Adding upstream version 5:7.2.4.upstream/5%7.2.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1204 insertions, 0 deletions

diff --git a/src/tls.c b/src/tls.c
new file mode 100644
index 0000000..e709c99
--- /dev/null
+++ b/src/tls.c
@@ -0,0 +1,1204 @@
+/*
+ * Copyright (c) 2019, Redis Labs
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *   * Neither the name of Redis nor the names of its contributors may be used
+ *     to endorse or promote products derived from this software without
+ *     specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define REDISMODULE_CORE_MODULE /* A module that's part of the redis core, uses server.h too. */
+
+#include "server.h"
+#include "connhelpers.h"
+#include "adlist.h"
+
+#if (USE_OPENSSL == 1 /* BUILD_YES */ ) || ((USE_OPENSSL == 2 /* BUILD_MODULE */) && (BUILD_TLS_MODULE == 2))
+
+#include <openssl/conf.h>
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+#include <openssl/rand.h>
+#include <openssl/pem.h>
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L
+#include <openssl/decoder.h>
+#endif
+#include <sys/uio.h>
+#include <arpa/inet.h>
+
+#define REDIS_TLS_PROTO_TLSv1       (1<<0)
+#define REDIS_TLS_PROTO_TLSv1_1     (1<<1)
+#define REDIS_TLS_PROTO_TLSv1_2     (1<<2)
+#define REDIS_TLS_PROTO_TLSv1_3     (1<<3)
+
+/* Use safe defaults */
+#ifdef TLS1_3_VERSION
+#define REDIS_TLS_PROTO_DEFAULT     (REDIS_TLS_PROTO_TLSv1_2|REDIS_TLS_PROTO_TLSv1_3)
+#else
+#define REDIS_TLS_PROTO_DEFAULT     (REDIS_TLS_PROTO_TLSv1_2)
+#endif
+
+SSL_CTX *redis_tls_ctx = NULL;
+SSL_CTX *redis_tls_client_ctx = NULL;
+
+static int parseProtocolsConfig(const char *str) {
+    int i, count = 0;
+    int protocols = 0;
+
+    if (!str) return REDIS_TLS_PROTO_DEFAULT;
+    sds *tokens = sdssplitlen(str, strlen(str), " ", 1, &count);
+
+    if (!tokens) { 
+        serverLog(LL_WARNING, "Invalid tls-protocols configuration string");
+        return -1;
+    }
+    for (i = 0; i < count; i++) {
+        if (!strcasecmp(tokens[i], "tlsv1")) protocols |= REDIS_TLS_PROTO_TLSv1;
+        else if (!strcasecmp(tokens[i], "tlsv1.1")) protocols |= REDIS_TLS_PROTO_TLSv1_1;
+        else if (!strcasecmp(tokens[i], "tlsv1.2")) protocols |= REDIS_TLS_PROTO_TLSv1_2;
+        else if (!strcasecmp(tokens[i], "tlsv1.3")) {
+#ifdef TLS1_3_VERSION
+            protocols |= REDIS_TLS_PROTO_TLSv1_3;
+#else
+            serverLog(LL_WARNING, "TLSv1.3 is specified in tls-protocols but not supported by OpenSSL.");
+            protocols = -1;
+            break;
+#endif
+        } else {
+            serverLog(LL_WARNING, "Invalid tls-protocols specified. "
+                    "Use a combination of 'TLSv1', 'TLSv1.1', 'TLSv1.2' and 'TLSv1.3'.");
+            protocols = -1;
+            break;
+        }
+    }
+    sdsfreesplitres(tokens, count);
+
+    return protocols;
+}
+
+/* list of connections with pending data already read from the socket, but not
+ * served to the reader yet. */
+static list *pending_list = NULL;
+
+/**
+ * OpenSSL global initialization and locking handling callbacks.
+ * Note that this is only required for OpenSSL < 1.1.0.
+ */
+
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#define USE_CRYPTO_LOCKS
+#endif
+
+#ifdef USE_CRYPTO_LOCKS
+
+static pthread_mutex_t *openssl_locks;
+
+static void sslLockingCallback(int mode, int lock_id, const char *f, int line) {
+    pthread_mutex_t *mt = openssl_locks + lock_id;
+
+    if (mode & CRYPTO_LOCK) {
+        pthread_mutex_lock(mt);
+    } else {
+        pthread_mutex_unlock(mt);
+    }
+
+    (void)f;
+    (void)line;
+}
+
+static void initCryptoLocks(void) {
+    unsigned i, nlocks;
+    if (CRYPTO_get_locking_callback() != NULL) {
+        /* Someone already set the callback before us. Don't destroy it! */
+        return;
+    }
+    nlocks = CRYPTO_num_locks();
+    openssl_locks = zmalloc(sizeof(*openssl_locks) * nlocks);
+    for (i = 0; i < nlocks; i++) {
+        pthread_mutex_init(openssl_locks + i, NULL);
+    }
+    CRYPTO_set_locking_callback(sslLockingCallback);
+}
+#endif /* USE_CRYPTO_LOCKS */
+
+static void tlsInit(void) {
+    /* Enable configuring OpenSSL using the standard openssl.cnf
+     * OPENSSL_config()/OPENSSL_init_crypto() should be the first 
+     * call to the OpenSSL* library.
