xref: /unit/src/nxt_openssl.c (revision 1828)

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) NGINX, Inc.
 */

#include <nxt_main.h>
#include <openssl/ssl.h>
#include <openssl/conf.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <openssl/x509v3.h>


typedef struct {
    SSL             *session;
    nxt_conn_t      *conn;

    int             ssl_error;
    uint8_t         times;      /* 2 bits */
    uint8_t         handshake;  /* 1 bit  */

    nxt_tls_conf_t  *conf;
    nxt_buf_mem_t   buffer;
} nxt_openssl_conn_t;


typedef enum {
    NXT_OPENSSL_HANDSHAKE = 0,
    NXT_OPENSSL_READ,
    NXT_OPENSSL_WRITE,
    NXT_OPENSSL_SHUTDOWN,
} nxt_openssl_io_t;


static nxt_int_t nxt_openssl_library_init(nxt_task_t *task);
static void nxt_openssl_library_free(nxt_task_t *task);
#if OPENSSL_VERSION_NUMBER < 0x10100004L
static nxt_int_t nxt_openssl_locks_init(void);
static void nxt_openssl_lock(int mode, int type, const char *file, int line);
static unsigned long nxt_openssl_thread_id(void);
static void nxt_openssl_locks_free(void);
#endif
static nxt_int_t nxt_openssl_server_init(nxt_task_t *task,
    nxt_tls_conf_t *conf, nxt_mp_t *mp, nxt_bool_t last);
static nxt_int_t nxt_openssl_chain_file(nxt_task_t *task, SSL_CTX *ctx,
    nxt_tls_conf_t *conf, nxt_mp_t *mp, nxt_bool_t single);
static nxt_uint_t nxt_openssl_cert_get_names(nxt_task_t *task, X509 *cert,
    nxt_tls_conf_t *conf, nxt_mp_t *mp);
static nxt_int_t nxt_openssl_bundle_hash_test(nxt_lvlhsh_query_t *lhq,
    void *data);
static nxt_int_t nxt_openssl_bundle_hash_insert(nxt_task_t *task,
    nxt_lvlhsh_t *lvlhsh, nxt_tls_bundle_hash_item_t *item, nxt_mp_t * mp);
static nxt_int_t nxt_openssl_servername(SSL *s, int *ad, void *arg);
static nxt_tls_bundle_conf_t *nxt_openssl_find_ctx(nxt_tls_conf_t *conf,
    nxt_str_t *sn);
static void nxt_openssl_server_free(nxt_task_t *task, nxt_tls_conf_t *conf);
static void nxt_openssl_conn_init(nxt_task_t *task, nxt_tls_conf_t *conf,
    nxt_conn_t *c);
static void nxt_openssl_conn_handshake(nxt_task_t *task, void *obj, void *data);
static ssize_t nxt_openssl_conn_io_recvbuf(nxt_conn_t *c, nxt_buf_t *b);
static ssize_t nxt_openssl_conn_io_sendbuf(nxt_task_t *task, nxt_sendbuf_t *sb);
static ssize_t nxt_openssl_conn_io_send(nxt_task_t *task, nxt_sendbuf_t *sb,
    void *buf, size_t size);
static void nxt_openssl_conn_io_shutdown(nxt_task_t *task, void *obj,
    void *data);
static nxt_int_t nxt_openssl_conn_test_error(nxt_task_t *task, nxt_conn_t *c,
    int ret, nxt_err_t sys_err, nxt_openssl_io_t io);
static void nxt_cdecl nxt_openssl_conn_error(nxt_task_t *task,
    nxt_err_t err, const char *fmt, ...);
static nxt_uint_t nxt_openssl_log_error_level(nxt_err_t err);


const nxt_tls_lib_t  nxt_openssl_lib = {
    .library_init = nxt_openssl_library_init,
    .library_free = nxt_openssl_library_free,

    .server_init = nxt_openssl_server_init,
    .server_free = nxt_openssl_server_free,
};


static nxt_conn_io_t  nxt_openssl_conn_io = {
    .read = nxt_conn_io_read,
    .recvbuf = nxt_openssl_conn_io_recvbuf,

