL(jboolean, SSLContext, setCertificateBio)(TCN_STDARGS, jlong ctx,
                                                         jlong cert, jlong key,
                                                         jstring password)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    BIO *cert_bio = J2P(cert, BIO *);
    BIO *key_bio = J2P(key, BIO *);
    EVP_PKEY *pkey = NULL;
    X509 *xcert = NULL;

    jboolean rv = JNI_TRUE;
    TCN_ALLOC_CSTRING(password);
    char *old_password = NULL;
    char err[256];

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    if (J2S(password)) {
        old_password = c->password;

        c->password = strdup(cpassword);
        if (c->password == NULL) {
            rv = JNI_FALSE;
            goto cleanup;
        }
    }

    if (!key)
        key = cert;
    if (!cert || !key) {
        tcn_Throw(e, "No Certificate file specified or invalid file format");
        rv = JNI_FALSE;
        goto cleanup;
    }

    if ((pkey = load_pem_key_bio(c->password, key_bio)) == NULL) {
        ERR_error_string(ERR_get_error(), err);
        ERR_clear_error();
        tcn_Throw(e, "Unable to load certificate key (%s)",err);
        rv = JNI_FALSE;
        goto cleanup;
    }
    if ((xcert = load_pem_cert_bio(c->password, cert_bio)) == NULL) {
        ERR_error_string(ERR_get_error(), err);
        ERR_clear_error();
        tcn_Throw(e, "Unable to load certificate (%s) ", err);
        rv = JNI_FALSE;
        goto cleanup;
    }

    if (SSL_CTX_use_certificate(c->ctx, xcert) <= 0) {
        ERR_error_string(ERR_get_error(), err);
        ERR_clear_error();
        tcn_Throw(e, "Error setting certificate (%s)", err);
        rv = JNI_FALSE;
        goto cleanup;
    }
    if (SSL_CTX_use_PrivateKey(c->ctx, pkey) <= 0) {
        ERR_error_string(ERR_get_error(), err);
        ERR_clear_error();
        tcn_Throw(e, "Error setting private key (%s)", err);
        rv = JNI_FALSE;
        goto cleanup;
    }
    if (SSL_CTX_check_private_key(c->ctx) <= 0) {
        ERR_error_string(ERR_get_error(), err);
        ERR_clear_error();

        tcn_Throw(e, "Private key does not match the certificate public key (%s)",
                  err);
        rv = JNI_FALSE;
        goto cleanup;
    }
cleanup:
    TCN_FREE_CSTRING(password);
    EVP_PKEY_free(pkey); // this function is safe to call with NULL
    X509_free(xcert); // this function is safe to call with NULL
    free_and_reset_pass(c, old_password, rv);
    return rv;
}

// Convert protos to wire format
static int initProtocols(JNIEnv *e, unsigned char **proto_data,
            unsigned int *proto_len, jobjectArray protos) {
    int i;
    unsigned char *p_data;
    // We start with allocate 128 bytes which should be good enough for most use-cases while still be pretty low.
    // We will call realloc to increase this if needed.
    size_t p_data_size = 128;
    size_t p_data_len = 0;
    jstring proto_string;
    const char *proto_chars;
    size_t proto_chars_len;
    int cnt;

    if (protos == NULL) {
        // Guard against NULL protos.
        return -1;
    }

    cnt = (*e)->GetArrayLength(e, protos);

    if (cnt == 0) {
        // if cnt is 0 we not need to continue and can just fail fast.
        return -1;
    }

    p_data = (unsigned char *) malloc(p_data_size);
    if (p_data == NULL) {
        // Not enough memory?
        return -1;
    }

    for (i = 0; i < cnt; ++i) {
         proto_string = (jstring) (*e)->GetObjectArrayElement(e, protos, i);
         proto_chars = (*e)->GetStringUTFChars(e, proto_string, 0);