+     *  - OPENSSL_config() should be used for OpenSSL versions < 1.1.0
+     *  - OPENSSL_init_crypto() should be used for OpenSSL versions >= 1.1.0
+     */
+    #if OPENSSL_VERSION_NUMBER < 0x10100000L
+    OPENSSL_config(NULL);
+    SSL_load_error_strings();
+    SSL_library_init();
+    #elif OPENSSL_VERSION_NUMBER < 0x10101000L
+    OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CONFIG, NULL);
+    #else
+    OPENSSL_init_crypto(OPENSSL_INIT_LOAD_CONFIG|OPENSSL_INIT_ATFORK, NULL);
+    #endif
+
+#ifdef USE_CRYPTO_LOCKS
+    initCryptoLocks();
+#endif
+
+    if (!RAND_poll()) {
+        serverLog(LL_WARNING, "OpenSSL: Failed to seed random number generator.");
+    }
+
+    pending_list = listCreate();
+}
+
+static void tlsCleanup(void) {
+    if (redis_tls_ctx) {
+        SSL_CTX_free(redis_tls_ctx);
+        redis_tls_ctx = NULL;
+    }
+    if (redis_tls_client_ctx) {
+        SSL_CTX_free(redis_tls_client_ctx);
+        redis_tls_client_ctx = NULL;
+    }
+
+    #if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
+    // unavailable on LibreSSL
+    OPENSSL_cleanup();
+    #endif
+}
+
+/* Callback for passing a keyfile password stored as an sds to OpenSSL */
+static int tlsPasswordCallback(char *buf, int size, int rwflag, void *u) {
+    UNUSED(rwflag);
+
+    const char *pass = u;
+    size_t pass_len;
+
+    if (!pass) return -1;
+    pass_len = strlen(pass);
+    if (pass_len > (size_t) size) return -1;
+    memcpy(buf, pass, pass_len);
+
+    return (int) pass_len;
+}
+
+/* Create a *base* SSL_CTX using the SSL configuration provided. The base context
+ * includes everything that's common for both client-side and server-side connections.
+ */
+static SSL_CTX *createSSLContext(redisTLSContextConfig *ctx_config, int protocols, int client) {
+    const char *cert_file = client ? ctx_config->client_cert_file : ctx_config->cert_file;
+    const char *key_file = client ? ctx_config->client_key_file : ctx_config->key_file;
+    const char *key_file_pass = client ? ctx_config->client_key_file_pass : ctx_config->key_file_pass;
+    char errbuf[256];
+    SSL_CTX *ctx = NULL;
+
+    ctx = SSL_CTX_new(SSLv23_method());
+
+    SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3);
+
+#ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
+    SSL_CTX_set_options(ctx, SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS);
+#endif
+
+    if (!(protocols & REDIS_TLS_PROTO_TLSv1))
+        SSL_CTX_set_options(ctx, SSL_OP_NO_TLSv1);
+    if (!(protocols & REDIS_TLS_PROTO_TLSv1_1))
+        SSL_CTX_set_options(ctx, SSL_OP_NO_TLSv1_1);
+#ifdef SSL_OP_NO_TLSv1_2
+    if (!(protocols & REDIS_TLS_PROTO_TLSv1_2))
+        SSL_CTX_set_options(ctx, SSL_OP_NO_TLSv1_2);
+#endif
+#ifdef SSL_OP_NO_TLSv1_3
+    if (!(protocols & REDIS_TLS_PROTO_TLSv1_3))
+        SSL_CTX_set_options(ctx, SSL_OP_NO_TLSv1_3);
+#endif
+
+#ifdef SSL_OP_NO_COMPRESSION
+    SSL_CTX_set_options(ctx, SSL_OP_NO_COMPRESSION);
+#endif
+
+    SSL_CTX_set_mode(ctx, SSL_MODE_ENABLE_PARTIAL_WRITE|SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
+    SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER|SSL_VERIFY_FAIL_IF_NO_PEER_CERT, NULL);
+
+    SSL_CTX_set_default_passwd_cb(ctx, tlsPasswordCallback);
+    SSL_CTX_set_default_passwd_cb_userdata(ctx, (void *) key_file_pass);
+
+    if (SSL_CTX_use_certificate_chain_file(ctx, cert_file) <= 0) {
+        ERR_error_string_n(ERR_get_error(), errbuf, sizeof(errbuf));
+        serverLog(LL_WARNING, "Failed to load certificate: %s: %s", cert_file, errbuf);
+        goto error;
+    }
+
+    if (SSL_CTX_use_PrivateKey_file(ctx, key_file, SSL_FILETYPE_PEM) <= 0) {
+        ERR_error_string_n(ERR_get_error(), errbuf, sizeof(errbuf));
+        serverLog(LL_WARNING, "Failed to load private key: %s: %s", key_file, errbuf);
+        goto error;
+    }
+
+    if ((ctx_config->ca_cert_file || ctx_config->ca_cert_dir) &&
+        SSL_CTX_load_verify_locations(ctx, ctx_config->ca_cert_file, ctx_config->ca_cert_dir) <= 0) {
+        ERR_error_string_n(ERR_get_error(), errbuf, sizeof(errbuf));
+        serverLog(LL_WARNING, "Failed to configure CA certificate(s) file/directory: %s", errbuf);
+        goto error;
+    }
+
+    if (ctx_config->ciphers && !SSL_CTX_set_cipher_list(ctx, ctx_config->ciphers)) {
+        serverLog(LL_WARNING, "Failed to configure ciphers: %s", ctx_config->ciphers);
+        goto error;
+    }
+
+#ifdef TLS1_3_VERSION
+    if (ctx_config->ciphersuites && !SSL_CTX_set_ciphersuites(ctx, ctx_config->ciphersuites)) {
+        serverLog(LL_WARNING, "Failed to configure ciphersuites: %s", ctx_config->ciphersuites);
+        goto error;
+    }
+#endif
+
+    return ctx;
+
+error:
+    if (ctx) SSL_CTX_free(ctx);
+    return NULL;
+}
+
+/* Attempt to configure/reconfigure TLS. This operation is atomic and will
+ * leave the SSL_CTX unchanged if fails.
+ * @priv: config of redisTLSContextConfig.
+ * @reconfigure: if true, ignore the previous configure; if false, only
+ *               configure from @ctx_config if redis_tls_ctx is NULL.