    .write = nxt_conn_io_write,
    .sendbuf = nxt_openssl_conn_io_sendbuf,

    .shutdown = nxt_openssl_conn_io_shutdown,
};


static long  nxt_openssl_version;
static int   nxt_openssl_connection_index;


static nxt_int_t
nxt_openssl_library_init(nxt_task_t *task)
{
    int  index;

    if (nxt_fast_path(nxt_openssl_version != 0)) {
        return NXT_OK;
    }

#if OPENSSL_VERSION_NUMBER >= 0x10100003L

    OPENSSL_init_ssl(OPENSSL_INIT_LOAD_CONFIG, NULL);

#else
    {
        nxt_int_t  ret;

        SSL_load_error_strings();

        OPENSSL_config(NULL);

        /*
         * SSL_library_init(3):
         *
         *   SSL_library_init() always returns "1",
         *   so it is safe to discard the return value.
         */
        (void) SSL_library_init();

        ret = nxt_openssl_locks_init();
        if (nxt_slow_path(ret != NXT_OK)) {
            return ret;
        }
    }

#endif

    nxt_openssl_version = SSLeay();

    nxt_log(task, NXT_LOG_INFO, "%s, %xl",
            SSLeay_version(SSLEAY_VERSION), nxt_openssl_version);

#ifndef SSL_OP_NO_COMPRESSION
    {
        /*
         * Disable gzip compression in OpenSSL prior to 1.0.0
         * version, this saves about 522K per connection.
         */
        int                 n;
        STACK_OF(SSL_COMP)  *ssl_comp_methods;

        ssl_comp_methods = SSL_COMP_get_compression_methods();

        for (n = sk_SSL_COMP_num(ssl_comp_methods); n != 0; n--) {
            (void) sk_SSL_COMP_pop(ssl_comp_methods);
        }
    }
#endif

    index = SSL_get_ex_new_index(0, NULL, NULL, NULL, NULL);

    if (index == -1) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT,
                              "SSL_get_ex_new_index() failed");
        return NXT_ERROR;
    }

    nxt_openssl_connection_index = index;

    return NXT_OK;
}


#if OPENSSL_VERSION_NUMBER >= 0x10100003L

static void
nxt_openssl_library_free(nxt_task_t *task)
{
}

#else

static nxt_thread_mutex_t  *nxt_openssl_locks;

static nxt_int_t
nxt_openssl_locks_init(void)
{
    int        i, n;
    nxt_int_t  ret;

    n = CRYPTO_num_locks();

    nxt_openssl_locks = OPENSSL_malloc(n * sizeof(nxt_thread_mutex_t));
    if (nxt_slow_path(nxt_openssl_locks == NULL)) {
        return NXT_ERROR;
    }

    for (i = 0; i < n; i++) {
        ret = nxt_thread_mutex_create(&nxt_openssl_locks[i]);
        if (nxt_slow_path(ret != NXT_OK)) {
            return ret;
        }
    }

    CRYPTO_set_locking_callback(nxt_openssl_lock);

    CRYPTO_set_id_callback(nxt_openssl_thread_id);

    return NXT_OK;
}


static void
nxt_openssl_lock(int mode, int type, const char *file, int line)
{
    nxt_thread_mutex_t  *lock;

    lock = &nxt_openssl_locks[type];

    if ((mode & CRYPTO_LOCK) != 0) {
        (void) nxt_thread_mutex_lock(lock);

    } else {
        (void) nxt_thread_mutex_unlock(lock);
    }
}


static u_long
nxt_openssl_thread_id(void)
{
    return (u_long) nxt_thread_handle();
}


static void
nxt_openssl_library_free(nxt_task_t *task)
{
    nxt_openssl_locks_free();
}


static void
nxt_openssl_locks_free(void)
{
    int  i, n;

    n = CRYPTO_num_locks();

    CRYPTO_set_locking_callback(NULL);

    for (i = 0; i < n; i++) {
        nxt_thread_mutex_destroy(&nxt_openssl_locks[i]);
    }