         proto_chars_len = strlen(proto_chars);
         if (proto_chars_len > 0 && proto_chars_len <= MAX_ALPN_NPN_PROTO_SIZE) {
            // We need to add +1 as each protocol is prefixed by it's length (unsigned char).
            // For all except of the last one we already have the extra space as everything is
            // delimited by ','.
            p_data_len += 1 + proto_chars_len;
            if (p_data_len > p_data_size) {
                // double size
                p_data_size <<= 1;
                p_data = realloc(p_data, p_data_size);
                if (p_data == NULL) {
                    // Not enough memory?
                    (*e)->ReleaseStringUTFChars(e, proto_string, proto_chars);
                    break;
                }
            }
            // Write the length of the protocol and then increment before memcpy the protocol itself.
            *p_data = proto_chars_len;
            ++p_data;
            memcpy(p_data, proto_chars, proto_chars_len);
            p_data += proto_chars_len;
         }

         // Release the string to prevent memory leaks
         (*e)->ReleaseStringUTFChars(e, proto_string, proto_chars);
    }

    if (p_data == NULL) {
        // Something went wrong so update the proto_len and return -1
        *proto_len = 0;
        return -1;
    } else {
        if (*proto_data != NULL) {
            // Free old data
            free(*proto_data);
        }
        // Decrement pointer again as we incremented it while creating the protocols in wire format.
        p_data -= p_data_len;
        *proto_data = p_data;
        *proto_len = p_data_len;
        return 0;
    }
}

TCN_IMPLEMENT_CALL(void, SSLContext, setNpnProtos)(TCN_STDARGS, jlong ctx, jobjectArray next_protos,
        jint selectorFailureBehavior)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    TCN_ASSERT(ctx != 0);
    UNREFERENCED(o);

    if (initProtocols(e, &c->next_proto_data, &c->next_proto_len, next_protos) == 0) {
        c->next_selector_failure_behavior = selectorFailureBehavior;

        // depending on if it's client mode or not we need to call different functions.
        if (c->mode == SSL_MODE_CLIENT)  {
            SSL_CTX_set_next_proto_select_cb(c->ctx, SSL_callback_select_next_proto, (void *)c);
        } else {
            SSL_CTX_set_next_protos_advertised_cb(c->ctx, SSL_callback_next_protos, (void *)c);
        }
    }
}

TCN_IMPLEMENT_CALL(void, SSLContext, setAlpnProtos)(TCN_STDARGS, jlong ctx, jobjectArray alpn_protos,
        jint selectorFailureBehavior)
{
    // Only supported with GCC
    #if !defined(OPENSSL_IS_BORINGSSL) && (defined(__GNUC__) || defined(__GNUG__))
        if (!SSL_CTX_set_alpn_protos || !SSL_CTX_set_alpn_select_cb) {
            UNREFERENCED_STDARGS;
            UNREFERENCED(ctx);
            UNREFERENCED(alpn_protos);
            return;
        }
    #endif

    // We can only support it when either use openssl version >= 1.0.2 or GCC as this way we can use weak linking
    #if OPENSSL_VERSION_NUMBER >= 0x10002000L || defined(__GNUC__) || defined(__GNUG__)
        tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

        TCN_ASSERT(ctx != 0);
        UNREFERENCED(o);

        if (initProtocols(e, &c->alpn_proto_data, &c->alpn_proto_len, alpn_protos) == 0) {
            c->alpn_selector_failure_behavior = selectorFailureBehavior;

            // depending on if it's client mode or not we need to call different functions.
            if (c->mode == SSL_MODE_CLIENT)  {
                SSL_CTX_set_alpn_protos(c->ctx, c->alpn_proto_data, c->alpn_proto_len);
            } else {
                SSL_CTX_set_alpn_select_cb(c->ctx, SSL_callback_alpn_select_proto, (void *) c);

