From 0373fe5d98c1515640e74fa6f4d32fac1f1d3ab2 Mon Sep 17 00:00:00 2001 From: Sergey Kandaurov Date: Tue, 28 Jan 2025 00:53:15 +0400 Subject: SNI: using the ClientHello callback. The change introduces an SNI based virtual server selection during early ClientHello processing. The callback is available since OpenSSL 1.1.1; for older OpenSSL versions, the previous behaviour is kept. Using the ClientHello callback sets a reasonable processing order for the "server_name" TLS extension. Notably, session resumption decision now happens after applying server configuration chosen by SNI, useful with enabled verification of client certificates, which brings consistency with BoringSSL behaviour. The change supersedes and reverts a fix made in 46b9f5d38 for TLSv1.3 resumed sessions. In addition, since the callback is invoked prior to the protocol version negotiation, this makes it possible to set "ssl_protocols" on a per-virtual server basis. To keep the $ssl_server_name variable working with TLSv1.2 resumed sessions, as previously fixed in fd97b2a80, a limited server name callback is preserved in order to acknowledge the extension. Note that to allow third-party modules to properly chain the call to ngx_ssl_client_hello_callback(), the servername callback function is passed through exdata. --- src/http/modules/ngx_http_ssl_module.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'src/http/modules') diff --git a/src/http/modules/ngx_http_ssl_module.c b/src/http/modules/ngx_http_ssl_module.c index fbf4ab871..3778758e2 100644 --- a/src/http/modules/ngx_http_ssl_module.c +++ b/src/http/modules/ngx_http_ssl_module.c @@ -749,6 +749,10 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child) cln->data = &conf->ssl; #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME + { + static ngx_ssl_client_hello_arg cb = { ngx_http_ssl_servername }; + + ngx_ssl_set_client_hello_callback(conf->ssl.ctx, &cb); if (SSL_CTX_set_tlsext_servername_callback(conf->ssl.ctx, ngx_http_ssl_servername) @@ -759,7 +763,7 @@ ngx_http_ssl_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child) "dynamically to an OpenSSL library which has no tlsext support, " "therefore SNI is not available"); } - + } #endif #ifdef TLSEXT_TYPE_application_layer_protocol_negotiation -- cgit