    OPENSSL_free(nxt_openssl_locks);
}

#endif


static nxt_int_t
nxt_openssl_server_init(nxt_task_t *task, nxt_tls_conf_t *conf,
    nxt_mp_t *mp, nxt_bool_t last)
{
    SSL_CTX                *ctx;
    const char             *ciphers, *ca_certificate;
    STACK_OF(X509_NAME)    *list;
    nxt_tls_bundle_conf_t  *bundle;

    ctx = SSL_CTX_new(SSLv23_server_method());
    if (ctx == NULL) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT, "SSL_CTX_new() failed");
        return NXT_ERROR;
    }

    bundle = conf->bundle;
    nxt_assert(bundle != NULL);

    bundle->ctx = ctx;

#ifdef SSL_OP_NO_RENEGOTIATION
    /* Renegration is not currently supported. */
    SSL_CTX_set_options(ctx, SSL_OP_NO_RENEGOTIATION);
#endif

#ifdef SSL_OP_NO_COMPRESSION
    /*
     * Disable gzip compression in OpenSSL 1.0.0,
     * this saves about 522K per connection.
     */
    SSL_CTX_set_options(ctx, SSL_OP_NO_COMPRESSION);
#endif

#ifdef SSL_MODE_RELEASE_BUFFERS

    if (nxt_openssl_version >= 10001078) {
        /*
         * Allow to release read and write buffers in OpenSSL 1.0.0,
         * this saves about 34K per idle connection.  It is not safe
         * before OpenSSL 1.0.1h (CVE-2010-5298).
         */
        SSL_CTX_set_mode(ctx, SSL_MODE_RELEASE_BUFFERS);
    }

#endif

    if (nxt_openssl_chain_file(task, ctx, conf, mp,
                               last && bundle->next == NULL)
        != NXT_OK)
    {
        goto fail;
    }
/*
    key = conf->certificate_key;

    if (SSL_CTX_use_PrivateKey_file(ctx, key, SSL_FILETYPE_PEM) == 0) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT,
                              "SSL_CTX_use_PrivateKey_file(\"%s\") failed",
                              key);
        goto fail;
    }
*/
    ciphers = (conf->ciphers != NULL) ? conf->ciphers : "HIGH:!aNULL:!MD5";

    if (SSL_CTX_set_cipher_list(ctx, ciphers) == 0) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT,
                              "SSL_CTX_set_cipher_list(\"%s\") failed",
                              ciphers);
        goto fail;
    }

    SSL_CTX_set_options(ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);

    if (conf->ca_certificate != NULL) {

        /* TODO: verify callback */
        SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);

        /* TODO: verify depth */
        SSL_CTX_set_verify_depth(ctx, 1);

        ca_certificate = conf->ca_certificate;

        if (SSL_CTX_load_verify_locations(ctx, ca_certificate, NULL) == 0) {
            nxt_openssl_log_error(task, NXT_LOG_ALERT,
                              "SSL_CTX_load_verify_locations(\"%s\") failed",
                              ca_certificate);
            goto fail;
        }

        list = SSL_load_client_CA_file(ca_certificate);

        if (list == NULL) {
            nxt_openssl_log_error(task, NXT_LOG_ALERT,
                              "SSL_load_client_CA_file(\"%s\") failed",
                              ca_certificate);
            goto fail;
        }

        /*
         * SSL_load_client_CA_file() in OpenSSL prior to 0.9.7h and
         * 0.9.8 versions always leaves an error in the error queue.
         */
        ERR_clear_error();

        SSL_CTX_set_client_CA_list(ctx, list);
    }

    if (last) {
        conf->conn_init = nxt_openssl_conn_init;

        if (bundle->next != NULL) {
            SSL_CTX_set_tlsext_servername_callback(ctx, nxt_openssl_servername);
        }
    }

    return NXT_OK;

fail:

    SSL_CTX_free(ctx);