            }
        }
    #else
        UNREFERENCED_STDARGS;
        UNREFERENCED(ctx);
        UNREFERENCED(alpn_protos);
    #endif
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, setSessionCacheMode)(TCN_STDARGS, jlong ctx, jlong mode)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    return SSL_CTX_set_session_cache_mode(c->ctx, mode);
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, getSessionCacheMode)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    return SSL_CTX_get_session_cache_mode(c->ctx);
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, setSessionCacheTimeout)(TCN_STDARGS, jlong ctx, jlong timeout)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_set_timeout(c->ctx, timeout);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, getSessionCacheTimeout)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    return SSL_CTX_get_timeout(c->ctx);
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, setSessionCacheSize)(TCN_STDARGS, jlong ctx, jlong size)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = 0;

    // Also allow size of 0 which is unlimited
    if (size >= 0) {
      SSL_CTX_set_session_cache_mode(c->ctx, SSL_SESS_CACHE_SERVER);
      rv = SSL_CTX_sess_set_cache_size(c->ctx, size);
    }

    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, getSessionCacheSize)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    return SSL_CTX_sess_get_cache_size(c->ctx);
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionNumber)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_number(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionConnect)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_connect(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionConnectGood)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_connect_good(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionConnectRenegotiate)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_connect_renegotiate(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionAccept)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_accept(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionAcceptGood)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_accept_good(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionAcceptRenegotiate)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_accept_renegotiate(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionHits)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_hits(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionCbHits)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_cb_hits(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionMisses)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_misses(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionTimeouts)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_timeouts(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionCacheFull)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = SSL_CTX_sess_cache_full(c->ctx);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionTicketKeyNew)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = apr_atomic_read32(&c->ticket_keys_new);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionTicketKeyResume)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = apr_atomic_read32(&c->ticket_keys_resume);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionTicketKeyRenew)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = apr_atomic_read32(&c->ticket_keys_renew);
    return rv;
}

TCN_IMPLEMENT_CALL(jlong, SSLContext, sessionTicketKeyFail)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jlong rv = apr_atomic_read32(&c->ticket_keys_fail);
    return rv;
}

static int current_session_key(tcn_ssl_ctxt_t *c, tcn_ssl_ticket_key_t *key) {
    int result = JNI_FALSE;
    apr_thread_rwlock_rdlock(c->mutex);
    if (c->ticket_keys_len > 0) {
        *key = c->ticket_keys[0];
        result = JNI_TRUE;
    }
    apr_thread_rwlock_unlock(c->mutex);
    return result;
}

static int find_session_key(tcn_ssl_ctxt_t *c, unsigned char key_name[16], tcn_ssl_ticket_key_t *key, int *is_current_key) {
    int result = JNI_FALSE;
    int i;

    apr_thread_rwlock_rdlock(c->mutex);
    for (i = 0; i < c->ticket_keys_len; ++i) {
        // Check if we have a match for tickets.
        if (memcmp(c->ticket_keys[i].key_name, key_name, 16) == 0) {
            *key = c->ticket_keys[i];
            result = JNI_TRUE;
            *is_current_key = (i == 0);
            break;
        }
    }
    apr_thread_rwlock_unlock(c->mutex);
    return result;
}

static int ssl_tlsext_ticket_key_cb(SSL *s, unsigned char key_name[16], unsigned char *iv, EVP_CIPHER_CTX *ctx, HMAC_CTX *hctx, int enc) {
     tcn_ssl_ctxt_t *c = SSL_get_app_data2(s);
     tcn_ssl_ticket_key_t key;
     int is_current_key;

     if (enc) { /* create new session */
         if (current_session_key(c, &key)) {
             if (RAND_bytes(iv, EVP_MAX_IV_LENGTH) <= 0) {
                 return -1; /* insufficient random */
             }

             memcpy(key_name, key.key_name, 16);

             EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key.aes_key, iv);
             HMAC_Init_ex(hctx, key.hmac_key, 16, EVP_sha256(), NULL);
             apr_atomic_inc32(&c->ticket_keys_new);
             return 1;
         }
         // No ticket configured
         return 0;
     } else { /* retrieve session */
         if (find_session_key(c, key_name, &key, &is_current_key)) {
             HMAC_Init_ex(hctx, key.hmac_key, 16, EVP_sha256(), NULL);
             EVP_DecryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key.aes_key, iv );
             if (!is_current_key) {
                 // The ticket matched a key in the list, and we want to upgrade it to the current
                 // key.
                 apr_atomic_inc32(&c->ticket_keys_renew);
                 return 2;
             }
             // The ticket matched the current key.
             apr_atomic_inc32(&c->ticket_keys_resume);
             return 1;
         }
         // No matching ticket.
         apr_atomic_inc32(&c->ticket_keys_fail);
         return 0;
     }
}

TCN_IMPLEMENT_CALL(void, SSLContext, setSessionTicketKeys0)(TCN_STDARGS, jlong ctx, jbyteArray keys)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    jbyte* b;
    jbyte* key;
    tcn_ssl_ticket_key_t* ticket_keys;
    int i;
    int cnt;

    cnt = (*e)->GetArrayLength(e, keys) / SSL_SESSION_TICKET_KEY_SIZE;
    b = (*e)->GetByteArrayElements(e, keys, NULL);

    ticket_keys = malloc(sizeof(tcn_ssl_ticket_key_t) * cnt);

    for (i = 0; i < cnt; ++i) {
        key = b + (SSL_SESSION_TICKET_KEY_SIZE * i);
        memcpy(ticket_keys[i].key_name, key, 16);
        memcpy(ticket_keys[i].hmac_key, key + 16, 16);
        memcpy(ticket_keys[i].aes_key, key + 32, 16);
    }

    (*e)->ReleaseByteArrayElements(e, keys, b, 0);

    apr_thread_rwlock_wrlock(c->mutex);
    if (c->ticket_keys) {
        free(c->ticket_keys);
    }
    c->ticket_keys_len = cnt;
    c->ticket_keys = ticket_keys;
    apr_thread_rwlock_unlock(c->mutex);

    SSL_CTX_set_tlsext_ticket_key_cb(c->ctx, ssl_tlsext_ticket_key_cb);
}

static const char* authentication_method(const SSL* ssl) {
{
    const STACK_OF(SSL_CIPHER) *ciphers = NULL;

    switch (SSL_version(ssl))
        {
        case SSL2_VERSION:
            return SSL_TXT_RSA;
        default:
            ciphers = SSL_get_ciphers(ssl);
            if (ciphers == NULL || sk_SSL_CIPHER_num(ciphers) <= 0) {
                // No cipher available so return UNKNOWN.
                return TCN_UNKNOWN_AUTH_METHOD;
            }
            return SSL_cipher_authentication_method(sk_SSL_CIPHER_value(ciphers, 0));
        }
    }
}
/* Android end */

static int SSL_cert_verify(X509_STORE_CTX *ctx, void *arg) {
    /* Get Apache context back through OpenSSL context */
    SSL *ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
    TCN_ASSERT(ssl != NULL);
    tcn_ssl_ctxt_t *c = SSL_get_app_data2(ssl);
    TCN_ASSERT(c != NULL);
    tcn_ssl_verify_config_t* verify_config = SSL_get_app_data4(ssl);
    TCN_ASSERT(verify_config != NULL);

    // Get a stack of all certs in the chain
    STACK_OF(X509) *sk = X509_STORE_CTX_get0_untrusted(ctx);

    // SSL_CTX_set_verify_depth() and SSL_set_verify_depth() set the limit up to which depth certificates in a chain are
    // used during the verification procedure. If the certificate chain is longer than allowed, the certificates above
    // the limit are ignored. Error messages are generated as if these certificates would not be present,
    // most likely a X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY will be issued.
    // https://www.openssl.org/docs/man1.0.2/ssl/SSL_set_verify.html
    const int totalQueuedLength = sk_X509_num(sk);
    int len = TCN_MIN(verify_config->verify_depth, totalQueuedLength);
    unsigned i;
    X509 *cert;
    int length;
    unsigned char *buf;
    JNIEnv *e;
    jbyteArray array;
    jbyteArray bArray;
    const char *authMethod;
    jstring authMethodString;
    jint result;
    jclass byteArrayClass = tcn_get_byte_array_class();
    tcn_get_java_env(&e);

