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- From 5fbcf1a914507b4c73d83387fdc5e8f612d83558 Mon Sep 17 00:00:00 2001
- From: Willy Tarreau <w@1wt.eu>
- Date: Thu, 22 Dec 2016 21:58:38 +0100
- Subject: [PATCH 16/19] BUG/MEDIUM: ssl: for a handshake when server-side SNI
- changes
-
- Calling SSL_set_tlsext_host_name() on the current SSL ctx has no effect
- if the session is being resumed because the hostname is already stored
- in the session and is not advertised again in subsequent connections.
- It's visible when enabling SNI and health checks at the same time because
- checks do not send an SNI and regular traffic reuses the same connection,
- resulting in no SNI being sent.
-
- The only short-term solution is to reset the reused session when the
- SNI changes compared to the previous one. It can make the server-side
- performance suffer when SNIs are interleaved but it will work. A better
- long-term solution would be to keep a small cache of a few contexts for
- a few SNIs.
-
- Now with SSL_set_session(ctx, NULL) it works. This needs to be double-
- checked though. The man says that SSL_set_session() frees any previously
- existing context. Some people report a bit of breakage when calling
- SSL_set_session(NULL) on openssl 1.1.0a (freed session not reusable at
- all though it's not an issue for now).
-
- This needs to be backported to 1.7 and 1.6.
- (cherry picked from commit 119a4084bf88418bce74d8af686576e371700c20)
- ---
- src/ssl_sock.c | 15 +++++++++++++++
- 1 file changed, 15 insertions(+)
-
- diff --git a/src/ssl_sock.c b/src/ssl_sock.c
- index 55eaa28..77fb4b3 100644
- --- a/src/ssl_sock.c
- +++ b/src/ssl_sock.c
- @@ -4143,12 +4143,27 @@ char *ssl_sock_get_version(struct connection *conn)
- return (char *)SSL_get_version(conn->xprt_ctx);
- }
-
- +/* Sets advertised SNI for outgoing connections. Please set <hostname> to NULL
- + * to disable SNI.
- + */
- void ssl_sock_set_servername(struct connection *conn, const char *hostname)
- {
- #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
- + char *prev_name;
- +
- if (!ssl_sock_is_ssl(conn))
- return;
-
- + /* if the SNI changes, we must destroy the reusable context so that a
- + * new connection will present a new SNI. As an optimization we could
- + * later imagine having a small cache of ssl_ctx to hold a few SNI per
- + * server.
- + */
- + prev_name = (char *)SSL_get_servername(conn->xprt_ctx, TLSEXT_NAMETYPE_host_name);
- + if ((!prev_name && hostname) ||
- + (prev_name && (!hostname || strcmp(hostname, prev_name) != 0)))
- + SSL_set_session(conn->xprt_ctx, NULL);
- +
- SSL_set_tlsext_host_name(conn->xprt_ctx, hostname);
- #endif
- }
- --
- 2.10.2
-
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