+ */
+static int tlsConfigure(void *priv, int reconfigure) {
+    redisTLSContextConfig *ctx_config = (redisTLSContextConfig *)priv;
+    char errbuf[256];
+    SSL_CTX *ctx = NULL;
+    SSL_CTX *client_ctx = NULL;
+
+    if (!reconfigure && redis_tls_ctx) {
+        return C_OK;
+    }
+
+    if (!ctx_config->cert_file) {
+        serverLog(LL_WARNING, "No tls-cert-file configured!");
+        goto error;
+    }
+
+    if (!ctx_config->key_file) {
+        serverLog(LL_WARNING, "No tls-key-file configured!");
+        goto error;
+    }
+
+    if (((server.tls_auth_clients != TLS_CLIENT_AUTH_NO) || server.tls_cluster || server.tls_replication) &&
+            !ctx_config->ca_cert_file && !ctx_config->ca_cert_dir) {
+        serverLog(LL_WARNING, "Either tls-ca-cert-file or tls-ca-cert-dir must be specified when tls-cluster, tls-replication or tls-auth-clients are enabled!");
+        goto error;
+    }
+
+    int protocols = parseProtocolsConfig(ctx_config->protocols);
+    if (protocols == -1) goto error;
+
+    /* Create server side/general context */
+    ctx = createSSLContext(ctx_config, protocols, 0);
+    if (!ctx) goto error;
+
+    if (ctx_config->session_caching) {
+        SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_SERVER);
+        SSL_CTX_sess_set_cache_size(ctx, ctx_config->session_cache_size);
+        SSL_CTX_set_timeout(ctx, ctx_config->session_cache_timeout);
+        SSL_CTX_set_session_id_context(ctx, (void *) "redis", 5);
+    } else {
+        SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF);
+    }
+
+#ifdef SSL_OP_NO_CLIENT_RENEGOTIATION
+    SSL_CTX_set_options(ctx, SSL_OP_NO_CLIENT_RENEGOTIATION);
+#endif
+
+    if (ctx_config->prefer_server_ciphers)
+        SSL_CTX_set_options(ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
+
+#if ((OPENSSL_VERSION_NUMBER < 0x30000000L) && defined(SSL_CTX_set_ecdh_auto))
+    SSL_CTX_set_ecdh_auto(ctx, 1);
+#endif
+    SSL_CTX_set_options(ctx, SSL_OP_SINGLE_DH_USE);
+
+    if (ctx_config->dh_params_file) {
+        FILE *dhfile = fopen(ctx_config->dh_params_file, "r");
+        if (!dhfile) {
+            serverLog(LL_WARNING, "Failed to load %s: %s", ctx_config->dh_params_file, strerror(errno));
+            goto error;
+        }
+
+#if (OPENSSL_VERSION_NUMBER >= 0x30000000L)
+        EVP_PKEY *pkey = NULL;
+        OSSL_DECODER_CTX *dctx = OSSL_DECODER_CTX_new_for_pkey(
+                &pkey, "PEM", NULL, "DH", OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS, NULL, NULL);
+        if (!dctx) {
+            serverLog(LL_WARNING, "No decoder for DH params.");
+            fclose(dhfile);
+            goto error;
+        }
+        if (!OSSL_DECODER_from_fp(dctx, dhfile)) {
+            serverLog(LL_WARNING, "%s: failed to read DH params.", ctx_config->dh_params_file);
+            OSSL_DECODER_CTX_free(dctx);
+            fclose(dhfile);
+            goto error;
+        }
+
+        OSSL_DECODER_CTX_free(dctx);
+        fclose(dhfile);
+
+        if (SSL_CTX_set0_tmp_dh_pkey(ctx, pkey) <= 0) {
+            ERR_error_string_n(ERR_get_error(), errbuf, sizeof(errbuf));
+            serverLog(LL_WARNING, "Failed to load DH params file: %s: %s", ctx_config->dh_params_file, errbuf);
+            EVP_PKEY_free(pkey);
+            goto error;
+        }
+        /* Not freeing pkey, it is owned by OpenSSL now */
+#else
+        DH *dh = PEM_read_DHparams(dhfile, NULL, NULL, NULL);
+        fclose(dhfile);
+        if (!dh) {
+            serverLog(LL_WARNING, "%s: failed to read DH params.", ctx_config->dh_params_file);
+            goto error;
+        }
+
+        if (SSL_CTX_set_tmp_dh(ctx, dh) <= 0) {
+            ERR_error_string_n(ERR_get_error(), errbuf, sizeof(errbuf));
+            serverLog(LL_WARNING, "Failed to load DH params file: %s: %s", ctx_config->dh_params_file, errbuf);
+            DH_free(dh);
+            goto error;
+        }
+
+        DH_free(dh);
+#endif
+    } else {
+#if (OPENSSL_VERSION_NUMBER >= 0x30000000L)
+        SSL_CTX_set_dh_auto(ctx, 1);
+#endif
+    }
+
+    /* If a client-side certificate is configured, create an explicit client context */
+    if (ctx_config->client_cert_file && ctx_config->client_key_file) {
+        client_ctx = createSSLContext(ctx_config, protocols, 1);
+        if (!client_ctx) goto error;
+    }
+
+    SSL_CTX_free(redis_tls_ctx);
+    SSL_CTX_free(redis_tls_client_ctx);
+    redis_tls_ctx = ctx;
+    redis_tls_client_ctx = client_ctx;
+
+    return C_OK;
+
+error:
+    if (ctx) SSL_CTX_free(ctx);
+    if (client_ctx) SSL_CTX_free(client_ctx);
+    return C_ERR;
+}
+
+#ifdef TLS_DEBUGGING
+#define TLSCONN_DEBUG(fmt, ...) \
+    serverLog(LL_DEBUG, "TLSCONN: " fmt, __VA_ARGS__)
+#else
+#define TLSCONN_DEBUG(fmt, ...)
+#endif
+
+static ConnectionType CT_TLS;
+
+/* Normal socket connections have a simple events/handler correlation.
+ *
+ * With TLS connections we need to handle cases where during a logical read
+ * or write operation, the SSL library asks to block for the opposite
+ * socket operation.
+ *
+ * When this happens, we need to do two things:
+ * 1. Make sure we register for the event.
+ * 2. Make sure we know which handler needs to execute when the
+ *    event fires.  That is, if we notify the caller of a write operation
+ *    that it blocks, and SSL asks for a read, we need to trigger the
+ *    write handler again on the next read event.