    // Create the byte[][] array that holds all the certs
    array = (*e)->NewObjectArray(e, len, byteArrayClass, NULL);

    for(i = 0; i < len; i++) {
        cert = sk_X509_value(sk, i);

        buf = NULL;
        length = i2d_X509(cert, &buf);
        if (length < 0) {
            // In case of error just return an empty byte[][]
            array = (*e)->NewObjectArray(e, 0, byteArrayClass, NULL);
            if (buf != NULL) {
                // We need to delete the local references so we not leak memory as this method is called via callback.
                OPENSSL_free(buf);
            }
            break;
        }
        bArray = (*e)->NewByteArray(e, length);
        (*e)->SetByteArrayRegion(e, bArray, 0, length, (jbyte*) buf);
        (*e)->SetObjectArrayElement(e, array, i, bArray);

        // Delete the local reference as we not know how long the chain is and local references are otherwise
        // only freed once jni method returns.
        (*e)->DeleteLocalRef(e, bArray);
        OPENSSL_free(buf);
    }

    authMethod = authentication_method(ssl);
    authMethodString = (*e)->NewStringUTF(e, authMethod);

    result = (*e)->CallIntMethod(e, c->verifier, c->verifier_method, P2J(ssl), array, authMethodString);

#ifdef X509_V_ERR_UNSPECIFIED
    // If we failed to verify for an unknown reason (currently this happens if we can't find a common root) then we should
    // fail with the same status as recommended in the OpenSSL docs https://www.openssl.org/docs/man1.0.2/ssl/SSL_set_verify.html
    if (result == X509_V_ERR_UNSPECIFIED && len < totalQueuedLength) {
        result = X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY;
    }
#else
    // HACK!
    // LibreSSL 2.4.x doesn't support the X509_V_ERR_UNSPECIFIED so we introduce a work around to make sure a supported alert is used.
    // This should be reverted when we support LibreSSL 2.5.x (which does support X509_V_ERR_UNSPECIFIED).
    if (result == TCN_X509_V_ERR_UNSPECIFIED) {
        result = len < totalQueuedLength ? X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY : X509_V_ERR_CERT_REJECTED;
    }
#endif

    // TODO(scott): if verify_config->verify_depth == SSL_CVERIFY_OPTIONAL we have the option to let the handshake
    // succeed for some of the "informational" error messages (e.g. X509_V_ERR_EMAIL_MISMATCH ?)

    // Set the correct error so it will be included in the alert.
    X509_STORE_CTX_set_error(ctx, result);

    // We need to delete the local references so we not leak memory as this method is called via callback.
    (*e)->DeleteLocalRef(e, authMethodString);
    (*e)->DeleteLocalRef(e, array);

    return result == X509_V_OK ? 1 : 0;
}

TCN_IMPLEMENT_CALL(void, SSLContext, setCertVerifyCallback)(TCN_STDARGS, jlong ctx, jobject verifier)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    if (verifier == NULL) {
        SSL_CTX_set_cert_verify_callback(c->ctx, NULL, NULL);
    } else {
        jclass verifier_class = (*e)->GetObjectClass(e, verifier);
        jmethodID method = (*e)->GetMethodID(e, verifier_class, "verify", "(J[[BLjava/lang/String;)I");

        if (method == NULL) {
            return;
        }
        // Delete the reference to the previous specified verifier if needed.
        if (c->verifier != NULL) {
            (*e)->DeleteLocalRef(e, c->verifier);
        }
        c->verifier = (*e)->NewGlobalRef(e, verifier);
        c->verifier_method = method;

