[TLS] ignore empty "CipherString" in ssl-conf-cmd

e.g. ssl.openssl.ssl-conf-cmd = ("CipherString" => "")

src/mod_gnutls.c

@@ -3010,7 +3010,7 @@ mod_gnutls_ssl_conf_ciphersuites (server *srv, plugin_config_socket *s, buffer *
      *
      * XXX: not done: could make a list of ciphers with bitflag of attributes
      *      to make future combining easier */
-    if (cipherstring) {
+    if (!buffer_string_is_empty(cipherstring)) {
         const buffer *b = cipherstring;
         const char *e = b->ptr;
 

src/mod_mbedtls.c

@@ -3128,7 +3128,7 @@ mod_mbedtls_ssl_conf_ciphersuites (server *srv, plugin_config_socket *s, buffer
      *
      * XXX: not done: could make a list of ciphers with bitflag of attributes
      *      to make future combining easier */
-    if (cipherstring) {
+    if (!buffer_string_is_empty(cipherstring)) {
         const buffer *b = cipherstring;
         const char *e = b->ptr;
 

src/mod_nss.c

@@ -3444,7 +3444,7 @@ mod_nss_ssl_conf_ciphersuites (server *srv, plugin_config_socket *s, buffer *cip
                   "Ciphersuite support not implemented for %s",
                   ciphersuites->ptr);
 
-    if (!cipherstring)
+    if (buffer_string_is_empty(cipherstring))
         return 1; /* nothing to do */
 
     /*

src/mod_openssl.c

@@ -1882,6 +1882,8 @@ network_openssl_ssl_conf_cmd (server *srv, plugin_config_socket *s)
     if (NULL != ds) {
         buffer *cipher_string =
           array_get_buf_ptr(s->ssl_conf_cmd, CONST_STR_LEN("CipherString"));
+        if (buffer_string_is_empty(cipher_string))
+            buffer_append_string_len(cipher_string, CONST_STR_LEN("HIGH"));
         buffer_append_string_len(cipher_string,
                                  CONST_STR_LEN(":!aNULL:!eNULL:!EXP"));
     }
@@ -3660,7 +3662,7 @@ mod_openssl_ssl_conf_cmd (server *srv, plugin_config_socket *s)
             rc = -1;
     }
 
-    if (cipherstring) {
+    if (!buffer_string_is_empty(cipherstring)) {
         /* Disable support for low encryption ciphers */
         buffer_append_string_len(cipherstring,
                                  CONST_STR_LEN(":!aNULL:!eNULL:!EXP"));

src/mod_wolfssl.c

@@ -3347,7 +3347,7 @@ mod_openssl_ssl_conf_cmd (server *srv, plugin_config_socket *s)
         /* WolfSSL max ver is set at WolfSSL compile-time */
     }
 
-    if (cipherstring) {
+    if (!buffer_string_is_empty(cipherstring)) {
         /* Disable support for low encryption ciphers */
         buffer_append_string_len(cipherstring,
                                  CONST_STR_LEN(":!aNULL:!eNULL:!EXP"));