#if (OPENSSL_VERSION_NUMBER >= 0x1010100fL \
     && OPENSSL_VERSION_NUMBER < 0x1010101fL)
    RAND_keep_random_devices_open(0);
#endif

    return NXT_ERROR;
}


static nxt_int_t
nxt_openssl_chain_file(nxt_task_t *task, SSL_CTX *ctx, nxt_tls_conf_t *conf,
    nxt_mp_t *mp, nxt_bool_t single)
{
    BIO                    *bio;
    X509                   *cert, *ca;
    long                   reason;
    EVP_PKEY               *key;
    nxt_int_t              ret;
    nxt_tls_bundle_conf_t  *bundle;

    ret = NXT_ERROR;
    cert = NULL;

    bio = BIO_new(BIO_s_fd());
    if (bio == NULL) {
        goto end;
    }

    bundle = conf->bundle;

    BIO_set_fd(bio, bundle->chain_file, BIO_CLOSE);

    cert = PEM_read_bio_X509_AUX(bio, NULL, NULL, NULL);
    if (cert == NULL) {
        goto end;
    }

    if (SSL_CTX_use_certificate(ctx, cert) != 1) {
        goto end;
    }

    if (!single && nxt_openssl_cert_get_names(task, cert, conf, mp) != NXT_OK) {
        goto clean;
    }

    for ( ;; ) {
        ca = PEM_read_bio_X509(bio, NULL, NULL, NULL);

        if (ca == NULL) {
            reason = ERR_GET_REASON(ERR_peek_last_error());
            if (reason != PEM_R_NO_START_LINE) {
                goto end;
            }

            ERR_clear_error();
            break;
        }

        /*
         * Note that ca isn't freed if it was successfully added to the chain,
         * while the main certificate needs a X509_free() call, since
         * its reference count is increased by SSL_CTX_use_certificate().
         */
#ifdef SSL_CTX_add0_chain_cert
        if (SSL_CTX_add0_chain_cert(ctx, ca) != 1) {
#else
        if (SSL_CTX_add_extra_chain_cert(ctx, ca) != 1) {
#endif
            X509_free(ca);
            goto end;
        }
    }

    if (BIO_reset(bio) != 0) {
        goto end;
    }

    key = PEM_read_bio_PrivateKey(bio, NULL, NULL, NULL);
    if (key == NULL) {
        goto end;
    }

    if (SSL_CTX_use_PrivateKey(ctx, key) == 1) {
        ret = NXT_OK;
    }

    EVP_PKEY_free(key);

end:

    if (ret != NXT_OK) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT,
                              "nxt_openssl_chain_file() failed");
    }

clean:

    BIO_free(bio);
    X509_free(cert);

    return ret;
}


static nxt_uint_t
nxt_openssl_cert_get_names(nxt_task_t *task, X509 *cert, nxt_tls_conf_t *conf,
    nxt_mp_t *mp)
{
    int                         len;
    nxt_str_t                   domain, str;
    X509_NAME                   *x509_name;
    nxt_uint_t                  i, n;
    GENERAL_NAME                *name;
    nxt_tls_bundle_conf_t       *bundle;
    STACK_OF(GENERAL_NAME)      *alt_names;
    nxt_tls_bundle_hash_item_t  *item;

    bundle = conf->bundle;

    alt_names = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL);

    if (alt_names != NULL) {
        n = sk_GENERAL_NAME_num(alt_names);

        for (i = 0; i != n; i++) {
            name = sk_GENERAL_NAME_value(alt_names, i);

            if (name->type != GEN_DNS) {
                continue;
            }

            str.length = ASN1_STRING_length(name->d.dNSName);
#if OPENSSL_VERSION_NUMBER > 0x10100000L
            str.start = (u_char *) ASN1_STRING_get0_data(name->d.dNSName);
#else
            str.start = ASN1_STRING_data(name->d.dNSName);
#endif

            domain.start = nxt_mp_nget(mp, str.length);
            if (nxt_slow_path(domain.start == NULL)) {
                goto fail;
            }

            domain.length = str.length;
            nxt_memcpy_lowcase(domain.start, str.start, str.length);

            item = nxt_mp_get(mp, sizeof(nxt_tls_bundle_hash_item_t));
            if (nxt_slow_path(item == NULL)) {
                goto fail;
            }

            item->name = domain;
            item->bundle = bundle;

            if (nxt_openssl_bundle_hash_insert(task, &conf->bundle_hash,
                                               item, mp)
                == NXT_ERROR)
            {
                goto fail;
            }
        }

        sk_GENERAL_NAME_pop_free(alt_names, GENERAL_NAME_free);

