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diff src/http/modules/ngx_http_ssl_module.c @ 7732:59e1c73fe02b

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SSL: ssl_reject_handshake directive (ticket #195). In some cases it might be needed to reject SSL handshake based on SNI server name provided, for example, to make sure an invalid certificate is not returned to clients trying to contact a name-based virtual server without SSL configured. Previously, a "ssl_ciphers aNULL;" was used for this. This workaround, however, is not compatible with TLSv1.3, in particular, when using BoringSSL, where it is not possible to configure TLSv1.3 ciphers at all. With this change, the ssl_reject_handshake directive is introduced, which instructs nginx to reject SSL handshakes with an "unrecognized_name" alert in a particular server block. For example, to reject handshake with names other than example.com, one can use the following configuration: server { listen 443 ssl; ssl_reject_handshake on; } server { listen 443 ssl; server_name example.com; ssl_certificate example.com.crt; ssl_certificate_key example.com.key; } The following configuration can be used to reject all SSL handshakes without SNI server name provided: server { listen 443 ssl; ssl_reject_handshake on; } server { listen 443 ssl; server_name ~^; ssl_certificate example.crt; ssl_certificate_key example.key; } Additionally, the ssl_reject_handshake directive makes configuring certificates for the default server block optional. If no certificates are configured in the default server for a given listening socket, certificates must be defined in all non-default server blocks with the listening socket in question.
author Maxim Dounin <mdounin@mdounin.ru>
date Thu, 22 Oct 2020 18:02:28 +0300
parents 3bff3f397c05
children 7ce28b4cc57e 71b7453fb11f
line wrap: on
line diff
--- a/src/http/modules/ngx_http_ssl_module.c
+++ b/src/http/modules/ngx_http_ssl_module.c
@@ -294,6 +294,13 @@ static ngx_command_t  ngx_http_ssl_comma
       offsetof(ngx_http_ssl_srv_conf_t, conf_commands),
       &ngx_http_ssl_conf_command_post },
 
+    { ngx_string("ssl_reject_handshake"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_flag_slot,
+      NGX_HTTP_SRV_CONF_OFFSET,
+      offsetof(ngx_http_ssl_srv_conf_t, reject_handshake),
+      NULL },
+
       ngx_null_command
 };
 
@@ -614,6 +621,7 @@ ngx_http_ssl_create_srv_conf(ngx_conf_t 
     sscf->enable = NGX_CONF_UNSET;
     sscf->prefer_server_ciphers = NGX_CONF_UNSET;
     sscf->early_data = NGX_CONF_UNSET;
+    sscf->reject_handshake = NGX_CONF_UNSET;
     sscf->buffer_size = NGX_CONF_UNSET_SIZE;
     sscf->verify = NGX_CONF_UNSET_UINT;
     sscf->verify_depth = NGX_CONF_UNSET_UINT;
@@ -660,6 +668,7 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *
                          prev->prefer_server_ciphers, 0);
 
     ngx_conf_merge_value(conf->early_data, prev->early_data, 0);
+    ngx_conf_merge_value(conf->reject_handshake, prev->reject_handshake, 0);
 
     ngx_conf_merge_bitmask_value(conf->protocols, prev->protocols,
                          (NGX_CONF_BITMASK_SET|NGX_SSL_TLSv1
@@ -707,7 +716,27 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *
 
     if (conf->enable) {
 
-        if (conf->certificates == NULL) {
+        if (conf->certificates) {
+            if (conf->certificate_keys == NULL) {
+                ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
+                              "no \"ssl_certificate_key\" is defined for "
+                              "the \"ssl\" directive in %s:%ui",
+                              conf->file, conf->line);
+                return NGX_CONF_ERROR;
+            }
+
+            if (conf->certificate_keys->nelts < conf->certificates->nelts) {
+                ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
+                              "no \"ssl_certificate_key\" is defined "
+                              "for certificate \"%V\" and "
+                              "the \"ssl\" directive in %s:%ui",
+                              ((ngx_str_t *) conf->certificates->elts)
+                              + conf->certificates->nelts - 1,
+                              conf->file, conf->line);
+                return NGX_CONF_ERROR;
+            }
+
+        } else if (!conf->reject_handshake) {
             ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                           "no \"ssl_certificate\" is defined for "
                           "the \"ssl\" directive in %s:%ui",
@@ -715,30 +744,7 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *
             return NGX_CONF_ERROR;
         }
 
-        if (conf->certificate_keys == NULL) {
-            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
-                          "no \"ssl_certificate_key\" is defined for "
-                          "the \"ssl\" directive in %s:%ui",
-                          conf->file, conf->line);
-            return NGX_CONF_ERROR;
-        }
-
-        if (conf->certificate_keys->nelts < conf->certificates->nelts) {
-            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
-                          "no \"ssl_certificate_key\" is defined "
-                          "for certificate \"%V\" and "
-                          "the \"ssl\" directive in %s:%ui",
-                          ((ngx_str_t *) conf->certificates->elts)
-                          + conf->certificates->nelts - 1,
-                          conf->file, conf->line);
-            return NGX_CONF_ERROR;
-        }
-
-    } else {
-
-        if (conf->certificates == NULL) {
-            return NGX_CONF_OK;
-        }
+    } else if (conf->certificates) {
 
         if (conf->certificate_keys == NULL
             || conf->certificate_keys->nelts < conf->certificates->nelts)
@@ -750,6 +756,9 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *
                           + conf->certificates->nelts - 1);
             return NGX_CONF_ERROR;
         }
+
+    } else if (!conf->reject_handshake) {
+        return NGX_CONF_OK;
     }
 
     if (ngx_ssl_create(&conf->ssl, conf->protocols, conf) != NGX_OK) {
@@ -808,7 +817,7 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *
         return NGX_CONF_ERROR;
 #endif
 
-    } else {
+    } else if (conf->certificates) {
 
         /* configure certificates */
 
@@ -947,6 +956,10 @@ ngx_http_ssl_compile_certificates(ngx_co
     ngx_http_complex_value_t          *cv;
     ngx_http_compile_complex_value_t   ccv;
 
+    if (conf->certificates == NULL) {
+        return NGX_OK;
+    }
+
     cert = conf->certificates->elts;
     key = conf->certificate_keys->elts;
     nelts = conf->certificates->nelts;
@@ -1327,7 +1340,33 @@ ngx_http_ssl_init(ngx_conf_t *cf)
             cscf = addr[a].default_server;
             sscf = cscf->ctx->srv_conf[ngx_http_ssl_module.ctx_index];
 
-            if (sscf->certificates == NULL) {
+            if (sscf->certificates) {
+                continue;
+            }
+
+            if (!sscf->reject_handshake) {
+                ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
+                              "no \"ssl_certificate\" is defined for "
+                              "the \"listen ... ssl\" directive in %s:%ui",
+                              cscf->file_name, cscf->line);
+                return NGX_ERROR;
+            }
+
+            /*
+             * if no certificates are defined in the default server,
+             * check all non-default server blocks
+             */
+
+            cscfp = addr[a].servers.elts;
+            for (s = 0; s < addr[a].servers.nelts; s++) {
+
+                cscf = cscfp[s];
+                sscf = cscf->ctx->srv_conf[ngx_http_ssl_module.ctx_index];
+
+                if (sscf->certificates || sscf->reject_handshake) {
+                    continue;
+                }
+
                 ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                               "no \"ssl_certificate\" is defined for "
                               "the \"listen ... ssl\" directive in %s:%ui",