70 lines
2.6 KiB
Diff
70 lines
2.6 KiB
Diff
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From 13935cf9fdc3c8d8278c70716417d3b71c36140e Mon Sep 17 00:00:00 2001
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From: Sergey Kandaurov <pluknet@nginx.com>
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Date: Wed, 22 Jan 2025 18:55:44 +0400
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Subject: [PATCH] SNI: added restriction for TLSv1.3 cross-SNI session
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resumption.
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In OpenSSL, session resumption always happens in the default SSL context,
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prior to invoking the SNI callback. Further, unlike in TLSv1.2 and older
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protocols, SSL_get_servername() returns values received in the resumption
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handshake, which may be different from the value in the initial handshake.
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Notably, this makes the restriction added in b720f650b insufficient for
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sessions resumed with different SNI server name.
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Considering the example from b720f650b, previously, a client was able to
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request example.org by presenting a certificate for example.org, then to
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resume and request example.com.
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The fix is to reject handshakes resumed with a different server name, if
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verification of client certificates is enabled in a corresponding server
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configuration.
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---
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src/http/ngx_http_request.c | 27 +++++++++++++++++++++++++--
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1 files changed, 25 insertions(+), 2 deletions(-)
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diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
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index 3cca57cf5ee..9593b7fb506 100644
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--- a/src/http/ngx_http_request.c
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+++ b/src/http/ngx_http_request.c
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@@ -932,6 +932,31 @@ ngx_http_ssl_servername(ngx_ssl_conn_t *ssl_conn, int *ad, void *arg)
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goto done;
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}
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+ sscf = ngx_http_get_module_srv_conf(cscf->ctx, ngx_http_ssl_module);
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+
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+#if (defined TLS1_3_VERSION \
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+ && !defined LIBRESSL_VERSION_NUMBER && !defined OPENSSL_IS_BORINGSSL)
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+
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+ /*
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+ * SSL_SESSION_get0_hostname() is only available in OpenSSL 1.1.1+,
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+ * but servername being negotiated in every TLSv1.3 handshake
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+ * is only returned in OpenSSL 1.1.1+ as well
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+ */
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+
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+ if (sscf->verify) {
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+ const char *hostname;
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+
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+ hostname = SSL_SESSION_get0_hostname(SSL_get0_session(ssl_conn));
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+
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+ if (hostname != NULL && ngx_strcmp(hostname, servername) != 0) {
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+ c->ssl->handshake_rejected = 1;
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+ *ad = SSL_AD_ACCESS_DENIED;
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+ return SSL_TLSEXT_ERR_ALERT_FATAL;
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+ }
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+ }
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+
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+#endif
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+
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hc->ssl_servername = ngx_palloc(c->pool, sizeof(ngx_str_t));
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if (hc->ssl_servername == NULL) {
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goto error;
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@@ -945,8 +970,6 @@ ngx_http_ssl_servername(ngx_ssl_conn_t *ssl_conn, int *ad, void *arg)
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ngx_set_connection_log(c, clcf->error_log);
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- sscf = ngx_http_get_module_srv_conf(hc->conf_ctx, ngx_http_ssl_module);
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-
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c->ssl->buffer_size = sscf->buffer_size;
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if (sscf->ssl.ctx) {
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