    } else {
        x509_name = X509_get_subject_name(cert);
        len = X509_NAME_get_text_by_NID(x509_name, NID_commonName,
                                        NULL, 0);
        if (len <= 0) {
            nxt_log(task, NXT_LOG_WARN, "certificate \"%V\" has neither "
                    "Subject Alternative Name nor Common Name", bundle->name);
            return NXT_OK;
        }

        domain.start = nxt_mp_nget(mp, len + 1);
        if (nxt_slow_path(domain.start == NULL)) {
            return NXT_ERROR;
        }

        domain.length = X509_NAME_get_text_by_NID(x509_name, NID_commonName,
                                                  (char *) domain.start,
                                                  len + 1);
        nxt_memcpy_lowcase(domain.start, domain.start, domain.length);

        item = nxt_mp_get(mp, sizeof(nxt_tls_bundle_hash_item_t));
        if (nxt_slow_path(item == NULL)) {
            return NXT_ERROR;
        }

        item->name = domain;
        item->bundle = bundle;

        if (nxt_openssl_bundle_hash_insert(task, &conf->bundle_hash, item,
                                           mp)
            == NXT_ERROR)
        {
            return NXT_ERROR;
        }
    }

    return NXT_OK;

fail:

    sk_GENERAL_NAME_pop_free(alt_names, GENERAL_NAME_free);

    return NXT_ERROR;
}


static const nxt_lvlhsh_proto_t  nxt_openssl_bundle_hash_proto
    nxt_aligned(64) =
{
    NXT_LVLHSH_DEFAULT,
    nxt_openssl_bundle_hash_test,
    nxt_mp_lvlhsh_alloc,
    nxt_mp_lvlhsh_free,
};


static nxt_int_t
nxt_openssl_bundle_hash_test(nxt_lvlhsh_query_t *lhq, void *data)
{
    nxt_tls_bundle_hash_item_t  *item;

    item = data;

    return nxt_strstr_eq(&lhq->key, &item->name) ? NXT_OK : NXT_DECLINED;
}


static nxt_int_t
nxt_openssl_bundle_hash_insert(nxt_task_t *task, nxt_lvlhsh_t *lvlhsh,
    nxt_tls_bundle_hash_item_t *item, nxt_mp_t *mp)
{
    nxt_str_t                   str;
    nxt_int_t                   ret;
    nxt_lvlhsh_query_t          lhq;
    nxt_tls_bundle_hash_item_t  *old;

    str = item->name;

    if (item->name.start[0] == '*') {
        item->name.start++;
        item->name.length--;

        if (item->name.length == 0 || item->name.start[0] != '.') {
            nxt_log(task, NXT_LOG_WARN, "ignored invalid name \"%V\" "
                    "in certificate \"%V\": missing \".\" "
                    "after wildcard symbol", &str, item->bundle->name);
            return NXT_OK;
        }
    }

    lhq.pool = mp;
    lhq.key = item->name;
    lhq.value = item;
    lhq.proto = &nxt_openssl_bundle_hash_proto;
    lhq.replace = 0;
    lhq.key_hash = nxt_murmur_hash2(item->name.start, item->name.length);

    ret = nxt_lvlhsh_insert(lvlhsh, &lhq);
    if (nxt_fast_path(ret == NXT_OK)) {
        nxt_debug(task, "name \"%V\" for certificate \"%V\" is inserted",
                  &str, item->bundle->name);
        return NXT_OK;
    }

    if (nxt_fast_path(ret == NXT_DECLINED)) {
        old = lhq.value;
        if (old->bundle != item->bundle) {
            nxt_log(task, NXT_LOG_WARN, "ignored duplicate name \"%V\" "
                    "in certificate \"%V\", identical name appears in \"%V\"",
                    &str, old->bundle->name, item->bundle->name);

            old->bundle = item->bundle;
        }

        return NXT_OK;
    }

    return NXT_ERROR;
}


static nxt_int_t
nxt_openssl_servername(SSL *s, int *ad, void *arg)
{
    nxt_str_t              str;
    nxt_uint_t             i;
    nxt_conn_t             *c;
    const char             *servername;
    nxt_tls_conf_t         *conf;
    nxt_openssl_conn_t     *tls;
    nxt_tls_bundle_conf_t  *bundle;