+ *
+ */
+
+typedef enum {
+    WANT_READ = 1,
+    WANT_WRITE
+} WantIOType;
+
+#define TLS_CONN_FLAG_READ_WANT_WRITE   (1<<0)
+#define TLS_CONN_FLAG_WRITE_WANT_READ   (1<<1)
+#define TLS_CONN_FLAG_FD_SET            (1<<2)
+
+typedef struct tls_connection {
+    connection c;
+    int flags;
+    SSL *ssl;
+    char *ssl_error;
+    listNode *pending_list_node;
+} tls_connection;
+
+static connection *createTLSConnection(int client_side) {
+    SSL_CTX *ctx = redis_tls_ctx;
+    if (client_side && redis_tls_client_ctx)
+        ctx = redis_tls_client_ctx;
+    tls_connection *conn = zcalloc(sizeof(tls_connection));
+    conn->c.type = &CT_TLS;
+    conn->c.fd = -1;
+    conn->c.iovcnt = IOV_MAX;
+    conn->ssl = SSL_new(ctx);
+    return (connection *) conn;
+}
+
+static connection *connCreateTLS(void) {
+    return createTLSConnection(1);
+}
+
+/* Fetch the latest OpenSSL error and store it in the connection */
+static void updateTLSError(tls_connection *conn) {
+    conn->c.last_errno = 0;
+    if (conn->ssl_error) zfree(conn->ssl_error);
+    conn->ssl_error = zmalloc(512);
+    ERR_error_string_n(ERR_get_error(), conn->ssl_error, 512);
+}
+
+/* Create a new TLS connection that is already associated with
+ * an accepted underlying file descriptor.
+ *
+ * The socket is not ready for I/O until connAccept() was called and
+ * invoked the connection-level accept handler.
+ *
+ * Callers should use connGetState() and verify the created connection
+ * is not in an error state.
+ */
+static connection *connCreateAcceptedTLS(int fd, void *priv) {
+    int require_auth = *(int *)priv;
+    tls_connection *conn = (tls_connection *) createTLSConnection(0);
+    conn->c.fd = fd;
+    conn->c.state = CONN_STATE_ACCEPTING;
+
+    if (!conn->ssl) {
+        updateTLSError(conn);
+        conn->c.state = CONN_STATE_ERROR;
+        return (connection *) conn;
+    }
+
+    switch (require_auth) {
+        case TLS_CLIENT_AUTH_NO:
+            SSL_set_verify(conn->ssl, SSL_VERIFY_NONE, NULL);
+            break;
+        case TLS_CLIENT_AUTH_OPTIONAL:
+            SSL_set_verify(conn->ssl, SSL_VERIFY_PEER, NULL);
+            break;
+        default: /* TLS_CLIENT_AUTH_YES, also fall-secure */
+            SSL_set_verify(conn->ssl, SSL_VERIFY_PEER|SSL_VERIFY_FAIL_IF_NO_PEER_CERT, NULL);
+            break;
+    }
+
+    SSL_set_fd(conn->ssl, conn->c.fd);
+    SSL_set_accept_state(conn->ssl);
+
+    return (connection *) conn;
+}
+
+static void tlsEventHandler(struct aeEventLoop *el, int fd, void *clientData, int mask);
+static void updateSSLEvent(tls_connection *conn);
+
+/* Process the return code received from OpenSSL>
+ * Update the want parameter with expected I/O.
+ * Update the connection's error state if a real error has occurred.
+ * Returns an SSL error code, or 0 if no further handling is required.
+ */
+static int handleSSLReturnCode(tls_connection *conn, int ret_value, WantIOType *want) {
+    if (ret_value <= 0) {
+        int ssl_err = SSL_get_error(conn->ssl, ret_value);
+        switch (ssl_err) {
+            case SSL_ERROR_WANT_WRITE:
+                *want = WANT_WRITE;
+                return 0;
+            case SSL_ERROR_WANT_READ:
+                *want = WANT_READ;
+                return 0;
+            case SSL_ERROR_SYSCALL:
+                conn->c.last_errno = errno;
+                if (conn->ssl_error) zfree(conn->ssl_error);
+                conn->ssl_error = errno ? zstrdup(strerror(errno)) : NULL;
+                break;
+            default:
+                /* Error! */
+                updateTLSError(conn);
+                break;
+        }
+
+        return ssl_err;
+    }
+
+    return 0;
+}
+
+/* Handle OpenSSL return code following SSL_write() or SSL_read():
+ *
+ * - Updates conn state and last_errno.
+ * - If update_event is nonzero, calls updateSSLEvent() when necessary.
+ *
+ * Returns ret_value, or -1 on error or dropped connection.
+ */
+static int updateStateAfterSSLIO(tls_connection *conn, int ret_value, int update_event) {
+    /* If system call was interrupted, there's no need to go through the full
+     * OpenSSL error handling and just report this for the caller to retry the
+     * operation.