        SSL_CTX_set_cert_verify_callback(c->ctx, SSL_cert_verify, NULL);
    }
}

/**
 * Returns an array containing all the X500 principal's bytes.
 *
 * Partly based on code from conscrypt:
 * https://android.googlesource.com/platform/external/conscrypt/+/master/src/main/native/org_conscrypt_NativeCrypto.cpp
 */
static jobjectArray principalBytes(JNIEnv* e, const STACK_OF(X509_NAME)* names) {
    jobjectArray array;
    jbyteArray bArray;
    int i;
    int count;
    int length;
    unsigned char *buf;
    X509_NAME* principal;
    jclass byteArrayClass = tcn_get_byte_array_class();

    if (names == NULL) {
        return NULL;
    }

    count = sk_X509_NAME_num(names);
    if (count <= 0) {
        return NULL;
    }

    array = (*e)->NewObjectArray(e, count, byteArrayClass, NULL);
    if (array == NULL) {
        return NULL;
    }

    for (i = 0; i < count; i++) {
        principal = sk_X509_NAME_value(names, i);
        buf = NULL;
        length = i2d_X509_NAME(principal, &buf);
        if (length < 0) {
            if (buf != NULL) {
                // We need to delete the local references so we not leak memory as this method is called via callback.
                OPENSSL_free(buf);
            }
            // In case of error just return an empty byte[][]
            return (*e)->NewObjectArray(e, 0, byteArrayClass, NULL);
        }
        bArray = (*e)->NewByteArray(e, length);
        (*e)->SetByteArrayRegion(e, bArray, 0, length, (jbyte*) buf);
        (*e)->SetObjectArrayElement(e, array, i, bArray);

        // Delete the local reference as we not know how long the chain is and local references are otherwise
        // only freed once jni method returns.
        (*e)->DeleteLocalRef(e, bArray);
        OPENSSL_free(buf);
    }

    return array;
}

static int cert_requested(SSL* ssl, X509** x509Out, EVP_PKEY** pkeyOut) {
#if defined(LIBRESSL_VERSION_NUMBER)
    return -1;
#else
    tcn_ssl_ctxt_t *c = SSL_get_app_data2(ssl);
    int ctype_num;
    jbyte* ctype_bytes;
    jobjectArray issuers;
    JNIEnv *e;
    jbyteArray keyTypes;
    jobject keyMaterial;
    STACK_OF(X509) *chain = NULL;
    X509 *cert = NULL;
    EVP_PKEY* pkey = NULL;
    jlong certChain;
    jlong privateKey;
    int certChainLen;
    int i;

    tcn_get_java_env(&e);

#if OPENSSL_VERSION_NUMBER < 0x10002000L
    char ssl2_ctype = SSL3_CT_RSA_SIGN;
    switch (ssl->version) {
        case SSL2_VERSION:
            ctype_bytes = (jbyte*) &ssl2_ctype;
            ctype_num = 1;
            break;
        case SSL3_VERSION:
        case TLS1_VERSION:
        case TLS1_1_VERSION:
        case TLS1_2_VERSION:
        case DTLS1_VERSION:
            ctype_bytes = (jbyte*) ssl->s3->tmp.ctype;
            ctype_num = ssl->s3->tmp.ctype_num;
            break;
    }
#else
    ctype_num = SSL_get0_certificate_types(ssl, (const uint8_t **) &ctype_bytes);
#endif
    if (ctype_num <= 0) {
        // Use no certificate
        return 0;
    }
    keyTypes = (*e)->NewByteArray(e, ctype_num);
    if (keyTypes == NULL) {
        // Something went seriously wrong, bail out!
        return -1;
    }
    (*e)->SetByteArrayRegion(e, keyTypes, 0, ctype_num, ctype_bytes);

    issuers = principalBytes(e,  SSL_get_client_CA_list(ssl));

    // Execute the java callback
    keyMaterial = (*e)->CallObjectMethod(e, c->cert_requested_callback, c->cert_requested_callback_method, P2J(ssl), keyTypes, issuers);
    if (keyMaterial == NULL) {
        return 0;
    }