    c = SSL_get_ex_data(s, nxt_openssl_connection_index);

    if (nxt_slow_path(c == NULL)) {
        nxt_thread_log_alert("SSL_get_ex_data() failed");
        return SSL_TLSEXT_ERR_ALERT_FATAL;
    }

    servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
    if (nxt_slow_path(servername == NULL)) {
        nxt_log(c->socket.task, NXT_LOG_ALERT, "SSL_get_servername() returned "
                                               "NULL in server name callback");
        return SSL_TLSEXT_ERR_ALERT_FATAL;
    }

    str.length = nxt_strlen(servername);
    if (str.length == 0) {
        nxt_debug(c->socket.task, "client sent zero-length server name");
        goto done;
    }

    if (servername[0] == '.') {
        nxt_debug(c->socket.task, "ignored the server name \"%s\": "
                                  "leading \".\"", servername);
        goto done;
    }

    nxt_debug(c->socket.task, "tls with servername \"%s\"", servername);

    str.start = nxt_mp_nget(c->mem_pool, str.length);
    if (nxt_slow_path(str.start == NULL)) {
        return SSL_TLSEXT_ERR_ALERT_FATAL;
    }

    nxt_memcpy_lowcase(str.start, (const u_char *) servername, str.length);

    tls = c->u.tls;
    conf = tls->conf;

    bundle = nxt_openssl_find_ctx(conf, &str);

    if (bundle == NULL) {
        for (i = 1; i < str.length; i++) {
            if (str.start[i] == '.') {
                str.start += i;
                str.length -= i;

                bundle = nxt_openssl_find_ctx(conf, &str);
                break;
            }
        }
    }

    if (bundle != NULL) {
        nxt_debug(c->socket.task, "new tls context found for \"%V\": \"%V\" "
                                  "(old: \"%V\")", &str, bundle->name,
                                  conf->bundle->name);

        if (bundle != conf->bundle) {
            if (SSL_set_SSL_CTX(s, bundle->ctx) == NULL) {
                nxt_openssl_log_error(c->socket.task, NXT_LOG_ALERT,
                                      "SSL_set_SSL_CTX() failed");

                return SSL_TLSEXT_ERR_ALERT_FATAL;
            }
        }
    }

done:

    return SSL_TLSEXT_ERR_OK;
}


static nxt_tls_bundle_conf_t *
nxt_openssl_find_ctx(nxt_tls_conf_t *conf, nxt_str_t *sn)
{
    nxt_int_t                   ret;
    nxt_lvlhsh_query_t          lhq;
    nxt_tls_bundle_hash_item_t  *item;

    lhq.key_hash = nxt_murmur_hash2(sn->start, sn->length);
    lhq.key = *sn;
    lhq.proto = &nxt_openssl_bundle_hash_proto;

    ret = nxt_lvlhsh_find(&conf->bundle_hash, &lhq);
    if (ret != NXT_OK) {
        return NULL;
    }

    item = lhq.value;

    return item->bundle;
}


static void
nxt_openssl_server_free(nxt_task_t *task, nxt_tls_conf_t *conf)
{
    nxt_tls_bundle_conf_t  *bundle;

    bundle = conf->bundle;
    nxt_assert(bundle != NULL);

    do {
        SSL_CTX_free(bundle->ctx);
        bundle = bundle->next;
    } while (bundle != NULL);

