[nginx] SSL: server name callback changed to return SSL_TLSEXT_ERR_OK.

[Maxim Dounin]

details:   https://hg.nginx.org/nginx/rev/7e8bcba6d039
branches:  
changeset: 7471:7e8bcba6d039
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Sun Mar 03 16:47:44 2019 +0300
description:
SSL: server name callback changed to return SSL_TLSEXT_ERR_OK.

OpenSSL 1.1.1 does not save server name to the session if server name
callback returns anything but SSL_TLSEXT_ERR_OK, thus breaking
the $ssl_server_name variable in resumed sessions.

Since $ssl_server_name can be used even if we've selected the default
server and there are no other servers, it looks like the only viable
solution is to always return SSL_TLSEXT_ERR_OK regardless of the actual
result.

To fix things in the stream module as well, added a dummy server name
callback which always returns SSL_TLSEXT_ERR_OK.

diffstat:

 src/http/ngx_http_request.c        |  12 ++++++------
 src/stream/ngx_stream_ssl_module.c |  19 +++++++++++++++++++
 2 files changed, 25 insertions(+), 6 deletions(-)

diffs (93 lines):

diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -866,13 +866,13 @@ ngx_http_ssl_servername(ngx_ssl_conn_t *
     servername = SSL_get_servername(ssl_conn, TLSEXT_NAMETYPE_host_name);
 
     if (servername == NULL) {
-        return SSL_TLSEXT_ERR_NOACK;
+        return SSL_TLSEXT_ERR_OK;
     }
 
     c = ngx_ssl_get_connection(ssl_conn);
 
     if (c->ssl->handshaked) {
-        return SSL_TLSEXT_ERR_NOACK;
+        return SSL_TLSEXT_ERR_OK;
     }
 
     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0,
@@ -881,13 +881,13 @@ ngx_http_ssl_servername(ngx_ssl_conn_t *
     host.len = ngx_strlen(servername);
 
     if (host.len == 0) {
-        return SSL_TLSEXT_ERR_NOACK;
+        return SSL_TLSEXT_ERR_OK;
     }
 
     host.data = (u_char *) servername;
 
     if (ngx_http_validate_host(&host, c->pool, 1) != NGX_OK) {
-        return SSL_TLSEXT_ERR_NOACK;
+        return SSL_TLSEXT_ERR_OK;
     }
 
     hc = c->data;
@@ -896,12 +896,12 @@ ngx_http_ssl_servername(ngx_ssl_conn_t *
                                      NULL, &cscf)
         != NGX_OK)
     {
-        return SSL_TLSEXT_ERR_NOACK;
+        return SSL_TLSEXT_ERR_OK;
     }
 
     hc->ssl_servername = ngx_palloc(c->pool, sizeof(ngx_str_t));
     if (hc->ssl_servername == NULL) {
-        return SSL_TLSEXT_ERR_NOACK;
+        return SSL_TLSEXT_ERR_OK;
     }
 
     *hc->ssl_servername = host;
diff --git a/src/stream/ngx_stream_ssl_module.c b/src/stream/ngx_stream_ssl_module.c
--- a/src/stream/ngx_stream_ssl_module.c
+++ b/src/stream/ngx_stream_ssl_module.c
@@ -22,6 +22,9 @@ static ngx_int_t ngx_stream_ssl_handler(
 static ngx_int_t ngx_stream_ssl_init_connection(ngx_ssl_t *ssl,
     ngx_connection_t *c);
 static void ngx_stream_ssl_handshake_handler(ngx_connection_t *c);
+#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
+int ngx_stream_ssl_servername(ngx_ssl_conn_t *ssl_conn, int *ad, void *arg);
+#endif
 #ifdef SSL_R_CERT_CB_ERROR
 static int ngx_stream_ssl_certificate(ngx_ssl_conn_t *ssl_conn, void *arg);
 #endif
@@ -414,6 +417,17 @@ ngx_stream_ssl_handshake_handler(ngx_con
 }
 
 
+#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
+
+int
+ngx_stream_ssl_servername(ngx_ssl_conn_t *ssl_conn, int *ad, void *arg)
+{
+    return SSL_TLSEXT_ERR_OK;
+}
+
+#endif
+
+
 #ifdef SSL_R_CERT_CB_ERROR
 
 int
@@ -682,6 +696,11 @@ ngx_stream_ssl_merge_conf(ngx_conf_t *cf
     cln->handler = ngx_ssl_cleanup_ctx;
     cln->data = &conf->ssl;
 
+#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
+    SSL_CTX_set_tlsext_servername_callback(conf->ssl.ctx,
+                                           ngx_stream_ssl_servername);
+#endif
+
     if (ngx_stream_ssl_compile_certificates(cf, conf) != NGX_OK) {
         return NGX_CONF_ERROR;
     }