    // Any failure after this line must cause a goto fail to cleanup things.
    certChain = (*e)->GetLongField(e, keyMaterial, tcn_get_key_material_certificate_chain_field());
    privateKey = (*e)->GetLongField(e, keyMaterial, tcn_get_key_material_private_key_field());

    chain = J2P(certChain, STACK_OF(X509) *);
    pkey = J2P(privateKey, EVP_PKEY *);

    if (chain == NULL || pkey == NULL) {
        goto fail;
    }

    certChainLen = sk_X509_num(chain);

    if (certChainLen <= 0) {
       goto fail;
    }

    // Skip the first cert in the chain as we will write this to x509Out.
    // See https://github.com/netty/netty-tcnative/issues/184
    for (i = 1; i < certChainLen; ++i) {
        // We need to explicit add extra certs to the chain as stated in:
        // https://www.openssl.org/docs/manmaster/ssl/SSL_CTX_set_client_cert_cb.html
        //
        // Using SSL_add0_chain_cert(...) here as we not want to increment the reference count.
        if (SSL_add0_chain_cert(ssl, sk_X509_value(chain, i)) <= 0) {
            goto fail;
        }
    }

    cert = sk_X509_value(chain, 0);
    // Increment the reference count as we already set the chain via SSL_set0_chain(...) and using a cert out of it.
    if (tcn_X509_up_ref(cert) <= 0) {
        goto fail;
    }
    *x509Out = cert;
    *pkeyOut = pkey;

    // Free the stack it self but not the certs.
    sk_X509_free(chain);
    return 1;
fail:
    ERR_clear_error();
    sk_X509_pop_free(chain, X509_free);
    EVP_PKEY_free(pkey);

    // TODO: Would it be more correct to return 0 in this case we may not want to use any cert / private key ?
    return -1;
#endif /* defined(LIBRESSL_VERSION_NUMBER) */
}

TCN_IMPLEMENT_CALL(void, SSLContext, setCertRequestedCallback)(TCN_STDARGS, jlong ctx, jobject callback)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    if (callback == NULL) {
        SSL_CTX_set_client_cert_cb(c->ctx, NULL);
    } else {
        jclass callback_class = (*e)->GetObjectClass(e, callback);
        jmethodID method = (*e)->GetMethodID(e, callback_class, "requested", "(J[B[[B)Lio/netty/internal/tcnative/CertificateRequestedCallback$KeyMaterial;");
        if (method == NULL) {
            return;
        }
        // Delete the reference to the previous specified verifier if needed.
        if (c->cert_requested_callback != NULL) {
            (*e)->DeleteLocalRef(e, c->cert_requested_callback);
        }
        c->cert_requested_callback = (*e)->NewGlobalRef(e, callback);
        c->cert_requested_callback_method = method;

        SSL_CTX_set_client_cert_cb(c->ctx, cert_requested);
    }
}

TCN_IMPLEMENT_CALL(jboolean, SSLContext, setSessionIdContext)(TCN_STDARGS, jlong ctx, jbyteArray sidCtx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);
    int len = (*e)->GetArrayLength(e, sidCtx);
    unsigned char *buf;
    int res;

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    buf = malloc(len);

    (*e)->GetByteArrayRegion(e, sidCtx, 0, len, (jbyte*) buf);

    res = SSL_CTX_set_session_id_context(c->ctx, buf, len);
    free(buf);

    if (res == 1) {
        return JNI_TRUE;
    }
    return JNI_FALSE;
}

TCN_IMPLEMENT_CALL(jint, SSLContext, setMode)(TCN_STDARGS, jlong ctx, jint mode)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    return (jint) SSL_CTX_set_mode(c->ctx, mode);
}


TCN_IMPLEMENT_CALL(jint, SSLContext, getMode)(TCN_STDARGS, jlong ctx)
{
    tcn_ssl_ctxt_t *c = J2P(ctx, tcn_ssl_ctxt_t *);

    UNREFERENCED(o);
    TCN_ASSERT(ctx != 0);

    return (jint) SSL_CTX_get_mode(c->ctx);
}