+     */
+    if (errno == EINTR) {
+        conn->c.last_errno = EINTR;
+        return -1;
+    }
+
+    if (ret_value <= 0) {
+        WantIOType want = 0;
+        int ssl_err;
+        if (!(ssl_err = handleSSLReturnCode(conn, ret_value, &want))) {
+            if (want == WANT_READ) conn->flags |= TLS_CONN_FLAG_WRITE_WANT_READ;
+            if (want == WANT_WRITE) conn->flags |= TLS_CONN_FLAG_READ_WANT_WRITE;
+            if (update_event) updateSSLEvent(conn);
+            errno = EAGAIN;
+            return -1;
+        } else {
+            if (ssl_err == SSL_ERROR_ZERO_RETURN ||
+                ((ssl_err == SSL_ERROR_SYSCALL && !errno))) {
+                conn->c.state = CONN_STATE_CLOSED;
+                return -1;
+            } else {
+                conn->c.state = CONN_STATE_ERROR;
+                return -1;
+            }
+        }
+    }
+
+    return ret_value;
+}
+
+static void registerSSLEvent(tls_connection *conn, WantIOType want) {
+    int mask = aeGetFileEvents(server.el, conn->c.fd);
+
+    switch (want) {
+        case WANT_READ:
+            if (mask & AE_WRITABLE) aeDeleteFileEvent(server.el, conn->c.fd, AE_WRITABLE);
+            if (!(mask & AE_READABLE)) aeCreateFileEvent(server.el, conn->c.fd, AE_READABLE,
+                        tlsEventHandler, conn);
+            break;
+        case WANT_WRITE:
+            if (mask & AE_READABLE) aeDeleteFileEvent(server.el, conn->c.fd, AE_READABLE);
+            if (!(mask & AE_WRITABLE)) aeCreateFileEvent(server.el, conn->c.fd, AE_WRITABLE,
+                        tlsEventHandler, conn);
+            break;
+        default:
+            serverAssert(0);
+            break;
+    }
+}
+
+static void updateSSLEvent(tls_connection *conn) {
+    int mask = aeGetFileEvents(server.el, conn->c.fd);
+    int need_read = conn->c.read_handler || (conn->flags & TLS_CONN_FLAG_WRITE_WANT_READ);
+    int need_write = conn->c.write_handler || (conn->flags & TLS_CONN_FLAG_READ_WANT_WRITE);
+
+    if (need_read && !(mask & AE_READABLE))
+        aeCreateFileEvent(server.el, conn->c.fd, AE_READABLE, tlsEventHandler, conn);
+    if (!need_read && (mask & AE_READABLE))
+        aeDeleteFileEvent(server.el, conn->c.fd, AE_READABLE);
+
+    if (need_write && !(mask & AE_WRITABLE))
+        aeCreateFileEvent(server.el, conn->c.fd, AE_WRITABLE, tlsEventHandler, conn);
+    if (!need_write && (mask & AE_WRITABLE))
+        aeDeleteFileEvent(server.el, conn->c.fd, AE_WRITABLE);
+}
+
+static void tlsHandleEvent(tls_connection *conn, int mask) {
+    int ret, conn_error;
+
+    TLSCONN_DEBUG("tlsEventHandler(): fd=%d, state=%d, mask=%d, r=%d, w=%d, flags=%d",
+            fd, conn->c.state, mask, conn->c.read_handler != NULL, conn->c.write_handler != NULL,
+            conn->flags);
+
+    ERR_clear_error();
+
+    switch (conn->c.state) {
+        case CONN_STATE_CONNECTING:
+            conn_error = anetGetError(conn->c.fd);
+            if (conn_error) {
+                conn->c.last_errno = conn_error;
+                conn->c.state = CONN_STATE_ERROR;
+            } else {
+                if (!(conn->flags & TLS_CONN_FLAG_FD_SET)) {
+                    SSL_set_fd(conn->ssl, conn->c.fd);
+                    conn->flags |= TLS_CONN_FLAG_FD_SET;
+                }
+                ret = SSL_connect(conn->ssl);
+                if (ret <= 0) {
+                    WantIOType want = 0;
+                    if (!handleSSLReturnCode(conn, ret, &want)) {
+                        registerSSLEvent(conn, want);
+
+                        /* Avoid hitting UpdateSSLEvent, which knows nothing
+                         * of what SSL_connect() wants and instead looks at our
+                         * R/W handlers.
+                         */
+                        return;
+                    }
+
+                    /* If not handled, it's an error */
+                    conn->c.state = CONN_STATE_ERROR;
+                } else {
+                    conn->c.state = CONN_STATE_CONNECTED;
+                }
+            }
+
+            if (!callHandler((connection *) conn, conn->c.conn_handler)) return;
+            conn->c.conn_handler = NULL;
+            break;
+        case CONN_STATE_ACCEPTING:
+            ret = SSL_accept(conn->ssl);
+            if (ret <= 0) {
+                WantIOType want = 0;
+                if (!handleSSLReturnCode(conn, ret, &want)) {
+                    /* Avoid hitting UpdateSSLEvent, which knows nothing
+                     * of what SSL_connect() wants and instead looks at our
+                     * R/W handlers.
+                     */
+                    registerSSLEvent(conn, want);
+                    return;
+                }
+
+                /* If not handled, it's an error */
+                conn->c.state = CONN_STATE_ERROR;
+            } else {
+                conn->c.state = CONN_STATE_CONNECTED;
+            }
+
+            if (!callHandler((connection *) conn, conn->c.conn_handler)) return;
+            conn->c.conn_handler = NULL;
+            break;
+        case CONN_STATE_CONNECTED:
+        {
+            int call_read = ((mask & AE_READABLE) && conn->c.read_handler) ||
+                ((mask & AE_WRITABLE) && (conn->flags & TLS_CONN_FLAG_READ_WANT_WRITE));
+            int call_write = ((mask & AE_WRITABLE) && conn->c.write_handler) ||
+                ((mask & AE_READABLE) && (conn->flags & TLS_CONN_FLAG_WRITE_WANT_READ));
+
+            /* Normally we execute the readable event first, and the writable
+             * event laster. This is useful as sometimes we may be able
+             * to serve the reply of a query immediately after processing the
+             * query.
+             *
+             * However if WRITE_BARRIER is set in the mask, our application is
+             * asking us to do the reverse: never fire the writable event
+             * after the readable. In such a case, we invert the calls.