#if (OPENSSL_VERSION_NUMBER >= 0x1010100fL \
     && OPENSSL_VERSION_NUMBER < 0x1010101fL)
    RAND_keep_random_devices_open(0);
#endif
}


static void
nxt_openssl_conn_init(nxt_task_t *task, nxt_tls_conf_t *conf, nxt_conn_t *c)
{
    int                 ret;
    SSL                 *s;
    SSL_CTX             *ctx;
    nxt_openssl_conn_t  *tls;

    nxt_log_debug(c->socket.log, "openssl conn init");

    tls = nxt_mp_zget(c->mem_pool, sizeof(nxt_openssl_conn_t));
    if (tls == NULL) {
        goto fail;
    }

    c->u.tls = tls;
    nxt_buf_mem_set_size(&tls->buffer, conf->buffer_size);

    ctx = conf->bundle->ctx;

    s = SSL_new(ctx);
    if (s == NULL) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT, "SSL_new() failed");
        goto fail;
    }

    tls->session = s;
    /* To pass TLS config to the nxt_openssl_servername() callback. */
    tls->conf = conf;
    tls->conn = c;

    ret = SSL_set_fd(s, c->socket.fd);

    if (ret == 0) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT, "SSL_set_fd(%d) failed",
                              c->socket.fd);
        goto fail;
    }

    SSL_set_accept_state(s);

    if (SSL_set_ex_data(s, nxt_openssl_connection_index, c) == 0) {
        nxt_openssl_log_error(task, NXT_LOG_ALERT, "SSL_set_ex_data() failed");
        goto fail;
    }

    c->io = &nxt_openssl_conn_io;
    c->sendfile = NXT_CONN_SENDFILE_OFF;

    nxt_openssl_conn_handshake(task, c, c->socket.data);
    /*
     * TLS configuration might be destroyed after the TLS connection
     * is established.
     */
    tls->conf = NULL;
    return;

fail:

    nxt_work_queue_add(c->read_work_queue, c->read_state->error_handler,
                       task, c, c->socket.data);
}


nxt_inline void
nxt_openssl_conn_free(nxt_task_t *task, nxt_conn_t *c)
{
    nxt_openssl_conn_t  *tls;

    nxt_debug(task, "openssl conn free");

    tls = c->u.tls;

    if (tls != NULL) {
        c->u.tls = NULL;
        nxt_free(tls->buffer.start);
        SSL_free(tls->session);
    }
}


static void
nxt_openssl_conn_handshake(nxt_task_t *task, void *obj, void *data)
{
    int                     ret;
    nxt_int_t               n;
    nxt_err_t               err;
    nxt_conn_t              *c;
    nxt_work_queue_t        *wq;
    nxt_work_handler_t      handler;
    nxt_openssl_conn_t      *tls;
    const nxt_conn_state_t  *state;

    c = obj;

    nxt_debug(task, "openssl conn handshake fd:%d", c->socket.fd);

    if (c->socket.error != 0) {
        return;
    }

    tls = c->u.tls;

    if (tls == NULL) {
        return;
    }

    nxt_debug(task, "openssl conn handshake: %d times", tls->times);

    /* "tls->times == 1" is suitable to run SSL_do_handshake() in job. */

    ret = SSL_do_handshake(tls->session);

    err = (ret <= 0) ? nxt_socket_errno : 0;

    nxt_thread_time_debug_update(task->thread);

    nxt_debug(task, "SSL_do_handshake(%d): %d err:%d", c->socket.fd, ret, err);

    state = (c->read_state != NULL) ? c->read_state : c->write_state;

    if (ret > 0) {
        /* ret == 1, the handshake was successfully completed. */
        tls->handshake = 1;

        if (c->read_state != NULL) {
            if (state->io_read_handler != NULL || c->read != NULL) {
                nxt_conn_read(task->thread->engine, c);
                return;
            }

        } else {
            if (c->write != NULL) {
                nxt_conn_write(task->thread->engine, c);
                return;
            }
        }

        handler = state->ready_handler;

    } else {
        c->socket.read_handler = nxt_openssl_conn_handshake;
        c->socket.write_handler = nxt_openssl_conn_handshake;

        n = nxt_openssl_conn_test_error(task, c, ret, err,
                                        NXT_OPENSSL_HANDSHAKE);
        switch (n) {

        case NXT_AGAIN:
            if (tls->ssl_error == SSL_ERROR_WANT_READ && tls->times < 2) {
                tls->times++;
            }

            return;

        case 0:
            handler = state->close_handler;
            break;

        default:
        case NXT_ERROR:
            nxt_openssl_conn_error(task, err, "SSL_do_handshake(%d) failed",
                                   c->socket.fd);

            handler = state->error_handler;