+             * This is useful when, for instance, we want to do things
+             * in the beforeSleep() hook, like fsynching a file to disk,
+             * before replying to a client. */
+            int invert = conn->c.flags & CONN_FLAG_WRITE_BARRIER;
+
+            if (!invert && call_read) {
+                conn->flags &= ~TLS_CONN_FLAG_READ_WANT_WRITE;
+                if (!callHandler((connection *) conn, conn->c.read_handler)) return;
+            }
+
+            /* Fire the writable event. */
+            if (call_write) {
+                conn->flags &= ~TLS_CONN_FLAG_WRITE_WANT_READ;
+                if (!callHandler((connection *) conn, conn->c.write_handler)) return;
+            }
+
+            /* If we have to invert the call, fire the readable event now
+             * after the writable one. */
+            if (invert && call_read) {
+                conn->flags &= ~TLS_CONN_FLAG_READ_WANT_WRITE;
+                if (!callHandler((connection *) conn, conn->c.read_handler)) return;
+            }
+
+            /* If SSL has pending that, already read from the socket, we're at
+             * risk of not calling the read handler again, make sure to add it
+             * to a list of pending connection that should be handled anyway. */
+            if ((mask & AE_READABLE)) {
+                if (SSL_pending(conn->ssl) > 0) {
+                    if (!conn->pending_list_node) {
+                        listAddNodeTail(pending_list, conn);
+                        conn->pending_list_node = listLast(pending_list);
+                    }
+                } else if (conn->pending_list_node) {
+                    listDelNode(pending_list, conn->pending_list_node);
+                    conn->pending_list_node = NULL;
+                }
+            }
+
+            break;
+        }
+        default:
+            break;
+    }
+
+    updateSSLEvent(conn);
+}
+
+static void tlsEventHandler(struct aeEventLoop *el, int fd, void *clientData, int mask) {
+    UNUSED(el);
+    UNUSED(fd);
+    tls_connection *conn = clientData;
+    tlsHandleEvent(conn, mask);
+}
+
+static void tlsAcceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
+    int cport, cfd, max = MAX_ACCEPTS_PER_CALL;
+    char cip[NET_IP_STR_LEN];
+    UNUSED(el);
+    UNUSED(mask);
+    UNUSED(privdata);
+
+    while(max--) {
+        cfd = anetTcpAccept(server.neterr, fd, cip, sizeof(cip), &cport);
+        if (cfd == ANET_ERR) {
+            if (errno != EWOULDBLOCK)
+                serverLog(LL_WARNING,
+                    "Accepting client connection: %s", server.neterr);
+            return;
+        }
+        serverLog(LL_VERBOSE,"Accepted %s:%d", cip, cport);
+        acceptCommonHandler(connCreateAcceptedTLS(cfd, &server.tls_auth_clients),0,cip);
+    }
+}
+
+static int connTLSAddr(connection *conn, char *ip, size_t ip_len, int *port, int remote) {
+    return anetFdToString(conn->fd, ip, ip_len, port, remote);
+}
+
+static int connTLSIsLocal(connection *conn) {
+    return connectionTypeTcp()->is_local(conn);
+}
+
+static int connTLSListen(connListener *listener) {
+    return listenToPort(listener);
+}
+
+static void connTLSShutdown(connection *conn_) {
+    tls_connection *conn = (tls_connection *) conn_;
+
+    if (conn->ssl) {
+        if (conn->c.state == CONN_STATE_CONNECTED)
+            SSL_shutdown(conn->ssl);
+        SSL_free(conn->ssl);
+        conn->ssl = NULL;
+    }
+
+    connectionTypeTcp()->shutdown(conn_);
+}
+
+static void connTLSClose(connection *conn_) {
+    tls_connection *conn = (tls_connection *) conn_;
+
+    if (conn->ssl) {
+        if (conn->c.state == CONN_STATE_CONNECTED)
+            SSL_shutdown(conn->ssl);
+        SSL_free(conn->ssl);
+        conn->ssl = NULL;
+    }
+
+    if (conn->ssl_error) {
+        zfree(conn->ssl_error);
+        conn->ssl_error = NULL;
+    }
+
+    if (conn->pending_list_node) {
+        listDelNode(pending_list, conn->pending_list_node);
+        conn->pending_list_node = NULL;
+    }
+
+    connectionTypeTcp()->close(conn_);
+}
+
+static int connTLSAccept(connection *_conn, ConnectionCallbackFunc accept_handler) {
+    tls_connection *conn = (tls_connection *) _conn;
+    int ret;
+
+    if (conn->c.state != CONN_STATE_ACCEPTING) return C_ERR;
+    ERR_clear_error();
+
+    /* Try to accept */
+    conn->c.conn_handler = accept_handler;
+    ret = SSL_accept(conn->ssl);
+
+    if (ret <= 0) {
+        WantIOType want = 0;
+        if (!handleSSLReturnCode(conn, ret, &want)) {
+            registerSSLEvent(conn, want);   /* We'll fire back */
+            return C_OK;
+        } else {
+            conn->c.state = CONN_STATE_ERROR;
+            return C_ERR;
+        }
+    }
+
+    conn->c.state = CONN_STATE_CONNECTED;
+    if (!callHandler((connection *) conn, conn->c.conn_handler)) return C_OK;
+    conn->c.conn_handler = NULL;
+
+    return C_OK;
+}
+
+static int connTLSConnect(connection *conn_, const char *addr, int port, const char *src_addr, ConnectionCallbackFunc connect_handler) {
+    tls_connection *conn = (tls_connection *) conn_;
+    unsigned char addr_buf[sizeof(struct in6_addr)];
+
+    if (conn->c.state != CONN_STATE_NONE) return C_ERR;
+    ERR_clear_error();
+
+    /* Check whether addr is an IP address, if not, use the value for Server Name Indication */
+    if (inet_pton(AF_INET, addr, addr_buf) != 1 && inet_pton(AF_INET6, addr, addr_buf) != 1) {
+        SSL_set_tlsext_host_name(conn->ssl, addr);
+    }
+
+    /* Initiate Socket connection first */
+    if (connectionTypeTcp()->connect(conn_, addr, port, src_addr, connect_handler) == C_ERR) return C_ERR;
+
+    /* Return now, once the socket is connected we'll initiate
+     * TLS connection from the event handler.
+     */
+    return C_OK;
+}
+
+static int connTLSWrite(connection *conn_, const void *data, size_t data_len) {
+    tls_connection *conn = (tls_connection *) conn_;
+    int ret;
+
+    if (conn->c.state != CONN_STATE_CONNECTED) return -1;
+    ERR_clear_error();
+    ret = SSL_write(conn->ssl, data, data_len);
+    return updateStateAfterSSLIO(conn, ret, 1);
+}
+
+static int connTLSWritev(connection *conn_, const struct iovec *iov, int iovcnt) {
+    if (iovcnt == 1) return connTLSWrite(conn_, iov[0].iov_base, iov[0].iov_len);
+
+    /* Accumulate the amount of bytes of each buffer and check if it exceeds NET_MAX_WRITES_PER_EVENT. */
+    size_t iov_bytes_len = 0;
+    for (int i = 0; i < iovcnt; i++) {
+        iov_bytes_len += iov[i].iov_len;
+        if (iov_bytes_len > NET_MAX_WRITES_PER_EVENT) break;
+    }
+
+    /* The amount of all buffers is greater than NET_MAX_WRITES_PER_EVENT, 
+     * which is not worth doing so much memory copying to reduce system calls,
+     * therefore, invoke connTLSWrite() multiple times to avoid memory copies. */
+    if (iov_bytes_len > NET_MAX_WRITES_PER_EVENT) {
+        ssize_t tot_sent = 0;
+        for (int i = 0; i < iovcnt; i++) {
+            ssize_t sent = connTLSWrite(conn_, iov[i].iov_base, iov[i].iov_len);
+            if (sent <= 0) return tot_sent > 0 ? tot_sent : sent;
+            tot_sent += sent;
+            if ((size_t) sent != iov[i].iov_len) break;
+        }
+        return tot_sent;
+    }
+
+    /* The amount of all buffers is less than NET_MAX_WRITES_PER_EVENT, 
+     * which is worth doing more memory copies in exchange for fewer system calls, 
+     * so concatenate these scattered buffers into a contiguous piece of memory 
+     * and send it away by one call to connTLSWrite(). */
+    char buf[iov_bytes_len];
+    size_t offset = 0;
+    for (int i = 0; i < iovcnt; i++) {
+        memcpy(buf + offset, iov[i].iov_base, iov[i].iov_len);
+        offset += iov[i].iov_len;
+    }
+    return connTLSWrite(conn_, buf, iov_bytes_len);
+}
+
+static int connTLSRead(connection *conn_, void *buf, size_t buf_len) {
+    tls_connection *conn = (tls_connection *) conn_;
+    int ret;
+
+    if (conn->c.state != CONN_STATE_CONNECTED) return -1;
+    ERR_clear_error();
+    ret = SSL_read(conn->ssl, buf, buf_len);
+    return updateStateAfterSSLIO(conn, ret, 1);
+}
+
+static const char *connTLSGetLastError(connection *conn_) {
+    tls_connection *conn = (tls_connection *) conn_;
+
+    if (conn->ssl_error) return conn->ssl_error;
+    return NULL;
+}
+
+static int connTLSSetWriteHandler(connection *conn, ConnectionCallbackFunc func, int barrier) {
+    conn->write_handler = func;
+    if (barrier)
+        conn->flags |= CONN_FLAG_WRITE_BARRIER;
+    else
+        conn->flags &= ~CONN_FLAG_WRITE_BARRIER;
+    updateSSLEvent((tls_connection *) conn);
+    return C_OK;
+}
+
+static int connTLSSetReadHandler(connection *conn, ConnectionCallbackFunc func) {
+    conn->read_handler = func;
+    updateSSLEvent((tls_connection *) conn);
+    return C_OK;
+}
+
+static void setBlockingTimeout(tls_connection *conn, long long timeout) {
+    anetBlock(NULL, conn->c.fd);
+    anetSendTimeout(NULL, conn->c.fd, timeout);
+    anetRecvTimeout(NULL, conn->c.fd, timeout);
+}
+
+static void unsetBlockingTimeout(tls_connection *conn) {
+    anetNonBlock(NULL, conn->c.fd);
+    anetSendTimeout(NULL, conn->c.fd, 0);
+    anetRecvTimeout(NULL, conn->c.fd, 0);
+}
+
+static int connTLSBlockingConnect(connection *conn_, const char *addr, int port, long long timeout) {
+    tls_connection *conn = (tls_connection *) conn_;
+    int ret;
+
+    if (conn->c.state != CONN_STATE_NONE) return C_ERR;
+
+    /* Initiate socket blocking connect first */
+    if (connectionTypeTcp()->blocking_connect(conn_, addr, port, timeout) == C_ERR) return C_ERR;
+
+    /* Initiate TLS connection now.  We set up a send/recv timeout on the socket,
+     * which means the specified timeout will not be enforced accurately. */
+    SSL_set_fd(conn->ssl, conn->c.fd);
+    setBlockingTimeout(conn, timeout);
+
+    if ((ret = SSL_connect(conn->ssl)) <= 0) {
+        conn->c.state = CONN_STATE_ERROR;
+        return C_ERR;
+    }
+    unsetBlockingTimeout(conn);
+
+    conn->c.state = CONN_STATE_CONNECTED;
+    return C_OK;
+}
+
+static ssize_t connTLSSyncWrite(connection *conn_, char *ptr, ssize_t size, long long timeout) {
+    tls_connection *conn = (tls_connection *) conn_;
+
+    setBlockingTimeout(conn, timeout);
+    SSL_clear_mode(conn->ssl, SSL_MODE_ENABLE_PARTIAL_WRITE);
+    ERR_clear_error();
+    int ret = SSL_write(conn->ssl, ptr, size);
+    ret = updateStateAfterSSLIO(conn, ret, 0);
+    SSL_set_mode(conn->ssl, SSL_MODE_ENABLE_PARTIAL_WRITE);
+    unsetBlockingTimeout(conn);
+
+    return ret;
+}
+
+static ssize_t connTLSSyncRead(connection *conn_, char *ptr, ssize_t size, long long timeout) {
+    tls_connection *conn = (tls_connection *) conn_;
+
+    setBlockingTimeout(conn, timeout);
+    ERR_clear_error();
+    int ret = SSL_read(conn->ssl, ptr, size);
+    ret = updateStateAfterSSLIO(conn, ret, 0);
+    unsetBlockingTimeout(conn);
+
+    return ret;
+}
+
+static ssize_t connTLSSyncReadLine(connection *conn_, char *ptr, ssize_t size, long long timeout) {
+    tls_connection *conn = (tls_connection *) conn_;
+    ssize_t nread = 0;
+
+    setBlockingTimeout(conn, timeout);
+
+    size--;
+    while(size) {
+        char c;
+
+        ERR_clear_error();
+        int ret = SSL_read(conn->ssl, &c, 1);
+        ret = updateStateAfterSSLIO(conn, ret, 0);
+        if (ret <= 0) {
+            nread = -1;
+            goto exit;
+        }
+        if (c == '\n') {
+            *ptr = '\0';
+            if (nread && *(ptr-1) == '\r') *(ptr-1) = '\0';
+            goto exit;
+        } else {
+            *ptr++ = c;
+            *ptr = '\0';
+            nread++;
+        }
+        size--;
+    }
+exit:
+    unsetBlockingTimeout(conn);
+    return nread;
+}
+
+static const char *connTLSGetType(connection *conn_) {
+    (void) conn_;
+
+    return CONN_TYPE_TLS;
+}
+
+static int tlsHasPendingData(void) {
+    if (!pending_list)
+        return 0;
+    return listLength(pending_list) > 0;
+}
+
+static int tlsProcessPendingData(void) {
+    listIter li;
+    listNode *ln;
+
+    int processed = listLength(pending_list);
+    listRewind(pending_list,&li);
+    while((ln = listNext(&li))) {
+        tls_connection *conn = listNodeValue(ln);
+        tlsHandleEvent(conn, AE_READABLE);
+    }
+    return processed;
+}
+
+/* Fetch the peer certificate used for authentication on the specified
+ * connection and return it as a PEM-encoded sds.
+ */
+static sds connTLSGetPeerCert(connection *conn_) {
+    tls_connection *conn = (tls_connection *) conn_;
+    if ((conn_->type != connectionTypeTls()) || !conn->ssl) return NULL;
+
+    X509 *cert = SSL_get_peer_certificate(conn->ssl);
+    if (!cert) return NULL;
+
+    BIO *bio = BIO_new(BIO_s_mem());
+    if (bio == NULL || !PEM_write_bio_X509(bio, cert)) {
+        if (bio != NULL) BIO_free(bio);
+        return NULL;
+    }
+
+    const char *bio_ptr;
+    long long bio_len = BIO_get_mem_data(bio, &bio_ptr);
+    sds cert_pem = sdsnewlen(bio_ptr, bio_len);
+    BIO_free(bio);
+
+    return cert_pem;
+}
+
+static ConnectionType CT_TLS = {
+    /* connection type */
+    .get_type = connTLSGetType,
+
+    /* connection type initialize & finalize & configure */
+    .init = tlsInit,
+    .cleanup = tlsCleanup,
+    .configure = tlsConfigure,
+
+    /* ae & accept & listen & error & address handler */
+    .ae_handler = tlsEventHandler,
+    .accept_handler = tlsAcceptHandler,
+    .addr = connTLSAddr,
+    .is_local = connTLSIsLocal,
+    .listen = connTLSListen,
+
+    /* create/shutdown/close connection */
+    .conn_create = connCreateTLS,
+    .conn_create_accepted = connCreateAcceptedTLS,
+    .shutdown = connTLSShutdown,
+    .close = connTLSClose,
+
+    /* connect & accept */
+    .connect = connTLSConnect,
+    .blocking_connect = connTLSBlockingConnect,
+    .accept = connTLSAccept,
+
+    /* IO */
+    .read = connTLSRead,
+    .write = connTLSWrite,
+    .writev = connTLSWritev,
+    .set_write_handler = connTLSSetWriteHandler,
+    .set_read_handler = connTLSSetReadHandler,
+    .get_last_error = connTLSGetLastError,
+    .sync_write = connTLSSyncWrite,
+    .sync_read = connTLSSyncRead,
+    .sync_readline = connTLSSyncReadLine,
+
+    /* pending data */
+    .has_pending_data = tlsHasPendingData,
+    .process_pending_data = tlsProcessPendingData,
+
+    /* TLS specified methods */
+    .get_peer_cert = connTLSGetPeerCert,
+};
+
+int RedisRegisterConnectionTypeTLS(void) {
+    return connTypeRegister(&CT_TLS);
+}
+
+#else   /* USE_OPENSSL */
+
+int RedisRegisterConnectionTypeTLS(void) {
+    serverLog(LL_VERBOSE, "Connection type %s not builtin", CONN_TYPE_TLS);
+    return C_ERR;
+}
+
+#endif
+
+#if BUILD_TLS_MODULE == 2 /* BUILD_MODULE */
+
+#include "release.h"
+
+int RedisModule_OnLoad(void *ctx, RedisModuleString **argv, int argc) {
+    UNUSED(argv);
+    UNUSED(argc);
+
+    /* Connection modules must be part of the same build as redis. */
+    if (strcmp(REDIS_BUILD_ID_RAW, redisBuildIdRaw())) {
+        serverLog(LL_NOTICE, "Connection type %s was not built together with the redis-server used.", CONN_TYPE_TLS);
+        return REDISMODULE_ERR;
+    }
+
+    if (RedisModule_Init(ctx,"tls",1,REDISMODULE_APIVER_1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    /* Connection modules is available only bootup. */
+    if ((RedisModule_GetContextFlags(ctx) & REDISMODULE_CTX_FLAGS_SERVER_STARTUP) == 0) {
+        serverLog(LL_NOTICE, "Connection type %s can be loaded only during bootup", CONN_TYPE_TLS);
+        return REDISMODULE_ERR;
+    }
+
+    RedisModule_SetModuleOptions(ctx, REDISMODULE_OPTIONS_HANDLE_REPL_ASYNC_LOAD);
+
+    if(connTypeRegister(&CT_TLS) != C_OK)
+        return REDISMODULE_ERR;
+
+    return REDISMODULE_OK;
+}
+
+int RedisModule_OnUnload(void *arg) {
+    UNUSED(arg);
+    serverLog(LL_NOTICE, "Connection type %s can not be unloaded", CONN_TYPE_TLS);
+    return REDISMODULE_ERR;
+}
+#endif